Tame Kernels of Pure Cubic Fields
Institute of Scientific and Technical Information of China (English)
Xiao Yun CHENG
2012-01-01
In this paper,we study the p-rank of the tame kernels of pure cubic fields.In particular,we prove that for a fixed positive integer m,there exist infinitely many pure cubic fields whose 3-rank of the tame kernel equal to m.As an application,we determine the 3-rank of their tame kernels for some special pure cubic fields.
CLASSIFICATION OF CUBIC PARAMETERIZED HOMOGENEOUS VECTOR FIELDS
Institute of Scientific and Technical Information of China (English)
Karnal H.Yasir; TANG Yun
2002-01-01
In this paper the cubic homogeneous parameterized vector fields are studied.The classification of the phase portrait near the critical point is presented. This classification is an extension of the result given by Takens to the cubic homogeneous parameterized vector fields with six parameters.
CLASSIFICATION OF CUBIC PARAMETERIZED HOMOGENEOUS VECTOR FIELDS
Institute of Scientific and Technical Information of China (English)
KamalH.Yasir; TNAGYun
2002-01-01
In this paper the cubic homogeneous parameterized vector fields are studied.The classification of the phase portrait near the critical point is presented.This classification is an extension of the result given by takens to the cubic homogeneous parameterized vector fields with six parameters.
National Research Council Canada - National Science Library
Goodwin, Adrian N
2009-01-01
A flexible tree taper model based on a cubic polynomial is described. It is algebraically invertible and integrable, and can be constrained by one or two diameters, neither of which need be diameter at breast height (DBH...
Binomial Squares in Pure Cubic Number Fields
Lemmermeyer, Franz
2011-01-01
Let K = Q(\\omega) with \\omega^3 = m be a pure cubic number field. We show that the elements\\alpha \\in K^\\times whose squares have the form a - \\omega form a group isomorphic to the group of rational points on the elliptic curve E_m: y^2= x^3 - m.
Purely cubic action for string field theory
Horowitz, G. T.; Lykken, J.; Rohm, R.; Strominger, A.
1986-01-01
It is shown that Witten's (1986) open-bosonic-string field-theory action and a closed-string analog can be written as a purely cubic interaction term. The conventional form of the action arises by expansion around particular solutions of the classical equations of motion. The explicit background dependence of the conventional action via the Becchi-Rouet-Stora-Tyutin operator is eliminated in the cubic formulation. A closed-form expression is found for the full nonlinear gauge-transformation law.
Purely cubic action for string field theory
Horowitz, G. T.; Lykken, J.; Rohm, R.; Strominger, A.
1986-01-01
It is shown that Witten's (1986) open-bosonic-string field-theory action and a closed-string analog can be written as a purely cubic interaction term. The conventional form of the action arises by expansion around particular solutions of the classical equations of motion. The explicit background dependence of the conventional action via the Becchi-Rouet-Stora-Tyutin operator is eliminated in the cubic formulation. A closed-form expression is found for the full nonlinear gauge-transformation law.
Tachyon Vacuum in Cubic Superstring Field Theory
Erler, Theodore
2008-01-01
In this paper we give an exact analytic solution for tachyon condensation in the modified (picture 0) cubic superstring field theory. We prove the absence of cohomology and, crucially, reproduce the correct value for the D-brane tension. The solution is surprising for two reasons: First, the existence of a tachyon vacuum in this theory has not been definitively established in the level expansion. Second, the solution {\\it vanishes} in the GSO$(-)$ sector, implying a ``tachyon vacuum'' solution exists even for a {\\it BPS} D-brane.
On cubic equations over $P-$adic field
Mukhamedov, Farrukh; Saburov, Mansoor
2012-01-01
We provide a solvability criteria for a depressed cubic equation in domains $\\bz_p^{*},\\bz_p,\\bq_p$. We show that, in principal, the Cardano method is not always applicable for such equations. Moreover, the numbers of solutions of the depressed cubic equation in domains $\\bz_p^{*},\\bz_p,\\bq_p$ are provided. Since $\\bbf_p\\subset\\bq_p,$ we generalize J.-P. Serre's \\cite{JPSJ} and Z.H.Sun's \\cite{ZHS1,ZHS3} results concerning with depressed cubic equations over the finite field $\\bbf_p$. Finally, all depressed cubic equations, for which the Cardano method could be applied, are described and the $p-$adic Cardano formula is provided for those cubic equations.
A cubic interpolation pipeline for fast computation of 3D deformation fields modeled using B-splines
Castro-Pareja, Carlos R.; Shekhar, Raj
2006-02-01
Fast computation of 3D deformation fields is critical to bringing the application of automated elastic image registration algorithms to routine clinical practice. However, it lies beyond the computational power of current microprocessors; therefore requiring implementations using either massively parallel computers or application-specific hardware accelerators. The use of massively parallel computers in a clinical setting is not practical or cost-effective, therefore making the use of hardware accelerators necessary. We present a hardware pipeline that allows accelerating the computation of 3D deformation fields to speeds up to two orders of magnitude faster than software implementations on current workstations and about 64 times faster than other previously reported architectures. The pipeline implements a version of the free-form deformation calculation algorithm, which is optimized to minimize the number of arithmetic operations required to calculate the transformation of a given set of neighboring voxels, thereby achieving an efficient and compact implementation in hardware which allows its use as part of a larger system.
Bast, Radovan; Thorvaldsen, Andreas J.; Ringholm, Magnus; Ruud, Kenneth
2009-02-01
We present the first analytic calculations of the second hyperpolarizability in a relativistic framework. The calculations are made possible by our recent developments of a response theory built on a quasienergy formalism, in which the basis set may be both time and perturbation dependent. The approach is formulated for an arbitrary self-consistent field state in the atomic orbital basis. The implementation consists of a stand-alone code that only requires the unperturbed density in the atomic orbital basis as input, as well as a linear response solver by which we can determine the perturbed density matrices to different orders, at each new order solving equations that have the same structure as the linear response equation. Using these features of our formalism, we extend in this paper our approach to the relativistic domain, utilizing both two- and four-component relativistic wave functions. We apply the formalism to the calculation of the electronic and pure vibrational contributions to the second hyperpolarizability tensor for the hydrogen halides. Our results demonstrate that relativistic effects can be substantial for frequency-dependent second hyperpolarizabilities. Due to changes in the pole structure when going to the relativistic domain, the relativistic corrections to the hyperpolarizabilities are not transferable between different optical processes, except for very low frequencies.
Energy Technology Data Exchange (ETDEWEB)
Bast, Radovan; Thorvaldsen, Andreas J.; Ringholm, Magnus [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromso, N-9037 Tromso (Norway); Ruud, Kenneth [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromso, N-9037 Tromso (Norway)], E-mail: kenneth.ruud@chem.uit.no
2009-02-17
We present the first analytic calculations of the second hyperpolarizability in a relativistic framework. The calculations are made possible by our recent developments of a response theory built on a quasienergy formalism, in which the basis set may be both time and perturbation dependent. The approach is formulated for an arbitrary self-consistent field state in the atomic orbital basis. The implementation consists of a stand-alone code that only requires the unperturbed density in the atomic orbital basis as input, as well as a linear response solver by which we can determine the perturbed density matrices to different orders, at each new order solving equations that have the same structure as the linear response equation. Using these features of our formalism, we extend in this paper our approach to the relativistic domain, utilizing both two- and four-component relativistic wave functions. We apply the formalism to the calculation of the electronic and pure vibrational contributions to the second hyperpolarizability tensor for the hydrogen halides. Our results demonstrate that relativistic effects can be substantial for frequency-dependent second hyperpolarizabilities. Due to changes in the pole structure when going to the relativistic domain, the relativistic corrections to the hyperpolarizabilities are not transferable between different optical processes, except for very low frequencies.
Cubic ideal ferromagnets at low temperature and weak magnetic field
Hofmann, Christoph P.
2017-04-01
The low-temperature series for the free energy density, pressure, magnetization and susceptibility of cubic ideal ferromagnets in weak external magnetic fields are discussed within the effective Lagrangian framework up to three loops. The structure of the simple, body-centered, and face-centered cubic lattice is taken into account explicitly. The expansion involves integer and half-integer powers of the temperature. The corresponding coefficients depend on the magnetic field and on low-energy effective constants that can be expressed in terms of microscopic quantities. Our formulas may also serve as efficiency or consistency check for other techniques like Green's function methods, where spurious terms in the low-temperature expansion have appeared. We explore the sign and magnitude of the spin-wave interaction in the pressure, magnetization and susceptibility, and emphasize that our effective field theory approach is fully systematic and rigorous.
Arithmetic Problems in Cubic and Quartic Function Fields
Bembom, Tobias
2010-01-01
One of the main themes in this thesis is the description of the signature of both the infinite place and the finite places in cubic function fields of any characteristic and quartic function fields of characteristic at least 5. For these purposes, we provide a new theory which can be applied to cubic and quartic function fields and to even higher dimensional function fields. One of the striking advantages of this theory to other existing methods is that is does not use the concept of p-adic completions and we can dispense of Cardano's formulae. Another key result comprises the construction of cubic function fields of unit rank 1 and 2, with an obvious fundamental system. One of the main ingredients for such constructions is the definition of the maximum value. This definition is new and very prolific in the context of finding fundamental systems. We conclude the thesis with miscellaneous results on the divisor class number h, including a new approach for finding divisors of h.
Field-effect transistors based on cubic indium nitride.
Oseki, Masaaki; Okubo, Kana; Kobayashi, Atsushi; Ohta, Jitsuo; Fujioka, Hiroshi
2014-02-04
Although the demand for high-speed telecommunications has increased in recent years, the performance of transistors fabricated with traditional semiconductors such as silicon, gallium arsenide, and gallium nitride have reached their physical performance limits. Therefore, new materials with high carrier velocities should be sought for the fabrication of next-generation, ultra-high-speed transistors. Indium nitride (InN) has attracted much attention for this purpose because of its high electron drift velocity under a high electric field. Thick InN films have been applied to the fabrication of field-effect transistors (FETs), but the performance of the thick InN transistors was discouraging, with no clear linear-saturation output characteristics and poor on/off current ratios. Here, we report the epitaxial deposition of ultrathin cubic InN on insulating oxide yttria-stabilized zirconia substrates and the first demonstration of ultrathin-InN-based FETs. The devices exhibit high on/off ratios and low off-current densities because of the high quality top and bottom interfaces between the ultrathin cubic InN and oxide insulators. This first demonstration of FETs using a ultrathin cubic indium nitride semiconductor will thus pave the way for the development of next-generation high-speed electronics.
The Body Center Cubic Quark Lattice Model
Lin Xu, Jiao
2004-01-01
The Standard Model while successful in many ways is incomplete; many questions remain. The origin of quark masses and hadronization of quarks are awaiting an answer. From the Dirac sea concept, we infer that two kinds of elementary quarks (u(0) and d(0)) constitute a body center cubic (BCC) quark lattice with a lattice constant a < $10^{-18}$m in the vacuum. Using energy band theory and the BCC quark lattice, we can deduce the rest masses and the intrinsic quantum numbers (I, S, C, b and Q) of quarks. With the quark spectrum, we deduce a baryon spectrum. The theoretical spectrum is in agreement well with the experimental results. Not only will this paper provide a physical basis for the Quark Model, but also it will open a door to study the more fundamental nature at distance scales <$10^{-18}$m. This paper predicts some new quarks $u_{c}$(6490) and d$_{b}$(9950), and new baryons $\\Lambda_{c}^{+}$(6500), $\\Lambda_{b}^{0}$(9960).
Gauge Fixing of Modified Cubic Open Superstring Field Theory
Kohriki, Maiko; Kunitomo, Hiroshi
2011-01-01
The gauge-fixing problem of modified cubic open superstring field theory is discussed in detail both for the Ramond and Neveu-Schwarz sectors in the Batalin-Vilkovisky (BV) framework. We prove for the first time that the same form of action as the classical gauge-invariant one with the ghost-number constraint on the string field relaxed gives the master action satisfying the BV master equation. This is achieved by identifying independent component fields based on the analysis of the kernel structure of the inverse picture changing operator. The explicit gauge-fixing conditions for the component fields are discussed. In a kind of $b_0=0$ gauge, we explicitly obtain the NS propagator which has poles at the zeros of the Virasoro operator $L_0$.
Exotic Universal Solutions in Cubic Superstring Field Theory
Erler, Theodore
2010-01-01
We present a class of analytic solutions of cubic superstring field theory in the universal sector on a non-BPS D-brane. Computation of the action and gauge invariant overlap reveal that the solutions carry half the tension of a non-BPS D-brane. However, the solutions do not satisfy the reality condition. In fact, they display an intriguing topological structure: We find evidence that conjugation of the solutions is equivalent to a gauge transformation that cannot be continuously deformed to the identity.
CSIR Research Space (South Africa)
Park, R
2010-09-01
Full Text Available being made for rainfall, maximum and minimum temperatures, and wind fields using the new Conformal- Cubic Atmospheric Model (CCAM). This model has been adapted and developed since its initialisation, increasing its weather prediction capability in order...
Specific heat of the simple-cubic Ising model
Feng, X.; Blöte, H.W.J.
2010-01-01
We provide an expression quantitatively describing the specific heat of the Ising model on the simple-cubic lattice in the critical region. This expression is based on finite-size scaling of numerical results obtained by means of a Monte Carlo method. It agrees satisfactorily with series expansions
Multiscale Modeling of Point and Line Defects in Cubic Lattices
2007-01-01
and discli- nations with finite micropolar elastoplasticity . Int. J. Plasticity. 22:210–256, 2006. 56. Menzel, A., and Steinmann, P., On the contin...Voyiadjis, G. Z., A finite strain plastic- damage model for high velocity impact using combined viscosity and gradient localization limiters: Part I...Theoretical for- mulation. Int. J. Damage Mech. 15:293–334, 2006. 58. Milstein, F., and Chantasiriwan, S,. Theoretical study of the response of 12 cubic
Ferrighi, Lara; Frediani, Luca; Ruud, Kenneth
2010-01-01
The theory and an implementation of the solvent contribution to the cubic response function for the polarizable continuum model for multiconfigurational self-consistent field wave functions is presented. The excited-state polarizability of benzene, para-nitroaniline, and nitrobenzene has been obtained from the double residue of the cubic response function calculated in the presence of an acetonitrile and dioxane solvent. The calculated excited-state polarizabilities are compared to results obtained from the linear response function of the explicitly optimized excited states.
Finite Element Treatment of Vortex States in 3D Cubic Superconductors in a Tilted Magnetic Field
Peng, Lin; Cai, Chuanbing
2017-03-01
The time-dependent Ginzburg-Landau equations have been solved numerically by a finite element analysis for superconducting samples with a cubic shape in a tilted magnetic field. We obtain different vortex patterns as a function of the external magnetic field. With a magnetic field not parallel to the x- or y-axis, the vortices attempt to change their orientation accordingly. Our analysis of the corresponding changes in the magnetic response in different directions can provide information not only about vorticity but also about the three-dimensional vortex arrangement, even about the very subtle changes for the superconducting samples with a cubic shape in a tilted magnetic field.
Nonlinear structure formation in the Cubic Galileon gravity model
Barreira, Alexandre; Hellwing, Wojciech A; Baugh, Carlton M; Pascoli, Silvia
2013-01-01
We model the linear and nonlinear growth of large scale structure in the Cubic Galileon gravity model, by running a suite of N-body cosmological simulations using the {\\tt ECOSMOG} code. Our simulations include the Vainshtein screening effect, which reconciles the Cubic Galileon model with local tests of gravity. In the linear regime, the amplitude of the matter power spectrum increases by $\\sim 25%$ with respect to the standard $\\Lambda$CDM model today. The modified expansion rate accounts for $\\sim 20%$ of this enhancement, while the fifth force is responsible for only $\\sim 5%$. This is because the effective unscreened gravitational strength deviates from standard gravity only at late times, even though it can be twice as large today. In the nonlinear regime ($k \\gtrsim 0.1 h\\rm{Mpc}^{-1}$), the fifth force leads to only a modest increase ($\\lesssim 8%$) in the clustering power on all scales due to the very efficient operation of the Vainshtein mechanism. Such a strong effect is typically not seen in other...
Analytical Solution of Linear, Quadratic and Cubic Model of PTT Fluid
Directory of Open Access Journals (Sweden)
Naeem Faraz
2015-07-01
Full Text Available An attempt is made for the first time to solve the quadratic and cubic model of magneto hydrodynamic Poiseuille flow of Phan-Thein-Tanner (PTT. Series solution of magneto hydrodynamic (MHD flow is developed by using homotopy perturbation method (HPM. Results are presented graphically and the effects of non-dimensional parameters on the flow field are analyzed. The results obtained reveals many interesting behaviors that warrant further study on the equations related to non-Newtonian fluid phenomena.
Adaptive Predistortion Using Cubic Spline Nonlinearity Based Hammerstein Modeling
Wu, Xiaofang; Shi, Jianghong
In this paper, a new Hammerstein predistorter modeling for power amplifier (PA) linearization is proposed. The key feature of the model is that the cubic splines, instead of conventional high-order polynomials, are utilized as the static nonlinearities due to the fact that the splines are able to represent hard nonlinearities accurately and circumvent the numerical instability problem simultaneously. Furthermore, according to the amplifier's AM/AM and AM/PM characteristics, real-valued cubic spline functions are utilized to compensate the nonlinear distortion of the amplifier and the following finite impulse response (FIR) filters are utilized to eliminate the memory effects of the amplifier. In addition, the identification algorithm of the Hammerstein predistorter is discussed. The predistorter is implemented on the indirect learning architecture, and the separable nonlinear least squares (SNLS) Levenberg-Marquardt algorithm is adopted for the sake that the separation method reduces the dimension of the nonlinear search space and thus greatly simplifies the identification procedure. However, the convergence performance of the iterative SNLS algorithm is sensitive to the initial estimation. Therefore an effective normalization strategy is presented to solve this problem. Simulation experiments were carried out on a single-carrier WCDMA signal. Results show that compared to the conventional polynomial predistorters, the proposed Hammerstein predistorter has a higher linearization performance when the PA is near saturation and has a comparable linearization performance when the PA is mildly nonlinear. Furthermore, the proposed predistorter is numerically more stable in all input back-off cases. The results also demonstrate the validity of the convergence scheme.
On the 3-rank of tame kernels of certain pure cubic number fields
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
In this paper,we present some explicit formulas for the 3-rank of the tame kernels of certain pure cubic number fields,and give the density results concerning the 3-rank of the tame kernels.Numerical examples are given in Tables 1 and 2.
Gagnon, Jean-Sébastien; Pérez-Mercader, Juan
2017-08-01
We study the effect of external power-law noise on the renormalizability of a specific reaction-diffusion system of equations describing a cubic autocatalytic chemical reaction. We show that changing the noise exponent modifies the divergence structure of loop integrals and thus the renormalizability of the model. The effects of noise-generated higher order interactions are discussed. We show how noise induces new interaction terms that can be interpreted as a manifestation of some (internal) ;chemical mechanism;. We also show how ideas of effective field theory can be applied to construct a more fundamental chemical model for this system.
