2d Affine XY-Spin Model/4d Gauge Theory Duality and Deconfinement
Energy Technology Data Exchange (ETDEWEB)
Anber, Mohamed M.; Poppitz, Erich; /Toronto U.; Unsal, Mithat; /SLAC /Stanford U., Phys. Dept. /San Francisco State U.
2012-08-16
We introduce a duality between two-dimensional XY-spin models with symmetry-breaking perturbations and certain four-dimensional SU(2) and SU(2) = Z{sub 2} gauge theories, compactified on a small spatial circle R{sup 1,2} x S{sup 1}, and considered at temperatures near the deconfinement transition. In a Euclidean set up, the theory is defined on R{sup 2} x T{sup 2}. Similarly, thermal gauge theories of higher rank are dual to new families of 'affine' XY-spin models with perturbations. For rank two, these are related to models used to describe the melting of a 2d crystal with a triangular lattice. The connection is made through a multi-component electric-magnetic Coulomb gas representation for both systems. Perturbations in the spin system map to topological defects in the gauge theory, such as monopole-instantons or magnetic bions, and the vortices in the spin system map to the electrically charged W-bosons in field theory (or vice versa, depending on the duality frame). The duality permits one to use the two-dimensional technology of spin systems to study the thermal deconfinement and discrete chiral transitions in four-dimensional SU(N{sub c}) gauge theories with n{sub f} {ge} 1 adjoint Weyl fermions.
Palma, G
2009-01-01
The probability density function (PDF) of some global average quantity plays a fundamental role in critical and highly correlated systems. We explicitly compute this quantity as a function of the magnetization for the two dimensional XY model in its harmonic approximation. Numerical simulations and perturbative results have shown a Gumbel-like shape of the PDF, in spite of the fact that the average magnetization is not an extreme variable. Our analytical result allows to test both perturbative analytical expansions and also numerical computations performed previously. Perfect agreement is found for the first moments of the PDF. Also for large volume and in the high temperature limit the distribution becomes Gaussian, as it should be. In the low temperature regime its numerical evaluation is compatible with a Gumbel distribution.
Komura, Yukihiro
2014-01-01
We present sample CUDA programs for the GPU computing of the Swendsen-Wang multi-cluster spin flip algorithm. We deal with the classical spin models; the Ising model, the $q$-state Potts model, and the classical XY model. As for the lattice, both the 2D (square) lattice and the 3D (simple cubic) lattice are treated. We already reported the idea of the GPU implementation for 2D models [Comput. Phys. Commun. 183 (2012) 1155-1161]. We here explain the details of sample programs, and discuss the performance of the present GPU implementation for the 3D Ising and XY models. We also show the calculated results of the moment ratio for these models, and discuss phase transitions.
Correlation Inequalities for the Quantum XY Model
Benassi, Costanza; Lees, Benjamin; Ueltschi, Daniel
2016-09-01
We show the positivity or negativity of truncated correlation functions in the quantum XY model with spin 1/2 (at any temperature) and spin 1 (in the ground state). These Griffiths-Ginibre inequalities of the second kind generalise an earlier result of Gallavotti.
Return to equilibrium in the XY model
Energy Technology Data Exchange (ETDEWEB)
Hume, L.; Robinson, D.W.
1986-09-01
We prove that the locally perturbed XY model returns to equilibrium under the unperturbed evolution but the unperturbed model does not necessarily approach equilibrium under the perturbed evolution. In fact this latter property is false for perturbation by a local magnetization. The failure is directly attributable to the formation of bound states. If the perturbation is quadratic these problems are reduced to spectral analysis of the one-particle Hamiltonian. We demonstrate that the perturbed Hamiltonian has a finite set of eigenvalues of finite multiplicity together with some absolutely continuous spectrum. Eigenvalues can occur in the continuum if, and only if, the perturbation dislocates the system. Singular continuous spectrum cannot occur.
Lattice distortion in disordered antiferromagnetic XY models
Institute of Scientific and Technical Information of China (English)
Li Peng-Fei; Cao Hai-Jing
2012-01-01
The behavior of lattice distortion in spin 1/2 antiferromagnetic XY models with random magnetic modulation is investigated with the consideration of spin-phonon coupling in the adiabatic limit.It is found that lattice distortion relies on the strength of the random modulation.For strong or weak enough spin-phonon couplings,the average lattice distortion may decrease or increase as the random modulation is strengthened.This may be the result of competition between the random magnetic modulation and the spin-phonon coupling.
Institute of Scientific and Technical Information of China (English)
GE Rong-Chun; LI Chuan-Feng; GUO Guang-Can
2012-01-01
We investigate the dynamics of entanglement,quantum correlation and classical correlation for the one-dimensional XY model in a transverse magnetic field.With the initial state polarized along the z axis,we find that the first maximum of the classical correlation between the nearest neighbor sites peaks around the critical point for large anisotropy parameter.It may indicate the quantum phase transition.For all kinds of correlation,we find that their behaviors between the nearest neighbor sites are significantly different from those of the next-nearestneighbor sites.
Activated sludge model No. 2d, ASM2d
DEFF Research Database (Denmark)
Henze, M.
1999-01-01
The Activated Sludge Model No. 2d (ASM2d) presents a model for biological phosphorus removal with simultaneous nitrification-denitrification in activated sludge systems. ASM2d is based on ASM2 and is expanded to include the denitrifying activity of the phosphorus accumulating organisms (PAOs......). This extension of ASM2 allows for improved modeling of the processes, especially with respect to the dynamics of nitrate and phosphate. (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved....
Simulating the classical XY model with a laser network
Tamate, Shuhei; Marandi, Alireza; McMahon, Peter; Utsunomiya, Shoko
2016-01-01
Drawing fair samples from the Boltzmann distribution of a statistical model is a challenging task for modern digital computers. We propose a physical implementation of a Boltzmann sampler for the classical XY model by using a laser network. The XY spins are mapped onto the phases of multiple laser pulses in a fiber ring cavity and the steady-state distribution of phases naturally realizes the Boltzmann distribution of the corresponding XY model. We experimentally implement the laser network by using an actively mode-locked fiber laser with optical delay lines, and demonstrate Boltzmann sampling for a one-dimensional XY ring.
The XY Model Coupled to Two-Dimensional Quantum Gravity
Baillie, C F; 10.1016/0370-2693(92)91037-A
2009-01-01
We perform Monte Carlo simulations using the Wolff cluster algorithm of the XY model on both fixed and dynamical phi-cubed graphs (i.e. without and with coupling to two-dimensional quantum gravity). We compare the numerical results with the theoretical expectation that the phase transition remains of KT type when the XY model is coupled to gravity. We also examine whether the universality we discovered in our earlier work on various Potts models with the same value of the central charge, $c$, carries over to the XY model, which has $c=1$.
The XY model coupled to two-dimensional quantum gravity
Baillie, C. F.; Johnston, D. A.
1992-09-01
We perform Monte Carlo simulations using the Wolff cluster algorithm of the XY model on both fixed and dynamical phi-cubed graphs (i.e. without and with coupling to two-dimensional quantum gravity). We compare the numerical results with the theoretical expectation that the phase transition remains of KT type when the XY model is coupled to gravity. We also examine whether the universality we discovered in our earlier work on various Potts models with the same value of the central charge, c, carries over to the XY model, which has c=1.
Multipartite geometric entanglement in finite size XY model
Energy Technology Data Exchange (ETDEWEB)
Blasone, Massimo; Dell' Anno, Fabio; De Siena, Silvio; Giampaolo, Salvatore Marco; Illuminati, Fabrizio, E-mail: blasone@sa.infn.i [Dipartimento di Matematica e Informatica, Universita degli Studi di Salerno, Via Ponte don Melillo, I-84084 Fisciano (Italy)
2009-06-01
We investigate the behavior of the multipartite entanglement in the finite size XY model by means of the hierarchical geometric measure of entanglement. By selecting specific components of the hierarchy, we study both global entanglement and genuinely multipartite entanglement.
19-vertex version of the fully frustrated XY model
Knops, Yolanda M. M.; Nienhuis, Bernard; Knops, Hubert J. F.; Blöte, Henk W. J.
1994-07-01
We investigate a 19-vertex version of the two-dimensional fully frustrated XY (FFXY) model. We construct Yang-Baxter equations for this model and show that there is no solution. Therefore we have chosen a numerical approach based on the transfer matrix. The results show that a coupled XY Ising model is in the same universality class as the FFXY model. We find that the phase coupling over an Ising wall is irrelevant at criticality. This leads to a correction of earlier determinations of the dimension x*h,Is of the Ising disorder operator. We find x*h,Is=0.123(5) and a conformal anomaly c=1.55(5). These results are consistent with the hypothesis that the FFXY model behaves as a superposition of an Ising model and an XY model. However, the dimensions associated with the energy, xt=0.77(3), and with the XY magnetization xh,XY~=0.17, refute this hypothesis.
Probability-changing cluster algorithm for two-dimensional XY and clock models
Tomita, Yusuke; Okabe, Yutaka
2002-05-01
We extend the newly proposed probability-changing cluster (PCC) Monte Carlo algorithm to the study of systems with the vector order parameter. Wolff's idea of the embedded cluster formalism is used for assigning clusters. The Kosterlitz-Thouless (KT) transitions for the two-dimensional (2D) XY and q-state clock models are studied by using the PCC algorithm. Combined with the finite-size scaling analysis based on the KT form of the correlation length, ξ~exp(c/(T/TKT-1)), we determine the KT transition temperature and the decay exponent η as TKT=0.8933(6) and η=0.243(4) for the 2D XY model. We investigate two transitions of the KT type for the 2D q-state clock models with q=6,8,12 and confirm the prediction of η=4/q2 at T1, the low-temperature critical point between the ordered and XY-like phases, systematically.
DEFF Research Database (Denmark)
Burcharth, Hans F.; Andersen, Thomas Lykke; Jensen, Palle Meinert
This report present the results of 2D physical model tests (length scale 1:50) carried out in a waveflume at Dept. of Civil Engineering, Aalborg University (AAU).......This report present the results of 2D physical model tests (length scale 1:50) carried out in a waveflume at Dept. of Civil Engineering, Aalborg University (AAU)....
Graph spectral characterisation of the XY model on complex networks
Expert, Paul; Takaguchi, Taro; Lambiotte, Renaud
2016-01-01
There is recent evidence that the $XY$ spin model on complex networks can display three different macroscopic states in response to the topology of the network underpinning the interactions of the spins. In this work, we present a novel way to characterise the macroscopic states of the $XY$ spin model based on the spectral decomposition of time series using topological information about the underlying networks. We use three different classes of networks to generate time series of the spins for the three possible macroscopic states. We then use the temporal Graph Signal Transform technique to decompose the time series of the spins on the eigenbasis of the Laplacian. From this decomposition, we produce spatial power spectra, which summarise the activation of structural modes by the non-linear dynamics, and thus coherent patterns of activity of the spins. These signatures of the macroscopic states are independent of the underlying networks and can thus be used as universal signatures for the macroscopic states. ...
Energy Technology Data Exchange (ETDEWEB)
Ginsparg, P.
1991-01-01
These are introductory lectures for a general audience that give an overview of the subject of matrix models and their application to random surfaces, 2d gravity, and string theory. They are intentionally 1.5 years out of date.
Energy Technology Data Exchange (ETDEWEB)
Ginsparg, P.
1991-12-31
These are introductory lectures for a general audience that give an overview of the subject of matrix models and their application to random surfaces, 2d gravity, and string theory. They are intentionally 1.5 years out of date.
DEFF Research Database (Denmark)
Andersen, Thomas Lykke; Frigaard, Peter
This report present the results of 2D physical model tests carried out in the shallow wave flume at Dept. of Civil Engineering, Aalborg University (AAU), on behalf of Energy E2 A/S part of DONG Energy A/S, Denmark. The objective of the tests was: to investigate the combined influence of the pile...
Another solution of 2D Ising model
Vergeles, S. N.
2009-04-01
The partition function of the Ising model on a two-dimensional regular lattice is calculated by using the matrix representation of a Clifford algebra (the Dirac algebra), with number of generators equal to the number of lattice sites. It is shown that the partition function over all loops in a 2D lattice including self-intersecting ones is the trace of a polynomial in terms of Dirac matrices. The polynomial is an element of the rotation group in the spinor representation. Thus, the partition function is a function of a character on an orthogonal group of a high degree in the spinor representation.
An electric-field representation of the harmonic XY model
Faulkner, Michael F.; Bramwell, Steven T.; Holdsworth, Peter C. W.
2017-03-01
The two-dimensional harmonic XY (HXY) model is a spin model in which the classical spins interact via a piecewise parabolic potential. We argue that the HXY model should be regarded as the canonical classical lattice spin model of phase fluctuations in two-dimensional condensates, as it is the simplest model that guarantees the modular symmetry of the experimental systems. Here we formulate a lattice electric-field representation of the HXY model and contrast this with an analogous representation of the Villain model and the two-dimensional Coulomb gas with a purely rotational auxiliary field. We find that the HXY model is a spin-model analogue of a lattice electric-field model of the Coulomb gas with an auxiliary field, but with a temperature-dependent vacuum (electric) permittivity that encodes the coupling of the spin vortices to their background spin-wave medium. The spin vortices map to the Coulomb charges, while the spin-wave fluctuations correspond to auxiliary-field fluctuations. The coupling explains the striking differences in the high-temperature asymptotes of the specific heats of the HXY model and the Coulomb gas with an auxiliary field. Our results elucidate the propagation of effective long-range interactions throughout the HXY model (whose interactions are purely local) by the lattice electric fields. They also imply that global spin-twist excitations (topological-sector fluctuations) generated by local spin dynamics are ergodically excluded in the low-temperature phase. We discuss the relevance of these results to condensate physics.
Spin-dynamics simulations of the triangular antiferromagnetic XY model*
Nho, Kwangsik; Landau, D. P.
2003-03-01
Using Monte Carlo and spin-dynamics methods, we have studied the dynamic behavior of the classical, antiferromagnetic XY model on a triangular lattice. The temporal evolutions of spin configurations were obtained by solving numerically the coupled equations of motion for each spin using fourth-order Suzuki-Trotter decompositions of exponential operators. We calculated the dynamic structure factor S(q,w) for momentum q and frequency w. Below T_KT (Kosteritz-Thouless transition), both the in-plane (S^xx) and out-of-plane (S^zz) components exhibit very strong and sharp spin-wave peaks. Well above T_KT, S^xx and S^zz apparently display a central peak, and spin-wave signatures are still seen in S^zz. In addition, we also observed an almost dispersionless domain-wall peak at high w below Tc (Ising transition), where long-range order appears in the staggered chirality[1]. We found that our results demonstrate the consistency of the dynamic finite-size scaling theory for the characteristic frequency wm and S(q,w). *Supported by NSF [1] D.H. Lee, J.D. Joannopoulos, J.W. Negele, and D.P. Landau, Phys. Rev. Lett. 52, 433 (1984)
Spin-dynamics simulations of the antiferromagnetic triangular XY model*
Nho, Kwangsik; Landau, D. P.
2002-03-01
Using Monte Carlo and spin-dynamics methods, we have simulated the dynamic behavior of the classical, antiferromagnetic XY model on a triangular lattice. The temporal evolutions of spin configurations were obtained by solving numerically the coupled equations of motion for each spin using fourth-order Suzuki-Trotter decompositions of exponential operators. From space-and time-displaced spin-spin correlation functions and their space-time Fourier transforms we obtained the dynamic structure factor S(q,w) for momentum q and frequency w. Below T_c, where long-range order appears in the staggered chirality[1], S(q,w) exhibits very strong and sharp spin-wave peaks in the in-plane-component S^xx. We also observe two-spin-wave peaks at low w and an almost dispersionless domain-wall peak at high w. Above T_c, a weak spin-wave peak persists but the domain-wall peak disappears for all q. We have calculated the dispersion relation and the linewidth of the spin-wave peak in S^xx by fitting the line shape to simple Lorentzians. *Supported by NSF [1] D.H. Lee, J.D. Joannopoulos, J.W. Negele, and D.P. Landau, Phys. Rev. Lett. 52, 433 (1984)
Effects of staggered magnetic field on entanglement in the anisotropic XY model
Sun, Z; Li, Y Q; Sun, Zhe; Wang, XiaoGuang; Li, You-Quan
2004-01-01
We investigate effects of staggered magnetic field on thermal entanglement in the anisotropic XY model. The analytic results of entanglement for the two-site cases are obtained. For the general case of even sites, we show that when the anisotropic parameter is zero, the entanglement in the XY model with a staggered magnetic field is the same as that with a uniform magnetic field.
WFR-2D: an analytical model for PWAS-generated 2D ultrasonic guided wave propagation
Shen, Yanfeng; Giurgiutiu, Victor
2014-03-01
This paper presents WaveFormRevealer 2-D (WFR-2D), an analytical predictive tool for the simulation of 2-D ultrasonic guided wave propagation and interaction with damage. The design of structural health monitoring (SHM) systems and self-aware smart structures requires the exploration of a wide range of parameters to achieve best detection and quantification of certain types of damage. Such need for parameter exploration on sensor dimension, location, guided wave characteristics (mode type, frequency, wavelength, etc.) can be best satisfied with analytical models which are fast and efficient. The analytical model was constructed based on the exact 2-D Lamb wave solution using Bessel and Hankel functions. Damage effects were inserted in the model by considering the damage as a secondary wave source with complex-valued directivity scattering coefficients containing both amplitude and phase information from wave-damage interaction. The analytical procedure was coded with MATLAB, and a predictive simulation tool called WaveFormRevealer 2-D was developed. The wave-damage interaction coefficients (WDICs) were extracted from harmonic analysis of local finite element model (FEM) with artificial non-reflective boundaries (NRB). The WFR-2D analytical simulation results were compared and verified with full scale multiphysics finite element models and experiments with scanning laser vibrometer. First, Lamb wave propagation in a pristine aluminum plate was simulated with WFR-2D, compared with finite element results, and verified by experiments. Then, an inhomogeneity was machined into the plate to represent damage. Analytical modeling was carried out, and verified by finite element simulation and experiments. This paper finishes with conclusions and suggestions for future work.
Temperature dependence of universal fluctuations in the two-dimensional harmonic XY model.
Palma, G
2006-04-01
We compute exact analytical expressions for the skewness and kurtosis in the two-dimensional harmonic XY model. These quantities correspond to the third and fourth normalized moments of the probability density function (PDF) of the magnetization of the model. From their behavior, we conclude that they depend explicitly on the system temperature even in the thermodynamic limit, and hence the PDF itself must depend on it. Our results correct the hypothesis called universal fluctuations, they confirm and extend previous results which showed a T dependence of the PDF, including perturbative expansions within the XY model up to first order in temperature.
Symmetries and solvable models for evaporating 2D black holes
Cruz, J; Navarro-Salas, J; Talavera, C F
1997-01-01
We study the evaporation process of a 2D black hole in thermal equilibrium when the ingoing radiation is switched off suddenly. We also introduce global symmetries of generic 2D dilaton gravity models which generalize the extra symmetry of the CGHS model.
Bond diluted Ising model in 2D
Directory of Open Access Journals (Sweden)
Bouamrane Rachid
2013-03-01
Full Text Available The bond diluted Ising model is studied by Monte Carlo method. The simulation is carried out on a two dimensional square lattice with missing bonds and free boundary conditions. The aim of this work is to investigate the thermodynamical properties of this model for different disorder degree parameter σ. The critical temperature is determined from the Binder cumulant and is shown to decreases as the disorder parameter σ increases linearly.
DEFF Research Database (Denmark)
Burcharth, Hans F.; Meinert, Palle; Andersen, Thomas Lykke
the crown wall have been measured. The model has been subjected to irregular waves corresponding to typical conditions offshore from the intended prototype location. Characteristic situations have been video recorded. The stability of the toe has been investigated. The wave-generated forces on the caisson...... and the crown have been recorded. The maximum of horizontal wave force and the related tilting moment together with the pressure distribution are documented for waves in the range of design conditions. The parameters and results in the report are given in full-scale values, if nothing else is stated....
Cosmological model in 2d dilaton gravity
Mishima, T; Mishima, Takashi; Nakamichi, Akika
1993-01-01
We apply CGHS-type dilaton gravity model to (1+1)-dimensional cosmological situations. First the behavior of a compact 1-dimensional universe (i.e. like a closed string) is classified on the assumption of homogeneity of universe. Several interesting solutions are found, which include a Misner-type universe having closed time-like curves, and an asymptotically de Sitter universe first pointed out by Yoshimura. In the second half of this talk, we discuss the modification of the classical homogeneous solutions, considering inhomogeneity of classical conformal matters and also quantum back-reaction respectively. (An expanded version of the talk presented by T. Mishima at Yukawa Institute of Theoretical Physics workshop `Quantum Gravity' 24-27, November 1992.)
Kalman Filter for Generalized 2-D Roesser Models
Institute of Scientific and Technical Information of China (English)
SHENG Mei; ZOU Yun
2007-01-01
The design problem of the state filter for the generalized stochastic 2-D Roesser models, which appears when both the state and measurement are simultaneously subjected to the interference from white noise, is discussed. The wellknown Kalman filter design is extended to the generalized 2-D Roesser models. Based on the method of "scanning line by line", the filtering problem of generalized 2-D Roesser models with mode-energy reconstruction is solved. The formula of the optimal filtering, which minimizes the variance of the estimation error of the state vectors, is derived. The validity of the designed filter is verified by the calculation steps and the examples are introduced.
A study of the XY model by the Monte Carlo method
Suranyi, Peter; Harten, Paul
1987-01-01
The massively parallel processor is used to perform Monte Carlo simulations for the two dimensional XY model on lattices of sizes up to 128 x 128. A parallel random number generator was constructed, finite size effects were studied, and run times were compared with those on a CRAY X-MP supercomputer.
Approximating the XY model on a random graph with a q -state clock model
Lupo, Cosimo; Ricci-Tersenghi, Federico
2017-02-01
Numerical simulations of spin glass models with continuous variables set the problem of a reliable but efficient discretization of such variables. In particular, the main question is how fast physical observables computed in the discretized model converge toward the ones of the continuous model when the number of states of the discretized model increases. We answer this question for the XY model and its discretization, the q -state clock model, in the mean-field setting provided by random graphs. It is found that the convergence of physical observables is exponentially fast in the number q of states of the clock model, so allowing a very reliable approximation of the XY model by using a rather small number of states. Furthermore, such an exponential convergence is found to be independent from the disorder distribution used. Only at T =0 , the convergence is slightly slower (stretched exponential). Thanks to the analytical solution to the q -state clock model, we compute accurate phase diagrams in the temperature versus disorder strength plane. We find that, at zero temperature, spontaneous replica symmetry breaking takes place for any amount of disorder, even an infinitesimal one. We also study the one step of replica symmetry breaking (1RSB) solution in the low-temperature spin glass phase.
QSAR Models for P-450 (2D6) Substrate Activity
DEFF Research Database (Denmark)
Ringsted, Tine; Nikolov, Nikolai Georgiev; Jensen, Gunde Egeskov;
2009-01-01
activity relationship (QSAR) modelling systems. They cross validated (leave-groups-out) with concordances of 71%, 81% and 82%, respectively. Discrete organic European Inventory of Existing Commercial Chemical Substances (EINECS) chemicals were screened to predict an approximate percentage of CYP 2D6...... substrates. These chemicals are potentially present in the environment. The biological importance of the CYP 2D6 and the use of the software mentioned above were discussed....
Collins Model and Phase Diagram of 2D Ternary System
Institute of Scientific and Technical Information of China (English)
XIE Chuan-Mei; CHEN Li-Rong
2004-01-01
The Collins model is introduced into the two-dimensional (2D) alternative ternary system having the Lennard-Jones (L-J) potential. The Gibbs free energy of this ternary system is calculated, and according to thermodynamic theory, a group of equations that determine the solid-liquid diagram of ternary system are derived, some isothermal sectional diagrams of the 2D ternary system are obtained. The results are quite similar to the behavior of three-dimensional substances.
Directory of Open Access Journals (Sweden)
A. Sadeghi
2007-03-01
Full Text Available Using both mean field renormalization group (MFRG and Surface-Bulk MFRG (SBMFRG, we study the critical behavior of the classical Heisenberg and XY models on a simple cubic lattice. Critical temperatures as well as critical exponents, characteristic the universality classes of these two models were calculated, analytically for1, 2, 3 and 4 spin clusters. The results are in good agreement with higher accurate methods such as Monte Carlo and High- temperature series.
UPLAND EROSION MODELING WITH CASC2D-SED
Institute of Scientific and Technical Information of China (English)
Pierre JULIEN; Rosalía ROJAS
2002-01-01
Developed at Colorado State University, CASC2D-SED is a physically-based model simulating the hydrologic response of a watershed to a distributed rainfall field. The time-dependent processes include:precipitation, interception, infiltration, surface runoff and channel routing, upland erosion, transport and sedimentation. CASC2D-SED is applied to Goodwin Creek, Mississippi. The watershed covers 21 km2and has been extensively monitored both at the outlet and at several internal locations by the ARS-NSL at Oxford, MS. The model has been calibrated and validated using rainfall data from 16 meteorological stations, 6 stream gauging stations and 6 sediment gauging stations. Sediment erosion/deposition rates by size fraction are predicted both in space and time. Geovisualization, a powerful data exploration technique based on GIS technology, is used to analyze and display the dynamic output time series generated by the CASC2D-SED model.
Thermodynamics of the two-dimensional XY model from functional renormalization
Jakubczyk, Pawel
2016-01-01
We solve the nonperturbative renormalization-group flow equations for the two-dimensional XY model at the truncation level of the (complete) second-order derivative expansion. We compute the thermodynamic properties in the high-temperature phase and compare the non-universal features specific to the XY model with results from Monte Carlo simulations. In particular, we study the position and magnitude of the specific heat peak as a function of temperature. The obtained results compare well with Monte Carlo simulations. We additionally gauge the accuracy of simplified nonperturbative renormalization-group treatments relying on $\\phi^4$-type truncations. Our computation indicates that such an approximation is insufficient in the high-$T$ phase and a correct analysis of the specific heat profile requires account of an infinite number of interaction vertices.
A VARIATIONAL MODEL FOR 2-D MICROPOLAR BLOOD FLOW
Institute of Scientific and Technical Information of China (English)
He Ji-huan
2003-01-01
The micropolar fluid model is an essential generalization of the well-established Navier-Stokes model in the sense that it takes into account the microstructure of the fluid.This paper is devolted to establishing a variational principle for 2-D incompressible micropolar blood flow.
Classical XY model with conserved angular momentum is an archetypal non-Newtonian fluid.
Evans, R M L; Hall, Craig A; Simha, R Aditi; Welsh, Tom S
2015-04-03
We find that the classical one-dimensional XY model, with angular-momentum-conserving Langevin dynamics, mimics the non-Newtonian flow regimes characteristic of soft matter when subjected to counterrotating boundaries. An elaborate steady-state phase diagram has continuous and first-order transitions between states of uniform flow, shear-banding, solid-fluid coexistence and slip planes. Results of numerical studies and a concise mean-field constitutive relation offer a paradigm for diverse nonequilibrium complex fluids.
Monte Carlo Study of the Xy-Model on SIERPIŃSKI Carpet
Mitrović, Božidar; Przedborski, Michelle A.
2014-09-01
We have performed a Monte Carlo (MC) study of the classical XY-model on a Sierpiński carpet, which is a planar fractal structure with infinite order of ramification and fractal dimension 1.8928. We employed the Wolff cluster algorithm in our simulations and our results, in particular those for the susceptibility and the helicity modulus, indicate the absence of finite-temperature Berezinskii-Kosterlitz-Thouless (BKT) transition in this system.
Absence of phase transition in the XY-model on Menger sponge
Przedborski, M. A.; Mitrović, B.
2014-04-01
We have performed a Monte Carlo study of the classical XY-model on a Menger sponge with the Wolff cluster algorithm (U. Wolff, 1989). The Menger sponge is a fractal object with infinite order of ramification and fractal dimension D=log(20)/log(3)=2.7268. From the dependence of the helicity modulus on system size and on boundary conditions, we conclude that there is no phase transition in the system at any finite temperature.
DEVELOPMENT OF 2D HUMAN BODY MODELING USING THINNING ALGORITHM
Directory of Open Access Journals (Sweden)
K. Srinivasan
2010-11-01
Full Text Available Monitoring the behavior and activities of people in Video surveillance has gained more applications in Computer vision. This paper proposes a new approach to model the human body in 2D view for the activity analysis using Thinning algorithm. The first step of this work is Background subtraction which is achieved by the frame differencing algorithm. Thinning algorithm has been used to find the skeleton of the human body. After thinning, the thirteen feature points like terminating points, intersecting points, shoulder, elbow, and knee points have been extracted. Here, this research work attempts to represent the body model in three different ways such as Stick figure model, Patch model and Rectangle body model. The activities of humans have been analyzed with the help of 2D model for the pre-defined poses from the monocular video data. Finally, the time consumption and efficiency of our proposed algorithm have been evaluated.
DEFF Research Database (Denmark)
Andersen, Thomas Lykke; Brorsen, Michael
This report is an extension of the study presented in Lykke Andersen and Brorsen, 2006 and includes results from the irregular wave tests, where Lykke Andersen & Brorsen, 2006 focused on regular waves. The 2D physical model tests were carried out in the shallow wave flume at Dept. of Civil...
Critical properties of XY model on two-layer Villain-ferromagnetic lattice
Institute of Scientific and Technical Information of China (English)
Wang Yi; R. Quartu; Liu Xiao-Yan; Han Ru-Qi; Horiguchi Tsuyoshi
2004-01-01
We investigate phase transitions of the XY model on a two-layer square lattice which consists of a Villain plane(J) and a ferromagnetic plane (I), using Monte Carlo simulations and a histogram method. Depending on the values of interaction parameters (I, J), the system presents three phases: namely, a Kosterlitz-Thouless (KT) phase in which the two planes are critical for I predominant over J, a chiral phase in which the two planes have a chiral order for J predominant over I and a new phase in which only the Villain plane has a chiral order and the ferromagnetic plane is paramagnetic with a small value of chirality. We clarify the nature of phase transitions by using a finite size scaling method. We find three different kinds of transitions according to the values of (I, J): the KT transition, the Ising transition and an XY-Ising transition with v = 0.849(3). It turns out that the Ising or XY-Ising transition is associated with the disappearance of the chiral order in the Villain plane.
Instantons in 2D U(1) Higgs model and 2D CP(N-1) sigma models
Lian, Yaogang
2007-12-01
In this thesis I present the results of a study of the topological structures of 2D U(1) Higgs model and 2D CP N-1 sigma models. Both models have been studied using the overlap Dirac operator construction of topological charge density. The overlap operator provides a more incisive probe into the local topological structure of gauge field configurations than the traditional plaquette-based operator. In the 2D U(1) Higgs model, we show that classical instantons with finite sizes violate the negativity of topological charge correlator by giving a positive contribution to the correlator at non-zero separation. We argue that instantons in 2D U(1) Higgs model must be accompanied by large quantum fluctuations in order to solve this contradiction. In 2D CPN-1 sigma models, we observe the anomalous scaling behavior of the topological susceptibility chi t for N ≤ 3. The divergence of chi t in these models is traced to the presence of small instantons with a radius of order a (= lattice spacing), which are directly observed on the lattice. The observation of these small instantons provides detailed confirmation of Luscher's argument that such short-distance excitations, with quantized topological charge, should be the dominant topological fluctuations in CP1 and CP 2, leading to a divergent topological susceptibility in the continuum limit. For the CPN-1 models with N > 3 the topological susceptibility is observed to scale properly with the mass gap. Another topic presented in this thesis is an implementation of the Zolotarev optimal rational approximation for the overlap Dirac operator. This new implementation has reduced the time complexity of the overlap routine from O(N3 ) to O(N), where N is the total number of sites on the lattice. This opens up a door to more accurate lattice measurements in the future.
2D Models for Dust-driven AGB Star Winds
Woitke, P
2006-01-01
New axisymmetric (2D) models for dust-driven winds of C-stars are presented which include hydrodynamics with radiation pressure on dust, equilibrium chemistry and time-dependent dust formation with coupled grey Monte Carlo radiative transfer. Considering the most simple case without stellar pulsation (hydrostatic inner boundary condition) these models reveal a more complex picture of the dust formation and wind acceleration as compared to earlier published spherically symmetric (1D) models. The so-called exterior $\\kappa$-mechanism causes radial oscillations with short phases of active dust formation between longer phases without appreciable dust formation, just like in the 1D models. However, in 2D geometry, the oscillations can be out-of-phase at different places above the stellar atmosphere which result in the formation of dust arcs or smaller caps that only occupy a certain fraction of the total solid angle. These dust structures are accelerated outward by radiation pressure, expanding radially and tangen...
2-D Magnetohydrodynamic Modeling of A Pulsed Plasma Thruster
Thio, Y. C. Francis; Cassibry, J. T.; Wu, S. T.; Rodgers, Stephen L. (Technical Monitor)
2002-01-01
Experiments are being performed on the NASA Marshall Space Flight Center (MSFC) MK-1 pulsed plasma thruster. Data produced from the experiments provide an opportunity to further understand the plasma dynamics in these thrusters via detailed computational modeling. The detailed and accurate understanding of the plasma dynamics in these devices holds the key towards extending their capabilities in a number of applications, including their applications as high power (greater than 1 MW) thrusters, and their use for producing high-velocity, uniform plasma jets for experimental purposes. For this study, the 2-D MHD modeling code, MACH2, is used to provide detailed interpretation of the experimental data. At the same time, a 0-D physics model of the plasma initial phase is developed to guide our 2-D modeling studies.
DEFF Research Database (Denmark)
Andersen, Thomas Lykke; Brorsen, Michael
This report present the results of 2D physical model tests carried out in the shallow wave flume at Dept. of Civil Engineering, Aalborg University (AAU), Denmark. The starting point for the present report is the previously carried out run-up tests described in Lykke Andersen & Frigaard, 2006......-shaped access platforms on piles. The Model tests include mainly regular waves and a few irregular wave tests. These tests have been conducted at Aalborg University from 9. November, 2006 to 17. November, 2006....
Phase transitions and topology in 2+k XY mean-field models.
Angelani, L; Ruocco, G
2007-11-01
The thermodynamics and topology of mean-field models with 2+k body interaction terms (generalizing XY model) are derived. Focusing on two particular cases (2+4 and 2+6 body interaction terms), a comparison between thermodynamic (phase transition energy, thermodynamically forbidden energy regions) and topological (singularity and curvature of saddle entropy) properties is performed. We find that (i) a topological change is present at the phase transition energy; however, (ii) only one topological change occurs, also for those models exhibiting two phase transitions; (iii) the order of a phase transition is not completely signaled by the curvature of topological quantities.
Numerical modelling of spallation in 2D hydrodynamics codes
Maw, J. R.; Giles, A. R.
1996-05-01
A model for spallation based on the void growth model of Johnson has been implemented in 2D Lagrangian and Eulerian hydrocodes. The model has been extended to treat complete separation of material when voids coalesce and to describe the effects of elevated temperatures and melting. The capabilities of the model are illustrated by comparison with data from explosively generated spall experiments. Particular emphasis is placed on the prediction of multiple spall effects in weak, low melting point, materials such as lead. The correlation between the model predictions and observations on the strain rate dependence of spall strength is discussed.
A "Necklace" Model for Vesicles Simulations in 2D
Ismail, Mourad
2012-01-01
The aim of this paper is to propose a new numerical model to simulate 2D vesicles interacting with a newtonian fluid. The inextensible membrane is modeled by a chain of circular rigid particles which are maintained in cohesion by using two different type of forces. First, a spring force is imposed between neighboring particles in the chain. Second, in order to model the bending of the membrane, each triplet of successive particles is submitted to an angular force. Numerical simulations of vesicles in shear flow have been run using Finite Element Method and the FreeFem++[1] software. Exploring different ratios of inner and outer viscosities, we recover the well known "Tank-Treading" and "Tumbling" motions predicted by theory and experiments. Moreover, for the first time, 2D simulations of the "Vacillating-Breathing" regime predicted by theory in [2] and observed experimentally in [3] are done without special ingredient like for example thermal fluctuations used in [4].
Spin transport in the frustrated anisotropic three-dimensional XY model
Lima, L. S.
2016-12-01
We use the SU(3) Schwinger's boson theory to study the spin transport in the frustrated anisotropic three-dimensional XY model at T=0 with single ion anisotropy. We have investigated the behavior of the spin conductivity for this model that presents exchange interactions J1, J2 and J ‧ . We study the spin transport in the Bose-Einstein regime where we have that the tz bosons are condensed i.e. = = t . Our results show a metallic spin transport for ω > 0 and a superconductor spin transport in the limit of DC conductivity.
Discontinuity of the Spin-Wave Stiffness in the Two-Dimensional XY Model
Chayes, L.
Using a graphical representation based on the Wolff algorithm, the (classical) d-dimensional XY model and some related spin-systems are studied. It is proved that in d≡2, the predicted discontinuity in the spin-wave stiffness indeed occurs. Further, the critical properties of the spin-system are related to percolation properties of the graphical representation. In particular, a suitably defined notion of percolation in the graphical representation is proved to be the necessary and sufficient condition for positivity of the spontaneous magnetization.
Critical properties of XY model on two-dimensional layered magnetic films
Institute of Scientific and Technical Information of China (English)
Wang Yi; Liu Xiao-Yan; Sun Lei; Zhang Xing; Han Ru-Qi
2006-01-01
Using Monte Carlo simulations, we have investigated the classical XY model on triangular lattices of ultra-thin film structures with middle ferromagnetic layers sandwiched between two antiferromagnetic layers. The internal energy,the specific heat, the chirality and the chiral susceptibility are calculated in order to clarify phase transitions and critical phenomena. From the finite-size scaling analyses, the values of critical exponents are determined. In a range of interaction parameters, we find that the chirality steeply goes up as temperature increases in a temperature range;correspondingly the value of a critical exponent for this change is estimated.
Finite size scaling and first-order phase transition in a modified XY model
Sinha, Suman; Roy, Soumen Kumar
2010-02-01
Monte Carlo simulation has been performed in a two-dimensional modified XY -model first proposed by Domany [Phys. Rev. Lett. 52, 1535 (1984)] The cluster algorithm of Wolff has been used and multiple histogram reweighting is performed. The first-order scaling behavior of the quantities such as specific heat and free-energy barrier are found to be obeyed accurately. While the lowest-order correlation function was found to decay to zero at long distance just above the transition, the next-higher-order correlation function shows a nonzero plateau.
2-D Electromagnetic Model of Fast-Ramping Superconducting Magnets
Auchmann, B; Kurz, S; Russenschuck, Stephan
2006-01-01
Fast-ramping superconducting (SC) accelerator magnets are the subject of R&D efforts by magnet designers at various laboratories. They require modifications of magnet design tools such as the ROXIE program at CERN, i.e. models of dynamic effects in superconductors need to be implemented and validated. In this paper we present the efforts towards a dynamic 2-D simulation of fast-ramping SC magnets with the ROXIE tool. Models are introduced and simulation results are compared to measurements of the GSI001 magnet of a GSI test magnet constructed and measured at BNL.
DEFF Research Database (Denmark)
Andersen, Thomas Lykke; Frigaard, Peter
This report present the results of 2D physical model tests carried out in the shallow wave flume at Dept. of Civil Engineering, Aalborg University (AAU). The objective of the tests was: To investigate the combined influence of the pile diameter to water depth ratio and the wave height to water...... on the front side of the pile (0 to 90 degrees). These tests have been conducted at Aalborg University from 9. October, 2006 to 8. November, 2006. Unless otherwise mentioned, all values given in this report are in model scale....
Yang, Hong-Liu; Radons, Günter
2008-01-01
Crossover from weak to strong chaos in high-dimensional Hamiltonian systems at the strong stochasticity threshold (SST) was anticipated to indicate a global transition in the geometric structure of phase space. Our recent study of Fermi-Pasta-Ulam models showed that corresponding to this transition the energy density dependence of all Lyapunov exponents is identical apart from a scaling factor. The current investigation of the dynamic XY model discovers an alternative scenario for the energy dependence of the system dynamics at SSTs. Though similar in tendency, the Lyapunov exponents now show individually different energy dependencies except in the near-harmonic regime. Such a finding restricts the use of indices such as the largest Lyapunov exponent and the Ricci curvatures to characterize the global transition in the dynamics of high-dimensional Hamiltonian systems. These observations are consistent with our conjecture that the quasi-isotropy assumption works well only when parametric resonances are the dominant sources of dynamical instabilities. Moreover, numerical simulations demonstrate the existence of hydrodynamical Lyapunov modes (HLMs) in the dynamic XY model and show that corresponding to the crossover in the Lyapunov exponents there is also a smooth transition in the energy density dependence of significance measures of HLMs. In particular, our numerical results confirm that strong chaos is essential for the appearance of HLMs.
Critical behavior of the XY-rotor model on regular and small-world networks.
De Nigris, Sarah; Leoncini, Xavier
2013-07-01
We study the XY rotors model on small networks whose number of links scales with the system size N(links)~N(γ), where 1≤γ≤2. We first focus on regular one-dimensional rings in the microcanonical ensemble. For γ1.5, the system equilibrium properties are found to be identical to the mean field, which displays a second-order phase transition at a critical energy density ε=E/N,ε(c)=0.75. Moreover, for γ(c)~/=1.5 we find that a nontrivial state emerges, characterized by an infinite susceptibility. We then consider small-world networks, using the Watts-Strogatz mechanism on the regular networks parametrized by γ. We first analyze the topology and find that the small-world regime appears for rewiring probabilities which scale as p(SW)[proportionality]1/N(γ). Then considering the XY-rotors model on these networks, we find that a second-order phase transition occurs at a critical energy ε(c) which logarithmically depends on the topological parameters p and γ. We also define a critical probability p(MF), corresponding to the probability beyond which the mean field is quantitatively recovered, and we analyze its dependence on γ.
Brane Brick Models and 2d (0,2) Triality
Franco, Sebastian; Seong, Rak-Kyeong
2016-01-01
We provide a brane realization of 2d (0,2) Gadde-Gukov-Putrov triality in terms of brane brick models. These are Type IIA brane configurations that are T-dual to D1-branes over singular toric Calabi-Yau 4-folds. Triality translates into a local transformation of brane brick models, whose simplest representative is a cube move. We present explicit examples and construct their triality networks. We also argue that the classical mesonic moduli space of brane brick model theories, which corresponds to the probed Calabi-Yau 4-fold, is invariant under triality. Finally, we discuss triality in terms of phase boundaries, which play a central role in connecting Calabi-Yau 4-folds to brane brick models.
2D numerical modelling of meandering channel formation
Indian Academy of Sciences (India)
Y Xiao; G Zhou; F S Yang
2016-03-01
A 2D depth-averaged model for hydrodynamic sediment transport and river morphological adjustment was established. The sediment transport submodel takes into account the influence of non-uniform sediment with bed surface armoring and considers the impact of secondary flow in the direction of bed-loadtransport and transverse slope of the river bed. The bank erosion submodel incorporates a simple simulation method for updating bank geometry during either degradational or aggradational bed evolution. Comparison of the results obtained by the extended model with experimental and field data, and numericalpredictions validate that the proposed model can simulate grain sorting in river bends and duplicate the characteristics of meandering river and its development. The results illustrate that by using its control factors, the improved numerical model can be applied to simulate channel evolution under differentscenarios and improve understanding of patterning processes.
2-D Composite Model for Numerical Simulations of Nonlinear Waves
Institute of Scientific and Technical Information of China (English)
2000-01-01
－ A composite model, which is the combination of Boussinesq equations and Volume of Fluid (VOF) method, has been developed for 2-D time-domain computations of nonlinear waves in a large region. The whole computational region Ω is divided into two subregions. In the near-field around a structure, Ω2, the flow is governed by 2-D Reynolds Averaged Navier-Stokes equations with a turbulence closure model of k-ε equations and numerically solved by the improved VOF method; whereas in the subregion Ω1 (Ω1 = Ω - Ω2) the flow is governed by one-D Boussinesq equations and numerically solved with the predictor-corrector algorithm. The velocity and the wave surface elevation are matched on the common boundary of the two subregions. Numerical tests have been conducted for the case of wave propagation and interaction with a wave barrier. It is shown that the composite model can help perform efficient computation of nonlinear waves in a large region with the complicated flow fields near structures taken into account.
2D model for melt progression through rods and debris
Energy Technology Data Exchange (ETDEWEB)
Fichot, F. [IPSN/DRS, CEA Cadarache, St. Paul-lez-Durance (France)
2001-07-01
During the degradation of a nuclear core in a severe accident scenario, the high temperatures reached lead to the melting of materials. The formation of liquid mixtures at various elevations is followed by the flow of molten materials through the core. Liquid mixture may flow under several configurations: axial relocation along the rods, horizontal motion over a plane surface such as the core support plate or a blockage of material, 2D relocation through a debris bed, etc.. The two-dimensional relocation of molten material through a porous debris bed, implemented for the simulation of late degradation phases, has opened a new way to the elaboration of the relocation model for the flow of liquid mixture along the rods. It is based on a volume averaging method, where wall friction and capillary effects are taken into account by introducing effective coefficients to characterize the solid matrix (rods, grids, debris, etc.). A local description of the liquid flow is necessary to derive the effective coefficients. Heat transfers are modelled in a similar way. The derivation of the conservation equations for the liquid mixture falling flow (momentum) in two directions (axial and radial-horizontal) and for the heat exchanges (energy) are the main points of this new model for simulating melt progression. In this presentation, the full model for the relocation and solidification of liquid materials through a rod bundle or a debris bed is described. It is implemented in the ICARE/CATHARE code, developed by IPSN in Cadarache. The main improvements and advantages of the new model are: A single formulation for liquid mixture relocation, in 2D, either through a rod bundle or a porous debris bed, Extensions to complex structures (grids, by-pass, etc..), The modeling of relocation of a liquid mixture over plane surfaces. (author)
A stochastic model of cascades in 2D turbulence
Ditlevsen, Peter D
2012-01-01
The dual cascade of energy and enstrophy in 2D turbulence cannot easily be understood in terms of an analog to the Richardson-Kolmogorov scenario describing the energy cascade in 3D turbulence. The coherent up- and downscale fluxes points to non-locality of interactions in spectral space, and thus the specific spatial structure of the flow could be important. Shell models, which lack spacial structure and have only local interactions in spectral space, indeed fail in reproducing the correct scaling for the inverse cascade of energy. In order to exclude the possibility that non-locality of interactions in spectral space is crucial for the dual cascade, we introduce a stochastic spectral model of the cascades which is local in spectral space and which shows the correct scaling for both the direct enstrophy - and the inverse energy cascade.
2D Quantum Transport Modeling in Nanoscale MOSFETs
Svizhenko, Alexei; Anantram, M. P.; Govindan, T. R.; Biegel, Bryan
2001-01-01
With the onset of quantum confinement in the inversion layer in nanoscale MOSFETs, behavior of the resonant level inevitably determines all device characteristics. While most classical device simulators take quantization into account in some simplified manner, the important details of electrostatics are missing. Our work addresses this shortcoming and provides: (a) a framework to quantitatively explore device physics issues such as the source-drain and gate leakage currents, DIBL, and threshold voltage shift due to quantization, and b) a means of benchmarking quantum corrections to semiclassical models (such as density- gradient and quantum-corrected MEDICI). We have developed physical approximations and computer code capable of realistically simulating 2-D nanoscale transistors, using the non-equilibrium Green's function (NEGF) method. This is the most accurate full quantum model yet applied to 2-D device simulation. Open boundary conditions, oxide tunneling and phase-breaking scattering are treated on equal footing. Electrons in the ellipsoids of the conduction band are treated within the anisotropic effective mass approximation. Quantum simulations are focused on MIT 25, 50 and 90 nm "well- tempered" MOSFETs and compared to classical and quantum corrected models. The important feature of quantum model is smaller slope of Id-Vg curve and consequently higher threshold voltage. These results are quantitatively consistent with I D Schroedinger-Poisson calculations. The effect of gate length on gate-oxide leakage and sub-threshold current has been studied. The shorter gate length device has an order of magnitude smaller current at zero gate bias than the longer gate length device without a significant trade-off in on-current. This should be a device design consideration.
Generalization Technique for 2D+SCALE Dhe Data Model
Karim, Hairi; Rahman, Alias Abdul; Boguslawski, Pawel
2016-10-01
Different users or applications need different scale model especially in computer application such as game visualization and GIS modelling. Some issues has been raised on fulfilling GIS requirement of retaining the details while minimizing the redundancy of the scale datasets. Previous researchers suggested and attempted to add another dimension such as scale or/and time into a 3D model, but the implementation of scale dimension faces some problems due to the limitations and availability of data structures and data models. Nowadays, various data structures and data models have been proposed to support variety of applications and dimensionality but lack research works has been conducted in terms of supporting scale dimension. Generally, the Dual Half Edge (DHE) data structure was designed to work with any perfect 3D spatial object such as buildings. In this paper, we attempt to expand the capability of the DHE data structure toward integration with scale dimension. The description of the concept and implementation of generating 3D-scale (2D spatial + scale dimension) for the DHE data structure forms the major discussion of this paper. We strongly believed some advantages such as local modification and topological element (navigation, query and semantic information) in scale dimension could be used for the future 3D-scale applications.
2D scaled model of the TURBOPROP wing
Directory of Open Access Journals (Sweden)
Adrian DOBRE
2011-12-01
Full Text Available The 2D Turbo Prop wing is part of the European Clean Sky JTI GRA Low Noise programme. For this, the model is equipped with interchangeable T.E. noise reducing systems.The scope of the tests in the INCAS Subsonic wind tunnel is to investigate and compare the aerodynamic and aero acoustic performances of a series of different T.E. High Lift Devices noise reducing systems of the “Turbo Prop wing configuration”. For this, the distribution of the pressure at the surface of the model should be determined. The measurement of the pressure is classically made through orifices of small size connected to a common transducer via a tubing system and a scanning device. The aerodynamic forces and moments are obtained by integration of the pressure and shear stress distributions. The wing span of the model is equal to the width of the test section.Due to the large wing span B = 2500 mm and the testing speed V = 90 m/s, the aerodynamic forces and moments occurring on the model exceed more than two times the measuring capacity of the TEM external balance of the INCAS Subsonic wind tunnel. This imposes attaching the model to supports situated outside the wind tunnel.
The sudden Birth and sudden Death of thermal fidelity in a two-qubit XY model
Qin, Li-Guo; Jiang, Ying; Zhang, Hong-Biao
2011-01-01
We study the energy level crossings of the states and thermal fidelity for a two-qubit XY model in the presence of a transverse and inhomogeneous magnetic field. It is shown clearly the effects of the anisotropic factor of the magnetic field through the contour figures of energy level crossing in two subspaces, the isotropy subspace and anisotropy subspace. We calculate the quantum fidelity between the system and the ground state to which the results show the strong effect of the anisotropic factor again. In addition, making use of the transition of Yangian generators in the tensor product space, we study the evolution of the thermal fidelity after the transition. The potential applications of Yangian algebra, as a switch to turn on or off the fidelity, are proposed.
Subtlety in the Critical Behavior of the Two Dimensional XY Model
Kim, Jae-Kwon
1996-03-01
We study the two dimensional classical XY model using the single cluster Monte Carlo algorithm^1. We present extensive high -temperature -phase bulk data that are extracted based on a novel finite- size- scaling Monte Carlo technique^2. The largest value of the estimated bulk correlation length is 1390 in lattice units. Our data reveal that η=1/4 sets in near criticality. The standard finite-size-scaling analysis of the data close to criticality, however, seems to indicate that η=1/4 is compatible only for a critical temperature (T_c) over the range 0.900 Wolff, Phys. Rev. Lett. 62, 361 (1989) ^2 J.-K. Kim, Euro. Phys. Lett. 28, 211 (1994) Research supported in part by the NSF
2-D Chemical-Dynamical Modeling of Venus's Sulfur Variability
Bierson, Carver J.; Zhang, Xi
2016-10-01
Over the last decade a combination of ground based and Venus Express observations have been made of the concentration of sulfur species in Venus's atmosphere, both above [1, 2] and below the clouds [3, 4]. These observations put constraints on both the vertical and meridional variations of the major sulfur species in Venus's atmosphere.. It has also been observed that SO2 concentrations varies on both timescales of hours and years [1,4]. The spatial and temporal distribution of tracer species is owing to two possibilities: mutual chemical interaction and dynamical tracer transport.Previous Chemical modeling of Venus's middle atmosphere has only been explored in 1-D. We will present the first 2-D (altitude and latitude) chemical-dynamical model for Venus's middle atmosphere. The sulfur chemistry is based on of the 1D model of Zhang et al. 2012 [5]. We do model runs over multiple Venus decades testing two scenarios: first one with varying sulfur fluxes from below, and second with secular dynamical perturbations in the atmosphere [6]. By comparing to Venus Express and ground based observations, we put constraints on the dynamics of Venus's middle atmosphere.References: [1] Belyaev et al. Icarus 2012 [2] Marcq et al. Nature geoscience, 2013 [3] Marcq et al. JGR:Planets, 2008 [4] Arney et al. JGR:Planets, 2014 [5] Zhang et al. Icarus 2012 [6] Parish et al. Icarus 2012
2-D Model for Normal and Sickle Cell Blood Microcirculation
Tekleab, Yonatan; Harris, Wesley
2011-11-01
Sickle cell disease (SCD) is a genetic disorder that alters the red blood cell (RBC) structure and function such that hemoglobin (Hb) cannot effectively bind and release oxygen. Previous computational models have been designed to study the microcirculation for insight into blood disorders such as SCD. Our novel 2-D computational model represents a fast, time efficient method developed to analyze flow dynamics, O2 diffusion, and cell deformation in the microcirculation. The model uses a finite difference, Crank-Nicholson scheme to compute the flow and O2 concentration, and the level set computational method to advect the RBC membrane on a staggered grid. Several sets of initial and boundary conditions were tested. Simulation data indicate a few parameters to be significant in the perturbation of the blood flow and O2 concentration profiles. Specifically, the Hill coefficient, arterial O2 partial pressure, O2 partial pressure at 50% Hb saturation, and cell membrane stiffness are significant factors. Results were found to be consistent with those of Le Floch [2010] and Secomb [2006].
VAM2D: Variably saturated analysis model in two dimensions
Energy Technology Data Exchange (ETDEWEB)
Huyakorn, P.S.; Kool, J.B.; Wu, Y.S. (HydroGeoLogic, Inc., Herndon, VA (United States))
1991-10-01
This report documents a two-dimensional finite element model, VAM2D, developed to simulate water flow and solute transport in variably saturated porous media. Both flow and transport simulation can be handled concurrently or sequentially. The formulation of the governing equations and the numerical procedures used in the code are presented. The flow equation is approximated using the Galerkin finite element method. Nonlinear soil moisture characteristics and atmospheric boundary conditions (e.g., infiltration, evaporation and seepage face), are treated using Picard and Newton-Raphson iterations. Hysteresis effects and anisotropy in the unsaturated hydraulic conductivity can be taken into account if needed. The contaminant transport simulation can account for advection, hydrodynamic dispersion, linear equilibrium sorption, and first-order degradation. Transport of a single component or a multi-component decay chain can be handled. The transport equation is approximated using an upstream weighted residual method. Several test problems are presented to verify the code and demonstrate its utility. These problems range from simple one-dimensional to complex two-dimensional and axisymmetric problems. This document has been produced as a user's manual. It contains detailed information on the code structure along with instructions for input data preparation and sample input and printed output for selected test problems. Also included are instructions for job set up and restarting procedures. 44 refs., 54 figs., 24 tabs.
Žukovič, Milan
2016-07-01
Ground-state phases of a generalized XY model with magnetic and generalized nematic couplings on a nonbipartite triangular lattice are investigated in the exchange interactions parameter space. We demonstrate that the model displays a number of ordered and quasiordered phases as a result of geometrical frustration and/or competition between the magnetic and the generalized nematic interactions. The nature and the extent of the respective phases depend on the parameter q that characterizes the higher-order harmonics term in the Hamiltonian. Motivated by a recent discovery of the experimental realization of the model with q =2 in a seemingly unrelated field of the system chemistry [A. B. Cairns, M. J. Cliffe, J. A. M. Paddison, D. Daisenberger, M. G. Tucker, F.-X. Coudert, and A. L. Goodwin, Nature Chemistry 8, 442 (2016), 10.1038/nchem.2462], the model with q ≥2 is discussed in the context of the prediction of structural phases of a class of bimetallic cyanides based on a mapping between the two systems.
High-temperature series analyses of the classical Heisenberg and XY model
Adler, J; Janke, W
1993-01-01
Although there is now a good measure of agreement between Monte Carlo and high-temperature series expansion estimates for Ising ($n=1$) models, published results for the critical temperature from series expansions up to 12{\\em th} order for the three-dimensional classical Heisenberg ($n=3$) and XY ($n=2$) model do not agree very well with recent high-precision Monte Carlo estimates. In order to clarify this discrepancy we have analyzed extended high-temperature series expansions of the susceptibility, the second correlation moment, and the second field derivative of the susceptibility, which have been derived a few years ago by L\\"uscher and Weisz for general $O(n)$ vector spin models on $D$-dimensional hypercubic lattices up to 14{\\em th} order in $K \\equiv J/k_B T$. By analyzing these series expansions in three dimensions with two different methods that allow for confluent correction terms, we obtain good agreement with the standard field theory exponent estimates and with the critical temperature estimates...
Phase diagram and correlation functions of the two-dimensional dissipative quantum XY model
Hou, Changtao; Varma, Chandra M.
2016-11-01
The two-dimensional quantum XY model, with a Caldeira-Leggett form of dissipation, is applicable to the quantum-critical properties of diverse experimental systems, ranging from superconductor to insulator transitions, ferromagnetic and antiferromagnetic transitions in metals, to the loop-current order transition in cuprates. We solve the reexpression of this model in terms of orthogonal topological excitations, vortices, and a variety of instantons, by renormalization group methods. The calculations explain the extraordinary properties of the model discovered in Monte Carlo calculations: the product form of the quantum-critical fluctuations in space and time, a spatial correlation length proportional to the logarithm of the temporal correlation length near the transition from a disordered to a fully ordered state, and the occurrence of a phase with spatial order without temporal order. They are intimately related to the flow of the metric of time in relation to the metric of space, i.e., of the dynamical critical exponent z . These properties appear to be essential in understanding the strange metallic phase found in a variety of quantum-critical transitions as well as the accompanying high-temperature superconductivity.
Super-rough glassy phase of the random field XY model in two dimensions.
Perret, Anthony; Ristivojevic, Zoran; Le Doussal, Pierre; Schehr, Grégory; Wiese, Kay J
2012-10-12
We study both analytically, using the renormalization group (RG) to two loop order, and numerically, using an exact polynomial algorithm, the disorder-induced glass phase of the two-dimensional XY model with quenched random symmetry-breaking fields and without vortices. In the super-rough glassy phase, i.e., below the critical temperature T(c), the disorder and thermally averaged correlation function B(r) of the phase field θ(x), B(r)=([θ(x)-θ(x+r)](2)) behaves, for r > a, as B(r) is approximately equal to A(τ)ln(2)(r/a) where r=|r| and a is a microscopic length scale. We derive the RG equations up to cubic order in τ=(T(c)-T)/T(c) and predict the universal amplitude A(τ)=2τ(2)-2τ(3)+O(τ(4)). The universality of A(τ) results from nontrivial cancellations between nonuniversal constants of RG equations. Using an exact polynomial algorithm on an equivalent dimer version of the model we compute A(τ) numerically and obtain a remarkable agreement with our analytical prediction, up to τ≈0.5.
Maximizing entropy of image models for 2-D constrained coding
DEFF Research Database (Denmark)
Forchhammer, Søren; Danieli, Matteo; Burini, Nino;
2010-01-01
£ 2 squares contains all 0s or all 1s. The maximum values of the entropy for the constraints are estimated and binary PRF satisfying the constraint are characterized and optimized w.r.t. the entropy. The maximum binary PRF entropy is 0.839 bits/symbol for the no uniform squares constraint. The entropy...... of the Markov random field defined by the 2-D constraint is estimated to be (upper bounded by) 0.8570 bits/symbol using the iterative technique of Belief Propagation on 2 £ 2 finite lattices. Based on combinatorial bounding techniques the maximum entropy for the constraint was determined to be 0.848.......This paper considers estimating and maximizing the entropy of two-dimensional (2-D) fields with application to 2-D constrained coding. We consider Markov random fields (MRF), which have a non-causal description, and the special case of Pickard random fields (PRF). The PRF are 2-D causal finite...
Truncating an exact matrix product state for the XY model: Transfer matrix and its renormalization
Rams, Marek M.; Zauner, Valentin; Bal, Matthias; Haegeman, Jutho; Verstraete, Frank
2015-12-01
We discuss how to analytically obtain an essentially infinite matrix product state (MPS) representation of the ground state of the XY model. On one hand this allows us to illustrate how the Ornstein-Zernike form of the correlation function emerges in the exact case using standard MPS language. On the other hand we study the consequences of truncating the bond dimension of the exact MPS, which is also part of many tensor network algorithms, and analyze how the truncated MPS transfer matrix is representing the dominant part of the exact quantum transfer matrix. In the gapped phase we observe that the correlation length obtained from a truncated MPS approaches the exact value following a power law in effective bond dimension. In the gapless phase we find a good match between a state obtained numerically from standard MPS techniques with finite bond dimension and a state obtained by effective finite imaginary time evolution in our framework. This provides a direct hint for a geometric interpretation of finite entanglement scaling at the critical point in this case. Finally, by analyzing the spectra of transfer matrices, we support the interpretation put forward by V. Zauner et al. [New J. Phys. 17, 053002 (2015), 10.1088/1367-2630/17/5/053002] that the MPS transfer matrix emerges from the quantum transfer matrix though the application of Wilson's numerical renormalization group along the imaginary-time direction.