Bifurcation and Isochronicity at Infinity in a Class of Cubic Polynomial Vector Fields
Institute of Scientific and Technical Information of China (English)
Qin-long Wang; Yi-rong Liu
2007-01-01
In this paper, we study the appearance of limit cycles from the equator and isochronicity of infinity in polynomial vector fields with no singular points at infinity. We give a recursive formula to compute the singular point quantities of a class of cubic polynomial systems, which is used to calculate the first seven singular point quantities. Further, we prove that such a cubic vector field can have maximal seven limit cycles in the neighborhood of infinity. We actually and construct a system that has seven limit cycles. The positions of these limit cycles can be given exactly without constructing the Poincare cycle fields. The technique employed in this work is essentially different from the previously widely used ones. Finally, the isochronous center conditions at infinity are given.
The Electric Field of a Uniformly Charged Non-Conducting Cubic Surface
McCreery, Kaitlin
2016-01-01
As an integrative and insightful example for undergraduates learning about electrostatics, we discuss how to use symmetry, Coulomb's Law, superposition, Gauss's law, and visualization to understand the electric field produced by a non-conducting cubic surface that is covered with a uniform surface charge density. We first discuss how to deduce qualitatively, using only elementary physics, the surprising fact that the electric field inside the cubic surface is nonzero and has a complex structure, pointing inwards towards the cube center from the midface of each cube and pointing outwards towards each edge and corner. We then discuss how to understand the quantitative features of the electric field by plotting an analytical expression for E along symmetry lines and on symmetry surfaces. This example would be a good choice for group problem solving in a recitation or flipped classroom.
On Gauge Equivalence of Tachyon Solutions in Cubic Neveu-Schwarz String Field Theory
Aref'eva, I Ya
2010-01-01
Simple analytic solution to cubic Neveu-Schwarz String Field Theory including the $GSO(-)$ sector is presented. This solution is an analog of the Erler-Schnabl solution for bosonic case and one of the authors solution for the pure $GSO(+)$ case. Gauge transformations of the new solution to others known solutions for the $NS$ string tachyon condensation are constructed explicitly. This gauge equivalence manifestly supports the early observed fact that these solutions have the same value of the action density.
Crystal field effects on interionic distance in cubic MgO crystal doped with Fe{sup 2+} ions
Energy Technology Data Exchange (ETDEWEB)
Ivascu, S.; Gruia, A.S. [Faculty of Physics, West University of Timisoara, Bd. V. Parvan 4, 300223-Timisoara (Romania); Avram, N.M., E-mail: avram@physics.uvt.ro [Faculty of Physics, West University of Timisoara, Bd. V. Parvan 4, 300223-Timisoara (Romania); Academy of Romanian Scientists, Independentei 54, 050094-Bucharest (Romania)
2014-10-01
The exchange charge model of crystal field was applied to determine the dependence of the crystal field strength 10Dq on interionic distances R between the Fe{sup 2+} impurity ion and O{sup 2−} ligands in cubic MgO:Fe{sup 2+}. The obtained results were extrapolated by the power law and was shown that 10Dq depends on R as 1/R{sup n}, with n=6.3486. The deviations of these values from the value n=5 (predicted by the simple point charge model of crystal field) is explained by the covalent and exchange effects between impurity ion and ligands; the contribution of these effects into the total crystal field strength was considered separately. The 10Dq functions obtained as a result of our calculations were used for estimations of the electron–vibrational constants, Huang–Rhys parameters, and Jahn–Teller stabilization energy, and compared with available literature data.
Crystal field effects on interionic distance in cubic MgO crystal doped with Fe2+ ions
Ivascu, S.; Gruia, A. S.; Avram, N. M.
2014-10-01
The exchange charge model of crystal field was applied to determine the dependence of the crystal field strength 10Dq on interionic distances R between the Fe2+ impurity ion and O2- ligands in cubic MgO:Fe2+. The obtained results were extrapolated by the power law and was shown that 10Dq depends on R as 1/R, with n=6.3486. The deviations of these values from the value n=5 (predicted by the simple point charge model of crystal field) is explained by the covalent and exchange effects between impurity ion and ligands; the contribution of these effects into the total crystal field strength was considered separately. The 10Dq functions obtained as a result of our calculations were used for estimations of the electron-vibrational constants, Huang-Rhys parameters, and Jahn-Teller stabilization energy, and compared with available literature data.
Stable vortex solitons in a vectorial cubic-quintic model
Energy Technology Data Exchange (ETDEWEB)
Mihalache, D [Department of Theoretical Physics, Institute of Atomic Physics, PO Box MG-6, Bucharest (Romania); Mazilu, D [Department of Theoretical Physics, Institute of Atomic Physics, PO Box MG-6, Bucharest (Romania); Malomed, B A [Department of Interdisciplinary Studies, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978 (Israel); Lederer, F [Institute of Solid State Theory and Theoretical Optics, Friedrich-Schiller Universitaet Jena, Max-Wien-Platz 1, D-07743, Jena (Germany)
2004-05-01
We investigate the stability of vectorial (two-component) vortex solitons of two types. Their stationary shapes are identical, but their stability (which is the most important issue for spinning solitons) is drastically different. These are solitons with vorticities (S,S) and (S,-S) in the two components. The analysis is performed in a vectorial cubic-quintic model, with the two components nonlinearly coupled by the incoherent cross-phase-modulation interaction, but we expect that the results are quite generic. The stability was investigated by means of computing eigenvalues of perturbations around the stationary solitons, as well as in direct simulations. We also report new analytical results for the well-known problem of the description of the stationary form of scalar solitons in media of this type. The analytical results explain the shape of the spinning solitons, and the strong dependence of their norm (power) on the vorticity, in both the 2D and 3D cases. In this paper we also give the first estimate of the physical characteristics (power and radius) of the stable solitons with different values of S, making use of recently measured values of the necessary nonlinear parameters. All the two-component solitons of type (S,-S) are unstable. In contrast, those of type (S,S) have their stability regions, the size of which strongly depends on S. An unstable soliton always splits into a set of separating zero-spin ones, in precise compliance with the azimuthal index of the most unstable perturbation eigenmode. Direct simulations demonstrate that stable solitons readily self-trap from arbitrary initial pulses which belong to their topological class.
Study of unsteady cavitation on NACA66 hydrofoil using dynamic cubic nonlinear subgrid-scale model
Directory of Open Access Journals (Sweden)
Xianbei Huang
2015-11-01
Full Text Available In this article, we describe the use of a new dynamic cubic nonlinear model, a new nonlinear subgrid-scale model, for simulating the cavitating flow around an NACA66 series hydrofoil. For comparison, the dynamic Smagorinsky model is also used. It is found that the dynamic cubic nonlinear model can capture the turbulence spectrum, while the dynamic Smagorinsky model fails. Both models reproduce the cavity growth/destabilization cycle, but the results of the dynamic cubic nonlinear model are much smoother. The re-entrant jet is clearly captured by the models, and it is shown that the re-entrant jet cuts the cavity into two parts. In general, the dynamic cubic nonlinear model provides improvement over the dynamic Smagorinsky model for the calculation of cavitating flow.
Generating Erler-Schnabl-type Solution for Tachyon Vacuum in Cubic Superstring Field Theory
Arroyo, E Aldo
2010-01-01
We analyze a new class of identity-based solutions in open bosonic string field theory and cubic superstring field theory. Even though these solutions seem to be trivial, it turns out that after performing a suitable gauge transformation, we are left with the known Erler-Schnabl-type solutions which correctly reproduce the value for the D-brane tension. This important result shows explicitly that how a seemingly trivial solution can generate a non-trivial configuration which precisely represents the tachyon vacuum.
Generating Erler-Schnabl-type solution for the tachyon vacuum in cubic superstring field theory
Aldo Arroyo, E.
2010-11-01
We study a new set of identity-based solutions to analyze the problem of tachyon condensation in open bosonic string field theory and cubic superstring field theory. Even though these identity-based solutions seem to be trivial, it turns out that after performing a suitable gauge transformation, we are left with the known Erler-Schnabl-type solutions which correctly reproduce the value of the D-brane tension. This result shows explicitly that a seemingly trivial solution can generate a non-trivial configuration which precisely represents the tachyon vacuum.
Higher-Order Approximation of Cubic-Quintic Duffing Model
DEFF Research Database (Denmark)
Ganji, S. S.; Barari, Amin; Babazadeh, H.
2011-01-01
We apply an Artificial Parameter Lindstedt-Poincaré Method (APL-PM) to find improved approximate solutions for strongly nonlinear Duffing oscillations with cubic-quintic nonlinear restoring force. This approach yields simple linear algebraic equations instead of nonlinear algebraic equations...... without analytical solution which makes it a unique solution. It is demonstrated that this method works very well for the whole range of parameters in the case of the cubic-quintic oscillator, and excellent agreement of the approximate frequencies with the exact one has been observed and discussed....... Moreover, it is not limited to the small parameter such as in the classical perturbation method. Interestingly, this study revealed that the relative error percentage in the second-order approximate analytical period is less than 0.042% for the whole parameter values. In addition, we compared...
Energy Technology Data Exchange (ETDEWEB)
Cortijo, Alberto [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid (Spain); Zubkov, M.A., E-mail: zubkov@itep.ru [ITEP, B. Cheremushkinskaya 25, Moscow, 117259 (Russian Federation); Moscow Institute of Physics and Technology, 9, Institutskii per., Dolgoprudny, Moscow Region, 141700 (Russian Federation); Far Eastern Federal University, School of Biomedicine, 690950 Vladivostok (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoe highway 31, 115409 Moscow (Russian Federation)
2016-03-15
We consider the tight-binding model with cubic symmetry that may be relevant for the description of a certain class of Weyl semimetals. We take into account elastic deformations of the semimetal through the modification of hopping parameters. This modification results in the appearance of emergent gauge field and the coordinate dependent anisotropic Fermi velocity. The latter may be interpreted as emergent gravitational field.
Gauge equivalence of Tachyon solutions in the cubic Neveu—Schwarz string field theory
Aref'eva, I. Ya.; Gorbachev, R. V.
2010-11-01
We construct a simple analytic solution of the cubic Neveu—Schwarz (NS) string field theory including the GSO(-) sector. This solution is analogous to the Erler—Schnabl solution in the bosonic case and to the solution in the pure GSO(+) case previously proposed by one of us. We construct exact gauge transformations of the new solution to other known solutions for the NS string tachyon condensation. This gauge equivalence manifestly supports the previous observation that the Erler solution for the pure GSO(+) sector and our solution containing both the GSO(+) and the GSO(-) sectors have the same value of the action density.
Indian Academy of Sciences (India)
Nahid Ashrafi
2009-06-01
The unit sum number, $u(R)$, of a ring is the least such that every element is the sum of units; if there is no such then $u(R)$ is or ∞ depending on whether the units generate additively or not. Here we introduce a finer classification for the unit sum number of a ring and in this new classification we completely determine the unit sum number of the ring of integers of a quadratic field. Further we obtain some results on cubic complex fields which one can decide whether the unit sum number is or ∞. Then we present some examples showing that all possibilities can occur.
PT-Symmetric Cubic Anharmonic Oscillator as a Physical Model
Mostafazadeh, A
2004-01-01
We perform a perturbative calculation of the physical observables, in particular pseudo-Hermitian position and momentum operators, the equivalent Hermitian Hamiltonian operator, and the classical Hamiltonian for the PT-symmetric cubic anharmonic oscillator, $ H=p^1/(2m)+\\mu^2x^2/2+i\\epsilon x^3 $. Ignoring terms of order $ \\epsilon^4 $ and higher, we show that this system describes an ordinary quartic anharmonic oscillator with a position-dependent mass and real and positive coupling constants. This observation elucidates the classical origin of the reality and positivity of the energy spectrum. We also discuss the quantum-classical correspondence for this PT-symmetric system, compute the associated conserved probability density, and comment on the issue of factor-ordering in the pseudo-Hermitian canonical quantization of the underlying classical system.
Studies on the second-harmonic generations in cubical quantum dots with applied electric field
Energy Technology Data Exchange (ETDEWEB)
Shao Shuai [Department of Physics, College of Physics and Electronic Engineering, Guangzhou University, Guangzhou 510006 (China); Guo Kangxian, E-mail: axguo@sohu.co [Department of Physics, College of Physics and Electronic Engineering, Guangzhou University, Guangzhou 510006 (China); Zhang Zhihai; Li Ning; Peng Chao [Department of Physics, College of Physics and Electronic Engineering, Guangzhou University, Guangzhou 510006 (China)
2011-02-01
The second-harmonic generation (SHG) coefficient for cubical quantum dots (CQDs) with the applied electric field is theoretically investigated. Using the compact density-matrix approach and the iterative method, we get the analytical expression of the SHG coefficient. And the numerical calculations for the typical GaAs/AlAs CQDs are presented. The results show that the SHG coefficient can reach the magnitude of 10{sup -5} m/V, about two orders higher than that in spherical quantum dot system. More importantly, the SHG coefficient is not a monotonic function of the length L of CQDs as well as the applied field F. If we select suitable values of F and L, we will get a higher value of the SHG coefficient. In addition, the relaxation rate also affects the SHG coefficient obviously.
Ohshima, T; Ishida, Y
2003-01-01
The n-channel metal-oxide-semiconductor field effect transistors (MOSFETs) were fabricated on cubic silicon carbide (3C-SiC) epitaxial layers grown on 3C-SiC substrates. The gate oxide of the MOSFETs was formed using pyrogenic oxidation at 1100 degC. The 3C-SiC MOSFETs showed enhancement type behaviors after annealing at 200degC for 30 min in argon atmosphere. The maximum value of the effective channel mobility of the 3C-SiC MOSFETs was 260cm sup 2 /V centre dot s. The leakage current of gate oxide was of a few tens of nA/cm sup 2 at an electric field range below 8.5 MV/cm, and breakdown began around 8.5MV/cm. (author)
Grajeda, Laura M; Ivanescu, Andrada; Saito, Mayuko; Crainiceanu, Ciprian; Jaganath, Devan; Gilman, Robert H; Crabtree, Jean E; Kelleher, Dermott; Cabrera, Lilia; Cama, Vitaliano; Checkley, William
2016-01-01
Childhood growth is a cornerstone of pediatric research. Statistical models need to consider individual trajectories to adequately describe growth outcomes. Specifically, well-defined longitudinal models are essential to characterize both population and subject-specific growth. Linear mixed-effect models with cubic regression splines can account for the nonlinearity of growth curves and provide reasonable estimators of population and subject-specific growth, velocity and acceleration. We provide a stepwise approach that builds from simple to complex models, and account for the intrinsic complexity of the data. We start with standard cubic splines regression models and build up to a model that includes subject-specific random intercepts and slopes and residual autocorrelation. We then compared cubic regression splines vis-à-vis linear piecewise splines, and with varying number of knots and positions. Statistical code is provided to ensure reproducibility and improve dissemination of methods. Models are applied to longitudinal height measurements in a cohort of 215 Peruvian children followed from birth until their fourth year of life. Unexplained variability, as measured by the variance of the regression model, was reduced from 7.34 when using ordinary least squares to 0.81 (p linear mixed-effect models with random slopes and a first order continuous autoregressive error term. There was substantial heterogeneity in both the intercept (p linear regression equation for both estimation and prediction of population- and individual-level growth in height. We show that cubic regression splines are superior to linear regression splines for the case of a small number of knots in both estimation and prediction with the full linear mixed effect model (AIC 19,352 vs. 19,598, respectively). While the regression parameters are more complex to interpret in the former, we argue that inference for any problem depends more on the estimated curve or differences in curves rather
Yamagata, Atsushi
1994-01-01
We perform the Monte Carlo simulations of the hard-sphere lattice gas on the simple cubic lattice with nearest neighbour exclusion. The critical activity is estimated, $z_{\\rm c} = 1.0588 \\pm 0.0003$. Using a relation between the hard-sphere lattice gas and the antiferromagnetic Ising model in an external magnetic field, we conclude that there is no re-entrant phase transition of the latter on the simple cubic lattice.
BV analysis of tachyon fluctuation around multi-brane solutions in cubic string field theory
Hata, Hiroyuki
2016-05-01
We study whether the tachyon mode exists as a physical fluctuation on the 2-brane solution and on the tachyon vacuum solution in cubic open string field theory. Our analysis is based on the Batalin-Vilkovisky formalism. We first construct a set of six string states which corresponds to the set of fields and anti-fields containing the tachyon field. Whether the tachyon field can exist as a physical fluctuation is determined by the 6 × 6 matrix defining the anti-bracket in the present sector. If the matrix is degenerate/non-degenerate, the tachyon field is physical/unphysical. Calculations for the pure-gauge type solutions in the framework of the KBc algebra and using the K ɛ -regularization lead to the expected results. Namely, the matrix for the anti-bracket is degenerate/non-degenerate in the case of the 2-brane/tachyon-vacuum solution. Our analysis is not complete, in particular, in that we have not identified the four-fold degeneracy of tachyon fluctuation on the 2-brane solution, and moreover that the present six states do not satisfy the hermiticity condition.
A Cubic B-Spline Approach for Inter-Transformation Between Potential Field and Gradient Data
Wang, B.; Gao, S. S.
2008-12-01
Traditionally, algorithms involving Fast Fourier Transforms (FFT) are used to calculate gradients from field data and vise versa. Because the popular FFT differentiation algorithms are prone to noise, expensive field campaigns are increasingly utilized to obtain gradient data. In areas with both field and gradient data, transformation facilitates comparison. In areas with only one kind of data, transformation facilitates interpretation by transforming the measured data into another form of data. We advance unified formulae for interpolation, differentiation and integration using cubic B-splines, and propose new space-domain approaches for 2D and 3D transformations from potential field data to potential-field gradient data and vice versa. We also advance spline-based continuation techniques. In the spline-based algorithms, the spacing can be either regular or irregular. Analyses using synthetic and real gravity and magnetic data show that the new algorithms have higher accuracy, are more noise-tolerant and thus provide better insights into understanding the nature of the sources than the traditional FFT techniques.
Energy Technology Data Exchange (ETDEWEB)
Cairo, Laurent [MAPMO/CNRS-Departement de Mathematiques, Universite d' Orleans, 45067 Orleans, Cedex 2 (France); Llibre, Jaume [Departament de Matematiques, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain)
2007-06-15
We classify all the global phase portraits of the cubic polynomial vector fields of Lotka-Volterra type having a rational first integral of degree 2. For such vector fields there are exactly 28 different global phase portraits in the Poincare disc up to a reversal of sense of all orbits.
The structure model of a cubic aperiodic phase ('quasicrystal without forbidden symmetry axes').
Kraposhin, V S; Talis, A L; Thanh Lam, Ha
2008-03-19
A model structure of the aperiodic cubic phase (a cubic quasicrystal) has been constructed as a periodical packing of hierarchical octahedral clusters which were composed of truncated tetrahedra (Friauf-Laves polyhedra) and chains of Frank-Kasper polyhedra with 14 vertices. The construction of the hierarchical model for the cubic aperiodic phase became possible due to the discovery of a new space subdivision with equal edges and with vertices belonging to two orbits of the space group Fm3m. The subdivision is characterized by unique values and unique relations between the coordinates of the starting points of two orbits. Calculated x-ray diffraction patterns for the proposed hierarchical model are in qualitative agreement with published experimental x-ray patterns for aperiodical phases observed in melt-quenched Mg-Al and Fe-Nb-B-Si alloys.
Improvement of energy model based on cubic interpolation curve
Institute of Scientific and Technical Information of China (English)
Li Peipei; Li Xuemei; and Wei Yu
2012-01-01
In CAGD and CG, energy model is often used to control the curves and surfaces shape. In curve/surface modeling, we can get fair curve/surface by minimizing the energy of curve/surface. However, our research indicates that in some cases we can＇t get fair curves/surface using the current energy model. So an improved energy model is presented in this paper. Examples are also included to show that fair curves can be obtained using the improved energy model.