A 2D simulation model for urban flood management
Price, Roland; van der Wielen, Jonathan; Velickov, Slavco; Galvao, Diogo
2014-05-01
The European Floods Directive, which came into force on 26 November 2007, requires member states to assess all their water courses and coast lines for risk of flooding, to map flood extents and assets and humans at risk, and to take adequate and coordinated measures to reduce the flood risk in consultation with the public. Flood Risk Management Plans are to be in place by 2015. There are a number of reasons for the promotion of this Directive, not least because there has been much urban and other infrastructural development in flood plains, which puts many at risk of flooding along with vital societal assets. In addition there is growing awareness that the changing climate appears to be inducing more frequent extremes of rainfall with a consequent increases in the frequency of flooding. Thirdly, the growing urban populations in Europe, and especially in the developing countries, means that more people are being put at risk from a greater frequency of urban flooding in particular. There are urgent needs therefore to assess flood risk accurately and consistently, to reduce this risk where it is important to do so or where the benefit is greater than the damage cost, to improve flood forecasting and warning, to provide where necessary (and possible) flood insurance cover, and to involve all stakeholders in decision making affecting flood protection and flood risk management plans. Key data for assessing risk are water levels achieved or forecasted during a flood. Such levels should of course be monitored, but they also need to be predicted, whether for design or simulation. A 2D simulation model (PriceXD) solving the shallow water wave equations is presented specifically for determining flood risk, assessing flood defense schemes and generating flood forecasts and warnings. The simulation model is required to have a number of important properties: -Solve the full shallow water wave equations using a range of possible solutions; -Automatically adjust the time step and
Brownian regime of finite-N corrections to particle motion in the XY hamiltonian mean field model
Ribeiro, Bruno V; Elskens, Yves
2016-01-01
We study the dynamics of the N-particle system evolving in the XY hamiltonian mean field (HMF) model for a repulsive potential, when no phase transition occurs. Starting from a homogeneous distribution, particles evolve in a mean field created by the interaction with all others. This interaction does not change the homogeneous state of the system, and particle motion is approximately ballistic with small corrections. For initial particle data approaching a waterbag, it is explicitly proved that corrections to the ballistic velocities are in the form of independent brownian noises over a time scale diverging not slower than $N^{2/5}$ as $N \\to \\infty$, which proves the propagation of molecular chaos. Molecular dynamics simulations of the XY-HMF model confirm our analytical findings.
Brownian regime of finite-N corrections to particle motion in the XY Hamiltonian mean field model
Ribeiro, Bruno V.; Amato, Marco A.; Elskens, Yves
2016-08-01
We study the dynamics of the N-particle system evolving in the XY Hamiltonian mean field (HMF) model for a repulsive potential, when no phase transition occurs. Starting from a homogeneous distribution, particles evolve in a mean field created by the interaction with all others. This interaction does not change the homogeneous state of the system, and particle motion is approximately ballistic with small corrections. For initial particle data approaching a waterbag, it is explicitly proved that corrections to the ballistic velocities are in the form of independent Brownian noises over a time scale diverging not slower than {N}2/5 as N\\to ∞ , which proves the propagation of molecular chaos. Molecular dynamics simulations of the XY-HMF model confirm our analytical findings.
The Implementation of C-ID, R2D2 Model on Learning Reading Comprehension
Rayanto, Yudi Hari; Rusmawan, Putu Ngurah
2016-01-01
The purposes of this research are to find out, (1) whether C-ID, R2D2 model is effective to be implemented on learning Reading comprehension, (2) college students' activity during the implementation of C-ID, R2D2 model on learning Reading comprehension, and 3) college students' learning achievement during the implementation of C-ID, R2D2 model on…
Chae, Dongho; Constantin, Peter; Wu, Jiahong
2014-09-01
We give an example of a well posed, finite energy, 2D incompressible active scalar equation with the same scaling as the surface quasi-geostrophic equation and prove that it can produce finite time singularities. In spite of its simplicity, this seems to be the first such example. Further, we construct explicit solutions of the 2D Boussinesq equations whose gradients grow exponentially in time for all time. In addition, we introduce a variant of the 2D Boussinesq equations which is perhaps a more faithful companion of the 3D axisymmetric Euler equations than the usual 2D Boussinesq equations.
Completeness of the classical 2D Ising model and universal quantum computation.
Van den Nest, M; Dür, W; Briegel, H J
2008-03-21
We prove that the 2D Ising model is complete in the sense that the partition function of any classical q-state spin model (on an arbitrary graph) can be expressed as a special instance of the partition function of a 2D Ising model with complex inhomogeneous couplings and external fields. In the case where the original model is an Ising or Potts-type model, we find that the corresponding 2D square lattice requires only polynomially more spins with respect to the original one, and we give a constructive method to map such models to the 2D Ising model. For more general models the overhead in system size may be exponential. The results are established by connecting classical spin models with measurement-based quantum computation and invoking the universality of the 2D cluster states.
Models of Late-Type Disk Galaxies: 1-D Versus 2-D
Mineikis, Tadas
2015-01-01
We investigate the effects of stochasticity on the observed galaxy parameters by comparing our stochastic star formation two-dimensional (2-D) galaxy evolution models with the commonly used one-dimensional (1-D) models with smooth star formation. The 2-D stochastic models predict high variability of the star formation rate and the surface photometric parameters across the galactic disks and in time.
Influence of Non-Uniform Magnetic Field on Quantum Teleportation in Heisenberg XY Model
Institute of Scientific and Technical Information of China (English)
SHAO Bin; YANG Tie-jian; ZHAO Yue-hong; ZOU Jian
2007-01-01
By considering the intrinsic decoherence, the validity of quantum teleportation of a two-qubit 1D Heisenberg XY chain in a non-uniform external magnetic field is studied. The fidelity as the measurement of a possible quantum teleportation is calculated and the effects of the non-uniform magnetic field and the intrinsic decoherence are discussed. It is found that anti-parallel magnetic field is more favorable for teleportation and the fidelity is suppressed by the intrinsic decoherence.
2D Poisson sigma models with gauged vectorial supersymmetry
2015-01-01
In this note, we gauge the rigid vectorial supersymmetry of the two-dimensional Poisson sigma model presented in arXiv:1503.05625. We show that the consistency of the construction does not impose any further constraints on the differential Poisson algebra geometry than those required for the ungauged model. We conclude by proposing that the gauged model provides a first-quantized framework for higher spin gravity.
2D Poisson Sigma Models with Gauged Vectorial Supersymmetry
Bonezzi, Roberto; Torres-Gomez, Alexander
2015-01-01
In this note, we gauge the rigid vectorial supersymmetry of the two-dimensional Poisson sigma model presented in arXiv:1503.05625. We show that the consistency of the construction does not impose any further constraints on the differential Poisson algebra geometry than those required for the ungauged model. We conclude by proposing that the gauged model provides a first-quantized framework for higher spin gravity.
2D Poisson sigma models with gauged vectorial supersymmetry
Bonezzi, Roberto; Sundell, Per; Torres-Gomez, Alexander
2015-08-01
In this note, we gauge the rigid vectorial supersymmetry of the two-dimensional Poisson sigma model presented in arXiv:1503.05625. We show that the consistency of the construction does not impose any further constraints on the differential Poisson algebra geometry than those required for the ungauged model. We conclude by proposing that the gauged model provides a first-quantized framework for higher spin gravity.
2-D Model Test Study of the Suape Breakwater, Brazil
DEFF Research Database (Denmark)
Andersen, Thomas Lykke; Burcharth, Hans F.; Sopavicius, A.;
This report deals with a two-dimensional model test study of the extension of the breakwater in Suape, Brazil. One cross-section was tested for stability and overtopping in various sea conditions. The length scale used for the model tests was 1:35. Unless otherwise specified all values given...
2D sigma models and differential Poisson algebras
Arias, Cesar; Boulanger, Nicolas; Sundell, Per; Torres-Gomez, Alexander
2015-08-01
We construct a two-dimensional topological sigma model whose target space is endowed with a Poisson algebra for differential forms. The model consists of an equal number of bosonic and fermionic fields of worldsheet form degrees zero and one. The action is built using exterior products and derivatives, without any reference to a worldsheet metric, and is of the covariant Hamiltonian form. The equations of motion define a universally Cartan integrable system. In addition to gauge symmetries, the model has one rigid nilpotent supersymmetry corresponding to the target space de Rham operator. The rigid and local symmetries of the action, respectively, are equivalent to the Poisson bracket being compatible with the de Rham operator and obeying graded Jacobi identities. We propose that perturbative quantization of the model yields a covariantized differential star product algebra of Kontsevich type. We comment on the resemblance to the topological A model.
2D sigma models and differential Poisson algebras
Arias, Cesar; Sundell, Per; Torres-Gomez, Alexander
2015-01-01
We construct a two-dimensional topological sigma model whose target space is endowed with a Poisson algebra for differential forms. The model consists of an equal number of bosonic and fermionic fields of worldsheet form degrees zero and one. The action is built using exterior products and derivatives, without any reference to any worldsheet metric, and is of the covariant Hamiltonian form. The equations of motion define a universally Cartan integrable system. In addition to gauge symmetries, the model has one rigid nilpotent supersymmetry corresponding to the target space de Rham operator. The rigid and local symmetries of the action, respectively, are equivalent to the Poisson bracket being compatible with the de Rham operator and obeying graded Jacobi identities. We propose that perturbative quantization of the model yields a covariantized differential star product algebra of Kontsevich type. We comment on the resemblance to the topological A model.
2D - Finite element model of a CIGS module
Energy Technology Data Exchange (ETDEWEB)
Janssen, G.J.M.; Slooff, L.H.; Bende, E.E. [ECN Solar Energy, Petten (Netherlands)
2012-09-15
The performance of thin-film CIGS modules is often limited due to inhomogeneities in CIGS layers. A 2-dimensional Finite Element Model for CIGS modules is demonstrated that predicts the impact of such inhomogeneities on the module performance. Results are presented of a module with a region of poor diode characteristics. It is concluded that according to this model the effects of poor diodes depend strongly on their location in the module and on their dispersion over the module surface. Due to its generic character the model can also be applied to other series connections of photovoltaic cells.
2D Ising Model with a Defect Line
Cabra, D C
1994-01-01
We study the two-dimensional Ising model with a defect line and evaluate multipoint energy correlation functions using non-perturbative field-theoretical methods. We also discuss the evaluation of the two spin correlator on the defect line.
Vibration induced flow in hoppers: DEM 2D polygon model
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
A two-dimensional discrete element model (DEM) simulation of cohesive polygonal particles has been developed to assess the benefit of point source vibration to induce flow in wedge-shaped hoppers. The particle-particle interaction model used is based on a multi-contact principle.The first part of the study investigated particle discharge under gravity without vibration to determine the critical orifice size (Be) to just sustain flow as a function of particle shape. It is shown that polygonal-shaped particles need a larger orifice than circular particles. It is also shown that Be decreases as the number of particle vertices increases. Addition of circular particles promotes flow of polygons in a linear manner.The second part of the study showed that vibration could enhance flow, effectively reducing Be. The model demonstrated the importance of vibrator location (height), consistent with previous continuum model results, and vibration amplitude in enhancing flow.
Quasicomplex N=2, d=1 Supersymmetric Sigma Models
Directory of Open Access Journals (Sweden)
Evgeny A. Ivanov
2013-11-01
Full Text Available We derive and discuss a new type of N=2 supersymmetric quantum mechanical sigma models which appear when the superfield action of the (1,2,1 multiplets is modified by adding an imaginary antisymmetric tensor to the target space metric, thus completing the latter to a non-symmetric Hermitian metric. These models are not equivalent to the standard de Rham sigma models, but are related to them through a certain special similarity transformation of the supercharges. On the other hand, they can be obtained by a Hamiltonian reduction from the complex supersymmetric N=2 sigma models built on the multiplets (2,2,0 and describing the Dolbeault complex on the manifolds with proper isometries. We study in detail the extremal two-dimensional case, when the target space metric is defined solely by the antisymmetric tensor, and show that the corresponding quantum systems reveal a hidden N=4 supersymmetry.
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.
Simulations of Quantum Spin Models on 2D Frustrated Lattices
Melko, Roger
2006-03-01
Algorithmic advances in quantum Monte Carlo techniques have opened up the possibility of studying models in the general class of the S=1/2 XXZ model (equivalent to hard-core bosons) on frustrated lattices. With an antiferromagnetic diagonal interaction (Jz), these models can be solved exactly with QMC, albeit with some effort required to retain ergodicity in the near-degenerate manifold of states that exists for large Jz. The application of the quantum (ferromagnetic off-diagonal) interaction to this classically degenerate manifold produces a variety of intriguing physics, including an order-by-disorder supersolid phase, novel insulating states, and possible exotic quantum critical phenomena. We discuss numerical results for the triangular and kagome lattices with nearest and next-nearest neighbor exchange interactions, and focus on the relevance of the simulations to related areas of physics, such as experiments of cold trapped atomic gasses and the recent theory of deconfined quantum criticality.
Coupled 1D-2D hydrodynamic inundation model for sewer overflow: Influence of modeling parameters
Directory of Open Access Journals (Sweden)
Adeniyi Ganiyu Adeogun
2015-10-01
Full Text Available This paper presents outcome of our investigation on the influence of modeling parameters on 1D-2D hydrodynamic inundation model for sewer overflow, developed through coupling of an existing 1D sewer network model (SWMM and 2D inundation model (BREZO. The 1D-2D hydrodynamic model was developed for the purpose of examining flood incidence due to surcharged water on overland surface. The investigation was carried out by performing sensitivity analysis on the developed model. For the sensitivity analysis, modeling parameters, such as mesh resolution Digital Elevation Model (DEM resolution and roughness were considered. The outcome of the study shows the model is sensitive to changes in these parameters. The performance of the model is significantly influenced, by the Manning's friction value, the DEM resolution and the area of the triangular mesh. Also, changes in the aforementioned modeling parameters influence the Flood characteristics, such as the inundation extent, the flow depth and the velocity across the model domain.
Conservation laws and LETKF with 2D Shallow Water Model
Zeng, Yuefei; Janjic, Tijana
2016-04-01
Numerous approaches have been proposed to maintain physical conservation laws in the numerical weather prediction models. However, to achieve a reliable prediction, adequate initial conditions are also necessary, which are produced by a data assimilation algorithm. If an ensemble Kalman filters (EnKF) is used for this purpose, it has been shown that it could yield unphysical analysis ensemble that for example violates principles of mass conservation and positivity preservation (e.g. Janjic et al 2014) . In this presentation, we discuss the selection of conservation criteria for the analysis step, and start with testing the conservation of mass, energy and enstrophy. The simple experiments deal with nonlinear shallow water equations and simulated observations that are assimilated with LETKF (Localized Ensemble Transform Kalman Filter, Hunt et al. 2007). The model is discretized in a specific way to conserve mass, angular momentum, energy and enstrophy. The effects of the data assimilation on the conserved quantities (of mass, energy and enstrophy) depend on observation covarage, localization radius, observed variable and observation operator. Having in mind that Arakawa (1966) and Arakawa and Lamb (1977) showed that the conservation of both kinetic energy and enstrophy by momentum advection schemes in the case of nondivergent flow prevents systematic and unrealistic energy cascade towards high wave numbers, a cause of excessive numerical noise and possible eventual nonlinear instability, we test the effects on prediction depending on the type of errors in the initial condition. The performance with respect to nonlinear energy cascade is assessed as well.
Simulation of subgrid orographic precipitation with an embedded 2-D cloud-resolving model
Jung, Joon-Hee; Arakawa, Akio
2016-03-01
By explicitly resolving cloud-scale processes with embedded two-dimensional (2-D) cloud-resolving models (CRMs), superparameterized global atmospheric models have successfully simulated various atmospheric events over a wide range of time scales. Up to now, however, such models have not included the effects of topography on the CRM grid scale. We have used both 3-D and 2-D CRMs to simulate the effects of topography with prescribed "large-scale" winds. The 3-D CRM is used as a benchmark. The results show that the mean precipitation can be simulated reasonably well by using a 2-D representation of topography as long as the statistics of the topography such as the mean and standard deviation are closely represented. It is also shown that the use of a set of two perpendicular 2-D grids can significantly reduce the error due to a 2-D representation of topography.
Point Contacts in Modeling Conducting 2D Planar Structures
Thiel, David V; Hettenhausen, Jan; Lewis, Andrew
2015-01-01
Use of an optimization algorithm to improve performance of antennas and electromagnetic structures usually ends up in planar unusual shapes. Using rectangular conducting elements the proposed structures sometimes have connections with only one single point in common between two neighboring areas. The single point connections (point crossing) can affect the electromagnetic performance of the structure. In this letter, we illustrate the influence of point crossing on dipole and loop antennas using MoM, FDTD, and FEM solvers. Current distribution, radiation pattern, and impedance properties for different junctions are different. These solvers do not agree in the modeling of the point crossing junctions which is a warning about uncertainty in using such junctions. However, solvers agree that a negligible change in the junction would significantly change the antenna performance. We propose that one should consider both bridging and chamfering of the conflicting cells to find optimized structures. This reduces the ...
Zhu, Wu-Le; Zhu, Zhiwei; Shi, Yi; Wang, Xinwei; Guan, Kaimin; Ju, Bing-Feng
2016-11-01
In this paper, a new piezo-actuated XY parallel compliant mechanism for large workspace nano-positioning with decoupled motions is developed by incorporating a novel Z-shaped flexure hinge (ZFH)-based mechanism into the mirror-symmetrically distributed structure. The bridge-type mechanism and two-stage leverage mechanisms serve as preliminary displacement amplifiers, while further amplification with motion transfer and decoupled output motions are achieved by means of the ZFH mechanism. Based on finite element theory, a high-precision analytical model of the XY compliant mechanism is established by considering all the connecting linkages as flexible components. Through the improved differential evolution algorithm, the optimized compliant mechanism is capable of performing millimeter-scale workspace nano-positioning with decoupled motions. In addition, the input displacement unbalance, resulting from the lateral force which has potential to damage the piezoelectric actuators, is markedly lowered to a negligible value. The performance of the fabricated compliant mechanism with optimized parameters is investigated to well agree with both the analytical model and ANSYS simulation. In addition, based on the inverse kinematics derived from the model and experimental results, different elliptical vibration trajectories are accurately acquired.
A 2D model to design MHD induction pumps
Stieglitz, R.; Zeininger, J.
2006-09-01
Technical liquid metal systems accompanied by a thermal transfer of energy such as reactor systems, metallurgical processes, metal refinement, casting, etc., require a forced convection of the fluid. The increased temperatures and more often the environmental conditions as, e.g., in a nuclear environment, pumping principles are required, in which rotating parts are absent. Additionally, in many applications a controlled atmosphere is indispensable, in order to ensure the structural integrity of the duct walls. An interesting option to overcome the sealing problem of a mechanical pump towards the surrounding is offered by induction systems. Although their efficiency compared to that of turbo machines is quite low, they have several advantages, which are attractive to the specific requirements in liquid metal applications such as: - low maintenance costs due to the absence of sealings, bearings and moving parts; - low degradation rate of the structural material; - simple replacement of the inductor without cut of the piping system; - fine regulation of flow rate by different inductor connections; - change of pump characteristics without change of the mechanical set-up. Within the article, general design requirements of electromagnetic pumps (EMP) are elaborated. The design of two annular linear induction pumps operating with sodium and lead-bismuth are presented and the calculated pump characteristics and experimentally obtained data are compared. In this context, physical effects leading to deviations between the model and the real data are addressed. Finally, the main results are summarized. Tables 4, Figs 4, Refs 12.
Modelling and simulation of 2D stokesian Squirmers*
Directory of Open Access Journals (Sweden)
Aguillon Nina
2013-01-01
Full Text Available Direct numerical simulations of the individual and collective dynamics of neutral squirmers are presented. “Squirmer” refers to a class of swimmers driven by prescribed tangential deformations at their surface, and “cneutral” means that the swimmer does not apply a force dipole on the fluid. The squirmer model is used in this article to describe self-propelled liquid droplets. Each swimmer is a fluid sphere in Stokes flow without radial velocity and with a prescribed tangential velocity, which is constant in time in the swimmer frame. The interaction between two or more swimmers is taken into account through the relaxation of their translational and angular velocities. The algorithm presented for solving the fluid flow and the motion of the liquid particles is based on a variational formulation written on the whole domain (including the external fluid and the liquid particles and on a fictitious domain approach. The constraint on the tangential velocity of swimmers can be enforced using two different methods: penalty approach of the strain rate tensor on the particles domain, or a saddle-point formulation involving a Lagrange multiplier associated to the constraint. This leads to a minimization problem over unconstrained functional spaces that can be implemented straightforwardly in a finiteelement multi-purpose solver. In order to ensure robustness, a projection algorithm is used to deal with contacts between particles. Two-dimensional numerical simulations implemented with FreeFem++ are presented.
Shen, Xueqin; Yan, Hui; Yan, Weili; Guo, Lei
2007-01-01
In this paper, we introduce multidimensional support vector regression (MSVR) with iterative re-weight least square (IRWLS) based procedure to estimating the regional conductivity in 2D disc head model. The results show that the method is capable of determining for the regional location of the disturbed conductivity in the 2D disc head model with single tissue and estimating for the tissue conductivities in the 2D disc head model with four kinds of tissue. The estimation errors are all within a few percent.
A HORIZONTAL 2-D HYDRAULIC NUMERICAL MODEL AND IT'S APPLICATIONS TO FLOOD FORECAST
Institute of Scientific and Technical Information of China (English)
Minghui YU; Guolu YANG; Jinjun XU
2002-01-01
In this paper,a horizontal 2-D numerical model has been developed to simulate flow processes in dike burst. The finite difference method is used in computation. The model employs 2-D flow equations and can simulate complex flows when supercritical flow and sub-critical flow exist simultaneously such as hydraulic jumps. Several simulated results are worked out to demonstrate the applicability of the numerical model,such as flood propagation on a dry bed of a complex terrain.
DEFF Research Database (Denmark)
Mouritsen, Ole G.; Praestgaard, Eigil
1988-01-01
temperature, the domain-growth kinetics is found to be independent of the value of this parameter over several decades of its range. This suggests that a universal principle is operative. The domain-wall shape is analyzed and shown to be well represented by a hyperbolic tangent function. The growth process......The domain-growth kinetics in two different anisotropic two-dimensional XY-spin models is studied by computer simulation. The models have uniaxial and cubic anisotropy which leads to ground-state orderings which are twofold and fourfold degenerate, respectively. The models are quenched from...... 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...
Quantum chromodynamics, antiferromagnets and XY models from a unified point of view
Hofmann, Christoph P.
2017-03-01
Antiferromagnets and quantum XY magnets in three space dimensions are described by an effective Lagrangian that exhibits the same structure as the effective Lagrangian of quantum chromodynamics with two light flavors. These systems all share a spontaneously broken internal symmetry O (N) → O (N - 1). Although the respective scales differ by many orders of magnitude, the general structure of the low-temperature expansion of the partition function is the same. In the nonabelian case (N ≥ 3), logarithmic terms of the form T8 ln T emerge at three-loop order, while for N = 2 the series only involves powers of T2. The manifestation of the Goldstone boson interaction in the pressure, order parameter, and susceptibility is explored in presence of an external field.
Hui, Ning-Ju; Xu, Yang-Yang; Wang, Jicheng; Zhang, Yixin; Hu, Zheng-Da
2017-04-01
We investigate the properties of geometric quantum coherence in the XY spin-1/2 chain with staggered Dzyaloshinsky-Moriya interaction via the quantum renormalization-group approach. It is shown that the geometric quantum coherence and its coherence susceptibility are effective to detect the quantum phase transition. In the thermodynamic limit, the geometric quantum coherence exhibits a sudden jump. The coherence susceptibilities versus the anisotropy parameter and the Dzyaloshinsky-Moriya interaction are infinite and vanishing, respectively, illustrating the distinct roles of the anisotropy parameter and the Dzyaloshinsky-Moriya interaction in quantum phase transition. Moreover, we also explore the finite-size scaling behaviors of the coherence susceptibilities. For a finite-size chain, the coherence susceptibility versus the phase-transition parameter is always maximal at the critical point, indicating the dramatic quantum fluctuation. Besides, we show that the correlation length can be revealed by the scaling exponent for the coherence susceptibility versus the Dzyaloshinsky-Moriya interaction.
Quantum Chromodynamics, Antiferromagnets and XY Models from a Unified Point of View
Hofmann, Christoph P
2016-01-01
Antiferromagnets and quantum XY magnets in three space dimensions are described by an effective Lagrangian that exhibits the same structure as the effective Lagrangian of quantum chromodynamics with two light flavors. These systems all share a spontaneously broken internal symmetry O($N$) $\\to$ O($N$-1). Although the respective scales differ by many orders of magnitude, the general structure of the low-temperature expansion of the partition function is the same. In the nonabelian case, logarithmic terms of the form $T^8 \\ln T$ emerge at three-loop order, while for $N$=2 the series only involves powers of $T^2$. The manifestation of the Goldstone boson interaction in the pressure, order parameter, and susceptibility is explored in presence of an external field.
2-D model for pollutant dispersion at the coastal outfall off Paradip
Digital Repository Service at National Institute of Oceanography (India)
Suryanarayana, A.; Babu, M.T.; Vethamony, P.; Gouveia, A.D.
Simulation of dispersion of the effluent discharge has been carried out using 2-D Model to verify the advection and diffusion of the pollutant patch of the proposed effluent disposal off Paradip, Orissa, India. The simulation of dispersion...
Ghostine, Rabih
2014-12-01
In open channel networks, flow is usually approximated by the one-dimensional (1D) Saint-Venant equations coupled with an empirical junction model. In this work, a comparison in terms of accuracy and computational cost between a coupled 1D-2D shallow water model and a fully two-dimensional (2D) model is presented. The paper explores the ability of a coupled model to simulate the flow processes during supercritical flows in crossroads. This combination leads to a significant reduction in the computational time, as a 1D approach is used in branches and a 2D approach is employed in selected areas only where detailed flow information is essential. Overall, the numerical results suggest that the coupled model is able to accurately simulate the main flow processes. In particular, hydraulic jumps, recirculation zones, and discharge distribution are reasonably well reproduced and clearly identified. Overall, the proposed model leads to a 30% reduction in run times. © 2014 International Association for Hydro-Environment Engineering and Research.
Quasi-long-range ordering in a finite-size 2D Heisenberg model
Kapikranian, O; Holovatch, Yu; Berche, Bertrand; Holovatch, Yurij; Kapikranian, Oleksandr
2006-01-01
We analyse the low-temperature behaviour of the Heisenberg model on a two-dimensional lattice of finite size. Presence of a residual magnetisation in a finite-size system enables us to use the spin wave approximation, which is known to give reliable results for the XY model at low temperatures T. For the system considered, we find that the spin-spin correlation function decays as 1/r^eta(T) for large separations r bringing about presence of a quasi-long-range ordering. We give analytic estimates for the exponent eta(T) in different regimes and support our findings by Monte Carlo simulations of the model on lattices of different sizes at different temperatures.
Aarts, Gert
2010-01-01
The three-dimensional XY model is studied at finite chemical potential using complex Langevin dynamics. The validity of the approach is probed at small chemical potential using imaginary chemical potential and continuity arguments, and at larger chemical potential by comparison with the world line method. While complex Langevin works for larger beta, we find that it fails for smaller beta, in the region of the phase diagram corresponding to the disordered phase. Diagnostic tests are developed to identify symptoms correlated with incorrect convergence. We argue that the erroneous behaviour at smaller beta is not due to the sign problem, but rather resembles dynamics observed in complex Langevin simulations of simple models with complex noise.
Activated sludge models ASM1, ASM2, ASM2d and ASM3
DEFF Research Database (Denmark)
Henze, Mogens; Gujer, W.; Mino, T.;
This book has been produced to give a total overview of the Activated Sludge Model (ASM) family at the start of 2000 and to give the reader easy access to the different models in their original versions. It thus presents ASM1, ASM2, ASM2d and ASM3 together for the first time.Modelling of activated...... sludge processes has become a common part of the design and operation of wastewater treatment plants. Today models are being used in design, control, teaching and research.ContentsASM3: Introduction, Comparison of ASM1 and ASM3, ASM3: Definition of compounds in the model, ASM3: Definition of processes...... in the Model, ASM3: Stoichiometry, ASM3: Kinetics, Limitations of ASM3, Aspects of application of ASM3, ASM3C: A Carbon based model, Conclusion ASM 2d: Introduction, Conceptual Approach, ASM 2d, Typical Wastewater Characteristics and Kinetic and Stoichiometric Constants, Limitations, Conclusion ASM 2...
A 2D spring model for the simulation of ultrasonic wave propagation in nonlinear hysteretic media.
Delsanto, P P; Gliozzi, A S; Hirsekorn, M; Nobili, M
2006-07-01
A two-dimensional (2D) approach to the simulation of ultrasonic wave propagation in nonclassical nonlinear (NCNL) media is presented. The approach represents the extension to 2D of a previously proposed one dimensional (1D) Spring Model, with the inclusion of a PM space treatment of the intersticial regions between grains. The extension to 2D is of great practical relevance for its potential applications in the field of quantitative nondestructive evaluation and material characterization, but it is also useful, from a theoretical point of view, to gain a better insight of the interaction mechanisms involved. The model is tested by means of virtual 2D experiments. The expected NCNL behaviors are qualitatively well reproduced.
DEVELOPMENT OF COUPLED 1D-2D MATHEMATICAL MODELS FOR TIDAL RIVERS
Institute of Scientific and Technical Information of China (English)
XU Zu-xin; YIN Hai-long
2004-01-01
Some coupled 1D-2D hydrodynamic and water quality models depicting tidal water bodies with complex topography were presented. For the coupled models, finite element method was used to solve the governing equations so as to study tidal rivers with complex topography. Since the 1D and 2D models were coupled, the principle of model coupling was proposed to account appropriately for the factors of water level, flow and pollutant flux and the related dynamical behavior was simulated. Specifically the models were used to probe quantitative pollution contribution of receiving water from neighboring Jiangsu and Zhejiang Provinces to the pollution in the Huangpu River passing through Shanghai City. Numerical examples indicated that the developed coupled 1D-2D models are applicable in tidal river network region of Shanghai.
Granato, Enzo
2012-02-01
Phase coherence and vortex order in the fully frustrated XY model on a two-dimensional honeycomb lattice are studied by extensive Monte Carlo simulations using the parallel tempering method and finite-size scaling. No evidence is found for an equilibrium order-disorder or a spin/vortex-glass transition, suggested in previous simulation works. Instead, the scaling analysis of correlations of phase and vortex variables in the full equilibrated system is consistent with a phase transition where the critical temperature vanishes and the correlation lengths diverge as a power law with decreasing temperatures and corresponding critical exponents νph and νv. This behavior and the near agreement of the critical exponents suggest a zero-temperature transition scenario where phase and vortex variables remain coupled on large length scales.
Gaurier, Benoît; Cébron, David
2010-01-01
A model using wake oscillators is developed to predict the 2D motion in a transverse plan of two rigid cylinders in tandem arrangement. This model of the wake dynamics is validated with experimental data from previous trials which took place at the Ifremer flume tank in Boulogne-sur-Mer, France. The agreement between the model and the experimental results allows using this model as a simple computational tool in the prediction of 2D Vortex-Induced Vibrations (VIV) and, after some futher developments, Wake-Induced Oscillations (WIO) effects.
Palma, G; Niedermayer, F; Rácz, Z; Riveros, A; Zambrano, D
2016-08-01
The zero-temperature, classical XY model on an L×L square lattice is studied by exploring the distribution Φ_{L}(y) of its centered and normalized magnetization y in the large-L limit. An integral representation of the cumulant generating function, known from earlier works, is used for the numerical evaluation of Φ_{L}(y), and the limit distribution Φ_{L→∞}(y)=Φ_{0}(y) is obtained with high precision. The two leading finite-size corrections Φ_{L}(y)-Φ_{0}(y)≈a_{1}(L)Φ_{1}(y)+a_{2}(L)Φ_{2}(y) are also extracted both from numerics and from analytic calculations. We find that the amplitude a_{1}(L) scales as ln(L/L_{0})/L^{2} and the shape correction function Φ_{1}(y) can be expressed through the low-order derivatives of the limit distribution, Φ_{1}(y)=[yΦ_{0}(y)+Φ_{0}^{'}(y)]^{'}. Thus, Φ_{1}(y) carries the same universal features as the limit distribution and can be used for consistency checks of universality claims based on finite-size systems. The second finite-size correction has an amplitude a_{2}(L)∝1/L^{2} and one finds that a_{2}Φ_{2}(y)≪a_{1}Φ_{1}(y) already for small system size (L>10). We illustrate the feasibility of observing the calculated finite-size corrections by performing simulations of the XY model at low temperatures, including T=0.
Analysis of vegetation effect on waves using a vertical 2-D RANS model
A vertical two-dimensional (2-D) model has been applied in the simulation of wave propagation through vegetated water bodies. The model is based on an existing model SOLA-VOF which solves the Reynolds-Averaged Navier-Stokes (RANS) equations with the finite difference method on a staggered rectangula...
Tidal regime in Gulf of Kutch, west coast of India, by 2D model
Digital Repository Service at National Institute of Oceanography (India)
Unnikrishnan, A; Gouveia, A; Vethamony, P.
A 2D barotropic numerical model is developed for the Gulf of Kutch with a view to synthesize available information on tides and currents in the Gulf. A comparison of model results with moored current meter observations shows that the model...
Simulation of Cardiac Arrhythmias Using a 2D Heterogeneous Whole Heart Model.
Balakrishnan, Minimol; Chakravarthy, V Srinivasa; Guhathakurta, Soma
2015-01-01
Simulation studies of cardiac arrhythmias at the whole heart level with electrocardiogram (ECG) gives an understanding of how the underlying cell and tissue level changes manifest as rhythm disturbances in the ECG. We present a 2D whole heart model (WHM2D) which can accommodate variations at the cellular level and can generate the ECG waveform. It is shown that, by varying cellular-level parameters like the gap junction conductance (GJC), excitability, action potential duration (APD) and frequency of oscillations of the auto-rhythmic cell in WHM2D a large variety of cardiac arrhythmias can be generated including sinus tachycardia, sinus bradycardia, sinus arrhythmia, sinus pause, junctional rhythm, Wolf Parkinson White syndrome and all types of AV conduction blocks. WHM2D includes key components of the electrical conduction system of the heart like the SA (Sino atrial) node cells, fast conducting intranodal pathways, slow conducting atriovenctricular (AV) node, bundle of His cells, Purkinje network, atrial, and ventricular myocardial cells. SA nodal cells, AV nodal cells, bundle of His cells, and Purkinje cells are represented by the Fitzhugh-Nagumo (FN) model which is a reduced model of the Hodgkin-Huxley neuron model. The atrial and ventricular myocardial cells are modeled by the Aliev-Panfilov (AP) two-variable model proposed for cardiac excitation. WHM2D can prove to be a valuable clinical tool for understanding cardiac arrhythmias.
Form factors of the finite quantum XY-chain
Energy Technology Data Exchange (ETDEWEB)
Iorgov, Nikolai, E-mail: iorgov@bitp.kiev.ua [Bogolyubov Institute for Theoretical Physics, Kiev 03680 (Ukraine)
2011-08-19
Explicit factorized formulas for the matrix elements (form factors) of the spin operators {sigma}{sup x} and {sigma}{sup y} between the eigenvectors of the Hamiltonian of the finite quantum periodic XY-chain in a transverse field were derived. The derivation is based on the relations between three models: the model of quantum XY-chain, Ising model on 2D lattice and N = 2 Baxter-Bazhanov-Stroganov {tau}{sup (2)}-model. Due to these relations we transfer the formulas for the form factors of the latter model recently obtained by the use of separation of variables method to the model of quantum XY-chain. Hopefully, the formulas for the form factors will help in analysis of multipoint dynamic correlation functions at a finite temperature. As an example, we re-derive the asymptotics of the two-point correlation function in the disordered phase without the use of the Toeplitz determinants and the Wiener-Hopf factorization method.
Popov, Alexander P.; Gloria Pini, Maria; Rettori, Angelo
2016-03-01
The metastable states of a finite-size chain of N classical spins described by the chiral XY-model on a discrete one-dimensional lattice are calculated by means of a general theoretical method recently developed by one of us. This method allows one to determine all the possible equilibrium magnetic states in an accurate and systematic way. The ground state of a chain consisting of N classical XY spins is calculated in the presence of (i) a symmetric ferromagnetic exchange interaction, favoring parallel alignment of nearest neighbor spins, (ii) a uniaxial anisotropy, favoring a given direction in the film plane, and (iii) an antisymmetric Dzyaloshinskii-Moriya interaction (DMI), favoring perpendicular alignment of nearest neighbor spins. In addition to the ground state with a non-uniform helical spin arrangement, which originates from the energy competition in the finite-size chain with open boundary conditions, we have found a considerable number of higher-energy equilibrium states. In the investigated case of a chain with N=10 spins and a DMI much smaller than the in-plane uniaxial anisotropy, it turns out that a metastable (unstable) state of the finite chain is characterized by a configuration where none (at least one) of the inner spins is nearly parallel to the hard axis. The role of the DMI is to establish a unique rotational sense for the helical ground state. Moreover, the number of both metastable and unstable equilibrium states is doubled with respect to the case of zero DMI. This produces modifications in the Peierls-Nabarro potential encountered by a domain wall during its displacement along the discrete spin chain.
Evaluation of 2D shallow-water model for spillway flow with a complex geometry
Although the two-dimensional (2D) shallow water model is formulated based on several assumptions such as hydrostatic pressure distribution and vertical velocity is negligible, as a simple alternative to the complex 3D model, it has been used to compute water flows in which these assumptions may be ...
Validity of Mixed 2D and 3D Cadastral Parcels in the Land Administration Domain Model
Thompson, R.J.; Van Oosterom, P.J.M.
2012-01-01
In the move towards a 3D Cadastre, many jurisdictions are considering a hybrid 2D/3D database as either a stage of development or as a target in itself (van Oosterom, Stoter, Ploeger, Thompson and Karki 2011). The Land Administration Domain Model (LADM), which is the underlying model for the ISO 191
Comparison between 2D turbulence model ESEL and experimental data from AUG and COMPASS tokamaks
DEFF Research Database (Denmark)
Ondac, Peter; Horacek, Jan; Seidl, Jakub;
2015-01-01
In this article we have used the 2D fluid turbulence numerical model, ESEL, to simulate turbulent transport in edge tokamak plasma. Basic plasma parameters from the ASDEX Upgrade and COMPASS tokamaks are used as input for the model, and the output is compared with experimental observations obtained...
Validation of DYSTOOL for unsteady aerodynamic modeling of 2D airfoils
González, A.; Gomez-Iradi, S.; Munduate, X.
2014-06-01
From the point of view of wind turbine modeling, an important group of tools is based on blade element momentum (BEM) theory using 2D aerodynamic calculations on the blade elements. Due to the importance of this sectional computation of the blades, the National Renewable Wind Energy Center of Spain (CENER) developed DYSTOOL, an aerodynamic code for 2D airfoil modeling based on the Beddoes-Leishman model. The main focus here is related to the model parameters, whose values depend on the airfoil or the operating conditions. In this work, the values of the parameters are adjusted using available experimental or CFD data. The present document is mainly related to the validation of the results of DYSTOOL for 2D airfoils. The results of the computations have been compared with unsteady experimental data of the S809 and NACA0015 profiles. Some of the cases have also been modeled using the CFD code WMB (Wind Multi Block), within the framework of a collaboration with ACCIONA Windpower. The validation has been performed using pitch oscillations with different reduced frequencies, Reynolds numbers, amplitudes and mean angles of attack. The results have shown a good agreement using the methodology of adjustment for the value of the parameters. DYSTOOL have demonstrated to be a promising tool for 2D airfoil unsteady aerodynamic modeling.
Impact of high speed civil transports on stratospheric ozone. A 2-D model investigation
Energy Technology Data Exchange (ETDEWEB)
Kinnison, D.E.; Connell, P.S. [Lawrence Livermore National Lab., CA (United States)
1997-12-31
This study investigates the effect on stratospheric ozone from a fleet of proposed High Speed Civil Transports (HSCTs). The new LLNL 2-D operator-split chemical-radiative-transport model of the troposphere and stratosphere is used for this HSCT investigation. This model is integrated in a diurnal manner, using an implicit numerical solver. Therefore, rate coefficients are not modified by any sort of diurnal average factor. This model also does not make any assumptions on lumping of chemical species into families. Comparisons to previous model-derived HSCT assessment of ozone change are made, both to the previous LLNL 2-D model and to other models from the international assessment modeling community. The sensitivity to the NO{sub x} emission index and sulfate surface area density is also explored. (author) 7 refs.
Hemodynamic simulation of the heart using a 2D model and MR data
DEFF Research Database (Denmark)
Adeler, Pernille Thorup
2002-01-01
Computational models of the blood flow in the heart are a useful tool for studying the functioning of the heart. The purpose of this thesis is to achieve a better understanding of hemodynamics of the normal and diseased hearts through the use of a computational model and magnetic resonance (MR......) data. We present a 2D computational model of the blood flow in the left side of the heart. The work is based on Peskin and McQueen's 2D model dimensioned to data on the dog heart, which we improve and adjust using physiological knowledge and MR velocity data to achieve a model of the human heart...... parameter values. This is our reference model, which gives representative simulation results. We compare a simulation using our reference model with an MR velocity data set obtained from a healthy human. The comparison is carried out for the intraventricular velocity field and the velocity time curves over...
Parallelized CCHE2D flow model with CUDA Fortran on Graphics Process Units
This paper presents the CCHE2D implicit flow model parallelized using CUDA Fortran programming technique on Graphics Processing Units (GPUs). A parallelized implicit Alternating Direction Implicit (ADI) solver using Parallel Cyclic Reduction (PCR) algorithm on GPU is developed and tested. This solve...
2D-Raman-THz spectroscopy: A sensitive test of polarizable water models
Energy Technology Data Exchange (ETDEWEB)
Hamm, Peter, E-mail: peter.hamm@chem.uzh.ch [Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich (Switzerland)
2014-11-14
In a recent paper, the experimental 2D-Raman-THz response of liquid water at ambient conditions has been presented [J. Savolainen, S. Ahmed, and P. Hamm, Proc. Natl. Acad. Sci. U. S. A. 110, 20402 (2013)]. Here, all-atom molecular dynamics simulations are performed with the goal to reproduce the experimental results. To that end, the molecular response functions are calculated in a first step, and are then convoluted with the laser pulses in order to enable a direct comparison with the experimental results. The molecular dynamics simulation are performed with several different water models: TIP4P/2005, SWM4-NDP, and TL4P. As polarizability is essential to describe the 2D-Raman-THz response, the TIP4P/2005 water molecules are amended with either an isotropic or a anisotropic polarizability a posteriori after the molecular dynamics simulation. In contrast, SWM4-NDP and TL4P are intrinsically polarizable, and hence the 2D-Raman-THz response can be calculated in a self-consistent way, using the same force field as during the molecular dynamics simulation. It is found that the 2D-Raman-THz response depends extremely sensitively on details of the water model, and in particular on details of the description of polarizability. Despite the limited time resolution of the experiment, it could easily distinguish between various water models. Albeit not perfect, the overall best agreement with the experimental data is obtained for the TL4P water model.
Park, Elisa L.
2009-01-01
The purpose of this study is to understand the dynamics of Korean students' international mobility to study abroad by using the 2-D Model. The first D, "the driving force factor," explains how and what components of the dissatisfaction with domestic higher education perceived by Korean students drives students' outward mobility to seek…
Multiple Ising models coupled to 2-d gravity: a CSD analysis
Bowick, Mark; Falcioni, Marco; Harris, Geoffrey; Marinari, Enzo
1994-04-01
We simulate single and multiple Ising models coupled to 2-d gravity and we measure critical slowing down (CSD) with the standard methods. We find that the Swendsen-Wang and Wolff cluster algorithms do not eliminate CSD. We interpret the result as an effect of the mesh dynamics.
Strict System Equivalence of 2D Linear Discrete State Space Models
Directory of Open Access Journals (Sweden)
Mohamed S. Boudellioua
2012-01-01
Full Text Available The connection between the polynomial matrix descriptions (PMDs of the well-known regular and singular 2D linear discrete state space models is considered. It is shown that the transformation of strict system equivalence in the sense of Fuhrmann provides the basis for this connection. The exact form of the transformation is established for both the regular and singular cases.
New technologies of 2-D and 3-D modeling for analysis and management of natural resources
Cheremisina, E. N.; Lyubimova, A. V.; Kirpicheva, E. Yu.
2016-09-01
For ensuring technological support of research and administrative activity in the sphere of environmental management a specialized modular program complex was developed. The special attention in developing a program complex is focused to creation of convenient and effective tools for creation and visualization 2d and 3D models providing the solution of tasks of the analysis and management of natural resources.
Coupled BOUSS-2D and CMS-Wave Modeling Approach for Harbor Projects
2012-08-01
al. 2011; Demirbilek et al. 2007) is part of the Coastal Modeling System ( CMS ) for simulating combined waves, currents, sediment transport, and...III. 2011. Verification and Validation of the Coastal Modeling System : Report 2, CMS -Wave, Tech. Report ERDC/CHL-TR-11-10, U.S. Army Engineer R&D...ERDC/CHL CHETN-IV-84 August 2012 Approved for public release; distribution is unlimited. Coupled BOUSS-2D and CMS -Wave Modeling Approach for
Structure of a model salt bridge in solution investigated with 2D-IR spectroscopy
Huerta-Viga, Adriana; Amirjalayer, Saeed; Woutersen, Sander
2013-01-01
Salt bridges are known to be important for the stability of protein conformation, but up to now it has been difficult to study their geometry in solution. Here we characterize the spatial structure of a model salt bridge between guanidinium (Gdm+) and acetate (Ac-) using two-dimensional vibrational (2D-IR) spectroscopy. We find that as a result of salt bridging the infrared response of Gdm+ and Ac- change significantly, and in the 2D-IR spectrum, salt bridging of the molecules appears as cross peaks. From the 2D-IR spectrum we determine the relative orientation of the transition-dipole moments of the vibrational modes involved in the salt bridge, as well as the coupling between them. In this manner we reconstruct the geometry of the solvated salt bridge.
A novel explicit 2D+t cyclic shape model applied to echocardiography.
Casero, Ramón; Noble, J Alison
2008-01-01
In this paper, we propose a novel explicit 2D+t cyclic shape model that extends the Point Distribution Model (PDM) to shapes like myocardial contours with cyclic dynamics. We also propose an extension to Procrustes alignment that removes pose and subject size variability while maintaining dynamic effects. Our model draws on ideas from Principal Component Analysis (PCA), Multidimensional Scaling (MDS) and Kernel PCA (KPCA) and solves 3 shortcomings of previous implicit models: (1) cardiac cycles in the data set do not each need to have the same number of frames, (2) the required number of subjects for statistically significant results is substantially reduced and (3) the displacement of contour points incorporates time as an explicit variable. We illustrate our method by computing models of the myocardium in the 4 principal planes of 2D+t echocardiography data.
Modeling Overlapping Laminations in Magnetic Core Materials Using 2-D Finite-Element Analysis
DEFF Research Database (Denmark)
Jensen, Bogi Bech; Guest, Emerson David; Mecrow, Barrie C.
2015-01-01
and a composite material is created, which has the same magnetization characteristic. The benefit of this technique is that it allows a designer to perform design and optimization of magnetic cores with overlapped laminations using a 2-D FE model rather than a 3-D FE model, which saves modeling and simulation...... time. The modeling technique is verified experimentally by creating a composite material of a lap joint with a 3-mm overlapping region and using it in a 2-D FE model of a ring sample made up of a stack of 20 laminations. The B-H curve of the simulated ring sample is compared with the B-H curve obtained...
Generic 2-D River Network Modeling of Flow and Sediment Transports
Guo, W.; Wang, C.; Xiang, X.; Ma, T.
2012-04-01
A generic 2D river network model of flow and sediment transports is proposed for the flow and sediment simulation in the complex river network. The paper expands the three-step method adopted in the 1D river network to the 2D river network simulation. A 2D river network model is divided into several cells, including single river cell, "tree-like" river cell, "ring-like" river cell and "cross-like" river cell, which can reflect the interactive influence of flow field in the bifurcated channel and applies to generic 2D simulation. Based on equation of the 2D shallow water and unsteady non-uniform suspended sediment, the relationship between the variables (water level, discharge and sediment concentration) of each section and those of the boundaries are obtained through the full implicit matrix chase-after method. Through the conservation of water and sediment on the boundaries, the water level and sediment concentration on the nodes can be got by solving the irregular sparse matrix of conservation equation, so as to implement the coupled simulation of flow and sediment in the whole river network. The paper take the Chengtong River Reach located in the low reaches of Yangtze River as the example of "cross-like" river to verify the algorithm. The model is calibrated using the measured data. A comparison of calculated water level, discharge and sediment concentration shows that the generic model can reflex the interactive influence of flow field, with reasonable accuracy, especially in the bifurcated channel.
Reliability of a Novel Model for Drug Release from 2D HPMC-Matrices
Directory of Open Access Journals (Sweden)
Rumiana Blagoeva
2010-04-01
Full Text Available A novel model of drug release from 2D-HPMC matrices is considered. Detailed mathematical description of matrix swelling and the effect of the initial drug loading are introduced. A numerical approach to solution of the posed nonlinear 2D problem is used on the basis of finite element domain approximation and time difference method. The reliability of the model is investigated in two steps: numerical evaluation of the water uptake parameters; evaluation of drug release parameters under available experimental data. The proposed numerical procedure for fitting the model is validated performing different numerical examples of drug release in two cases (with and without taking into account initial drug loading. The goodness of fit evaluated by the coefficient of determination is presented to be very good with few exceptions. The obtained results show better model fitting when accounting the effect of initial drug loading (especially for larger values.
Reliability analysis of diesel engine crankshaft based on 2D stress strength interference model
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
A 2D stress strength interference model (2D-SSIM) considering that the fatigue reliability of engineering structural components has close relationship to load asymmetric ratio and its variability to some extent is put forward. The principle, geometric schematic and limit state equation of this model are presented. Reliability evaluation for a kind of diesel engine crankshaft was made based on this theory, in which multi-axial loading fatigue criteria was employed. Because more important factors, i.e.stress asymmetric ratio and its variability, are considered, it theoretically can make more accurate evaluation for structural component reliability than the traditional interference model. Correspondingly, a Monte-Carlo Method simulation solution is also given. The computation suggests that this model can yield satisfactory reliability evaluation.
Simplified 2D Bidomain Model of Whole Heart Electrical Activity and ECG Generation
Sovilj, Siniša; Magjarević, Ratko; Abed, Amr Al; Lovell, Nigel H.; Dokos, Socrates
2014-06-01
The aim of this study was the development of a geometrically simple and highly computationally-efficient two dimensional (2D) biophysical model of whole heart electrical activity, incorporating spontaneous activation of the sinoatrial node (SAN), the specialized conduction system, and realistic surface ECG morphology computed on the torso. The FitzHugh-Nagumo (FHN) equations were incorporated into a bidomain finite element model of cardiac electrical activity, which was comprised of a simplified geometry of the whole heart with the blood cavities, the lungs and the torso as an extracellular volume conductor. To model the ECG, we placed four electrodes on the surface of the torso to simulate three Einthoven leads VI, VII and VIII from the standard 12-lead system. The 2D model was able to reconstruct ECG morphology on the torso from action potentials generated at various regions of the heart, including the sinoatrial node, atria, atrioventricular node, His bundle, bundle branches, Purkinje fibers, and ventricles. Our 2D cardiac model offers a good compromise between computational load and model complexity, and can be used as a first step towards three dimensional (3D) ECG models with more complex, precise and accurate geometry of anatomical structures, to investigate the effect of various cardiac electrophysiological parameters on ECG morphology.
Comparison between 2D and 3D Modelling of Induction Machine Using Finite Element Method
Directory of Open Access Journals (Sweden)
Zelmira Ferkova
2015-01-01
Full Text Available The paper compares two different ways (2D and 3D of modelling of two-phase squirrel-cage induction machine using the finite element method (FEM. It focuses mainly on differences between starting characteristics given from both types of the model. It also discusses influence of skew rotor slots on harmonic content in air gap flux density and summarizes some issues of both approaches.
Directory of Open Access Journals (Sweden)
Wu Steven H
2012-06-01
Full Text Available Abstract Background Two-dimensional polyacrylamide gel electrophoresis (2D PAGE is commonly used to identify differentially expressed proteins under two or more experimental or observational conditions. Wu et al (2009 developed a univariate probabilistic model which was used to identify differential expression between Case and Control groups, by applying a Likelihood Ratio Test (LRT to each protein on a 2D PAGE. In contrast to commonly used statistical approaches, this model takes into account the two possible causes of missing values in 2D PAGE: either (1 the non-expression of a protein; or (2 a level of expression that falls below the limit of detection. Results We develop a global Bayesian model which extends the previously described model. Unlike the univariate approach, the model reported here is able treat all differentially expressed proteins simultaneously. Whereas each protein is modelled by the univariate likelihood function previously described, several global distributions are used to model the underlying relationship between the parameters associated with individual proteins. These global distributions are able to combine information from each protein to give more accurate estimates of the true parameters. In our implementation of the procedure, all parameters are recovered by Markov chain Monte Carlo (MCMC integration. The 95% highest posterior density (HPD intervals for the marginal posterior distributions are used to determine whether differences in protein expression are due to differences in mean expression intensities, and/or differences in the probabilities of expression. Conclusions Simulation analyses showed that the global model is able to accurately recover the underlying global distributions, and identify more differentially expressed proteins than the simple application of a LRT. Additionally, simulations also indicate that the probability of incorrectly identifying a protein as differentially expressed (i.e., the False
Stochastic 2-D Models of Galaxy Disk Evolution. The Galaxy M33
Mineikis, Tadas
2015-01-01
We have developed a fast numerical 2-D model of galaxy disk evolution (resolved along the galaxy radius and azimuth) by adopting a scheme of parameterized stochastic self-propagating star formation. We explore the parameter space of the model and demonstrate its capability to reproduce 1-D radial profiles of the galaxy M33: gas surface density, surface brightness in the i and GALEX FUV passbands, and metallicity.
Ice shelf flexures modeled with a 2-D elastic flow line model
Directory of Open Access Journals (Sweden)
Y. V. Konovalov
2011-10-01
Full Text Available Ice shelf flexures modeling was performed using a 2-D finite-difference elastic model, which takes into account sub-ice-shelf sea water flow. The sub-ice water flow was described by the wave equation for the sub-ice-shelf pressure perturbations (Holdsworth and Glynn, 1978. In the model ice shelf flexures result from variations in ocean pressure due to changes in prescribed sea levels. The numerical experiments were performed for a flow line down one of the fast flowing ice streams of the Academy of Sciences Ice Cap. The profile includes a part of the adjacent ice shelf. The numerical experiments were carried out for harmonic incoming pressure perturbations P' and the ice shelf flexures were obtained for a wide spectrum of the pressure perturbations frequencies, ranging from tidal periods down to periods of a few seconds (0.004..0.02 Hz. The amplitudes of the ice shelf deflections obtained by the model achieve a maxima at about T ≈ 165 s in concordance with previous investigations of the impact of waves on Antarctic ice shelves (Bromirski et al., 2010. The explanation of the effect is found in the solution of the corresponding eigenvalue problem revealing the existence of a resonance at these high frequencies.
Mechanical Modelling of Pultrusion Process: 2D and 3D Numerical Approaches
DEFF Research Database (Denmark)
Baran, Ismet; Hattel, Jesper Henri; Akkerman, Remko
2015-01-01
The process induced variations such as residual stresses and distortions are a critical issue in pultrusion, since they affect the structural behavior as well as the mechanical properties and geometrical precision of the final product. In order to capture and investigate these variations......, a mechanical analysis should be performed. In the present work, the two dimensional (2D) quasi-static plane strain mechanical model for the pultrusion of a thick square profile developed by the authors is further improved using generalized plane strain elements. In addition to that, a more advanced 3D thermo......-chemical-mechanical analysis is carried out using 3D quadratic elements which is a novel application for the numerical modelling of the pultrusion process. It is found that the 2D mechanical models give relatively reasonable and accurate stress and displacement evolutions in the transverse direction as compared to the 3D...
3D Modeling of Transformer Substation Based on Mapping and 2D Images
Directory of Open Access Journals (Sweden)
Lei Sun
2016-01-01
Full Text Available A new method for building 3D models of transformer substation based on mapping and 2D images is proposed in this paper. This method segments objects of equipment in 2D images by using k-means algorithm in determining the cluster centers dynamically to segment different shapes and then extracts feature parameters from the divided objects by using FFT and retrieves the similar objects from 3D databases and then builds 3D models by computing the mapping data. The method proposed in this paper can avoid the complex data collection and big workload by using 3D laser scanner. The example analysis shows the method can build coarse 3D models efficiently which can meet the requirements for hazardous area classification and constructions representations of transformer substation.
Numerical Methods and Comparisons for 1D and Quasi 2D Streamer Propagation Models
Huang, Mengmin; Guan, Huizhe; Zeng, Rong
2016-01-01
In this work, we propose four different strategies to simulate the one-dimensional (1D) and quasi two-dimensional (2D) model for streamer propagation. Each strategy involves of one numerical method for solving Poisson's equation and another method for solving continuity equations in the models, and a total variation diminishing three-stage Runge-Kutta method in temporal discretization. The numerical methods for Poisson's equation include finite volume method, discontinuous Galerkin methods, mixed finite element method and least-squared finite element method. The numerical method for continuity equations is chosen from the family of discontinuous Galerkin methods. The accuracy tests and comparisons show that all of these four strategies are suitable and competitive in streamer simulations from the aspects of accuracy and efficiency. By applying any strategy in real simulations, we can study the dynamics of streamer propagations and influences due to the change of parameters in both of 1D and quasi 2D models. T...
A depth-averaged 2-D model of flow and sediment transport in coastal waters
Sanchez, Alejandro; Wu, Weiming; Beck, Tanya M.
2016-11-01
A depth-averaged 2-D model has been developed to simulate unsteady flow and nonuniform sediment transport in coastal waters. The current motion is computed by solving the phase-averaged 2-D shallow water flow equations reformulated in terms of total-flux velocity, accounting for the effects of wave radiation stresses and general diffusion or mixing induced by current, waves, and wave breaking. The cross-shore boundary conditions are specified by assuming fully developed longshore current and wave setup that are determined using the reduced 1-D momentum equations. A 2-D wave spectral transformation model is used to calculate the wave height, period, direction, and radiation stresses, and a surface wave roller model is adopted to consider the effects of surface roller on the nearshore currents. The nonequilibrium transport of nonuniform total-load sediment is simulated, considering sediment entrainment by current and waves, the lag of sediment transport relative to the flow, and the hiding and exposure effect of nonuniform bed material. The flow and sediment transport equations are solved using an implicit finite volume method on a variety of meshes including nonuniform rectangular, telescoping (quadtree) rectangular, and hybrid triangular/quadrilateral meshes. The flow and wave models are integrated through a carefully designed steering process. The model has been tested in three field cases, showing generally good performance.
TRENT2D WG: a smart web infrastructure for debris-flow modelling and hazard assessment
Zorzi, Nadia; Rosatti, Giorgio; Zugliani, Daniel; Rizzi, Alessandro; Piffer, Stefano
2016-04-01
Mountain regions are naturally exposed to geomorphic flows, which involve large amounts of sediments and induce significant morphological modifications. The physical complexity of this class of phenomena represents a challenging issue for modelling, leading to elaborate theoretical frameworks and sophisticated numerical techniques. In general, geomorphic-flows models proved to be valid tools in hazard assessment and management. However, model complexity seems to represent one of the main obstacles to the diffusion of advanced modelling tools between practitioners and stakeholders, although the UE Flood Directive (2007/60/EC) requires risk management and assessment to be based on "best practices and best available technologies". Furthermore, several cutting-edge models are not particularly user-friendly and multiple stand-alone software are needed to pre- and post-process modelling data. For all these reasons, users often resort to quicker and rougher approaches, leading possibly to unreliable results. Therefore, some effort seems to be necessary to overcome these drawbacks, with the purpose of supporting and encouraging a widespread diffusion of the most reliable, although sophisticated, modelling tools. With this aim, this work presents TRENT2D WG, a new smart modelling solution for the state-of-the-art model TRENT2D (Armanini et al., 2009, Rosatti and Begnudelli, 2013), which simulates debris flows and hyperconcentrated flows adopting a two-phase description over a mobile bed. TRENT2D WG is a web infrastructure joining advantages offered by the software-delivering model SaaS (Software as a Service) and by WebGIS technology and hosting a complete and user-friendly working environment for modelling. In order to develop TRENT2D WG, the model TRENT2D was converted into a service and exposed on a cloud server, transferring computational burdens from the user hardware to a high-performing server and reducing computational time. Then, the system was equipped with an
Gao, Shou-Ting; Ping, Fan; Li, Xiao-Fan; Tao, Wei-Kuo
2004-01-01
Although dry/moist potential vorticity is a useful physical quantity for meteorological analysis, it cannot be applied to the analysis of 2D simulations. A convective vorticity vector (CVV) is introduced in this study to analyze 2D cloud-resolving simulation data associated with 2D tropical convection. The cloud model is forced by the vertical velocity, zonal wind, horizontal advection, and sea surface temperature obtained from the TOGA COARE, and is integrated for a selected 10-day period. The CVV has zonal and vertical components in the 2D x-z frame. Analysis of zonally-averaged and mass-integrated quantities shows that the correlation coefficient between the vertical component of the CVV and the sum of the cloud hydrometeor mixing ratios is 0.81, whereas the correlation coefficient between the zonal component and the sum of the mixing ratios is only 0.18. This indicates that the vertical component of the CVV is closely associated with tropical convection. The tendency equation for the vertical component of the CVV is derived and the zonally-averaged and mass-integrated tendency budgets are analyzed. The tendency of the vertical component of the CVV is determined by the interaction between the vorticity and the zonal gradient of cloud heating. The results demonstrate that the vertical component of the CVV is a cloud-linked parameter and can be used to study tropical convection.
Parameterising root system growth models using 2D neutron radiography images
Schnepf, Andrea; Felderer, Bernd; Vontobel, Peter; Leitner, Daniel
2013-04-01
Root architecture is a key factor for plant acquisition of water and nutrients from soil. In particular in view of a second green revolution where the below ground parts of agricultural crops are important, it is essential to characterise and quantify root architecture and its effect on plant resource acquisition. Mathematical models can help to understand the processes occurring in the soil-plant system, they can be used to quantify the effect of root and rhizosphere traits on resource acquisition and the response to environmental conditions. In order to do so, root architectural models are coupled with a model of water and solute transport in soil. However, dynamic root architectural models are difficult to parameterise. Novel imaging techniques such as x-ray computed tomography, neutron radiography and magnetic resonance imaging enable the in situ visualisation of plant root systems. Therefore, these images facilitate the parameterisation of dynamic root architecture models. These imaging techniques are capable of producing 3D or 2D images. Moreover, 2D images are also available in the form of hand drawings or from images of standard cameras. While full 3D imaging tools are still limited in resolutions, 2D techniques are a more accurate and less expensive option for observing roots in their environment. However, analysis of 2D images has additional difficulties compared to the 3D case, because of overlapping roots. We present a novel algorithm for the parameterisation of root system growth models based on 2D images of root system. The algorithm analyses dynamic image data. These are a series of 2D images of the root system at different points in time. Image data has already been adjusted for missing links and artefacts and segmentation was performed by applying a matched filter response. From this time series of binary 2D images, we parameterise the dynamic root architecture model in the following way: First, a morphological skeleton is derived from the binary
Characteristic polynomial assignment in F-M model Ⅱ of 2-D systems
Institute of Scientific and Technical Information of China (English)
唐万生; 亢京力
2004-01-01
The problems of characteristic polynomial assignment in Fornasini-Marchesini (F-M) model Ⅱ of 2-D systems are investigated. The corresponding closed-loop systems described by F-M model Ⅱ are obtained via the state feedback.Using the algebraic geometry method, the characteristic polynomial assignment in the closed-loop systems is discussed. In terms of the theory of algebraic geometry, the problem of characteristic polynomial assignment is transferred to the one whether a rational mapping is onto. Sufficient conditions for almost arbitrary assignment coefficients of characteristic polynomial in F-M model Ⅱ of 2-D systems via state feedback are derived, and they are available for multi-input cases. It also has been shown that this method can be applied to assign the characteristic polynomial with output feedback. The sufficient conditions for almost arbitrary assignment coefficients of characteristic polynomial of multi-input 2-D systems described by F-M model Ⅱ with output feedback are established.
Laser irradiated fluorescent perfluorocarbon microparticles in 2-D and 3-D breast cancer cell models
Niu, Chengcheng; Wang, Long; Wang, Zhigang; Xu, Yan; Hu, Yihe; Peng, Qinghai
2017-03-01
Perfluorocarbon (PFC) droplets were studied as new generation ultrasound contrast agents via acoustic or optical droplet vaporization (ADV or ODV). Little is known about the ODV irradiated vaporization mechanisms of PFC-microparticle complexs and the stability of the new bubbles produced. In this study, fluorescent perfluorohexane (PFH) poly(lactic-co-glycolic acid) (PLGA) particles were used as a model to study the process of particle vaporization and bubble stability following excitation in two-dimensional (2-D) and three-dimensional (3-D) cell models. We observed localization of the fluorescent agent on the microparticle coating material initially and after vaporization under fluorescence microscopy. Furthermore, the stability and growth dynamics of the newly created bubbles were observed for 11 min following vaporization. The particles were co-cultured with 2-D cells to form 3-D spheroids and could be vaporized even when encapsulated within the spheroids via laser irradiation, which provides an effective basis for further work.
A Neural-FEM tool for the 2-D magnetic hysteresis modeling
Energy Technology Data Exchange (ETDEWEB)
Cardelli, E. [University of Perugia, Department of Engineering, Via G. Duranti 93, 06125 Perugia (Italy); Faba, A., E-mail: antonio.faba@unipg.it [University of Perugia, Department of Engineering, Via G. Duranti 93, 06125 Perugia (Italy); Laudani, A.; Lozito, G.M.; Riganti Fulginei, F.; Salvini, A. [Department of Engineering, Roma Tre University, Via V. Volterra 62, 00146 Rome (Italy)
2016-04-01
The aim of this work is to present a new tool for the analysis of magnetic field problems considering 2-D magnetic hysteresis. In particular, this tool makes use of the Finite Element Method to solve the magnetic field problem in real device, and fruitfully exploits a neural network (NN) for the modeling of 2-D magnetic hysteresis of materials. The NS has as input the magnetic inductions components B at the k-th simulation step and returns as output the corresponding values of the magnetic field H corresponding to the input pattern. It is trained by vector measurements performed on the magnetic material to be modeled. This input/output scheme is directly implemented in a FEM code employing the magnetic potential vector A formulation. Validations through measurements on a real device have been performed.
Hybrid 2D-3D modelling of GTA welding with filler wire addition
Traidia, Abderrazak
2012-07-01
A hybrid 2D-3D model for the numerical simulation of Gas Tungsten Arc welding is proposed in this paper. It offers the possibility to predict the temperature field as well as the shape of the solidified weld joint for different operating parameters, with relatively good accuracy and reasonable computational cost. Also, an original approach to simulate the effect of immersing a cold filler wire in the weld pool is presented. The simulation results reveal two important observations. First, the weld pool depth is locally decreased in the presence of filler metal, which is due to the energy absorption by the cold feeding wire from the hot molten pool. In addition, the weld shape, maximum temperature and thermal cycles in the workpiece are relatively well predicted even when a 2D model for the arc plasma region is used. © 2012 Elsevier Ltd. All rights reserved.
2D edge plasma modeling extended up to the main chamber
Energy Technology Data Exchange (ETDEWEB)
Dekeyser, W., E-mail: wouter.dekeyser@mech.kuleuven.be [Department of Mechanical Engineering, Katholieke Universiteit Leuven, Celestijnenlaan 300A, 3001 Leuven (Belgium); Baelmans, M. [Department of Mechanical Engineering, Katholieke Universiteit Leuven, Celestijnenlaan 300A, 3001 Leuven (Belgium); Reiter, D.; Boerner, P.; Kotov, V. [Institut fuer Plasmaphysik, Forschungszentrum Juelich GmbH, EURATOM-Association, Trilateral Euregio Cluster, D-52425 Juelich (Germany)
2011-08-01
Far SOL plasma flow, and hence main chamber recycling and plasma surface interaction, are today still only very poorly described by current 2D fluid edge codes, such as B2, UEDGE or EDGE2D, due to a common technical limitation. We have extended the B2 plasma fluid solver in the current ITER version of B2-EIRENE (SOLPS4.3) to allow plasma solutions to be obtained up to the 'real vessel wall', at least on the basis of ad hoc far SOL transport models. We apply here the kinetic Monte Carlo Code EIRENE on such plasma solutions to study effects of this model refinement on main chamber fluxes and sputtering, for an ITER configuration. We show that main chamber sputtering may be significantly modified both due to thermalization of CX neutrals in the far SOL and poloidally highly asymmetric plasma wall contact, as compared to hitherto applied teleportation of particle fluxes across this domain.
Snapshot Observation for 2D Classical Lattice Models by Corner Transfer Matrix Renormalization Group
Ueda, K.; Otani, R.; Nishio, Y; Gendiar, A.; Nishino, T
2004-01-01
We report a way of obtaining a spin configuration snapshot, which is one of the representative spin configurations in canonical ensemble, in a finite area of infinite size two-dimensional (2D) classical lattice models. The corner transfer matrix renormalization group (CTMRG), a variant of the density matrix renormalization group (DMRG), is used for the numerical calculation. The matrix product structure of the variational state in CTMRG makes it possible to stochastically fix spins each by ea...
Anisotropy effects and friction maps in the framework of the 2d PT model
Energy Technology Data Exchange (ETDEWEB)
Fajardo, O.Y. [Instituto de Ciencia de Materiales de Aragón and Departamento de Física de la Materia Condensada, CSIC-Universidad de Zaragoza, E-50009 Zaragoza (Spain); Gnecco, E. [Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, 28049 Madrid (Spain); Mazo, J.J., E-mail: juanjo@unizar.es [Instituto de Ciencia de Materiales de Aragón and Departamento de Física de la Materia Condensada, CSIC-Universidad de Zaragoza, E-50009 Zaragoza (Spain)
2014-12-15
We present a series of numerical simulations on the friction–anisotropy behavior and stick–slip dynamics of a point mass in the framework of a 2d Prandtl–Tomlinson model. Results for three representative surface lattice are shown: square, hexagonal and honeycomb. Curves for scan angle dependence of static friction force, and kinetic one at T=0 K and T=300 K are shown. Friction force maps are computed at different directions.
Critical slowing down of cluster algorithms for Ising models coupled to 2-d gravity
Bowick, Mark; Falcioni, Marco; Harris, Geoffrey; Marinari, Enzo
1994-02-01
We simulate single and multiple Ising models coupled to 2-d gravity using both the Swendsen-Wang and Wolff algorithms to update the spins. We study the integrated autocorrelation time and find that there is considerable critical slowing down, particularly in the magnetization. We argue that this is primarily due to the local nature of the dynamical triangulation algorithm and to the generation of a distribution of baby universes which inhibits cluster growth.
Critical Slowing Down of Cluster Algorithms for Ising Models Coupled to 2-d Gravity
Bowick, M; Harris, G; Marinari, E
1994-01-01
We simulate single and multiple Ising models coupled to 2-d gravity using both the Swendsen-Wang and Wolff algorithms to update the spins. We study the integrated autocorrelation time and find that there is considerable critical slowing down, particularly in the magnetization. We argue that this is primarily due to the local nature of the dynamical triangulation algorithm and to the generation of a distribution of baby universes which inhibits cluster growth.
Size distribution of islands according to 2D growth model with 2 kinds of diffusion atoms
Yamauchi, R; Koyama, M; Sasakura, H; Nakata, Y; Muto, S
2015-01-01
We simulated the growth of 2D islands with 2 kinds of diffusion atoms using the kinetic Monte- Carlo (kMC) method. As a result, we found that the slow atoms tend to create nuclei and determine the island volume distribution, along with additional properties such as island density. We also conducted a theoretical analysis using the rate equation of the point-island model to confirm these results.
Optimizing the transverse thermal conductivity of 2D-SiCf/SiC composites, I. Modeling
Energy Technology Data Exchange (ETDEWEB)
Youngblood, Gerald E.; Senor, David J.; Jones, Russell H.
2002-12-31
For potential fusion applications, considerable fabrication efforts have been directed to obtaining transverse thermal conductivity (Keff) values in excess of 30 W/mK (unirradiated) in the 800-1000°C temperature range for 2D-SiCf/SiC composites. To gain insight into the factors affecting Keff, at PNNL we have tested three different analytic models for predicting Keff in terms of constituent (fiber, matrix and interphase) properties. The tested models were: the Hasselman-Johnson (H-J) “2-Cylinder” model, which examines the effects of fiber-matrix (f/m) thermal barriers; the Markworth “3-Cylinder” model, which specifically examines the effects of interphase thickness and thermal conductivity; and a newly-developed Anisotropic “3-Square” model, which examines the potential effect of introducing a fiber coating with anisotropic properties to enhance (or diminish) f/m thermal coupling. The first two models are effective medium models, while the third model is a simple combination of parallel and series conductances. Model predictions suggest specific designs and/or development efforts directed to optimize the overall thermal transport performance of 2D-SiCf/SiC.
A simple 2-D inundation model for incorporating flood damage in urban drainage planning
Directory of Open Access Journals (Sweden)
A. Pathirana
2008-11-01
Full Text Available In this paper a new inundation model code is developed and coupled with Storm Water Management Model, SWMM, to relate spatial information associated with urban drainage systems as criteria for planning of storm water drainage networks. The prime objective is to achive a model code that is simple and fast enough to be consistently be used in planning stages of urban drainage projects.
The formulation for the two-dimensional (2-D surface flow model algorithms is based on the Navier Stokes equation in two dimensions. An Alternating Direction Implicit (ADI finite difference numerical scheme is applied to solve the governing equations. This numerical scheme is used to express the partial differential equations with time steps split into two halves. The model algorithm is written using C++ computer programming language.
This 2-D surface flow model is then coupled with SWMM for simulation of both pipe flow component and surcharge induced inundation in urban areas. In addition, a damage calculation block is integrated within the inundation model code.
The coupled model is shown to be capable of dealing with various flow conditions, as well as being able to simulate wetting and drying processes that will occur as the flood flows over an urban area. It has been applied under idealized and semi-hypothetical cases to determine detailed inundation zones, depths and velocities due to surcharged water on overland surface.
Nested 1D-2D approach for urban surface flood modeling
Murla, Damian; Willems, Patrick
2015-04-01
Floods in urban areas as a consequence of sewer capacity exceedance receive increased attention because of trends in urbanization (increased population density and impermeability of the surface) and climate change. Despite the strong recent developments in numerical modeling of water systems, urban surface flood modeling is still a major challenge. Whereas very advanced and accurate flood modeling systems are in place and operation by many river authorities in support of flood management along rivers, this is not yet the case in urban water management. Reasons include the small scale of the urban inundation processes, the need to have very high resolution topographical information available, and the huge computational demands. Urban drainage related inundation modeling requires a 1D full hydrodynamic model of the sewer network to be coupled with a 2D surface flood model. To reduce the computational times, 0D (flood cones), 1D/quasi-2D surface flood modeling approaches have been developed and applied in some case studies. In this research, a nested 1D/2D hydraulic model has been developed for an urban catchment at the city of Gent (Belgium), linking the underground sewer (minor system) with the overland surface (major system). For the overland surface flood modelling, comparison was made of 0D, 1D/quasi-2D and full 2D approaches. The approaches are advanced by considering nested 1D-2D approaches, including infiltration in the green city areas, and allowing the effects of surface storm water storage to be simulated. An optimal nested combination of three different mesh resolutions was identified; based on a compromise between precision and simulation time for further real-time flood forecasting, warning and control applications. Main streets as mesh zones together with buildings as void regions constitute one of these mesh resolution (3.75m2 - 15m2); they have been included since they channel most of the flood water from the manholes and they improve the accuracy of
Brane Brick Models, Toric Calabi-Yau 4-Folds and 2d (0,2) Quivers
Franco, Sebastian; Seong, Rak-Kyeong
2015-01-01
We introduce brane brick models, a novel type of Type IIA brane configurations consisting of D4-branes ending on an NS5-brane. Brane brick models are T-dual to D1-branes over singular toric Calabi-Yau 4-folds. They fully encode the infinite class of 2d (generically) N=(0,2) gauge theories on the worldvolume of the D1-branes and streamline their connection to the probed geometries. For this purpose, we also introduce new combinatorial procedures for deriving the Calabi-Yau associated to a given gauge theory and vice versa.
Uncertainties in modelling Mt. Pinatubo eruption with 2-D AER model and CCM SOCOL
Kenzelmann, P.; Weisenstein, D.; Peter, T.; Luo, B. P.; Rozanov, E.; Fueglistaler, S.; Thomason, L. W.
2009-04-01
Large volcanic eruptions may introduce a strong forcing on climate. They challenge the skills of climate models. In addition to the short time attenuation of solar light by ashes the formation of stratospheric sulphate aerosols, due to volcanic sulphur dioxide injection into the lower stratosphere, may lead to a significant enhancement of the global albedo. The sulphate aerosols have a residence time of about 2 years. As a consequence of the enhanced sulphate aerosol concentration both the stratospheric chemistry and dynamics are strongly affected. Due to absorption of longwave and near infrared radiation the temperature in the lower stratosphere increases. So far chemistry climate models overestimate this warming [Eyring et al. 2006]. We present an extensive validation of extinction measurements and model runs of the eruption of Mt. Pinatubo in 1991. Even if Mt. Pinatubo eruption has been the best quantified volcanic eruption of this magnitude, the measurements show considerable uncertainties. For instance the total amount of sulphur emitted to the stratosphere ranges from 5-12 Mt sulphur [e.g. Guo et al. 2004, McCormick, 1992]. The largest uncertainties are in the specification of the main aerosol cloud. SAGE II, for instance, could not measure the peak of the aerosol extinction for about 1.5 years, because optical termination was reached. The gap-filling of the SAGE II [Thomason and Peter, 2006] using lidar measurements underestimates the total extinctions in the tropics for the first half year after the eruption by 30% compared to AVHRR [Rusell et. al 1992]. The same applies to the optical dataset described by Stenchikov et al. [1998]. We compare these extinction data derived from measurements with extinctions derived from AER 2D aerosol model calculations [Weisenstein et al., 2007]. Full microphysical calculations with injections of 14, 17, 20 and 26 Mt SO2 in the lower stratosphere were performed. The optical aerosol properties derived from SAGE II
A New Approach to Calculate Indirect GWPs using the UIUC 2-D CRT and RTM Model
Li, Y.; Youn, D.; Patten, K.; Wuebbles, D.
2006-12-01
Global warming potentials (GWPs) are defined to be the total impact over time of adding a unit mass of a greenhouse gas to the atmosphere. Indirect GWPs are due to ozone depletion effects in the stratosphere for a certain compound and therefore stand for the long-term global cooling effects. Previously, indirect GWPs were calculated using a box model, which was not able to consider the complex processes in the atmosphere. As a step towards obtaining indirect GWPs through a more robust approach, the UIUC 2-D CRT model was used as the computational tool to derive ozone changes. The 2-D model has more realistic chemical, physical, and dynamical processes in the atmosphere and a relatively complete transport system, which makes it useful for a more accurate analysis. Furthermore, the University of Illinois at Urbana-Champaign (UIUC) radiative transfer model (RTM) is employed to derive the corresponding time-dependent radiative forcings from the 2-D CRT outputs. Two Halon compounds, Halon-1211 and Halon-1301, were selected to be studied for their indirect GWPs. The results showed that instantaneous and stratospheric adjusted indirect GWPs for a 100-year horizon are -10004.8 and -10237.1 for Halon-1211, while for Halon-1301 they are -19218.0 and -19627.6. The indirect GWPs for Halon-1211 and -1301 presented here are two to three times smaller compared to the results in WMO (2006) draft. Further analysis on indirect GWPs will be carried out using our 3-D MOZART-3 model.
2D-3D Registration of CT Vertebra Volume to Fluoroscopy Projection: A Calibration Model Assessment
Directory of Open Access Journals (Sweden)
Allen R
2010-01-01
Full Text Available This study extends a previous research concerning intervertebral motion registration by means of 2D dynamic fluoroscopy to obtain a more comprehensive 3D description of vertebral kinematics. The problem of estimating the 3D rigid pose of a CT volume of a vertebra from its 2D X-ray fluoroscopy projection is addressed. 2D-3D registration is obtained maximising a measure of similarity between Digitally Reconstructed Radiographs (obtained from the CT volume and real fluoroscopic projection. X-ray energy correction was performed. To assess the method a calibration model was realised a sheep dry vertebra was rigidly fixed to a frame of reference including metallic markers. Accurate measurement of 3D orientation was obtained via single-camera calibration of the markers and held as true 3D vertebra position; then, vertebra 3D pose was estimated and results compared. Error analysis revealed accuracy of the order of 0.1 degree for the rotation angles of about 1 mm for displacements parallel to the fluoroscopic plane, and of order of 10 mm for the orthogonal displacement.
75 FR 3127 - Airworthiness Directives; Thrush Aircraft, Inc. Model 600 S2D and S2R Series Airplanes
2010-01-20
... wing front lower spar caps in Thrush Aircraft, Inc. Model 600 S2D and S2R (S-2R) series airplanes (type..., which applies to Thrush Aircraft, Inc. Model 600 S2D and S2R (S-2R) series airplanes (type certificate... Environmental Conditions Avenger Aircraft and Services (Avenger) states the life limits for the wing front...
A solidification constitutive model for NIKE2D and NIKE3D
Energy Technology Data Exchange (ETDEWEB)
Raboin, P.J.
1994-03-17
This memo updates the current status of a solidification material model development which has been underway for more than a year. Significant modeling goals such as predicting cut-off stresses, thermo-elasto-plasticity, strain rate dependent plasticity and dynamic recovery have been completed. The model is called SOLMAT for solidification material model, and while developed for NIKE2D, it has already been implemented in NIKE3D and NIT03D by B. Maker. This memo details the future development strategy of SOLMAT including liquid and solid constitutive improvements, coupling of deviatoric and dilatational deformation and a plan to switch between constitutive theories. It explains some of the difficulties associated solidification modeling and proposes two experiments to measure properties for using SOLMAT. Due to the sensitive nature of these plans in relation to programmatic and CRADA concerns, this memo should be treated as confidential document.
2D cellular automaton model for the evolution of active region coronal plasmas
Fuentes, Marcelo López
2016-01-01
We study a 2D cellular automaton (CA) model for the evolution of coronal loop plasmas. The model is based on the idea that coronal loops are made of elementary magnetic strands that are tangled and stressed by the displacement of their footpoints by photospheric motions. The magnetic stress accumulated between neighbor strands is released in sudden reconnection events or nanoflares that heat the plasma. We combine the CA model with the Enthalpy Based Thermal Evolution of Loops (EBTEL) model to compute the response of the plasma to the heating events. Using the known response of the XRT telescope on board Hinode we also obtain synthetic data. The model obeys easy to understand scaling laws relating the output (nanoflare energy, temperature, density, intensity) to the input parameters (field strength, strand length, critical misalignment angle). The nanoflares have a power-law distribution with a universal slope of -2.5, independent of the input parameters. The repetition frequency of nanoflares, expressed in t...
Quenched bond randomness in marginal and non-marginal Ising spin models in 2D
Fytas, N. G.; Malakis, A.; Hadjiagapiou, I. A.
2008-11-01
We investigate and contrast, via entropic sampling based on the Wang-Landau algorithm, the effects of quenched bond randomness on the critical behavior of two Ising spin models in 2D. The random bond version of the superantiferromagnetic (SAF) square model with nearest- and next-nearest-neighbor competing interactions and the corresponding version of the simple Ising model are studied, and their general universality aspects are inspected by means of a detailed finite size scaling (FSS) analysis. We find that the random bond SAF model obeys weak universality, hyperscaling, and exhibits a strong saturating behavior of the specific heat due to the competing nature of interactions. On the other hand, for the random Ising model we encounter some difficulties as regards a definite discrimination between the two well-known scenarios of the logarithmic corrections versus the weak universality. However, a careful FSS analysis of our data favors the field theoretically predicted logarithmic corrections.
2D lattice model of a lipid bilayer: Microscopic derivation and thermodynamic exploration
Hakobyan, Davit; Heuer, Andreas
2017-02-01
Based on all-atom Molecular Dynamics (MD) simulations of a lipid bilayer we present a systematic mapping on a 2D lattice model. Keeping the lipid type and the chain order parameter as key variables we derive a free energy functional, containing the enthalpic interaction of adjacent lipids as well as the tail entropy. The functional form of both functions is explicitly determined for saturated and polyunsaturated lipids. By studying the lattice model via Monte Carlo simulations it is possible to reproduce the temperature dependence of the distribution of order parameters of the pure lipids, including the prediction of the gel transition. Furthermore, application to a mixture of saturated and polyunsaturated lipids yields the correct phase separation behavior at lower temperatures with a simulation time reduced by approximately 7 orders of magnitude as compared to the corresponding MD simulations. Even the time-dependence of the de-mixing is reproduced on a semi-quantitative level. Due to the generality of the approach we envisage a large number of further applications, ranging from modeling larger sets of lipids, sterols, and solvent proteins to predicting nucleation barriers for the melting of lipids. Particularly, from the properties of the 2D lattice model one can directly read off the enthalpy and entropy change of the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine gel-to-liquid transition in excellent agreement with experimental and MD results.
Mendoza-Torres, F.; Diaz-Viera, M. A.
2015-12-01
In many natural fractured porous media, such as aquifers, soils, oil and geothermal reservoirs, fractures play a crucial role in their flow and transport properties. An approach that has recently gained popularity for modeling fracture systems is the Discrete Fracture Network (DFN) model. This approach consists in applying a stochastic boolean simulation method, also known as object simulation method, where fractures are represented as simplified geometric objects (line segments in 2D and polygons in 3D). One of the shortcomings of this approach is that it usually does not consider the dependency relationships that may exist between the geometric properties of fractures (direction, length, aperture, etc), that is, each property is simulated independently. In this work a method for modeling such dependencies by copula theory is introduced. In particular, a nonparametric model using Bernstein copulas for direction-length fracture dependency in 2D is presented. The application of this method is illustrated in a case study for a fractured rock sample from a carbonate reservoir outcrop.
Institute of Scientific and Technical Information of China (English)
罗孟波; 陈庆虎; 焦正宽
2002-01-01
We investigate the influence of the boundary condition on the short-time dynamic behaviour of the Ising-like phase transition in square-lattice fully frustrated (FF) XY models with periodic and fluctuating twist boundary conditions. The transition temperature Tc and the dynamic and static critical exponents z, 2β/v and v are estimated for both cases using short-time dynamic scaling analysis. The results show that both models have the same critical exponents, indicating that the boundary condition has nearly no effect on the short-time dynamic behaviour of the FFXY model.
Boundary field induced first-order transition in the 2D Ising model: exact study
Energy Technology Data Exchange (ETDEWEB)
Clusel, Maxime [Institut Laue-Langevin, 6 rue Horowitz BP156 X, 38042 Grenoble Cedex (France); Fortin, Jean-Yves [Laboratoire Poncelet, 119002, Bolshoy Vlasyevskiy Pereulok 11, Moscow (Russian Federation)
2006-02-03
We present in this paper an exact study of a first-order transition induced by an inhomogeneous boundary magnetic field in the 2D Ising model. From a previous analysis of the interfacial free energy in the discrete case (Clusel and Fortin 2005 J. Phys. A: Math. Gen. 38 2849) we identify, using an asymptotic expansion in the thermodynamic limit, the line of transition that separates the regime where the interface is localized near the boundary from the one where it is propagating inside the bulk. In particular, the transition line has a strong dependence on the aspect ratio of the lattice.
Transport Properties near Quantum Critical Point in 2D Hubbard Model
Chen, Kuang-Shing; Pathak, Sandeep; Yang, Shuxiang; Su, Shi-Quan; Galanakis, Dimitris; Mikelsons, Karlis; Moreno, Juana; Jarrell, Mark
2011-03-01
We obtain high quality estimates of the self energy Σ (K , ω) by direct analytic continuation of Σ (K , iωn) obtained from Continuous-Time Quantum Monte Carlo. We use these results to investigate the transport properties near the quantum critical point found in the 2D Hubbard model at finite doping. Resistivity, thermal conductivity, Wiedemann-Franz Law, and thermopower are examined in the Fermi liquid, Marginal Fermi liquid (MFL), and pseudo-gap regions. Σ (k , ω) with k along the nodal direction displays temperature-dependent scaling similar to that seen in the experiment. A next-nearest neighbor hopping tOISE-0730290.
On the origin of quantum criticality found at finite doping in 2D Hubbard model
Yang, Shuxiang; Fotso, Herbert; Moreno, Juana; Jarrell, Mark
2011-03-01
To better understand the excitations responsible for quantum criticality (QC) found at finite doping in the 2D Hubbard model, we analyze the vertices for different scattering channels obtained from the Dynamical Cluster Continuous-Time Quantum Monte Carlo simulation. By decomposing these vertices using the parquet equations we find that both superconductivity and the charge instabilities responsible for the QC come from the crossed spin channel contribution, and thus are driven by the spin-fluctuations. On contrast, the spin instability comes from the fully irreducible spin vertex contribution. We acknowledge the support from NSF OISE-0730290 and DOE SciDAC DE-FC02-06ER25792.
2D-HIDDEN MARKOV MODEL FEATURE EXTRACTION STRATEGY OF ROTATING MACHINERY FAULT DIAGNOSIS
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
A new feature extraction method based on 2D-hidden Markov model(HMM) is proposed.Meanwhile the time index and frequency index are introduced to represent the new features. The new feature extraction strategy is tested by the experimental data that collected from Bently rotor experiment system. The results show that this methodology is very effective to extract the feature of vibration signals in the rotor speed-up course and can be extended to other non-stationary signal analysis fields in the future.
JetCurry: Modeling 3D geometry of AGN jets from 2D images
Kosak, Katie; Li, KunYang; Avachat, Sayali S.; Perlman, Eric S.
2017-02-01
Written in Python, JetCurry models the 3D geometry of jets from 2-D images. JetCurry requires NumPy and SciPy and incorporates emcee (ascl:1303.002) and AstroPy (ascl:1304.002), and optionally uses VPython. From a defined initial part of the jet that serves as a reference point, JetCurry finds the position of highest flux within a bin of data in the image matrix and fits along the x axis for the general location of the bends in the jet. A spline fitting is used to smooth out the resulted jet stream.
Entanglement entropy through conformal interfaces in the 2D Ising model
Brehm, Enrico M
2015-01-01
We consider the entanglement entropy for the 2D Ising model at the conformal fixed point in the presence of interfaces. More precisely, we investigate the situation where the two subsystems are separated by a defect line that preserves conformal invariance. Using the replica trick, we compute the entanglement entropy between the two subsystems. We observe that the entropy, just like in the case without defects, shows a logarithmic scaling behavior with respect to the size of the system. Here, the prefactor of the logarithm depends on the strength of the defect encoded in the transmission coefficient. We also commend on the supersymmetric case.
A 2D Axisymmetric Mixture Multiphase Model for Bottom Stirring in a BOF Converter
Kruskopf, Ari
2017-02-01
A process model for basic oxygen furnace (BOF) steel converter is in development. The model will take into account all the essential physical and chemical phenomena, while achieving real-time calculation of the process. The complete model will include a 2D axisymmetric turbulent multiphase flow model for iron melt and argon gas mixture, a steel scrap melting model, and a chemical reaction model. A novel liquid mass conserving mixture multiphase model for bubbling gas jet is introduced in this paper. In-house implementation of the model is tested and validated in this article independently from the other parts of the full process model. Validation data comprise three different water models with different volume flow rates of air blown through a regular nozzle and a porous plug. The water models cover a wide range of dimensionless number R_{{p}} , which include values that are similar for industrial-scale steel converter. The k- ɛ turbulence model is used with wall functions so that a coarse grid can be utilized. The model calculates a steady-state flow field for gas/liquid mixture using control volume method with staggered SIMPLE algorithm.
A 2D Axisymmetric Mixture Multiphase Model for Bottom Stirring in a BOF Converter
Kruskopf, Ari
2016-11-01
A process model for basic oxygen furnace (BOF) steel converter is in development. The model will take into account all the essential physical and chemical phenomena, while achieving real-time calculation of the process. The complete model will include a 2D axisymmetric turbulent multiphase flow model for iron melt and argon gas mixture, a steel scrap melting model, and a chemical reaction model. A novel liquid mass conserving mixture multiphase model for bubbling gas jet is introduced in this paper. In-house implementation of the model is tested and validated in this article independently from the other parts of the full process model. Validation data comprise three different water models with different volume flow rates of air blown through a regular nozzle and a porous plug. The water models cover a wide range of dimensionless number R_{p} , which include values that are similar for industrial-scale steel converter. The k-ɛ turbulence model is used with wall functions so that a coarse grid can be utilized. The model calculates a steady-state flow field for gas/liquid mixture using control volume method with staggered SIMPLE algorithm.
Modeling of lamps through a diffuser with 2D and 3D picket-fence backlight models
Belshaw, Richard J.; Wilmott, Roger; Thomas, John T.
2002-08-01
Laboratory photometric measurements are taken of a display backlight one metre away from the emission surface (diffuser) with a whole acceptance angle on the photometer of about 0.125 degrees (2.182mm spot size at emission surface). A simulation method was sought to be able to obtain the brightness uniformity (luminance peak to trough ratio from above one lamp to the null between lamps in a picket-fence backlight). A 3D raytrace BackLight model in TracePro and a 2D Mathematical model in Matlab have been developed. With a specimen backlight in the laboratory, a smooth luminance profile was measured by the photometer on the diffuser surface. Ray Trace models in both 3D and 2D take too long to produce smooth 'continuous filled' distributions. The Mathematical 2D approach, although with limitations, yielded smooth solutions in a very reasonable time frame.
Image restoration using 2D autoregressive texture model and structure curve construction
Voronin, V. V.; Marchuk, V. I.; Petrosov, S. P.; Svirin, I.; Agaian, S.; Egiazarian, K.
2015-05-01
In this paper an image inpainting approach based on the construction of a composite curve for the restoration of the edges of objects in an image using the concepts of parametric and geometric continuity is presented. It is shown that this approach allows to restore the curved edges and provide more flexibility for curve design in damaged image by interpolating the boundaries of objects by cubic splines. After edge restoration stage, a texture restoration using 2D autoregressive texture model is carried out. The image intensity is locally modeled by a first spatial autoregressive model with support in a strongly causal prediction region on the plane. Model parameters are estimated by Yule-Walker method. Several examples considered in this paper show the effectiveness of the proposed approach for large objects removal as well as recovery of small regions on several test images.
Improving object detection in 2D images using a 3D world model
Viggh, Herbert E. M.; Cho, Peter L.; Armstrong-Crews, Nicholas; Nam, Myra; Shah, Danelle C.; Brown, Geoffrey E.
2014-05-01
A mobile robot operating in a netcentric environment can utilize offboard resources on the network to improve its local perception. One such offboard resource is a world model built and maintained by other sensor systems. In this paper we present results from research into improving the performance of Deformable Parts Model object detection algorithms by using an offboard 3D world model. Experiments were run for detecting both people and cars in 2D photographs taken in an urban environment. After generating candidate object detections, a 3D world model built from airborne Light Detection and Ranging (LIDAR) and aerial photographs was used to filter out false alarm using several types of geometric reasoning. Comparison of the baseline detection performance to the performance after false alarm filtering showed a significant decrease in false alarms for a given probability of detection.
Stochastic dynamics of phase singularities under ventricular fibrillation in 2D Beeler-Reuter model
Suzuki, Akio; Konno, Hidetoshi
2011-09-01
The dynamics of ventricular fibrillation (VF) has been studied extensively, and the initiation mechanism of VF has been elucidated to some extent. However, the stochastic dynamical nature of sustained VF remains unclear so far due to the complexity of high dimensional chaos in a heterogeneous system. In this paper, various statistical mechanical properties of sustained VF are studied numerically in 2D Beeler-Reuter-Drouhard-Roberge (BRDR) model with normal and modified ionic current conductance. The nature of sustained VF is analyzed by measuring various fluctuations of spatial phase singularity (PS) such as velocity, lifetime, the rates of birth and death. It is found that the probability density function (pdf) for lifetime of PSs is independent of system size. It is also found that the hyper-Gamma distribution serves as a universal pdf for the counting number of PSs for various system sizes and various parameters of our model tissue under VF. Further, it is demonstrated that the nonlinear Langevin equation associated with a hyper-Gamma process can mimic the pdf and temporal variation of the number of PSs in the 2D BRDR model.
Yan, Bo; Li, Yuguo; Liu, Ying
2016-07-01
In this paper, we present an adaptive finite element (FE) algorithm for direct current (DC) resistivity modeling in 2-D generally anisotropic conductivity structures. Our algorithm is implemented on an unstructured triangular mesh that readily accommodates complex structures such as topography and dipping layers and so on. We implement a self-adaptive, goal-oriented grid refinement algorithm in which the finite element analysis is performed on a sequence of refined grids. The grid refinement process is guided by an a posteriori error estimator. The problem is formulated in terms of total potentials where mixed boundary conditions are incorporated. This type of boundary condition is superior to the Dirichlet type of conditions and improves numerical accuracy considerably according to model calculations. We have verified the adaptive finite element algorithm using a two-layered earth with azimuthal anisotropy. The FE algorithm with incorporation of mixed boundary conditions achieves high accuracy. The relative error between the numerical and analytical solutions is less than 1% except in the vicinity of the current source location, where the relative error is up to 2.4%. A 2-D anisotropic model is used to demonstrate the effects of anisotropy upon the apparent resistivity in DC soundings.
CFHTLenS: Combined probe cosmological model comparison using 2D weak gravitational lensing
Kilbinger, Martin; Heymans, Catherine; Simpson, Fergus; Benjamin, Jonathan; Erben, Thomas; Harnois-Deraps, Joachim; Hoekstra, Henk; Hildebrandt, Hendrik; Kitching, Thomas D; Mellier, Yannick; Miller, Lance; Van Waerbeke, Ludovic; Benabed, Karim; Bonnett, Christopher; Coupon, Jean; Hudson, Michael J; Kuijken, Konrad; Rowe, Barnaby; Schrabback, Tim; Semboloni, Elisabetta; Vafaei, Sanaz; Velander, Malin
2012-01-01
We present cosmological constraints from 2D weak gravitational lensing by the large-scale structure in the Canada-France Hawaii Telescope Lensing Survey (CFHTLenS) which spans 154 square degrees in five optical bands. Using accurate photometric redshifts and measured shapes for 4.2 million galaxies between redshifts of 0.2 and 1.3, we compute the 2D cosmic shear correlation function over angular scales ranging between 0.8 and 350 arcmin. Using non-linear models of the dark-matter power spectrum, we constrain cosmological parameters by exploring the parameter space with Population Monte Carlo sampling. The best constraints from lensing alone are obtained for the small-scale density-fluctuations amplitude sigma_8 scaled with the total matter density Omega_m. For a flat LambdaCDM model we obtain sigma_8(Omega_m/0.27)^0.6 = 0.79+-0.03. We combine the CFHTLenS data with WMAP7, BOSS and an HST distance-ladder prior on the Hubble constant to get joint constraints. For a flat LambdaCDM model, we find Omega_m = 0.283+...
Stochastic dynamics of phase singularities under ventricular fibrillation in 2D Beeler-Reuter model
Directory of Open Access Journals (Sweden)
Akio Suzuki
2011-09-01
Full Text Available The dynamics of ventricular fibrillation (VF has been studied extensively, and the initiation mechanism of VF has been elucidated to some extent. However, the stochastic dynamical nature of sustained VF remains unclear so far due to the complexity of high dimensional chaos in a heterogeneous system. In this paper, various statistical mechanical properties of sustained VF are studied numerically in 2D Beeler-Reuter-Drouhard-Roberge (BRDR model with normal and modified ionic current conductance. The nature of sustained VF is analyzed by measuring various fluctuations of spatial phase singularity (PS such as velocity, lifetime, the rates of birth and death. It is found that the probability density function (pdf for lifetime of PSs is independent of system size. It is also found that the hyper-Gamma distribution serves as a universal pdf for the counting number of PSs for various system sizes and various parameters of our model tissue under VF. Further, it is demonstrated that the nonlinear Langevin equation associated with a hyper-Gamma process can mimic the pdf and temporal variation of the number of PSs in the 2D BRDR model.
Self-Organization in 2D Traffic Flow Model with Jam-Avoiding Drive
Nagatani, Takashi
1995-04-01
A stochastic cellular automaton (CA) model is presented to investigate the traffic jam by self-organization in the two-dimensional (2D) traffic flow. The CA model is the extended version of the 2D asymmetric exclusion model to take into account jam-avoiding drive. Each site contains either a car moving to the up, a car moving to the right, or is empty. A up car can shift right with probability p ja if it is blocked ahead by other cars. It is shown that the three phases (the low-density phase, the intermediate-density phase and the high-density phase) appear in the traffic flow. The intermediate-density phase is characterized by the right moving of up cars. The jamming transition to the high-density jamming phase occurs with higher density of cars than that without jam-avoiding drive. The jamming transition point p 2c increases with the shifting probability p ja. In the deterministic limit of p ja=1, it is found that a new jamming transition occurs from the low-density synchronized-shifting phase to the high-density moving phase with increasing density of cars. In the synchronized-shifting phase, all up cars do not move to the up but shift to the right by synchronizing with the move of right cars. We show that the jam-avoiding drive has an important effect on the dynamical jamming transition.
Quasi 2D hydrodynamic modelling of the flooded hinterland due to dyke breaching on the Elbe River
Directory of Open Access Journals (Sweden)
S. Huang
2007-01-01
Full Text Available In flood modeling, many 1D and 2D combination and 2D models are used to simulate diversion of water from rivers through dyke breaches into the hinterland for extreme flood events. However, these models are too demanding in data requirements and computational resources which is an important consideration when uncertainty analysis using Monte Carlo techniques is used to complement the modeling exercise. The goal of this paper is to show the development of a quasi-2D modeling approach, which still calculates the dynamic wave in 1D but the discretisation of the computational units are in 2D, allowing a better spatial representation of the flow in the hinterland due to dyke breaching without a large additional expenditure on data pre-processing and computational time. A 2D representation of the flow and velocity fields is required to model sediment and micro-pollutant transport. The model DYNHYD (1D hydrodynamics from the WASP5 modeling package was used as a basis for the simulations. The model was extended to incorporate the quasi-2D approach and a Monte-Carlo Analysis was used to conduct a flood sensitivity analysis to determine the sensitivity of parameters and boundary conditions to the resulting water flow. An extreme flood event on the Elbe River, Germany, with a possible dyke breach area was used as a test case. The results show a good similarity with those obtained from another 1D/2D modeling study.
Heerens, W.C.; Laham, C.D.; Holman, A.E.
1997-01-01
An XY-displacement device (1) with a four-fold symmetry comprises a reference frame (10); an object mount (20) for holding an object (22) to be displaced; an X-manipulator (100) coupled between the reference frame (10) and the object mount (20), which provides a rigid coupling between the object mou
Assessing soil fluxes using meteoric 10Be: development and application of the Be2D model
Campforts, Benjamin; Govers, Gerard; Vanacker, Veerle; Baken, Stijn; Smolders, Erik; Vanderborght, Jan
2015-04-01
Meteoric 10Be is a promising and increasingly popular tool to better understand soil fluxes at different timescales. Unlike other, more classical, methods such as the study of sedimentary archives it enables a direct coupling between eroding and deposition sites. However, meteoric 10Be can be mobilized within the soil. Therefore, spatial variations in meteoric 10Be inventories cannot directly be translated into spatial variations in erosion and sedimentation rates: a correct interpretation of measured 10Be inventories requires that both lateral and vertical movement of meteoric 10Be are accounted for. Here, we present a spatially explicit 2D model that allows to simulate the behaviour of meteoric 10Be in the soil system over timescales of up to 1 million year and use the model to investigate the impact of accelerated erosion on meteoric 10Be inventories. The model consists of two parts. A first component deals with advective and diffusive mobility within the soil profile, whereas a second component describes lateral soil (and meteoric 10Be) fluxes over the hillslope. Soil depth is calculated dynamically, accounting for soil production through weathering and lateral soil fluxes. Different types of erosion such as creep, water and tillage erosion are supported. Model runs show that natural soil fluxes can be well reconstructed based on meteoric 10Be inventories, and this for a wide range of geomorphological and pedological conditions. However, extracting signals of human impact and distinguishing them from natural soil fluxes is only feasible when the soil has a rather high retention capacity so that meteoric 10Be is retained in the top soil layer. Application of the Be2D model to an existing data set in the Appalachian Mountains [West et al.,2013] using realistic parameter values for the soil retention capacity as well as for vertical advection resulted in a good agreement between simulated and observed 10Be inventories. This confirms the robustness of the model. We
Well-posedness and generalized plane waves simulations of a 2D mode conversion model
Imbert-Gérard, Lise-Marie
2015-01-01
Certain types of electro-magnetic waves propagating in a plasma can undergo a mode conversion process. In magnetic confinement fusion, this phenomenon is very useful to heat the plasma, since it permits to transfer the heat at or near the plasma center. This work focuses on a mathematical model of wave propagation around the mode conversion region, from both theoretical and numerical points of view. It aims at developing, for a well-posed equation, specific basis functions to study a wave mode conversion process. These basis functions, called generalized plane waves, are intrinsically based on variable coefficients. As such, they are particularly adapted to the mode conversion problem. The design of generalized plane waves for the proposed model is described in detail. Their implementation within a discontinuous Galerkin method then provides numerical simulations of the process. These first 2D simulations for this model agree with qualitative aspects studied in previous works.
Observation of spatial charge and spin correlations in the 2D Fermi-Hubbard model.
Cheuk, Lawrence W; Nichols, Matthew A; Lawrence, Katherine R; Okan, Melih; Zhang, Hao; Khatami, Ehsan; Trivedi, Nandini; Paiva, Thereza; Rigol, Marcos; Zwierlein, Martin W
2016-09-16
Strong electron correlations lie at the origin of high-temperature superconductivity. Its essence is believed to be captured by the Fermi-Hubbard model of repulsively interacting fermions on a lattice. Here we report on the site-resolved observation of charge and spin correlations in the two-dimensional (2D) Fermi-Hubbard model realized with ultracold atoms. Antiferromagnetic spin correlations are maximal at half-filling and weaken monotonically upon doping. At large doping, nearest-neighbor correlations between singly charged sites are negative, revealing the formation of a correlation hole, the suppressed probability of finding two fermions near each other. As the doping is reduced, the correlations become positive, signaling strong bunching of doublons and holes, in agreement with numerical calculations. The dynamics of the doublon-hole correlations should play an important role for transport in the Fermi-Hubbard model.
A coupled $2\\times2$D Babcock-Leighton solar dynamo model. II. Reference dynamo solutions
Lemerle, Alexandre
2016-01-01
In this paper we complete the presentation of a new hybrid $2\\times2$D flux transport dynamo (FTD) model of the solar cycle based on the Babcock-Leighton mechanism of poloidal magnetic field regeneration via the surface decay of bipolar magnetic regions (BMRs). This hybrid model is constructed by allowing the surface flux transport (SFT) simulation described in Lemerle et al. 2015 to provide the poloidal source term to an axisymmetric FTD simulation defined in a meridional plane, which in turn generates the BMRs required by the SFT. A key aspect of this coupling is the definition of an emergence function describing the probability of BMR emergence as a function of the spatial distribution of the internal axisymmetric magnetic field. We use a genetic algorithm to calibrate this function, together with other model parameters, against observed cycle 21 emergence data. We present a reference dynamo solution reproducing many solar cycle characteristics, including good hemispheric coupling, phase relationship betwe...
2-D IMAGE-BASED VOLUMETRIC MODELING FOR PARTICLE OF RANDOM SHAPE
Institute of Scientific and Technical Information of China (English)
Chen Ken; Larry E. Banta; Jiang Gangyi
2006-01-01
In this paper, an approach to predicting randomly-shaped particle volume based on its twoDimensional (2-D) digital image is explored. Conversion of gray-scale image of the particles to its binary counterpart is first performed using backlighting technique. The silhouette of particle is thus obtained, and consequently, informative features such as particle area, centroid and shape-related descriptors are collected. Several dimensionless parameters are defined, and used as regressor variables in a multiple linear regression model to predict particle volume. Regressor coefficients are found by fitting to a randomly selected sample of 501 particles ranging in size from 4.75mm to 25mm. The model testing experiment is conducted against a different aggregate sample of the similar statistical properties, the errors of the model-predicted volume of the batch is within ±2%.
Interchange turbulence model for the edge plasma in SOLEDGE2D-EIRENE
Energy Technology Data Exchange (ETDEWEB)
Bufferand, H.; Marandet, Y. [Aix-Marseille Universite, CNRS, PIIM, Marseille (France); Ciraolo, G.; Ghendrih, P.; Bucalossi, J.; Fedorczak, N.; Gunn, J.; Tamain, P. [CEA, IRFM, Saint-Paul-Lez-Durance (France); Colin, C.; Galassi, D.; Leybros, R.; Serre, E. [Aix-Marseille Universite, CNRS, M2P2, Marseille (France)
2016-08-15
Cross-field transport in edge tokamak plasmas is known to be dominated by turbulent transport. A dedicated effort has been made to simulate this turbulent transport from first principle models but the numerical cost to run these simulations on the ITER scale remains prohibitive. Edge plasma transport study relies mostly nowadays on so-called transport codes where the turbulent transport is taken into account using effective ad-hoc diffusion coefficients. In this contribution, we propose to introduce a transport equation for the turbulence intensity in SOLEDGE2D-EIRENE to describe the interchange turbulence properties. Going beyond the empirical diffusive model, this system automatically generates profiles for the turbulent transport and hence reduces the number of degrees of freedom for edge plasma transport codes. We draw inspiration from the k-epsilon model widely used in the neutral fluid community. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Laser irradiated fluorescent perfluorocarbon microparticles in 2-D and 3-D breast cancer cell models
Niu, Chengcheng; Wang, Long; Wang, Zhigang; Xu, Yan; Hu, Yihe; Peng, Qinghai
2017-01-01
Perfluorocarbon (PFC) droplets were studied as new generation ultrasound contrast agents via acoustic or optical droplet vaporization (ADV or ODV). Little is known about the ODV irradiated vaporization mechanisms of PFC-microparticle complexs and the stability of the new bubbles produced. In this study, fluorescent perfluorohexane (PFH) poly(lactic-co-glycolic acid) (PLGA) particles were used as a model to study the process of particle vaporization and bubble stability following excitation in two-dimensional (2-D) and three-dimensional (3-D) cell models. We observed localization of the fluorescent agent on the microparticle coating material initially and after vaporization under fluorescence microscopy. Furthermore, the stability and growth dynamics of the newly created bubbles were observed for 11 min following vaporization. The particles were co-cultured with 2-D cells to form 3-D spheroids and could be vaporized even when encapsulated within the spheroids via laser irradiation, which provides an effective basis for further work. PMID:28262671
2-D Modeling of Nanoscale MOSFETs: Non-Equilibrium Green's Function Approach
Svizhenko, Alexei; Anantram, M. P.; Govindan, T. R.; Biegel, Bryan
2001-01-01
We have developed physical approximations and computer code capable of realistically simulating 2-D nanoscale transistors, using the non-equilibrium Green's function (NEGF) method. This is the most accurate full quantum model yet applied to 2-D device simulation. Open boundary conditions and oxide tunneling are treated on an equal footing. Electrons in the ellipsoids of the conduction band are treated within the anisotropic effective mass approximation. Electron-electron interaction is treated within Hartree approximation by solving NEGF and Poisson equations self-consistently. For the calculations presented here, parallelization is performed by distributing the solution of NEGF equations to various processors, energy wise. We present simulation of the "benchmark" MIT 25nm and 90nm MOSFETs and compare our results to those from the drift-diffusion simulator and the quantum-corrected results available. In the 25nm MOSFET, the channel length is less than ten times the electron wavelength, and the electron scattering time is comparable to its transit time. Our main results are: (1) Simulated drain subthreshold current characteristics are shown, where the potential profiles are calculated self-consistently by the corresponding simulation methods. The current predicted by our quantum simulation has smaller subthreshold slope of the Vg dependence which results in higher threshold voltage. (2) When gate oxide thickness is less than 2 nm, gate oxide leakage is a primary factor which determines off-current of a MOSFET (3) Using our 2-D NEGF simulator, we found several ways to drastically decrease oxide leakage current without compromising drive current. (4) Quantum mechanically calculated electron density is much smaller than the background doping density in the poly silicon gate region near oxide interface. This creates an additional effective gate voltage. Different ways to. include this effect approximately will be discussed.
Dynamical modeling of sub-grid scales in 2D turbulence
Laval, Jean-Philippe; Dubrulle, Bérengère; Nazarenko, Sergey
2000-08-01
We develop a new numerical method which treats resolved and sub-grid scales as two different fluid components evolving according to their own dynamical equations. These two fluids are nonlinearly interacting and can be transformed one into another when their scale becomes comparable to the grid size. Equations describing the two-fluid dynamics were rigorously derived from Euler equations [B. Dubrulle, S. Nazarenko, Physica D 110 (1997) 123-138] and they do not involve any adjustable parameters. The main assumption of such a derivation is that the large-scale vortices are so strong that they advect the sub-grid scales as a passive scalar, and the interactions of small scales with small and intermediate scales can be neglected. As a test for our numerical method, we performed numerical simulations of 2D turbulence with a spectral gap, and we found a good agreement with analytical results obtained for this case by Nazarenko and Laval [Non-local 2D turbulence and passive scalars in Batchelor’s regime, J. Fluid Mech., in press]. We used the two-fluid method to study three typical problems in 2D dynamics of incompressible fluids: decaying turbulence, vortex merger and forced turbulence. The two-fluid simulations performed on at 128 2 and 256 2 resolution were compared with pseudo-spectral simulations using hyperviscosity performed at the same and at much higher resolution. This comparison shows that performance of the two-fluid method is much better than one of the pseudo-spectral method at the same resolution and comparable computational cost. The most significant improvement is observed in modeling of the small-scale component, so that effective inertial interval increases by about two decades compared to the high-resolution pseudo-spectral method. Using the two-fluid method, we demonstrated that the k-3 tail always exists for the energy spectrum, although its amplitude is slowly decreasing in decaying turbulence.
A Bayesian approach to modeling 2D gravity data using polygon states
Titus, W. J.; Titus, S.; Davis, J. R.
2015-12-01
We present a Bayesian Markov chain Monte Carlo (MCMC) method for the 2D gravity inversion of a localized subsurface object with constant density contrast. Our models have four parameters: the density contrast, the number of vertices in a polygonal approximation of the object, an upper bound on the ratio of the perimeter squared to the area, and the vertices of a polygon container that bounds the object. Reasonable parameter values can be estimated prior to inversion using a forward model and geologic information. In addition, we assume that the field data have a common random uncertainty that lies between two bounds but that it has no systematic uncertainty. Finally, we assume that there is no uncertainty in the spatial locations of the measurement stations. For any set of model parameters, we use MCMC methods to generate an approximate probability distribution of polygons for the object. We then compute various probability distributions for the object, including the variance between the observed and predicted fields (an important quantity in the MCMC method), the area, the center of area, and the occupancy probability (the probability that a spatial point lies within the object). In addition, we compare probabilities of different models using parallel tempering, a technique which also mitigates trapping in local optima that can occur in certain model geometries. We apply our method to several synthetic data sets generated from objects of varying shape and location. We also analyze a natural data set collected across the Rio Grande Gorge Bridge in New Mexico, where the object (i.e. the air below the bridge) is known and the canyon is approximately 2D. Although there are many ways to view results, the occupancy probability proves quite powerful. We also find that the choice of the container is important. In particular, large containers should be avoided, because the more closely a container confines the object, the better the predictions match properties of object.
Be2D: A model to understand the distribution of meteoric 10Be in soilscapes
Campforts, Benjamin; Vanacker, Veerle; Vanderborght, Jan; Govers, Gerard
2016-04-01
Cosmogenic nuclides have revolutionised our understanding of earth surface process rates. They have become one of the standard tools to quantify soil production by weathering, soil redistribution and erosion. Especially Beryllium-10 has gained much attention due to its long half-live and propensity to be relatively conservative in the landscape. The latter makes 10Be an excellent tool to assess denudation rates over the last 1000 to 100 × 103 years, bridging the anthropogenic and geological time scale. Nevertheless, the mobility of meteoric 10Be in soil systems makes translation of meteoric 10Be inventories into erosion and deposition rates difficult. Here we present a coupled soil hillslope model, Be2D, that is applied to synthetic and real topography to address the following three research questions. (i) What is the influence of vertical meteoric Be10 mobility, caused by chemical mobility, clay translocation and bioturbation, on its lateral redistribution over the soilscape, (ii) How does vertical mobility influence erosion rates and soil residence times inferred from meteoric 10Be inventories and (iii) To what extent can a tracer with a half-life of 1.36 Myr be used to distinguish between natural and human-disturbed soil redistribution rates? The model architecture of Be2D is designed to answer these research questions. Be2D is a dynamic model including physical processes such as soil formation, physical weathering, clay migration, bioturbation, creep, overland flow and tillage erosion. Pathways of meteoric 10Be mobility are simulated using a two step approach which is updated each timestep. First, advective and diffusive mobility of meteoric 10Be is simulated within the soil profile and second, lateral redistribution because of lateral soil fluxes is calculated. The performance and functionality of the model is demonstrated through a number of synthetic and real model runs using existing datasets of meteoric 10Be from case-studies in southeastern US. Brute
Estimating nitrogen losses in furrow irrigated soil amended by compost using HYDRUS-2D model
Iqbal, Shahid; Guber, Andrey; Zaman Khan, Haroon; ullah, Ehsan
2014-05-01
Furrow irrigation commonly results in high nitrogen (N) losses from soil profile via deep infiltration. Estimation of such losses and their reduction is not a trivial task because furrow irrigation creates highly nonuniform distribution of soil water that leads to preferential water and N fluxes in soil profile. Direct measurements of such fluxes are impractical. The objective of this study was to assess applicability of HYDRUS-2D model for estimating nitrogen balance in manure amended soil under furrow irrigation. Field experiments were conducted in a sandy loam soil amended by poultry manure compost (PMC) and pressmud compost (PrMC) fertilizers. The PMC and PrMC contained 2.5% and 0.9% N and were applied at 5 rates: 2, 4, 6, 8 and 10 ton/ha. Plots were irrigated starting from 26th day from planting using furrows with 1x1 ridge to furrow aspect ratio. Irrigation depths were 7.5 cm and time interval between irrigations varied from 8 to 15 days. Results of the field experiments showed that approximately the same corn yield was obtained with considerably higher N application rates using PMC than using PrMC as a fertilizer. HYDRUS-2D model was implemented to evaluate N fluxes in soil amended by PMC and PrMC fertilizers. Nitrogen exchange between two pools of organic N (compost and soil) and two pools of mineral N (soil NH4-N and soil NO3-N) was modeled using mineralization and nitrification reactions. Sources of mineral N losses from soil profile included denitrification, root N uptake and leaching with deep infiltration of water. HYDRUS-2D simulations showed that the observed increases in N root water uptake and corn yields associated with compost application could not be explained by the amount of N added to soil profile with the compost. Predicted N uptake by roots significantly underestimated the field data. Good agreement between simulated and field-estimated values of N root uptake was achieved when the rate of organic N mineralization was increased
Destabilization of survival factor MEF2D mRNA by neurotoxin in models of Parkinson's disease.
Wang, Bao; Cai, Zhibiao; Lu, Fangfang; Li, Chen; Zhu, Xiaofei; Su, Linna; Gao, Guodong; Yang, Qian
2014-09-01
Progressive loss of dopaminergic (DA) neurons in the substantial nigra pars compacta (SNc) is an important pathological feature in Parkinson's disease (PD). Loss of transcription factor myocyte enhancer factor 2D (MEF2D), a key neuronal survival factor, has been shown to underlie the loss of DA neurons in SNc and the pathogenic process of PD. It is known that PD-associated neurotoxins reduce the level of MEF2D protein to trigger neuronal death. Although neurotoxins clearly destabilize MEF2D by post-translational mechanisms, it is not known whether regulation of MEF2D mRNA contributes to neurotoxin-induced decrease in MEF2D protein. In this work, we showed that MPP(+), the toxic metabolite of MPTP, caused a significant decrease in the half-life and total level of MEF2D mRNA in a DA neuronal cell line, SN4741 cells. Quantitative PCR analysis of the SNc DA neurons captured by immune-laser capture microdissection showed that exposure to MPTP led to a marked reduction in the level of MEF2D mRNA in SNc DA neurons compared to controls. Down-regulation of MEF2D mRNA alone reduced the viability of SN4741 cells and sensitized the cells to MPP(+)-induced toxicity. These results suggest that destabilization and reduction in MEF2D mRNA is in part responsible for neurotoxin-induced decrease in MEF2D protein and neuronal viability. Myocyte enhancer factor 2D (MEF2D) plays an important role in neuronal survival. How MEF2D mRNA is deregulated under toxic stress is unclear. We found that PD-associated neurotoxins destabilize MEF2D mRNA and reduce its level in vitro and in vivo. Reduction in MEF2D mRNA is sufficient to sensitize model cells to neurotoxin-induced toxicity, suggesting that destabilization of MEF2D mRNA is part of the mechanism by which neurotoxins trigger deregulation of neuronal survival.
Bezzeccheri, E.; Colasanti, S.; Falco, A.; Liguori, R.; Rubino, A.; Lugli, P.
2016-05-01
Vertical Organic Transistors and Phototransistors have been proven to be promising technologies due to the advantages of reduced channel length and larger sensitive area with respect to planar devices. Nevertheless, a real improvement of their performance is subordinate to the quantitative description of their operation mechanisms. In this work, we present a comparative study on the modeling of vertical and planar Organic Phototransistor (OPT) structures. Computer-based simulations of the devices have been carried out with Synopsys Sentaurus TCAD in a 2D Drift-Diffusion framework. The photoactive semiconductor material has been modeled using the virtual semiconductor approach as the archetypal P3HT:PC61BM bulk heterojunction. It has been found that both simulated devices have comparable electrical and optical characteristics, accordingly to recent experimental reports on the subject.