Ground-state ordering of the J1-J2 model on the simple cubic and body-centered cubic lattices
Farnell, D. J. J.; Götze, O.; Richter, J.
2016-06-01
The J1-J2 Heisenberg model is a "canonical" model in the field of quantum magnetism in order to study the interplay between frustration and quantum fluctuations as well as quantum phase transitions driven by frustration. Here we apply the coupled cluster method (CCM) to study the spin-half J1-J2 model with antiferromagnetic nearest-neighbor bonds J1>0 and next-nearest-neighbor bonds J2>0 for the simple cubic (sc) and body-centered cubic (bcc) lattices. In particular, we wish to study the ground-state ordering of these systems as a function of the frustration parameter p =z2J2/z1J1 , where z1 (z2) is the number of nearest (next-nearest) neighbors. We wish to determine the positions of the phase transitions using the CCM and we aim to resolve the nature of the phase transition points. We consider the ground-state energy, order parameters, spin-spin correlation functions, as well as the spin stiffness in order to determine the ground-state phase diagrams of these models. We find a direct first-order phase transition at a value of p =0.528 from a state of nearest-neighbor Néel order to next-nearest-neighbor Néel order for the bcc lattice. For the sc lattice the situation is more subtle. CCM results for the energy, the order parameter, the spin-spin correlation functions, and the spin stiffness indicate that there is no direct first-order transition between ground-state phases with magnetic long-range order, rather it is more likely that two phases with antiferromagnetic long range are separated by a narrow region of a spin-liquid-like quantum phase around p =0.55 . Thus the strong frustration present in the J1-J2 Heisenberg model on the sc lattice may open a window for an unconventional quantum ground state in this three-dimensional spin model.
Investigation of Cubic EOS Models for HFO-1234yf Refrigerant Used In Automotive application
Agrawal, Anant; Cornelio, Avi Anthony; Limperich, Dirk
2012-01-01
The need for a consistent and reliable calculation of thermodynamic property of refrigerants has been a topic of research since the past decade. This paper reports a study of various cubic equations of state (EOS) for a refrigerant to be used in automotive applications. Thermodynamic properties of refrigerant 2,3,3,3-tetrafluoropropene (HFO- 1234yf) using three different cubic equations of state, i.e. Peng-Robinson (PR), Yu-Lu (YL) and Guo-Du (GD), are modeled, compared and analyzed. A generi...
KOELINK, MH; DEMUL, FFM; GREVE, J; GRAAFF, R; DASSEL, ACM; AARNOUDSE, JG
1992-01-01
In addition to the static cubic lattice model for photon migration in turbid biological media by Bonner et al. [J. Opt. Soc. Am. A 4, 423-432 (1987)], a dynamic method is presented to calculate the average absolute Doppler shift as a function of the distance between the point of injection of photons
Generalized Additive Models, Cubic Splines and Penalized Likelihood.
1987-05-22
in case control studies ). All models in the table include dummy variable to account for the matching. The first 3 lines of the table indicate that OA...Ausoc. Breslow, N. and Day, N. (1980). Statistical methods in cancer research, volume 1- the analysis of case - control studies . International agency
Gravitational cubic interactions for a simple mixed-symmetry gauge field in AdS and flat backgrounds
Energy Technology Data Exchange (ETDEWEB)
Boulanger, Nicolas [Service de Mecanique et Gravitation, Universite de Mons-UMONS, 20 Place du Parc, 7000 Mons (Belgium); Skvortsov, E D [P. N. Lebedev Physical Institute, Leninsky Prospect 53, 119991 Moscow (Russian Federation); Zinoviev, Yu M, E-mail: nicolas.boulanger@umons.ac.be, E-mail: skvortsov@lpi.ru, E-mail: Yurii.Zinoviev@ihep.ru [Institute for High Energy Physics Protvino, Moscow Region 142280 (Russian Federation)
2011-10-14
Cubic interactions between the simplest mixed-symmetry gauge field and gravity are constructed in anti-de Sitter (AdS) and flat backgrounds. Non-Abelian cubic interactions are obtained in AdS following various perturbative methods including the Fradkin-Vasiliev construction, with and without Stueckelberg fields. The action that features the maximal number of Stueckelberg fields can be considered in the flat limit without loss of physical degrees of freedom. The resulting interactions in flat space are compared with a classification of vertices obtained via the antifield cohomological perturbative method. It is shown that the gauge algebra becomes Abelian in the flat limit, in contrast to what happens for totally symmetric gauge fields in AdS. (paper)
An assessment of CSIRO Conformal Cubic Atmospheric Model simulations over Sri Lanka
Thevakaran, A.; McGregor, J. L.; Katzfey, J.; Hoffmann, P.; Suppiah, R.; Sonnadara, D. U. J.
2016-03-01
In this study, we present an assessment of the Conformal Cubic Atmospheric Model (CCAM) 50 km simulations forced by the sea surface temperature and sea ice concentration of six global climate models (GCMs) (ACCESS1-0, CCSM4, GFDL-CM3, NorESM, MPI-ESM and CNRM-CM5) from the Coupled Model Inter-comparison Project Phase 5 (CMIP5) over South Asia, centred on Sri Lanka. The model simulations were compared with the data provided by the Asian Precipitation Highly Resolved Observational Data Integration towards Evaluation of Water Resource (APHRODITE) project and ERA-Interim from the European Centre for Medium range Weather Forecast (ECMWF) over a broad region centred on Sri Lanka. This broad region includes South Asia and northern Indian Ocean. Statistical measures such as pattern correlations, mean biases and root mean square errors were calculated separately for the four seasons. Results based on statistical tests indicate that the current CCAM simulations capture the spatial patterns of 10 m wind speed, mean sea level pressure, temperature and rainfall over a broad region over South Asia fairly well. The annual cycles of temperature and rainfall were also compared against observations over the northern and southern regions of Sri Lanka by taking the field average of each model and the observed data. The characteristics of the observed annual variations of rainfall and temperature over the smaller domains are not very well captured by the CCAM simulations. There are differences in the magnitudes of the temperature and rainfall in the six member CCAM simulations. Comparatively, the two CCAM simulations CNRM-CM5 and GFDL-CM3 show slightly better agreement over the Sri Lankan region.
Modeling of type-2 fuzzy cubic B-spline surface for flood data problem in Malaysia
Bidin, Mohd Syafiq; Wahab, Abd. Fatah
2017-08-01
Malaysia possesses a low and sloping land areas which may cause flood. The flood phenomenon can be analyzed if the surface data of the study area can be modeled by geometric modeling. Type-2 fuzzy data for the flood data is defined using type-2 fuzzy set theory in order to solve the uncertainty of complex data. Then, cubic B-spline surface function is used to produce a smooth surface. Three main processes are carried out to find a solution to crisp type-2 fuzzy data which is fuzzification (α-cut operation), type-reduction and defuzzification. Upon conducting these processes, Type-2 Fuzzy Cubic B-Spline Surface Model is applied to visualize the surface data of the flood areas that are complex uncertainty.
Xu, J L
2002-01-01
We assume that the u quarks and the d quarks constitute a body center cubic quark lattice in the vacuum. Using energy band theory, we deduce an excited quark spectrum (from the quark lattice). Using the accompanying excitation concept, we deduce a baryon spectrum (including S, C, b, I, Q, and mass) from the quark spectrum. With a phenomenological binding energy formula, we deduce a meson spectrum (including S, C, b, I, Q, and mass) from the quark spectrum. The baryon and meson spectra agree well with experimental results. The BCC Quark Model predicts many new quarks (u'(3), d'(6)), baryons ($\\Lambda^0(4280)$, $\\Lambda_{C}^{+}(6600)$, $\\Lambda_{b}^{0}(9960))$, and mesons (K(3597), D(5996), B(9504), $\\eta(5926)$, $\\Upsilon(17805)$, T(1603) with I=2). The quarks u'(3) and d'(6) and the meson T(1603) have already been discovered.
Numerical modelling of odour dispersion around a cubical obstacle using large eddy simulation.
Dourado, Harerton Oliveira; Santos, Jane Meri; Reis, Neyval C; Mavroidis, Ilias
2012-01-01
In the present work two different large eddy simulation (LES) approaches, namely the Dynamic Smagorinsky model and the Wale model, are used to simulate the air flow and pollutant dispersion around a cubical obstacle. Results are compared with wind tunnel data (WT) and with results from the Smagorinsky LES model. Overall agreement was good between the different LES approaches and the WT results, both for the mean and fluctuating flow and concentration patterns. LES models can provide good estimates of concentration fluctuation intensity and enable the calculation of the intermittency factor. The model results indicate that LES is a viable tool for odour impact assessment.
Influence of spin-orbit interactions on the cubic crystal-field states of the d4 system*
Radwanski, R. J.; Ropka, Z.
2002-01-01
It has been shown that for the highly-correlated d4 electronic system the spin-orbit interactions produce, even in case of the cubic crystal-field interactions, a singlet ground state. Its magnetic moment grows rapidly with the applied magnetic field approaching 4 uB for the Eg state, but only 3 uB for the T2g state. The applicability of the present results to the Mn3+ ion in LaMnO3 is discussed. Keywords: crystal-field, spin-orbit, orbital moment. PACS: 71.70.E, 75.10.D
Gonzales, Matthew J; Sturgeon, Gregory; Krishnamurthy, Adarsh; Hake, Johan; Jonas, René; Stark, Paul; Rappel, Wouter-Jan; Narayan, Sanjiv M; Zhang, Yongjie; Segars, W Paul; McCulloch, Andrew D
2013-07-01
High-order cubic Hermite finite elements have been valuable in modeling cardiac geometry, fiber orientations, biomechanics, and electrophysiology, but their use in solving three-dimensional problems has been limited to ventricular models with simple topologies. Here, we utilized a subdivision surface scheme and derived a generalization of the "local-to-global" derivative mapping scheme of cubic Hermite finite elements to construct bicubic and tricubic Hermite models of the human atria with extraordinary vertices from computed tomography images of a patient with atrial fibrillation. To an accuracy of 0.6 mm, we were able to capture the left atrial geometry with only 142 bicubic Hermite finite elements, and the right atrial geometry with only 90. The left and right atrial bicubic Hermite meshes were G1 continuous everywhere except in the one-neighborhood of extraordinary vertices, where the mean dot products of normals at adjacent elements were 0.928 and 0.925. We also constructed two biatrial tricubic Hermite models and defined fiber orientation fields in agreement with diagrammatic data from the literature using only 42 angle parameters. The meshes all have good quality metrics, uniform element sizes, and elements with aspect ratios near unity, and are shared with the public. These new methods will allow for more compact and efficient patient-specific models of human atrial and whole heart physiology. Copyright © 2013 Elsevier B.V. All rights reserved.
Cubic constraints for the resolvents of the ABJM matrix model and its cousins
Itoyama, Hiroshi; Suyama, Takao; Yoshioka, Reiji
2016-01-01
A set of Schwinger-Dyson equations forming constraints for at most three resolvent functions are considered for a class of Chern-Simons matter matrix models with two nodes labelled by a non-vanishing number $n$. The two cases $n=2$ and $n= -2$ label respectively the ABJM matrix model, which is the hyperbolic lift of the affine $A_1^{(1)}$ quiver matrix model, and the lens space matrix model. In the planar limit, we derive two cubic loop equations for the two planar resolvents. One of these reduces to the quadratic one when $n = \\pm 2$.
Analytic cubic and quartic force fields using density-functional theory
Energy Technology Data Exchange (ETDEWEB)
Ringholm, Magnus; Gao, Bin; Thorvaldsen, Andreas J.; Ruud, Kenneth [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromsø—The Arctic University of Norway, 9037 Tromsø (Norway); Jonsson, Dan [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromsø—The Arctic University of Norway, 9037 Tromsø (Norway); High Performance Computing Group, University of Tromsø—The Arctic University of Norway, 9037 Tromsø (Norway); Bast, Radovan [Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, AlbaNova University Center, S-10691 Stockholm, Sweden and PDC Center for High Performance Computing, Royal Institute of Technology, S-10044 Stockholm (Sweden); Ekström, Ulf; Helgaker, Trygve [Center for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo (Norway)
2014-01-21
We present the first analytic implementation of cubic and quartic force constants at the level of Kohn–Sham density-functional theory. The implementation is based on an open-ended formalism for the evaluation of energy derivatives in an atomic-orbital basis. The implementation relies on the availability of open-ended codes for evaluation of one- and two-electron integrals differentiated with respect to nuclear displacements as well as automatic differentiation of the exchange–correlation kernels. We use generalized second-order vibrational perturbation theory to calculate the fundamental frequencies of methane, ethane, benzene, and aniline, comparing B3LYP, BLYP, and Hartree–Fock results. The Hartree–Fock anharmonic corrections agree well with the B3LYP corrections when calculated at the B3LYP geometry and from B3LYP normal coordinates, suggesting that the inclusion of electron correlation is not essential for the reliable calculation of cubic and quartic force constants.
Directory of Open Access Journals (Sweden)
J.-M. Caillol
2013-01-01
Full Text Available We establish the critical line of the one-component Φ4 (or Landau-Ginzburg model on a simple four dimensional cubic lattice. Our study is performed in the framework of the non-perturbative renormalization group in the local potential approximation with a soft infra-red regulator. The transition is found to be of second order even in the Gaussian limit where first order would be expected according to some recent theoretical predictions.
On intrinsic time measure in the modeling of cyclic behavior of a Nitinol cubic block
Chiroiu, Veturia; Florinel Ionescu, Marius; Sireteanu, Tudor; Ioan, Rodica; Munteanu, Ligia
2015-03-01
In this paper, the cyclic behavior of a superelastic-plastic nitinol cubic block is described by using the Bouc-Wen model coupled to an intrinsic time measure other than clock time, which governs the behavior of the materials. As a consequence, the thermodynamic admissibility of the Bouc-Wen model is provided by the endochronic theory of plasticity. The role of the intrinsic time measure is described by capturing the stiffness and strength degradation and the opposite phenomena. Such behavior is due to the permanent-strain addition of residual martensite and alterations in the properties of the texture during phase transformation.
Non-Born-Oppenheimer self-consistent field calculations with cubic scaling
Energy Technology Data Exchange (ETDEWEB)
Moncada, Felix, E-mail: areyesv@unal.edu.co [Departamento de Quimica, Universidad Nacional de Colombia, Av. Cra. 30 45-03, Bogota (Colombia); Posada, Edwin [Departamento de Quimica, Universidad Nacional de Colombia, Av. Cra. 30 45-03, Bogota (Colombia); Flores-Moreno, Roberto [Departamento de Quimica, Universidad de Guadalajara, Blvd. Marcelino Garcia Barragan 1421, Guadalajara Jal., C.P. 44430 (Mexico); Reyes, Andres [Departamento de Quimica, Universidad Nacional de Colombia, Av. Cra. 30 45-03, Bogota (Colombia)
2012-05-25
Highlights: Black-Right-Pointing-Pointer It is possible to perform cubic-scaling Non-Born-Oppenheimer calculations. Black-Right-Pointing-Pointer The errors introduced by the approximations used in this methodology are small. Black-Right-Pointing-Pointer This method makes possible calculations of molecules with more than a hundred atoms. - Abstract: An efficient nuclear molecular orbital methodology is presented. This approach combines an auxiliary density functional theory for electrons (ADFT) and a localized Hartree product (LHP) representation for the nuclear wave function. A series of test calculations conducted on small molecules exposed that energy and geometry errors introduced by the use of ADFT and LHP approximations are small and comparable to those obtained by the use of electronic ADFT. In addition, sample calculations performed on (HF){sub n} chains disclosed that the combined ADFT/LHP approach scales cubically with system size (n) as opposed to the quartic scaling of Hartree-Fock/LHP or DFT/LHP methods. Even for medium size molecules the improved scaling of the ADFT/LHP approach resulted in speedups of at least 5x with respect to Hartree-Fock/LHP calculations. The ADFT/LHP method opens up the possibility of studying nuclear quantum effects on large size systems that otherwise would be impractical.
Research on cubic polynomial acceleration and deceleration control model for high speed NC machining
Institute of Scientific and Technical Information of China (English)
Hong-bin LENG; Yi-jie WU; Xiao-hong PAN
2008-01-01
To satisfy the need of high speed NC (numerical control) machining, an acceleration and deceleration (aec/dec) control model is proposed, and the speed curve is also constructed by the cubic polynomial. The proposed control model provides continuity of acceleration, which avoids the intense vibration in high speed NC machining. Based on the discrete characteristic of the data sampling interpolation, the acc/dec control discrete mathematical model is also set up and the discrete expression of the theoretical deceleration length is obtained furthermore. Aiming at the question of hardly predetermining the deceleration point in acc/dec control before interpolation, the adaptive acc/dec control algorithm is deduced from the expressions of the theoretical deceleration length. The experimental result proves that the acc/dec control model has the characteristic of easy implementation, stable movement and low impact. The model has been applied in multi-axes high speed micro fabrication machining successfully.
A probabilistic model of the electron transport in films of nanocrystals arranged in a cubic lattice
Energy Technology Data Exchange (ETDEWEB)
Kriegel, Ilka [Department of Nanochemistry, Istituto Italiano di Tecnologia (IIT), via Morego, 30, 16163 Genova (Italy); Scotognella, Francesco, E-mail: francesco.scotognella@polimi.it [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia, Via Giovanni Pascoli, 70/3, 20133 Milan (Italy)
2016-08-01
The fabrication of nanocrystal (NC) films, starting from colloidal dispersion, is a very attractive topic in condensed matter physics community. NC films can be employed for transistors, light emitting diodes, lasers, and solar cells. For this reason the understanding of the film conductivity is of major importance. In this paper we describe a probabilistic model that allows the prediction of the conductivity of NC films, in this case of a cubic lattice of Lead Selenide or Cadmium Selenide NCs. The model is based on the hopping probability between NCs. The results are compared to experimental data reported in literature. - Highlights: • Colloidal nanocrystal (NC) film conductivity is a topic of major importance. • We present a probabilistic model to predict the electron conductivity in NC films. • The model is based on the hopping probability between NCs. • We found a good agreement between the model and data reported in literature.
A cubic matrix-fracture geometry model for radial tracer flow in naturally fractured reservoirs
Energy Technology Data Exchange (ETDEWEB)
Jetzabeth Ramirez-Sabag; Fernando Samaniego V.
1992-01-01
This study presents a general solution for the radial flow of tracers in naturally fractured reservoirs, with cubic blocks matrix-fracture geometry. Continuous and finite step injection of chemical and radioactive tracers are considered. The reservoir is treated as being composed of two regions: a mobile where dispersion and convection take place and a stagnant where only diffusion and adsorption are allowed. Radioactive decay is considered in both regions. The model of this study is thoroughly compared under proper simplified conditions to those previously presented in the literature. The coupled matrix to fracture solution in the Laplace space is numerically inverted by means of the Crump algorithm. A detailed validation of the model with respect to solutions previously presented and/or simplified physical conditions solutions (i.e., homogeneous case) or limit solutions (i.e., naturally fractured nearly homogeneous) was carried out. The influence of the three of the main dimensionless parameters that enter into the solution was carefully investigated. A comparison of results for three different naturally fractured systems, vertical fractures (linear flow), horizontal fractures (radial flow) and the cubic geometry model of this study, is presented.