Complex-temperature properties of the Ising model on 2D heteropolygonal lattices
Matveev, V; Matveev, Victor; Shrock, Robert
1995-01-01
Using exact results, we determine the complex-temperature phase diagrams of the 2D Ising model on three regular heteropolygonal lattices, (3 \\cdot 6 \\cdot 3 \\cdot 6) (kagom\\'{e}), (3 \\cdot 12^2), and (4 \\cdot 8^2) (bathroom tile), where the notation denotes the regular n-sided polygons adjacent to each vertex. We also work out the exact complex-temperature singularities of the spontaneous magnetisation. A comparison with the properties on the square, triangular, and hexagonal lattices is given. In particular, we find the first case where, even for isotropic spin-spin exchange couplings, the nontrivial non-analyticities of the free energy of the Ising model lie in a two-dimensional, rather than one-dimensional, algebraic variety in the z=e^{-2K} plane.
Mo, Yike; Greenhalgh, Stewart A.; Robertsson, Johan O. A.; Karaman, Hakki
2015-05-01
Lateral velocity variations and low velocity near-surface layers can produce strong scattered and guided waves which interfere with reflections and lead to severe imaging problems in seismic exploration. In order to investigate these specific problems by laboratory seismic modelling, a simple 2D ultrasonic model facility has been recently assembled within the Wave Propagation Lab at ETH Zurich. The simulated geological structures are constructed from 2 mm thick metal and plastic sheets, cut and bonded together. The experiments entail the use of a piezoelectric source driven by a pulse amplifier at ultrasonic frequencies to generate Lamb waves in the plate, which are detected by piezoelectric receivers and recorded digitally on a National Instruments recording system, under LabVIEW software control. The 2D models employed were constructed in-house in full recognition of the similitude relations. The first heterogeneous model features a flat uniform low velocity near-surface layer and deeper dipping and flat interfaces separating different materials. The second model is comparable but also incorporates two rectangular shaped inserts, one of low velocity, the other of high velocity. The third model is identical to the second other than it has an irregular low velocity surface layer of variable thickness. Reflection as well as transmission experiments (crosshole & vertical seismic profiling) were performed on each model. The two dominant Lamb waves recorded are the fundamental symmetric mode (non-dispersive) and the fundamental antisymmetric (flexural) dispersive mode, the latter normally being absent when the source transducer is located on a model edge but dominant when it is on the flat planar surface of the plate. Experimental group and phase velocity dispersion curves were determined and plotted for both modes in a uniform aluminium plate. For the reflection seismic data, various processing techniques were applied, as far as pre-stack Kirchhoff migration. The
A 2-D Analytical Threshold Voltage Model for Symmetric Double Gate MOSFET's Using Green’s Function
Directory of Open Access Journals (Sweden)
Anoop Garg
2011-01-01
Full Text Available We propose a new two dimensional (2D analytical solution of Threshold Voltage for undoped (or lightly doped Double Gate MOSFETs. We have used Green’s function technique to solve the 2D Poisson equation, and derived the threshold voltage model using minimum surface potential concept. This model is assumed uniform doping profile in Si region. The proposed model compared with existing literature and experimental data and we obtain excellent agreements with previous techniques.
The combined effect of attraction and orientation zones in 2D flocking models
Iliass, Tarras; Cambui, Dorilson
2016-01-01
In nature, many animal groups, such as fish schools or bird flocks, clearly display structural order and appear to move as a single coherent entity. In order to understand the complex motion of these systems, we study the Vicsek model of self-propelled particles (SPP) which is an important tool to investigate the behavior of collective motion of live organisms. This model reproduces the biological behavior patterns in the two-dimensional (2D) space. Within the framework of this model, the particles move with the same absolute velocity and interact locally in the zone of orientation by trying to align their direction with that of the neighbors. In this paper, we model the collective movement of SPP using an agent-based model which follows biologically motivated behavioral rules, by adding a second region called the attraction zone, where each particles move towards each other avoiding being isolated. Our main goal is to present a detailed numerical study on the effect of the zone of attraction on the kinetic phase transition of our system. In our study, the consideration of this zone seems to play an important role in the cohesion. Consequently, in the directional orientation, the zone that we added forms the compact particle group. In our simulation, we show clearly that the model proposed here can produce two collective behavior patterns: torus and dynamic parallel group. Implications of these findings are discussed.
A simple model for 2D image upconversion of incoherent light
DEFF Research Database (Denmark)
Dam, Jeppe Seidelin; Pedersen, Christian; Tidemand-Lichtenberg, Peter
2011-01-01
We present a simple theoretical model for 2 dimensional (2-D) image up-conversion of incoherent light. While image upconversion has been known for more than 40 years, the technology has been hindered by very low conversion quantum efficiency (~10-7). We show that our implementation compared...... to previous work can result in a feasible system: Using intracavity upconversion and Quasi Phase Matching (QPM) nonlinear materials provide increased conversion efficiency. Using a QPM crystal and choosing the wavelengths so the first order term in the phasematch wavelength acceptance vanishes, results...... in very large wavelength acceptance. This work describes how the bandwidth acceptance can be predicted and designed. This gives promise of a new way to make infrared imaging devices with tunable spectral sensitivity....
Entire solutions for a mono-stable delay population model in a 2D lattice strip
Directory of Open Access Journals (Sweden)
Hai-Qin Zhao
2014-11-01
Full Text Available This article concerns the entire solutions of a mono-stable age-structured population model in a 2D lattice strip. In a previous publication, we established the existence of entire solutions related to traveling wave solutions with speeds larger than the minimal wave speed $c_{\\rm min}$. However, the existence of entire solutions related to the minimal wave fronts remains open open question. In this article, we first establish a new comparison theorem. Then, applying the theorem we obtain the existence of entire solutions by mixing any finite number of traveling wave fronts with speeds $c\\geq c_{\\rm min}$, and a solution without the $j$ variable. In particular, we show the relationship between the entire solution and the traveling wave fronts that they originate.
The strong-weak coupling symmetry in 2D Φ4 field models
Directory of Open Access Journals (Sweden)
B.N.Shalaev
2005-01-01
Full Text Available It is found that the exact beta-function β(g of the continuous 2D gΦ4 model possesses two types of dual symmetries, these being the Kramers-Wannier (KW duality symmetry and the strong-weak (SW coupling symmetry f(g, or S-duality. All these transformations are explicitly constructed. The S-duality transformation f(g is shown to connect domains of weak and strong couplings, i.e. above and below g*. Basically it means that there is a tempting possibility to compute multiloop Feynman diagrams for the β-function using high-temperature lattice expansions. The regular scheme developed is found to be strongly unstable. Approximate values of the renormalized coupling constant g* found from duality symmetry equations are in an agreement with available numerical results.
Time domain numerical modeling of wave propagation in 2D acoustic / porous media
Chiavassa, Guillaume
2011-01-01
Numerical methods are developed to simulate the wave propagation in 2D heterogeneous fluid / poroelastic media. Wave propagation is described by the usual acoustics equations (in the fluid medium) and by the low-frequency Biot's equations (in the porous medium). Interface conditions are introduced to model various hydraulic contacts between the two media: open pores, sealed pores, and imperfect pores. Well-possedness of the initial-boundary value problem is proven. Cartesian grid numerical methods previously developed in porous heterogeneous media are adapted to the present context: a fourth-order ADER scheme with Strang splitting for time-marching; a space-time mesh-refinement to capture the slow compressional wave predicted by Biot's theory; and an immersed interface method to discretize the interface conditions and to introduce a subcell resolution. Numerical experiments and comparisons with exact solutions are proposed for the three types of interface conditions, demonstrating the accuracy of the approach...
Zhao, Hongbo; Engelbrecht, Jan R.
2000-03-01
At the Mean Field level (G. Murthy and R. Shankar, J. Phys. Condens. Matter, 7) (1995), the frustration due to an external field first makes the uniform BCS ground state unstable to an incommensurate (qne0) superconducting state and then to a spin-polarized Fermi Liquid state. Our interest is how fluctuations modify this picture, as well as the normal state of this system which has a quantum critical point. We use the Fluctuation-Exchange Approximation for the 2D Attractive Hubbard Model, to study this system beyond the Mean-Field level. Earlier work in zero field has shown that this numerical method successfully captures the critical scaling of the KT superconducting transition upon cooling in the normal state. Here we investigate how the pair-breaking external field modifies this picture, and the development of incommensurate pairing.
Robust autonomous model learning from 2D and 3D data sets.
Langs, Georg; Donner, René; Peloschek, Philipp; Bischof, Horst
2007-01-01
In this paper we propose a weakly supervised learning algorithm for appearance models based on the minimum description length (MDL) principle. From a set of training images or volumes depicting examples of an anatomical structure, correspondences for a set of landmarks are established by group-wise registration. The approach does not require any annotation. In contrast to existing methods no assumptions about the topology of the data are made, and the topology can change throughout the data set. Instead of a continuous representation of the volumes or images, only sparse finite sets of interest points are used to represent the examples during optimization. This enables the algorithm to efficiently use distinctive points, and to handle texture variations robustly. In contrast to standard elasticity based deformation constraints the MDL criterion accounts for systematic deformations typical for training sets stemming from medical image data. Experimental results are reported for five different 2D and 3D data sets.
An application of the distributed hydrologic model CASC2D to a tropical montane watershed
Marsik, Matt; Waylen, Peter
2006-11-01
SummaryIncreased stormflow in the Quebrada Estero watershed (2.5 km 2), in the northwestern Central Valley tectonic depression of Costa Rica, reportedly has caused flooding of the city of San Ramón in recent decades. Although scientifically untested, urban expansion was deemed the cause and remedial measures were recommended by the Programa de Investigación en Desarrollo Humano Sostenible (ProDUS). CASC2D, a physically-based, spatially explicit hydrologic model, was constructed and calibrated to a June 10th 2002 storm that delivered 110.5 mm of precipitation in 4.5 h visibly exceeded the bankfull stage (0.9 m) of the Quebrada flooding portions of San Ramón. The calibrated hydrograph showed a peak discharge 16.68% (2.5 m 3 s -1) higher, an above flood stage duration 20% shorter, and time to peak discharge 11 min later than the same observed discharge hydrograph characteristics. Simulations of changing land cover conditions from 1979 to 1999 showed an increase also in the peak discharge, above flood stage duration, and time to peak discharge. Analysis using a modified location quotient identified increased urbanization in lower portions of the watershed over the time period studied. These results suggest that increased urbanization in the Quebrada Estero watershed have increased flooding peaks, and durations above threshold, confirming the ProDUS report. These results and the CASC2D model offer an easy-to-use, pragmatic planning tool for policymakers in San Ramón to assess future development scenarios and their potential flooding impacts to San Ramón.
Wörz, Stefan; Heinzer, Stephan; Weiss, Matthias; Rohr, Karl
2008-03-01
We introduce a model-based approach for segmenting and quantifying GFP-tagged subcellular structures of the Golgi apparatus in 2D and 3D microscopy images. The approach is based on 2D and 3D intensity models, which are directly fitted to an image within 2D circular or 3D spherical regions-of-interest (ROIs). We also propose automatic approaches for the detection of candidates, for the initialization of the model parameters, and for adapting the size of the ROI used for model fitting. Based on the fitting results, we determine statistical information about the spatial distribution and the total amount of intensity (fluorescence) of the subcellular structures. We demonstrate the applicability of our new approach based on 2D and 3D microscopy images.
2-D Finite Difference Modeling of the D'' Structure Beneath the Eastern Cocos Plate: Part I
Helmberger, D. V.; Song, T. A.; Sun, D.
2005-12-01
The discovery of phase transition from Perovskite (Pv) to Post-Perovskite (PPv) at depth nears the lowermost mantle has revealed a new view of the earth's D'' layer (Oganov et al. 2004; Murakami et al. 2004). Hernlund et al. (2004) recently pusposed that, depending on the geotherm at the core-mantle boundary (CMB), a double-crossing of the phase boundary by the geotherm at two different depths may also occur. To explore these new findings, we adopt 2-D finite difference scheme (Helmberger and Vidale, 1988) to model wave propagation in rapidly varying structure. We collect broadband waveform data recorded by several Passcal experiments, such as La Ristra transect and CDROM transect in the southwest US to constrain the lateral variations in D'' structure. These data provide fairly dense sampling (~ 20 km) in the lowermost mantle beneath the eastern Cocos plate. Since the source-receiver paths are mostly in the same azimuth, we make 2-D cross-sections from global tomography model (Grand, 2002) and compute finite difference synthetics. We modify the lowermost mantle below 2500 km with constraints from transverse-component waveform data at epicentral distances of 70-82 degrees in the time window between S and ScS, essentially foward modeling waveforms. Assuming a velocity jump of 3 % at D'', our preferred model shows that the D'' topography deepens from the north to the south by about 120 km over a lateral distance of 300 km. Such large topography jumps have been proposed by Thomas et al. (2004) using data recorded by TriNet. In addition, there is a negative velocity jump (-3 %) 100 km above the CMB in the south. This simple model compare favorably with results from a study by Sun, Song and Helmberger (2005), who follow Sidorin et al. (1999) approach and produce a thermodynamically consistent velocity model with Pv-PPv phase boundary. It appears that much of this complexity exists in Grand's tomographic maps with rapid variation in velocities just above the D''. We also
Energy Technology Data Exchange (ETDEWEB)
Gurban, Ioana (3D Terra (Canada))
2008-08-15
This work represents the stage 2.3 of the hydrochemical evaluation and modelling of the Forsmark data. This comprises M3 modelling and 2D visualisation of the data along the boreholes. The following conclusions can be drawn: - M3 modelling helped to summarise and understand the data, by using as variables the major elements and the isotopes delta18O and deltaD. - Previous alternative models and the experience from Forsmark 1.2, 2.1 and 2.2, helped to clarify different previously unsolved issues such as: the use of variables, tests with different endmembers, the use of only groundwater data in order to build a bedrock hydrochemical model. - The visualisation of the mixing proportions along the boreholes helps to understand the distribution of the data in the domain and to check and compare the results of different models; and therefore to chose the model which best describes the measured data. - The different M3 modelling tests resulted in the following conclusions: a) When calculating mixing proportions only samples from the boreholes will be used, b) the altered meteoric end-member which best describes the more shallow groundwater compositions is defined by a representative upper bedrock sample; the Littorina end-member employed the existing modelled compositions; the Deep saline and glacial end-members compositions were tested by means of a feasibility study and employed in the modelling. - Three models were presented. All the models are good and can be used, but the best is to use the one that fits the conceptual model best and the hydrogeochemical understanding. - The use of Littorina, Glacial, Deep Saline and Altered Meteoric end-members makes possible the comparison of different sites such as Laxemar and Forsmark. - All the data used in the M3 modelling and the results of the modelling and visualisation along the boreholes are presented in SKB database SIMON. - The extended data do not affect the results of the modelling of the Forsmark 2.3 dataset (the
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.
Distributed and coupled 2D electro-thermal model of power semiconductor devices
Belkacem, Ghania; Lefebvre, Stéphane; Joubert, Pierre-Yves; Bouarroudj-Berkani, Mounira; Labrousse, Denis; Rostaing, Gilles
2014-05-01
The development of power electronics in the field of transportations (automotive, aeronautics) requires the use of power semiconductor devices providing protection and diagnostic functions. In the case of series protections power semiconductor devices which provide protection may operate in shortcircuit and act as a current limiting device. This mode of operations is very constraining due to the large dissipation of power. In these particular conditions of operation, electro-thermal models of power semiconductor devices are of key importance in order to optimize their thermal design and increase their reliability. The development of such an electro-thermal model for power MOSFET transistors based on the coupling between two computation softwares (Matlab and Cast3M) is described in this paper. The 2D electro-thermal model is able to predict (i) the temperature distribution on chip surface well as in the volume under short-circuit operations, (ii) the effect of the temperature on the distribution of the current flowing within the die and (iii) the effects of the ageing of the metallization layer on the current density and the temperature. In this paper, the electrical and thermal models are described as well as the implemented coupling scheme.
Komura, Yukihiro; Okabe, Yutaka
2016-03-01
We present new versions of sample CUDA programs for the GPU computing of the Swendsen-Wang multi-cluster spin flip algorithm. In this update, we add the method of GPU-based cluster-labeling algorithm without the use of conventional iteration (Komura, 2015) to those programs. For high-precision calculations, we also add a random-number generator in the cuRAND library. Moreover, we fix several bugs and remove the extra usage of shared memory in the kernel functions.
Transectional heat transfer in thermoregulating bigeye tuna (Thunnus obesus) - a 2D heat flux model.
Boye, Jess; Musyl, Michael; Brill, Richard; Malte, Hans
2009-11-01
We developed a 2D heat flux model to elucidate routes and rates of heat transfer within bigeye tuna Thunnus obesus Lowe 1839 in both steady-state and time-dependent settings. In modeling the former situation, we adjusted the efficiencies of heat conservation in the red and the white muscle so as to make the output of the model agree as closely as possible with observed cross-sectional isotherms. In modeling the latter situation, we applied the heat exchanger efficiencies from the steady-state model to predict the distribution of temperature and heat fluxes in bigeye tuna during their extensive daily vertical excursions. The simulations yielded a close match to the data recorded in free-swimming fish and strongly point to the importance of the heat-producing and heat-conserving properties of the white muscle. The best correspondence between model output and observed data was obtained when the countercurrent heat exchangers in the blood flow pathways to the red and white muscle retained 99% and 96% (respectively) of the heat produced in these tissues. Our model confirms that the ability of bigeye tuna to maintain elevated muscle temperatures during their extensive daily vertical movements depends on their ability to rapidly modulate heating and cooling rates. This study shows that the differential cooling and heating rates could be fully accounted for by a mechanism where blood flow to the swimming muscles is either exclusively through the heat exchangers or completely shunted around them, depending on the ambient temperature relative to the body temperature. Our results therefore strongly suggest that such a mechanism is involved in the extensive physiological thermoregulatory abilities of endothermic bigeye tuna.
In vitro systems to study nephropharmacology : 2D versus 3D models
Sánchez-Romero, Natalia; Schophuizen, Carolien M S; Giménez, Ignacio; Masereeuw, Rosalinde
2016-01-01
The conventional 2-dimensional (2D) cell culture is an invaluable tool in, amongst others, cell biology and experimental pharmacology. However, cells cultured in 2D, on the top of stiff plastic plates lose their phenotypical characteristics and fail in recreating the physiological environment found
Field-induced magnetization jumps and quantum criticality in the 2D J-Q model
Iaizzi, Adam; Sandvik, Anders
The J-Q model is a `designer hamiltonian' formed by adding a four spin `Q' term to the standard antiferromagnetic S = 1 / 2 Heisenberg model. The Q term drives a quantum phase transition to a valence-bond solid (VBS) state: a non-magnetic state with a pattern of local singlets which breaks lattice symmetries. The elementary excitations of the VBS are triplons, i.e. gapped S=1 quasiparticles. There is considerable interest in the quantum phase transition between the Néel and VBS states as an example of deconfined quantum criticality. Near the phase boundary, triplons deconfine into pairs of bosonic spin-1/2 excitations known as spinons. Using exact diagonalization and the stochastic series expansion quantum monte carlo method, we study the 2D J-Q model in the presence of an external magnetic field. We use the field to force a nonzero density of magnetic excitations at T=0 and look for signatures of Bose-Einstein condensation of spinons. At higher magnetic fields, there is a jump in the induced magnetization caused by the onset of an effective attractive interaction between magnons on a ferromagnetic background. We characterize the first order quantum phase transition and determine the minimum value of the coupling ratio q ≡ Q / J required to produce this jump. Funded by NSF DMR-1410126.
On the assimilation of SWOT type data into 2D shallow-water models
Frédéric, Couderc; Denis, Dartus; Pierre-André, Garambois; Ronan, Madec; Jérôme, Monnier; Jean-Paul, Villa
2013-04-01
In river hydraulics, assimilation of water level measurements at gauging stations is well controlled, while assimilation of images is still delicate. In the present talk, we address the richness of satellite mapped information to constrain a 2D shallow-water model, but also related difficulties. 2D shallow models may be necessary for small scale modelling in particular for low-water and flood plain flows. Since in both cases, the dynamics of the wet-dry front is essential, one has to elaborate robust and accurate solvers. In this contribution we introduce robust second order, stable finite volume scheme [CoMaMoViDaLa]. Comparisons of real like tests cases with more classical solvers highlight the importance of an accurate flood plain modelling. A preliminary inverse study is presented in a flood plain flow case, [LaMo] [HoLaMoPu]. As a first step, a 0th order data processing model improves observation operator and produces more reliable water level derived from rough measurements [PuRa]. Then, both model and flow behaviours can be better understood thanks to variational sensitivities based on a gradient computation and adjoint equations. It can reveal several difficulties that a model designer has to tackle. Next, a 4D-Var data assimilation algorithm used with spatialized data leads to improved model calibration and potentially leads to identify river discharges. All the algorithms are implemented into DassFlow software (Fortran, MPI, adjoint) [Da]. All these results and experiments (accurate wet-dry front dynamics, sensitivities analysis, identification of discharges and calibration of model) are currently performed in view to use data from the future SWOT mission. [CoMaMoViDaLa] F. Couderc, R. Madec, J. Monnier, J.-P. Vila, D. Dartus, K. Larnier. "Sensitivity analysis and variational data assimilation for geophysical shallow water flows". Submitted. [Da] DassFlow - Data Assimilation for Free Surface Flows. Computational software http
2D spectral element modeling of GPR wave propagation in inhomogeneous media
Zarei, Sajad; Oskooi, Behrooz; Amini, Navid; Dalkhani, Amin Rahimi
2016-10-01
We present a spectral element method, for simulation of ground-penetrating radar (GPR) in two dimensions. The technique is based upon a weak formulation of the equations of Maxwell and combines the flexibility of the elemental-based methods with the accuracy of the spectral based methods. The wave field on the elements is discretized using high-degree Lagrange interpolation and integration over an element is accomplished based upon the Gauss-Lobatto-Legendre integration rule. As a result, the mass matrix and the damping matrix are always diagonal, which drastically reduces the computational cost. We first develop the formulation of 2D spectral element method (SEM) in the time-domain based on Maxwell's equations. The presented formulation is with matrix notation that simplifies the implementation of the relations in computer programs, especially in MATLAB application. We discuss the differences between spectral element method and finite-element method in the time-domain. Also, we show that the SEM numerical dispersion is much lower than FEM. To absorb waves at the edges of the modeling domain, we implement first order Clayton and Engquist absorbing boundary conditions (CE-ABC) introduced in numerical finite-difference modeling of seismic wave propagation. We used the SEM to simulate a complex model to show its abilities and limitations. As well as, one distinct advantage of SEM is that we can easily define our model features in nodal points, because the integration points and the interpolation points are similar that makes it very flexible in simulation of complex models.
A single domain direct carbon fuel cell (DCFC) 2-D modeling
Energy Technology Data Exchange (ETDEWEB)
Elleuch, A.; Boussetta, A.; Halouani, K. [Sfax Univ., Sfax (Tunisia). Inst. Preparatoire aux Etudes d' Ingenieurs de Sfax, Micro-Electro-Thermal Systems, Industrial Energy Systems Group; Sahraoui, M. [Tunis Univ., Tunis (Tunisia). LASMAP EPT IPEIT
2010-07-01
There has been a renewed interest in cells fuelled with solid carbon because they promise increased conversion efficiencies for coal-based power generation with less production of carbon dioxide (CO{sub 2}). In addition, the CO{sub 2} produced in a direct carbon fuel cell (DCFC) is capture-ready for sequestration. The DCFC is a special type of high temperature fuel cell in which solid carbon directly reacts with oxygen to form CO{sub 2} and electricity. This paper presented a numerical 2-D model that simulates the transport of gaseous species, electrochemical kinetics, energy transport, and ionic current distribution for all regions of the DCFC. The governing differential equations were solved over a single computational domain, which consisted of a cathode gas channel, cathode gas diffusion layer, and cathode catalyst layer for the cathode side of the cell, a simple bloc for the anode side as well as the molten carbonate electrolyte. The coupled set of differential equations was solved using a FORTRAN code, and was readily adaptable in terms of geometry and material property definitions. The results showed temperature, carbon dioxide and oxygen concentration profile in all DCFC compartments. It was concluded that the model contributes to a better understanding of the heat and mass transfer mechanisms occurring within the cell. 10 refs., 3 tabs., 8 figs.
Multi-GPU Accelerated Multi-Spin Monte Carlo Simulations of the 2D Ising Model
Block, Benjamin; Preis, Tobias; 10.1016/j.cpc.2010.05.005
2010-01-01
A modern graphics processing unit (GPU) is able to perform massively parallel scientific computations at low cost. We extend our implementation of the checkerboard algorithm for the two dimensional Ising model [T. Preis et al., J. Comp. Phys. 228, 4468 (2009)] in order to overcome the memory limitations of a single GPU which enables us to simulate significantly larger systems. Using multi-spin coding techniques, we are able to accelerate simulations on a single GPU by factors up to 35 compared to an optimized single Central Processor Unit (CPU) core implementation which employs multi-spin coding. By combining the Compute Unified Device Architecture (CUDA) with the Message Parsing Interface (MPI) on the CPU level, a single Ising lattice can be updated by a cluster of GPUs in parallel. For large systems, the computation time scales nearly linearly with the number of GPUs used. As proof of concept we reproduce the critical temperature of the 2D Ising model using finite size scaling techniques.
Risk zone of wrack hitting marine structure simulated by 2D hydraulic model
Institute of Scientific and Technical Information of China (English)
MA Jin-rong; GUO Ya-qiong; NAN Wei
2010-01-01
The wrack or the ship out of control will drift with flow.One of the most important factors that drive the ship is flow current which moves circularly in tidal area.The wrack from same place always drifts in different ways if the start time is different.So,during the ship drifting period,the drift trace is also determined by both wave and wind forces.The drift direction is limited by water depth which must be deeper than ship draft.These marine structures that can not afford the hit of wrack or will destroy the wrack must be well considered when they are placed near harbor and waterway or other water area with ship running.The risk zone should be consulted according to tide and weather conditions to protect structures and ships in necessary.A method is presented here to simulate the risk zone by 2D numerical hydraulic model with tidal current,wave,wind and water depth considered.This model can be used to built early-warning and protect system for special maline structure.
Beyond Flood Hazard Maps: Detailed Flood Characterization with Remote Sensing, GIS and 2d Modelling
Santillan, J. R.; Marqueso, J. T.; Makinano-Santillan, M.; Serviano, J. L.
2016-09-01
Flooding is considered to be one of the most destructive among many natural disasters such that understanding floods and assessing the risks associated to it are becoming more important nowadays. In the Philippines, Remote Sensing (RS) and Geographic Information System (GIS) are two main technologies used in the nationwide modelling and mapping of flood hazards. Although the currently available high resolution flood hazard maps have become very valuable, their use for flood preparedness and mitigation can be maximized by enhancing the layers of information these maps portrays. In this paper, we present an approach based on RS, GIS and two-dimensional (2D) flood modelling to generate new flood layers (in addition to the usual flood depths and hazard layers) that are also very useful in flood disaster management such as flood arrival times, flood velocities, flood duration, flood recession times, and the percentage within a given flood event period a particular location is inundated. The availability of these new layers of flood information are crucial for better decision making before, during, and after occurrence of a flood disaster. The generation of these new flood characteristic layers is illustrated using the Cabadbaran River Basin in Mindanao, Philippines as case study area. It is envisioned that these detailed maps can be considered as additional inputs in flood disaster risk reduction and management in the Philippines.
BEYOND FLOOD HAZARD MAPS: DETAILED FLOOD CHARACTERIZATION WITH REMOTE SENSING, GIS AND 2D MODELLING
Directory of Open Access Journals (Sweden)
J. R. Santillan
2016-09-01
Full Text Available Flooding is considered to be one of the most destructive among many natural disasters such that understanding floods and assessing the risks associated to it are becoming more important nowadays. In the Philippines, Remote Sensing (RS and Geographic Information System (GIS are two main technologies used in the nationwide modelling and mapping of flood hazards. Although the currently available high resolution flood hazard maps have become very valuable, their use for flood preparedness and mitigation can be maximized by enhancing the layers of information these maps portrays. In this paper, we present an approach based on RS, GIS and two-dimensional (2D flood modelling to generate new flood layers (in addition to the usual flood depths and hazard layers that are also very useful in flood disaster management such as flood arrival times, flood velocities, flood duration, flood recession times, and the percentage within a given flood event period a particular location is inundated. The availability of these new layers of flood information are crucial for better decision making before, during, and after occurrence of a flood disaster. The generation of these new flood characteristic layers is illustrated using the Cabadbaran River Basin in Mindanao, Philippines as case study area. It is envisioned that these detailed maps can be considered as additional inputs in flood disaster risk reduction and management in the Philippines.
A 2D mechanical-magneto-thermal model for direction-dependent magnetoelectric effect in laminates
Zhang, Shunzu; Yao, Hong; Gao, Yuanwen
2017-04-01
A two dimensional (2D) mechanical-magneto-thermal model of direction-dependent magnetoelectric (ME) effect in Terfenol-D/PZT/Terfenol-D laminated composites is established. The expressions of ME coefficient at low and resonance frequencies are derived by the average field method, respectively. The prediction of theoretical model presents a good agreement with the experimental data. The combined effect of orientation-dependent stress and magnetic fields, as well as operating temperature on ME coefficient is discussed. It is shown that ME effect presents a significantly nonlinear change with the increasing pre-stress under different loading angles. There exists an optimal angle and value of pre-stress corresponding to the best ME effect, improving the angle of pre-stress can get more prominent ME coupling than in x axis state. Note that an optimal angle of magnetic field gradually increases with the rise of pre-stress, which can further lead to the enhancement of ME coefficient. Meanwhile, reducing the operating temperature can enhance ME coefficient. Furthermore, resonance frequency, affected by pre-stress, magnetic field and temperature via ; ΔE effect;, can enhance ME coefficient about 100 times than that at low frequency.
Optimal implicit 2-D finite differences to model wave propagation in poroelastic media
Itzá, Reymundo; Iturrarán-Viveros, Ursula; Parra, Jorge O.
2016-08-01
Numerical modeling of seismic waves in heterogeneous porous reservoir rocks is an important tool for the interpretation of seismic surveys in reservoir engineering. We apply globally optimal implicit staggered-grid finite differences (FD) to model 2-D wave propagation in heterogeneous poroelastic media at a low-frequency range (<10 kHz). We validate the numerical solution by comparing it to an analytical-transient solution obtaining clear seismic wavefields including fast P and slow P and S waves (for a porous media saturated with fluid). The numerical dispersion and stability conditions are derived using von Neumann analysis, showing that over a wide range of porous materials the Courant condition governs the stability and this optimal implicit scheme improves the stability of explicit schemes. High-order explicit FD can be replaced by some lower order optimal implicit FD so computational cost will not be as expensive while maintaining the accuracy. Here, we compute weights for the optimal implicit FD scheme to attain an accuracy of γ = 10-8. The implicit spatial differentiation involves solving tridiagonal linear systems of equations through Thomas' algorithm.
The success of Fermi gas model for overall scaling of 2D metal-to-insulator transition data
Cheremisin, M. V.
2017-03-01
The melting condition for two-dimensional Wigner solid (Platzman and Fukuyama, 1974) [14] is shown to contain an error of a factor of π. The analysis of experimental data for apparent 2D metal-to-insulator transition shows that the Wigner solidification (Tanatar and Ceperley, 1989) [16] has been never achieved. Within routine Fermi gas model both the metallic and insulating behavior of different 2D system for actual range of carrier densities and temperatures is explained.
Lithospheric architecture of the Levant Basin (Eastern Mediterranean region): A 2D modeling approach
Inati, Lama; Zeyen, Hermann; Nader, Fadi Henri; Adelinet, Mathilde; Sursock, Alexandre; Rahhal, Muhsin Elie; Roure, François
2016-12-01
This paper discusses the deep structure of the lithosphere underlying the easternmost Mediterranean region, in particular the Levant Basin and its margins, where the nature of the crust, continental versus oceanic, remains debated. Crustal thickness and the depth of the lithosphere-asthenosphere boundary (LAB) as well as the crustal density distribution were calculated by integrating surface heat flow data, free-air gravity anomaly, geoid and topography. Accordingly, two-dimensional, lithospheric models of the study area are discussed, demonstrating the presence of a progressively attenuated crystalline crust from E to W (average thickness from 35 to 8 km). The crystalline crust is best interpreted as a strongly thinned continental crust under the Levant Basin, represented by two distinct components, an upper and a lower crust. Further to the west, the Herodotus Basin is believed to be underlain by an oceanic crust, with a thickness between 6 and 10 km. The Moho under the Arabian Plate is 35-40 km deep and becomes shallower towards the Mediterranean coast. It appears to be situated at depths ranging between 20 and 23 km below the Levant Basin and 26 km beneath the Herodotus Basin, based on our proposed models. At the Levantine margin, the thinning of the crust in the transitional domain between the onshore and the offshore is gradual, indicating successive extensional regimes that did not reach the beak up stage. In addition, the depth to LAB is around 120 km under the Arabian and the Eurasian Plates, 150 km under the Levant Basin, and it plunges to 180 km under the Herodotus Basin. This study shows that detailed 2D lithosphere modeling using integrated geophysical data can help understand the mechanisms responsible for the modelled lithospheric architecture when constrained with geological findings.
Electrical resistivity tomography applied to a complex lava dome: 2D and 3D models comparison
Portal, Angélie; Fargier, Yannick; Lénat, Jean-François; Labazuy, Philippe
2015-04-01
The study of volcanic domes growth (e.g. St. Helens, Unzen, Montserrat) shows that it is often characterized by a succession of extrusion phases, dome explosions and collapse events. Lava dome eruptive activity may last from days to decades. Therefore, their internal structure, at the end of the eruption, is complex and includes massive extrusions and lava lobes, talus and pyroclastic deposits as well as hydrothermal alteration. The electrical resistivity tomography (ERT) method, initially developed for environmental and engineering exploration, is now commonly used for volcano structure imaging. Because a large range of resistivity values is often observed in volcanic environments, the method is well suited to study the internal structure of volcanic edifices. We performed an ERT survey on an 11ka years old trachytic lava dome, the Puy de Dôme volcano (French Massif Central). The analysis of a recent high resolution DEM (LiDAR 0.5 m), as well as other geophysical data, strongly suggest that the Puy de Dôme is a composite dome. 11 ERT profiles have been carried out, both at the scale of the entire dome (base diameter of ~2 km and height of 400 m) on the one hand, and at a smaller scale on the summit part on the other hand. Each profile is composed of 64 electrodes. Three different electrode spacing have been used depending on the study area (35 m for the entire dome, 10 m and 5 m for its summit part). Some profiles were performed with half-length roll-along acquisitions, in order to keep a good trade-off between depth of investigation and resolution. Both Wenner-alpha and Wenner-Schlumberger protocols were used. 2-D models of the electrical resistivity distribution were computed using RES2DINV software. In order to constrain inversion models interpretation, the depth of investigation (DOI) method was applied to those results. It aims to compute a sensitivity index on inversion results, illustrating how the data influence the model and constraining models
Krali, Emiljana; Curry, Richard J
2011-04-26
To improve the efficiency of organic photovoltaic devices the inclusion of semiconducting nanoparticles such as PbS has been used to enhance near-infrared absorption. Additionally the use of interdigitated heterojunctions has been explored as a means of improving charge extraction. In this paper we provide a two-dimensional model taking into account these approaches with the aim of predicting an optimized device geometry to maximize the efficiency. The steady-state exciton population has been calculated in each of the active regions taking into account the full optical response based on using a finite difference approach to obtain approximate numerical solutions to the 2D exciton diffusion equation. On the basis of this we calculate the contribution of each active material to the device short circuit current and power conversion efficiency. We show that optimized structures can lead to power conversions efficiencies of ∼50% compared to a maximum of ∼17% for planar heterojunction devices. To achieve this the interdigitated region thickness should be ∼800 nm with PbS and C(60) widths of ∼60 and 20 nm, respectively. Even modest nanopatterning using much thinner active regions provides improvements in efficiency and may be approached using a variety of methods including nanoimprinting lithography, nanotemplating, or the incorporation of presynthesized nanorod structures.
Coupled Mode Equation Modeling for Out-of-Plane Gap Solitons in 2D Photonic Crystals
Dohnal, Tomas
2012-01-01
Out-of-plane gap solitons in 2D photonic crystals are optical beams localized in the plane of periodicity of the medium and delocalized in the orthogonal direction, in which they propagate with a nonzero velocity. We study such gap solitons as described by the Kerr nonlinear Maxwell system. Using a model of the nonlinear polarization, which does not generate higher harmonics, we obtain a closed curl-curl problem for the fundamental harmonic of the gap soliton. For gap solitons with frequencies inside spectral gaps and in an asymptotic vicinity of a gap edge we use a slowly varying envelope approximation based on the linear Bloch waves at the edge and slowly varying envelopes. We carry out a systematic derivation of the coupled mode equations (CMEs) which govern the envelopes. This derivation needs to be carried out in Bloch variables. The CMEs are a system of coupled nonlinear stationary Schr\\"odinger equations with an additional cross derivative term. Examples of gap soliton approximations are numerically co...
GPU computing with OpenCL to model 2D elastic wave propagation: exploring memory usage
Iturrarán-Viveros, Ursula; Molero-Armenta, Miguel
2015-01-01
Graphics processing units (GPUs) have become increasingly powerful in recent years. Programs exploring the advantages of this architecture could achieve large performance gains and this is the aim of new initiatives in high performance computing. The objective of this work is to develop an efficient tool to model 2D elastic wave propagation on parallel computing devices. To this end, we implement the elastodynamic finite integration technique, using the industry open standard open computing language (OpenCL) for cross-platform, parallel programming of modern processors, and an open-source toolkit called [Py]OpenCL. The code written with [Py]OpenCL can run on a wide variety of platforms; it can be used on AMD or NVIDIA GPUs as well as classical multicore CPUs, adapting to the underlying architecture. Our main contribution is its implementation with local and global memory and the performance analysis using five different computing devices (including Kepler, one of the fastest and most efficient high performance computing technologies) with various operating systems.
Modeling of two-storey precast school building using Ruaumoko 2D program
Energy Technology Data Exchange (ETDEWEB)
Hamid, N. H.; Tarmizi, L. H.; Ghani, K. D. [Faculty of Civil Engineering, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia)
2015-05-15
The long-distant earthquake loading from Sumatra and Java Island had caused some slight damages to precast and reinforced concrete buildings in West Malaysia such as cracks on wall panels, columns and beams. Subsequently, the safety of existing precast concrete building is needed to be analyzed because these buildings were designed using BS 8110 which did not include the seismic loading in the design. Thus, this paper emphasizes on the seismic performance and dynamic behavior of precast school building constructed in Malaysia under three selected past earthquakes excitations ; El Centro 1940 North-South, El Centro East-West components and San Fernando 1971 using RUAUMOKO 2D program. This program is fully utilized by using prototype precast school model and dynamic non-linear time history analysis. From the results, it can be concluded that two-storey precast school building has experienced severe damage and partial collapse especially at beam-column joint under San Fernando and El Centro North-South Earthquake as its exceeds the allowable inter-storey drift and displacement as specified in Eurocode 8. The San Fernando earthquake has produced a massive destruction to the precast building under viscous damping, ξ = 5% and this building has generated maximum building displacement of 435mm, maximum building drift of 0.68% and maximum bending moment at 8458kNm.
Stability of superfluid phases in the 2D spin-polarized attractive Hubbard model
Kujawa-Cichy, A.; Micnas, R.
2011-08-01
We study the evolution from the weak coupling (BCS-like limit) to the strong coupling limit of tightly bound local pairs (LPs) with increasing attraction, in the presence of the Zeeman magnetic field (h) for d=2, within the spin-polarized attractive Hubbard model. The broken symmetry Hartree approximation as well as the strong coupling expansion are used. We also apply the Kosterlitz-Thouless (KT) scenario to determine the phase coherence temperatures. For spin-independent hopping integrals (t↑=t↓), we find no stable homogeneous polarized superfluid (SCM) state in the ground state for the strong attraction and obtain that for a two-component Fermi system on a 2D lattice with population imbalance, phase separation (PS) is favoured for a fixed particle concentration, even on the LP (BEC) side. We also examine the influence of spin-dependent hopping integrals (mass imbalance) on the stability of the SCM phase. We find a topological quantum phase transition (Lifshitz type) from the unpolarized superfluid phase (SC0) to SCM and tricritical points in the h-|U| and t↑/t↓-|U| ground-state phase diagrams. We also construct the finite temperature phase diagrams for both t↑=t↓ and t↑≠t↓ and analyze the possibility of occurrence of a spin-polarized KT superfluid.
2D BEM modeling of a singular thermal diffusion free boundary problem with phase change
Nikolayev, Vadim
2016-01-01
We report a 2D Boundary Element Method (BEM) modeling of the thermal diffusion-controlled growth of a vapor bubble attached to a heating surface during saturated pool boiling. The transient heat conduction problem is solved in a liquid that surrounds a bubble with a free boundary and in a semi-infinite solid heater. The heat generated homogeneously in the heater causes evaporation, i. e. the bubble growth. A singularity exists at the point of the triple (liquid-vapor-solid) contact. At high system pressure the bubble is assumed to grow slowly, its shape being defined by the surface tension and the vapor recoil force, a force coming from the liquid evaporating into the bubble. It is shown that at some typical time the dry spot under the bubble begins to grow rapidly under the action of the vapor recoil. Such a bubble can eventually spread into a vapor film that can separate the liquid from the heater, thus triggering the boiling crisis (Critical Heat Flux phenomenon).
D Recording for 2d Delivering - the Employment of 3d Models for Studies and Analyses -
Rizzi, A.; Baratti, G.; Jiménez, B.; Girardi, S.; Remondino, F.
2011-09-01
In the last years, thanks to the advances of surveying sensors and techniques, many heritage sites could be accurately replicated in digital form with very detailed and impressive results. The actual limits are mainly related to hardware capabilities, computation time and low performance of personal computer. Often, the produced models are not visible on a normal computer and the only solution to easily visualized them is offline using rendered videos. This kind of 3D representations is useful for digital conservation, divulgation purposes or virtual tourism where people can visit places otherwise closed for preservation or security reasons. But many more potentialities and possible applications are available using a 3D model. The problem is the ability to handle 3D data as without adequate knowledge this information is reduced to standard 2D data. This article presents some surveying and 3D modeling experiences within the APSAT project ("Ambiente e Paesaggi dei Siti d'Altura Trentini", i.e. Environment and Landscapes of Upland Sites in Trentino). APSAT is a multidisciplinary project funded by the Autonomous Province of Trento (Italy) with the aim documenting, surveying, studying, analysing and preserving mountainous and hill-top heritage sites located in the region. The project focuses on theoretical, methodological and technological aspects of the archaeological investigation of mountain landscape, considered as the product of sequences of settlements, parcelling-outs, communication networks, resources, and symbolic places. The mountain environment preserves better than others the traces of hunting and gathering, breeding, agricultural, metallurgical, symbolic activities characterised by different lengths and environmental impacts, from Prehistory to the Modern Period. Therefore the correct surveying and documentation of this heritage sites and material is very important. Within the project, the 3DOM unit of FBK is delivering all the surveying and 3D material to
Modeling Cellular Networks with Full Duplex D2D Communication: A Stochastic Geometry Approach
Ali, Konpal S.
2016-08-24
Full-duplex (FD) communication is optimistically promoted to double the spectral efficiency if sufficient self-interference cancellation (SIC) is achieved. However, this is not true when deploying FD-communication in a large-scale setup due to the induced mutual interference. Therefore, a large-scale study is necessary to draw legitimate conclusions about gains associated with FD-communication. This paper studies the FD operation for underlay device-to-device (D2D) communication sharing the uplink resources in cellular networks. We propose a disjoint fine-tuned selection criterion for the D2D and FD modes of operation. Then, we develop a tractable analytical paradigm, based on stochastic geometry, to calculate the outage probability and rate for cellular and D2D users. The results reveal that even in the case of perfect SIC, due to the increased interference injected to the network by FD-D2D communication, having all proximity UEs transmit in FD-D2D is not beneficial for the network. However, if the system parameters are carefully tuned, non-trivial network spectral-efficiency gains (64% shown) can be harvested. We also investigate the effects of imperfect SIC and D2D-link distance distribution on the harvested FD gains.
Dynamical Models of SAURON and CALIFA Galaxies: 1D and 2D Rotational Curves
Kalinova, Veselina; van de Ven, G.; Lyubenova, M.; Falcon-Barroso, J.; van den Bosch, R.
2013-01-01
The mass of a galaxy is the most important parameter to understand its structure and evolution. The total mass we can infer by constructing dynamical models that fit the motion of the stars and gas in the galaxy. The dark matter content then follows after subtracting the luminous matter inferred from colors and/or spectra. Here, we present the mass distribution of a sample of 18 late-type spiral (Sb-Sd) galaxies, using two-dimensional stellar kinematics obtained with the integral-field spectrograph SAURON. The observed second order velocity moments of these galaxies are fitted with solutions of the Axisymmetric Jeans equations and give us an accurate estimation of the mass-to-light ratio profiles and rotational curves. The rotation curves of the galaxies are obtained by the Asymmetric Drift Correction (ADC) and Multi-Gaussian Expansion (MGE) methods, corresponding to one- and two-dimensional mass distribution. Their comparison shows that the mass distribution based on the 2D stellar kinematics is much more reliable than 1D one. SAURON integral field of view looks at the inner parts of the galaxies in contrast with CALIFA survey. CALIFA survey provides PMAS/PPAK integral-field spectroscopic data of ~ 600 nearby galaxies as part of the Calar Alto Legacy Integral Field Area. We show the first CALIFA dynamical models of different morphological type of galaxies, giving the clue about the mass distribution of galaxies through the whole Hubble sequence and their evolution from the blue cloud to the red sequence.
Shen, D.; Wang, J.; Cheng, X.; Rui, Y.; Ye, S.
2015-08-01
The rapid progress of lidar technology has made the acquirement and application of high-resolution digital elevation model (DEM) data increasingly popular, especially in regards to the study of floodplain flow. However, high-resolution DEM data pose several disadvantages for floodplain modeling studies; e.g., the data sets contain many redundant interpolation points, large numbers of calculations are required to work with data, and the data do not match the size of the computational mesh. Two-dimensional (2-D) hydraulic modeling, which is a popular method for analyzing floodplain flow, offers highly precise elevation parameterization for computational mesh while ignoring much of the micro-topographic information of the DEM data itself. We offer a flood simulation method that integrates 2-D hydraulic model results and high-resolution DEM data, thus enabling the calculation of flood water levels in DEM grid cells through local inverse distance-weighted interpolation. To get rid of the false inundation areas during interpolation, it employs the run-length encoding method to mark the inundated DEM grid cells and determine the real inundation areas through the run-length boundary tracing technique, which solves the complicated problem of connectivity between DEM grid cells. We constructed a 2-D hydraulic model for the Gongshuangcha detention basin, which is a flood storage area of Dongting Lake in China, by using our integrated method to simulate the floodplain flow. The results demonstrate that this method can solve DEM associated problems efficiently and simulate flooding processes with greater accuracy than simulations only with DEM.
Building a 2.5D Digital Elevation Model from 2D Imagery
Padgett, Curtis W.; Ansar, Adnan I.; Brennan, Shane; Cheng, Yang; Clouse, Daniel S.; Almeida, Eduardo
2013-01-01
When projecting imagery into a georeferenced coordinate frame, one needs to have some model of the geographical region that is being projected to. This model can sometimes be a simple geometrical curve, such as an ellipse or even a plane. However, to obtain accurate projections, one needs to have a more sophisticated model that encodes the undulations in the terrain including things like mountains, valleys, and even manmade structures. The product that is often used for this purpose is a Digital Elevation Model (DEM). The technology presented here generates a high-quality DEM from a collection of 2D images taken from multiple viewpoints, plus pose data for each of the images and a camera model for the sensor. The technology assumes that the images are all of the same region of the environment. The pose data for each image is used as an initial estimate of the geometric relationship between the images, but the pose data is often noisy and not of sufficient quality to build a high-quality DEM. Therefore, the source imagery is passed through a feature-tracking algorithm and multi-plane-homography algorithm, which refine the geometric transforms between images. The images and their refined poses are then passed to a stereo algorithm, which generates dense 3D data for each image in the sequence. The 3D data from each image is then placed into a consistent coordinate frame and passed to a routine that divides the coordinate frame into a number of cells. The 3D points that fall into each cell are collected, and basic statistics are applied to determine the elevation of that cell. The result of this step is a DEM that is in an arbitrary coordinate frame. This DEM is then filtered and smoothed in order to remove small artifacts. The final step in the algorithm is to take the initial DEM and rotate and translate it to be in the world coordinate frame [such as UTM (Universal Transverse Mercator), MGRS (Military Grid Reference System), or geodetic] such that it can be saved in
Modelling thermal stratification in the North Sea: Application of a 2-D potential energy model
DEFF Research Database (Denmark)
Nielsen, Morten Holtegaard; St. John, Michael
2001-01-01
energy as water masses of different densities are mixed in the field of gravity. A constant ratio between the gain in potential energy and the production of TKE is assumed, known as the flux Richardson number. The model is comprised of 0·5m vertical layers with a temporal time step of 1 day. The model...... is forced with wind, dew point temperature from Ekofisk oilfield in the central North Sea, and tidal current and atmospheric radiation. The model is used to simulate the seasonal cycle of stratification in the central North Sea in the years 1988, 1989 and 1990 and is compared to density profiles...... an R2=0·97 between observed and predicted upper layer temperatures. However, the model is less successful in the prediction of temperatures of the intermediate and deep layers (R2=0·46 and 0·14) due to small deviations in thermocline depth and variations in tidal amplitude. The model was then applied...
Multi-objective optimisation of cost-benefit of urban flood management using a 1D2D coupled model.
Delelegn, S W; Pathirana, A; Gersonius, B; Adeogun, A G; Vairavamoorthy, K
2011-01-01
This paper presents a multi-objective optimisation (MOO) tool for urban drainage management that is based on a 1D2D coupled model of SWMM5 (1D sub-surface flow model) and BreZo (2D surface flow model). This coupled model is linked with NSGA-II, which is an Evolutionary Algorithm-based optimiser. Previously the combination of a surface/sub-surface flow model and evolutionary optimisation has been considered to be infeasible due to the computational demands. The 1D2D coupled model used here shows a computational efficiency that is acceptable for optimisation. This technological advance is the result of the application of a triangular irregular discretisation process and an explicit finite volume solver in the 2D surface flow model. Besides that, OpenMP based parallelisation was employed at optimiser level to further improve the computational speed of the MOO tool. The MOO tool has been applied to an existing sewer network in West Garforth, UK. This application demonstrates the advantages of using multi-objective optimisation by providing an easy-to-comprehend Pareto-optimal front (relating investment cost to expected flood damage) that could be used for decision making processes, without repeatedly going through the modelling-optimisation stage.
DEFF Research Database (Denmark)
Lindhardt Johansen, Marie; Hagen, Casper P; Rajpert-De Meyts, Ewa;
2012-01-01
Most previous studies of 45,X/46,XY mosaicism are case reports or have described single aspects of the disease.......Most previous studies of 45,X/46,XY mosaicism are case reports or have described single aspects of the disease....
2009-09-01
28 2.3 Delfin and Finel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 2.4 ELCIRC and...Designed for coastal oceans, shelves, estuaries, inlets, floodplains, rivers and beaches Delfin FV/FD ELCIRC Eularian-Lagrangian CIRCu- lation model FV/FD...NOAA’s National Ocean Services for storm surge/inundation applications. 2.3 Delfin and Finel Delfin was developed by D. Ham under the supervision of J
Hamerly, Ryan; Inagaki, Takahiro; Takesue, Hiroki; Yamamoto, Yoshihisa; Mabuchi, Hideo
2016-01-01
A network of optical parametric oscillators is used to simulate classical Ising and XY spin chains. The collective nonlinear dynamics of this network, driven by quantum noise rather than thermal fluctuations, seeks out the Ising / XY ground state as the system transitions from below to above the lasing threshold. We study the behavior of this "Ising machine" for three canonical problems: a 1D ferromagnetic spin chain, a 2D square lattice, and problems where next-nearest-neighbor couplings give rise to frustration. If the pump turn-on time is finite, topological defects form (domain walls for the Ising model, winding number and vortices for XY) and their density can be predicted from a numerical model involving a linear "growth stage" and a nonlinear "saturation stage". These predictions are compared against recent data for a 10,000-spin 1D Ising machine.
Hamerly, Ryan; Inaba, Kensuke; Inagaki, Takahiro; Takesue, Hiroki; Yamamoto, Yoshihisa; Mabuchi, Hideo
2016-09-01
A network of optical parametric oscillators (OPOs) is used to simulate classical Ising and XY spin chains. The collective nonlinear dynamics of this network, driven by quantum noise rather than thermal fluctuations, seeks out the Ising/XY ground state as the system transitions from below to above the lasing threshold. We study the behavior of this “Ising machine” for three canonical problems: a 1D ferromagnetic spin chain, a 2D square lattice and problems where next-nearest-neighbor couplings give rise to frustration. If the pump turn-on time is finite, topological defects form (domain walls for the Ising model, winding number and vortices for XY) and their density can be predicted from a numerical model involving a linear “growth stage” and a nonlinear “saturation stage”. These predictions are compared against recent data for a 10,000-spin 1D Ising machine.
Directory of Open Access Journals (Sweden)
F. Tornabene
2016-01-01
Full Text Available The cylindrical bending condition for structural models is very common in the literature because it allows an incisive and simple verification of the proposed plate and shell models. In the present paper, 2D numerical approaches (the Generalized Differential Quadrature (GDQ and the finite element (FE methods are compared with an exact 3D shell solution in the case of free vibrations of functionally graded material (FGM plates and shells. The first 18 vibration modes carried out through the 3D exact model are compared with the frequencies obtained via the 2D numerical models. All the 18 frequencies obtained via the 3D exact model are computed when the structures have simply supported boundary conditions for all the edges. If the same boundary conditions are used in the 2D numerical models, some modes are missed. Some of these missed modes can be obtained modifying the boundary conditions imposing free edges through the direction perpendicular to the direction of cylindrical bending. However, some modes cannot be calculated via the 2D numerical models even when the boundary conditions are modified because the cylindrical bending requirements cannot be imposed for numerical solutions in the curvilinear edges by definition. These features are investigated in the present paper for different geometries (plates, cylinders, and cylindrical shells, types of FGM law, lamination sequences, and thickness ratios.
Yoshida, Risa; Kimoto, Tomoyuki; Uezu, Tatsuya
2017-03-01
We analyze the structure of attractors in the classical XY model with an associative-memory-type interaction by the statistical mechanical method. Previously, it was found that when patterns are uncorrelated, points on a path connecting two memory patterns in the space of the order parameters are solutions of the saddle point equations (SPEs) in the case that p is O(1) irrespective of N and N ≫ 1, where p and N are the numbers of patterns and spins, respectively. This state is called the continuous attractor (CA). In this paper, we clarify the conditions for the existence and stability of the CA with and without the correlation a (0 ≤ a 0, we numerically study the case that patterns are subject to external noise and find that pc increases as the noise amplitude increases.
DEFF Research Database (Denmark)
Bhaskar, Mahajan Sagar; Sanjeevikumar, Padmanaban; Wheeler, Patrick
2016-01-01
A New breed of a buck boost converter, named as the XY converter family is proposed in this article. In the XY family, 16 topologies are presented which are highly suitable for renewable energy applications which require a high ratio of DC-DC converter; such as a photovoltaic multilevel inverter...... system, high voltage automotive applications and industrial drives. Compared to the traditional boost converter and existing recent converters, the proposed XY converter family has the ability to provide a higher output voltage by using less number of power devices and reactive components. Other distinct...... features of the XY converter family are i) Single control switch ii) Provide negative output voltage iii) Non-isolated topologies iv) High conversion ratio without making the use of high duty cycle and v) modular structure. XY family is compared with the recent high step-up converters and the detailed...
Straatsma, M.W.; Huthoff, F.
2011-01-01
In The Netherlands, 2D-hydrodynamic simulations are used to evaluate the effect of potential safety measures against river floods. In the investigated scenarios, the floodplains are completely inundated, thus requiring realistic representations of hydraulic roughness of floodplain vegetation. The cu
Correspondenceless 3D-2D registration based on expectation conditional maximization
Kang, X.; Taylor, R. H.; Armand, M.; Otake, Y.; Yau, W. P.; Cheung, P. Y. S.; Hu, Y.
2011-03-01
3D-2D registration is a fundamental task in image guided interventions. Due to the physics of the X-ray imaging, however, traditional point based methods meet new challenges, where the local point features are indistinguishable, creating difficulties in establishing correspondence between 2D image feature points and 3D model points. In this paper, we propose a novel method to accomplish 3D-2D registration without known correspondences. Given a set of 3D and 2D unmatched points, this is achieved by introducing correspondence probabilities that we model as a mixture model. By casting it into the expectation conditional maximization framework, without establishing one-to-one point correspondences, we can iteratively refine the registration parameters. The method has been tested on 100 real X-ray images. The experiments showed that the proposed method accurately estimated the rotations (< 1°) and in-plane (X-Y plane) translations (< 1 mm).
The 2005 Vazcun Valley Lahar: Evaluation of the TITAN2D Two-Phase Flow Model Using an Actual Event.
Williams, R.; Stinton, A. J.; Sheridan, M. F.
2005-12-01
TITAN2D is a depth-averaged, thin-layer computational fluid dynamics (CFD) code, suitable for simulating a variety of geophysical mass flows. TITAN2D output data include pile thickness and flow momentum at each time step for all cells traversed by the flow during the simulation. From this the flow limit, run-out path, pile velocity, deposit thickness, and travel time can be calculated. Results can be visualized in the open source GRASS GIS software or with the built-in TITAN2D viewer. A new two-phase TITAN2D version allows simulation of flows containing various mixtures of water and solids. The purpose of this study is to compare simulations by the two-phase flow version of TITAN2D with an actual event. The chosen natural flow is a small ash-rich lahar (volume approximately 60,000 m3) that occurred on 12 February 2005 in the Vazcún Valley, located on the north-east flank of Volcán Tungurahua, Ecuador. Lahars and pyroclastic flows along this valley could potentially threaten the 20,000 inhabitants living in and near the city of Baños. A variety of data sources exist for this lahar, including: pre- and post-event meter-scale topography, and photographic, video, seismic and acoustic flow monitoring (AFM) records from during the event. These data permit detailed comparisons between the dynamics of the actual lahar and those of the TITAN2D simulated flow. In particular, detailed comparisons are made between run-up heights, flow velocity, inundation area, and deposit area and thickness. Simulations utilize a variety of data derived from field observations such as lahar volume, solid to pore-fluid ratio and pre-event topography. TITAN2D is important in modeling lahars because it allows assessment of the impact of the flows on buildings and infrastructure lifelines located near drainages that descend from volcanoes.
Comparison of the 1D flux theory with a 2D hydrodynamic secondary settling tank model.
Ekama, G A; Marais, P
2004-01-01
The applicability of the 1D idealized flux theory (1DFT) for design of secondary settling tanks (SSTs) is evaluated by comparing its predicted maximum surface overflow (SOR) and solids loading (SLR) rates with that calculated from the 2D hydrodynamic model SettlerCAD using as a basis 35 full scale SST stress tests conducted on different SSTs with diameters from 30 to 45m and 2.25 to 4.1 m side water depth, with and without Stamford baffles. From the simulations, a relatively consistent pattern appeared, i.e. that the 1DFT can be used for design but its predicted maximum SLR needs to be reduced by an appropriate flux rating, the magnitude of which depends mainly on SST depth and hydraulic loading rate (HLR). Simulations of the sloping bottom shallow (1.5-2.5 m SWD) Dutch SSTs tested by STOWa and the Watts et al. SST, all with doubled SWDs, and the Darvill new (4.1 m) and old (2.5 m) SSTs with interchanged depths, were run to confirm the sensitivity of the flux rating to depth and HLR. Simulations with and without a Stamford baffle were also done. While the design of the internal features of the SST, such as baffling, have a marked influence on the effluent SS concentration for underloaded SSTs, these features appeared to have only a small influence on the flux rating, i.e. capacity, of the SST, In the meantime until more information is obtained, it would appear that from the simulations so far that the flux rating of 0.80 of the 1DFT maximum SLR recommended by Ekama and Marais remains a reasonable value to apply in the design of full scale SSTs--for deep SSTs (4 m SWD) the flux rating could be increased to 0.85 and for shallow SSTs (2.5 m SWD) decreased to 0.75. It is recommended that (i) while the apparent interrelationship between SST flux rating and depth suggests some optimization of the volume of the SST, that this be avoided and that (ii) the depth of the SST be designed independently of the surface area as is usually the practice and once selected, the
A new approach to river bank retreat and advance in 2D numerical models of fluvial morphodynamics
Spruyt, A.; Mosselman, E.; Jagers, B.