A Finite Element Cable Model and Its Applications Based on the Cubic Spline Curve
Institute of Scientific and Technical Information of China (English)
方子帆; 贺青松; 向兵飞; 肖化攀; 何孔德; 杜义贤
2013-01-01
For accurate prediction of the deformation of cable in the towed system, a new finite element model is presented that provides a representation of both the bending and torsional effects. In this paper, the cubic spline interpolation function is applied as the trial solution. By using a weighted residual approach, the discretized motion equations for the new finite element model are developed. The model is calculated with the computation program complier by Matlab. Several numerical examples are presented to illustrate the numerical schemes. The results of numerical simulation are stable and valid, and consistent with the mechanical properties of the cable. The model can be applied to kinematics analysis and the design of ocean cable, such as mooring lines, towing, and ROV umbilical cables.
Quantum disordered insulating phase in the frustrated cubic-lattice Hubbard model
Laubach, Manuel; Joshi, Darshan G.; Reuther, Johannes; Thomale, Ronny; Vojta, Matthias; Rachel, Stephan
2016-01-01
In the quest for quantum spin liquids in three spatial dimensions (3D), we study the half-filled Hubbard model on the simple cubic lattice with hopping processes up to third neighbors. Employing the variational cluster approach (VCA), we determine the zero-temperature phase diagram: In addition to a paramagnetic metal at small interaction strength U and various antiferromagnetic insulators at large U , we find an intermediate-U antiferromagnetic metal. Most interestingly, we also identify a nonmagnetic insulating region, extending from intermediate to strong U . Using VCA results in the large-U limit, we establish the phase diagram of the corresponding J1-J2-J3 Heisenberg model. This is qualitatively confirmed—including the nonmagnetic region—using spin-wave theory. Further analysis reveals a striking similarity to the behavior of the J1-J2 square-lattice Heisenberg model, suggesting that the nonmagnetic region may host a 3D spin-liquid phase.
Topological Expansion in the Complex Cubic Log-Gas Model: One-Cut Case
Bleher, Pavel; Deaño, Alfredo; Yattselev, Maxim
2017-02-01
We prove the topological expansion for the cubic log-gas partition function Z_N(t)= int _Γ \\cdots int _Γ prod _{1≤jcomplex parameter and Γ is an unbounded contour on the complex plane extending from e^{π i}∞ to e^{π i/3}∞. The complex cubic log-gas model exhibits two phase regions on the complex t-plane, with one cut and two cuts, separated by analytic critical arcs of the two types of phase transition: split of a cut and birth of a cut. The common point of the critical arcs is a tricritical point of the Painlevé I type. In the present paper we prove the topological expansion for log Z_N(t) in the one-cut phase region. The proof is based on the Riemann-Hilbert approach to semiclassical asymptotic expansions for the associated orthogonal polynomials and the theory of S-curves and quadratic differentials.
Energy Technology Data Exchange (ETDEWEB)
Buchbinder, I.L. [Tomsk State Pedagogical University, Department of Theoretical Physics, Tomsk (Russian Federation); National Research Tomsk State University, Tomsk (Russian Federation); Snegirev, T.V. [Tomsk State Pedagogical University, Department of Theoretical Physics, Tomsk (Russian Federation); Zinoviev, Yu.M. [Institute for High Energy Physics, Protvino, Moscow Region (Russian Federation)
2014-11-15
We study the interaction of a massive spin-3/2 field with electromagnetic and gravitational fields in the four dimensional AdS space and construct the corresponding cubic vertices. The construction is based on a generalization of Fradkin-Vasiliev formalism, developed for massless higher spin fields, to massive fermionic higher spin fields. The main ingredients of this formalism are the gauge-invariant curvatures. We build such curvatures for the massive theory under consideration and show how the cubic vertices are written in their terms. (orig.)
Critical behavior in the cubic dimer model at nonzero monomer density
Sreejith, G. J.; Powell, Stephen
2014-01-01
We study critical behavior in the classical cubic dimer model (CDM) in the presence of a finite density of monomers. With attractive interactions between parallel dimers, the monomer-free CDM exhibits an unconventional transition from a Coulomb phase to a dimer crystal. Monomers act as charges (or monopoles) in the Coulomb phase and, at nonzero density, lead to a standard Landau-type transition. We use large-scale Monte Carlo simulations to study the system in the neighborhood of the critical point, and find results in agreement with detailed predictions of scaling theory. Going beyond previous studies of the transition in the absence of monomers, we explicitly confirm the distinction between conventional and unconventional criticality, and quantitatively demonstrate the crossover between the two. Our results also provide additional evidence for the theoretical claim that the transition in the CDM belongs in the same universality class as the deconfined quantum critical point in the SU (2) JQ model.
Hoede, C.; Zandvliet, H.J.W.
2008-01-01
In a recent paper Hoede and Zandvliet introduced the concept of gauging on an equation. This enables the simulation of more complex Ising models by the simple quadratic model. The possibility of simulating the simple cubic model was defended by calculating a sequence of approximations to the transit
Estimates of critical quantities from an expansion in mass: Ising model on the simple cubic lattice
Yamada, Hirofumi
2015-01-01
In Ising model on the simple cubic lattice, we describe the inverse temperature $\\beta$ and other quantities relevant for the computation of critical quantities in terms of a dimensionless squared mass $M$. The critical behaviors of those quantities are represented by the linear differential equations with constant coefficients which are related to critical exponents. We estimate the critical temperature and exponents via an expansion in the inverse powers of the mass under the use of $\\delta$-expansion. The critical inverse temperature $\\beta_{c}$ is estimated first in unbiased manner and then critical exponents are also estimated in biased and unbiased self-contained way including $\\omega$, the correction-to-scaling exponent, $\
Energy Technology Data Exchange (ETDEWEB)
Llor, A.; Olejniczak, Z.; Pines, A. [Materials Sciences Division, Lawrence Berkeley Laboratory, and Department of Chemistry, University of California, Berkeley, California 94720 (United States)
1995-09-08
We present a special case of the theory of coherent isotropic averaging in zero-field NMR, given in part I of this work. In a zero external field, combinations of the magnetic-field pulses restricted to {pi}/2 rotations along the three coordinate axes can selectively average internal spin Hamiltonians while preserving the intrinsic invariance of the spectrum with respect to the sample orientation. Compared with the general case, the limits of the allowed scaling factors of first- and second-rank interactions are slightly reduced. For instance, time reversal is possible for second-rank tensors with a {minus}1/5 scaling factor, instead of {minus}1/4 in general. Finite pulse compensations are analyzed and experimental illustrations are given for two optimum time-reversal sequences. The cubic sequences, though less efficient than the icosahedral sequences, are technically more feasible and may be used in zero-field experiments such as decoupling (by rank or nuclear species), time reversal or multipolar experiments (the zero-field equivalent of multiple-quantum NMR). {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
Ferromagnetism and crystalline electric field effects in cubic UX2Zn20 (X=Co, Rh, Ir)
Bauer, E. D.; Thompson, J. D.; Sarrao, J. L.; Hundley, M. F.
2007-03-01
The physical properties of a new family of cubic UX2Zn20 (X=Co, Rh, Ir) heavy-fermion compounds are presented. Both UCo2Zn20 and URh2Zn20 show peaks in specific heat and magnetic susceptibility at ˜5-10 K suggesting the presence of crystalline electric field (CEF) effects in these materials, i.e., a localized 5f2 configuration of uranium. UIr2Zn20 exhibits a first-order ferromagnetic transition at Tc=2.1 K with a saturation moment μsat=0.4 μB at 2 K indicating itinerant ferromagnetism. All compounds in this series are heavy-fermion materials with enhanced electronic specific heat coefficients γ˜100-450 mJ/mol K2.
Field assisted sintering of dense Al-substituted cubic phase Li7La3Zr2O12 solid electrolytes
Zhang, Yanhua; Chen, Fei; Tu, Rong; Shen, Qiang; Zhang, Lianmeng
2014-12-01
High performance lithium ion conducting Li7La3Zr2O12 solid electrolytes are prepared for the first time by field assisted sintering technology (FAST). The effect of sintering temperature on the phase compositions, microstructure and Li ionic conductivity is systematically investigated. The results show that pure cubic phase LLZO can be obtained at a range of temperatures from 1100 to 1180 °C for no more than 10 min. For the sample sintered at 1150 °C, a maximum relative density of 99.8% with a total ionic conductivity as high as 5.7 × 10-4 S cm-1 are obtained at room temperature. This value is the highest among the present research. Compared with the traditional preparation methods, the current FAST is very promising to obtain high performance LLZO for its advantages of very short sintering time, a single preparation step of reaction-densification processing, and relatively lower sintering temperature.
Orthogonal polynomials in the normal matrix model with a cubic potential
Bleher, Pavel M
2011-01-01
We consider the normal matrix model with a cubic potential. The model is ill-defined, and in order to reguralize it, Elbau and Felder introduced a model with a cut-off and corresponding system of orthogonal polynomials with respect to a varying exponential weight on the cut-off region on the complex plane. In the present paper we show how to define orthogonal polynomials on a specially chosen system of infinite contours on the complex plane, without any cut-off, which satisfy the same recurrence algebraic identity that is asymptotically valid for the orthogonal polynomials of Elbau and Felder. The main goal of this paper is to develop the Riemann-Hilbert (RH) approach to the orthogonal polynomials under consideration and to obtain their asymptotic behavior on the complex plane as the degree $n$ of the polynomial goes to infinity. As the first step in the RH approach, we introduce an auxiliary vector equilibrium problem for a pair of measures $(\\mu_1,\\mu_2)$ on the complex plane. We then formulate a $3\\times 3...
A singular one-parameter family of solutions in cubic superstring field theory
Arroyo, E. Aldo
2016-05-01
Performing a gauge transformation of a simple identity-like solution of superstring field theory, we construct a one-parameter family of solutions, and by evaluating the energy associated to this family, we show that for most of the values of the parameter the solution represents the tachyon vacuum, except for two isolated singular points where the solution becomes the perturbative vacuum and the half brane solution.
Babaev, A. B.; Murtazaev, A. K.
2017-03-01
Slightly diluted magnetic systems described by the disordered three-dimensional Potts model with the number of spin states q = 3 are studied in the case of a simple cubic lattice. The position of the tricritical point in the phase diagram is determined using the histogram Monte Carlo technique.
Deformation twinning in small-sized face-centred cubic single crystals: Experiments and modelling
Liang, Z. Y.; Huang, M. X.
2015-12-01
Small-sized crystals generally show deformation behaviour distinct from their bulk counterparts. In addition to dislocation slip, deformation twinning in small-sized face-centred cubic (FCC) single crystals has been reported to follow a different mechanism which involves coherent emission of partial dislocations on successive { 111 } planes from free surface. The present work employed a twinning-induced plasticity (TWIP) steel with a low stacking fault energy to systematically investigate the twin evolution in small-sized FCC single crystals. Micrometre-sized single crystal pillars of TWIP steel were fabricated by focus ion beam and then strained to different levels by compression experiments. Detailed transmission electron microscopy characterization was carried out to obtain a quantitative evaluation of the deformation twins, which contribute to most of the plastic strain. Emissions of partial dislocations from free surface (surface sources) and pre-existing perfect dislocations inside the pillar (inner sources) are found as the essential processes for the formation of deformation twins. Accordingly, a physically-based model, which integrates source introduction methods and source activation criterions for partial dislocation emission, is developed to quantitatively predict the twin evolution. The model is able to reproduce the experimental twin evolution, in terms of the total twin formation, the twin morphology and the occurrence of twinning burst.
Khajepor, Sorush; Chen, Baixin
2016-01-01
A method is developed to analytically and consistently implement cubic equations of state into the recently proposed multipseudopotential interaction (MPI) scheme in the class of two-phase lattice Boltzmann (LB) models [S. Khajepor, J. Wen, and B. Chen, Phys. Rev. E 91, 023301 (2015)]10.1103/PhysRevE.91.023301. An MPI forcing term is applied to reduce the constraints on the mathematical shape of the thermodynamically consistent pseudopotentials; this allows the parameters of the MPI forces to be determined analytically without the need of curve fitting or trial and error methods. Attraction and repulsion parts of equations of state (EOSs), representing underlying molecular interactions, are modeled by individual pseudopotentials. Four EOSs, van der Waals, Carnahan-Starling, Peng-Robinson, and Soave-Redlich-Kwong, are investigated and the results show that the developed MPI-LB system can satisfactorily recover the thermodynamic states of interest. The phase interface is predicted analytically and controlled via EOS parameters independently and its effect on the vapor-liquid equilibrium system is studied. The scheme is highly stable to very high density ratios and the accuracy of the results can be enhanced by increasing the interface resolution. The MPI drop is evaluated with regard to surface tension, spurious velocities, isotropy, dynamic behavior, and the stability dependence on the relaxation time.
Wang-Landau sampling in face-centered-cubic hydrophobic-hydrophilic lattice model proteins.
Liu, Jingfa; Song, Beibei; Yao, Yonglei; Xue, Yu; Liu, Wenjie; Liu, Zhaoxia
2014-10-01
Finding the global minimum-energy structure is one of the main problems of protein structure prediction. The face-centered-cubic (fcc) hydrophobic-hydrophilic (HP) lattice model can reach high approximation ratios of real protein structures, so the fcc lattice model is a good choice to predict the protein structures. The lacking of an effective global optimization method is the key obstacle in solving this problem. The Wang-Landau sampling method is especially useful for complex systems with a rough energy landscape and has been successfully applied to solving many optimization problems. We apply the improved Wang-Landau (IWL) sampling method, which incorporates the generation of an initial conformation based on the greedy strategy and the neighborhood strategy based on pull moves into the Wang-Landau sampling method to predict the protein structures on the fcc HP lattice model. Unlike conventional Monte Carlo simulations that generate a probability distribution at a given temperature, the Wang-Landau sampling method can estimate the density of states accurately via a random walk, which produces a flat histogram in energy space. We test 12 general benchmark instances on both two-dimensional and three-dimensional (3D) fcc HP lattice models. The lowest energies by the IWL sampling method are as good as or better than those of other methods in the literature for all instances. We then test five sets of larger-scale instances, denoted by the S, R, F90, F180, and CASP target instances on the 3D fcc HP lattice model. The numerical results show that our algorithm performs better than the other five methods in the literature on both the lowest energies and the average lowest energies in all runs. The IWL sampling method turns out to be a powerful tool to study the structure prediction of the fcc HP lattice model proteins.
Influence of a strong magnetic field on paramagnetic fluid's flow in cubical enclosure
Kraszewska, A.; Pyrda, L.; Donizak, J.
2016-10-01
The fluid behaviour in thermo-magnetic convection of paramagnetic fluid in a strong magnetic field was studied. The fluid was 50% volume aqueous solution of glycerol with an addition of gadolinium nitrate hexahydrate (Gd(NO3)3-6H2O). Experimental enclosure - a vessel with aspect ratio (AR=height/width) equal to 1.0 - was heated from the bottom, and cooled from the top. Temperature difference between top and bottom walls was kept constant at ΔT = 5 and 11 [°C]. The magnetic induction was increased stepwise from 1 to 10 [T] and thermocouples placed inside the enclosures measured temperature changes of the fluid. On the basis of temperature measurements, analysis of the fluid flow was performed.
Numerical Modeling of the Stability of Face-Centered Cubic Metals with High Vacancy Concentration
Energy Technology Data Exchange (ETDEWEB)
Brian P. Somerday; M. I. Baskes
1998-12-01
The objective of this research is to assess the possibility of forming an atomically porous structure in a low-density metal, e.g., Al with vacancies up to 0.20/lattice site; and to examine the effects of hydrogen and vacancy concentration on the stability of an atomically porous structure that has been experimentally produced in nickel. The approach involves numerical modeling using the Embedded-Atom Method (EAM). High vacancy concentrations cause the Al lattice to disorder at 300K. In contrast, Ni retains the face-centered-cubic structure at 300K for vacancy concentrations up to 0.15 Vac/lattice site. Unexpectedly, the lattice with 0.15 Vac/lattice site is more stable than the lattice with 0.10 or 0.20 Vac/lattice site. The Ni systems with 0.10 and 0.15 Vac/lattice site exhibit domains consisting of uniform lattice rotations. The Ni lattice with 0.15 Vac/lattice site is more stable with an initial distribution of random vacancies compared to ordered vacancies. The equilibrium lattice structures of Ni a d Al containing vacancies and H are less ordered to structures with vacancies only at 300K.
Crystal field excitations in the cubic compound Ce{sub 3}Rh{sub 4}Sn{sub 13}
Energy Technology Data Exchange (ETDEWEB)
Adroja, D.T. [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom)], E-mail: d.t.adroja@rl.ac.uk; Strydom, A.M. [Department of Physics APK, University of Johannesburg (South Africa); Murani, A.P. [Institut Laue Langevin, F-38042 Grenoble Cedex (France); Kockelmann, W.A. [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); Fraile, A. [Laboratorio de Magnetismo, Dpto de Fisica de Materia Condensada and Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza, 50009 Zaragoza (Spain)
2008-04-01
The recent heat capacity measurements of Ce{sub 3}Rh{sub 4}Sn{sub 13} have revealed a broad peak at 1 K with an entropy of 3R ln(2) per f.u., but no clear sign of any magnetic ordering down to 100 mK. In order to understand this anomalous heat capacity behaviour of Ce{sub 3}Rh{sub 4}Sn{sub 13}, we have carried out low- and high-energy inelastic neutron scattering measurements. Our high-energy studies reveal two well-resolved crystal field (CF) excitations at {approx}9 meV and 38 meV. The observation of two CF excitations in the cubic structure of Ce{sub 3}Rh{sub 4}Sn{sub 13} could be explained on the basis of tetragonal point symmetry of the Ce ions. Interestingly, the low-energy measurements apparently show, or are best described by, a quasi-elastic peak and an inelastic peak at {approx}0.2 meV at 1.5 K, both of Lorentzian shape. We attribute the low-energy peak to Zeeman splitting of the ground state doublet, in the presence of short range magnetic ordering. Further, the low-energy peak explains the observed anomaly in the heat capacity.
Bobrovskij, N. M.; Levashkin, D. G.; Bobrovskij, I. N.; Melnikov, P. A.; Lukyanov, A. A.
2017-01-01
Article is devoted the decision of basing holes machining accuracy problems of automatically replaceable cubical units (carriers) for reconfigurable manufacturing systems with low-waste production (RMS). Results of automatically replaceable units basing holes machining modeling on the basis of the dimensional chains analysis are presented. Influence of machining parameters processing on accuracy spacings on centers between basing apertures is shown. The mathematical model of carriers basing holes machining accuracy is offered.
Universal Reconfiguration of (Hyper-)cubic Robots
Abel, Zachary; Kominers, Scott D.
2008-01-01
We study a simple reconfigurable robot model which has not been previously examined: cubic robots comprised of three-dimensional cubic modules which can slide across each other and rotate about each others' edges. We demonstrate that the cubic robot model is universal, i.e., that an n-module cubic robot can reconfigure itself into any specified n-module configuration. Additionally, we provide an algorithm that efficiently plans and executes cubic robot motion. Our results directly extend to a...
Finite-band solitons in the Kronig-Penney model with the cubic-quintic nonlinearity.