2011-01-01
River bank retreat and advance are modes of morphological evolution in addition to bed level changes and changes in bed sediment composition. They produce planform changes such as width adjustment and meander bend migration. However, their reproduction in a 2D numerical model still remains a challen
W. J. Goedheer,; Meijer, P. M.; Bezemer, J.; Passchier, J. D. P.; van Sark, Wgjhm
1995-01-01
The results of a 2-D fluid model for argon radiofrequency (RF) discharges in a closed cylindrical vacuum chamber are compared with experimental data from an amorphous silicon deposition reactor operated in argon. Good agreement is obtained for the relation between the DC autobias voltage and the dis
Novel Method Fusing (2D) 2 LDA with Multichannel Model for Face Recognition
Institute of Scientific and Technical Information of China (English)
Xia Liu∗; Yang Cao; Yu Cao; Bo Wang
2015-01-01
A fusion method of Gabor features and (2D)2LDA for face feature extraction is proposed in this paper. Gabor filters are utilized to extract multi⁃direction and multi⁃scale features from facial image to employ its robust performance for illumination, expressional variability and other factors. The extracted features have the defect of high dimension and redundancy data. (2D)2LDA is implemented to reduce the dimension of Gabor features and select effective feature data. Finally, the nearest neighbor classifier is used to classify characteristics and complete face recognition. The experiments are implemented by using ORL database and Yale database respectively. The experimental results show that the proposed method significantly reduces the dimension of Gabor features and decrease the influence of other factors. The proposed method acquires excellent recognition accuracy and has light architectures as well.
MOD_FreeSurf2D: a Surface Fluid Flow Simulation Model for Rivers, Streams, and Shallow Estuaries
Martin, N.; Gorelick, S. M.
2003-12-01
The MOD_FreeSurf2D, Modular Free Surface Flow in Two-Dimensions, computer model simulates free surface fluid flow in streams, rivers, and shallow estuaries under the assumptions of a well-mixed water column, a small water depth to width ratio, and a hydrostatic pressure distribution. The dependent variables in the model are free surface elevation, which provides total water depth, and fluid velocity. Primary advantages of MOD_FreeSurf2D relative to other two-dimensional models are a stable and computationally efficient numerical representation and a transparent representation of wetting and drying of the simulation domain. MOD_FreeSurf2D approximates the depth-averaged, shallow water equations with a finite volume, semi-implicit, semi-Lagrangian numerical representation similar to the TRIM method (Casulli, 1990; Casulli and Cheng, 1992; Casulli, 1999). The semi-implicit, semi-Lagrangian approach is computationally efficient because time steps can exceed the Courant-Friedrich-Lewy (CFL) stability criterion without significant accuracy degradation (Robert, 1982; Casulli, 1990). The rectangular, Arakawa C-grid, finite-volume layout allows flooding and drying in response to changing flow conditions without prior channel specification or closed boundary specification. Open boundary conditions available in MOD_FreeSurf2D are specified flux, specified total water depth, specified velocity, radiation free surface, and radiation velocity. MOD_FreeSurf2D requires initial topography, undisturbed water depth, and Manning's roughness coefficient. MOD_FreeSurf2D simulated results are shown to converge to the semi-empirical solution for a simple straight channel case. Two applications demonstrate the accuracy of MOD_FreeSurf2D. The first application is the evolution of water depth in the dambreak-style flume experiment of Bellos et al. (1992). In this case, MOD_FreeSurf2D accurately simulates the changing water depth in the flume during the experiment and models the wetting of
Matrix Models of 2D String Theory in Non--trivial Backgrounds
Koetsier, Arnaud
2005-01-01
After a brief review of critical string theory in trivial backgrounds we begin with introduction to strings in non--trivial backgrounds and noncritical string theory. In particular, we relate the latter to critical string theory in a linear dilaton background. We then show how a black hole background arises from 2D string theory and discuss some of its properties. A time--dependant tachyon background is constructed by perturbing the CFT describing string theory in a linear dilaton background....
Reference measurements on a Francis model turbine with 2D Laser-Doppler-Anemometry
Frey, A.; Kirschner, O.; Riedelbauch, S.; Jester-Zuerker, R.; Jung, A.
2016-11-01
To validate the investigations of a high-resolution CFD simulation of a Francis turbine, measurements with 2D Laser-Doppler-Anemometry are carried out. The turbine is operated in part load, where a rotating vortex rope occurs. To validate both, mean velocities and velocity fluctuations, the measurements are classified relative to the vortex rope position. Several acrylic glass windows are installed in the turbine walls such as upstream of the spiral case inlet, in the vaneless space and in the draft tube. The current investigation is focused on a measurement plane below the runner. 2D velocity components are measured on this whole plane by measuring several narrow spaced radial lines. To avoid optical refraction of the laser beam a plan parallel window is inserted in the cone wall. The laser probe is positioned with a 2D traverse system consisting of a circumferential rail and a radial aligned linear traverse. The velocity data are synchronized with the rotational frequency of the rotating vortex rope. The results of one measurement line show the dependency of the axial and circumferential velocities on the vortex rope position.
Fang, F.; Zhang, T.; Pavlidis, D.; Pain, C. C.; Buchan, A. G.; Navon, I. M.
2014-10-01
A novel reduced order model (ROM) based on proper orthogonal decomposition (POD) has been developed for a finite-element (FE) adaptive mesh air pollution model. A quadratic expansion of the non-linear terms is employed to ensure the method remained efficient. This is the first time such an approach has been applied to air pollution LES turbulent simulation through three dimensional landscapes. The novelty of this work also includes POD's application within a FE-LES turbulence model that uses adaptive resolution. The accuracy of the reduced order model is assessed and validated for a range of 2D and 3D urban street canyon flow problems. By comparing the POD solutions against the fine detail solutions obtained from the full FE model it is shown that the accuracy is maintained, where fine details of the air flows are captured, whilst the computational requirements are reduced. In the examples presented below the size of the reduced order models is reduced by factors up to 2400 in comparison to the full FE model while the CPU time is reduced by up to 98% of that required by the full model.
2D MHD AND 1D HD MODELS OF A SOLAR FLARE—A COMPREHENSIVE COMPARISON OF THE RESULTS
Energy Technology Data Exchange (ETDEWEB)
Falewicz, R.; Rudawy, P. [Astronomical Institute, University of Wrocław, 51-622 Wrocław, ul. Kopernika 11 (Poland); Murawski, K. [Group of Astrophysics, UMCS, ul. Radziszewskiego 10, 20-031 Lublin (Poland); Srivastava, A. K., E-mail: falewicz@astro.uni.wroc.pl, E-mail: rudawy@astro.uni.wroc.pl, E-mail: kmur@kft.umcs.lublin.pl, E-mail: asrivastava.app@iitbhu.ac.in [Department of Physics, Indian Institute of Technology (Banaras Hindu University), Varanasi-221005 (India)
2015-11-01
Without any doubt, solar flaring loops possess a multithread internal structure that is poorly resolved, and there are no means to observe heating episodes and thermodynamic evolution of the individual threads. These limitations cause fundamental problems in numerical modeling of flaring loops, such as selection of a structure and a number of threads, and an implementation of a proper model of the energy deposition process. A set of one-dimensional (1D) hydrodynamic and two-dimensional (2D) magnetohydrodynamic models of a flaring loop are developed to compare energy redistribution and plasma dynamics in the course of a prototypical solar flare. Basic parameters of the modeled loop are set according to the progenitor M1.8 flare recorded in AR 10126 on 2002 September 20 between 09:21 UT and 09:50 UT. The nonideal 1D models include thermal conduction and radiative losses of the optically thin plasma as energy-loss mechanisms, while the nonideal 2D models take into account viscosity and thermal conduction as energy-loss mechanisms only. The 2D models have a continuous distribution of the parameters of the plasma across the loop and are powered by varying in time and space along and across the loop heating flux. We show that such 2D models are an extreme borderline case of a multithread internal structure of the flaring loop, with a filling factor equal to 1. Nevertheless, these simple models ensure the general correctness of the obtained results and can be adopted as a correct approximation of the real flaring structures.
A new approach for assimilation of 2D radar precipitation in a high-resolution NWP model
DEFF Research Database (Denmark)
Korsholm, Ulrik Smith; Petersen, Claus; Sass, Bent Hansen;
2015-01-01
A new approach for assimilation of 2D precipitation in numerical weather prediction models is presented and tested in a case with convective, heavy precipitation. In the scheme a nudging term is added to the horizontal velocity divergence tendency equation. In case of underproduction of precipita......A new approach for assimilation of 2D precipitation in numerical weather prediction models is presented and tested in a case with convective, heavy precipitation. In the scheme a nudging term is added to the horizontal velocity divergence tendency equation. In case of underproduction...... of precipitation, the strength of the nudging is proportional to the offset between observed and modelled precipitation, leading to increased moisture convergence. If the model over-predicts precipitation, the low level moisture source is reduced, and in-cloud moisture is nudged towards environmental values...
Simulating floods : On the application of a 2D-hydraulic model for flood hazard and risk assessment
Alkema, D.
2007-01-01
Over the last decades, river floods in Europe seem to occur more frequently and are causing more and more economic and emotional damage. Understanding the processes causing flooding and the development of simulation models to evaluate countermeasures to control that damage are important issues. This study deals with the application of a 2D hydraulic flood propagation model for flood hazard and risk assessment. It focuses on two components: 1) how well does it predict the spatial-dynamic chara...
Comparison between a 1D and a 2D numerical model of an active magnetic regenerative refrigerator
DEFF Research Database (Denmark)
Petersen, Thomas Frank; Engelbrecht, Kurt; Bahl, Christian Robert Haffenden;
2008-01-01
a reciprocating AMR and can determine the cyclical steady-state temperature profile of the system as well as performance parameters such as the refrigeration capacity, the work input and the coefficient of performance (COP). The models are used to analyse an AMR with a regenerator made of flat parallel plates...... results of overall results such as the refrigeration capacity but that a 2D model is required for a detailed analysis of the phenomena occurring inside the AMR....
Lehto, N J; Sochaczewski, L; Davison, W; Tych, W; Zhang, H
2008-03-01
Diffusive gradients in thin films (DGT) is a dynamic, in situ measuring technique that can be used to supply diverse information on concentrations and behaviour of solutes. When deployed in soils and sediments, quantitative interpretation of DGT measurements requires the use of a numerical model. An improved version of the DGT induced fluxes in soils and sediments model (DIFS), working in two dimensions (2D DIFS), was used to investigate the accuracy with which DGT measurements can be used to estimate the distribution coefficient for labile metal (KD) and the response time of the soil to depletion (TC). The 2D DIFS model was used to obtain values of KD and TC for Cd, Zn and Ni in three different soils, which were compared to values determined previously using 1D DIFS for these cases. While the 1D model was shown to provide reasonable estimates of KD, the 2D model refined the estimates of the kinetic parameters. Desorption rate constants were shown to be similar for all three metals and lower than previously thought. Calculation of an error function as KD and TC are systematically varied showed the spread of KD and TC values that fit the experimental data equally well. These automatically generated error maps reflected the quality of the data and provided an appraisal of the accuracy of parameter estimation. They showed that in some cases parameter accuracy could be improved by fitting the model to a sub-set of data.
Directory of Open Access Journals (Sweden)
Guoqing Zhou
2016-06-01
Full Text Available This paper proposes a novel rigorous transformation model for 2D-3D registration to address the difficult problem of obtaining a sufficient number of well-distributed ground control points (GCPs in urban areas with tall buildings. The proposed model applies two types of geometric constraints, co-planarity and perpendicularity, to the conventional photogrammetric collinearity model. Both types of geometric information are directly obtained from geometric building structures, with which the geometric constraints are automatically created and combined into the conventional transformation model. A test field located in downtown Denver, Colorado, is used to evaluate the accuracy and reliability of the proposed method. The comparison analysis of the accuracy achieved by the proposed method and the conventional method is conducted. Experimental results demonstrated that: (1 the theoretical accuracy of the solved registration parameters can reach 0.47 pixels, whereas the other methods reach only 1.23 and 1.09 pixels; (2 the RMS values of 2D-3D registration achieved by the proposed model are only two pixels along the x and y directions, much smaller than the RMS values of the conventional model, which are approximately 10 pixels along the x and y directions. These results demonstrate that the proposed method is able to significantly improve the accuracy of 2D-3D registration with much fewer GCPs in urban areas with tall buildings.
Blitz, Celine; Komatitsch, Dimitri; Lognonné, Philippe; Martin, Roland; Le Goff, Nicolas
The understanding of the interior structure of Near Earth Objects (NEOs) is a fundamental issue to determine their evolution and origin, and also, to design possible mitigation techniques (Walker and Huebner, 2004). Indeed, if an oncoming Potentially Hazardous Object (PHO) were to threaten the Earth, numerous methods are suggested to prevent it from colliding our planet. Such mitigation techniques may involve nuclear explosives on or below the object surface, impact by a projectile, or concentration of solar energy using giant mirrors (Holsapple, 2004). The energy needed in such mitigation techniques highly depends on the porosity of the hazardous threatening object (asteroid or comet), as suggested by Holsapple, 2004. Thus, for a given source, the seismic response of a coherent homogeneous asteroid should be very different from the seismic response of a fractured or rubble-pile asteroid. To assess this hypothesis, we performed numerical simulations of wave propagation in different interior models of the Near Earth Asteroid 433 Eros. The simulations of wave propagation required a shape model of asteroid Eros, kindly provided by A. Cheng and O. Barnouin-Jha (personal communication). A cross-section along the longest axis has been chosen to define our 2D geometrical model, and we study two models of the interior: a homogeneous one, and a complex one characterized by fault networks below the main crosscut craters, and covered by a regolith layer of thickness ranging from 50 m to 150 m. To perform the numerical simulations we use the spectral-element method, which solves the variational weak form of the seismic wave equation (Komatitsch and Tromp, 1999) on the meshes of the 2D models of asteroid Eros. The homogeneous model is composed of an elastic material characterized by a pressure wave velocity Vp = 3000 m.s-1 , a shear wave velocity Vs = 1700 m.s-1 and a density of 2700 kg.m-3 . The fractured model possesses the same characteristics except for the presence of
Directory of Open Access Journals (Sweden)
Sri Atmaja P. Rosidi
2007-01-01
Full Text Available The Spectral Analysis of Surface Wave (SASW method is a non-destructive in situ seismic technique used to assess and evaluate the material stiffness (dynamic elastic modulus and thickness of pavement layers at low strains. These values can be used analytically to calculate load capacities in order to predict the performance of pavement system. The SASW method is based on the dispersion phenomena of Rayleigh waves in layered media. In order to get the actual shear wave velocities, 2-D and 3-D models are used in the simulation of the inversion process for best fitting between theoretical and empirical dispersion curves. The objective of this study is to simulate and compare the 2-D and 3-D model of SASW analysis in the construction of the theoretical dispersion curve for pavement structure evaluation. The result showed that the dispersion curve from the 3-D model was similar with the dispersion curve of the actual pavement profile compared to the 2-D model. The wave velocity profiles also showed that the 3-D model used in the SASW analysis is able to detect all the distinct layers of flexible pavement units.
Institute of Scientific and Technical Information of China (English)
LI Haifeng; HU Zunhe; LIU Jingtai
2016-01-01
To facilitate scene understanding and robot navigation in large scale urban environment, a two-layer enhanced geometric map (EGMap) is designed using videos from a monocular onboard camera. The 2D layer of EGMap consists of a 2D building boundary map from top-down view and a 2D road map, which can support localization and advanced map-matching when compared with standard polyline-based maps. The 3D layer includes features such as 3D road model, and building facades with coplanar 3D vertical and horizontal line segments, which can provide the 3D metric features to localize the vehicles and flying-robots in 3D space. Starting from the 2D building boundary and road map, EGMap is initially constructed using feature fusion with geometric constraints under a line feature-based simultaneous localization and mapping (SLAM) framework iteratively and progressively. Then, a local bundle adjustment algorithm is proposed to jointly refine the camera localizations and EGMap features. Furthermore, the issues of uncertainty, memory use, time efficiency and obstacle effect in EGMap construction are discussed and analyzed. Physical experiments show that EGMap can be successfully constructed in large scale urban environment and the construction method is demonstrated to be very accurate and robust.
Müller, Peter; Messmer, Marie; Bayer, Monika; Pfeilschifter, Josef M; Hintermann, Edith; Christen, Urs
2016-05-01
Non-alcoholic fatty liver disease (NAFLD) and its more severe development non-alcoholic steatohepatitis (NASH) are increasing worldwide. In particular NASH, which is characterized by an active hepatic inflammation, has often severe consequences including progressive fibrosis, cirrhosis, and eventually hepatocellular carcinoma (HCC). Here we investigated how metabolic liver injury is influencing the pathogenesis of autoimmune hepatitis (AIH). We used the CYP2D6 mouse model in which wild type C57BL/6 mice are infected with an Adenovirus expressing the major liver autoantigen cytochrome P450 2D6 (CYP2D6). Such mice display several features of human AIH, including interface hepatitis, formation of LKM-1 antibodies and CYP2D6-specific T cells, as well as hepatic fibrosis. NAFLD was induced with a high-fat diet (HFD). We found that pre-existing NAFLD potentiates the severity of AIH. Mice fed for 12 weeks with a HFD displayed increased cellular infiltration of the liver, enhanced hepatic fibrosis and elevated numbers of liver autoantigen-specific T cells. Our data suggest that a pre-existing metabolic liver injury constitutes an additional risk for the severity of an autoimmune condition of the liver, such as AIH.
APPLICATION OF A QUASI-2D HYDRO-MORPHOLOGICAL MODEL TO THE ARGENTINEAN PARAN(A) RIVER
Institute of Scientific and Technical Information of China (English)
Pedro A.BASILE; Gerardo A.RICCARDI
2002-01-01
Herein a simplified quasi-two dimensional horizontal hydro-morphological mathematical model is presented. The governing equations for the quasi-2D horizontal time-depending flow field are represented by the well-known approach of interconnected cells. New discharge laws between cells are incorporated. The model is capable of predicting temporal changes in water depth, velocity distribution,sediment transport, bed elevation, as well as water and suspended sediment exchanges between main stream and flood plains. An application of the model to the middle reach of the Argentinean Parana River is presented. Satisfactory results were obtained during model calibration, validation and application.
Directory of Open Access Journals (Sweden)
DIEGO A. GARZÓN-ALVARADO
2012-01-01
Full Text Available Este articulo presenta distintas pruebas numéricas en dominios que presenta variación de parámetros, de forma espacial, de la ecuación de reacción- difusión en el espacio de Turing. Las pruebas son desarrolladas en cuadrados de lado unitario 2D en el cual se realizan subdivisiones (subdominios. En cada subdomminio se ingresan parámetros que corresponden a los diferentes números de onda, por lo tanto presentan un medio heterogéneo. Cada número de onda fue predicho mediante la teoría lineal de estabilidad y corresponde a diferentes patrones de Turing. La ecuación de reacción elegida es Schnakenberg. Los resultados muestran patrones complejos de bandas mixtas y puntos, además, los patrones no corresponden a los patrones originales en cada subdominio.
Modeling of Nitrate Leaching from a Potato Field using HYDRUS-2D
DEFF Research Database (Denmark)
Shekofteh, Hosein; Afyuni, Majid; Hajabbasi, Mohammad Ali;
2013-01-01
Excessive use of nitrogen (N) fertilizers is likely to be responsible for the increasing nitrate in groundwater. Thus, appropriate water and nutrient management is required to minimize groundwater pollution and to maximize the nutrient-use efficiency. In this study HYDRUS-2D software package...... was applied to simulate nitrate leaching from a drip-irrigated sandy agricultural soil for varying emitter discharges and various amounts of fertilizer. It was found that for small emitter discharge values free drainage increased significantly with increase in discharge, whereas the increase was leveled out...... at greater discharge values. Nitrate leaching increased with an increase in emitter discharge and amount of fertilizer, but the rate of increase was most significant for low emitter discharges. Based on the results, with regard to the selection of emitter discharge and the amount of appropriate fertilizer...
Spiral-driven accretion in protoplanetary discs - I. 2D models
Lesur, Geoffroy; Fromang, Sébastien
2015-01-01
We numerically investigate the dynamics of a 2D non-magnetised protoplanetary disc surrounded by an inflow coming from an external envelope. We find that the accretion shock between the disc and the inflow is unstable, leading to the generation of large-amplitude spiral density waves. These spiral waves propagate over long distances, down to radii at least ten times smaller than the accretion shock radius. We measure spiral-driven outward angular momentum transport with 1e-4 1e-8 Msun/yr. We conclude that the interaction of the disc with its envelope leads to long-lived spiral density waves and radial angular momentum transport with rates that cannot be neglected in young non-magnetised protostellar discs.
Directory of Open Access Journals (Sweden)
O. Alptekin
2005-06-01
Full Text Available The October 1, 1995 Dinar earthquake (ML=5.9 caused extensive damage within a limited area in Dinar town located in southwestern Turkey. Graben structure of the damaged area suggests the basin edge effects as a potential factor on the occurred damage. In this study numerical 2D site responses in the Dinar Graben are computed by using a finite-difference scheme and numerical results are compared with the observations within the graben. Our results suggest that the ground motions within the Dinar Graben were dominated by surface waves generated from the edges of the garben. In addition to magnifying amplitudes within the graben, the surface waves increased the duration of ground motion. Synthetic response spectra of the mainshock have shown that spectral accelerations at different sites in the graben are larger than the observed one. High spectral accelerations and long durations of ground motion may explain the extensive damage observed within the Dinar Graben.
A model of the effect of uncertainty on the C elegans L2/L2d decision.
Directory of Open Access Journals (Sweden)
Leon Avery
Full Text Available At the end of the first larval stage, the C elegans larva chooses between two developmental pathways, an L2 committed to reproductive development and an L2d, which has the option of undergoing reproductive development or entering the dauer diapause. I develop a quantitative model of this choice using mathematical tools developed for pricing financial options. The model predicts that the optimal decision must take into account not only the expected potential for reproductive growth, but also the uncertainty in that expected potential. Because the L2d has more flexibility than the L2, it is favored in unpredictable environments. I estimate that the ability to take uncertainty into account may increase reproductive value by as much as 5%, and discuss possible experimental tests for this ability.
Energy Technology Data Exchange (ETDEWEB)
Ramazani, A., E-mail: ali.ramazani@iehk.rwth-aachen.de [Department of Ferrous Metallurgy, RWTH Aachen University, Intzestr.1, D-52072 Aachen (Germany); Mukherjee, K.; Quade, H.; Prahl, U.; Bleck, W. [Department of Ferrous Metallurgy, RWTH Aachen University, Intzestr.1, D-52072 Aachen (Germany)
2013-01-10
A microstructure-based approach by means of representative volume elements (RVEs) is employed to evaluate the flow curve of DP steels using virtual tensile tests. Microstructures with different martensite fractions and morphologies are studied in two- and three-dimensional approaches. Micro sections of DP microstructures with various amounts of martensite have been converted to 2D RVEs, while 3D RVEs were constructed statistically with randomly distributed phases. A dislocation-based model is used to describe the flow curve of each ferrite and martensite phase separately as a function of carbon partitioning and microstructural features. Numerical tensile tests of RVE were carried out using the ABAQUS/Standard code to predict the flow behaviour of DP steels. It is observed that 2D plane strain modelling gives an underpredicted flow curve for DP steels, while the 3D modelling gives a quantitatively reasonable description of flow curve in comparison to the experimental data. In this work, a von Mises stress correlation factor {sigma}{sub 3D}/{sigma}{sub 2D} has been identified to compare the predicted flow curves of these two dimensionalities showing a third order polynomial relation with respect to martensite fraction and a second order polynomial relation with respect to equivalent plastic strain, respectively. The quantification of this polynomial correlation factor is performed based on laboratory-annealed DP600 chemistry with varying martensite content and it is validated for industrially produced DP qualities with various chemistry, strength level and martensite fraction.
Toward IMRT 2D dose modeling using artificial neural networks: A feasibility study
Energy Technology Data Exchange (ETDEWEB)
Kalantzis, Georgios; Vasquez-Quino, Luis A.; Zalman, Travis; Pratx, Guillem; Lei, Yu [Radiation Oncology Department, University of Texas, Health Science Center San Antonio, Texas 78229 and Radiation Oncology Department, Stanford University School of Medicine, Stanford, California 94305 (United States); Radiation Oncology Department, University of Texas, Health Science Center San Antonio, Texas 78229 (United States); Radiation Oncology Department, Stanford University School of Medicine, Stanford, California 94305 (United States); Radiation Oncology Department, University of Texas, Health Science Center San Antonio, Texas 78229 (United States)
2011-10-15
Purpose: To investigate the feasibility of artificial neural networks (ANN) to reconstruct dose maps for intensity modulated radiation treatment (IMRT) fields compared with those of the treatment planning system (TPS). Methods: An artificial feed forward neural network and the back-propagation learning algorithm have been used to replicate dose calculations of IMRT fields obtained from PINNACLE{sup 3} v9.0. The ANN was trained with fluence and dose maps of IMRT fields for 6 MV x-rays, which were obtained from the amorphous silicon (a-Si) electronic portal imaging device of Novalis TX. Those fluence distributions were imported to the TPS and the dose maps were calculated on the horizontal midpoint plane of a water equivalent homogeneous cylindrical virtual phantom. Each exported 2D dose distribution from the TPS was classified into two clusters of high and low dose regions, respectively, based on the K-means algorithm and the Euclidian metric in the fluence-dose domain. The data of each cluster were divided into two sets for the training and validation phase of the ANN, respectively. After the completion of the ANN training phase, 2D dose maps were reconstructed by the ANN and isodose distributions were created. The dose maps reconstructed by ANN were evaluated and compared with the TPS, where the mean absolute deviation of the dose and the {gamma}-index were used. Results: A good agreement between the doses calculated from the TPS and the trained ANN was achieved. In particular, an average relative dosimetric difference of 4.6% and an average {gamma}-index passing rate of 93% were obtained for low dose regions, and a dosimetric difference of 2.3% and an average {gamma}-index passing rate of 97% for high dose region. Conclusions: An artificial neural network has been developed to convert fluence maps to corresponding dose maps. The feasibility and potential of an artificial neural network to replicate complex convolution kernels in the TPS for IMRT dose calculations
Lattice Boltzmann simulations for proton transport in 2-D model channels of Nafion.
Akinaga, Yoshinobu; Hyodo, Shi-aki; Ikeshoji, Tamio
2008-10-01
Proton conductance in a 2-D channel with a slab-like structure was studied to verify that the lattice Boltzmann method (LBM) can be used as a simulation tool for proton conduction in a Nafion membrane, which is a mesoscopic system with a highly disordered porous structure. Diffusion resulting from a concentration gradient and migration by an electrostatic force were considered as the origins of proton transport. The electrostatic force acting on a proton was computed by solving the Poisson equation. The proton concentration in the membrane is expressed as a continuous function and the sulfonic charge is placed discretely. The space-averaged conductance of protons in a nonequilibrium stationary state was evaluated as a function of the structural parameters: namely, channel width and distribution of the sulfonic groups. The resulting space-averaged conductance deviates from the bulk values, depending particularly on the sulfonic group distribution. Details of the simulation scheme are described and the applicability of the present scheme to real membranes is discussed.
A novel simple procedure to consider seismic soil structure interaction effects in 2D models
Jaramillo, Juan Diego; Gómez, Juan David; Restrepo, Doriam; Rivera, Santiago
2014-09-01
A method is proposed to estimate the seismic soil-structure-interaction (SSI) effects for use in engineering practice. It is applicable to 2D structures subjected to vertically incident shear waves supported by homogenous half-spaces. The method is attractive since it keeps the simplicity of the spectral approach, overcomes some of the difficulties and inaccuracies of existing classical techniques and yet it considers a physically consistent excitation. This level of simplicity is achieved through a response spectra modification factor that can be applied to the free-field 5%-damped response spectra to yield design spectral ordinates that take into account the scattered motions introduced by the interaction effects. The modification factor is representative of the Transfer Function (TF) between the structural relative displacements and the free-field motion, which is described in terms of its maximum amplitude and associated frequency. Expressions to compute the modification factor by practicing engineers are proposed based upon a parametric study using 576 cases representative of actual structures. The method is tested in 10 cases spanning a wide range of common fundamental vibration periods.
Stability Analysis of State Saturation 2D Discrete Time-Delay Systems Based on F-M Model
Directory of Open Access Journals (Sweden)
Dongyan Chen
2013-01-01
Full Text Available The problem of stability analysis is investigated for a class of state saturation two-dimensional (2D discrete time-delay systems described by the Fornasini-Marchesini (F-M model. The delay is allowed to be a bounded time-varying function. By constructing the delay-dependent 2D discrete Lyapunov functional and introducing a nonnegative scalar β, a sufficient condition is proposed to guarantee the global asymptotic stability of the addressed systems. Subsequently, the criterion is converted into the linear matrix inequalities (LMIs which can be easily tested by using the standard numerical software. Finally, two numerical examples are given to show the effectiveness of the proposed stability criterion.
A review on 2D models for the description of pantographic fabrics
Placidi, Luca; Barchiesi, Emilio; Turco, Emilio; Rizzi, Nicola Luigi
2016-10-01
A review on models for pantographic fabrics, a new promising kind of metamaterials, is presented. We treat those models that are able to capture the peculiar effects conferred by their specific microstructure and that can be generalized for the description of more complex metamaterials. For each approach, model formulation and modeling assumptions are discussed along with the presentation of numerical solutions in exemplary cases and no attempt is made to model damage and failure phenomena.
2D soil and engineering-seismic bedrock modeling of eastern part of Izmir inner bay/Turkey
Pamuk, Eren; Akgün, Mustafa; Özdağ, Özkan Cevdet; Gönenç, Tolga
2017-02-01
Soil-bedrock models are used as a base when the earthquake-soil common behaviour is defined. Moreover, the medium which is defined as bedrock is classified as engineering and seismic bedrock in itself. In these descriptions, S-wave velocity is (Vs) used as a base. The mediums are called soil where the Vs is < 760 m/s, the bigger ones are called bedrock as well. Additionally, the parts are called engineering bedrock where the Vs is between 3000 m/s and 760 m/s, the parts where are bigger than 3000 m/s called seismic bedrock. The interfacial's horizontal topography where is between engineering and seismic bedrock is effective on earthquake's effect changing on the soil surface. That's why, 2D soil-bedrock models must be used to estimate the earthquake effect that could occur on the soil surface. In this research, surface wave methods and microgravity method were used for occuring the 2D soil-bedrock models in the east of İzmir bay. In the first stage, velocity values were obtained by the studies using surface wave methods. Then, density values were calculated from these velocity values by the help of the empiric relations. 2D soil-bedrock models were occurred based upon both Vs and changing of density by using these density values in microgravity model. When evaluating the models, it was determined that the soil is 300-400 m thickness and composed of more than one layers in parts where are especially closer to the bay. Moreover, it was observed that the soil thickness changes in the direction of N-S. In the study area, geologically, it should be thought the engineering bedrock is composed of Bornova melange and seismic bedrock unit is composed of Menderes massif. Also, according to the geophysical results, Neogene limestone and andesite units at between 200 and 400 m depth show that engineering bedrock characteristic.
Sparsity and level set regularization for diffuse optical tomography using a transport model in 2D
Prieto, Kernel; Dorn, Oliver
2017-01-01
In this paper we address an inverse problem for the time-dependent linear transport equation (or radiative transfer equation) in 2D having in mind applications in diffuse optical tomography (DOT). We propose two new reconstruction algorithms which so far have not been applied to such a situation and compare their performances in certain practically relevant situations. The first of these reconstruction algorithms uses a sparsity promoting regularization scheme, whereas the second one uses a simultaneous level set reconstruction scheme for two parameters of the linear transport equation. We will also compare the results of both schemes with a third scheme which is a more traditional L 2-based Landweber-Kaczmarz scheme. We focus our attention on the DOT application of imaging the human head of a neonate where the simpler diffusion approximation is not well-suited for the inversion due to the presence of a clear layer beneath the skull which is filled with ‘low-scattering’ cerebrospinal fluid. This layer, even if its location and characteristics are known a priori, poses significant difficulties for most reconstruction schemes due to its ‘wave-guiding’ property which reduces sensitivity of the data to the interior regions. A further complication arises due to the necessity to reconstruct simultaneously two different parameters of the linear transport equation, the scattering and the absorption cross-section, from the same data set. A significant ‘cross-talk’ between these two parameters is usually expected. Our numerical experiments indicate that each of the three considered reconstruction schemes do have their merits and perform differently but reasonably well when the clear layer is a priori known. We also demonstrate the behavior of the three algorithms in the particular situation where the clear layer is unknown during the reconstruction.
Directory of Open Access Journals (Sweden)
H. H. Gerke
2011-06-01
Full Text Available Subsurface drained experimental fields are frequently used for studying preferential flow (PF in structured soils. Considering two-dimensional (2-D transport towards the drain, however, the relevance of mass transfer coefficients, apparently reflecting small-scale soil structural properties, for the water and solute balances of the entire drained field is largely unknown. This paper reviews and analyzes effects of mass transfer reductions on Br^{−} leaching for a subsurface drained experimental field using a numerical 2-D dual-permeability model (2D-DPERM. The sensitivity of the "diffusive" mass transfer component on bromide (Br^{−} leaching patterns is discussed. Flow and transport is simulated in a 2-D vertical cross-section using parameters, boundary conditions (BC, and data of a Br^{−} tracer irrigation experiment on a subsurface drained field (5000 m^{2} area at Bokhorst (Germany, where soils have developed from glacial till sediments. The 2D-DPERM simulation scenarios assume realistic irrigation and rainfall rates, and Br-application in the soil matrix (SM domain. The mass transfer reduction controls preferential tracer movement and can be related to physical and chemical properties at the interface between flow path and soil matrix in structured soil. A reduced solute mass transfer rate coefficient allows a better match of the Br^{−} mass flow observed in the tile drain discharge. The results suggest that coefficients of water and solute transfer between PF and SM domains have a clear impact on Br^{−} effluent from the drain. Amount and composition of the drain effluent is analyzed as a highly complex interrelation between temporally and spatially variable mass transfer in the 2-D vertical flow domain that depends on varying "advective" and "diffusive" transfer components, the spatial distribution of residual tracer concentrations, and the lateral flow fields in both domains from
Directory of Open Access Journals (Sweden)
A. Ghoggal
2005-12-01
Full Text Available This paper deals mainly with the modeling of induction machine inductances by taking into account all the space harmonics, the skewing rotor bars effects and linear rise of MMF across the slot. The model is established initially in the case of symmetric machine, which corresponds to the case of a constant air-gap, then in the other case where the machine presents a static or dynamic, axial or radial eccentricity. This objective would be achieved by exploiting an extension in 2-D of the modified winding function approach (MWFA.
Leblanc, M D; Whitehead, J P; Plumer, M L
2013-05-15
A combination of Metropolis and modified Wolff cluster algorithms is used to examine the impact of uniaxial single-ion anisotropy on the phase transition to ferromagnetic order of Heisenberg macrospins on a 2D square lattice. This forms the basis of a model for granular perpendicular recording media where macrospins represent the magnetic moment of grains. The focus of this work is on the interplay between anisotropy D, intragrain exchange J' and intergrain exchange J on the ordering temperature T(C) and extends our previous reported analysis of the granular Ising model. The role of intragrain degrees of freedom in heat assisted magnetic recording is discussed.
Leblanc, M. D.; Whitehead, J. P.; Plumer, M. L.
2013-05-01
A combination of Metropolis and modified Wolff cluster algorithms is used to examine the impact of uniaxial single-ion anisotropy on the phase transition to ferromagnetic order of Heisenberg macrospins on a 2D square lattice. This forms the basis of a model for granular perpendicular recording media where macrospins represent the magnetic moment of grains. The focus of this work is on the interplay between anisotropy D, intragrain exchange J‧ and intergrain exchange J on the ordering temperature TC and extends our previous reported analysis of the granular Ising model. The role of intragrain degrees of freedom in heat assisted magnetic recording is discussed.
Lawrence-Doniach model in London approximation as a system of 2D Coulomb particles of two kinds
Energy Technology Data Exchange (ETDEWEB)
Artemov, A.N., E-mail: artemov@fti.dn.ua [Donetsk Physical and Technology Institute, Donetsk 83114 (Ukraine)
2011-12-15
We examine the Lawrence-Doniach model with Josephson coupling between layers. We represent the model as a system of 2D Coulomb particles of two kinds. The model was studied in the mean field and renormalization group approaches. The system investigated does not undergo a second order phase transition. Thermodynamical properties of layered superconductors with Josephson coupling in zero magnetic field are discussed. It is shown that the Lawrence-Doniach model of layered superconductors in the London approximation can be presented as a system of classical Coulomb particles of two kinds. This representation includes both Josephson and 2D vortex subsystems in absolutely symmetrical way. The model was analyzed by means of the real-space renormalization group approach and in the mean field approximation. It is found that there is no a second order phase transition in the system. Instead of this the model demonstrates the qualitative change of the system properties which can look as a phase transition for experimental purposes.
2D MHD and 1D HD models of a solar flare -- a comprehensive comparison of the results
Falewicz, R; Murawski, K; Srivastava, A K
2015-01-01
Without any doubt solar flaring loops possess a multi-thread internal structure that is poorly resolved and there are no means to observe heating episodes and thermodynamic evolution of the individual threads. These limitations cause fundamental problems in numerical modelling of flaring loops, such as selection of a structure and a number of threads, and an implementation of a proper model of the energy deposition process. A set of 1D hydrodynamic and 2D magnetohydrodynamic models of a flaring loop are developed to compare energy redistribution and plasma dynamics in the course of a prototypical solar flare. Basic parameters of the modeled loop are set according to the progenitor M1.8 flare recorded in the AR10126 on September 20, 2002 between 09:21 UT and 09:50 UT. The non-ideal 1D models include thermal conduction and radiative losses of the optically thin plasma as energy loss mechanisms, while the non-ideal 2D models take into account viscosity and thermal conduction as energy loss mechanisms only. The 2...
A New Cluster Updating for 2-D SU(2) × SU(2) Chiral Model
Zhang, Jianbo; Ji, Daren
1993-09-01
We propose a variant version of Wolff's cluster algorithm, which may be extended to SU(N) × SU(N) chiral model, and test it in 2-dimensional SU(2) × SU(2) chiral model. The results show that the new method can efficiently reduce the critical slowing down in SU(2) × SU(2) chiral model.
A Cluster Algorithm for the 2-D SU(3) × SU(3) Chiral Model
Ji, Da-ren; Zhang, Jian-bo
1996-07-01
To extend the cluster algorithm to SU(N) × SU(N) chiral models, a variant version of Wolff's cluster algorithm is proposed and tested for the 2-dimensional SU(3) × SU(3) chiral model. The results show that the new method can reduce the critical slowing down in SU(3) × SU(3) chiral model.
Calibration of a 1D/1D urban flood model using 1D/2D model results in the absence of field data.
Leandro, J; Djordjević, S; Chen, A S; Savić, D A; Stanić, M
2011-01-01
Recently increased flood events have been prompting researchers to improve existing coupled flood-models such as one-dimensional (1D)/1D and 1D/two-dimensional (2D) models. While 1D/1D models simulate sewer and surface networks using a one-dimensional approach, 1D/2D models represent the surface network by a two-dimensional surface grid. However their application raises two issues to urban flood modellers: (1) stormwater systems planning/emergency or risk analysis demands for fast models, and the 1D/2D computational time is prohibitive, (2) and the recognized lack of field data (e.g. Hunter et al. (2008)) causes difficulties for the calibration/validation of 1D/1D models. In this paper we propose to overcome these issues by calibrating a 1D/1D model with the results of a 1D/2D model. The flood-inundation results show that: (1) 1D/2D results can be used to calibrate faster 1D/1D models, (2) the 1D/1D model is able to map the 1D/2D flood maximum extent well, and the flooding limits satisfactorily in each time-step, (3) the 1D/1D model major differences are the instantaneous flow propagation and overestimation of the flood-depths within surface-ponds, (4) the agreement in the volume surcharged by both models is a necessary condition for the 1D surface-network validation and (5) the agreement of the manholes discharge shapes measures the fitness of the calibrated 1D surface-network.
Development of 2D dynamic model for hydrogen-fed and methane-fed solid oxide fuel cells
Luo, X. J.; Fong, K. F.
2016-10-01
A new two-dimensional (2D) dynamic model is developed in Fortran to study the mass and energy transport, the velocity field and the electrochemical phenomena of high-temperature solid oxide fuel cell (SOFC). The key feature of this model is that gas properties, reaction heat, open circuit voltage, ohmic voltage and exchange current density are temperature-dependent. Based on this, the change of gas temperature and related characteristics can be evaluated in this study. The transient performances of SOFC, like heat-up and start-up processes, are therefore assessed accordingly. In this 2D dynamic SOFC model, chemical and electrochemical reaction, flow field, mass and energy transfer models are coupled in order to determine the current density, the mass fraction and the temperature of gas species. Mass, momentum and energy balance equations are discretized by finite difference method. Performance evaluation in current density, electrical efficiency and overall efficiency is conducted for the effects of different operating parameters in SOFC. The present model can serve as a valuable tool for in-depth performance evaluation of other design and operating parameters of SOFC unit, as well as further dynamic simulation and optimization of SOFC as a prime mover in cogeneration or trigeneration system.
Is the 2D O(3) Nonlinear $\\sigma$ Model Asymptotically Free?
Patrascioiu, Adrian; Seiler, Erhard
1997-01-01
We report the results of a Monte Carlo study of the continuum limit of the two dimensional O(3) non-linear $\\sigma$ model. The notable finding is that it agrees very well with both the prediction inspired by Zamolodchikovs' S-matrix ansatz and with the continuum limit of the dodecahedron spin model. The latter finding renders the existence of asymptotic freedom in the O(3) model rather unlikely.
2-D Model Test Study of the Breakwater at Porto de Dande , Angola
DEFF Research Database (Denmark)
Andersen, Thomas Lykke; Ramirez, Jorge Robert Rodriguez; Burcharth, Hans F.
This report deals with a two-dimensional model test study of the new breakwater at Porto de Dande, Angola. One cross-section was tested for stability and overtopping in various sea conditions. The length scale used for the model tests was 1:32. Unless otherwise specified all values given in this ......This report deals with a two-dimensional model test study of the new breakwater at Porto de Dande, Angola. One cross-section was tested for stability and overtopping in various sea conditions. The length scale used for the model tests was 1:32. Unless otherwise specified all values given...
Modeling for control of an inflatable space reflector, the linear 2-D case
Voß, T.; Scherpen, J.M.A.; Edelmayer, András
2010-01-01
In this paper we develop a mathematical model for the dynamics of a linear plate with piezoelectric actuation. This model can then be used to design controllers with the goal of achieving a desired shape of the plate. This control scheme can be used for several applications, e.g., vibration control
Numerical study of the classical 2D discrete frustrated phi(4) model
Savkin, V.; Rubtsov, A.N.; Janssen, T.
2004-01-01
The two-dimensional discrete frustrated phi(4) model is studied by Monte Carlo simulations for two sets of the parameters of the model. Two phase transitions and a floating-incommensurate phase are observed for the case of stronger frustration. The phase transition from the floating-fluid phase to t
A local constitutive model with anisotropy for various homogeneous 2D biaxial deformation modes
Luding, S.; Perdahcioglu, E.S.
2011-01-01
A local constitutive model for granular materials with anisotropy is proposed and applied to different biaxial box deformation modes. The simplified version of the model (in the coordinate system of the biaxial box) involves only scalar values for hydrostatic and shear stresses, for the isotropic an
A 2D analytical multiple slip model for continuum texture development and plastic spin
Giessen, E. van der; Houtte, P. van
1992-01-01
A two-dimensional continuum slip model is presented which accounts in an approximate way for texture development in polycrystalline metals during large strain plastic deformations. The basic kinematic model is that of a rigid-plastic laminated material deforming predominantly by slip along its conta
Institute of Scientific and Technical Information of China (English)
吴修广; 沈永明; 郑永红
2004-01-01
A numerical model for shallow water flow has been developed based on the unsteady Reynolds-averaged NavierStokes equations with the hydrodynamic pressure instead of hydrostatic pressure assumption. The equations are transformed into the σ-coordinate system and the eddy viscosity is calculated with the standard k - e turbulence model. The control volume method is used to discrete the equations, and the boundary conditions at the bed for shallow water models only include vertical diffusion terms expressed with wall functions. And the semi-implicit method for pressure linked equation arithmetic is adopted to solve the equations. The model is applied to the 2D vertical plane flow of a curent over two steep-sided trenches for which experiment data are available for comparison and good agreement is obtained. And the model is used to predicting the flow in a channel with a steep-sided submerged breakwater at the bottom, and the streamline is drawn.
Filipović, Vilim; Romić, Davor; Romić, Marija; Matijević, Lana; Mallmann, Fábio J. K.; Robinson, David A.
2016-04-01
Growing vegetables commercially requires intensive management and involves high irrigation demands and input of agrochemicals. Plastic mulch application in combination with drip irrigation is a common agricultural management technique practiced due to variety of benefits to the crop, mostly vegetable biomass production. However, the use of these techniques can result in various impacts on water and nutrient distribution in underlying soil and consequently affect nutrient leaching towards groundwater resources. The aim of this work is to estimate the effect of plastic mulch cover in combination with drip irrigation on water and nitrate dynamics in soil using HYDRUS-2D model. The field site was located in Croatian costal karst area on a Gleysol (WRB). The experiment was designed according to the split-plot design in three repetitions and was divided into plots with plastic mulch cover (MULCH) and control plots with bare soil (CONT). Each of these plots received applications of three levels of nitrogen fertilizer: 70, 140, and 210 kg per ha. All plots were equipped with drip irrigation and cropped with bell pepper (Capsicum annuum L. cv. Bianca F1). Lysimeters were installed at 90 cm depth in all plots and were used for monitoring the water and nitrate outflow. HYDRUS-2D was used for modeling the water and nitrogen outflow in the MULCH and CONT plots, implementing the proper boundary conditions. HYDRUS-2D simulated results showed good fitting to the field site observed data in both cumulative water and nitrate outflow, with high level of agreement. Water flow simulations produced model efficiency of 0.84 for CONT and 0.56 for MULCH plots, while nitrate simulations showed model efficiency ranging from 0.67 to 0.83 and from 0.70 to 0.93, respectively. Additional simulations were performed with the absence of the lysimeter, revealing faster transport of nitrates below drip line in the CONT plots, mostly because of the increased surface area subjected to precipitation
FireStem2D--a two-dimensional heat transfer model for simulating tree stem injury in fires.
Directory of Open Access Journals (Sweden)
Efthalia K Chatziefstratiou
Full Text Available 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 resolving stem moisture loss, temperatures through the stem, degree of bark charring, and necrotic depth around the stem. We present the results of numerical parameterization and model evaluation experiments for FireStem2D that simulate laboratory stem-heating experiments of 52 tree sections from 25 trees. We also conducted a set of virtual sensitivity analysis experiments to test the effects of unevenness of heating around the stem and with aboveground height using data from two studies: a low-intensity surface fire and a more intense crown fire. The model allows for improved understanding and prediction of the effects of wildland fire on injury and mortality of trees of different species and sizes.
Stable Non--Perturbative Minimal Models Coupled to 2D Quantum Gravity
Johnson, C; Spence, B; Johnson, Clifford; Morris, Tim; Spence, Bill
1992-01-01
A generalisation of the non--perturbatively stable solutions of string equations which respect the KdV flows, obtained recently for the $(2m-1,2)$ conformal minimal models coupled to two--dimensional quantum gravity, is presented for the $(p,q)$ models. These string equations are the most general string equations compatible with the $q$--th generalised KdV flows. They exhibit a close relationship with the bi-hamiltonian structure in these hierarchies. The Ising model is studied as a particular example, for which a real non-singular numerical solution to the string susceptibility is presented.
Parameter estimation and accuracy matching strategies for 2-D reactor models
Nowak, U.; Grah, A.; Schreier, M.
2005-11-01
The mathematical modelling of a special modular catalytic reactor kit leads to a system of partial differential equation in two space dimensions. As customary, this model contains uncertain physical parameters, which may be adapted to fit experimental data. To solve this nonlinear least-squares problem we apply a damped Gauss-Newton method. A method of lines approach is used to evaluate the associated model equations. By an a priori spatial discretization, a large DAE system is derived and integrated with an adaptive, linearly implicit extrapolation method. For sensitivity evaluation we apply an internal numerical differentiation technique, which reuses linear algebra information from the model integration. In order not to interfere with the control of the Gauss-Newton iteration these computations are done usually very accurately and, therefore, with substantial cost. To overcome this difficulty, we discuss several accuracy adaptation strategies, e.g., a master-slave mode. Finally, we present some numerical experiments.
Baryon Acoustic Oscillations in 2D: Modeling Redshift-space Power Spectrum from Perturbation Theory
Taruya, Atsushi; Saito, Shun
2010-01-01
We present an improved prescription for matter power spectrum in redshift space taking a proper account of both the non-linear gravitational clustering and redshift distortion, which are of particular importance for accurately modeling baryon acoustic oscillations (BAOs). Contrary to the models of redshift distortion phenomenologically introduced but frequently used in the literature, the new model includes the corrections arising from the non-linear coupling between the density and velocity fields associated with two competitive effects of redshift distortion, i.e., Kaiser and Finger-of-God effects. Based on the improved treatment of perturbation theory for gravitational clustering, we compare our model predictions with monopole and quadrupole power spectra of N-body simulations, and an excellent agreement is achieved over the scales of BAOs. Potential impacts on constraining dark energy and modified gravity from the redshift-space power spectrum are also investigated based on the Fisher-matrix formalism. We...
A microscopic nuclear collective rotation-vibration model: 2D submodel
Gulshani, Parviz
2016-01-01
The previous microscopic collective rotation-vibration model is improved to include interaction between collective oscillations in a pair of spatial directions, and to remove many of the previous-model approximations. As in the previous model, the nuclear Schrodinger equation (instead of the Hamiltonian) is canonically transformed to obtain a Schrodinger equation for collective rotation and vibration of a nucleus coupled to an intrinsic motion, with the related constraints imposed on the wavefunction (rather than on the particle co-ordinates). The resulting equation is then effectively linearized into three self-consistent, time-reversal invariant, cranking-type equations using a variational method. The relation of the equations to the phenomenological hydrodynamic collective Bohr-Davydov-Faessler-Greiner model is discussed. To facilitate the solution of the equations and enhance physical insight, we consider in this article the collective oscillations in only two space directions. For harmonic oscillator mea...
An efficient numerical model for hydrodynamic parameterization in 2D fractured dual-porosity media
Fahs, Hassane; Hayek, Mohamed; Fahs, Marwan; Younes, Anis
2014-01-01
This paper presents a robust and efficient numerical model for the parameterization of the hydrodynamic in fractured porous media. The developed model is based upon the refinement indicators algorithm for adaptive multi-scale parameterization. For each level of refinement, the Levenberg-Marquardt method is used to minimize the difference between the measured and predicted data that are obtained by solving the direct problem with the mixed finite element method. Sensitivities of state variables with respect to the parameters are calculated by the sensitivity method. The adjoint-state method is used to calculate the local gradients of the objective function necessary for the computation of the refinement indicators. Validity and efficiency of the proposed model are demonstrated by means of several numerical experiments. The developed numerical model provides encouraging results, even for noisy data and/or with a reduced number of measured heads.
Application of 2-D sediment model to fluctuating backwater area of Yangtze River
Institute of Scientific and Technical Information of China (English)
Yong FAN
2009-01-01
Based on the characteristics of backflow,a two-dimensional mathematical model of sediment movement was established.The complexity of the watercourse boundary at the confluence of the main stream and the tributary was dealt with using a boundary-fitting orthogonal coordinate system.The basic equation of the two-dimensional total sediment load model,the numerical calculation format,and key problems associated with using the orthogonal curvilinear coordinate system were discussed.Water and sediment flow in the Chongqing reach of the Yangtze River were simulated.The calculated water level,flow velocity distribution,amount of silting and scouring,and alluvial distribution are found to be in agreement with the measured data,which indicates that the numerical model and calculation method are reasonable.The model can be used for calculation of flow in a relatively complicated river network.
Application of 2-D sediment model to fluctuating backwater area of Yangtze River
Directory of Open Access Journals (Sweden)
Yong FAN
2009-09-01
Full Text Available Based on the characteristics of backflow, a two-dimensional mathematical model of sediment movement was established. The complexity of the watercourse boundary at the confluence of the main stream and the tributary was dealt with using a boundary-fitting orthogonal coordinate system. The basic equation of the two-dimensional total sediment load model, the numerical calculation format, and key problems associated with using the orthogonal curvilinear coordinate system were discussed. Water and sediment flow in the Chongqing reach of the Yangtze River were simulated. The calculated water level, flow velocity distribution, amount of silting and scouring, and alluvial distribution are found to be in agreement with the measured data, which indicates that the numerical model and calculation method are reasonable. The model can be used for calculation of flow in a relatively complicated river network.
On Correlation Numbers in 2D Minimal Gravity and Matrix Models
Belavin, A A
2008-01-01
We test recent results for the four-point correlation numbers in Minimal Liouville Gravity against calculations in the one-Matrix Models, and find full agreement. In the process, we construct the resonance transformation which relates coupling parameters of the Liouville Gravity with the couplings of the Matrix Models, up to the terms of the order 4. We also conjecture the general form of this transformation.
Applying Contact Angle to a 2D Multiphase Smoothed Particle Hydrodynamics Model
Farrokhpanah, Amirsaman; Samareh, Babak; Mostaghimi, Javad
2016-01-01
Equilibrium contact angle of liquid drops over horizontal surfaces has been modeled using Smoothed Particle Hydrodynamics (SPH). The model is capable of accurate implementation of contact angles to stationary and moving contact lines. In this scheme, the desired value for stationary or dynamic contact angle is used to correct the profile near the triple point. This is achieved by correcting the surface normals near the contact line and also interpolating the drop profile into the boundaries. ...
2D Articulatory Velum Modeling Applied to Copy Synthesis of Sentences Containing Nasal Phonemes
Laprie, Yves; Elie, Benjamin; Tsukanova, Anastasiia
2015-01-01
International audience; Articulatory synthesis could become a valuable tool to investigate links between articulatory gestures and acoustic cues. This papers presents the construction of an articulatory model of the velum which is intended to complete a model already comprising other articulators. The velum contour was de-lineated and extracted from a thousand of X-ray images corresponding to short sentences of French. A principal component analysis was applied in order to derive the main def...
Enhanced Kalman Filtering for a 2D CFD NS Wind Farm Flow Model
Doekemeijer, B. M.; van Wingerden, J. W.; Boersma, S.; Pao, L. Y.
2016-09-01
Wind turbines are often grouped together for financial reasons, but due to wake development this usually results in decreased turbine lifetimes and power capture, and thereby an increased levelized cost of energy (LCOE). Wind farm control aims to minimize this cost by operating turbines at their optimal control settings. Most state-of-the-art control algorithms are open-loop and rely on low fidelity, static flow models. Closed-loop control relying on a dynamic model and state observer has real potential to further decrease wind's LCOE, but is often too computationally expensive for practical use. In this paper two time-efficient Kalman filter (KF) variants are outlined incorporating the medium fidelity, dynamic flow model “WindFarmSimulator” (WFSim). This model relies on a discretized set of Navier-Stokes equations in two dimensions to predict the flow in wind farms at low computational cost. The filters implemented are an Ensemble KF and an Approximate KF. Simulations in which a high fidelity simulation model represents the true wind farm show that these filters are 101 —102 times faster than a regular KF with comparable or better performance, correcting for wake dynamics that are not modeled in WFSim (noticeably, wake meandering and turbine hub effects). This is a first big step towards real-time closed-loop control for wind farms.
Multi-level model for 2D human motion analysis and description
Foures, Thomas; Joly, Philippe
2003-01-01
This paper deals with the proposition of a model for human motion analysis in a video. Its main caracteristic is to adapt itself automatically to the current resolution, the actual quality of the picture, or the level of precision required by a given application, due to its possible decomposition into several hierarchical levels. The model is region-based to address some analysis processing needs. The top level of the model is only defined with 5 ribbons, which can be cut into sub-ribbons regarding to a given (or an expected) level of details. Matching process between model and current picture consists in the comparison of extracted subject shape with a graphical rendering of the model built on the base of some computed parameters. The comparison is processed by using a chamfer matching algorithm. In our developments, we intend to realize a platform of interaction between a dancer and tools synthetizing abstract motion pictures and music in the conditions of a real-time dialogue between a human and a computer. In consequence, we use this model in a perspective of motion description instead of motion recognition: no a priori gestures are supposed to be recognized as far as no a priori application is specially targeted. The resulting description will be made following a Description Scheme compliant with the movement notation called "Labanotation".
Collective instabilities and collisional effects for a 2D model of a beam in a storage ring
Benedetti, C
2007-01-01
We consider a collisional 2D model for a beam in a ring. In the smooth focusing approximation the relaxation time scales according to Landau’s theory, but the p.d.f of momentum jumps has a power law decaying queue. A new hybrid regime is found for the equipartitioning due to the interplay between collisional and collective effects. The moments equations of a small perturbation to the KV distribution are analytically determined and the stability conditions follow from Floquet’s theory.
New urban area flood model: a comparison with MIKE11-quasi2d
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A. Sole
2005-01-01
Full Text Available Recent hydrogeological events have increased both public interest and that of the Scientific Community in a more accurate study of flooding in urban areas. The present project proposes a new model which offers an optimal integration of two models, one for flood wave propagation in riverbeds and the other for flooding in urban areas. We consider it necessary to not only treat the modelling of the outflow in riverbeds and outside riverbeds.together but to integrate them thoroughly. We simulate the propagation in riverbed of the flood event with a model solving the equations of De Saint Venant with the explicit scheme at the finite differences by McCormack. The propagation outside the riverbed is simulated using an algorithm proposed by Braschi et al. (1990. This algorithm is based on a local discretization of the urban territory, divided in a series of "tanks" and "channels". Each tank is associated with an area of an extension related to the position of the other tanks and the quantity of buildings, modelled as insurmountable obstacles. The model facilitates the simultaneous performance of the two simulations: at each instant, the quantitiy of water overflow, depending on the piezometric level in every section, is calculated as a function of the dimensions of the weirs (the banks, assuming it passes through the critical state. Then, it is transferred to the tanks placed in the surroundings of the overflow points. Those points are the starting nodes for the propagation of the flood because they are connected to the network of tanks in which the surrounding land has been schematised. In this paper, we present a comparison of one of the most powerful models of inundation simulation in urban and no-urban areas. The field area is the city of Albenga (SV, Italy and the simulated event is the inundation of the 1994 (return period of about 25 years.
The giant HII region NGC 588 as a benchmark for 2D photoionisation models
Perez-Montero, Enrique; Relano, Monica; Vilchez, Jose M; Kehrig, Carolina; Morisset, Christophe
2014-01-01
We use optical integral field spectroscopy and 8 and 24 micron mid-IR observations of the giant HII region NGC 588 in the disc of M33 as input and constraints for two-dimensional tailor-made photoionisation models. Two different geometrical approaches are followed for the modelling structure: i) Each spatial element of the emitting gas is studied individually using models which assume that the ionisation structure is complete in each element to look for azimuthal variations across gas and dust. ii) A single model is considered, and the two-dimensional structure of the gas and the dust are assumed to be due to the projection of an emitting sphere onto the sky. The models in both assumptions reproduce the radial profiles of Hbeta surface brightness, the observed number of ionising photons, and the strong optical emission-line relative intensities. The first approach produces a constant-density matter-bounded thin shell of variable thickness and dust-to-gas ratio, while the second gives place to a radiation-boun...
Directory of Open Access Journals (Sweden)
Peter Flaschel
2014-01-01
Full Text Available The paper argues that applicable macro is high frequency macro and the data generating process is therefore to be modeled in continuous time. It exemplifies this with a misuse of a 2D period model of monetarist type which becomes extremely overshooting, allowing for routes to “chaos,” when iterated at low frequencies. Instead of such low frequency procedures, we augment the model by a Keynesian feedback chain (the real rate of interest channel to introduce local instability into the model. We also introduce heterogeneous opinion dynamics into it. The implied 4D dynamics are made bounded thereby, but seem to allow only complex limit cycles, with no transition towards strange attractors anymore.
Calibrating OPC model with full CD profile data for 2D and 3D patterns using scatterometry
Dave, Aasutosh D.; Kritsun, Oleg; Deng, Yunfei; Yoshimoto, Kenji; Li, Jie; Hu, Jiangtao
2009-03-01
The ability to manage critical dimensions (CDs) of structures on IC devices is vital to improving product yield and performance. It is challenging to achieve accurate metrology data as the geometries shrink beyond 40 nm features. At this technology node CDSEM noise and resist LER are of significant concerns1. This paper examines the extendibility of scatterometry techniques to characterize structures that are close to limits of lithographic printing and to extract full profile information for 2D and 3D features for OPC model calibration2. The resist LER concerns are diminished because of the automatic averaging that scatterometry provides over the measurement pad; this represents a significant added value for proper OPC model calibration and verification. This work develops a comparison matrix to determine the impact of scatterometry data on OPC model calibration with conventional CDSEM measurements. The paper will report test results for the OPC model through process data for accuracy and predictability.
2D fuzzy Anti-de Sitter space from matrix models
Jurman, Danijel
2013-01-01
We study the fuzzy hyperboloids AdS^2 and dS^2 as brane solutions in matrix models. The unitary representations of SO(2,1) required for quantum field theory are identified, and explicit formulae for their realization in terms of fuzzy wavefunctions are given. In a second part, we study the (A)dS^2 brane geometry and its dynamics, as governed by a suitable matrix model. In particular, we show that trace of the energy-momentum tensor of matter induces transversal perturbations of the brane and of the Ricci scalar. This leads to a linearized form of Henneaux-Teitelboim-type gravity, illustrating the mechanism of emergent gravity in matrix models.