Merhasin, Ilya M; Gisin, Boris V; Driben, Rodislav; Malomed, Boris A
2005-01-01
We present a model combining a periodic array of rectangular potential wells [the Kronig-Penney (KP) potential] and the cubic-quintic (CQ) nonlinearity. A plethora of soliton states is found in the system: fundamental single-humped solitons, symmetric and antisymmetric double-humped ones, three-peak solitons with and without the phase shift pi between the peaks, etc. If the potential profile is shallow, the solitons belong to the semi-infinite gap beneath the band structure of the linear KP model, while finite gaps between the Bloch bands remain empty. However, in contrast with the situation known in the model combining a periodic potential and the self-focusing Kerr nonlinearity, the solitons fill only a finite zone near the top of the semi-infinite gap, which is a consequence of the saturable character of the CQ nonlinearity. If the potential structure is much deeper, then fundamental and double (both symmetric and antisymmetric) solitons with a flat-top shape are found in the finite gaps. Computation of stability eigenvalues for small perturbations and direct simulations show that all the solitons are stable. In the shallow KP potential, the soliton characteristics, in the form of the integral power Q (or width w) versus the propagation constant k, reveal strong bistability, with two and, sometimes, four different solutions found for a given k (the bistability disappears with the increase of the depth of the potential). Disobeying the Vakhitov-Kolokolov criterion, the solution branches with both dQ/dk > 0 and dQ/dk < 0 are stable. The curve Q(k) corresponding to each particular type of the solution (with a given number of local peaks and definite symmetry) ends at a finite maximum value of Q (breathers are found past the end points). The increase of the integral power gives rise to additional peaks in the soliton's shape, each corresponding to a subpulse trapped in a local channel of the KP structure (a beam-splitting property). It is plausible that these
Topological Expansion in the Complex Cubic Log-Gas Model: One-Cut Case
Bleher, Pavel; Deaño, Alfredo; Yattselev, Maxim
2016-09-01
We prove the topological expansion for the cubic log-gas partition function Z_N(t)= int _Γ \\cdots int _Γ prod _{1≤ jtopological expansion for log Z_N(t) in the one-cut phase region. The proof is based on the Riemann-Hilbert approach to semiclassical asymptotic expansions for the associated orthogonal polynomials and the theory of S-curves and quadratic differentials.
Interpolation by two-dimensional cubic convolution
Shi, Jiazheng; Reichenbach, Stephen E.
2003-08-01
This paper presents results of image interpolation with an improved method for two-dimensional cubic convolution. Convolution with a piecewise cubic is one of the most popular methods for image reconstruction, but the traditional approach uses a separable two-dimensional convolution kernel that is based on a one-dimensional derivation. The traditional, separable method is sub-optimal for the usual case of non-separable images. The improved method in this paper implements the most general non-separable, two-dimensional, piecewise-cubic interpolator with constraints for symmetry, continuity, and smoothness. The improved method of two-dimensional cubic convolution has three parameters that can be tuned to yield maximal fidelity for specific scene ensembles characterized by autocorrelation or power-spectrum. This paper illustrates examples for several scene models (a circular disk of parametric size, a square pulse with parametric rotation, and a Markov random field with parametric spatial detail) and actual images -- presenting the optimal parameters and the resulting fidelity for each model. In these examples, improved two-dimensional cubic convolution is superior to several other popular small-kernel interpolation methods.
DEFF Research Database (Denmark)
Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald;
2016-01-01
This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning with co...
Wang, Shuai; Takahashi, Keisuke; Hashimoto, Naoyuki; Isobe, Shigehito; Ohnuki, Somei
2013-01-01
Effect of hydrogen in body-centered cubic iron is explored by using the density function theory. Hydrogen atoms increase the concentration of free electrons in the simulation cell and have bonding interaction with Fe atom. Caused by anisotropic strain components of hydrogen atoms in the tetrahedral sites, elastic interaction for hydrogen with screw dislocation has been found. The dependence of hydrogen-screw dislocation interaction on hydrogen concentration is confirmed by repeated stress rel...
An exact solution on the ferromagnetic face-cubic spin model on a Bethe lattice
Ohanyan, V. R.; Ananikyan, L. N.; Ananikian, N. S.
2007-04-01
The lattice spin model with Q-component discrete spin variables restricted to have orientations orthogonal to the faces of Q-dimensional hypercube is considered on the Bethe lattice, the recursive graph which contains no cycles. The partition function of the model with dipole-dipole and quadrupole-quadrupole interaction for arbitrary planar graph is presented in terms of double graph expansions. The latter is calculated exactly in case of trees. The system of two recurrent relations (RR) which allows to calculate all thermodynamic characteristics of the model is obtained. The correspondence between thermodynamic phases and different types of fixed points of the RR is established. Using the technique of simple iterations the plots of the zero field magnetization and quadrupolar moment are obtained. Analyzing the regions of stability of different types of fixed points of the system of recurrent relations the phase diagrams of the model are plotted. For Q⩽2 the phase diagram of the model is found to have three tricritical points, whereas for Q>2 there are one triple and one tricritical points.
Wiegelmann, Thomas; Petrie, Gordon J. D.; Riley, Pete
2017-09-01
Coronal magnetic field models use photospheric field measurements as boundary condition to model the solar corona. We review in this paper the most common model assumptions, starting from MHD-models, magnetohydrostatics, force-free and finally potential field models. Each model in this list is somewhat less complex than the previous one and makes more restrictive assumptions by neglecting physical effects. The magnetohydrostatic approach neglects time-dependent phenomena and plasma flows, the force-free approach neglects additionally the gradient of the plasma pressure and the gravity force. This leads to the assumption of a vanishing Lorentz force and electric currents are parallel (or anti-parallel) to the magnetic field lines. Finally, the potential field approach neglects also these currents. We outline the main assumptions, benefits and limitations of these models both from a theoretical (how realistic are the models?) and a practical viewpoint (which computer resources to we need?). Finally we address the important problem of noisy and inconsistent photospheric boundary conditions and the possibility of using chromospheric and coronal observations to improve the models.
Directory of Open Access Journals (Sweden)
Kinjal Gandha
2017-05-01
Full Text Available Ferromagnetic Co-doped α-Fe2O3 cubic shaped nanocrystal assemblies (NAs with a high coercivity of 5.5 kOe have been synthesized via a magnetic field (2 kOe assisted hydrothermal process. The X-ray diffraction pattern and Raman spectra of α-Fe2O3 and Co-doped α-Fe2O3 NAs confirms the formation of single-phase α-Fe2O3 with a rhombohedral crystal structure. Electron microscopy analysis depict that the Co-doped α-Fe2O3 NAs synthesized under the influence of the magnetic field are consist of aggregated nanocrystals (∼30 nm and of average assembly size 2 μm. In contrast to the NAs synthesized with no magnetic field, the average NAs size and coercivity of the Co-doped α-Fe2O3 NAs prepared with magnetic field is increased by 1 μm and 1.4 kOe, respectively. The enhanced coercivity could be related to the well-known spin–orbit coupling strength of Co2+ cations and the redistribution of the cations. The size increment indicates that the small ferromagnetic nanocrystals assemble into cubic NAs with increased size in the magnetic field that also lead to the enhanced coercivity.
Cubical sets and the topological topos
DEFF Research Database (Denmark)
Spitters, Bas
2016-01-01
Coquand's cubical set model for homotopy type theory provides the basis for a computational interpretation of the univalence axiom and some higher inductive types, as implemented in the cubical proof assistant. This paper contributes to the understanding of this model. We make three contributions...... show that it can also be a target for cubical realization by showing that Coquand's cubical sets classify the geometric theory of flat distributive lattices. As a side result, we obtain a simplicial realization of a cubical set. 2. Using the internal `interval' in the topos of cubical sets, we...... construct a Moore path model of identity types. 3. We construct a premodel structure internally in the cubical type theory and hence on the fibrant objects in cubical sets....
Two-dimensional cubic convolution.
Reichenbach, Stephen E; Geng, Frank
2003-01-01
The paper develops two-dimensional (2D), nonseparable, piecewise cubic convolution (PCC) for image interpolation. Traditionally, PCC has been implemented based on a one-dimensional (1D) derivation with a separable generalization to two dimensions. However, typical scenes and imaging systems are not separable, so the traditional approach is suboptimal. We develop a closed-form derivation for a two-parameter, 2D PCC kernel with support [-2,2] x [-2,2] that is constrained for continuity, smoothness, symmetry, and flat-field response. Our analyses, using several image models, including Markov random fields, demonstrate that the 2D PCC yields small improvements in interpolation fidelity over the traditional, separable approach. The constraints on the derivation can be relaxed to provide greater flexibility and performance.
Cubic Icosahedra? A Problem in Assigning Symmetry
Lloyd, D. R.
2010-01-01
There is a standard convention that the icosahedral groups are classified separately from the cubic groups, but these two symmetry types have been conflated as "cubic" in some chemistry textbooks. In this note, the connection between cubic and icosahedral symmetries is examined, using a simple pictorial model. It is shown that octahedral and…
Self-Assembled Lipid Cubic Phase and Cubosomes for the Delivery of Aspirin as a Model Drug.
Kulkarni, Chandrashekhar V; Vishwapathi, Vinod Kumar; Quarshie, Abraham; Moinuddin, Zeinab; Page, James; Kendrekar, Pravin; Mashele, Samson S
2017-09-05
Three-dimensionally organized lipid cubic self-assemblies and derived oil-in-water emulsions called "cubosomes" are attractive for various biotechnological applications due to their ability to be loaded with functional molecules and their associated sustained release properties. Here, we employed both of these lipid-based systems for the delivery of a model drug, aspirin, under comparable conditions. Studies were performed by varying drug-to-lipid ratio and the type of release medium, water and phosphate buffer saline (PBS). Release rates were determined using UV-vis spectroscopy, and small-angle X-ray scattering was used to confirm the type of self-assembled nanostructures formed in these lipid systems. The release from the bulk lipid cubic phase was sustained as compared to that of dispersed cubosomes, and the release in PBS was more efficient than in water. The tortuosity of the architecture, length of the diffusion pathway, type of nanostructure, and physicochemical interaction with the release media evidently contribute to these observations. This work is particularly important as it is the first report where both of these nanostructured lipid systems have been studied together under similar conditions. This work provides important insights into understanding and therefore controlling the release behavior of lipid-based drug nanocarriers.
Institute of Scientific and Technical Information of China (English)
Tian Yongliang; Liu Hu; Yin Jiao; Luo Mingqiang; Wu Guanghui
2015-01-01
Simulation-based training is a promising way to train a carrier flight deck crew because of the complex and dangerous working environment. Quantitative evaluation of simulation-based training quality is vital to make simulation-based training practical for aircraft carrier marshalling. This paper develops a personal computer-based aircraft carrier marshalling simulation system and a cave automatic virtual environment (CAVE)-based immersive environment. In order to compare the training effectiveness of simulation-based training and paper-based training, a learning cubic model is proposed and a contrast experiment is carried out as well. The experimental data is ana-lyzed based on a simplified Kirkpatrick’s model. The results show that simulation-based training is better than paper-based training by 26.80%after three rounds of testing, which prove the effective-ness of simulation-based aircraft carrier marshalling training.
DEFF Research Database (Denmark)
Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald;
2016-01-01
This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning...... with coinductive types. We wish to implement GDTT with decidable type-checking, while still supporting non-trivial equality proofs that reason about the extensions of guarded recursive constructions. CTT is a variation of Martin-L\\"of type theory in which the identity type is replaced by abstract paths between...... terms. CTT provides a computational interpretation of functional extensionality, is conjectured to have decidable type checking, and has an implemented type-checker. Our new type theory, called guarded cubical type theory, provides a computational interpretation of extensionality for guarded recursive...
DEFF Research Database (Denmark)
Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald;
2016-01-01
This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning...... with coinductive types. We wish to implement GDTT with decidable type checking, while still supporting non-trivial equality proofs that reason about the extensions of guarded recursive constructions. CTT is a variation of Martin-L\\"of type theory in which the identity type is replaced by abstract paths between...... terms. CTT provides a computational interpretation of functional extensionality, enjoys canonicity for the natural numbers type, and is conjectured to support decidable type-checking. Our new type theory, guarded cubical type theory (GCTT), provides a computational interpretation of extensionality...
Zhang, Peng; Kim, Kyungsoo; Lee, Seungah; Chakkarapani, Suresh Kumar; Fang, Ning; Kang, Seong Ho
2016-09-01
Augmented three-dimensional (3D) subdiffraction-limited resolution of fluorescence-free single-nanoparticles was achieved with wavelength-dependent enhanced dark-field (EDF) illumination and a least-cubic algorithm. Various plasmonic nanoparticles on a glass slide (i.e., gold nanoparticles, GNPs; silver nanoparticles, SNPs; and gold nanorods, GNRs) were imaged and sliced in the z-direction to a thickness of 10 nm. Single-particle images were then compared with simulation data. The 3D coordinates of individual GNP, SNP, and GNR nanoparticles (x, y, z) were resolved by fitting the data with 3D point spread functions using a least-cubic algorithm and collation. Final, 3D super-resolution microscopy (SRM) images were obtained by resolving 3D coordinates and their Cramér-Rao lower bound-based localization precisions in an image space (530 nm × 530 nm × 300 nm) with a specific voxel size (2.5 nm × 2.5 nm × 5 nm). Compared with the commonly used least-square method, the least-cubic method was more useful for finding the center in asymmetric cases (i.e., nanorods) with high precision and accuracy. This novel 3D fluorescence-free SRM technique was successfully applied to resolve the positions of various nanoparticles on glass and gold nanospots (in vitro) as well as in a living single cell (in vivo) with subdiffraction limited resolution in 3D.
Cubical local partial orders on cubically subdivided spaces - Existence and construction
DEFF Research Database (Denmark)
Fajstrup, Lisbeth
2006-01-01
The geometric models of higher dimensional automata (HDA) and Dijkstra's PV-model are cubically subdivided topological spaces with a local partial order. If a cubicalization of a topological space is free of immersed cubic Möbius bands, then there are consistent choices of direction in all cubes...
Cubical local partial orders on cubically subdivided spaces - existence and construction
DEFF Research Database (Denmark)
Fajstrup, Lisbeth
The geometric models of Higher Dimensional Automata and Dijkstra's PV-model are cubically subdivided topological spaces with a local partial order. If a cubicalization of a topological space is free of immersed cubic Möbius bands, then there are consistent choices of direction in all cubes...
Institute of Scientific and Technical Information of China (English)
马俊; 李进龙; 范冬福; 彭昌军; 刘洪来; 胡英
2011-01-01
Combining Peng-Robinson （PR） equation of state （EoS） with an association model derived from shield-sticky method （SSM） by Liu et al., a new cubic-plus-association （CPA） EoS is proposed to describe the ther-modynamic properties of pure ionic liquids （ILs） and their mixtures. The new molecular parameters for 25 ILs are obtained by fitting the experimental density data over a wide temperature and pressure range, and the overall aver-age deviation is 0.22%. The model parameter b for homologous ILs shows a good linear relationship with their mo-lecular mass, so the number of model parameters is reduced effectively. Using one temperature-independent binary adjustable parameter kij, satisfactory correlations of vapor-liquid equilibria （VLE） for binary mixtures of ILs ＋ non-associating solvents and ＋ associating solvents are obtained with the overall average deviation of vapor pressure 2.91% and 7.01%, respectively. In addition, VLE results for ILs ＋ non-associating mixtures from CPA, lattice-fluid （LF） and square-well chain fluids with variable range （SWCF-VR） EoSs are compared.
An exact solution on the ferromagnetic Face-Cubic spin model on a Bethe lattice
Ohanyan, V. R.; Ananikyan, L. N.; Ananikian, N. S.
2006-01-01
The lattice spin model with $Q$--component discrete spin variables restricted to have orientations orthogonal to the faces of $Q$-dimensional hypercube is considered on the Bethe lattice, the recursive graph which contains no cycles. The partition function of the model with dipole--dipole and quadrupole--quadrupole interaction for arbitrary planar graph is presented in terms of double graph expansions. The latter is calculated exactly in case of trees. The system of two recurrent relations wh...
Monte Carlo studies of the cubic lattice mixed-bond Ising model
Santos-Filho, J. B.; Moreno, N. O.; de Albuquerque, D. F.; de Arruda, A. S.
2007-09-01
In this work, we used the Cluster Wolff algorithms to simulate the dynamics of the system. We obtained the thermodynamic quantities such as magnetization and susceptibility. Critical temperatures were estimated at the maximum of the susceptibility and with these values we made the phase diagram, TC versus p (the concentration of magnetic bonds) for different α values, being α the competition parameter. Our results were compared to those obtained by using a new technique in the effective field theory which employs similar probability distribution within the framework of two-site clusters.
DEFF Research Database (Denmark)
Arya, Alay; Liang, Xiaodong; von Solms, Nicolas
2017-01-01
to calculate the asphaltene onset condition during the addition of different n-paraffin precipitants (n-pentane to n-hexadecane). Three parameters per precipitant are fitted to calculate the asphaltene yield during the addition of the precipitant. The results obtained from the model are compared...
El-Mellouhi, Fadwa; Lucero, Melissa J; Scuseria, Gustavo E
2011-01-01
We have calculated the properties of SrTiO3 (STO) using a wide array of density functionals ranging from standard semi-local functionals to modern range-separated hybrids, combined with several basis sets of varying size/quality. We show how these combination's predictive ability varies signi?cantly, both for STO's cubic and antiferrodistortive (AFD) phases, with the greatest variation in functional/basis set e?cacy seen in modeling the AFD phase. The screened hybrid functionals we utilized predict the structural properties of both phases in very good agreement with experiment, especially if used with large (but still computationally tractable) basis sets. The most accurate results presented in this study, namely those from HSE06/modi?ed-def2-TZVP, stand as the most accurate modeling of STO to date when compared to the literature; these results agree well with experimental structural and electronic properties as well as providing insight into the band structure alteration during the phase transition.
Theoretical Strength of Face-Centred-Cubic Single Crystal Copper Based on a Continuum Model
Institute of Scientific and Technical Information of China (English)
LIU Xiao-Ming; LIU Zhan-Li; YOU Xiao-Chuan; NIE Jun-Feng; ZHUANG Zhuo
2009-01-01
The constitutive relation of single crystal copper based on atomistic potential is implemented to capture the nonlinear inter-atomic interactions. Uniaxial loading tests of single crystal copper with inter-atomic potential finite-element model are carried out to determine the corresponding ideal strength using the modified Born stability criteria. Dependence of the ideal strength on the crystallographic orientation is studied, and tension-compression asymmetry in ideal strength is also investigated. The results suggest that asymmetry for yielding strength of nano-materials may result from anisotropic character of crystal instability. Moreover, the results also reveal that the critical resolved shear stress in the direction of slip is not an accurate criterion for the ideal strength since it could not capture the dependence on the loading conditions and hydrostatic stress components for the ideal strength.
Anisotropic cubic curvature couplings
Bailey, Quentin G
2016-01-01
To complement recent work on tests of spacetime symmetry in gravity, cubic curvature couplings are studied using an effective field theory description of spacetime-symmetry breaking. The associated mass dimension 8 coefficients for Lorentz violation studied do not result in any linearized gravity modifications and instead are revealed in the first nonlinear terms in an expansion of spacetime around a flat background. We consider effects on gravitational radiation through the energy loss of a binary system and we study two-body orbital perturbations using the post-Newtonian metric. Some effects depend on the internal structure of the source and test bodies, thereby breaking the Weak Equivalence Principle for self-gravitating bodies. These coefficients can be measured in solar-system tests, while binary-pulsar systems and short-range gravity tests are particularly sensitive.