Time domain numerical modeling of wave propagation in 2D heterogeneous porous media
Chiavassa, Guillaume
2010-01-01
This paper deals with the numerical modeling of wave propagation in porous media described by Biot's theory. The viscous efforts between the fluid and the elastic skeleton are assumed to be a linear function of the relative velocity, which is valid in the low-frequency range. The coexistence of propagating fast compressional wave and shear wave, and of a diffusive slow compressional wave, makes numerical modeling tricky. To avoid restrictions on the time step, the Biot's system is splitted into two parts: the propagative part is discretized by a fourth-order ADER scheme, while the diffusive part is solved analytically. Near the material interfaces, a space-time mesh refinement is implemented to capture the small spatial scales related to the slow compressional wave. The jump conditions along the interfaces are discretized by an immersed interface method. Numerical experiments and comparisons with exact solutions confirm the accuracy of the numerical modeling. The efficiency of the approach is illustrated by s...
AN EXPERT APPROACH ON AUTOMATIC SOLID MODEL RECONSTRUCTION FROM 2D PROJECTIONS
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İsmail ŞAHİN
2008-02-01
Full Text Available This paper examines how to automatically reconstruct three dimentions (3D models from their orthographic two and three views and explains a new approach developed for that purpose. The approach is based on the identification of geometric features with the interpretation of 2B views, their volumetric intersections and reconstruction of solid models. A number of rules have been defined for this goal and they implemented on a prototype software with the approach of expert systems. The developed software allows determination of some features efficiently such as slot, holes, blind holes, closed prismatic holes, etc. Another contrubition of this research is to reconstruct solid models from their full section and half section views that is almost noneexistend in the releated literature.
Tian, Junfang; Li, Geng; Treiber, Martin; Zhu, Chenqiang; Jia, Bin
2016-01-01
This paper firstly show that 2 Dimensional Intelligent Driver Model (Jiang et al., PloS one, 9(4), e94351, 2014) is not able to replicate the synchronized traffic flow. Then we propose an improved model by considering the difference between the driving behaviors at high speeds and that at low speeds. Simulations show that the improved model can reproduce the phase transition from synchronized flow to wide moving jams, the spatiotemporal patterns of traffic flow induced by traffic bottleneck, and the evolution concavity of traffic oscillations (i.e. the standard deviation of the velocities of vehicles increases in a concave/linear way along the platoon). Validating results show that the empirical time series of traffic speed obtained from Floating Car Data can be well simulated as well.
Comparing 1D, 2D and 3D models for predicting root water uptake at the plant scale
de Willigen, Peter; van Dam, Jos; Heinen, Marius; Javaux, Mathieu
2010-05-01
Numerous modeling approaches exist to simulate soil water extraction by plant roots. They mainly differ in terms of dimensionality (from 1-D to 3-D) and in the degree of detail involved in the root geometry. One dimensional models consider 1-D root length density profiles and assume uniform horizontal soil water distribution and are very efficient regarding computation time. On the opposite, very detailed 3-D approaches, which consider explicitly the root architecture and the root water flow, may need more computation power and time. In between these two extreme cases, other approaches exist, which may be more accurate and less computationally demanding. Our objective is to compare different modeling approaches and check how their implicit or explicit simplifications or assumptions affect the root water uptake (RWU) predictions. Four models were subject to our comparison, all based on Richards equation. The first is a 1-D model solving Richards equation (SWAP) with the Feddes (1978) approach for RWU. The second one is also based on SWAP but with the root water uptake defined by a microscopic approach developed by de Jong van Lier (2008). The third one, FUSSIM, solves the Richards equation in 2-D based on a 2-D distribution of root length density (RLD). The fourth one is R-SWMS, a 3-D model simulating the water flow in the soil and in the roots, based on the complete root architecture description. A 45-day maize root was generated in 3-D and simplified in 2-D or 1-D RLD distributions. We simulated a constant uptake rate for 30 days with a 1-day rainfall at day 15 in three different soil types. We compared relative water uptake versus relative root length density profiles, and actual transpiration time series. On the one hand, the general trends of cumulative transpiration with time for the three soils were relatively similar for all models. On the other hand, some features like hydraulic lift are simulated by both FUSSIM and RSWMS models while other models do not
A new model of quantum chaotic billiards Spectral Statistics and Wavefunctions in 2D
Cuevas, E; Vergés, J A
1996-01-01
Quantum chaotic dynamics is obtained for a tight-binding model in which the energies of the atomic levels at the boundary sites are chosen at random. Results for the square lattice indicate that the energy spectrum shows a complex behavior with regions that obey the Wigner-Dyson statistics and localized and quasi-ideal states distributed according to Poisson statistics. Although the averaged spatial extension of the eigenstates in the present model scales with the size of the system as in the Gaussian Orthogonal Ensemble, the fluctuations are much larger.
Large scale 2D numerical modelling of reservoirs sedimentation and flushing operations
Dewals, Benjamin; Erpicum, Sébastien; Archambeau, Pierre; Detrembleur, Sylvain; Fraikin, Catherine; Pirotton, Michel
2004-01-01
The quasi-3D flow solver WOLF has been developed at the University of Liege for almost a decade. It has been used to carry out the simulation of silting processes in large reservoirs and to predict the efficiency of flushing operations. Besides briefly depicting the mathematical and numerical model, the present paper demonstrates its applicability on the case of a large hydropower project in India. The silting process of the reservoir has been simulated by means of the quasi-3D flow model wit...
Exact solution of the 2d dimer model: Corner free energy, correlation functions and combinatorics
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Allegra, Nicolas, E-mail: nicolas.allegra@univ-lorraine.fr
2015-05-15
In this work, some classical results of the pfaffian theory of the dimer model based on the work of Kasteleyn, Fisher and Temperley are introduced in a fermionic framework. Then we shall detail the bosonic formulation of the model via the so-called height mapping and the nature of boundary conditions is unravelled. The complete and detailed fermionic solution of the dimer model on the square lattice with an arbitrary number of monomers is presented, and finite size effect analysis is performed to study surface and corner effects, leading to the extrapolation of the central charge of the model. The solution allows for exact calculations of monomer and dimer correlation functions in the discrete level and the scaling behavior can be inferred in order to find the set of scaling dimensions and compare to the bosonic theory which predicts particular features concerning corner behaviors. Finally, some combinatorial and numerical properties of partition functions with boundary monomers are discussed, proved and checked with enumeration algorithms.
Adaptive Fault-Tolerant Routing in 2D Mesh with Cracky Rectangular Model
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Yi Yang
2014-01-01
Full Text Available This paper mainly focuses on routing in two-dimensional mesh networks. We propose a novel faulty block model, which is cracky rectangular block, for fault-tolerant adaptive routing. All the faulty nodes and faulty links are surrounded in this type of block, which is a convex structure, in order to avoid routing livelock. Additionally, the model constructs the interior spanning forest for each block in order to keep in touch with the nodes inside of each block. The procedure for block construction is dynamically and totally distributed. The construction algorithm is simple and ease of implementation. And this is a fully adaptive block which will dynamically adjust its scale in accordance with the situation of networks, either the fault emergence or the fault recovery, without shutdown of the system. Based on this model, we also develop a distributed fault-tolerant routing algorithm. Then we give the formal proof for this algorithm to guarantee that messages will always reach their destinations if and only if the destination nodes keep connecting with these mesh networks. So the new model and routing algorithm maximize the availability of the nodes in networks. This is a noticeable overall improvement of fault tolerability of the system.
Hard Copy to Digital Transfer: 3D Models that Match 2D Maps
Kellie, Andrew C.
2011-01-01
This research describes technical drawing techniques applied in a project involving digitizing of existing hard copy subsurface mapping for the preparation of three dimensional graphic and mathematical models. The intent of this research was to identify work flows that would support the project, ensure the accuracy of the digital data obtained,…
Accurate 2D/3D electromagnetic modeling for time-domain airborne EM systems
Yin, C.; Hodges, G.
2012-12-01
The existing industry software cannot deliver correct results for 3D time-domain airborne EM responses. In this paper, starting from the Fourier transform and convolution, we compare the stability of different modeling techniques and analyze the reason for instable calculations of the time-domain airborne EM responses. We find that the singularity of the impulse responses of EM systems at very early time that are used in the convolution is responsible for the instability of the modeling (Fig.1). Based on this finding, we put forward an algorithm that uses step response rather than impulse response of the airborne EM system for the convolution and create a stable algorithm that delivers precise results and maintains well the integral/derivative relationship between the magnetic field B and the magnetic induction dB/dt. A three-step transformation procedure for the modeling is proposed: 1) output the frequency-domain EM response data from the existing software; 2) transform into step-response by digital Fourier/Hankel transform; 3) convolve the step response with the transmitting current or its derivatives. The method has proved to be working very well (Fig. 2). The algorithm can be extended to the modeling of other time-domain ground and airborne EM system responses.Fig. 1: Comparison of impulse and step responses for an airborne EM system Fig. 2: Bz and dBz/dt calculated from step (middle panel) and impulse responses (lower panel) for the same 3D model as in Fig.1.
Autovino, Dario; Negm, Amro; Rallo, Giovanni; Provenzano, Giuseppe
2016-04-01
In Mediterranean countries characterized by limited water resources for agricultural and societal sectors, irrigation management plays a major role to improve water use efficiency at farm scale, mainly where irrigation systems are correctly designed to guarantee a suitable application efficiency and the uniform water distribution throughout the field. In the last two decades, physically-based agro-hydrological models have been developed to simulate mass and energy exchange processes in the soil-plant-atmosphere (SPA) system. Mechanistic models like HYDRUS 2D/3D (Šimunek et al., 2011) have been proposed to simulate all the components of water balance, including actual crop transpiration fluxes estimated according to a soil potential-dependent sink term. Even though the suitability of these models to simulate the temporal dynamics of soil and crop water status has been reported in the literature for different horticultural crops, a few researches have been considering arboreal crops where the higher gradients of root water uptake are the combination between the localized irrigation supply and the three dimensional root system distribution. The main objective of the paper was to assess the performance of HYDRUS-2D model to evaluate soil water contents and transpiration fluxes of an olive orchard irrigated with two different water distribution systems. Experiments were carried out in Castelvetrano (Sicily) during irrigation seasons 2011 and 2012, in a commercial farm specialized in the production of table olives (Olea europaea L., var. Nocellara del Belice), representing the typical variety of the surrounding area. During the first season, irrigation water was provided by a single lateral placed along the plant row with four emitters per plant (ordinary irrigation), whereas during the second season a grid of emitters laid on the soil was installed in order to irrigate the whole soil surface around the selected trees. The model performance was assessed based on the
2D transport modeling of tritium-helium in an aquifer with Alliances
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Dimier, A.; Appelo, C.A.J. [Andra, France, Hydrochemical Consultant (Netherlands)
2005-07-01
Full text of publication follows: ANDRA is the French organization in charge of the safety assessment of nuclear waste disposals. In a joint cooperation with other French organizations (CEA), tools are developed for predicting the migration of radionuclides and chemical species through geological media, all combined in the 'Alliances' platform. For the coupling of geochemistry and transport different codes have now been implemented: PHREEQC or CHESS for the chemical part, CASTEM, MT3D or TRACES for 3D transport and diffusion. Validation of the coupled codes was done on various hypothetical problems with complicated chemistry involving speciation, dissolution-precipitation, sorption and surface complexation. At present, the tool has matured sufficiently to simulate 'real world' configurations, and we present the modeling of tritium/helium profiles in an aquifer near Bocholt, Germany. A major challenge of reactive transport modeling in aquifers is the delineation of the flow field. Many profiles with environmental tracers such as tritium, tritium/helium and CFC's or SF6 have been reported and were compared with flow model results, but it appears difficult to generate a satisfactory model from many possible alternatives. Schlosser et al. (1988, 1989) analyzed {sup 3}H/{sup 3}He profiles in an aquifer using multilevel sampling wells. The profiles show a relatively low concentration of total {sup 3}H+{sup 3}He which led Schlosser to assume a small effective infiltration rate of 0.1 m/yr. However, the precipitation surplus in the area is at least 0.3 m/yr. Alternatively, total {sup 3}H+{sup 3}He decreases if 3He escapes into soil air by large dispersion in the aquifer, as shown by Schlosser et al. in 1D profiles. However, the large dispersion originates from heterogeneities in the flow field and is, in principle, connected with aquifer properties, thus presenting an ideal test case for Alliances. For initiating the hydraulic model, the {sup 3}H
Delocalization of two interacting particles in the 2D Harper model
Frahm, Klaus M.; Shepelyansky, Dima L.
2016-01-01
We study the problem of two interacting particles in a two-dimensional quasiperiodic potential of the Harper model. We consider an amplitude of the quasiperiodic potential such that in absence of interactions all eigenstates are exponentially localized while the two interacting particles are delocalized showing anomalous subdiffusive spreading over the lattice with the spreading exponent b ≈ 0.5 instead of a usual diffusion with b = 1. This spreading is stronger than in the case of a correlated disorder potential with a one particle localization length as for the quasiperiodic potential. At the same time we do not find signatures of ballistic pairs existing for two interacting particles in the localized phase of the one-dimensional Harper model.
Critical Casimir forces between defects in the 2D Ising model
Nowakowski, P.; Maciołek, A.; Dietrich, S.
2016-12-01
An exact statistical mechanical derivation is given of the critical Casimir interactions between two defects in a planar lattice-gas Ising model. Each defect is a finite group of nearest-neighbor spins with modified coupling constants. Such a system can be regarded as a model of a binary liquid mixture with the molecules confined to a membrane and the defects mimicking protein inclusions embedded into the membrane. As suggested by recent experiments, certain cellular membranes appear to be tuned to the proximity of a critical demixing point belonging to the two-dimensional Ising universality class. Therefore one can expect the emergence of critical Casimir forces between membrane inclusions. These forces are governed by universal scaling functions, which we derive for simple defects. We prove that the scaling law appearing at criticality is the same for all types of defects considered here.
Hue, V; Cavalié, T; Dobrijevic, M; Hersant, F
2015-01-01
Saturn's axial tilt produces seasons in a similar way as on Earth. Both the stratospheric temperature and composition are affected by this latitudinally varying insolation along the seasons. The thermal structure is controlled and regulated by the amount of hydrocarbons in the stratosphere, which act as absorbers and coolants from the UV to the far-IR spectral range, and this structure influences the amount of hydrocarbons. We study here the feedback between the chemical composition and the thermal structure by coupling a latitudinal and seasonal photochemical model with a radiative seasonal model. Our results show that the seasonal temperature peak in the higher stratosphere, associated with the seasonal increase of insolation, is shifted earlier than the maximum insolation peak. This shift is increased with increasing latitudes and is caused by the low amount of stratospheric coolants in the spring season. At 80$^{\\circ}$ in both hemispheres, the temperature peak at 1d-2mbar is seen to occur half a season e...
A 2D Time Domain DRBEM Computer Model for MagnetoThermoelastic Coupled Wave Propagation Problems
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Mohamed Abdelsabour Fahmy
2014-07-01
Full Text Available A numerical computer model based on the dual reciprocity boundary element method (DRBEM is extended to study magneto-thermoelastic coupled wave propagation problems with relaxation times involving anisotropic functionally graded solids. The model formulation is tested through its application to the problem of a solid placed in a constant primary magnetic field acting in the direction of the z-axis and rotating about this axis with a constant angular velocity. In the case of two-dimensional deformation, an implicit-explicit time domain DRBEM was presented and implemented to obtain the solution for the displacement and temperature fields. A comparison of the results is presented graphically in the context of Lord and Shulman (LS and Green and Lindsay (GL theories. Numerical results that demonstrate the validity of the proposed method are also presented graphically.
New 2D Thermal Model Applied to an LHC Inner Triplet Quadrupole Magnet
Bielert, ER; Ten Kate, HHJ; Verweij, AP
2011-01-01
A newly developed numerical model is presented that enables to compute two-dimensional heat transfer and temperature distributions over the cross-section of superconducting accelerator magnets. The entire thermal path from strand-in-cable to heat sink, including helium channels is considered. Superfluid helium properties are combined with temperature- and field-dependent non-linear solid material properties. Interfacial interactions are also taken into account. The model is applied to the cross-section of an inner triplet quadrupole magnet featuring a new concept for the ground insulation. Beam loss profiles are implemented as main heat source. It is concluded that operational margins can be considerably increased by opening additional thermal paths, improving the cooling conditions.
Applying Contact Angle to a 2D Multiphase Smoothed Particle Hydrodynamics Model
Farrokhpanah, Amirsaman; Mostaghimi, Javad
2016-01-01
Equilibrium contact angle of liquid drops over horizontal surfaces has been modeled using Smoothed Particle Hydrodynamics (SPH). The model is capable of accurate implementation of contact angles to stationary and moving contact lines. In this scheme, the desired value for stationary or dynamic contact angle is used to correct the profile near the triple point. This is achieved by correcting the surface normals near the contact line and also interpolating the drop profile into the boundaries. Simulations show that a close match to the chosen contact angle values can be achieved for both stationary and moving contact lines. This technique has proven to reduce the amount of nonphysical shear stresses near the triple point and to enhance the convergence characteristics of the solver.
Hassan, Ehab; Morrison, P J; Horton, W
2016-01-01
Progress in understanding the coupling between plasma instabilities in the equatorial electrojet based on a unified fluid model is reported. A deeper understanding of the linear and nonlinear evolution and the coupling of the gradient-drift and Farley-Buneman instabilities is achieved by studying the e?ect of di?erent combinations of the density-gradient scale-lengths (Ln) and cross-?eld (E?B) drifts on the plasma turbulence. Mechanisms and channels of energy transfer are illucidated for these multiscale instabilities. Energy for the uni?ed model is examined, including the injected, conservative redistribution (between ?elds and scales), and ultimate dissipation. Various physical mechanisms involved in the energetics are categorized as sources, sinks, nonlinear transfer, and coupling to show that the system satisfies the fundamental law of energy Oonservation. The physics of the nonlinear transfer terms is studied to identify their roles in producing energy cascades { the transference of energy from the domin...
A hierarchical lattice spring model to simulate the mechanics of 2-D materials-based composites
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Lucas eBrely
2015-07-01
Full Text Available In the field of engineering materials, strength and toughness are typically two mutually exclusive properties. Structural biological materials such as bone, tendon or dentin have resolved this conflict and show unprecedented damage tolerance, toughness and strength levels. The common feature of these materials is their hierarchical heterogeneous structure, which contributes to increased energy dissipation before failure occurring at different scale levels. These structural properties are the key to exceptional bioinspired material mechanical properties, in particular for nanocomposites. Here, we develop a numerical model in order to simulate the mechanisms involved in damage progression and energy dissipation at different size scales in nano- and macro-composites, which depend both on the heterogeneity of the material and on the type of hierarchical structure. Both these aspects have been incorporated into a 2-dimensional model based on a Lattice Spring Model, accounting for geometrical nonlinearities and including statistically-based fracture phenomena. The model has been validated by comparing numerical results to continuum and fracture mechanics results as well as finite elements simulations, and then employed to study how structural aspects impact on hierarchical composite material properties. Results obtained with the numerical code highlight the dependence of stress distributions on matrix properties and reinforcement dispersion, geometry and properties, and how failure of sacrificial elements is directly involved in the damage tolerance of the material. Thanks to the rapidly developing field of nanocomposite manufacture, it is already possible to artificially create materials with multi-scale hierarchical reinforcements. The developed code could be a valuable support in the design and optimization of these advanced materials, drawing inspiration and going beyond biological materials with exceptional mechanical properties.
Carbonate fracture stratigraphy: An integrated outcrop and 2D discrete element modelling study
Spence, Guy; Finch, Emma
2013-04-01
Constraining fracture stratigraphy is important as natural fractures control primary fluid flow in low matrix permeability naturally fractured carbonate hydrocarbon reservoirs. Away from the influence of folds and faults, stratigraphic controls are known to be the major control on fracture networks. The fracture stratigraphy of carbonate nodular-chert rhythmite successions are investigated using a Discrete Element Modelling (DEM) technique and validated against observations from outcrops. Comparisons are made to the naturally fractured carbonates of the Eocene Thebes Formation exposed in the west central Sinai of Egypt, which form reservoir rocks in the nearby East Ras Budran Field. DEM allows mechanical stratigraphy to be defined as the starting conditions from which forward numerical modelling can generate fracture stratigraphy. DEM can incorporate both stratigraphic and lateral heterogeneity, and enable mechanical and fracture stratigraphy to be characterised separately. Stratally bound stratified chert nodules below bedding surfaces generate closely spaced lateral heterogeneity in physical properties at stratigraphic mechanical interfaces. This generates extra complexity in natural fracture networks in addition to that caused by bed thickness and lithological physical properties. A series of representative geologically appropriate synthetic mechanical stratigraphic models were tested. Fracture networks generated in 15 DEM experiments designed to isolate and constrain the effects of nodular chert rhythmites on carbonate fracture stratigraphy are presented. The discrete element media used to model the elastic strengths of rocks contain 72,866 individual elements. Mechanical stratigraphies and the fracture networks generated are placed in a sequence stratigraphic framework. Nodular chert rhythmite successions are shown to be a distinct type of naturally fractured carbonate reservoir. Qualitative stratigraphic rules for predicting the distribution, lengths, spacing
Multi-Scale Modeling, Design Strategies and Physical Properties of 2D Composite Sheets
2015-01-15
Phase-Field Modeling and Experiments, Nano Letters, (11 2013): 0. doi: 10.1021/nl4033928 Damien Voiry, Maryam Salehi, Rafael Silva , Takeshi Fujita...Manish Chhowalla, Hisato Yamaguchi, Junwen Li, Damien Voiry, Rafael Silva , Diego C. B. Alves, Takeshi Fujita, Mingwei Chen, Tewodros Asefa, Vivek B...Simon J. Kelly, Anna Morozovska, Ehsan Kabiri Rahani, Evgheni Strelcov, Eugene Eliseev, Stephen Jesse, Michael D. Biegalski, Nina Balke. Mechanical
Spontaneous supersymmetry breaking in the 2d N=1 Wess-Zumino model
Baumgartner, David; Wenger, Urs
2013-01-01
We study the phase diagram of the two-dimensional N=1 Wess-Zumino model using Wilson fermions and the fermion loop formulation. We give a complete non-perturbative determination of the ground state structure in the continuum and infinite volume limit. We also present a determination of the particle spectrum in the supersymmetric phase, in the supersymmetry broken phase and across the supersymmetry breaking phase transition. In the supersymmetry broken phase we observe the emergence of the Goldstino particle.
Hue, V.; Greathouse, T. K.; Cavalié, T.; Dobrijevic, M.; Hersant, F.
2016-03-01
Saturn's axial tilt of 26.7° produces seasons in a similar way as on Earth. Both the stratospheric temperature and composition are affected by this latitudinally varying insolation along Saturn's orbital path. The atmospheric thermal structure is controlled and regulated by the amount of hydrocarbons in the stratosphere, which act as absorbers and coolants from the UV to the far-IR spectral range, and this structure has an influence on the amount of hydrocarbons. We study here the feedback between the chemical composition and the thermal structure by coupling a latitudinal and seasonal photochemical model with a radiative seasonal model. Our results show that the seasonal temperature peak in the higher stratosphere, associated with the seasonal increase of insolation, is shifted earlier than the maximum insolation peak. This shift is increased with increasing latitudes and is caused by the low amount of stratospheric coolants in the spring season. At 80° in both hemispheres, the temperature peak at 10-2 mbar is seen to occur half a season (3-4 Earth years) earlier than was previously predicted by radiative seasonal models that assumed spatially and temporally uniform distribution of coolants. This shift progressively decreases with increasing pressure, up to around the 0.5 mbar pressure level where it vanishes. On the opposite, the thermal field has a small feedback on the abundance distributions. Accounting for that feedback modifies the predicted equator-to-pole temperature gradient. The meridional gradients of temperature at the mbar pressure levels are better reproduced when this feedback is accounted for. At lower pressure levels, Saturn's stratospheric thermal structure seems to depart from pure radiative seasonal equilibrium as previously suggested by Guerlet et al. (2014). Although the agreement with the absolute value of the stratospheric temperature observed by Cassini is moderate, it is a mandatory step toward a fully coupled GCM-photochemical model.
Energy Technology Data Exchange (ETDEWEB)
Loarte, A. [JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (United Kingdom); Chankin, A. [JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (United Kingdom); Clement, S. [JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (United Kingdom); Corrigan, G. [JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (United Kingdom); Harbour, P. [JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (United Kingdom); Horton, L. [JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (United Kingdom); Janeschitz, G. [JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (United Kingdom); Lingertat, J. [JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (United Kingdom); Matthews, G. [JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (United Kingdom); Simonini, R. [JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (United Kingdom); Tagle, J.A. [JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (United Kingdom); Taroni, A. [JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (United Kingdom); Vlases, G. [JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (United Kingdom)
1995-04-01
Modelling with the EDGE2D/U-NIMBUS code of the measured scrape-off layer plasma parameters for JET divertor discharges is presented. Model results agree with the experiment if very small values (< or {approx}0.1 m{sup 2}/s in H-modes and low power L-modes) for the anomalous particle transport diffusion coefficient in the SOL are used. While the assumption of the power flow out of the main plasma being carried equally by the electrons and the ions describes satisfactorily the global power balance for Ohmic and L-mode discharges, more power flowing out through the ion channel is consistent with the power balance in hot ion H-modes. Some sensitivity studies of the code results on the modelling hypothesis are discussed. ((orig.)).
Pseudo-2D model of a cross-flow membrane humidifier for a PEM fuel cell under multiphase conditions
Energy Technology Data Exchange (ETDEWEB)
Dalet, C.; Diny, M. [Peugeot Citroen Automobile, Carrieres sous Poissy (France). Fuel Cell Program; Maranzana, G.; Lottin, O.; Dillet, J. [Nancy Univ., Vanoeuvre les Nancy (France). Centre national de la recherche scientifique
2009-07-01
Membrane dehydration can reduce the performance of proton exchange membrane fuel cells (PEMFCs). However, excessive water at the inlet of the fuel cells can flood cathodes. An understanding of the coupled mass and heat transfer processes involved in membrane humidifiers is needed in order to successfully manage water in PEMFCs. This paper discussed a pseudo-2D model of a cross-flow membrane humidifier for PEMFCs. The model was used to test correlations of the water transport coefficient through a Nafion 115 membrane. The study showed that results obtained using the model differed from experimental results. The effects of inlet operating conditions, flow rates, and temperature on the performance of a planar membrane humidifier under both single- and multi-phase conditions were also investigated.
1D and 2D Numerical Modeling for Solving Dam-Break Flow Problems Using Finite Volume Method
Directory of Open Access Journals (Sweden)
Szu-Hsien Peng
2012-01-01
Full Text Available The purpose of this study is to model the flow movement in an idealized dam-break configuration. One-dimensional and two-dimensional motion of a shallow flow over a rigid inclined bed is considered. The resulting shallow water equations are solved by finite volumes using the Roe and HLL schemes. At first, the one-dimensional model is considered in the development process. With conservative finite volume method, splitting is applied to manage the combination of hyperbolic term and source term of the shallow water equation and then to promote 1D to 2D. The simulations are validated by the comparison with flume experiments. Unsteady dam-break flow movement is found to be reasonably well captured by the model. The proposed concept could be further developed to the numerical calculation of non-Newtonian fluid or multilayers fluid flow.
Quark-Antiquark and Diquark Condensates in Vacuum in a 2D Two-Flavor Gross-Neveu Model
Institute of Scientific and Technical Information of China (English)
ZHOU Bang-Rong
2007-01-01
The analysis based on the renormalized effective potential indicates that, similar to in the 4D two-flavor Nambu-Jona-Lasinio (NJL) model, in a 2D two-flavor Gross-Neveu model, the interplay between the quark-antiquark and the diquark condensates in vacuum also depends on Gs/Hs, the ratio of the coupling constants in scalar quark antiquark and scalar diquark channel. Only the pure quark-antiquark condensates exist if Gs/Hs ＞ 2/3, which is just the ratio of the color numbers of the quarks participating in the diquark and quark-antiquark condensates. The two condensates will coexist if 0 ＜ Gs/Hs ＜ 2/3. However, different from the 4D NJL model, the pure diquark condensates arise only at Gs/Hs = 0 and are not in a possibly finite region of Gs/Hs below 2/3.
Yu, Ting; Chaix, Jean-François; Komatitsch, Dimitri; Garnier, Vincent; Audibert, Lorenzo; Henault, Jean-Marie
2017-02-01
Multiple scattering is important when ultrasounds propagate in a heterogeneous medium such as concrete, the scatterer size of which is in the order of the wavelength. The aim of this work is to build a 2D numerical model of ultrasonic wave propagation integrating the multiple scattering phenomena in SPECFEM software. The coherent field of multiple scattering could be obtained by averaging numerical wave fields, and it is used to determine the effective phase velocity and attenuation corresponding to an equivalent homogeneous medium. After the creation of numerical model under several assumptions, its validation is completed in a case of scattering by one cylinder through the comparison with analytical solution. Two cases of multiple scattering by a set of cylinders at different concentrations are simulated to perform a parametric study (of frequency, scatterer concentration, scatterer size). The effective properties are compared with the predictions of Waterman-Truell model as well, to verify its validity.
Finite-Element 2D and 3D PIC Modeling of RF Devices with Applications to Multipacting
De Ford, John F; Petillo, John
2005-01-01
Multipacting currently limits the performance of many high power radio-frequency (RF) devices, particularly couplers and windows. Models have helped researchers understand and mitigate this problem in 2D structures, but useful multipacting models for complicated 3D structures are still a challenge. A combination of three recent technologies that have been developed in the Analyst and MICHELLE codes begin to address this challenge: high-order adaptive finite-element RF field calculations, advanced particle tracking on unstructured grids, and comprehensive secondary emission models. Analyst employs high-order adaptive finite-element methods to accurately compute driven RF fields and eigenmodes in complex geometries, particularly near edges, corners, and curved surfaces. To perform a multipacting analysis, we use the mesh and fields from Analyst in a modified version of the self-consistent, finite-element gun code MICHELLE. MICHELLE has both a fast, accurate, and reliable particle tracker for unstructured grids ...
Mahmood, T.; Shahzad, A.; Iqbal, Z.; Ahmed, J.; Khan, M.
A study is presented for the flow and heat transfer of Sisko fluid model over an unsteady stretching sheet in the presence of uniform magnetic field. While taking newly developed similarity transformations, the governing time dependent partial differential equations are reduced to nonlinear ordinary differential equations. Numerical solutions of the reduced nonlinear differential equations are found by employing Shooting method. The influence of physical parameters of interest on the velocity and temperature profiles are highlighted graphically and examined in detail. Moreover, the skin friction coefficient and Nusselt number are tabulated against influential parameters. Skin friction coefficient increases with unsteadiness parameter, magnetic field and suction parameter.
Kasperski, Adam; Rżysko, Wojciech; Szabelski, Paweł
2016-12-01
The ability of capturing guest molecules in a selective way is one of desirable properties of modern structured adsorbents. This refers to a wide class of guest molecules, especially to those which are chiral and whose enantiomers are to be efficiently separated. In this contribution, using Monte Carlo modeling, we show how simple molecular building blocks with cruciform shape can be used to create 2D porous matrices with tunable adsorptive properties. To that end we consider different self-assembled structures comprising cross-shaped molecules and probe their ability to retain model guest molecules differing in size and shape. In particular we focus on the adsorption of enantiomeric pairs on these substrates and quantify the associated selectivity. The obtained results show that a suitable choice of the building block, including size and aspect ratio allows for the creation of 2D functional matrices with programmed adsorption performance. The findings of our theoretical investigations can be helpful in designing molecular guest-host systems with potential applications in separations, sensing and heterogeneous catalysis.
Enhanced Doppler reflectometry power response: physical optics and 2D full wave modelling
Pinzón, J. R.; Happel, T.; Blanco, E.; Conway, G. D.; Estrada, T.; Stroth, U.
2017-03-01
The power response of a Doppler reflectometer is investigated by means of the physical optics model; a simple model which considers basic scattering processes at the reflection layer. Apart from linear and saturated scattering regimes, non-linear regimes with an enhanced backscattered power are found. The different regimes are characterized and understood based on analytical calculations. The power response is also studied with two-dimensional full wave simulations, where the enhanced backscattered power regimes are also found in qualitative agreement with the physical optics results. The ordinary and extraordinary modes are compared for the same angle of incidence, with the conclusion that the ordinary mode is better suited for Doppler reflectometry turbulence level measurements due to the linearity of its response. The scattering efficiency is studied and a first approximation to describe it is proposed. At the end, the application of the physical optics results to experimental data analysis is discussed. In particular, a formula to assess the linearity of Doppler reflectometry measurements is provided.
Acid/base front propagation in saturated porous media: 2D laboratory experiments and modeling
Loyaux-Lawniczak, Stéphanie; Lehmann, François; Ackerer, Philippe
2012-09-01
We perform laboratory scale reactive transport experiments involving acid-basic reactions between nitric acid and sodium hydroxide. A two-dimensional experimental setup is designed to provide continuous on-line measurements of physico-chemical parameters such as pH, redox potential (Eh) and electrical conductivity (EC) inside the system under saturated flow through conditions. The electrodes provide reliable values of pH and EC, while sharp fronts associated with redox potential dynamics could not be captured. Care should be taken to properly incorporate within a numerical model the mixing processes occurring inside the electrodes. The available observations are modeled through a numerical code based on the advection-dispersion equation. In this framework, EC is considered as a variable behaving as a conservative tracer and pH and Eh require solving the advection dispersion equation only once. The agreement between the computed and measured pH and EC is good even without recurring to parameters calibration on the basis of the experiments. Our findings suggest that the classical advection-dispersion equation can be used to interpret these kinds of experiments if mixing inside the electrodes is adequately considered.
Competition among reputations in the 2D Sznajd model: Spontaneous emergence of democratic states
Crokidakis, Nuno
2011-01-01
We propose a modification in the Sznajd sociophysics model defined on the square lattice. For this purpose, we consider reputation-a mechanism limiting the agents' persuasive power. The reputation is introduced as a time-dependent score, which can be positive or negative. This mechanism avoids dictatorship (full consensus, all spins parallel) for a wide range of model parameters. We consider two different situations: case 1, in which the agents' reputation increases for each persuaded neighbor, and case 2, in which the agents' reputation increases for each persuasion and decreases when a neighbor keeps his opinion. Our results show that the introduction of reputation avoids full consensus even for initial densities of up spins greater than 1/2. The relaxation times follow a log-normal-like distribution in both cases, but they are larger in case 2 due to the competition among reputations. In addition, we show that the usual phase transition occurs and depends on the initial concentration $d$ of individuals wit...
Hayden-Lesmeister, A.; Remo, J. W.; Piazza, B.
2015-12-01
The Atchafalaya River (AR) in Louisiana is the principal distributary of the Mississippi River (MR), and its basin contains the largest contiguous area of baldcypress-water tupelo swamp forests in North America. After designation of the Atchafalaya River Basin (ARB) as a federal floodway following the destructive 1927 MR flood, it was extensively modified to accommodate a substantial portion of the MR flow (~25%) to mitigate flooding in southern Louisiana. These modifications and increased flows resulted in substantial incision along large portions of the AR, altering connectivity between the river and its associated waterbodies. As a result of incision, the hydroperiod has been substantially altered, which has contributed to a decline in ecological health of the ARB's baldcypress-water tupelo forests. While it is recognized that the altered hydroperiod has negatively affected natural baldcypress regeneration, it is unclear whether proposed projects designed to enhance flow connectivity will increase long-term survival of these forests. In this study, we have constructed a 1D2D hydrodynamic model using SOBEK 2.12 to realistically model key physical parameters such as residence times, inundation extent, water-surface elevations (WSELs), and flow velocities to increase our understanding of the ARB's altered hydroperiod and the consequences for baldcypress-water tupelo forests. While the model encompasses a majority of the ARB, our modeling effort is focused on the Flat Lake Water Management Unit located in the southern portion of the ARB, where it will also be used to evaluate flow connectivity enhancement projects within the management unit. We believe our 1D2D hybrid hydraulic modeling approach will provide the flexibility and accuracy needed to guide connectivity enhancement efforts in the ARB and may provide a model framework for guiding similar efforts along other highly-altered river systems.
Subsurface Gas Flow and Ice Grain Acceleration within Enceladus and Europa Fissures: 2D DSMC Models
Tucker, O. J.; Combi, M. R.; Tenishev, V.
2014-12-01
The ejection of material from geysers is a ubiquitous occurrence on outer solar system bodies. Water vapor plumes have been observed emanating from the southern hemispheres of Enceladus and Europa (Hansen et al. 2011, Roth et al. 2014), and N2plumes carrying ice and ark particles on Triton (Soderblom et al. 2009). The gas and ice grain distributions in the Enceladus plume depend on the subsurface gas properties and the geometry of the fissures e.g., (Schmidt et al. 2008, Ingersoll et al. 2010). Of course the fissures can have complex geometries due to tidal stresses, melting, freezing etc., but directly sampled and inferred gas and grain properties for the plume (source rate, bulk velocity, terminal grain velocity) can be used to provide a basis to constrain characteristic dimensions of vent width and depth. We used a 2-dimensional Direct Simulation Monte Carlo (DSMC) technique to model venting from both axi-symmetric canyons with widths ~2 km and narrow jets with widths ~15-40 m. For all of our vent geometries, considered the water vapor source rates (1027 - 1028 s-1) and bulk gas velocities (~330 - 670 m/s) obtained at the surface were consistent with inferred values obtained by fits of the data for the plume densities (1026 - 1028 s-1, 250 - 1000 m/s) respectively. However, when using the resulting DSMC gas distribution for the canyon geometries to integrate the trajectories of ice grains we found it insufficient to accelerate submicron ice grains to Enceladus' escape speed. On the other hand, the gas distributions in the jet like vents accelerated grains > 10 μm significantly above Enceladus' escape speed. It has been suggested that micron-sized grains are ejected from the vents with speeds comparable to the Enceladus escape speed. Here we report on these results including comparisons to results obtained from 1D models as well as discuss the implications of our plume model results. We also show preliminary results for similar considerations applied to Europa
A mathematical model for a didactic device able to simulate a 2D Newtonian gravitational field
De Marchi, Fabrizio
2015-01-01
In this paper we propose a mathematical model to describe a theoretical device able to simulate an inverse-square force on a test mass moving on a horizontal plane. We use two pulleys, a counterweight, a wire and a smooth rail, in addition to the test mass. The tension of the wire (i.e. the attractive force on the test mass) is determined by the position of a counterweight free to move on a rail placed under the plane. The profile of the rail is calculated in order to obtain the required Newtonian force. Details of this calculation are reported in the paper, and numerical simulations are provided in order to investigate the stability of the orbits under the effect of the main friction forces and other perturbative effects. This work points out that there are some criticalities intrinsic to the apparatus and gives some suggestions about how to minimize their impact.
Form factor expansions in the 2D Ising model and Painleve VI
Energy Technology Data Exchange (ETDEWEB)
Mangazeev, Vladimir V., E-mail: Vladimir.Mangazeev@anu.edu.a [Department of Theoretical Physics, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200 (Australia); Guttmann, Anthony J., E-mail: tonyg@ms.unimelb.edu.a [ARC Centre of Excellence for Mathematics and Statistics of Complex Systems, Department of Mathematics and Statistics, The University of Melbourne, Victoria 3010 (Australia)
2010-10-21
We derive a Toda-type recurrence relation, in both high- and low-temperature regimes, for the {lambda}-extended diagonal correlation functions C(N,N;{lambda}) of the two-dimensional Ising model, using an earlier connection between diagonal form factor expansions and tau-functions within Painleve VI (PVI) theory, originally discovered by Jimbo and Miwa. This greatly simplifies the calculation of the diagonal correlation functions, particularly their {lambda}-extended counterparts. We also conjecture a closed form expression for the simplest off-diagonal case C{sup {+-}}(0,1;{lambda}) where a connection to PVI theory is not known. Combined with the results for diagonal correlations these give all the initial conditions required for the {lambda}-extended version of quadratic difference equations for the correlation functions discovered by McCoy, Perk and Wu. The results obtained here should provide a further potential algorithmic improvement in the {lambda}-extended case, and facilitate other developments.
Interannual variability of carbon cycle implied by a 2-D atmospheric transport model
Institute of Scientific and Technical Information of China (English)
LI Can; XU Li; SHAO Min; ZHANG Ren-jian
2004-01-01
A 2-dimensional atmospheric transport model is deployed in a simplified CO2 inverse study. Calculated carbon flux distribution for the interval from 1981 to 1997 confirms the existence of a terrestrial carbon sink in mid-high latitude area of North Hemisphere. Strong interannual variability exists in carbon flux patterns, implying a possible link with ENSO and other natural episodes such as Pinatubo volcano eruption in 1991. Mechanism of this possible link was investigated with statistic method. Correlation analysis indicated that in North Hemisphere, climatic factors such as temperature and precipitation, to some extend, could influence the carbon cycle process of land and ocean, thus cause considerable change in carbon flux distribution. In addition, correlation study also demonstrated the possible important role of Asian terrestrial ecosystems in carbon cycle.
Superconducting correlations and thermodynamic properties in 2D square and triangular t-J model
Ogata, Masao
2006-03-01
Equal-time superconducting correlation functions of the two-dimensional t-J model on the square lattice are studied using high-temperature expansion method.[1] The sum of the pairing correlation, its spatial dependence and correlation length are obtained down to T ˜0.2t. By comparison of single-particle contributions in the correlation functions, we find effective attractive interactions between quasi-particles in dx^2-y^2-wave channel. It is shown that d-wave correlation grows rapidly at low temperatures for the doping 0.1 0 with hole doping, a rapid growth of effective d-wave paring interaction is found that indicates the resonating-valence-bond superconductivity. In contrast, when tJ. Phys. Soc. Japan 74, 1390 (2005). [2] T. Koretsune and M. Ogata, Phys. Rev. Lett. 89, 116401 (2002), and Phys. Rev. B72, 134513 (2005).
A boundary field induced first-order transition in the 2D Ising model: numerical study
Energy Technology Data Exchange (ETDEWEB)
Bittner, Elmar; Janke, Wolfhard [Institut fuer Theoretische Physik and Centre for Theoretical Sciences (NTZ), Universitaet Leipzig, Postfach 100 920, D-04009 Leipzig (Germany)], E-mail: elmar.bittner@itp.uni-leipzig.de, E-mail: Wolfhard.janke@itp.uni-leipzig.de
2008-10-03
In a recent paper, Clusel and Fortin (2006 J. Phys. A: Math. Gen. 39 995) presented an analytical study of a first-order transition induced by an inhomogeneous boundary magnetic field in the two-dimensional Ising model. They identified the transition that separates the regime where the interface is localized near the boundary from that where it propagates inside the bulk. Inspired by these results, we measured the interface tension by using multimagnetic simulations combined with parallel tempering to determine the phase transition and the location of the interface. Our results are in very good agreement with the theoretical predictions. Furthermore, we studied the spin-spin correlation function for which no analytical results are available.
Generando entrelazamiento en cadenas XY - (Generating entanglement in XY chains)
Schmiegelow, C T
2006-01-01
Se estudia en este trabajo la capacidad de generar entrelazamiento de una cadena de espines con acoplamiento de Heisenberg XY y un campo magnetico uniforme a partir de un estado inicial en el que los espines estan completamente alineados. Se encuentra que la capacidad de generar estados entrelazados no muestra un comportamiento monotono con el campo presentando, en cambio, plateaus y resonancias. Tambien se muestra que, a pesar de que la anisotropia es necesaria para que se generen estados entrelazados, una mayor anisotropia no implica necesariamente mejores condiciones para generar entrelazamiento que sirva para usarse en una computadora cuantica. Inclusive, se observa que, se genera una cantidad finita de entrelazamiento en el limite de pequena anisotropia. (The maximum entanglement reached by an initially fully aligned state evolving in a XY Heisenberg spin chain placed in a uniform transverse magnetic field is studied. It is shown that the capacity to create entangled states (both of one qubit with the re...
Time-Dependent 2D Modeling of Magnetron Plasma Torch in Turbulent Flow
Institute of Scientific and Technical Information of China (English)
LI Lincun; XIA Weidong
2008-01-01
A theoretical model is presented to describe the electromagnetic, heat transfer and fluid flow phenomena within a magnetron plasma torch and in the resultant plume, by using a commercial computational fluid dynamics (CFD) code FLUENT. Specific calculations are pre-sented for a pure argon system (i.e., an argon plasma discharging into an argon environment), operated in a turbulent mode. An important finding of this work is that the external axial mag-netic field (AMF) may have a significant effect on the behavior of arc plasma and thus affects the resulting plume. The AMF impels the plasma to retract axially and expand radially. As a result, the plasma intensity distribution on the cross section of torch seems to be more uniform. Numerical results also show that with AMF, the highest plasma temperature decreases and the anode arc root moves upstream significantly, while the current density distribution at the anode is more concentrated with a higher peak value. In addition, the use of AMF then induces a strong backflow at the torch spout and its magnitude increases with the AMF strength but decreases with the inlet gas velocity.
Computational study of a magnetic design to improve the diagnosis of malaria: 2D model
Vyas, Siddharth; Genis, Vladimir; Friedman, Gary
2017-02-01
This paper investigates the feasibility of a cost effective high gradient magnetic separation based device for the detection and identification of malaria parasites in a blood sample. The design utilizes magnetic properties of hemozoin present in malaria-infected red blood cells (mRBCs) in order to separate and concentrate them inside a microfluidic channel slide for easier examination under the microscope. The design consists of a rectangular microfluidic channel with multiple magnetic wires positioned on top of and underneath it along the length of the channel at a small angle with respect to the channel axis. Strong magnetic field gradients, produced by the wires, exert sufficient magnetic forces on the mRBCs in order to separate and concentrate them in a specific region small enough to fit within the microscope field of view at magnifications typically required to identify the malaria parasite type. The feasibility of the device is studied using a model where the trajectories of the mRBCs inside the channel are determined using first-order ordinary differential equations (ODEs) solved numerically using a multistep ODE solver available within MATLAB. The mRBCs trajectories reveal that it is possible to separate and concentrate the mRBCs in less than 5 min, even in cases of very low parasitemia (1-10 parasites/μL of blood) using blood sample volumes of around 3 μL employed today.
Pseudo-topological transitions in 2D gravity models coupled to massless scalar fields
Energy Technology Data Exchange (ETDEWEB)
Ambjorn, J., E-mail: ambjorn@nbi.dk [The Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, 2100 Copenhagen O (Denmark); Goerlich, A.T., E-mail: goerlich@nbi.dk [Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, 2100 Copenhagen O (Denmark); Mark Kac Complex Systems Research Centre, Marian Smoluchowski Institute of Physics, Jagellonian University, Reymonta 4, 30-059 Krakow (Poland); Jurkiewicz, J., E-mail: jerzy.jurkiewicz@uj.edu.pl [Mark Kac Complex Systems Research Centre, Marian Smoluchowski Institute of Physics, Jagellonian University, Reymonta 4, 30-059 Krakow (Poland); Zhang, H.-G., E-mail: zhang@th.if.uj.edu.pl [Mark Kac Complex Systems Research Centre, Marian Smoluchowski Institute of Physics, Jagellonian University, Reymonta 4, 30-059 Krakow (Poland)
2012-10-11
We study the geometries generated by two-dimensional causal dynamical triangulations (CDT) coupled to d massless scalar fields. Using methods similar to those used to study four-dimensional CDT we show that there exists a c=1 'barrier', analogous to the c=1 barrier encountered in non-critical string theory, only the CDT transition is easier to be detected numerically. For d Less-Than-Or-Slanted-Equal-To 1 we observe time-translation invariance and geometries entirely governed by quantum fluctuations around the uniform toroidal topology put in by hand. For d>1 the effective average geometry is no longer toroidal but 'semiclassical' and spherical with Hausdorff dimension d{sub H}=3. In the d>1 sector we study the time dependence of the semiclassical spatial volume distribution and show that the observed behavior is described by an effective mini-superspace action analogous to the actions found in the de Sitter phase of three- and four-dimensional pure CDT simulations and in the three-dimensional CDT-like Horava-Lifshitz models.
Thermodynamics and Kinetic Theory of Relativistic Gases in 2-D Cosmological Models
Kremer, G M
2002-01-01
A kinetic theory of relativistic gases in a two-dimensional space is developed in order to obtain the equilibrium distribution function and the expressions for the fields of energy per particle, pressure, entropy per particle and heat capacities in equilibrium. Furthermore, by using the method of Chapman and Enskog for a kinetic model of the Boltzmann equation the non-equilibrium energy-momentum tensor and the entropy production rate are determined for a universe described by a two-dimensional Robertson-Walker metric. The solutions of the gravitational field equations that consider the non-equilibrium energy-momentum tensor - associated with the coefficient of bulk viscosity - show that opposed to the four-dimensional case, the cosmic scale factor attains a maximum value at a finite time decreasing to a "big crunch" and that there exists a solution of the gravitational field equations corresponding to a "false vacuum". The evolution of the fields of pressure, energy density and entropy production rate with th...
Hassan, Ehab; Hatch, D. R.; Morrison, P. J.; Horton, W.
2016-09-01
Progress in understanding the coupling between plasma instabilities in the equatorial electrojet based on a unified fluid model is reported. Simulations with parameters set to various ionospheric background conditions revealed properties of the gradient-drift and Farley-Buneman instabilities. Notably, sharper density gradients increase linear growth rates at all scales, whereas variations in cross-field E × B drift velocity only affect small-scale instabilities. A formalism defining turbulent fluctuation energy for the system is introduced, and the turbulence is analyzed within this framework. This exercise serves as a useful verification test of the numerical simulations and also elucidates the physics underlying the ionospheric turbulence. Various physical mechanisms involved in the energetics are categorized as sources, sinks, nonlinear transfer, and cross-field coupling. The physics of the nonlinear transfer terms is studied to identify their roles in producing energy cascades, which explain the generation of small-scale structures that are stable in the linear regime. The theory of two-step energy cascading to generate the 3 m plasma irregularities in the equatorial electrojet is verified for the first time in the fluid regime. In addition, the nonlinearity of the system allows the possibility of an inverse energy cascade, potentially responsible for generating large-scale plasma structures at the top of the electrojet as found in different rocket and radar observations.
Process Parameters Optimization of 14nm MOSFET Using 2-D Analytical Modelling
Directory of Open Access Journals (Sweden)
Noor Faizah Z.A.
2016-01-01
Full Text Available This paper presents the modeling and optimization of 14nm gate length CMOS transistor which is down-scaled from previous 32nm gate length. High-k metal gate material was used in this research utilizing Hafnium Dioxide (HfO2 as dielectric and Tungsten Silicide (WSi2 and Titanium Silicide (TiSi2 as a metal gate for NMOS and PMOS respectively. The devices are fabricated virtually using ATHENA module and characterized its performance evaluation via ATLAS module; both in Virtual Wafer Fabrication (VWF of Silvaco TCAD Tools. The devices were then optimized through a process parameters variability using L9 Taguchi Method. There were four process parameter with two noise factor of different values were used to analyze the factor effect. The results show that the optimal value for both transistors are well within ITRS 2013 prediction where VTH and IOFF are 0.236737V and 6.995705nA/um for NMOS device and 0.248635 V and 5.26nA/um for PMOS device respectively.
2D condensation model for the inner Solar Nebula: an enstatite-rich environment
Pignatale, Francesco C; Maddison, Sarah T; Brooks, Geoffrey
2016-01-01
Infrared observations provide the dust composition in the protoplanetary discs surface layers, but can not probe the dust chemistry in the midplane, where planet formation occurs. Meteorites show that dynamics was important in determining the dust distribution in the Solar Nebula and needs to be considered if we are to understand the global chemistry in discs. 1D radial condensation sequences can only simulate one disc layer at a time and cannot describe the global chemistry or the complexity of meteorites. To address these limitations, we compute for the first time the two dimensional distribution of condensates in the inner Solar Nebula using a thermodynamic equilibrium model, and derive timescales for vertical settling and radial migration of dust. We find two enstatite-rich zones within 1 AU from the young Sun: a band ~0.1 AU thick in the upper optically-thin layer of the disc interior to 0.8 AU, and in the optically-thick disc midplane out to ~0.4 AU. The two enstatite-rich zones support recent evidence ...
Generando entrelazamiento en cadenas XY - (Generating entanglement in XY chains)
Schmiegelow, C. T.
2006-01-01
Se estudia en este trabajo la capacidad de generar entrelazamiento de una cadena de espines con acoplamiento de Heisenberg XY y un campo magnetico uniforme a partir de un estado inicial en el que los espines estan completamente alineados. Se encuentra que la capacidad de generar estados entrelazados no muestra un comportamiento monotono con el campo presentando, en cambio, plateaus y resonancias. Tambien se muestra que, a pesar de que la anisotropia es necesaria para que se generen estados en...
Zhao, Dongmiao; Tang, Jun; Wu, Xiuguang; Lin, Changning; Liu, Lijun; Chen, Jian
2016-05-01
A 2D vertical (2DV) numerical model, without σ-coordinate transformation in the vertical direction, is developed for the simulation of fl ow and sediment transport in open channels. In the model, time-averaged Reynolds equations are closed by the k-ɛ nonlinear turbulence model. The modifi ed Youngs-VOF method is introduced to capture free surface dynamics, and the free surface slope is simulated using the ELVIRA method. Based on the power-law scheme, the k-ɛ model and the suspended-load transport model are solved numerically with an implicit scheme applied in the vertical plane and an explicit scheme applied in the horizontal plane. Bedload transport is modeled using the Euler-WENO scheme, and the grid-closing skill is adopted to deal with the moving channel bed boundary. Verifi cation of the model using laboratory data shows that the model is able to adequately simulate fl ow and sediment transport in open channels, and is a good starting point for the study of sediment transport dynamics in strong nonlinear fl ow scenarios.
A 2D hydrodynamic-sedimentological model for gravel-bed rivers. Part I: theory and validation
Directory of Open Access Journals (Sweden)
Gabriel Kaless
2013-09-01
Full Text Available This paper presents a novel 2D-depth average model especially developed for gravel-bed rivers, named Lican-Leufú (Lican=pebble and Leufu=river, in Mapuche’s language, the native inhabitants of Central Patagonia, Argentina. The model consists of three components: a hydrodynamic, a sedimentological, and a morphological model. The flow of water is described by the depth-averaged Reynolds equations for unsteady, free-surface, shallow water flows. It includes the standard k-e model for turbulence closure. Sediment transport can be divided in different size classes (sand-gravel mixture and the equilibrium approach is used for Exner’s equation. The amour layer is also included in the structure of the model and the surface grain size distribution is also allowed to evolve. The model simulates bank slides that enable channel widening. Models predictions were tested against a flume experiment where a static armour layer was developed under conditions of sediment starvations and general good agreements were found: the model predicted adequately the sediment transport, grain size of transported material, final armour grain size distribution and bed elevation.
Guzik, Joyce A; Nelson, N J; Lovekin, C; Kosak, K; Kitiashvili, I N; Mansour, N N; Kosovichev, A
2016-01-01
We present multidimensional modeling of convection and oscillations in main-sequence stars somewhat more massive than the Sun, using three separate approaches: 1) Using the 3-D planar StellarBox radiation hydrodynamics code to model the envelope convection zone and part of the radiative zone. Our goals are to examine the interaction of stellar pulsations with turbulent convection in the envelope, excitation of acoustic modes, and the role of convective overshooting; 2) Applying the spherical 3-D MHD ASH (Anelastic Spherical Harmonics) code to simulate the core convection and radiative zone. Our goal is to determine whether core convection can excite low-frequency gravity modes, and thereby explain the presence of low frequencies for some hybrid gamma Doradus/delta Scuti variables for which the envelope convection zone is too shallow for the convective blocking mechanism to drive gravity modes; 3) Applying the ROTORC 2-D stellar evolution and dynamics code to calculate evolution with a variety of initial rotat...
Institute of Scientific and Technical Information of China (English)
V.MEDINA; A.BATEMAN; M.H(U)RLIMANN
2008-01-01
FLATModel is a 2D finite volume code that contains several original approaches to improve debris-flow simulation.Firstly,FLATModel incorporates a "stop-and-go" technique in each cell to allow continuous collapses and remobilizations of the debris-flow mass.Secondly,flow velocity and consequently yield stress is directly associated with the type of rheology to improve boundary accuracy.Thirdly,a simple approach for entrainment is also included in the model to analyse the effect of basal erosion of debris flows.FLATMODEL was tested at several events that occurred in the Eastern Pyrenees and simulation results indicated that the model can represent rather well the different characteristics observed in the field.
Lithospheric architecture of the Levant Basin (Eastern Mediterranean region): A 2D modeling approach
Inati, Lama; Zeyen, Hermann; Nader, Fadi-Henri; Adelinet, Mathilde; Sursock, Alexandre; Rahhal, Muhsin Elie; Roure, Francois
2016-04-01
One of the major uncertainties regarding the Levant Basin, known to be the site of rifting in the Late Paleozoic and Early Mesozoic, concerns its deep crustal configuration despite numerous old and recent geophysical studies in this region. The aim of this study is to deduce the deep structure of the lithosphere underlying the easternmost Mediterranean region, in particular the Levant Basin and its margins, where the nature of the crust, continental versus oceanic, remains debated and has major implications on understanding the regional tectonic and thermal evolution, and on constraining potential petroleum systems. The algorithm used is a trial and error method that delivers the crustal thickness and the depth of the lithosphere-asthenosphere boundary (LAB) as well as the crustal density distribution by integrating surface heat flow data, free-air gravity anomaly, Geoid and topography data. Moho depth and crustal thickness were locally constrained by refraction data where available. The models representing two EW sections show a progressively attenuated crystalline crust in an EW direction (35 to 8 km). The SN section represents a 12 km thick crust to the south, thins to 9-7 km towards the Lebanese coast and reaches 20 km in the north. The crystalline crust is best interpreted as a strongly thinned continental crust under the Levant Basin, represented by two distinct components, an upper and a lower crust. Nevertheless, the Herodotus Basin shows a thin crust, likely oceanic, with a thickness between 6 and 10 kms. West of the Eratosthenes Seamount, a local crustal anomaly is interpreted to be the result of an underlying continental crust with a thickness of 13 kms. The Moho under the Arabian plate is 35-40 km deep and becomes shallower towards the Mediterranean coast. Within the Levant Basin, the Moho appears to be situated between 20 and 23 km, reaching 26 km in the Herodotus Basin. While depth to LAB is around 110 km under the Arabian and the Eurasian plates, it
Liu, Zhen; Qu, Hengliang; Shi, Hongda; Hu, Gexing; Hyun, Beom-Soo
2016-12-01
Tidal current energy is renewable and sustainable, which is a promising alternative energy resource for the future electricity supply. The straight-bladed vertical-axis turbine is regarded as a useful tool to capture the tidal current energy especially under low-speed conditions. A 2D unsteady numerical model based on Ansys-Fluent 12.0 is established to conduct the numerical simulation, which is validated by the corresponding experimental data. For the unsteady calculations, the SST model, 2×105 and 0.01 s are selected as the proper turbulence model, mesh number, and time step, respectively. Detailed contours of the velocity distributions around the rotor blade foils have been provided for a flow field analysis. The tip speed ratio (TSR) determines the azimuth angle of the appearance of the torque peak, which occurs once for a blade in a single revolution. It is also found that simply increasing the incident flow velocity could not improve the turbine performance accordingly. The peaks of the averaged power and torque coefficients appear at TSRs of 2.1 and 1.8, respectively. Furthermore, several shapes of the duct augmentation are proposed to improve the turbine performance by contracting the flow path gradually from the open mouth of the duct to the rotor. The duct augmentation can significantly enhance the power and torque output. Furthermore, the elliptic shape enables the best performance of the turbine. The numerical results prove the capability of the present 2D model for the unsteady hydrodynamics and an operating performance analysis of the vertical tidal stream turbine.
Institute of Scientific and Technical Information of China (English)
LIU Zhen; QU Hengliang; SHI Hongda; HU Gexing; HYUN Beom-Soo
2016-01-01
Tidal current energy is renewable and sustainable, which is a promising alternative energy resource for the future elec-tricity supply. The straight-bladed vertical-axis turbine is regarded as a useful tool to capture the tidal current energy especially under low-speed conditions. A 2D unsteady numerical model based on Ansys-Fluent 12.0 is established to conduct the numerical simulation, which is validated by the corresponding experimental data. For the unsteady calculations, the SST model, 2×105and 0.01s are se-lected as the proper turbulence model, mesh number, and time step, respectively. Detailed contours of the velocity distributions around the rotor blade foils have been provided for a flow field analysis. The tip speed ratio (TSR) determines the azimuth angle of the appearance of the torque peak, which occurs once for a blade in a single revolution. It is also found that simply increasing the incident flow velocity could not improve the turbine performance accordingly. The peaks of the averaged power and torque coeffi-cients appear at TSRs of 2.1 and 1.8, respectively. Furthermore, several shapes of the duct augmentation are proposed to improve the turbine performance by contracting the flow path gradually from the open mouth of the duct to the rotor. The duct augmentation can significantly enhance the power and torque output. Furthermore, the elliptic shape enables the best performance of the turbine. The numerical results prove the capability of the present 2D model for the unsteady hydrodynamics and an operating performance analy-sis of the vertical tidal stream turbine.