Energy Technology Data Exchange (ETDEWEB)
Ricardo de Sousa, J. [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-000 Manaus, AM (Brazil); National Institute of Science and Technology for Complex Systems, 3000, Japiim, 69077-000 Manaus, AM (Brazil); Neto, Minos A., E-mail: minos@pq.cnpq.br [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-000 Manaus, AM (Brazil); Padilha, Igor T.; Salmon, Octavio D.R.; Viana, J. Roberto [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-000 Manaus, AM (Brazil)
2013-12-15
We have studied the anisotropic three-dimensional nearest-neighbor Ising model with competitive interactions in an uniform longitudinal magnetic field H. The model consists of ferromagnetic interactions J{sub z}=λ{sub 2}J{sub x} in the x(z) direction and antiferromagnetic interactions J{sub y}=λ{sub 1}J{sub x} in the y direction (Ising superantiferromagnet). For the particular case λ{sub 1}=λ{sub 2}=1 we obtain the phase diagram in the H−T plane, using the framework of the differential operator technique in the effective-field theory with finite cluster of N=4 spins (EFT-4). It was observed first- and second-order transitions in the low and high temperature limits, respectively, with the presence of a tricritical point and a reentrant behavior is observed at low temperature. The critical curve in the classical approach is also obtained and the results are compared.
Higher-spin Interactions from CFT: The Complete Cubic Couplings
Sleight, Charlotte
2016-01-01
In this letter we provide a complete holographic reconstruction of the cubic couplings in the minimal bosonic higher-spin theory in AdS$_{d+1}$. For this purpose we also determine the OPE coefficients of all single-trace conserved currents in the $d$-dimensional free scalar $O\\left(N\\right)$ vector model, and compute the tree-level three-point Witten diagram amplitudes for a generic cubic interaction of higher-spin gauge fields in the metric-like formulation.
Phase Diagrams and Tricritical Behaviour of the Spin-2 Ising Model in a Longitudinal Random Field
Institute of Scientific and Technical Information of China (English)
LIANG Ya-Qiu; WEI Guo-Zhu; ZHANG Qi; SONG Guo-Li
2004-01-01
@@ Within the framework of the effective-field theory with correlations, we study the ferromagnetic spin-2 randomfield Ising model (RFIM) in the presence of a crystal field on honeycomb (z = 3), square (z = 4) and simple cubic (z = 6) lattices. The effects of the crystal field and the longitudinal random field on the phase diagrams are investigated. Some characteristic features of the phase diagrams, such as the tricritical phenomena, reentrant phenomena and existence of two tricritical points, are found.
Kaulakys, B.; Alaburda, M.; Ruseckas, J.
2016-05-01
A well-known fact in the financial markets is the so-called ‘inverse cubic law’ of the cumulative distributions of the long-range memory fluctuations of market indicators such as a number of events of trades, trading volume and the logarithmic price change. We propose the nonlinear stochastic differential equation (SDE) giving both the power-law behavior of the power spectral density and the long-range dependent inverse cubic law of the cumulative distribution. This is achieved using the suggestion that when the market evolves from calm to violent behavior there is a decrease of the delay time of multiplicative feedback of the system in comparison to the driving noise correlation time. This results in a transition from the Itô to the Stratonovich sense of the SDE and yields a long-range memory process.
Cubic Subalgebras and Cubic Closed Ideals of B-algebras
Directory of Open Access Journals (Sweden)
Tapan Senapati
2015-06-01
Full Text Available In this paper, the concept of cubic set to subalgebras, ideals and closed ideals of B-algebras are introduced. Relations among cubic subalgebras with cubic ideals and cubic closed ideals of B-algebras investigated. The homomorphic image and inverse image of cubic subalgebras, ideals are studied and some related properties are investigated. Also, the product of cubic B-algebras are investigated.
Bibhab Kumar Lodh; Ajoy K Das
2015-01-01
This paper will present the large eddy simulation of turbulence modeling for wind flow over a wall mounted 3D cubical model. The LES Smagorinsky scheme is employed for the numerical simulation. The domain for this study is of the size of 60 cm x 30 cm x 30 cm. The 3D cube model is taken of the size of 6 cm x 6 cm x 4 cm. The Reynolds number for the flow in respect of the height of the cube i.e, 4 cm is 5.3x104 . The hexahedral grids are used for the meshing of the flow domain. ...
Cubic Curves, Finite Geometry and Cryptography
Bruen, A A; Wehlau, D L
2011-01-01
Some geometry on non-singular cubic curves, mainly over finite fields, is surveyed. Such a curve has 9,3,1 or 0 points of inflexion, and cubic curves are classified accordingly. The group structure and the possible numbers of rational points are also surveyed. A possible strengthening of the security of elliptic curve cryptography is proposed using a `shared secret' related to the group law. Cubic curves are also used in a new way to construct sets of points having various combinatorial and geometric properties that are of particular interest in finite Desarguesian planes.
Generalized Vaidya spacetime for cubic gravity
Ruan, Shan-Ming
2015-01-01
We present a kind of generalized Vaidya solutions of a new cubic gravity in five dimensions whose field equations in spherically spacetime are always second order like the Lovelock gravity. We also study the thermodynamics of its apparent horizon and get its entropy expression and generalized Misner-Sharp energy. Finally we present the first law and second law hold in this gravity. Although all the results are analogue to those in Lovelock gravity, we in fact introduce the contribution of new cubic term in five dimensions where cubic Lovelock term is just zero.
Hysteresis Loops and Phase Diagrams of the Spin-1 Ising Model in a Transverse Crystal Field
Institute of Scientific and Technical Information of China (English)
S. Bouhou; I. Essaoudi; A. Ainane; M. Saber; J. J. de Miguel; M. Kerouad1
2012-01-01
Within the framework of the effective-Geld theory with a probability distribution technique, which accounts for the self-spin correlation functions, the ferromagnetic spin-l Ising model with a transverse crystal field on honeycomb, square and simple cubic lattices is studied. We have investigated the effect of the transverse crystal field on the phase diagrams, magnetization, hysteresis loops and χz,h of the system. A number of interesting phenomena of the system are discussed.%Within the framework of the effective-field theory with a probability distribution technique,which accounts for the self-spin correlation functions,the ferromagnetic spin-1 Ising model with a transverse crystal field on honeycomb,square and simple cubic lattices is studied.We have investigated the effect of the transverse crystal field on the phase diagrams,magnetization,hysteresis loops and xz,h of the system.A number of interesting phenomena of the system are discussed.
Cubical sets as a classifying topos
DEFF Research Database (Denmark)
Spitters, Bas
Coquand’s cubical set model for homotopy type theory provides the basis for a computational interpretation of the univalence axiom and some higher inductive types, as implemented in the cubical proof assistant. We show that the underlying cube category is the opposite of the Lawvere theory of De...... Morgan algebras. The topos of cubical sets itself classifies the theory of ‘free De Morgan algebras’. This provides us with a topos with an internal ‘interval’. Using this interval we construct a model of type theory following van den Berg and Garner. We are currently investigating the precise relation...
DEFF Research Database (Denmark)
Maia, Filipa Meireles; Tsivintzelis, Ioannis; Rodriguez, Oscar
2012-01-01
-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][NTf2]) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([C4mim][NTf2]). The first step was to study an adequate approach for the determination of pure component parameters for the ionic liquids. The parameters were...... obtained by fitting the predictions of the model to experimental vapour pressure and liquid density data. The parameters provide a good description of both experimental vapour pressures and liquid density, with maximum percentage deviations of respectively 8.9 and 1.3% for [C2mim][NTf2] and 5.7 and 0.......5% for [C4mim][NTf2]. Different sets of pure component parameters for each ionic liquid were considered and their suitability to describe the behaviour of ionic liquids was evaluated by modelling the vapour–liquid equilibria (VLE) of mixtures with CO2 and the liquid–liquid equilibria (LLE) with water...
Phase Diagram and Tricritical Behavior of a Spin-2 Transverse Ising Model in a Random Field
Institute of Scientific and Technical Information of China (English)
LIANG Ya-Qiu; WEI Guo-Zhu; SONG Li-Li; SONG Guo-Li; ZANG Shu-Liang
2004-01-01
The phase diagrams of a spin-2 transverse Ising model with a random field on honeycomb, square, and simple-cubic lattices, respectively, are investigated within the framework of an effective-field theory with correlations.We find the behavior of the tricritical point and the reentrant phenomenon for the system with any coordination number z, when the applied random field is bimodal. The behavior of the tricritical point is also examined as a function of applied transverse field. The reentrant phenomenon comes from the competition between the transverse field and the random field.
Vladimirov, Igor; Jak, Eugene
2007-04-28
We study an interacting particle system on the simple cubic lattice satisfying the nearest neighbor exclusion (NNE) which forbids any two nearest sites to be simultaneously occupied. Under the constraint, we develop an edge-to-site reduction of the Bethe-Peierls entropy approximation of the cluster variation method. The resulting NNE-corrected Bragg-Williams approximation is applied to statistical mechanical modeling of a liquid silicate formed by silica and a univalent network modifier, for which we derive the molar Gibbs energy of mixing and enthalpy of mixing and compare the predictions with available thermodynamic data.
Interfacing materials models with fire field models
Energy Technology Data Exchange (ETDEWEB)
Nicolette, V.F.; Tieszen, S.R.; Moya, J.L.
1995-12-01
For flame spread over solid materials, there has traditionally been a large technology gap between fundamental combustion research and the somewhat simplistic approaches used for practical, real-world applications. Recent advances in computational hardware and computational fluid dynamics (CFD)-based software have led to the development of fire field models. These models, when used in conjunction with material burning models, have the potential to bridge the gap between research and application by implementing physics-based engineering models in a transient, multi-dimensional tool. This paper discusses the coupling that is necessary between fire field models and burning material models for the simulation of solid material fires. Fire field models are capable of providing detailed information about the local fire environment. This information serves as an input to the solid material combustion submodel, which subsequently calculates the impact of the fire environment on the material. The response of the solid material (in terms of thermal response, decomposition, charring, and off-gassing) is then fed back into the field model as a source of mass, momentum and energy. The critical parameters which must be passed between the field model and the material burning model have been identified. Many computational issues must be addressed when developing such an interface. Some examples include the ability to track multiple fuels and species, local ignition criteria, and the need to use local grid refinement over the burning material of interest.
Bueno, Pablo; Cano, Pablo A.
2016-11-01
We drastically simplify the problem of linearizing a general higher-order theory of gravity. We reduce it to the evaluation of its Lagrangian on a particular Riemann tensor depending on two parameters, and the computation of two derivatives with respect to one of those parameters. We use our method to construct a D -dimensional cubic theory of gravity which satisfies the following properties: (1) it shares the spectrum of Einstein gravity, i.e., it only propagates a transverse and massless graviton on a maximally symmetric background; (2) it is defined in the same way in general dimensions; (3) it is neither trivial nor topological in four dimensions. Up to cubic order in curvature, the only previously known theories satisfying the first two requirements are the Lovelock ones. We show that, up to cubic order, there exists only one additional theory satisfying requirements (1) and (2). Interestingly, this theory is, along with Einstein gravity, the only one which also satisfies (3).
Hansson, T; Erkintalo, M; Anthony, J; Coen, S; Ricciardi, I; De Rosa, M; Wabnitz, S
2016-01-01
We numerically study, by means of the single envelope equation, the generation of optical frequency combs ranging from the visible to the mid-infrared spectral regions in resonators with quadratic and cubic nonlinearities. Phase-matched quadratic wave-mixing processes among the comb lines can be activated by low-power continuous wave pumping in the near infrared of a radially poled lithium niobate whispering gallery resonator (WGR). We examine both separate and co-existing intra-cavity doubly resonant second-harmonic generation and parametric oscillation processes, and find that modulation instabilities may lead to the formation of coupled comb arrays extending over multiple octaves. In the temporal domain, the frequency combs may correspond to pulse trains, or isolated pulses.
Gravity field modelling and gravimetry
Directory of Open Access Journals (Sweden)
Krynski Jan
2015-12-01
Full Text Available The summary of research activities concerning gravity field modelling and gravimetric works performed in Poland in the period of 2011-2014 is presented. It contains the results of research on geoid modelling in Poland and other countries, evaluation of global geopotential models, determination of temporal variations of the gravity field with the use of data from satellite gravity space missions, absolute gravity surveys for the maintenance and modernization of the gravity control in Poland and overseas, metrological aspects in gravimetry, maintenance of gravimetric calibration baselines, and investigations of the nontidal gravity changes. The bibliography of the related works is given in references.
Stochastic-field cavitation model
Energy Technology Data Exchange (ETDEWEB)
Dumond, J., E-mail: julien.dumond@areva.com [AREVA Nuclear Professional School, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); AREVA GmbH, Erlangen, Paul-Gossen-Strasse 100, D-91052 Erlangen (Germany); Magagnato, F. [Institute of Fluid Mechanics, Karlsruhe Institute of Technology, Kaiserstrasse 12, D-76131 Karlsruhe (Germany); Class, A. [AREVA Nuclear Professional School, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); Institute for Nuclear and Energy Technologies, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany)
2013-07-15
Nonlinear phenomena can often be well described using probability density functions (pdf) and pdf transport models. Traditionally, the simulation of pdf transport requires Monte-Carlo codes based on Lagrangian “particles” or prescribed pdf assumptions including binning techniques. Recently, in the field of combustion, a novel formulation called the stochastic-field method solving pdf transport based on Eulerian fields has been proposed which eliminates the necessity to mix Eulerian and Lagrangian techniques or prescribed pdf assumptions. In the present work, for the first time the stochastic-field method is applied to multi-phase flow and, in particular, to cavitating flow. To validate the proposed stochastic-field cavitation model, two applications are considered. First, sheet cavitation is simulated in a Venturi-type nozzle. The second application is an innovative fluidic diode which exhibits coolant flashing. Agreement with experimental results is obtained for both applications with a fixed set of model constants. The stochastic-field cavitation model captures the wide range of pdf shapes present at different locations.
Stochastic-field cavitation model
Dumond, J.; Magagnato, F.; Class, A.
2013-07-01
Nonlinear phenomena can often be well described using probability density functions (pdf) and pdf transport models. Traditionally, the simulation of pdf transport requires Monte-Carlo codes based on Lagrangian "particles" or prescribed pdf assumptions including binning techniques. Recently, in the field of combustion, a novel formulation called the stochastic-field method solving pdf transport based on Eulerian fields has been proposed which eliminates the necessity to mix Eulerian and Lagrangian techniques or prescribed pdf assumptions. In the present work, for the first time the stochastic-field method is applied to multi-phase flow and, in particular, to cavitating flow. To validate the proposed stochastic-field cavitation model, two applications are considered. First, sheet cavitation is simulated in a Venturi-type nozzle. The second application is an innovative fluidic diode which exhibits coolant flashing. Agreement with experimental results is obtained for both applications with a fixed set of model constants. The stochastic-field cavitation model captures the wide range of pdf shapes present at different locations.
Ozkaya, S. I.; Mattner, J.
1996-06-01
An EXCEL visual basic program is presented for modeling fault drag using cubic splines. The objective of the program is to estimate minimum dip and strike separation using dip measurements in the vicinity of a fault. The program is useful especially for estimating stratigraphic separation in the subsurface environment where only limited structural information is available from dipmeter logs. A modified cubic spline curve fitting procedure is used to model bedding trace within the fault drag zone. The solution procedure is based on the assumption that the dip angle is the same at equal distances away from the fault trace on a cross-section or map projection within the fault drag zone on the same side of the fault. On a cross-section perpendicular to the strike of a fault, the distance between the points of intersection of the fault trace with dragged bed and projection of the undisturbed bed gives half of the minimum dip separation. On a map projection, this distance is equal to half of the strike separation.
Rheology of cubic particles suspended in a Newtonian fluid.
Cwalina, Colin D; Harrison, Kelsey J; Wagner, Norman J
2016-05-18
Many real-world industrial processes involve non-spherical particles suspended in a fluid medium. Knowledge of the flow behavior of these suspensions is essential for optimizing their transport properties and designing processing equipment. In the present work, we explore and report on the rheology of concentrated suspensions of cubic-shaped colloidal particles under steady and dynamic shear flow. These suspensions exhibit a rich non-Newtonian rheology that includes shear thickening and normal stress differences at high shear stresses. Scalings are proposed to connect the material properties of these suspensions of cubic particle to those measured for suspensions of spherical particles. Negative first normal stress differences indicate that lubrication hydrodynamic forces dominate the stress in the shear-thickened state. Accounting for the increased lubrication hydrodynamic interactions between the flat surfaces of the cubic particles allows for a quantitative comparison of the deviatoric stress in the shear-thickened state to that of spherical particles. New semi-empirical models for the viscosity and normal stress difference coefficients are presented for the shear-thickened state. The results of this study indicate that cubic particles offer new and unique opportunities to formulate colloidal dispersions for field-responsive materials.
Primordial non-Gaussianities of gravitational waves in the most general single-field inflation model
Gao, Xian; Yamaguchi, Masahide; Yokoyama, Jun'ichi
2011-01-01
We completely clarify the feature of primordial non-Gaussianities of tensor perturbations in generalized G-inflation, i.e., the most general single-field inflation model with second order field equations. It is shown that the most general cubic action for the tensor perturbation (gravitational wave) $h_{ij}$ is composed only of two contributions, one with two spacial derivatives and the other with one time derivative on each $h_{ij}$. The former is essentially identical to the cubic term that appears in Einstein gravity and predicts a squeezed shape, while the latter newly appears in the presence of the kinetic coupling to the Einstein tensor and predicts an equilateral shape. Thus, only two shapes appear in the graviton bispectrum of the most general single-field inflation model, which could open a new clue to the identification of inflationary gravitational waves in observations of cosmic microwave background anisotropies as well as direct gravitational wave detection experiments.
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.
Moussa, Jonathan E
2014-01-07
The random-phase approximation with second-order screened exchange (RPA+SOSEX) is a model of electron correlation energy with two caveats: its accuracy depends on an arbitrary choice of mean field, and it scales as O(n(5)) operations and O(n(3)) memory for n electrons. We derive a new algorithm that reduces its scaling to O(n(3)) operations and O(n(2)) memory using controlled approximations and a new self-consistent field that approximates Brueckner coupled-cluster doubles theory with RPA+SOSEX, referred to as Brueckner RPA theory. The algorithm comparably reduces the scaling of second-order Mo̸ller-Plesset perturbation theory with smaller cost prefactors than RPA+SOSEX. Within a semiempirical model, we study H2 dissociation to test accuracy and Hn rings to verify scaling.
Energy Technology Data Exchange (ETDEWEB)
Moussa, Jonathan E., E-mail: godotalgorithm@gmail.com [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)
2014-01-07
The random-phase approximation with second-order screened exchange (RPA+SOSEX) is a model of electron correlation energy with two caveats: its accuracy depends on an arbitrary choice of mean field, and it scales as O(n{sup 5}) operations and O(n{sup 3}) memory for n electrons. We derive a new algorithm that reduces its scaling to O(n{sup 3}) operations and O(n{sup 2}) memory using controlled approximations and a new self-consistent field that approximates Brueckner coupled-cluster doubles theory with RPA+SOSEX, referred to as Brueckner RPA theory. The algorithm comparably reduces the scaling of second-order Møller-Plesset perturbation theory with smaller cost prefactors than RPA+SOSEX. Within a semiempirical model, we study H{sub 2} dissociation to test accuracy and H{sub n} rings to verify scaling.
Ising low-temperature polynomials and hard-sphere gases on cubic lattices of general dimension
Butera, P
2015-01-01
We derive and analyze the low-activity and low-density expansions of the pressure for the model of a hard-sphere gas on cubic lattices of general dimension $d$, through the 13th order. These calculations are based on our recent extension to dimension d of the low-temperature expansions for the specific free-energy of the spin-1/2 Ising models subject to a uniform magnetic field on the (hyper-)simple-cubic lattices. Estimates of the model parameters are given also for some other lattices
DEFF Research Database (Denmark)
Herslund, Peter Jørgensen; Thomsen, Kaj; Abildskov, Jens
2013-01-01
The complex fluid phase behaviour, of the binary system comprised of water and tetrahydrofuran (THF) is modelled by use of the cubic-plus-association (CPA) equation of state. A total of seven modelling approaches are analysed, differing only in their way of describing THF and its interactions...... are named Case 2 to Case 7. Case 2 treats THF as non self-associating, but applies a single association site on the THF oxygen atom, that allows for cross-linking with a single water molecule. Case 3 is identical to Case 2 but applies two association sites on THF, allowing for simultaneous cross...... accepting- and two electron donating sites.Cases 6 and 7 are similar to Cases 4 and 5, respectively, however the binary cross-association volume between electron accepting sites on water and electron donating sites on THF is adjusted to match the CPA descriptions with available experimental VLE data...
Twelve-state Potts model in a magnetic field
Kassan-Ogly, F. A.; Filippov, B. N.; Proshkin, A. I.; Zarubin, A. V.
2015-02-01
In this work, we have obtained an exact solution to the one-dimensional modified 12-state Potts model using the Kramers-Wannier transfer matrix with allowance for the exchange interaction between nearest neighbors in an external magnetic field. Analytical expressions have been derived for the heat capacity, magnetization, magnetic susceptibility, magnetic entropy, and magnetocaloric effect as functions of temperature, magnitude and sign of exchange interaction, and the magnitude and direction of the magnetic field. The behavior of all of these parameters has been investigated in detail using numerical methods. The possibility of applying the results obtained to explain the observed magnetic properties of real cubic magnets with a NaCl structure and easy axes oriented along the [110] crystallographic directions has been discussed.
Nagai, Kiyoshi
1985-02-01
The global phase diagrams of the corner cubic anisotropic discrete-spin Heisenberg (CH) model and its site-diluted version (dCH) on a triangular lattice are investigated through the position-space renormalization-group method of the simple Migdal-Kadanoff type. The two models include many simpler models as their subspaces, and the interrelations among these models are elucidated. The five-dimensional (5D) phase diagram of the dCH model is generated from the 3D one of the CH model by introducing 2D site-dilution operation. The structure of the 5D phase diagram and the effect of site dilution on the CH model are conveniently visualized by introducing the concept of paths in the 3D subspace. The path describes the temperature variation provided that the ratios between the interaction parameters in the original CH model are fixed. The resulting phase diagrams of the dCH model exhibit the typical three-phase coexistence of solid, liquid, and gas, and their qualitative interpretations are summarized.
Energy Technology Data Exchange (ETDEWEB)
Nakai, T.; Tanahashi, T. [Keio University, Tokyo (Japan). Faculty of Science and Technology
1996-01-25
In a previous paper, we investigated the natural convection in thermoelectrically conducting fluids in a cubic cavity under a magnetic field applied in the gravitational direction, and complicated fluid phenomena were clarified. Particularly in the case of mercury (Pr=0.025, Gr=3.75{times}10{sup 7}), the numerical results agreed well with the observed experimental results obtained using a thermosensitive liquid crystal sheet. In the present paper, we aim to explain the fundamental behavior of thermoelectrically conducting fluids, and numerically determine the natural convection by considering a different direction for the applied magnetic field. The direction of the applied magnetic field is chosen as either the +x, -y or +z direction (see Fig. 1). The convective inhibitory effect of the Lorentz force increases in the order of the +x, -y and +z-directions. 11 refs., 7 figs., 2 tabs.
Correlation Models for Temperature Fields
North, Gerald R.
2011-05-16
This paper presents derivations of some analytical forms for spatial correlations of evolving random fields governed by a white-noise-driven damped diffusion equation that is the analog of autoregressive order 1 in time and autoregressive order 2 in space. The study considers the two-dimensional plane and the surface of a sphere, both of which have been studied before, but here time is introduced to the problem. Such models have a finite characteristic length (roughly the separation at which the autocorrelation falls to 1/e) and a relaxation time scale. In particular, the characteristic length of a particular temporal Fourier component of the field increases to a finite value as the frequency of the particular component decreases. Some near-analytical formulas are provided for the results. A potential application is to the correlation structure of surface temperature fields and to the estimation of large area averages, depending on how the original datastream is filtered into a distribution of Fourier frequencies (e.g., moving average, low pass, or narrow band). The form of the governing equation is just that of the simple energy balance climate models, which have a long history in climate studies. The physical motivation provided by the derivation from a climate model provides some heuristic appeal to the approach and suggests extensions of the work to nonuniform cases.
Directory of Open Access Journals (Sweden)
Bibhab Kumar Lodh
2015-02-01
Full Text Available This paper will present the large eddy simulation of turbulence modeling for wind flow over a wall mounted 3D cubical model. The LES Smagorinsky scheme is employed for the numerical simulation. The domain for this study is of the size of 60 cm x 30 cm x 30 cm. The 3D cube model is taken of the size of 6 cm x 6 cm x 4 cm. The Reynolds number for the flow in respect of the height of the cube i.e, 4 cm is 5.3x104 . The hexahedral grids are used for the meshing of the flow domain. The results are discussed in terms of various parameters such as velocity profile around the cube and the computational domain, the pressure distribution over the cube, near wall velocity profile and the shear stress distribution and also the result of drag coefficient is verified by neural network time series analysis using MATLAB. In this present study we have used the OpenFoam platform for the computational and numerical analysis. The numerical scheme employed is the combination of the steady state incompressible Newtonian flow model using SIMPLE algorithm followed by the transient model of incompressible Newtonian flow using PISO algorithm. We have observed that there is a constant positive drag coefficient in case of steady state simulation where as there is a negative lift coefficient in the initial run and a very low lift coefficient at the end of the steady state simulation.
CRACK PROBLEM UNDER SHEAR LOADING IN CUBIC QUASICRYSTAL
Institute of Scientific and Technical Information of China (English)
周旺民; 范天佑; 尹姝媛
2003-01-01
The axisymmetric elasticity problem of cubic quasicrystal is reduced to a single higher-order partial differential equation by introducing a displacement function. Based on the work, the analytic solutions of elastic field of cubic quasicrystal with a penny-shaped crack under the shear loading are found, and the stress intensity factor and strain energy release rate are determined.
All unitary cubic curvature gravities in D dimensions
Energy Technology Data Exchange (ETDEWEB)
Sisman, Tahsin Cagri; Guellue, Ibrahim; Tekin, Bayram, E-mail: sisman@metu.edu.tr, E-mail: e075555@metu.edu.tr, E-mail: btekin@metu.edu.tr [Department of Physics, Middle East Technical University, 06531 Ankara (Turkey)
2011-10-07
We construct all the unitary cubic curvature gravity theories built on the contractions of the Riemann tensor in D-dimensional (anti)-de Sitter spacetimes. Our construction is based on finding the equivalent quadratic action for the general cubic curvature theory and imposing ghost and tachyon freedom, which greatly simplifies the highly complicated problem of finding the propagator of cubic curvature theories in constant curvature backgrounds. To carry out the procedure we have also classified all the unitary quadratic models. We use our general results to study the recently found cubic curvature theories using different techniques and the string generated cubic curvature gravity model. We also study the scattering in critical gravity and give its cubic curvature extensions.
Directory of Open Access Journals (Sweden)
Roman G. Burkovsky
2016-10-01
Full Text Available We have analyzed the phonon dispersion curves in the paraelectric phase of a lead hafnate crystal (PbHfO3 by means of two different lattice-dynamical models. Both the rigid-ion model and the shell one provided an acceptable description of the available experimental data. The atomic displacement patterns were qualitatively different for the two models. In the rigid-ion model the motion in the characteristic low-energy flattened transverse acoustic branch contained both lead and hafnium displacements, while for the shell model it corresponded mainly to lead displacements with the small contribution of oxygen displacements. The shell model allows simultaneous description of the phonon dispersion curves and the correct value of the dielectric constant.
Entanglement across a cubic interface in 3+1 dimensions
Devakul, Trithep; Singh, Rajiv R. P.
2014-08-01
We calculate the area, edge, and corner Renyi entanglement entropies in the ground state of the transverse-field Ising model, on a simple-cubic lattice, by high-field and low-field series expansions. We find that while the area term is positive and the line term is negative as required by strong subadditivity, the corner contributions are positive in three dimensions. Analysis of the series suggests that the expansions converge up to the physical critical point from both sides. The leading area-law Renyi entropies match nicely from the high- and low-field expansions at the critical point, forming a sharp cusp there. We calculate the coefficients of the logarithmic divergence associated with the corner entropy and compare them with conformal field theory results with smooth interfaces and find a striking correspondence.
Dislocations via incompatibilities in phase-field models of microstructure evolution
Gröger, R.; Marchand, B.; Lookman, T.
2016-08-01
We develop a phase-field model that describes the elastic distortion of a ferroelastic material with cubic anisotropy due to an arbitrary dislocation network and a uniform external load. The dislocation network is characterized using the Nye tensor and enters the formulation via a set of incompatibility constraints for the internal strain field. The long-range elastic response of the material is obtained by minimization of the free energy that accounts for higher-order terms of the order parameters and symmetry-adapted strain gradients. The influence of dislocations on the microstructure is studied using a static equilibrium analysis of a material without dislocations and with a random array of parallel edge dislocations. A minimal continuum dislocation dynamics is then used to investigate the simultaneous evolution of the network of geometrically necessary dislocations and the internal strain field. The model developed here is directly applicable to single-phase cubic crystals with an arbitrary degree of anisotropy as well as to ferroelastic materials undergoing temperature-driven cubic-to-tetragonal phase transitions.
Stress Intensity of Antiplane Conjugate Cracks in Cubic Quasicrystal
Institute of Scientific and Technical Information of China (English)
ZHANG Lei
2008-01-01
Based on the theory of Muskhelishvili, the general solutions for stress and strain of conjugate cracks in cubic quasicrystal are obtained, with which the stress intensity factors of cubic quasicrystal at crack tips and the stress distribution functions of phonon and phason fields are given. The results show that though phason field is coupled with phonon field by constitutive equations, the stress intensity factors are not coupled with any other factors.
Phase Diagram and Tricritical Behavior of a Spin-2 Transverse Ising Model in aRandom Field
Institute of Scientific and Technical Information of China (English)
LIANGYa-Qiu; WEIGuo-Zhu; SONGLi-Li; SONGGuo-Li; ZANGShu-Liang
2004-01-01
The phase diagrams of a spin-2 transverse Ising model with a random field on honeycomb, square, and simple-cubic lattices, respectively, are investigated within the framework of an effective-field theory with correlations.We find the behavior of the tricritical point and the reentrant phenomenon for the system with any coordination number z, when the applied random field is bimodal. The behavior of the tricritical point is also examined as a function of applied transverse field. The reentrant phenomenon comes from the competition between the transverse field and the random field.
Nightingale, M.P.; Blöte , H.W.J.
1996-01-01
The principle and the efficiency of the Monte Carlo transfer-matrix algorithm are discussed. Enhancements of this algorithm are illustrated by applications to several phase transitions in lattice spin models. We demonstrate how the statistical noise can be reduced considerably by a similarity transf
Nightingale, M.P.; Blöte , H.W.J.
1996-01-01
The principle and the efficiency of the Monte Carlo transfer-matrix algorithm are discussed. Enhancements of this algorithm are illustrated by applications to several phase transitions in lattice spin models. We demonstrate how the statistical noise can be reduced considerably by a similarity
Murtazaev, A. K.; Ramazanov, M. K.; Kurbanova, D. R.; Badiev, M. K.; Abuev, Ya. K.
2017-06-01
The replica Monte Carlo method has been used to investigate the critical behavior of a threedimensional antiferromagnetic Ising model on a body-centered cubic lattice, taking into account interactions of the adjacent behind neighbors. Investigations are carried out for the ratios of the values of exchange interactions behind the nearest and next nearest neighbors k = J 2/ J 1 in the range of k ∈ [0.0, 1.0] with the step Δ k = 0.1. In the framework of the theory of finite-dimensional scaling the static critical indices of heat capacity α, susceptibility γ, of the order parameter β, correlation radius ν, and also the Fisher index η are calculated. It is shown that the universality class of the critical behavior of this model is kept in the interval of k ∈ [0.0, 0.6]. It is established that a nonuniversal critical behavior is observed in the range k ∈ [0.8, 1.0].
Energy Technology Data Exchange (ETDEWEB)
M Ali, M. K., E-mail: majidkhankhan@ymail.com, E-mail: eutoco@gmail.com; Ruslan, M. H., E-mail: majidkhankhan@ymail.com, E-mail: eutoco@gmail.com [Solar Energy Research Institute (SERI), Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor (Malaysia); Muthuvalu, M. S., E-mail: sudaram-@yahoo.com, E-mail: jumat@ums.edu.my; Wong, J., E-mail: sudaram-@yahoo.com, E-mail: jumat@ums.edu.my [Unit Penyelidikan Rumpai Laut (UPRL), Sekolah Sains dan Teknologi, Universiti Malaysia Sabah, 88400 Kota Kinabalu, Sabah (Malaysia); Sulaiman, J., E-mail: ysuhaimi@ums.edu.my, E-mail: hafidzruslan@eng.ukm.my; Yasir, S. Md., E-mail: ysuhaimi@ums.edu.my, E-mail: hafidzruslan@eng.ukm.my [Program Matematik dengan Ekonomi, Sekolah Sains dan Teknologi, Universiti Malaysia Sabah, 88400 Kota Kinabalu, Sabah (Malaysia)
2014-06-19
The solar drying experiment of seaweed using Green V-Roof Hybrid Solar Drier (GVRHSD) was conducted in Semporna, Sabah under the metrological condition in Malaysia. Drying of sample seaweed in GVRHSD reduced the moisture content from about 93.4% to 8.2% in 4 days at average solar radiation of about 600W/m{sup 2} and mass flow rate about 0.5 kg/s. Generally the plots of drying rate need more smoothing compared moisture content data. Special cares is needed at low drying rates and moisture contents. It is shown the cubic spline (CS) have been found to be effective for moisture-time curves. The idea of this method consists of an approximation of data by a CS regression having first and second derivatives. The analytical differentiation of the spline regression permits the determination of instantaneous rate. The method of minimization of the functional of average risk was used successfully to solve the problem. This method permits to obtain the instantaneous rate to be obtained directly from the experimental data. The drying kinetics was fitted with six published exponential thin layer drying models. The models were fitted using the coefficient of determination (R{sup 2}), and root mean square error (RMSE). The modeling of models using raw data tested with the possible of exponential drying method. The result showed that the model from Two Term was found to be the best models describe the drying behavior. Besides that, the drying rate smoothed using CS shows to be effective method for moisture-time curves good estimators as well as for the missing moisture content data of seaweed Kappaphycus Striatum Variety Durian in Solar Dryer under the condition tested.
M Ali, M. K.; Ruslan, M. H.; Muthuvalu, M. S.; Wong, J.; Sulaiman, J.; Yasir, S. Md.
2014-06-01
The solar drying experiment of seaweed using Green V-Roof Hybrid Solar Drier (GVRHSD) was conducted in Semporna, Sabah under the metrological condition in Malaysia. Drying of sample seaweed in GVRHSD reduced the moisture content from about 93.4% to 8.2% in 4 days at average solar radiation of about 600W/m2 and mass flow rate about 0.5 kg/s. Generally the plots of drying rate need more smoothing compared moisture content data. Special cares is needed at low drying rates and moisture contents. It is shown the cubic spline (CS) have been found to be effective for moisture-time curves. The idea of this method consists of an approximation of data by a CS regression having first and second derivatives. The analytical differentiation of the spline regression permits the determination of instantaneous rate. The method of minimization of the functional of average risk was used successfully to solve the problem. This method permits to obtain the instantaneous rate to be obtained directly from the experimental data. The drying kinetics was fitted with six published exponential thin layer drying models. The models were fitted using the coefficient of determination (R2), and root mean square error (RMSE). The modeling of models using raw data tested with the possible of exponential drying method. The result showed that the model from Two Term was found to be the best models describe the drying behavior. Besides that, the drying rate smoothed using CS shows to be effective method for moisture-time curves good estimators as well as for the missing moisture content data of seaweed Kappaphycus Striatum Variety Durian in Solar Dryer under the condition tested.
Energy Technology Data Exchange (ETDEWEB)
Hernandez, Andrew M. [Biomedical Engineering Graduate Group, University of California Davis, Sacramento, California 95817 (United States); Boone, John M., E-mail: john.boone@ucdmc.ucdavis.edu [Departments of Radiology and Biomedical Engineering, Biomedical Engineering Graduate Group, University of California Davis, Sacramento, California 95817 (United States)
2014-04-15
Purpose: Monte Carlo methods were used to generate lightly filtered high resolution x-ray spectra spanning from 20 kV to 640 kV. Methods: X-ray spectra were simulated for a conventional tungsten anode. The Monte Carlo N-Particle eXtended radiation transport code (MCNPX 2.6.0) was used to produce 35 spectra over the tube potential range from 20 kV to 640 kV, and cubic spline interpolation procedures were used to create piecewise polynomials characterizing the photon fluence per energy bin as a function of x-ray tube potential. Using these basis spectra and the cubic spline interpolation, 621 spectra were generated at 1 kV intervals from 20 to 640 kV. The tungsten anode spectral model using interpolating cubic splines (TASMICS) produces minimally filtered (0.8 mm Be) x-ray spectra with 1 keV energy resolution. The TASMICS spectra were compared mathematically with other, previously reported spectra. Results: Using pairedt-test analyses, no statistically significant difference (i.e., p > 0.05) was observed between compared spectra over energy bins above 1% of peak bremsstrahlung fluence. For all energy bins, the correlation of determination (R{sup 2}) demonstrated good correlation for all spectral comparisons. The mean overall difference (MOD) and mean absolute difference (MAD) were computed over energy bins (above 1% of peak bremsstrahlung fluence) and over all the kV permutations compared. MOD and MAD comparisons with previously reported spectra were 2.7% and 9.7%, respectively (TASMIP), 0.1% and 12.0%, respectively [R. Birch and M. Marshall, “Computation of bremsstrahlung x-ray spectra and comparison with spectra measured with a Ge(Li) detector,” Phys. Med. Biol. 24, 505–517 (1979)], 0.4% and 8.1%, respectively (Poludniowski), and 0.4% and 8.1%, respectively (AAPM TG 195). The effective energy of TASMICS spectra with 2.5 mm of added Al filtration ranged from 17 keV (at 20 kV) to 138 keV (at 640 kV); with 0.2 mm of added Cu filtration the effective energy was 9
Freitas, ACD; Cunico, LP; M. Aznar; Guirardello,R.