Institute of Scientific and Technical Information of China (English)
LI WeiFeng; CHEN QiuWen; MAO JingQiao
2009-01-01
Urban inundation due to anomalous storms is a serious problem for many cities worldwide. Therefore, it is important to accurately simulate urban hydrological processes and efficiently predict the potential risks of urban floods for the improvement of drainage designs and implementation of emergency ac-tions. However, the complexity of urban landforma and the diversity of hydraulic infrastructure pose particular challenges for the simulation and risk assessment of urban drainage processes. This study developed a methodology to comprehensively simulate inundation processes by dynamically coupling 1D and 2D hydrodynamic models. By allowing the simultaneous solution of the processes of rainfall and runoff, urban drainage, and flooding, this method can be used to estimate the potential inundation risks of any designed drainage system. Furthermore, a Geographical Information System (GIS) based platform was fully integrated with the model engine to effectively illustrate the context of the problem. The developed model was then demonstrated on the Beijing 2008 Olympic Village under the conditions of the 5-year and 50-year design storms. The sewer discharge, channel discharge, and flood propaga-tion (inundation initiation, extent, depths, and duration) were numerically validated and analyzed. The results identified the potential inundation risks. From the study, it is found that the coupled GIS and 1D and 2D hydrodynamic models have the potential to simulate urban inundation processes, and hence efficiently predict flood risks and support cost-effective drainage design and management. It also im-plies promising prospects about the wide availability of high quality digital data, GIS techniques, and well-developed monitoring infrastructure to develop online urban inundation forecasts.
Campforts, Benjamin; Vanacker, Veerle; Vanderborght, Jan; Baken, Stijn; Smolders, Erik; Govers, Gerard
2016-04-01
Meteoric 10Be allows for the quantification of vertical and lateral soil fluxes over long time scales (103-105 yr). However, the mobility of meteoric 10Be in the soil system makes a translation of meteoric 10Be inventories into erosion and deposition rates complex. Here, we present a spatially explicit 2D model simulating the behaviour of meteoric 10Be on a hillslope. The model consists of two parts. The first component deals with advective and diffusive mobility of meteoric 10Be within the soil profile, and the second component describes lateral soil and meteoric 10Be fluxes over the hillslope. Soil depth is calculated dynamically, accounting for soil production through weathering as well as downslope fluxes of soil due to creep, water and tillage erosion. Synthetic model simulations show that meteoric 10Be inventories can be related to erosion and deposition across a wide range of geomorphological and pedological settings. Our results also show that meteoric 10Be can be used as a tracer to detect human impact on soil fluxes for soils with a high affinity for meteoric 10Be. However, the quantification of vertical mobility is essential for a correct interpretation of the observed variations in meteoric 10Be profiles and inventories. Application of the Be2D model to natural conditions using data sets from the Southern Piedmont (Bacon et al., 2012) and Appalachian Mountains (Jungers et al., 2009; West et al., 2013) allows to reliably constrain parameter values. Good agreement between simulated and observed meteoric 10Be concentrations and inventories is obtained with realistic parameter values. Furthermore, our results provide detailed insights into the processes redistributing meteoric 10Be at the soil-hillslope scale.
Le Roux, Olivier; Cornou, Cécile; Jongmans, Denis; Schwartz, Stéphane
2012-09-01
H/V spectral ratios are regularly used for estimating the bedrock depth in 1-D like basins exhibiting smooth lateral variations. In the case of 2-D or 3-D pronounced geometries, observational and numerical studies have shown that H/V curves exhibit peculiar shapes and that the H/V frequency generally overestimates 1-D theoretical resonance frequency. To investigate the capabilities of the H/V method in complex structures, a detailed comparison between measured and 3-D-simulated ambient vibrations was performed in the small-size lower Romanche valley (French Alps), which shows significant variations in geometry, downstream and upstream the Séchilienne basin. Analysing the H/V curve characteristics, two different wave propagation modes were identified along the valley. Relying on previous geophysical investigation, a power-law relationship was derived between the bedrock depth and the H/V peak frequency, which was used for building a 3-D model of the valley geometry. Simulated and experimental H/V curves were found to exhibit quite similar features in terms of curve shape and peak frequency values, validating the 3-D structure. This good agreement also evidenced two different propagation modes in the valley: 2-D resonance in the Séchilienne basin and 1-D resonance in the external parts. This study underlines the interest of H/V curves for investigating complex basin structures.
Directory of Open Access Journals (Sweden)
Gabriel Kaless
2013-09-01
Full Text Available A 2D depth average model has been used to simulate water and sediment flow in the Brenta River so as to interpret channel changes and to assess model predictive capabilities. The Brenta River is a gravel bed river located in Northern Italy. The study reach is 1400 long and has a mean slope of 0.0056. High resolution digital terrain models has been produced combining laser imaging detection and ranging data with colour bathymetry techniques. Extensive field sedimentological surveys have been also carried out for surface and subsurface material. The data were loaded in the model and the passage of a high intense flood (R.I. > 9 years was simulated. The model was run under the hypothesis of a substantial equilibrium between sediment input and transport capacity. In this way, the model results were considered as a reference condition, and the potential trend of the reach was assessed. Low-frequency floods (R.I. » 1.5 years are expected to produce negligible changes in the channel while high floods may focalize erosion on banks instead than on channel bed. Furthermore, the model predicts well the location of erosion and siltation areas and the results promote its application to other reaches of the Brenta River in order to assess their stability and medium-term evolution.
QSAR modeling of toxicity of diverse organic chemicals to Daphnia magna using 2D and 3D descriptors
Energy Technology Data Exchange (ETDEWEB)
Kar, Supratik [Drug Theoretics and Cheminformatics Laboratory, Department of Pharmaceutical Technology, Jadavpur University, Raja S C Mullick Road, Kolkata 700032 (India); Roy, Kunal, E-mail: kunalroy_in@yahoo.com [Drug Theoretics and Cheminformatics Laboratory, Department of Pharmaceutical Technology, Jadavpur University, Raja S C Mullick Road, Kolkata 700032 (India)
2010-05-15
One of the major economic alternatives to experimental toxicity testing is the use of quantitative structure-activity relationships (QSARs) which are used in formulating regulatory decisions of environmental protection agencies. In this background, we have modeled a large diverse group of 297 chemicals for their toxicity to Daphnia magna using mechanistically interpretable descriptors. Three-dimensional (3D) (electronic and spatial) and two-dimensional (2D) (topological and information content indices) descriptors along with physicochemical parameter log K{sub o/w} (n-octanol/water partition coefficient) and structural descriptors were used as predictor variables. The QSAR models were developed by stepwise multiple linear regression (MLR), partial least squares (PLS), genetic function approximation (GFA), and genetic PLS (G/PLS). All the models were validated internally and externally. Among several models developed using different chemometric tools, the best model based on both internal and external validation characteristics was a PLS equation with 7 descriptors and three latent variables explaining 67.8% leave-one-out predicted variance and 74.1% external predicted variance. The PLS model suggests that higher lipophilicity and electrophilicity, less negative charge surface area and presence of ether linkage, hydrogen bond donor groups and acetylenic carbons are responsible for greater toxicity of chemicals. The developed model may be used for prediction of toxicity, safety and risk assessment of chemicals to achieve better ecotoxicological management and prevent adverse health consequences.
Lanty, Gaëtan; Jemli, Khaoula; Wei, Yi; Leymarie, Joël; Even, Jacky; Lauret, Jean-Sébastien; Deleporte, Emmanuelle
2014-11-20
We focus here our attention on a particular family of 2D-layered and 3D hybrid perovskite molecular crystals, the mixed perovskites (C6H5-C2H4-NH3)2PbZ4(1-x)Y4x and (CH3-NH3)PbZ3(1-x)Y3x, where Z and Y are halogen ions such as I, Br, and Cl. Studying experimentally the disorder-induced effects on the optical properties of the 2D mixed layered materials, we demonstrate that they can be considered as pseudobinary alloys, exactly like Ga1-xAlxAs, Cd1-xHgxTe inorganic semiconductors, or previously reported 3D mixed hybrid perovskite compounds. 2D-layered and 3D hybrid perovskites afford similar continuous optical tunability at room temperature. Our theoretical analysis allows one to describe the influence of alloying on the excitonic properties of 2D-layered perovskite molecular crystals. This model is further refined by considering different Bohr radii for pure compounds. This study confirms that despite a large binding energy of several 100 meV, the 2D excitons present a Wannier character rather than a Frenkel character. The small inhomogeneous broadening previously reported in 3D hybrid compounds at low temperature is similarly consistent with the Wannier character of free excitons.
GPU computing for 2-d spin systems: CUDA vs OpenGL
Anselmi, V; Di Renzo, F
2008-01-01
In recent years the more and more powerful GPU's available on the PC market have attracted attention as a cost effective solution for parallel (SIMD) computing. CUDA is a solid evidence of the attention that the major companies are devoting to the field. CUDA is a hardware and software architecture developed by Nvidia for computing on the GPU. It qualifies as a friendly alternative to the approach to GPU computing that has been pioneered in the OpenGL environment. We discuss the application of both the CUDA and the OpenGL approach to the simulation of 2-d spin systems (XY model).
Energy Technology Data Exchange (ETDEWEB)
Huang, M.J.; Eames, P.C. [Centre for Sustainable Technologies, School of the Built Environment, University of Ulster, Newtownabbey, BT37 0QB, N.Ireland (United Kingdom); Norton, B. [FOCAS Institute, Dublin Institute of Technology, Aungier Street, Dublin 2 (Ireland)
2006-08-15
A three-dimensional (3D) numerical model was developed to simulate the use of a phase change material linked to a photovoltaic (PV) system to control the temperature rise of the PV cells. The model can be used to predict temperatures, velocity fields and vortex formation within the system. The 3D predictions have been compared with those from a previously developed experimental validated two-dimensional (2D) finite-volume heat transfer model conjugated hydro-dynamically to solve the Navier-Stokes and energy equations. It was found that for the systems simulated with appropriate boundary conditions, the 2D model predictions compare well with those of the 3D model. The 3D model was used to predict the temperature distributions when the heat transfer to the phase change material was enhanced by high thermal conductivity pin fins. (author)
Directory of Open Access Journals (Sweden)
J. P. McCormack
2006-01-01
Full Text Available The new CHEM2D-Ozone Photochemistry Parameterization (CHEM2D-OPP for high-altitude numerical weather prediction (NWP systems and climate models specifies the net ozone photochemical tendency and its sensitivity to changes in ozone mixing ratio, temperature and overhead ozone column based on calculations from the CHEM2D interactive middle atmospheric photochemical transport model. We evaluate CHEM2D-OPP performance using both short-term (6-day and long-term (1-year stratospheric ozone simulations with the prototype high-altitude NOGAPS-ALPHA forecast model. An inter-comparison of NOGAPS-ALPHA 6-day ozone hindcasts for 7 February 2005 with ozone photochemistry parameterizations currently used in operational NWP systems shows that CHEM2D-OPP yields the best overall agreement with both individual Aura Microwave Limb Sounder ozone profile measurements and independent hemispheric (10°–90° N ozone analysis fields. A 1-year free-running NOGAPS-ALPHA simulation using CHEM2D-OPP produces a realistic seasonal cycle in zonal mean ozone throughout the stratosphere. We find that the combination of a model cold temperature bias at high latitudes in winter and a warm bias in the CHEM2D-OPP temperature climatology can degrade the performance of the linearized ozone photochemistry parameterization over seasonal time scales despite the fact that the parameterized temperature dependence is weak in these regions.
Tian, Junfang; Ma, Shoufeng; Zhu, Chenqiang; Jiang, Rui; Ding, YaoXian
2015-01-01
This paper proposes an improved cellular automaton traffic flow model based on the brake light model, which takes into account that the desired time gap of vehicles is remarkably larger than one second. Although the hypothetical steady state of vehicles in the deterministic limit corresponds to a unique relationship between speeds and gaps in the proposed model, the traffic states of vehicles dynamically span a two-dimensional region in the plane of speed versus gap, due to the various randomizations. It is shown that the model is able to well reproduce (i) the free flow, synchronized flow, jam as well as the transitions among the three phases; (ii) the evolution features of disturbances and the spatiotemporal patterns in a car-following platoon; (iii) the empirical time series of traffic speed obtained from NGSIM data. Therefore, we argue that a model can potentially reproduce the empirical and experimental features of traffic flow, provided that the traffic states are able to dynamically span a 2D speed-gap...
Schaa, R.; Gross, L.; du Plessis, J.
2016-04-01
We present a general finite-element solver, escript, tailored to solve geophysical forward and inverse modeling problems in terms of partial differential equations (PDEs) with suitable boundary conditions. Escript’s abstract interface allows geoscientists to focus on solving the actual problem without being experts in numerical modeling. General-purpose finite element solvers have found wide use especially in engineering fields and find increasing application in the geophysical disciplines as these offer a single interface to tackle different geophysical problems. These solvers are useful for data interpretation and for research, but can also be a useful tool in educational settings. This paper serves as an introduction into PDE-based modeling with escript where we demonstrate in detail how escript is used to solve two different forward modeling problems from applied geophysics (3D DC resistivity and 2D magnetotellurics). Based on these two different cases, other geophysical modeling work can easily be realized. The escript package is implemented as a Python library and allows the solution of coupled, linear or non-linear, time-dependent PDEs. Parallel execution for both shared and distributed memory architectures is supported and can be used without modifications to the scripts.
Dages, Cecile; Samouelian, Anatja; Lanoix, Marthe; Dollinger, Jeanne; Chakkour, Sara; Chovelon, Gabrielle; Trabelsi, Khouloud; Voltz, Marc
2015-04-01
Ditches are involved in the transfer of pesticide to surface and groundwaters (e.g. Louchart et al., 2001). Soil horizons underlying ditch beds may present specific soil characteristics compared to neighbouring field soils due to erosion/deposition processes, to the specific biological activities (rooting dynamic and animal habitat) in the ditches (e.g. Vaughan et al., 2008) and to management practices (burning, dredging, mowing,...). Moreover, in contrast to percolation processes in field soils that can be assumed to be mainly 1D vertical, those occurring in the ditch beds are by essence 2D or even 3D. Nevertheless, due to a lake of knowledge, these specific aspects of transfer within ditch beds are generally omitted for hydrological simulation at the catchment scale (Mottes et al., 2014). Accordingly, the aims of this study were i) to characterize subsurface solute transfer through ditch beds and ii) to determine equivalent hydraulic parameters of the ditch beds for use in catchment scale hydrological simulations. A complementary aim was to evaluate the error in predictions performed when percolation in ditches is assumed to be similar to that in the neighbouring field soil. First, bromide transfer experiments were performed on undisturbed soil column (15 cm long with a 15 cm inner-diameter), horizontally and vertically sampled within each soil horizon underlying a ditch bed and within the neighboring field. Columns were sampled at the Roujan catchment (Hérault, France), which belongs to the long term Mediterranean hydrological observatory OMERE (Voltz and Albergel, 2002). Second, for each column, a set of parameters was determined by inverse optimization with mobile-immobile or dual permeability models, with CXTFIT (Toride et al., 1999) or with HYDRUS (Simunek et al., 1998). Third, infiltration and percolation in the ditch was simulated by a 2D flow domain approach considering the 2D variation in hydraulic properties of the cross section of a ditch bed. Last
Cea, L.; Legout, C.; Darboux, F.; Esteves, M.; Nord, G.
2014-05-01
This paper presents a validation of a two-dimensional overland flow model using empirical laboratory data. Unlike previous publications in which model performance is evaluated as the ability to predict an outlet hydrograph, we use high resolution 2D water depth and velocity data to analyze to what degree the model is able to reproduce the spatial distribution of these variables. Several overland flow conditions over two impervious surfaces of the order of one square meter with different micro and macro-roughness characteristics are studied. The first surface is a simplified representation of a sinusoidal terrain with three crests and furrows, while the second one is a mould of a real agricultural seedbed terrain. We analyze four different bed friction parameterizations and we show that the performance of formulations which consider the transition between laminar, smooth turbulent and rough turbulent flow do not improve the results obtained with Manning or Keulegan formulas for rough turbulent flow. The simulations performed show that using Keulegan formula with a physically-based definition of the bed roughness coefficient, a two-dimensional shallow water model is able to reproduce satisfactorily the flow hydrodynamics. It is shown that, even if the resolution of the topography data and numerical mesh are high enough to include all the small scale features of the bed surface, the roughness coefficient must account for the macro-roughness characteristics of the terrain in order to correctly reproduce the flow hydrodynamics.
Modeling Coastal Salinity in Quasi 2D and 3D Using a DUALEM-421 and Inversion Software.
Davies, Gareth; Huang, Jingyi; Monteiro Santos, Fernando Acacio; Triantafilis, John
2015-01-01
Rising sea levels, owing to climate change, are a threat to fresh water coastal aquifers. This is because saline intrusions are caused by increases and intensification of medium-large scale influences including sea level rise, wave climate, tidal cycles, and shifts in beach morphology. Methods are therefore required to understand the dynamics of these interactions. While traditional borehole and galvanic contact resistivity (GCR) techniques have been successful they are time-consuming. Alternatively, frequency-domain electromagnetic (FEM) induction is potentially useful as physical contact with the ground is not required. A DUALEM-421 and EM4Soil inversion software package are used to develop a quasi two- (2D) and quasi three-dimensional (3D) electromagnetic conductivity images (EMCI) across Long Reef Beach located north of Sydney Harbour, New South Wales, Australia. The quasi 2D models discern: the dry sand (dune; sand with fresh water (10 to 20 mS/m); mixing of fresh and saline water (20 to 500 mS/m), and; saline sand of varying moisture (more than 500 mS/m). The quasi 3D EMCIs generated for low and high tides suggest that daily tidal cycles do not have a significant effect on local groundwater salinity. Instead, the saline intrusion is most likely influenced by medium-large scale drivers including local wave climate and morphology along this wave-dominated beach. Further research is required to elucidate the influence of spring-neap tidal cycles, contrasting beach morphological states and sea level rise.
From 2D to 3D--a New Dimension for Modelling the Effect of Natural Products on Human Tissue.
Wrzesinski, Krzysztof; Fey, Stephen J
2015-01-01
Natural products, or their synthetic derivatives are a treasure trove to find potential candidates for novel drugs for human treatment. The selection of diamonds from the huge pile of worthless stone is a critical--and difficult--stage in the discovery pipeline. Of all the factors to be considered, perhaps the most important, is that the compound should have the desired effect on the tissue in vivo. Since it is not possible (or ethical) to test all compounds in vivo one must preselect using a surrogate assay system. While animal models have the advantage of being holistic and current 3D culture systems are reductionistic, they at least can be constructed from human cell types. In this review we will consider some of the evidence demonstrating that cells grown in 3D cultures have physiological performances that mimic functions seen in human tissues significantly better than cells grown using classical 2D culture systems. We will discuss advantages and disadvantages of these new culture technologies and highlight theoretical reasons for the differences. 3D cell culture technologies are more labour intensive than 2D culture systems and therefore their introduction is a trade-off between the value of obtaining data that is more relevant to the human condition against their through-put. It is already clear that future in vitro 3D systems will become more complex, using multiple cell types to more faithfully represent a particular tissue or even organ system. And one thing is sure - the diamonds are not easy to find!
EDGE2D-EIRENE modelling of near SOL E r: possible impact on the H-mode power threshold
Chankin, A. V.; Delabie, E.; Corrigan, G.; Harting, D.; Maggi, C. F.; Meyer, H.; Contributors, JET
2017-04-01
Recent EDGE2D-EIRENE simulations of JET plasmas showed a significant difference between radial electric field (E r) profiles across the separatrix in two divertor configurations, with the outer strike point on the horizontal target (HT) and vertical target (VT) (Chankin et al 2016 Nucl. Mater. Energy, doi: 10.1016/j.nme.2016.10.004). Under conditions (input power, plasma density) where the HT plasma went into the H-mode, a large positive E r spike in the near scrape-off layer (SOL) was seen in the code output, leading to a very large E × B shear across the separatrix over a narrow region of a fraction of a cm width. No such E r feature was obtained in the code solution for the VT configuration, where the H-mode power threshold was found to be twice as high as in the HT configuration. It was hypothesised that the large E × B shear across the separatrix in the HT configuration could be responsible for the turbulence suppression leading to an earlier (at lower input power) L–H transition compared to the VT configuration. In the present work these ideas are extended to cover some other experimental observations on the H-mode power threshold variation with parameters which typically are not included in the multi-machine H-mode power threshold scalings, namely: ion mass dependence (isotope H–D–T exchange), dependence on the ion ∇B drift direction, and dependence on the wall material composition (ITER-like wall versus carbon wall in JET). In all these cases EDGE2D-EIRENE modelling shows larger positive E r spikes in the near SOL under conditions where the H-mode power threshold is lower, at least in the HT configuration.
Numerical model of water flow and solute accumulation in vertisols using HYDRUS 2D/3D code
Weiss, Tomáš; Dahan, Ofer; Turkeltub, Tuvia
2015-04-01
Keywords: dessication-crack-induced-salinization, preferential flow, conceptual model, numerical model, vadose zone, vertisols, soil water retention function, HYDRUS 2D/3D Vertisols cover a hydrologically very significant area of semi-arid regions often through which water infiltrates to groundwater aquifers. Understanding of water flow and solute accumulation is thus very relevant to agricultural activity and water resources management. Previous works suggest a conceptual model of dessication-crack-induced-salinization where salinization of sediment in the deep section of the vadose zone (up to 4 m) is induced by subsurface evaporation due to convective air flow in the dessication cracks. It suggests that the salinization is induced by the hydraulic gradient between the dry sediment in the vicinity of cracks (low potential) and the relatively wet sediment further from the main cracks (high potential). This paper presents a modified previously suggested conceptual model and a numerical model. The model uses a simple uniform flow approach but unconventionally prescribes the boundary conditions and the hydraulic parameters of soil. The numerical model is bound to one location close to a dairy farm waste lagoon, but the application of the suggested conceptual model could be possibly extended to all semi-arid regions with vertisols. Simulations were conducted using several modeling approaches with an ultimate goal of fitting the simulation results to the controlling variables measured in the field: temporal variation in water content across thick layer of unsaturated clay sediment (>10 m), sediment salinity and salinity the water draining down the vadose zone to the water table. The development of the model was engineered in several steps; all computed as forward solutions by try-and-error approach. The model suggests very deep instant infiltration of fresh water up to 12 m, which is also supported by the field data. The paper suggests prescribing a special atmospheric
Zheng, Liang; May, Dave; Gerya, Taras; Bostock, Michael
2016-08-01
Shear deformation, accompanied with fluid activity inside the subduction interface, is related to many tectonic energy-releasing events, including regular and slow earthquakes. We have numerically examined the fluid-rock interactions inside a deforming subduction interface using state-of-the-art 2-D hydromechanical numerical models, which incorporate the rock fracturing behavior as a plastic rheology which is dependent on the pore fluid pressure. Our modeling results suggest that two typical dynamical regimes of the deforming subduction interface exist, namely, a "coupled" and a "decoupled" regime. In the coupled regime the subduction interface is subdivided into multiple rigid blocks, each separated by a narrow shear zone inclined at an angle of 15-20° with respect to the slab surface. In contrast, in the decoupled regime the subduction interface is divided into two distinct layers moving relative to each other along a pervasive slab surface-parallel shear zone. Through a systematic parameter study, we observe that the tensile strength (cohesion) of the material within the subduction interface dictates the resulting style of deformation within the interface: high cohesion (~60 MPa) results in the coupled regime, while low cohesion (~10 MPa) leads to the decoupled regime. We also demonstrate that the lithostatic pressure and inflow/outflow fluid fluxes (i.e., fluid-fluxed boundary condition) influence the location and orientation of faults. Predictions from our numerical models are supported by experimental laboratory studies, geological data, and geophysical observations from modern subduction settings.
Kim, Ho Jun; Lee, Hae June
2016-06-01
The wide applicability of capacitively coupled plasma (CCP) deposition has increased the interest in developing comprehensive numerical models, but CCP imposes a tremendous computational cost when conducting a transient analysis in a three-dimensional (3D) model which reflects the real geometry of reactors. In particular, the detailed flow features of reactive gases induced by 3D geometric effects need to be considered for the precise calculation of radical distribution of reactive species. Thus, an alternative inclusive method for the numerical simulation of CCP deposition is proposed to simulate a two-dimensional (2D) CCP model based on the 3D gas flow results by simulating flow, temperature, and species fields in a 3D space at first without calculating the plasma chemistry. A numerical study of a cylindrical showerhead-electrode CCP reactor was conducted for particular cases of SiH4/NH3/N2/He gas mixture to deposit a hydrogenated silicon nitride (SiN x H y ) film. The proposed methodology produces numerical results for a 300 mm wafer deposition reactor which agree very well with the deposition rate profile measured experimentally along the wafer radius.
Li, Min; Wei, Dongbin; Zhao, Huimin; Du, Yuguo
2014-01-01
The genotoxicity of 21 quinolones antibiotics was determined using SOS/umu assay. Some quinolones exhibited high genotoxicity, and the chemical substituent on quinolone ring significantly affected genotoxicity. To establish the relationship between genotoxicity and substituent, a 2D-QSAR model based on quantum chemical parameters was developed. Calculation suggested that both steric and electrostatic properties were correlated well with genotoxicity. Furthermore, the specific effect on three key active sites (1-, 7- and 8-positions) of quinolone ring was investigated using a 3D-QSAR (comparative molecular field analysis, CoMFA) method. From our modeling, the genotoxicity increased when substituents had: (1) big volume and/or positive charge at 1-position; (2) negative charge at 7-position; and (3) small volume and/or negative charge at 8-position. The developed QSAR models were applicable to estimate genotoxicity of quinolones antibiotics and their transformation products. It is noted that some of the transformation products exhibited higher genotoxicity comparing to their precursor (e.g., ciprofloxacin). This study provided an alternative way to understand the molecule genotoxicity of quinolones derivatives, as well as to evaluate their potential environmental risks.
Multi-scale Model of Residual Strength of 2D Plain Weave C/SiC Composites in Oxidation Atmosphere
Chen, Xihui; Sun, Zhigang; Sun, Jianfen; Song, Yingdong
2016-06-01
Multi-scale models play an important role in capturing the nonlinear response of woven carbon fiber reinforced ceramic matrix composites. In plain weave carbon fiber/silicon carbon (C/SiC) composites, the carbon fibers and interphases will be oxidized at elevated temperature and the strength of the composite will be degraded when oxygen enters micro-cracks formed in the as-produced parts due to the mismatch in thermal properties between constituents. As a result of the oxidation on fiber surface, fiber shows a notch-like morphology. In this paper, the change rule of fiber notch depth is fitted by circular function. And a multi-scale model based upon the change rule of fiber notch depth is developed to simulate the residual strength and post-oxidation stress-strain curves of the composite. The multi-scale model is able to accurately predict the residual strength and post-oxidation stress-strain curves of the composite. Besides, the simulated residual strength and post-oxidation stress-strain curves of 2D plain weave C/SiC composites in oxidation atmosphere show good agreements with experimental results. Furthermore, the oxidation time and temperature of the composite are investigated to show their influences upon the residual strength and post-oxidation stress-strain curves of plain weave C/SiC composites.
Quark-Antiquark and Diquark Condensates in Vacuum in a 2D Two-Flavor Gross-Neveu Model
Bang-Rong, Z
2007-01-01
The analysis based on the renormalized effective potential indicates that, similar to in the 4D two-flavor Nambu-Jona-Lasinio (NJL) model, in a 2D two-flavor Gross-Neveu model, the interplay between the quark-antiquark and the diquark condensates in vacuum also depends on $G_S/H_S$, the ratio of the coupling constants in scalar quark-antiquark and scalar diquark channel. Only the pure quark-antiquark condensates exist if $G_S/H_S>2/3$ which is just the ratio of the color numbers of the quarks participating in the diquark and quark-antiquark condensates. The two condensates will coexist if $0
Understanding the impact of 2D and 3D fibroblast cultures on in vitro breast cancer models.
Directory of Open Access Journals (Sweden)
Kyung Eun Sung
Full Text Available The utilization of 3D, physiologically relevant in vitro cancer models to investigate complex interactions between tumor and stroma has been increasing. Prior work has generally focused on the cancer cells and, the role of fibroblast culture conditions on tumor-stromal cell interactions is still largely unknown. Here, we focus on the stroma by comparing functional behaviors of human mammary fibroblasts (HMFs cultured in 2D and 3D and their effects on the invasive progression of breast cancer cells (MCF10DCIS.com. We identified increased levels of several paracrine factors from HMFs cultured in 3D conditions that drive the invasive transition. Using a microscale co-culture model with improved compartmentalization and sensitivity, we demonstrated that HMFs cultured in 3D intensify the promotion of the invasive progression through the HGF/c-Met interaction. This study highlights the importance of the 3D stromal microenvironment in the development of multiple cell type in vitro cancer models.
The Moyal Momentum algebra applied to (theta)-deformed 2d conformal models and KdV-hierarchies
Boulahoual, A
2002-01-01
The properties of the Das-Popowicz Moyal momentum algebra that we introduce in hep-th/0207242 are reexamined in details and used to discuss some aspects of integrable models and 2d conformal field theories. Among the results presented, we setup some useful convention notations which lead to extract some non trivial properties of the Moyal momentum algebra. We use the particular sub-algebra sl(n)-{Sigma}_{n}^{(0,n)} to construct the sl(2)-Liouville conformal model and its sl(3)-Toda extension. We show also that the central charge, a la Feigin-Fuchs, associated to the spin-2 conformal current of the (theta)-Liouville model is given by c(theta)=1+24.theta^{2}. Moreover, the results obtained for the Das-Popowicz Mm algebra are applied to study systematically some properties of the Moyal KdV and Boussinesq hierarchies generalizing some known results. We discuss also the primarity condition of conformal $w_{\\theta}$-currents and interpret this condition as being a dressing gauge symmetry in the Moyal momentum space...
Hue, Vincent; Dobrijevic, Michel; Hersant, Franck; Greathouse, Thomas K
2015-01-01
Saturn's axial tilt of 26.7{\\deg} produces seasons in a similar way as on Earth. Both the stratospheric temperature and composition are affected by this latitudinally varying insolation along Saturn's orbital path. A new time dependent 2D photochemical model is presented to study the seasonal evolution of Saturn's stratospheric composition. This study focuses on the impact of the seasonally variable thermal field on the main stratospheric C2 hydrocarbon chemistry (C2H2 and C2H6) using a realistic radiative climate model. Meridional mixing and advective processes are implemented in the model but turned off in the present study for the sake of simplicity. The results are compared to a simple study case where a latitudinally and temporally steady thermal field is assumed. Our simulations suggest that, when the seasonally variable thermal field is accounted for, the downward diffusion of the seasonally produced hydrocarbons is faster due to the seasonal compression of the atmospheric column during winter. This ef...
Indian Academy of Sciences (India)
R Vidya Sagar; B K Raghu Prasad
2009-12-01
In this paper, numerical modelling of fracture in concrete using two-dimensional lattice model is presented and also a few issues related to lattice modelling technique applicable to concrete fracture are reviewed. A comparison is made with acoustic emission (AE) events with the number of fractured elements. To implement the heterogeneity of the plain concrete, two methods namely, by generating grain structure of the concrete using Fuller’s distribution and the concrete material properties are randomly distributed following Gaussian distribution are used. In the ﬁrst method, the modelling of the concrete at meso level is carried out following the existing methods available in literature. The shape of the aggregates present in the concrete are assumed as perfect spheres and shape of the same in two-dimensional lattice network is circular. A three-point bend (TPB) specimen is tested in the experiment under crack mouth opening displacement (CMOD) control at a rate of 0·0004 mm/sec and the fracture process in the same TPB specimen is modelled using regular triangular 2D lattice network. Load versus crack mouth opening displacement (CMOD) plots thus obtained by using both the methods are compared with experimental results. It was observed that the number of fractured elements increases near the peak load and beyond the peak load. That is once the crack starts to propagate. AE hits also increase rapidly beyond the peak load. It is compulsory here to mention that although the lattice modelling of concrete fracture used in this present study is very similar to those already available in literature, the present work brings out certain ﬁner details which are not available explicitly in the earlier works.
Dickschen, Kristin; Willmann, Stefan; Thelen, Kirstin; Lippert, Jörg; Hempel, Georg; Eissing, Thomas
2012-01-01
Tamoxifen is a first-line endocrine agent in the mechanism-based treatment of estrogen receptor positive (ER+) mammary carcinoma and applied to breast cancer patients all over the world. Endoxifen is a secondary and highly active metabolite of tamoxifen that is formed among others by the polymorphic cytochrome P450 2D6 (CYP2D6). It is widely accepted that CYP2D6 poor metabolizers exert a pronounced decrease in endoxifen steady-state plasma concentrations compared to CYP2D6 extensive metabolizers. Nevertheless, an in-depth understanding of the chain of cause and effect between CYP2D6 genotype, endoxifen steady-state plasma concentration, and subsequent tamoxifen treatment benefit still remains to be evolved. In this study, physiologically based pharmacokinetic (PBPK)-modeling was applied to mechanistically investigate the impact of CYP2D6 phenotype on endoxifen formation in female breast cancer patients undergoing tamoxifen therapy. A PBPK-model of tamoxifen and its pharmacologically important metabolites N-desmethyltamoxifen (NDM-TAM), 4-hydroxytamoxifen (4-OH-TAM), and endoxifen was developed and validated. This model is able to simulate the pharmacokinetics (PK) after single and repeated oral tamoxifen doses in female breast cancer patients in dependence of the CYP2D6 phenotype. A detailed model-based analysis of the mass balance offered support for a recent hypothesis stating a more prominent role for endoxifen formation from 4-OH-TAM. In the future this model provides a good basis to further investigate the linkage of PK, mode of action, and treatment outcome in dependence of factors such as phenotype, ethnicity, or co-treatment with CYP2D6 inhibitors. PMID:22661948
Institute of Scientific and Technical Information of China (English)
Zheng-Xu Zhao; Kai-Ling Li
2006-01-01
This article first generalizes the basic engineering phases of modern rapid prototyping processes, and then describes the techniques of data capture for data modeling and model making. The article also provides a brief overview of the photogrametric techniques of restitution of 3D objects, and highlights the difficulties and limitations of existing methods.It therefore presents a novel approach to photo-modeling for acquiring 3D model data from single 2D photorealistic images.Implementation of the approach is then described against a background of rapid prototyping processes to demonstrate the effectiveness of photo-modeling practice.
Quantum coherence and uncertainty in the anisotropic XY chain
2014-01-01
We explore the local quantum coherence and the local quantum uncertainty, based on Wigner-Yanase skew information, in the ground state of the anisotropic spin-1/2 XY chain in transverse magnetic field. We show that the skew information, as a figure of merit, supplies the necessary information to reveal the occurrence of the second order phase transition and the completely factorized ground state in the XY model. Additionally, in the same context, we also discuss the usefulness of a simple exp...
A Coupled 2 × 2D Babcock–Leighton Solar Dynamo Model. II. Reference Dynamo Solutions
Lemerle, Alexandre; Charbonneau, Paul
2017-01-01
In this paper we complete the presentation of a new hybrid 2 × 2D flux transport dynamo (FTD) model of the solar cycle based on the Babcock–Leighton mechanism of poloidal magnetic field regeneration via the surface decay of bipolar magnetic regions (BMRs). This hybrid model is constructed by allowing the surface flux transport (SFT) simulation described in Lemerle et al. to provide the poloidal source term to an axisymmetric FTD simulation defined in a meridional plane, which in turn generates the BMRs required by the SFT. A key aspect of this coupling is the definition of an emergence function describing the probability of BMR emergence as a function of the spatial distribution of the internal axisymmetric magnetic field. We use a genetic algorithm to calibrate this function, together with other model parameters, against observed cycle 21 emergence data. We present a reference dynamo solution reproducing many solar cycle characteristics, including good hemispheric coupling, phase relationship between the surface dipole and the BMR-generating internal field, and correlation between dipole strength at cycle maximum and peak amplitude of the next cycle. The saturation of the cycle amplitude takes place through the quenching of the BMR tilt as a function of the internal field. The observed statistical scatter about the mean BMR tilt, built into the model, acts as a source of stochasticity which dominates amplitude fluctuations. The model thus can produce Dalton-like epochs of strongly suppressed cycle amplitude lasting a few cycles and can even shut off entirely following an unfavorable sequence of emergence events.
Meqbel, Naser; Weckmann, Ute; Muñoz, Gerard; Ritter, Oliver
2016-12-01
We report on a study to explore the deep electrical conductivity structure of the Dead Sea Basin (DSB) using magnetotelluric (MT) data collected along a transect across the DSB where the left lateral strike-slip Dead Sea transform (DST) fault splits into two fault strands forming one of the largest pull-apart basins of the world. A very pronounced feature of our 2-D inversion model is a deep, subvertical conductive zone beneath the DSB. The conductor extends through the entire crust and is sandwiched between highly resistive structures associated with Precambrian rocks of the basin flanks. The high electrical conductivity could be attributed to fluids released by dehydration of the uppermost mantle beneath the DSB, possibly in combination with fluids released by mid- to low-grade metamorphism in the lower crust and generation of hydrous minerals in the middle crust through retrograde metamorphism. Similar high conductivity zones associated with fluids have been reported from other large fault systems. The presence of fluids and hydrous minerals in the middle and lower crust could explain the required low friction coefficient of the DST along the eastern boundary of the DSB and the high subsidence rate of basin sediments. 3-D inversion models confirm the existence of a subvertical high conductivity structure underneath the DSB but its expression is far less pronounced. Instead, the 3-D inversion model suggests a deepening of the conductive DSB sediments off-profile towards the south, reaching a maximum depth of approximately 12 km, which is consistent with other geophysical observations. At shallower levels, the 3-D inversion model reveals salt diapirism as an upwelling of highly resistive structures, localized underneath the Al-Lisan Peninsula. The 3-D model furthermore contains an E-W elongated conductive structure to the northeast of the DSB. More MT data with better spatial coverage are required, however, to fully constrain the robustness of the above
Bignardi, S.; Mantovani, A.; Abu Zeid, N.
2016-08-01
OpenHVSR is a computer program developed in the Matlab environment, designed for the simultaneous modeling and inversion of large Horizontal-to-Vertical Spectral Ratio (HVSR or H/V) datasets in order to construct 2D/3D subsurface models (topography included). The program is designed to provide a high level of interactive experience to the user and still to be of intuitive use. It implements several effective and established tools already present in the code ModelHVSR by Herak (2008), and many novel features such as: -confidence evaluation on lateral heterogeneity -evaluation of frequency dependent single parameter impact on the misfit function -relaxation of Vp/Vs bounds to allow for water table inclusion -a new cost function formulation which include a slope dependent term for fast matching of peaks, which greatly enhances convergence in case of low quality HVSR curves inversion -capability for the user of editing the subsurface model at any time during the inversion and capability to test the changes before acceptance. In what follows, we shall present many features of the program and we shall show its capabilities on both simulated and real data. We aim to supply a powerful tool to the scientific and professional community capable of handling large sets of HSVR curves, to retrieve the most from their microtremor data within a reduced amount of time and allowing the experienced scientist the necessary flexibility to integrate into the model their own geological knowledge of the sites under investigation. This is especially desirable now that microtremor testing has become routinely used. After testing the code over different datasets, both simulated and real, we finally decided to make it available in an open source format. The program is available by contacting the authors.
Meqbel, Naser; Weckmann, Ute; Muñoz, Gerard; Ritter, Oliver
2016-09-01
We report on a study to explore the deep electrical conductivity structure of the Dead Sea Basin (DSB) using magnetotelluric (MT) data collected along a transect across the DSB where the left lateral strike slip Dead Sea transform fault (DST) splits into two fault strands forming one of the largest pull-apart basins of the world. A very pronounced feature of our 2D inversion model is a deep, sub-vertical conductive zone beneath the DSB. The conductor extends through the entire crust and is sandwiched between highly resistive structures associated with Precambrian rocks of the basin flanks. The high electrical conductivity could be attributed to fluids released by dehydration of the uppermost mantle beneath the DSB, possibly in combination with fluids released by mid to low grade metamorphism in the lower crust and generation of hydrous minerals in the middle crust through retrograde metamorphism. Similar high conductivity zones associated with fluids have been reported from other large fault systems. The presence of fluids and hydrous minerals in the middle and lower crust could explain the required low friction coefficient of the DST along the eastern boundary of the Dead Sea basin and the high subsidence rate of basin sediments. 3D inversion models confirm the existence of a sub-vertical high conductivity structure underneath the DSB but its expression is far less pronounced. Instead, the 3D inversion model suggests a deepening of the conductive DSB sediments off-profile towards the south, reaching a maximum depth of approximately 12 km, which is consistent with other geophysical observations. At shallower levels, the 3D inversion model reveals salt diapirism as an upwelling of highly resistive structures, localized underneath the Al-Lisan Peninsula. The 3D model furthermore contains an E-W elongated conductive structure to the north-east of the Dead Sea basin. More MT data with better spatial coverage are required, however, to fully constrain the robustness of
Deb, SK; Shukla, MK; J. Šimůnek; Mexal, JG
2013-01-01
Quantitative information about the spatial and temporal patterns of compensatory root water uptake (RWU) in flood-irrigated pecan orchard is limited. We evaluated spatio-temporal compensated and uncompensated RWU patterns of mature pecan tree in a silty clay loam orchard using the HYDRUS (2D/3D) model. HYDRUS (2D/3D) simulations, which agreed well with measured water contents and temperatures at different soil depths and horizontal distances from the tree trunk, suggested that while both comp...
Bais, Preeti; Beebe, Kirk; Morelli, Kathryn H; Currie, Meagan E; Norberg, Sara N; Evsikov, Alexei V; Miers, Kathy E; Seburn, Kevin L; Guergueltcheva, Velina; Kremensky, Ivo; Jordanova, Albena; Bult, Carol J; Burgess, Robert W
2016-01-01
Charcot-Marie-Tooth disease encompasses a genetically heterogeneous class of heritable polyneuropathies that result in axonal degeneration in the peripheral nervous system. Charcot-Marie-Tooth type 2D neuropathy (CMT2D) is caused by dominant mutations in glycyl tRNA synthetase (GARS). Mutations in the mouse Gars gene result in a genetically and phenotypically valid animal model of CMT2D. How mutations in GARS lead to peripheral neuropathy remains controversial. To identify putative disease mechanisms, we compared metabolites isolated from the spinal cord of Gars mutant mice and their littermate controls. A profile of altered metabolites that distinguish the affected and unaffected tissue was determined. Ascorbic acid was decreased fourfold in the spinal cord of CMT2D mice, but was not altered in serum. Carnitine and its derivatives were also significantly reduced in spinal cord tissue of mutant mice, whereas glycine was elevated. Dietary supplementation with acetyl-L-carnitine improved gross motor performance of CMT2D mice, but neither acetyl-L-carnitine nor glycine supplementation altered the parameters directly assessing neuropathy. Other metabolite changes suggestive of liver and kidney dysfunction in the CMT2D mice were validated using clinical blood chemistry. These effects were not secondary to the neuromuscular phenotype, as determined by comparison with another, genetically unrelated mouse strain with similar neuromuscular dysfunction. However, these changes do not seem to be causative or consistent metabolites of CMT2D, because they were not observed in a second mouse Gars allele or in serum samples from CMT2D patients. Therefore, the metabolite 'fingerprint' we have identified for CMT2D improves our understanding of cellular biochemical changes associated with GARS mutations, but identification of efficacious treatment strategies and elucidation of the disease mechanism will require additional studies.
Bais, Preeti; Beebe, Kirk; Morelli, Kathryn H.; Currie, Meagan E.; Norberg, Sara N.; Evsikov, Alexei V.; Miers, Kathy E.; Seburn, Kevin L.; Guergueltcheva, Velina; Kremensky, Ivo; Jordanova, Albena; Bult, Carol J.
2016-01-01
ABSTRACT Charcot–Marie–Tooth disease encompasses a genetically heterogeneous class of heritable polyneuropathies that result in axonal degeneration in the peripheral nervous system. Charcot–Marie–Tooth type 2D neuropathy (CMT2D) is caused by dominant mutations in glycyl tRNA synthetase (GARS). Mutations in the mouse Gars gene result in a genetically and phenotypically valid animal model of CMT2D. How mutations in GARS lead to peripheral neuropathy remains controversial. To identify putative disease mechanisms, we compared metabolites isolated from the spinal cord of Gars mutant mice and their littermate controls. A profile of altered metabolites that distinguish the affected and unaffected tissue was determined. Ascorbic acid was decreased fourfold in the spinal cord of CMT2D mice, but was not altered in serum. Carnitine and its derivatives were also significantly reduced in spinal cord tissue of mutant mice, whereas glycine was elevated. Dietary supplementation with acetyl-L-carnitine improved gross motor performance of CMT2D mice, but neither acetyl-L-carnitine nor glycine supplementation altered the parameters directly assessing neuropathy. Other metabolite changes suggestive of liver and kidney dysfunction in the CMT2D mice were validated using clinical blood chemistry. These effects were not secondary to the neuromuscular phenotype, as determined by comparison with another, genetically unrelated mouse strain with similar neuromuscular dysfunction. However, these changes do not seem to be causative or consistent metabolites of CMT2D, because they were not observed in a second mouse Gars allele or in serum samples from CMT2D patients. Therefore, the metabolite ‘fingerprint’ we have identified for CMT2D improves our understanding of cellular biochemical changes associated with GARS mutations, but identification of efficacious treatment strategies and elucidation of the disease mechanism will require additional studies. PMID:27288508
Directory of Open Access Journals (Sweden)
Preeti Bais
2016-07-01
Full Text Available Charcot–Marie–Tooth disease encompasses a genetically heterogeneous class of heritable polyneuropathies that result in axonal degeneration in the peripheral nervous system. Charcot–Marie–Tooth type 2D neuropathy (CMT2D is caused by dominant mutations in glycyl tRNA synthetase (GARS. Mutations in the mouse Gars gene result in a genetically and phenotypically valid animal model of CMT2D. How mutations in GARS lead to peripheral neuropathy remains controversial. To identify putative disease mechanisms, we compared metabolites isolated from the spinal cord of Gars mutant mice and their littermate controls. A profile of altered metabolites that distinguish the affected and unaffected tissue was determined. Ascorbic acid was decreased fourfold in the spinal cord of CMT2D mice, but was not altered in serum. Carnitine and its derivatives were also significantly reduced in spinal cord tissue of mutant mice, whereas glycine was elevated. Dietary supplementation with acetyl-L-carnitine improved gross motor performance of CMT2D mice, but neither acetyl-L-carnitine nor glycine supplementation altered the parameters directly assessing neuropathy. Other metabolite changes suggestive of liver and kidney dysfunction in the CMT2D mice were validated using clinical blood chemistry. These effects were not secondary to the neuromuscular phenotype, as determined by comparison with another, genetically unrelated mouse strain with similar neuromuscular dysfunction. However, these changes do not seem to be causative or consistent metabolites of CMT2D, because they were not observed in a second mouse Gars allele or in serum samples from CMT2D patients. Therefore, the metabolite ‘fingerprint’ we have identified for CMT2D improves our understanding of cellular biochemical changes associated with GARS mutations, but identification of efficacious treatment strategies and elucidation of the disease mechanism will require additional studies.
Cepeda, Jose; Luna, Byron Quan; Nadim, Farrokh
2013-04-01
An essential component of a quantitative landslide hazard assessment is establishing the extent of the endangered area. This task requires accurate prediction of the run-out behaviour of a landslide, which includes the estimation of the run-out distance, run-out width, velocities, pressures, and depth of the moving mass and the final configuration of the deposits. One approach to run-out modelling is to reproduce accurately the dynamics of the propagation processes. A number of dynamic numerical models are able to compute the movement of the flow over irregular topographic terrains (3-D) controlled by a complex interaction between mechanical properties that may vary in space and time. Given the number of unknown parameters and the fact that most of the rheological parameters cannot be measured in the laboratory or field, the parametrization of run-out models is very difficult in practice. For this reason, the application of run-out models is mostly used for back-analysis of past events and very few studies have attempted to achieve forward predictions. Consequently all models are based on simplified descriptions that attempt to reproduce the general features of the failed mass motion through the use of parameters (mostly controlling shear stresses at the base of the moving mass) which account for aspects not explicitly described or oversimplified. The uncertainties involved in the run-out process have to be approached in a stochastic manner. It is of significant importance to develop methods for quantifying and properly handling the uncertainties in dynamic run-out models, in order to allow a more comprehensive approach to quantitative risk assessment. A method was developed to compute the variation in run-out intensities by using a dynamic run-out model (MassMov2D) and a probabilistic framework based on a Monte Carlo simulation in order to analyze the effect of the uncertainty of input parameters. The probability density functions of the rheological parameters
Elsawy, Hesham
2014-11-01
Device-to-device (D2D) communication enables the user equipments (UEs) located in close proximity to bypass the cellular base stations (BSs) and directly connect to each other, and thereby, offload traffic from the cellular infrastructure. D2D communication can improve spatial frequency reuse and energy efficiency in cellular networks. This paper presents a comprehensive and tractable analytical framework for D2D-enabled uplink cellular networks with a flexible mode selection scheme along with truncated channel inversion power control. The developed framework is used to analyze and understand how the underlaying D2D communication affects the cellular network performance. Through comprehensive numerical analysis, we investigate the expected performance gains and provide guidelines for selecting the network parameters.
System-parameter dependence of the metallic phase of the non-doped 2D Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Yamaji, K., E-mail: yamaji-kuni@aist.go.j [Nanoelectronics Research Institute, AIST Central 2, 1-1-1 Umezono, Tsukuba 305-8568 (Japan); Yanagisawa, T. [Nanoelectronics Research Institute, AIST Central 2, 1-1-1 Umezono, Tsukuba 305-8568 (Japan); Miyazaki, M. [Hakodate National College of Technology, 14-1 Tokura-cho, Hakodate 042-8501 (Japan); Kadono, R. [Institute of Materials Structure Science, KEK, 1-1 Oho, Tsukuba 305-0801 (Japan)
2009-10-15
Naito et al. reported that some non-doped T'-214-type compounds drive high-T{sub c} superconductivity. The compounds are considered to be metallic since on-site Coulomb energy U is moderate and the Fermi surface is much deformed in these compounds. In order to confirm this picture and extract electronic structure information, we have examined the phase diagram of the metallic state of the 2D Hubbard model as a function of U and t' (with t'' we fixed at -t'/2 here; t' and t'' are the second- and third-neighbor transfer energies, respectively) by means of the variational Monte-Carlo method. We employed a Jastrow-type Gutzwiller trial wave function. In the studied range of U 2-12, the boundary value for |t'| at which SDW disappears increases almost linearly with U. Jump-wise transition to the Mott insulator state was not observed. Using the boundary curve and experimental band parameter values, we estimate U approx 5 for T'-214 compounds. Preceding works are discussed in the last part.
Energy Technology Data Exchange (ETDEWEB)
Plenio, M. B.; Almeida, J.; Huelga, S. F. [Institute for Theoretical Physics, Albert-Einstein-Allee 11, University Ulm, D-89069 Ulm (Germany)
2013-12-21
We demonstrate that the coupling of excitonic and vibrational motion in biological complexes can provide mechanisms to explain the long-lived oscillations that have been obtained in nonlinear spectroscopic signals of different photosynthetic pigment protein complexes and we discuss the contributions of excitonic versus purely vibrational components to these oscillatory features. Considering a dimer model coupled to a structured spectral density we exemplify the fundamental aspects of the electron-phonon dynamics, and by analyzing separately the different contributions to the nonlinear signal, we show that for realistic parameter regimes purely electronic coherence is of the same order as purely vibrational coherence in the electronic ground state. Moreover, we demonstrate how the latter relies upon the excitonic interaction to manifest. These results link recently proposed microscopic, non-equilibrium mechanisms to support long lived coherence at ambient temperatures with actual experimental observations of oscillatory behaviour using 2D photon echo techniques to corroborate the fundamental importance of the interplay of electronic and vibrational degrees of freedom in the dynamics of light harvesting aggregates.
Plenio, M B; Almeida, J; Huelga, S F
2013-12-21
We demonstrate that the coupling of excitonic and vibrational motion in biological complexes can provide mechanisms to explain the long-lived oscillations that have been obtained in nonlinear spectroscopic signals of different photosynthetic pigment protein complexes and we discuss the contributions of excitonic versus purely vibrational components to these oscillatory features. Considering a dimer model coupled to a structured spectral density we exemplify the fundamental aspects of the electron-phonon dynamics, and by analyzing separately the different contributions to the nonlinear signal, we show that for realistic parameter regimes purely electronic coherence is of the same order as purely vibrational coherence in the electronic ground state. Moreover, we demonstrate how the latter relies upon the excitonic interaction to manifest. These results link recently proposed microscopic, non-equilibrium mechanisms to support long lived coherence at ambient temperatures with actual experimental observations of oscillatory behaviour using 2D photon echo techniques to corroborate the fundamental importance of the interplay of electronic and vibrational degrees of freedom in the dynamics of light harvesting aggregates.
Thermodynamic properties of the 2D frustrated Heisenberg model for the entire J1 -J2 circle
Mikheyenkov, A. V.; Shvartsberg, A. V.; Valiulin, V. E.; Barabanov, A. F.
2016-12-01
Using the spherically symmetric self-consistent Green's function method, we consider thermodynamic properties of the S = 1 / 2J1 -J2 Heisenberg model on the 2D square lattice. We calculate the temperature dependence of the spin-spin correlation functions cr = , the gaps in the spin excitation spectrum, the energy E and the heat capacity CV for the whole J1-J2-circle, i.e. for arbitrary φ, J1 = cos (φ), J2 = sin (φ). Due to low dimension there is no long-range order at T ≠ 0, but the short-range holds the memory of the parent zero-temperature ordered phase (antiferromagnetic, stripe or ferromagnetic). E(φ) and CV(φ) demonstrate extrema "above" the long-range ordered phases and in the regions of rapid short-range rearranging. Tracts of cr(φ) lines have several nodes leading to nonmonotonic cr(T) dependence. For any fixed φ the heat capacity CV(T) always has maximum, tending to zero at T → 0, in the narrow vicinity of φ = 155 ° it exhibits an additional frustration-induced low-temperature maximum. We have also found the nonmonotonic behaviour of the spin gaps at φ = 270 ° ± 0 and exponentially small antiferromagnetic gap up to (T ≲ 0.5) for φ ≳ 270 °.
3D RECORDING FOR 2D DELIVERING – THE EMPLOYMENT OF 3D MODELS FOR STUDIES AND ANALYSES –
Directory of Open Access Journals (Sweden)
A. Rizzi
2012-09-01
Full Text Available In the last years, thanks to the advances of surveying sensors and techniques, many heritage sites could be accurately replicated in digital form with very detailed and impressive results. The actual limits are mainly related to hardware capabilities, computation time and low performance of personal computer. Often, the produced models are not visible on a normal computer and the only solution to easily visualized them is offline using rendered videos. This kind of 3D representations is useful for digital conservation, divulgation purposes or virtual tourism where people can visit places otherwise closed for preservation or security reasons. But many more potentialities and possible applications are available using a 3D model. The problem is the ability to handle 3D data as without adequate knowledge this information is reduced to standard 2D data. This article presents some surveying and 3D modeling experiences within the APSAT project ("Ambiente e Paesaggi dei Siti d’Altura Trentini", i.e. Environment and Landscapes of Upland Sites in Trentino. APSAT is a multidisciplinary project funded by the Autonomous Province of Trento (Italy with the aim documenting, surveying, studying, analysing and preserving mountainous and hill-top heritage sites located in the region. The project focuses on theoretical, methodological and technological aspects of the archaeological investigation of mountain landscape, considered as the product of sequences of settlements, parcelling-outs, communication networks, resources, and symbolic places. The mountain environment preserves better than others the traces of hunting and gathering, breeding, agricultural, metallurgical, symbolic activities characterised by different lengths and environmental impacts, from Prehistory to the Modern Period. Therefore the correct surveying and documentation of this heritage sites and material is very important. Within the project, the 3DOM unit of FBK is delivering all the surveying
Directory of Open Access Journals (Sweden)
Kristin eDickschen
2012-05-01
Full Text Available Tamoxifen is a first-line endocrine agent in the mechanism-based treatment of estrogen receptor positive (ER+ mammary carcinoma and applied to breast cancer patients all over the world. Endoxifen is a secondary and highly active metabolite of tamoxifen that is formed among others by the polymorphic cytochrome P450 2D6 (CYP2D6. It is widely accepted that CYP2D6 poor metabolizers (PM exert a pronounced decrease in endoxifen steady-state plasma concentrations compared to CYP2D6 extensive metabolizers (EM. Nevertheless, an in-depth understanding of the chain of cause and effect between CYP2D6 genotype, endoxifen steady-state plasma concentration, and subsequent tamoxifen treatment benefit still remains to be evolved.In this context, physiologically-based pharmacokinetic (PBPK-modeling provides a useful tool to mechanistically investigate the impact of CYP2D6 phenotype on endoxifen formation in female breast cancer patients undergoing tamoxifen therapy.It has long been thought that only a minor percentage of endoxifen is formed via 4-hydroxytamoxifen. However, the current investigation supports very recently published data that postulates a contribution of 4-hydroxytamoxifen above 20 % to total endoxifen formation. The developed PBPK-model describes tamoxifen PK in rats and humans. Moreover, tamoxifen metabolism in dependence of CYP2D6 phenotype in populations of European female individuals is well described, thus providing a good basis to further investigate the linkage of PK, mode of action, and treatment outcome in dependence of factors such as phenotype, ethnicity or co-treatment with CYP2D6 inhibitors.
Institute of Scientific and Technical Information of China (English)
HAN Dong; FANG Hong-wei; BAI Jing; HE Guo-jian
2011-01-01
A coupled one-dimensional(1-D)and two-dimensional(2-D)channel network mathematical model is proposed for flow calculations at nodes in a channel network system in this article.For the 1-D model,the finite difference method is used to discretize the Saint-Venant equations in all channels of a looped network.The Alternating Direction Implicit(ADI)method is adopted for the 2-D model at the nodes.In the coupled model,the 1-D model provides a good approximation with small computational effort,while the 2-D model is applied for complex topography to achieve a high accuracy.An Artificial Neural Network(ANN)method is used for the data exchange and the connectivity between the 1-D and 2-D models.The coupled model is applied to the Jingjiang-Dongting Lake region,to simulate the tremendous looped channel network system,and the results are compared with field data.The good agreement shows that the coupled hydraulic model is more effective than the conventional 1-D model.
Chevalier, Laure; Collombet, Marielle; Pinel, Virginie
2017-03-01
Understanding magma degassing evolution during an eruption is essential to improving forecasting of effusive/explosive regime transitions at andesitic volcanoes. Lava domes frequently form during effusive phases, inducing a pressure increase both within the conduit and within the surrounding rocks. To quantify the influence of dome height on magma flow and degassing, we couple magma and gas flow in a 2D numerical model. The deformation induced by magma flow evolution is also quantified. From realistic initial magma flow conditions in effusive regime (Collombet, 2009), we apply increasing pressure at the conduit top as the dome grows. Since volatile solubility increases with pressure, dome growth is then associated with an increase in magma dissolved water content at a given depth, which corresponds with a decrease in magma porosity and permeability. Magma flow evolution is associated with ground deflation of a few μrad in the near field. However this signal is not detectable as it is hidden by dome subsidence (a few mrad). A Darcy flow model is used to study the impact of pressure and permeability conditions on gas flow in the conduit and surrounding rock. We show that dome permeability has almost no influence on magma degassing. However, increasing pressure in the surrounding rock, due to dome loading, as well as decreasing magma permeability in the conduit limit permeable gas loss at the conduit walls, thus causing gas pressurization in the upper conduit by a few tens of MPa. Decreasing magma permeability and increasing gas pressure increase the likelihood of magma explosivity and hazard in the case of a rapid decompression due to dome collapse.
Lu, Xianqing; Zhang, Jicai
2006-10-01
Based on the simulation of M2 tide in the Bohai Sea, the Yellow Sea and the East China Sea, TOPEX/Poseidon altimeter data are assimilated into a 2D tidal model to study the spatially varying bottom friction coefficient (BFC) by using the adjoint method. In this study, the BFC at some grid points are selected as the independent BFC, while the BFC at other grid points can be obtained through linear interpolation with the independent BFC. Two strategies for selecting the independent BFC are discussed. In the first strategy, one independent BFC is uniformly selected from each 1°×1° area. In the second one, the independent BFC are selected based on the spatial distribution of water depth. Twin and practical experiments are carried out to compare the two strategies. In the twin experiments, the adjoint method has a strong ability of inverting the prescribed BFC distributions combined with the spatially varying BFC. In the practical experiments, reasonable simulation results can be obtained by optimizing the spatially varying independent BFC. In both twin and practical experiments, the simulation results with the second strategy are better than those with the first one. The BFC distribution obtained from the practical experiment indicates that the BFC in shallow water are larger than those in deep water in the Bohai Sea, the North Yellow Sea, the South Yellow Sea and the East China Sea individually. However, the BFC in the East China Sea are larger than those in the other areas perhaps because of the large difference of water depth or bottom roughness. The sensitivity analysis indicates that the model results are more sensitive to the independent BFC near the land.
Ex vivo 2D and 3D HSV-2 infection model using human normal vaginal epithelial cells.
Zhu, Yaqi; Yang, Yan; Guo, Juanjuan; Dai, Ying; Ye, Lina; Qiu, Jianbin; Zeng, Zhihong; Wu, Xiaoting; Xing, Yanmei; Long, Xiang; Wu, Xufeng; Ye, Lin; Wang, Shubin; Li, Hui
2017-01-27
Herpes simplex virus type 2 (HSV-2) infects human genital mucosa and establishes life-long latent infection. It is unmet need to establish a human cell-based microphysiological system for virus biology and anti-viral drug discovery. One of barriers is lacking of culture system of normal epithelial cells in vitro over decades. In this study, we established human normal vaginal epithelial cell (HNVEC) culture using co-culture system. HNVEC cells were then propagated rapidly and stably in a defined culture condition. HNVEC cells exhibited a normal diploid karyotype and formed the well-defined and polarized spheres in matrigel three-dimension (3D) culture, while malignant cells (HeLa) formed disorganized and nonpolar solid spheres. HNVEC cells had a normal cellular response to DNA damage and had no transforming property using soft agar assays. HNVEC expressed epithelial marker cytokeratin 14 (CK14) and p63, but not cytokeratin 18 (CK18). Next, we reconstructed HNVEC-derived 3D vaginal epithelium using air-liquid interface (ALI) culture. This 3D vaginal epithelium has the basal and apical layers with expression of epithelial markers as its originated human vaginal tissue. Finally, we established an HSV-2 infection model based on the reconstructed 3D vaginal epithelium. After inoculation of HSV-2 (G strain) at apical layer of the reconstructed 3D vaginal epithelium, we observed obvious pathological effects gradually spreading from the apical layer to basal layer with expression of a viral protein. Thus, we established an ex vivo 2D and 3D HSV-2 infection model that can be used for HSV-2 virology and anti-viral drug discovery.
Energy Technology Data Exchange (ETDEWEB)
Begis, J.; Balzer, G.
1997-02-01
The numerical modelling of internal CFB boilers flows faced with complex phenomenons due to the flows un-stationariness, the heterogeneousness of the particle size distribution, and interactions between the two phases and the walls. Our study consisted in applying numerical models to the experimental configuration of cold circulating fluidized bed studied at the Cerchar. Special attention was given to the analysis of particles - wall interactions models, stemming from Jenkins (1992) and Louge`s (1994) theories, as well as the influence of the particles on fluid turbulence. In order to realize numerical simulations, we have used Eulerian two-phases flow codes developed at NHL medolif(2D), ESTET-ASTRID(3D). From different tests we have deducted that the most appropriate model for the realization of CFB`s prediction is the model taking in account the influence of particles on fluid turbulence. Then, to evaluate the validity limits of this model, we have built the regime diagram, and we have compared it with the experimental diagram. We have concluded that the simulation allows to describe the different CFB`s working regimes, and especially transitions. We have also noticed the importance of the choice of the mean diameter of the simulated particles. In this way, making a correction of the simulated particles` diameter in comparison with Sauter mean particle diameter, we obtained numerical results in good agreement with experimental data. (authors) 13 refs.
Ikeda, Tatsushi; Tanimura, Yoshitaka
2015-01-01
We explore and describe the roles of inter-molecular vibrations in terms of a Brownian oscillator (BO) model with linear-linear (LL) and square-linear (SL) system-bath interactions, which we use to analyze two-dimensional (2D) THz-Raman spectra obtained by means of molecular dynamics (MD) simulations. In addition to linear absorption (1D IR), we calculate 2D Raman-THz-THz, THz-Raman-THz, and THz-THz-Raman signals for liquid formamide, water, and methanol using an equilibrium non-equilibrium hybrid MD simulation. The calculated 1D IR and 2D THz-Raman signals are then accounted by the LL+SL BO model with the use of the hierarchal Fokker-Planck equations for a non-perturbative and non-Markovian noise. All of the characteristic 2D profiles of the simulated signals are reproduced using the LL+SL BO model, indicating that the present model captures the essential features of the inter-molecular motion. We analyze the fitted the 2D profiles in terms of anharmonicity, nonlinear polarizability, and dephasing time. The ...
El Kadi Abderrezzak, Kamal; Die Moran, Andrés; Tassi, Pablo; Ata, Riadh; Hervouet, Jean-Michel
2016-07-01
Bank erosion can be an important form of morphological adjustment in rivers. With the advances made in computational techniques, two-dimensional (2D) depth-averaged numerical models have become valuable tools for resolving many engineering problems dealing with sediment transport. The objective of this research work is to present a simple, new, bank-erosion operator that is integrated into a 2D Saint-Venant-Exner morphodynamic model. The numerical code is based on an unstructured grid of triangular elements and finite-element algorithms. The slope of each element in the grid is compared to the angle of repose of the bank material. Elements for which the slope is too steep are tilted to bring them to the angle of repose along a horizontal axis defined such that the volume loss above the axis is equal to the volume gain below, thus ensuring mass balance. The model performance is assessed using data from laboratory flume experiments and a scale model of the Old Rhine. For the flume experiment case with uniform bank material, relevant results are obtained for bank geometry changes. For the more challenging case (i.e. scale model of the Old Rhine with non-uniform bank material), the numerical model is capable of reproducing the main features of the bank failure, induced by the newly designed groynes, as well as the transport of the mobilized sediment material downstream. Some deviations between the computed results and measured data are, however, observed. They are ascribed to the effects of three-dimensional (3D) flow structures, pore pressure and cohesion, which are not considered in the present 2D model.
Steerneman, A.G.M.; van Perlo -ten Kleij, Frederieke
2005-01-01
The main topic of this paper is the matrix V = A - XY*, where A is a nonsingular complex k x k matrix and X and Y are k x p complex matrices of full column rank. Because properties of the matrix V can be derived from those of the matrix Q = I - XY*, we will consider in particular the case where A =
A 2-D process-based model for suspended sediment dynamics: A first step towards ecological modeling
Achete, F. M.; van der Wegen, M.; Roelvink, D.; Jaffe, B.
2015-01-01
In estuaries suspended sediment concentration (SSC) is one of the most important contributors to turbidity, which influences habitat conditions and ecological functions of the system. Sediment dynamics differs depending on sediment supply and hydrodynamic forcing conditions that vary over space and over time. A robust sediment transport model is a first step in developing a chain of models enabling simulations of contaminants, phytoplankton and habitat conditions. This works aims to determine turbidity levels in the complex-geometry delta of the San Francisco estuary using a process-based approach (Delft3D Flexible Mesh software). Our approach includes a detailed calibration against measured SSC levels, a sensitivity analysis on model parameters and the determination of a yearly sediment budget as well as an assessment of model results in terms of turbidity levels for a single year, water year (WY) 2011. Model results show that our process-based approach is a valuable tool in assessing sediment dynamics and their related ecological parameters over a range of spatial and temporal scales. The model may act as the base model for a chain of ecological models assessing the impact of climate change and management scenarios. Here we present a modeling approach that, with limited data, produces reliable predictions and can be useful for estuaries without a large amount of processes data.
A 2-D process-based model for suspended sediment dynamics: a first step towards ecological modeling
Directory of Open Access Journals (Sweden)
F. M. Achete
2015-02-01
Full Text Available In estuaries most of the sediment load is carried in suspension. Sediment dynamics differ depending on sediment supply and hydrodynamic forcing conditions that vary over space and over time. Suspended sediment concentration (SSC is one of the most important contributors to turbidity, which influences habitat conditions and ecological functions of the system. A robust sediment model is the first step towards a chain of model including contaminants and phytoplankton dynamics and habitat modeling. This works aims to determine turbidity levels in the complex-geometry Delta of San Francisco Estuary using a process-based approach (D-Flow Flexible Mesh software. Our approach includes a detailed calibration against measured SSC levels, a sensitivity analysis on model parameters, the determination of a yearly sediment budget as well as an assessment of model results in terms of turbidity levels for a single year (Water Year 2011. Model results shows that our process-based approach is a valuable tool in assessing sediment dynamics and their related ecological parameters over a range of spatial and temporal scales. The current model may act as the base model for a chain of ecological models and climate scenario forecasting.
Five radionuclide vadose zone models with different degrees of complexity (CHAIN, MULTIMED_DP, FECTUZ, HYDRUS, and CHAIN 2D) were selected for use in soil screening level (SSL) calculations. A benchmarking analysis between the models was conducted for a radionuclide (99Tc) rele...
Directory of Open Access Journals (Sweden)
Longbiao Li
2016-05-01
Full Text Available In this paper, the cyclic fatigue hysteresis loops of 2D woven SiC/SiC ceramic matrix composites (CMCs at elevated temperatures in steam have been investigated. The interface slip between fibers and the matrix existing in matrix cracking modes 3 and 5, in which matrix cracking and interface debonding occurred in longitudinal yarns, is considered as the major reason for hysteresis loops of 2D woven CMCs. The hysteresis loops of 2D SiC/SiC composites corresponding to different peak stresses, test conditions, and loading frequencies have been predicted using the present analysis. The damage parameter, i.e., the proportion of matrix cracking mode 3 in the entire matrix cracking modes of the composite, and the hysteresis dissipated energy increase with increasing fatigue peak stress. With increasing cycle number, the interface shear stress in the longitudinal yarns decreases, leading to transition of interface slip types of matrix cracking modes 3 and 5.
Zhang, Yi; Gabr, Refaat E.; Zhou, Jinyuan; Weiss, Robert G.; Bottomley, Paul A.
2013-12-01
Noninvasive magnetic resonance spectroscopy (MRS) with chemical shift imaging (CSI) provides valuable metabolic information for research and clinical studies, but is often limited by long scan times. Recently, spectroscopy with linear algebraic modeling (SLAM) was shown to provide compartment-averaged spectra resolved in one spatial dimension with many-fold reductions in scan-time. This was achieved using a small subset of the CSI phase-encoding steps from central image k-space that maximized the signal-to-noise ratio. Here, SLAM is extended to two- and three-dimensions (2D, 3D). In addition, SLAM is combined with sensitivity-encoded (SENSE) parallel imaging techniques, enabling the replacement of even more CSI phase-encoding steps to further accelerate scan-speed. A modified SLAM reconstruction algorithm is introduced that significantly reduces the effects of signal nonuniformity within compartments. Finally, main-field inhomogeneity corrections are provided, analogous to CSI. These methods are all tested on brain proton MRS data from a total of 24 patients with brain tumors, and in a human cardiac phosphorus 3D SLAM study at 3T. Acceleration factors of up to 120-fold versus CSI are demonstrated, including speed-up factors of 5-fold relative to already-accelerated SENSE CSI. Brain metabolites are quantified in SLAM and SENSE SLAM spectra and found to be indistinguishable from CSI measures from the same compartments. The modified reconstruction algorithm demonstrated immunity to maladjusted segmentation and errors from signal heterogeneity in brain data. In conclusion, SLAM demonstrates the potential to supplant CSI in studies requiring compartment-average spectra or large volume coverage, by dramatically reducing scan-time while providing essentially the same quantitative results.
Choquard, Ph.; Vuffray, M.
2014-10-01
The coupling between dilatation and vorticity, two coexisting and fundamental processes in fluid dynamics (Wu et al., 2006, pp. 3, 6) is investigated here, in the simplest cases of inviscid 2D isotropic Burgers and pressureless Euler-Coriolis fluids respectively modeled by single vortices confined in compressible, local, inertial and global, rotating, environments. The field equations are established, inductively, starting from the equations of the characteristics solved with an initial Helmholtz decomposition of the velocity fields namely a vorticity free and a divergence free part (Wu et al., 2006, Sects. 2.3.2, 2.3.3) and, deductively, by means of a canonical Hamiltonian Clebsch like formalism (Clebsch, 1857, 1859), implying two pairs of conjugate variables. Two vector valued fields are constants of the motion: the velocity field in the Burgers case and the momentum field per unit mass in the Euler-Coriolis one. Taking advantage of this property, a class of solutions for the mass densities of the fluids is given by the Jacobian of their sum with respect to the actual coordinates. Implementation of the isotropy hypothesis entails a radial dependence of the velocity potentials and of the stream functions associated to the compressible and to the rotational part of the fluids and results in the cancellation of the dilatation-rotational cross terms in the Jacobian. A simple expression is obtained for all the radially symmetric Jacobians occurring in the theory. Representative examples of regular and singular solutions are shown and the competition between dilatation and vorticity is illustrated. Inspired by thermodynamical, mean field theoretical analogies, a genuine variational formula is proposed which yields unique measure solutions for the radially symmetric fluid densities investigated. We stress that this variational formula, unlike the Hopf-Lax formula, enables us to treat systems which are both compressible and rotational. Moreover in the one
VCA Direct-Drive High Speed and Precision XY Table
Institute of Scientific and Technical Information of China (English)
ZHAO Xingyu; FENG Xiaomei; ZHANG Dawei
2007-01-01
In order to compensate for the limitation of conventional XY table used in semiconductor integrated circuits(IC) packaging and improve its speed and accuracy, a voice coil actuator (VCA)direct-drive high-speed and precision positioning XY table used in wire bonder was proposed. Also, a novel flexible decoupling mechanism was used in the positioning table, and the small moving mass enabled the positioning table to move at high speed and precision. XY table deformation interference caused by assembly error and instant interference generated by dynamic load moving with high speed and acceleration can be eliminated through the flexible decoupling mechanism. Considering the positioning table as lumped mass spring system, the dynamic equations of the mechanical sys-tem and the VCA were built according to the Newton mechanics principle and electromagnetic theory. Then the electromechanical coupling control model of the system was created through Laplace transform. Based on displacement PID controller, the Icop-locked controlling algorithm of the positioning system was investigated. The dynamic control algorithm effectively improved the system dynamic performance. The precision test of the prototype machine was carried out, and the results val-idated the correctness of the model and the theory. Compared with traditional XY table, the tablehas higher speed, acceleration and positioning accuracy.
A 2-D process-based model for suspended sediment dynamics: a first step towards ecological modeling
2015-01-01
In estuaries most of the sediment load is carried in suspension. Sediment dynamics differ depending on sediment supply and hydrodynamic forcing conditions that vary over space and over time. Suspended sediment concentration (SSC) is one of the most important contributors to turbidity, which influences habitat conditions and ecological functions of the system. A robust sediment model is the first step towards a chain of model including contaminants and phytoplankton dy...
A 2-D FEM thermal model to simulate water flow in a porous media: Campi Flegrei caldera case study
Directory of Open Access Journals (Sweden)
V. Romano
2012-05-01
Full Text Available Volcanic and geothermal aspects both exist in many geologically young areas. In these areas the heat transfer process is of fundamental importance, so that the thermal and fluid-dynamic processes characterizing a viscous fluid in a porous medium are very important to understand the complex dynamics of the these areas. The Campi Flegrei caldera, located west of the city of Naples, within the central-southern sector of the large graben of Campanian plain, is a region where both volcanic and geothermal phenomena are present. The upper part of the geothermal system can be considered roughly as a succession of volcanic porous material (tuff saturated by a mixture formed mainly by water and carbon dioxide. We have implemented a finite elements approach in transient conditions to simulate water flow in a 2-D porous medium to model the changes of temperature in the geothermal system due to magmatic fluid inflow, accounting for a transient phase, not considered in the analytical solutions and fluid compressibility. The thermal model is described by means of conductive/convective equations, in which we propose a thermal source represented by a parabolic shape function to better simulate an increase of temperature in the central part (magma chamber of a box, simulating the Campi Flegrei caldera and using more recent evaluations, from literature, for the medium's parameters (specific heat capacity, density, thermal conductivity, permeability. A best-fit velocity for the permeant is evaluated by comparing the simulated temperatures with those measured in wells drilled by Agip (Italian Oil Agency in the 1980s in the framework of geothermal exploration. A few tens of days are enough to reach the thermal steady state, showing the quick response of the system to heat injection. The increase in the pressure due to the heat transport is then used to compute ground deformation, in particular the vertical displacements characteristics of the Campi Flegrei caldera
DEFF Research Database (Denmark)
Pedersen, Henrik; Ólafsdóttir, Hildur; Darkner, Sune;
2009-01-01
with sufficient spatial and temporal resolution. To overcome this problem our method predicts pixel intensities in multiple 2D slices, acquired with high spatial and temporal resolution, and subsequently assembles these into volumetric data sets. The prediction is based on external motion sensors, in our case...
Kozinszky, Zoltan; Surányi, Andrea; Péics, Hajnalka; Molnár, András; Pál, Attila
2015-08-01
The aim of this study was to determine the utility of a new mathematical model in volumetric assessment of the placenta using 2-D ultrasound. Placental volumetry was performed in a prospective cross-sectional survey by virtual organ computer-aided analysis (VOCAL) with the help of a shell-off method in 346 uncomplicated pregnancies according to STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines. Furthermore, placental thickness, length and height were measured with the 2-D technique to estimate placental volume based on the mathematical formula for the volume of "the shell of the spherical sector." Fetal size was also assessed by 2-D sonography. The placental volumes measured by 2-D and 3-D techniques had a correlation of 0.86. In the first trimester, the correlation was 0.82, and later during pregnancy, it was 0.86. Placental volumetry using "the circle-shaped shell of the spherical sector" mathematical model with 2-D ultrasound technique may be introduced into everyday practice to screen for placental volume deviations associated with adverse pregnancy outcome.
基于概率模型的E-2D Mesh网络容错性分析%Fault Tolerance of E-2D Mesh Networks Based on Model of Probability
Institute of Scientific and Technical Information of China (English)
肖杰; 梁家荣; 黄亿海
2009-01-01
研究了太比特路由器核心交换网络拓扑的一种新结构-E-2D Mesh.提出一种计算E-2D Mesh网络连通率的新方法.证明了当网络结点失效率控制在0.66%以下时,具有四万多个结点的E-2D Mesh网络可保持不低于99%的连通率,且在同等规模条件下,E-2D Mesh网络结点容错率至少是Mesh网络的11.09倍.研究结果表明,该方法在计算E-2D Mesh网络连通率时显示出较强的生命力且能够用于研究其它层次的网络和其它网络通信问题.%A novel switching fabric is the core of the terabit router.--E-2D mesh networks are one of the most important network topologies In massively multiprocessor parallel systems. In this paper,a novel approach for calculating the probabilistic connectivity of E-2D mesh networks is proposed. The paper formally proves that when the networks'node failure probability is bounded by 0.66%, the E-2D mesh networks with over forty thousand nodes remain connected with probability larger than 99% , and in the same scale and conditions, the probability of E-2D mesh networks is 11.09 times greater than mesh networks. The results show that the method is a powerful technique for calculating the probabilistic connectivity in E-2D mesh networks,and the scheme is also applicable to the study of other hierarchical network structures and of other network communication problems.
Garrote, J.; Alvarenga, F. M.; Díez-Herrero, A.
2016-10-01
The village of Pajares de Pedraza (Segovia, Spain) is located in the floodplain of the Cega River, a left bank tributary of the Douro River. Repeated flash flood events occur in this small village because of its upstream catchment area, mountainous character and impermeable lithology, which reduce concentration time to just a few hours. River overbank flow has frequently caused flooding and property damage to homes and rural properties, most notably in 1927, 1991, 1996, 2001, 2013 and 2014. Consequently, a detailed analysis was carried out to quantify the economic risk of flash floods in peri-urban and rural areas. Magnitudes and exceedance probabilities were obtained from a flood frequency analysis of maximum discharges. To determine the extent and characteristics of the flooded area, we performed 2D hydraulic modeling (Iber 2.0 software) based on LIDAR (1 m) topography and considering three different scenarios associated with the initial construction (1997) and subsequent extension (2013) of a linear defense structure (rockfill dike or levee) to protect the population. Specific stage-damage functions were expressly developed using in situ data collection for exposed elements, with special emphasis on urban-type categories. The average number of elements and their unit value were established. The relationship between water depth and the height at which electric outlets, furniture, household goods, etc. were located was analyzed; due to its effect on the form of the function. Other nonspecific magnitude-damage functions were used in order to compare both economic estimates. The results indicate that the use of non-specific magnitude-damage functions leads to a significant overestimation of economic losses, partly linked to the use of general economic cost data. Furthermore, a detailed classification and financial assessment of exposed assets is the most important step to ensure a correct estimate of financial losses. In both cases, this should include a
Sikder, Arif Mohiuddin; Alam, M. Mustafa
2003-02-01
Structural architecture of the Bengal Basin has been strongly controlled by the collision pattern of the Indian plate with the Burma and Tibetan plates. The eastern fold belt (EFB) of the basin, comprising a series of north-south-trending curvilinear anticlines and synclines, represents a fold-and-thrust belt that constitutes the westward continuation of Arakan-Chin fold system of the Indo-Burman Ranges. The present study is mainly concerned with the 2-D modelling of the anticlinal structures in order to develop an understanding about the process-response relationships between the structural style and tectonic evolution of the eastern fold belt. The dominant fold-generating mechanism is believed to be the east-west-directed compressional force arising from oblique subduction of the Indian plate beneath the Burma plate that resulted in the growth of fault-propagation folds above a detachment or decollement at depth, giving rise to the Neogene accretionary prism complex development. A prominent feature of the region is the major east-dipping thrusts separating successive accretionary wedges. In seismic sections, evidence for several phases of compressional deformation suggests that multiphase stress conditions were responsible for the structural expression of the fold belt. Deep seismic sections reveal that the base of folding is characterized by a low-interval velocity horizon that represents a detachment separating the upper folded zone from the lower, seismically coherent, nearly unfolded zone. This detachment coincides with the undercompacted pressured shale unit, which is thought to have played an important role in the structural development of the eastern fold belt. Clay mineralogical analysis reveals the presence of a low-density shale horizon within the dense and thick shale sequence that is thought to be an undercompacted pressured shale during the geological past, and was responsible for the initiation of decollement and incipient diapirism involving thin
DEFF Research Database (Denmark)
Pardo, D.; Branner, K.
2005-01-01
A very detailed 2D-solid finite element model is developed representing the load carrying box girder of a wind turbine blade. Using typical geometrical values for the girder dimensions and public available material data, the overall cross-sectional behaviour is analysed for a simple compressive...
改进的牵引移动的蚁群算法在2D HP 模型中的应用%APPLYING IMPROVED PULL MOVES ACO IN 2D HP MODEL
Institute of Scientific and Technical Information of China (English)
高翔; 杨惠; 张成文
2015-01-01
Protein folding problem is to predict a protein’s conformation from its amino acid sequence,it is one of the most prominent problems in bioinformatics.In this paper we mainly study two-dimensional (2D)hydrophobic-polar (HP)lattice model,which is a representative simplified model widely used for simulating the protein folding problem,and apply the ant colony optimisation (ACO)to solving the 2D HP protein folding problem.Besides,we introduce an improved pull moves method to local search mechanism,to improve protein’s conformation it is an effective method.Experimental results show that the improved ACO with pull moves (ACO +)can obtain lower-energy conformations than ACO for several longer amino acid sequences,this demonstrates that our ACO + algorithm is a effective method to predict the structure of protein.%蛋白质折叠问题就是从氨基酸序列中预测蛋白质的构象，该问题是生物信息学的一个突出问题。主要研究二维 HP 格点模型，它是用于模拟蛋白质折叠问题的一个具有代表性的简化模型，并且将蚁群算法用于求解该二维 HP 蛋白质的折叠问题。此外，在局部搜索机制中引入一种改进的牵引移动方法，这是一个提高蛋白质构象的有效方法。实验结果表明，针对较长的氨基酸序列，改进的带牵引移动的蚁群算法（ACO ＋）比 ACO 能够获得更低能量的构象，证明了所提出的改进蚁群算法是预测蛋白质结构的有效方法。
Izrayelit, Yevgeniy; Robinette, Steven L; Bose, Neelanjan; von Reuss, Stephan H.; Schroeder, Frank C.
2012-01-01
Ascarosides are small-molecule signals that play a central role in C. elegans biology, including dauer formation, aging, and social behaviors, but many aspects of their biosynthesis remain unknown. Using automated 2D NMR-based comparative metabolomics, we identified ascaroside ethanolamides as shunt metabolites in C. elegans mutants of daf-22, a gene with homology to mammalian 3-ketoacyl-CoA thiolases predicted to function in conserved peroxisomal lipid β-oxidation. Two groups of ethanolamide...
Energy Technology Data Exchange (ETDEWEB)
Gepraegs, R.; Schmitz, G.; Peters, D. [Institut fuer Atmosphaerenphysik, Kuehlungsborn (Germany)
1997-12-31
A 2D version of the ECHAM T21 climate model has been developed. The new model includes an efficient spectral transport scheme with implicit diffusion. Furthermore, photodissociation and chemistry of the NCAR 2D model have been incorporated. A self consistent parametrization scheme is used for eddy heat- and momentum flux in the troposphere. It is based on the heat flux parametrization of Branscome and mixing-length formulation for quasi-geostrophic vorticity. Above 150 hPa the mixing-coefficient K{sub yy} is prescribed. Some of the model results are discussed, concerning especially the impact of aircraft NO{sub x} emission on the model chemistry. (author) 6 refs.
From 2D to 3D modelling in long term tectonics: Modelling challenges and HPC solutions (Invited)
Le Pourhiet, L.; May, D.
2013-12-01
Over the last decades, 3D thermo-mechanical codes have been made available to the long term tectonics community either as open source (Underworld, Gale) or more limited access (Fantom, Elvis3D, Douar, LaMem etc ...). However, to date, few published results using these methods have included the coupling between crustal and lithospheric dynamics at large strain. The fact that these computations are computational expensive is not the primary reason for the relatively slow development of 3D modeling in the long term tectonics community, as compare to the rapid development observed within the mantle dynamic community, or in the short-term tectonics field. Long term tectonics problems have specific issues not found in either of these two field, including; large strain (not an issue for short-term), the inclusion of free surface and the occurence of large viscosity contrasts. The first issue is typically eliminated using a combined marker-ALE method instead of fully lagrangian method, however, the marker-ALE approach can pose some algorithmic challenges in a massively parallel environment. The two last issues are more problematic because they affect the convergence of the linear/non-linear solver and the memory cost. Two options have been tested so far, using low order element and solving with a sparse direct solver, or using higher order stable elements together with a multi-grid solver. The first options, is simpler to code and to use but reaches its limit at around 80^3 low order elements. The second option requires more operations but allows using iterative solver on extremely large computers. In this presentation, I will describe the design philosophy and highlight results obtained using a code from the second-class method. The presentation will be oriented from an end-user point of view, using an application from 3D continental break up to illustrate key concepts. The description will proceed point by point from implementing physics into the code, to dealing with
From 2D to 3D - a new dimension for modelling the effect of natural products on human tissue
DEFF Research Database (Denmark)
Wrzesinski, Krzysztof; Fey, Stephen John
2015-01-01
Natural products, or their synthetic derivatives are a treasure trove to find potential candidates for novel drugs for human treatment. The selection of diamonds from the huge pile of worthless stone is a critical – and difficult - stage in the discovery pipeline. Of all the factors to be conside......Natural products, or their synthetic derivatives are a treasure trove to find potential candidates for novel drugs for human treatment. The selection of diamonds from the huge pile of worthless stone is a critical – and difficult - stage in the discovery pipeline. Of all the factors...... culture systems are reductionistic, they at least can be constructed from human cell types. In this review we will consider some of the evidence demonstrating that cells grown in 3D cultures have physiological performances that mimic functions seen in human tissues significantly better than cells grown...... using classical 2D culture systems. We will discuss advantages and disadvantages of these new culture technologies and highlight theoretical reasons for the differences. 3D cell culture technologies are more labour intensive than 2D culture systems and therefore their introduction is a trade-off between...
Leandro, Jorge; Martins, Ricardo
2016-01-01
Pluvial flooding in urban areas is characterized by a gradually varying inundation process caused by surcharge of the sewer manholes. Therefore urban flood models need to simulate the interaction between the sewer network and the overland flow in order to accurately predict the flood inundation extents. In this work we present a methodology for linking 2D overland flow models with the storm sewer model SWMM 5. SWMM 5 is a well-known free open-source code originally developed in 1971. The latest major release saw its structure re-written in C ++ allowing it to be compiled as a command line executable or through a series of calls made to function inside a dynamic link library (DLL). The methodology developed herein is written inside the same DLL in C + +, and is able to simulate the bi-directional interaction between both models during simulation. Validation is done in a real case study with an existing urban flood coupled model. The novelty herein is that the new methodology can be added to SWMM without the need for editing SWMM's original code. Furthermore, it is directly applicable to other coupled overland flow models aiming to use SWMM 5 as the sewer network model.
Directory of Open Access Journals (Sweden)
Filiberto Chiabrando
2011-12-01
Full Text Available The Basilica of San Pietro is a Romanic architecture located in the municipality of Tuscania in the Lazio Region about 100 km far from Rome. In 1971 the apse dome collapsed during the earthquake and the important fresco of a Christ Pantocrator was destroyed. In 1975 the dome was reconstructed using reinforced concrete.In 2010 an integrated survey of the Church has been performed using LiDAR techniques integrated with photogrammetric and topographic methodologies in order to realize a complete 2D documentation of the Basilica of San Pietro. Thanks to the acquired data a complete multi-scale 3D model of the Church and of the surroundings was realized.The aim of this work is to present different strategies in order to realize correct documentations for Cultural Heritage knowledge, using typical 3D survey methodologies (i. e. LiDAR survey and photogrammetry.After data acquisition and processing, several 2D representations were realized in order to carry out traditional supports for the different actors involved in the conservation plans; moreover, starting from the 2D drawing a simplified 3D modeling methodology has been followed in order to define the fundamental geometry of the Basilica and the surroundings: the achieved model could be useful for a small architectural scale description of the structure and for the documentation of the surroundings. For the aforementioned small architectural scale model, the 3D modeling was realized using the information derived from the 2D drawings with an approach based on the Constructive Solid Geometry. Using this approach the real shape of the object is simplified. This methodology is employed in particular when the shape of the structures is simple or to communicate new project ideas of when, as in our case, the aim is to give an idea of the complexity of an architectural Cultural Heritage. In order to follow this objective, a small architectural scale model was realized: the area of the Civita hill was
Calibration model of a dual gain flat panel detector for 2D and 3D x-ray imaging.
Schmidgunst, C; Ritter, D; Lang, E
2007-09-01
The continuing research and further development in flat panel detector technology have led to its integration into more and more medical x-ray systems for two-dimensional (2D) and three-dimensional (3D) imaging, such as fixed or mobile C arms. Besides the obvious advantages of flat panel detectors, like the slim design and the resulting optimum accessibility to the patient, their success is primarily a product of the image quality that can be achieved. The benefits in the physical and performance-related features as opposed to conventional image intensifier systems, (e.g., distortion-free reproduction of imaging information or almost linear signal response over a large dynamic range) can be fully exploited, however, only if the raw detector images are correctly calibrated and postprocessed. Previous procedures for processing raw data contain idealizations that, in the real world, lead to artifacts or losses in image quality. Thus, for example, temperature dependencies or changes in beam geometry, as can occur with mobile C arm systems, have not been taken into account up to this time. Additionally, adverse characteristics such as image lag or aging effects have to be compensated to attain the best possible image quality. In this article a procedure is presented that takes into account the important dependencies of the individual pixel sensitivity of flat panel detectors used in 2D or 3D imaging and simultaneously minimizes the work required for an extensive recalibration. It is suitable for conventional detectors with only one gain mode as well as for the detectors specially developed for 3D imaging with dual gain read-out technology.
Directory of Open Access Journals (Sweden)
Ke-Da Yu
Full Text Available PURPOSE: Previous studies have suggested that postmenopausal women with breast cancer who present with wild-type CYP2D6 may actually have similar or superior recurrence-free survival outcomes when given tamoxifen in place of aromatase inhibitors (AIs. The present study established a CYP2D6 multiple-genotype-based model to determine the optimal endocrine therapy for patients harboring wild-type CYP2D6. METHODS: We created a Markov model to determine whether tamoxifen or AIs maximized 5-year disease-free survival (DFS for extensive metabolizer (EM patients using annual hazard ratio (HR data from the BIG 1-98 trial. We then replicated the model by evaluating 9-year event-free survival (EFS using HR data from the ATAC trial. In addition, we employed two-way sensitivity analyses to explore the impact of HR of decreased-metabolizer (DM and its frequency on survival by studying a range of estimates. RESULTS: The 5-year DFS of tamoxifen-treated EM patients was 83.3%, which is similar to that of genotypically unselected patients who received an AI (83.7%. In the validation study, we further demonstrated that the 9-year EFS of tamoxifen-treated EM patients was 81.4%, which is higher than that of genotypically unselected patients receiving tamoxifen (78.4% and similar to that of patients receiving an AI (83.2%. Two-way sensitivity analyses demonstrated the robustness of the results. CONCLUSIONS: Our modeling analyses indicate that, among EM patients, the DFS/EFS outcome of patients receiving tamoxifen is similar to that of patients receiving an AI. Further prospective clinical trials are needed to evaluate the value of the CYP2D6 genotype in the selection of endocrine therapy.
Williams, R.; Stinton, A. J.; Sheridan, M. F.
2008-11-01
Titan2D is a depth-averaged, thin-layer computational fluid dynamics (CFD) code, suitable for simulating a variety of geophysical mass flows. Titan2D output data include flow thickness and flow momentum at each time step for all cells traversed by the flow during the simulation. From this information the flow limit, run-out path, flow velocity, deposit thickness, and travel time can be calculated. Results can be visualized in the open-source GRASS GIS software or with the built-in Titan2D viewer. A new two-phase Titan2D version allows simulation of flows containing various mixtures of water and solids. The purpose of this study is to compare simulations by the two-phase flow version of Titan2D with an actual event. The chosen natural flow is a small ash-rich lahar (volume 50,000 m 3-70,000 m 3) that occurred on 12 February 2005 in the Vazcún Valley, located on the north-east flank of Volcán Tungurahua, Ecuador. Lahars and pyroclastic flows along this valley could potentially threaten the 20,000 inhabitants living in and near the city of Baños. A variety of data sources exist for this lahar, including: post-event meter-scale topography, and photographic, video, seismic and acoustic flow monitoring (AFM) records from during the event. These data permit detailed comparisons between the dynamics of the actual lahar and those of the Titan2D simulated flow. In particular, detailed comparisons are made between run-up heights, flow velocity, inundation area, and flow thickness. Simulations utilize a variety of data derived from field observations such as lahar volume, solid to pore-fluid ratio and pre-event topography. Titan2D is important in modeling lahars because it allows assessment of the impact of the flows on buildings and infrastructure lifelines located near drainages that descend from volcanoes.
Quenched disorder and spin-glass correlations in XY nematics
Energy Technology Data Exchange (ETDEWEB)
Petridis, L; Terentjev, E M [Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE (United Kingdom)
2006-08-04
We present a theoretical study of the equilibrium ordering in a 3D XY nematic system with quenched random disorder. Within this model, treated with the replica trick and Gaussian variational method, the correlation length is obtained as a function of the local nematic order parameter Q and the effective disorder strength {gamma}. These results, {xi} {approx} Q{sup 2}e{sup 1/Q{sup 2}} and {xi} {approx} (1/{gamma}) e{sup -{gamma}}, clarify what happens in the limiting cases of diminishing Q and {gamma}, that is near a phase transition of a pure system. In particular, it is found that quenched disorder is irrelevant as Q {yields} 0 and hence does not change the character of the continuous XY nematic-isotropic phase transition. We discuss how these results compare with experiments and simulations.
Quantum coherence and uncertainty in the anisotropic XY chain
Karpat, G.; ćakmak, B.; Fanchini, F. F.
2014-09-01
We explore the local quantum coherence and the local quantum uncertainty, based on Wigner-Yanase skew information, in the ground state of the anisotropic spin-1/2 XY chain in a transverse magnetic field. We show that the skew information, as a figure of merit, supplies the necessary information to reveal the occurrence of the second-order phase transition and the completely factorized ground state in the XY model. Additionally, in the same context, we also discuss the usefulness of a simple experimentally friendly lower bound of local quantum coherence. Furthermore, we demonstrate how the connection between the appearance of nonanalyticities in the local quantum uncertainty of the ground state and the quantum phase transitions does not hold in general, by providing explicit examples of the situation. Lastly, we discuss the ability of the local quantum coherence to accurately estimate the critical point of the phase transition, and we investigate the robustness of the factorization phenomenon at low temperatures.
Directory of Open Access Journals (Sweden)
Anna Enrico
2014-08-01
Full Text Available Intermediate temperature-solid oxide fuel cell (IT-SOFC Ni-(ZrO2x(Y2O31−x (Ni-YSZ anodes formed by two layers, with different thicknesses and morphologies, offer the possibility of obtaining adequate electrochemical performance coupled to satisfactory mechanical properties. We investigate bi-layered Ni-YSZ anodes from a modeling point of view. The model includes reaction kinetics (Butler-Volmer equation, mass transport (Dusty-Gas model, and charge transport (Ohm’s law, and allows to gain an insight into the distribution of the electrochemical reaction within the electrode. Additionally, the model allows to evaluate a reciprocal overall electrode resistance 1/Rp ≈ 6 S·cm−2 for a bi-layer electrode formed by a 10 µm thick active layer (AL composed of 0.25 µm radius Ni and YSZ particles (34% vol. Ni, coupled to a 700 µm thick support layer (SL formed by 0.5 µm radius Ni and YSZ particles (50% vol. Ni, and operated at a temperature of 1023 K. Simulation results compare satisfactorily to literature experimental data. The model allows to investigate, in detail, the effect of morphological and geometric parameters on the various sources of losses, which is the first step for an optimized electrode design.
Ambrosini, Pierre; Smal, Ihor; Ruijters, Daniel; Niessen, Wiro; Moelker, Adriaan; van Walsum, Theo
2016-11-07
In minimal invasive image guided catheterization procedures, physicians require information of the catheter position with respect to the patient's vasculature. However, in fluoroscopic images, visualization of the vasculature requires toxic contrast agent. Static vasculature roadmapping, which can reduce the usage of iodine contrast, is hampered by the breathing motion in abdominal catheterization. In this paper, we propose a method to track the catheter tip inside the patient's 3D vessel tree using intra-operative single-plane 2D X-ray image sequences and a peri-operative 3D rotational angiography (3DRA). The method is based on a hidden Markov model (HMM) where states of the model are the possible positions of the catheter tip inside the 3D vessel tree. The transitions from state to state model the probabilities for the catheter tip to move from one position to another. The HMM is updated following the observation scores, based on the registration between the 2D catheter centerline extracted from the 2D X-ray image, and the 2D projection of 3D vessel tree centerline extracted from the 3DRA. The method is extensively evaluated on simulated and clinical datasets acquired during liver abdominal catheterization. The evaluations show a median 3D tip tracking error of 2.3 mm with optimal settings in simulated data. The registered vessels close to the tip have a median distance error of 4.7 mm with angiographic data and optimal settings. Such accuracy is sufficient to help the physicians with an up-to-date roadmapping. The method tracks in real-time the catheter tip and enables roadmapping during catheterization procedures.
Richardson, Robert R.; Zhao, Shi; Howey, David A.
2016-09-01
Estimating the temperature distribution within Li-ion batteries during operation is critical for safety and control purposes. Although existing control-oriented thermal models - such as thermal equivalent circuits (TEC) - are computationally efficient, they only predict average temperatures, and are unable to predict the spatially resolved temperature distribution throughout the cell. We present a low-order 2D thermal model of a cylindrical battery based on a Chebyshev spectral-Galerkin (SG) method, capable of predicting the full temperature distribution with a similar efficiency to a TEC. The model accounts for transient heat generation, anisotropic heat conduction, and non-homogeneous convection boundary conditions. The accuracy of the model is validated through comparison with finite element simulations, which show that the 2-D temperature field (r, z) of a large format (64 mm diameter) cell can be accurately modelled with as few as 4 states. Furthermore, the performance of the model for a range of Biot numbers is investigated via frequency analysis. For larger cells or highly transient thermal dynamics, the model order can be increased for improved accuracy. The incorporation of this model in a state estimation scheme with experimental validation against thermocouple measurements is presented in the companion contribution (http://www.sciencedirect.com/science/article/pii/S0378775316308163).
Bateman, A.; Medina, V.; Hürlimann, M.
2009-04-01
Debris flows are present in every country where a combination of high mountains and flash floods exists. In the northern part of the Iberian Peninsula, at the Pyrenees, sporadic debris events occur. We selected two different events. The first one was triggered at La Guingueta by the big exceptional flood event that produced many debris flows in 1982 which were spread all over the Catalonian Pyrenees. The second, more local event occurred in 2000 at the mountain Montserrat at the Pre-litoral mountain chain. We present here some results of the FLATModel, entirely developed at the Research Group in Sediment Transport of the Hydraulic, Marine and Environmental Engineering Department (GITS-UPC). The 2D FLATModel is a Finite Volume method that uses the Godunov scheme. Some numerical arranges have been made to analyze the entrainment process during the events, the Stop & Go phenomena and the final deposit of the material. The material rheology implemented is the Voellmy approach, because it acts very well evaluating the frictional and turbulent behavior. The FLATModel uses a GIS environment that facilitates the data analysis as the comparison between field and numerical data. The two events present two different characteristics, one is practically a one dimensional problem of 1400 m in length and the other has a more two dimensional behavior that forms a big fan.
Directory of Open Access Journals (Sweden)
Li Jun
2014-12-01
Full Text Available This paper reports an experimental investigation on the macroscopic mechanical behaviors and damage mechanisms of the plain-woven (2D C/SiC composite under in-plane on- and off-axis loading conditions. Specimens with 15°, 30°, and 45° off-axis angles were prepared and tested under monotonic and incremental cyclic tension and compression loads. The obtained results were compared with those of uniaxial tension, compression, and shear specimens. The relationships between the damage modes and the stress state were analyzed based on scanning electronic microscopy (SEM observations and acoustic emission (AE data. The test results reveal the remarkable axial anisotropy and unilateral behavior of the material. The off-axis tension test results show that the material is fiber-dominant and the evolution rate of damage and inelastic strain is accelerated under the corresponding combined biaxial tension and shear loads. Due to the damage impediment effect of compression stress, compression specimens show higher mechanical properties and lower damage evolution rates than tension specimens with the same off-axis angle. Under cyclic tension–compression loadings, both on-axis and off-axis specimens exhibit progressive damage deactivation behaviors in the compression range, but with different deactivation rates.
Izrayelit, Yevgeniy; Robinette, Steven L; Bose, Neelanjan; von Reuss, Stephan H; Schroeder, Frank C
2013-02-15
Ascarosides are small-molecule signals that play a central role in C. elegans biology, including dauer formation, aging, and social behaviors, but many aspects of their biosynthesis remain unknown. Using automated 2D NMR-based comparative metabolomics, we identified ascaroside ethanolamides as shunt metabolites in C. elegans mutants of daf-22, a gene with homology to mammalian 3-ketoacyl-CoA thiolases predicted to function in conserved peroxisomal lipid β-oxidation. Two groups of ethanolamides feature β-keto functionalization confirming the predicted role of daf-22 in ascaroside biosynthesis, whereas α-methyl substitution points to unexpected inclusion of methylmalonate at a late stage in the biosynthesis of long-chain fatty acids in C. elegans. We show that ascaroside ethanolamide formation in response to defects in daf-22 and other peroxisomal genes is associated with severe depletion of endocannabinoid pools. These results indicate unexpected interaction between peroxisomal lipid β-oxidation and the biosynthesis of endocannabinoids, which are major regulators of lifespan in C. elegans. Our study demonstrates the utility of unbiased comparative metabolomics for investigating biochemical networks in metazoans.
Zhang, Yanhua; Clennell, Michael B.; Delle Piane, Claudio; Ahmed, Shakil; Sarout, Joel
2016-12-01
This generic 2D elastic-plastic modelling investigated the reactivation of a small isolated and critically-stressed fault in carbonate rocks at a reservoir depth level for fluid depletion and normal-faulting stress conditions. The model properties and boundary conditions are based on field and laboratory experimental data from a carbonate reservoir. The results show that a pore pressure perturbation of -25 MPa by depletion can lead to the reactivation of the fault and parts of the surrounding damage zones, producing normal-faulting downthrows and strain localization. The mechanism triggering fault reactivation in a carbonate field is the increase of shear stresses with pore-pressure reduction, due to the decrease of the absolute horizontal stress, which leads to an expanded Mohr's circle and mechanical failure, consistent with the predictions of previous poroelastic models. Two scenarios for fault and damage-zone permeability development are explored: (1) large permeability enhancement of a sealing fault upon reactivation, and (2) fault and damage zone permeability development governed by effective mean stress. In the first scenario, the fault becomes highly permeable to across- and along-fault fluid transport, removing local pore pressure highs/lows arising from the presence of the initially sealing fault. In the second scenario, reactivation induces small permeability enhancement in the fault and parts of damage zones, followed by small post-reactivation permeability reduction. Such permeability changes do not appear to change the original flow capacity of the fault or modify the fluid flow velocity fields dramatically.
Directory of Open Access Journals (Sweden)
Li Jun
2015-02-01
Full Text Available In this work, a macroscopic non-linear constitutive model accounting for damage, inelastic strain and unilateral behavior is proposed for the 2D plain-woven C/SiC composite. A set of scalar damage variables and a new thermodynamic potential expression are introduced in the framework of continuum damage mechanics. In the deduced constitutive equations, the material’s progressive damage deactivation behavior during the compression loading is described by a continuous function, and different deactivation rates under uniaxial and biaxial compression loadings are also considered. In damage evolution laws, the coupling effect among the damage modes and impediment effect of compression stress on the development of shear damage in different plane stress states are taken into account. Besides, the general plasticity theory is applied to describing the evolution of inelastic strain in tension and/or shear stress state. The Tsai–Wu failure criterion is adopted for strength analysis. Additionally, the material model is implemented as a user-defined material subroutine (UMAT and linked to the ABAQUS finite element software, and its performance is demonstrated through several numerical examples.
Ma, R; Deng, X L; Du, G L; Li, C; Xiao, S; Aibibai, Y; Zhu, J
2016-06-03
To investigate the protective effect of the active form of vitamin D3, 1,25-(OH)2D3, on macrovasculopathy in rats with type 2 diabetes mellitus (T2DM), 8-week-old male Sprague-Dawley rats were randomly divided into control group, T2DM group, and treatment group. The T2DM model was established after 6 weeks by administering an intraperitoneal injection of streptozotocin (30 mg/kg). 1,25-(OH)2D3 was administered by gavage to rats in the treatment group, and an equal volume of peanut oil was administered to rats in the T2DM group. Fasting plasma glucose (FPG), triglyceride (TG), total cholesterol (TC), high-density lipoprotein (HDL-C) and low-density lipoprotein (LDL-C) cholesterols were measured in all rats. The morphology of the thoracic aorta was examined, and the expression of tumor necrosis factor alpha (TNF-α), endothelin (ET), endothelial nitric oxide synthase (eNOS), CD54, and CD106 in the thoracic aorta was determined by immunohistochemistry. The expression of FPG, TG, TC, and LDL-C in rats from the T2DM and treatment groups was significantly elevated compared with rats from the control group (P 2D3 may protect the macrovessels from injury in T2DM rats by inhibiting the expression of TNF-α, CD54, and CD106.
Leblond, Jean-Baptiste; Frelat, Joël
2014-03-01
It is experimentally well-known that a crack loaded in mode I+III propagates through formation of discrete fracture facets inclined at a certain tilt angle on the original crack plane, depending on the ratio of the mode III to mode I initial stress intensity factors. Pollard et al. (1982) have proposed to calculate this angle by considering the tractions on all possible future infinitesimal facets and assuming shear tractions to be zero on that which will actually develop. In this paper we consider the opposite case of well-developed facets; the stress field near the lateral fronts of such facets becomes independent of the initial crack and essentially 2D in a plane perpendicular to the main direction of crack propagation. To determine this stress field, we solve the model 2D problem of an infinite plate containing an infinite periodic array of cracks inclined at some angle on a straight line, and loaded through uniform stresses at infinity. This is done first analytically, for small values of this angle, by combining Muskhelishvili's (1953) formalism and a first-order perturbation procedure. The formulae found for the 2D stress intensity factors are then extended in an approximate way to larger angles by using another reference solution, and finally assessed through comparison with some finite element results. To finally illustrate the possible future application of these formulae to the prediction of the stationary tilt angle, we introduce the tentative assumption that the 2D mode II stress intensity factor is zero on the lateral fronts of the facets. An approximate formula providing the tilt angle as a function of the ratio of the mode III to mode I stress intensity factors of the initial crack is deduced from there. This formula, which slightly depends on the type of loading imposed, predicts somewhat smaller angles than that of Pollard et al. (1982).
Directory of Open Access Journals (Sweden)
Coppola C
2016-11-01
Full Text Available Carmela Coppola,1 Gennaro Riccio,1 Antonio Barbieri,2 Maria Gaia Monti,3 Giovanna Piscopo,1 Domenica Rea,2 Claudio Arra,2 Carlo Maurea,1 Claudia De Lorenzo,4,5 Nicola Maurea1 1Division of Cardiology, Istituto Nazionale per lo Studio e la Cura dei Tumori “Fondazione G. Pascale”, IRCCS, Naples, Italy; 2Animal Facility Unit, Department of Experimental Oncology, Istituto Nazionale per lo Studio e la Cura dei Tumori “Fondazione G. Pascale”, IRCCS, Naples, Italy; 3Department of Translational Medical Sciences, University Federico II, Naples, Italy; 4Department of Molecular Medicine and Medical Biotechnology, University Federico II, Naples, Italy; 5CEINGE Biotecnologie Avanzate, Naples, Italy Objective: Considering that global left ventricular systolic radial strain is a sensitive technique for the early detection of left ventricular dysfunction due to antineoplastics and the analysis of segmental myocardial contractility, we evaluated this technique for early detection of trastuzumab-related cardiotoxicity by comparing it with cardiac structural damage.Methods: Groups of six mice were injected with trastuzumab or doxorubicin, used either as single agents or in combination. Cardiac function was evaluated by transthoracic echocardiography measurements before and after treatment for 2 or 7 days, by using a Vevo 2100 high-resolution imaging system. After echocardiography, mice were euthanized, and hearts were processed for histological evaluations, such as cardiac fibrosis, apoptosis, capillary density, and inflammatory response.Results: Trastuzumab-related cardiotoxicity was detected early by 2D strain imaging. Radial strain was reduced after 2 days in mice treated with trastuzumab alone (21.2%±8.0% vs 40.5%±4.8% sham; P<0.01. Similarly, trastuzumab was found to induce apoptosis, capillary density reduction, and inflammatory response in cardiac tissue after 2 days of treatment, in a fashion similar to doxorubicin. On the contrary, fractional
On the accuracy of simulations of a 2D boundary layer with RANS models implemented in OpenFoam
Graves, Benjamin J.; Gomez, Sebastian; Poroseva, Svetlana V.
2013-11-01
The OpenFoam software is an attractive Computational Fluid Dynamics solver for evaluating new turbulence models due to the open-source nature, and the suite of existing standard model implementations. Before interpreting results obtained with a new model, a baseline for performance of the OpenFoam solver and existing models is required. In the current study we analyze the RANS models in the OpenFoam incompressible solver for two planar (two-dimensional mean flow) benchmark cases generated by the AIAA Turbulence Model Benchmarking Working Group (TMBWG): a zero-pressure-gradient flat plate and a bump-in-channel. The OpenFoam results are compared against both experimental data and simulation results obtained with the NASA CFD codes CFL3D and FUN3D. Sensitivity of simulation results to the grid resolution and model implementation are analyzed. Testing is conducted using the Spalart-Allmaras one-equation model, Wilcox's two-equation k-omega model, and the Launder-Reece-Rodi Reynolds-stress model. Simulations using both wall functions and wall-resolved (low Reynolds number) formulations are considered. The material is based upon work supported by NASA under award NNX12AJ61A.
Directory of Open Access Journals (Sweden)
Pleite J.
2013-01-01
Full Text Available In this paper we propose and validate by experiment a practical method to compute by simulations the inductance of a ferrite inductor as a function of the current intensity level from the linear to the saturation regions. Our method combines the use of 2D Finite Element Analysis with experimental measurements taken in a laboratory environment. We also present and analyze results of the convergence and computational cost of the 2D and 3D simulations showing the reduction of computational cost when we chose the 2D simulation.
Common Behaviors of Spinor-Type Instantons in 2D Thirring and 4D Gursey Fermionic Models
Directory of Open Access Journals (Sweden)
Fatma Aydogmus
2014-01-01
Full Text Available We investigate two examples of conformal invariant pure spinor fermionic models, which admit particle-like solutions of the classical field equations. For different dimensions and quantum spinor numbers, the vector field visualizations of the models are constructed to provide a better understanding of the spinor-type instanton dynamics in phase space. The hierarchical cluster analysis method investigations of the models are also presented. Finally, the autocorrelation and power spectrum graphs of models are constructed and frequencies of motions are defined.
Global SH-wave propagation in a 2D whole Moon model using the parallel hybrid PSM/FDM method
Jiang, Xianghua; Wang, Yanbin; Qin, Yanfang; Takenaka, Hiroshi
2015-06-01
We present numerical modeling of SH-wave propagation for the recently proposed whole Moon model and try to improve our understanding of lunar seismic wave propagation. We use a hybrid PSM/FDM method on staggered grids to solve the wave equations and implement the calculation on a parallel PC cluster to improve the computing efficiency. Features of global SH-wave propagation are firstly discussed for a 100-km shallow and 900-km deep moonquakes, respectively. Effects of frequency range and lateral variation of crust thickness are then investigated with various models. Our synthetic waveforms are finally compared with observed Apollo data to show the features of wave propagation that were produced by our model and those not reproduced by our models. Our numerical modeling show that the low-velocity upper crust plays significant role in the development of reverberating wave trains. Increasing frequency enhances the strength and duration of the reverberations. Surface multiples dominate wavefields for shallow event. Core-mantle reflections can be clearly identified for deep event at low frequency. The layered whole Moon model and the low-velocity upper crust produce the reverberating wave trains following each phases consistent with observation. However, more realistic Moon model should be considered in order to explain the strong and slow decay scattering between various phases shown on observation data.
Chaudhary, Tarun; Khanna, Gargi
2017-03-01
The purpose of this paper is to explore junctionless double gate vertical slit field effect transistor (JLDG VeSFET) with reduced short channel effects and to develop an analytical threshold voltage model for the device considering the impact of thermal variations for the very first time. The model has been derived by solving 2D Poisson's equation and the effects of variation in temperature on various electrical parameters of the device such as Rout, drain current, mobility, subthreshold slope and DIBL has been studied and described in the paper. The model provides a deep physical insight of the device behavior and is also very helpful in contributing to the design space exploration for JLDG VeSFET. The proposed model is verified with simulative analysis at different radii of the device and it has been observed that there is a good agreement between the analytical model and simulation results.
Directory of Open Access Journals (Sweden)
Salvatore Brischetto
2015-12-01
Full Text Available The present paper talks about the free vibration analysis of simply supported Single- and Double-Walled Carbon Nanotubes (SWCNTs and DWCNTs. Refined 2D Generalized Differential Quadrature (GDQ shell methods and an exact 3D shell model are compared. A continuum approach (based on an elastic three-dimensional shell model is used for natural frequency investigation of SWCNTs and DWCNTs. SWCNTs are defined as isotropic cylinders with an equivalent thickness and Young modulus. DWCNTs are defined as two concentric isotropic cylinders (with an equivalent thickness and Young modulus which can be linked by means of the interlaminar continuity conditions or by means of van der Waals interactions. Layer wise approaches are mandatory for the analysis of van der Waals forces in DWCNTs. The effect of van der Waals interaction between the two cylinders is shown for different DWCNT lengths, diameters and vibration modes. The accuracy of beam models and classical 2D shell models in the free vibration analysis of SWCNTs and DWCNTs is also investigated.
Numerical method for a 2D drift diffusion model arising in strained n-type MOSFET device
Indian Academy of Sciences (India)
BENSEGUENI RACHIDA; LATRECHE SAIDA
2016-06-01
This paper reports the calculation of electron transport in metal oxide semiconductor field effects transistors (MOSFETs) with biaxially tensile strained silicon channel. The calculation is formulated based on two-dimensional drift diffusion model (DDM) including strain effects. The carrier mobility dependence on the lateral and vertical electric field model is especially consideredin the formulation. By using the model presented here, numerical method based on finite difference approach is performed. The obtained results show that the presence of biaxially tensile strain enhances the current in the devices.
A Solvable Model for Fermion masses on a warped 6D world with the extra 2D sphere
Kokado, Akira
2014-01-01
In a warped 6D world with an extra 2-dimensional sphere, we propose an exactly solvable model for fermion masses with zero mode. The warp factor is given by $\\phi (\\theta ,\\varphi )=\\sin{\\theta }\\cos{\\varphi }$, which is a solution to the 6D Einstein equation with the bulk cosmological constant $\\Lambda $ and the energy-momentum tensor of the bulk matter fields. Our model provides another possibility of obtaining fermion zero mode, rather than traditional model based on Dirac's monopole.
Energy Technology Data Exchange (ETDEWEB)
Park, Ju Yeop; In, Wang Kee; Chun, Tae Hyun; Oh, Dong Seok [Korea Atomic Energy Research Institute, Taejeon (Korea)
2000-02-01
The development of orthogonal 2-dimensional numerical code is made. The present code contains 9 kinds of turbulence models that are widely used. They include a standard k-{epsilon} model and 8 kinds of low Reynolds number ones. They also include 6 kinds of numerical schemes including 5 kinds of low order schemes and 1 kind of high order scheme such as QUICK. To verify the present numerical code, pipe flow, channel flow and expansion pipe flow are solved by this code with various options of turbulence models and numerical schemes and the calculated outputs are compared to experimental data. Furthermore, the discretization error that originates from the use of standard k-{epsilon} turbulence model with wall function is much more diminished by introducing a new grid system than a conventional one in the present code. 23 refs., 58 figs., 6 tabs. (Author)
A pseudo 2D chemical model of hot Jupiter atmospheres: application to HD 209458b and HD 189733b
Agundez, Marcelino; Venot, Olivia; Hersant, Franck; Selsis, Franck
2014-01-01
We have developed a pseudo two-dimensional model of a planetary atmosphere, which takes into account thermochemical kinetics, photochemistry, vertical mixing, and horizontal transport, the latter being modeled as a uniform zonal wind. We have applied the model to the atmospheres of the hot Jupiters HD 209458b and HD 189733b. The adopted eddy diffusion coefficients are calculated by following the behaviour of passive tracers in three-dimensional general circulation models, which results in eddy values significantly below previous estimates. We find that the distribution of molecules with altitude and longitude in the atmospheres of these two hot Jupiters is complex because of the interplay of the various physical and chemical processes at work. Much of the distribution of molecules is driven by the strong zonal wind and the limited extent of vertical transport, resulting in an important homogenisation of the chemical composition with longitude. In general, molecular abundances are quenched horizontally to valu...
A coupled 2$\\times$2D Babcock-Leighton solar dynamo model. I. Surface magnetic flux evolution
Lemerle, Alexandre; Carignan-Dugas, Arnaud
2015-01-01
The need for reliable predictions of the solar activity cycle motivates the development of dynamo models incorporating a representation of surface processes sufficiently detailed to allow assimilation of magnetographic data. In this series of papers we present one such dynamo model, and document its behavior and properties. This first paper focuses on one of the model's key components, namely surface magnetic flux evolution. Using a genetic algorithm, we obtain best-fit parameters of the transport model by least-squares minimization of the differences between the associated synthetic synoptic magnetogram and real magnetographic data for activity cycle 21. Our fitting procedure also returns Monte Carlo-like error estimates. We show that the range of acceptable surface meridional flow profiles is in good agreement with Doppler measurements, even though the latter are not used in the fitting process. Using a synthetic database of bipolar magnetic region (BMR) emergences reproducing the statistical properties of ...
Hoch, J. M.; Bierkens, M. F.; Van Beek, R.; Winsemius, H.; Haag, A.
2015-12-01
Understanding the dynamics of fluvial floods is paramount to accurate flood hazard and risk modeling. Currently, economic losses due to flooding constitute about one third of all damage resulting from natural hazards. Given future projections of climate change, the anticipated increase in the World's population and the associated implications, sound knowledge of flood hazard and related risk is crucial. Fluvial floods are cross-border phenomena that need to be addressed accordingly. Yet, only few studies model floods at the large-scale which is preferable to tiling the output of small-scale models. Most models cannot realistically model flood wave propagation due to a lack of either detailed channel and floodplain geometry or the absence of hydrologic processes. This study aims to develop a large-scale modeling tool that accounts for both hydrologic and hydrodynamic processes, to find and understand possible sources of errors and improvements and to assess how the added hydrodynamics affect flood wave propagation. Flood wave propagation is simulated by DELFT3D-FM (FM), a hydrodynamic model using a flexible mesh to schematize the study area. It is coupled to PCR-GLOBWB (PCR), a macro-scale hydrological model, that has its own simpler 1D routing scheme (DynRout) which has already been used for global inundation modeling and flood risk assessments (GLOFRIS; Winsemius et al., 2013). A number of model set-ups are compared and benchmarked for the simulation period 1986-1996: (0) PCR with DynRout; (1) using a FM 2D flexible mesh forced with PCR output and (2) as in (1) but discriminating between 1D channels and 2D floodplains, and, for comparison, (3) and (4) the same set-ups as (1) and (2) but forced with observed GRDC discharge values. Outputs are subsequently validated against observed GRDC data at Óbidos and flood extent maps from the Dartmouth Flood Observatory. The present research constitutes a first step into a globally applicable approach to fully couple
2D semiconductor optoelectronics
Novoselov, Kostya
The advent of graphene and related 2D materials has recently led to a new technology: heterostructures based on these atomically thin crystals. The paradigm proved itself extremely versatile and led to rapid demonstration of tunnelling diodes with negative differential resistance, tunnelling transistors, photovoltaic devices, etc. By taking the complexity and functionality of such van der Waals heterostructures to the next level we introduce quantum wells engineered with one atomic plane precision. Light emission from such quantum wells, quantum dots and polaritonic effects will be discussed.