2013-01-01
Ionic liquids (IL) have been described as novel environmentally benign solvents because of their remarkable characteristics. Numerous applications of these solvents continue to grow at an exponential rate. In this work, high pressure vapor liquid equilibria for 17 different IL + gas binary systems were modeled at different temperatures with Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK) equations of state, combined with the van der Waals mixing rule with two binary interaction parameters (v...
Hasenbusch, M.; Hasenbusch, Martin; Pinn, Klaus
1992-01-01
We compute properties of the interface of the 3-dimensional Ising model for a wide range of temperatures and for interface extensions up to 64 by 64. The interface tension sigma is obtained by integrating the surface energy density over the inverse temperature beta. The surface stiffness coefficient kappa is determined. We also study universal quantities like xi^2 sigma and xi^2 kappa. The behavior of the interfacial width on lattices up to 512 times 512 times 27 is also investigated.
Wang, Zhen; Qiao, Zhijun
2016-07-01
In this paper, the inverse scattering transform associated with a Riemann-Hilbert problem is formulated for the FQXL model: a generalized Camassa-Holm equation m t = /1 2 k 1 [ m ( u 2 - ux 2 ) ] x + /1 2 k 2 ( 2 m u x + m x u ) , m = u - u x x , which was originally included in the work of Fokas [Physica D 87, 145 (1995)] and was recently shown to be integrable in the sense of Lax pair, bi-Hamilton structure, and conservation laws by Qiao, Xia, and Li [e-print arXiv:1205.2028v2 (2012)]. We have discussed the following properties: direct scattering problems and Jost solutions, asymptotical and analytical behavior of Jost solutions, the scattering equations in a Riemann-Hilbert problem, and the multi-soliton solutions of the FQXL model. Then, one-soliton and two-soliton solutions are presented in a parametric form as a special case of multi-soliton solutions.
DEFF Research Database (Denmark)
Breil, Martin Peter; Kontogeorgis, Georgios; Behrens, Paul K.
2011-01-01
density, enthalpy of vaporization, and vapor-phase compressibility factor data. The CPA-HV parameters have been fitted to, among others, experimental vapor compressibility factor data and experimental relative volatility data at different temperature ranges. The purpose of the work was to investigate...... whether the CPA-HV model can describe the vapor−liquid equilibrium for acetic acid−water over a temperature range of 200 K and at the same time represent the behavior of pure acetic acid and acetic acid−water mixtures with respect to enthalpies of vaporization and compressibility factors. It is shown...... that satisfactory results are overall obtained, but if an excellent match is needed over the whole temperature range, then different interaction parameters need to be used at the various temperature ranges....
On the magnetization process and the associated probability in anisotropic cubic crystals
Khedr, D. M.; Aly, Samy H.; Shabara, Reham M.; Yehia, Sherif
2017-05-01
We present a theoretical method to calculate specific magnetic properties, e.g. magnetization curves, magnetic susceptibility and probability landscapes along the [100], [110] and [111] crystallographic directions of a crystal of cubic symmetry. The probability landscape displays the evolution of the most probable angular orientation of the magnetization vector, for selected temperatures and magnetic fields. Our method is based on the premises of classical statistical mechanics. The energy density, used in the partition function, is the sum of magnetic anisotropy and Zeeman energies, however no other energies e.g. elastic or magnetoelastic terms are considered in the present work. Model cubic systems of diverse anisotropies are analyzed first, and subsequently material magnetic systems of cubic symmetry; namely iron, nickel and Cox Fe100-x compounds, are discussed. We highlight a correlation between magnetization curves and the associated probability landscapes. In addition, determination of easiest axes of magnetization, using energy consideration, is done and compared with the results of the present method.
Directory of Open Access Journals (Sweden)
A. C. D. Freitas
2013-03-01
Full Text Available Ionic liquids (IL have been described as novel environmentally benign solvents because of their remarkable characteristics. Numerous applications of these solvents continue to grow at an exponential rate. In this work, high pressure vapor liquid equilibria for 17 different IL + gas binary systems were modeled at different temperatures with Peng-Robinson (PR and Soave-Redlich-Kwong (SRK equations of state, combined with the van der Waals mixing rule with two binary interaction parameters (vdW-2. The experimental data were taken from the literature. The optimum binary interaction parameters were estimated by minimization of an objective function based on the average absolute relative deviation of liquid and vapor phases, using the modified Simplex algorithm. The solubilities of all gases studied in this work decrease as the temperature increases and increase with increasing pressure. The correlated results were highly satisfactory, with average absolute relative deviations of 2.10% and 2.25% for PR-vdW-2 and SRK-vdW-2, respectively.
The Swarm Initial Field Model for the 2014 geomagnetic field
DEFF Research Database (Denmark)
Olsen, Nils; Hulot, Gauthier; Lesur, Vincent;
2015-01-01
Data from the first year of ESA's Swarm constellation mission are used to derive the Swarm Initial Field Model (SIFM), a new model of the Earth's magnetic field and its time variation. In addition to the conventional magnetic field observations provided by each of the three Swarm satellites......, explicit advantage is taken of the constellation aspect by including East-West magnetic intensity gradient information from the lower satellite pair. Along-track differences in magnetic intensity provide further information concerning the North-South gradient. The SIFM static field shows excellent...... agreement (up to at least degree 60) with recent field models derived from CHAMP data, providing an initial validation of the quality of the Swarm magnetic measurements. Use of gradient data improves the determination of both the static field and its secular variation, with the mean misfit for East...
DEFF Research Database (Denmark)
Poulsen, Stefan Othmar; Voorhees, P.W.; Lauridsen, Erik Mejdal
2012-01-01
A phase field model to study the microstructural evolution of a polycrystalline dual-phase material with conserved phase fraction has been implemented, and 2D simulations have been performed. For 2D simulations, the model predicts the cubic growth well-known for diffusion-controlled systems. Some...... interphase boundaries are found to show a persistent non-constant curvature, which seems to be a feature of multi-phase materials. Finally, it is briefly outlined how this model is to be applied to investigate microstructural evolution in duplex steel. © (2012) Trans Tech Publications, Switzerland....
Boudechiche, Noreddine; Yazid, Hynda; Trari, Mohamed; Sadaoui, Zahra
2017-07-05
In this study, the central composite rotatable design (CCRD) was used in the optimization of the operating parameters for the removal of the direct blue 86 (DB86), an anionic dye, because of its hazardous impact on human health and aquatic environment. In addition, DB86 is a recalcitrant and non-biodegradable dye whose presence considerably inhibits photosynthesis. Its removal in aqueous medium was achieved by biosorption onto the novel biosorbent Crataegus azarolus stones (CAS). The parameters like the solution pH, biosorbent dose, initial DB86 concentration, and temperature were studied in the ranges 2-6, 0.8-4 g L(-1), 20-100 mg L(-1), and 10-50 °C, respectively. The significance of the experimental parameters and their interactions was investigated by the Student's t test and p values with 5% error limits using JMP 11.0.0 software. The regression analysis of the experimental data obtained from 31 batch runs provides a cubic model. The optimum conditions obtained for the maximum DB86 elimination from the synthetic solution were found to be pH 2, biosorbent dose of 4 g L(-1), initial DB86 concentration of 20 mg L(-1), and temperature of 10 °C, leading to a theoretical maximum removal of 123%. The experimental data were analyzed by the Langmuir, Freundlich, and Temkin equilibrium models. The Langmuir isotherm gave the best fit with a maximum biosorption capacity of 24.02 mg g(-1). The results of the kinetic study revealed that the biosorption kinetic of DB86 follows a pseudo-second-order model. All results confirmed that CAS are an efficient, economic, and ecological alternative for the treatment of industrial wastewaters loaded with anionic dyes.
Mean-field models and exotic nuclei
Energy Technology Data Exchange (ETDEWEB)
Bender, M.; Buervenich, T.; Maruhn, J.A.; Greiner, W. [Inst. fuer Theoretische Physik, Univ. Frankfurt (Germany); Rutz, K. [Inst. fuer Theoretische Physik, Univ. Frankfurt (Germany)]|[Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Reinhard, P.G. [Inst. fuer Theoretische Physik, Univ. Erlangen (Germany)
1998-06-01
We discuss two widely used nuclear mean-field models, the relativistic mean-field model and the (nonrelativistic) Skyrme-Hartree-Fock model, and their capability to describe exotic nuclei. Test cases are superheavy nuclei and neutron-rich Sn isotopes. New information in this regime helps to fix hitherto loosely determined aspects of the models. (orig.)
The Exact Limit of Some Cubic Towers
DEFF Research Database (Denmark)
Anbar Meidl, Nurdagül; Beelen, Peter; Nguyen, Nhut
2016-01-01
Recently, a new explicit tower of function fields was introduced by Bassa, Beelen, Garcia and Stichtenoth (BBGS). This resulted in currently the best known lower bound for Ihara’s constant in the case of non-prime finite fields. In particular over cubic fields, the tower’s limit is at least as good...... as Zink’s bound; i.e. λ(BBGS/Fq3 ) ≥ 2(q2 - 1)/(q + 2). In this paper, the exact value of λ(BBGS/Fq3 ) is computed. We also settle a question stated by Ihara....
Directory of Open Access Journals (Sweden)
Zhenwei Gan
2017-01-01
Full Text Available Challenged by the increasing complexity of targets and the tense situation of turning losses into profits during the 12th Five-Year Plan, by virtue of technological innovation, Sinopec Southwest Oil & Gas Company proposed the theories of gas exploration in continental clastic rock and marine carbonate rock, and developed the development technologies for reef, channel sandstone and tight sandstone reservoirs. Moreover, it innovatively formed a series of engineering technologies, including intelligent sliding sleeve staged fracturing, blasting–packing–fracturing stimulation, impulse fracturing, and drilling, completion and production technologies for ultra-deep horizontal wells with high sulfur contents. With these innovated theories and improved technologies, great discoveries have been made in the continental clastic rocks and marine carbonate rocks in West Sichuan Basin, the marine shale in South Sichuan Basin, and the marine carbonate rocks in Yuanba area of NE Sichuan Basin, and three 100 billion-m3 class commercial gas reserves zones were discovered. Moreover, two medium- and large-sized gas fields were proved, and three medium- and large-sized gas fields were completely constructed. Both reserves and production reached a new record in history. During the 13th Five-Year Plan, Sinopec Southwest Oil & Gas Company will focus on the exploration and development of deep marine carbonate reservoirs, commercial development of deep shale gas, safe development of gas fields with high sulfur, and enhancement of recovery in mature gas fields. By the end of the 13th Five-Year Plan, it is expected that the annual gas production of (10–12 × 109 m3 will be achieved.
Quantum field theory competitive models
Tolksdorf, Jürgen; Zeidler, Eberhard
2009-01-01
For more than 70 years, quantum field theory (QFT) can be seen as a driving force in the development of theoretical physics. Equally fascinating is the fruitful impact which QFT had in rather remote areas of mathematics. The present book features some of the different approaches, different physically viewpoints and techniques used to make the notion of quantum field theory more precise. For example, the present book contains a discussion including general considerations, stochastic methods, deformation theory and the holographic AdS/CFT correspondence. It also contains a discussion of more recent developments like the use of category theory and topos theoretic methods to describe QFT. The present volume emerged from the 3rd 'Blaubeuren Workshop: Recent Developments in Quantum Field Theory', held in July 2007 at the Max Planck Institute of Mathematics in the Sciences in Leipzig/Germany. All of the contributions are committed to the idea of this workshop series: 'To bring together outstanding experts working in...
The CHAOS-4 geomagnetic field model
DEFF Research Database (Denmark)
Olsen, Nils; Lühr, H.; Finlay, Chris;
2014-01-01
We present CHAOS-4, a new version in the CHAOS model series, which aims to describe the Earth's magnetic field with high spatial and temporal resolution. Terms up to spherical degree of at least n = 85 for the lithospheric field, and up to n = 16 for the time-varying core field are robustly deter...
The CHAOS-4 Geomagnetic Field Model
DEFF Research Database (Denmark)
Olsen, Nils; Finlay, Chris; Lühr, H.
We present CHAOS-4, a new version in the CHAOS model series, which aims at describing the Earth's magnetic field with high spatial resolution (terms up to spherical degree n=90 for the crustal field, and up to n=16 for the time-varying core field are robustly determined) and high temporal resolut...
Alien wavelength modeling tool and field trial
DEFF Research Database (Denmark)
Sambo, N.; Sgambelluri, A.; Secondini, M.
2015-01-01
A modeling tool is presented for pre-FEC BER estimation of PM-QPSK alien wavelength signals. A field trial is demonstrated and used as validation of the tool's correctness. A very close correspondence between the performance of the field trial and the one predicted by the modeling tool has been...
Geostatistical methods applied to field model residuals
DEFF Research Database (Denmark)
Maule, Fox; Mosegaard, K.; Olsen, Nils
consists of measurement errors and unmodelled signal), and is typically assumed to be uncorrelated and Gaussian distributed. We have applied geostatistical methods to analyse the residuals of the Oersted(09d/04) field model [http://www.dsri.dk/Oersted/Field_models/IGRF_2005_candidates/], which is based...
The Coulombic Lattice Potential of Ionic Compounds: The Cubic Perovskites.
Francisco, E.; And Others
1988-01-01
Presents coulombic models representing the particles of a system by point charges interacting through Coulomb's law to explain coulombic lattice potential. Uses rubidium manganese trifluoride as an example of cubic perovskite structure. Discusses the effects on cluster properties. (CW)
Evidence for a bicritical point in the XXZ Heisenberg antiferromagnet on a simple cubic lattice.
Selke, Walter
2011-04-01
The classical Heisenberg antiferromagnet with uniaxial exchange anisotropy (XXZ model) in a field on a simple cubic lattice is studied with the help of extensive Monte Carlo simulations. We analyze, in particular, various staggered susceptibilities and Binder cumulants and present clear evidence for the triple point of the antiferromagnetic, spin-flop, and paramagnetic phases being a bicritical point with Heisenberg symmetry. Results are compared to previous predictions applying various theoretical approaches.
Modelling electricity forward markets by ambit fields
DEFF Research Database (Denmark)
Barndorff-Nielsen, Ole; Fred Espen Benth, Fred Espen; Veraart, Almut
This paper proposes a new modelling framework for electricity forward markets, which is based on ambit fields. The new model can capture many of the stylised facts observed in energy markets. One of the main differences to the traditional models lies in the fact that we do not model the dynamics...
Random-field Ising model on isometric lattices: Ground states and non-Porod scattering
Bupathy, Arunkumar; Banerjee, Varsha; Puri, Sanjay
2016-01-01
We use a computationally efficient graph cut method to obtain ground state morphologies of the random-field Ising model (RFIM) on (i) simple cubic (SC), (ii) body-centered cubic (BCC), and (iii) face-centered cubic (FCC) lattices. We determine the critical disorder strength Δc at zero temperature with high accuracy. For the SC lattice, our estimate (Δc=2.278 ±0.002 ) is consistent with earlier reports. For the BCC and FCC lattices, Δc=3.316 ±0.002 and 5.160 ±0.002 , respectively, which are the most accurate estimates in the literature to date. The small-r behavior of the correlation function exhibits a cusp regime characterized by a cusp exponent α signifying fractal interfaces. In the paramagnetic phase, α =0.5 ±0.01 for all three lattices. In the ferromagnetic phase, the cusp exponent shows small variations due to the lattice structure. Consequently, the interfacial energy Ei(L ) for an interface of size L is significantly different for the three lattices. This has important implications for nonequilibrium properties.
Local atomic structure in cubic stabilized zirconia
Energy Technology Data Exchange (ETDEWEB)
Villella, P.; Conradson, S. D.; Espinosa-Faller, F. J.; Foltyn, S. R.; Sickafus, K. E.; Valdez, J. A.; Degueldre, C. A.
2001-09-01
X-ray-absorption fine structure measurements have been used to elucidate the local atomic structure of quaternary Zr, Y, Er, Ce/U cubic stabilized zirconia. These compounds display more complicated local environments than those reported for simpler binary systems. While the shortest cation-O distances are similar to those found in the binary cubic stabilized compounds, responding to the different sizes of the cations, we have identified large distortions in the first-shell oxygen distribution involving long, 2.8--3.2 {angstrom} cation-O distances that are similar to those found in the amorphous phase of zirconium. The cation-cation distributions are also found to be quite complicated (non-Gaussian) and element specific. The U-near neighbor distances are expanded relative to the Ce ions for which it substitutes, consistent with the larger size of the actinide, and the U-cation distribution is also more complicated. In terms of the effects of this substitution on the other cation sites, the local environment around Y is altered while the Zr and Er local environments remain unchanged. These results point out the importance of collective and correlated interactions between the different pairs of cations and the host lattice that are mediated by the local strain fields generated by the different cations. The presence of pair-specific couplings has not been commonly included in previous analyses and may have implications for the stabilization mechanisms of cubic zirconia.
The special symplectic structure of binary cubics
Slupinski, Marcus
2009-01-01
Let $k$ be a field of characteristic not 2 or 3. Let $V$ be the $k$-space of binary cubic polynomials. The natural symplectic structure on $k^2$ promotes to a symplectic structure $\\omega$ on $V$ and from the natural symplectic action of $\\textrm{Sl}(2,k)$ one obtains the symplectic module $(V,\\omega)$. We give a complete analysis of this symplectic module from the point of view of the associated moment map, its norm square $Q$ (essentially the classical discriminant) and the symplectic gradient of $Q$. Among the results are a symplectic derivation of the Cardano-Tartaglia formulas for the roots of a cubic, detailed parameters for all $\\textrm{Sl}(2,k)$ and $\\textrm{Gl}(2,k)$-orbits, in particular identifying a group structure on the set of $\\textrm{Sl}(2,k)$-orbits of fixed nonzero discriminant, and a purely symplectic generalization of the classical Eisenstein syzygy for the covariants of a binary cubic. Such fine symplectic analysis is due to the special symplectic nature inherited from the ambient excepti...
Butera, P
2000-01-01
Using a renormalized linked-cluster-expansion method, we extend to order $\\beta^{23}$ the high-temperature series for the susceptibility $\\chi$ and the second-moment correlation length $\\xi$ of the spin-1/2 Ising models on the sc and the bcc lattices. A study of these expansions yields updated direct estimates of universal parameters, such as exponents and amplitude ratios, which characterize the critical behavior of $\\chi$ and $\\xi$. Our best estimates for the inverse critical temperatures are $\\beta^{sc}_c=0.221654(1)$ and $\\beta^{bcc}_c=0.1573725(6)$. For the susceptibility exponent we get $\\gamma=1.2375(6)$ and for the correlation length exponent $\
A northern hemisphere geomagnetic field model for the last 14ka
Pavon-Carrasco, Fco Javier; Osete, Maria Luisa; Miquel Torta, Joan; de Santis, Angelo
2013-04-01
In this work, we propose a first regional geomagnetic field model for the Northern Hemisphere based on archaeomagnetic and lava flow data. The regional model, called scha.dif.14k, allows us to analyse the low degree of the geomagnetic field secular variation for the last 14000 years: from 12000 BC to 1900 AD. The inversion process of the declination, inclination and intensity palaeomagnetic data was carried out iteratively, using the spherical cap harmonic analysis (SCHA) up to degree K = 4 in space and penalized cubic B-spline in time with a knot point of 100 years for the whole time interval. Three starting models have been tested: a) A constant axial dipole field, b) a time-dependent axial dipole field and c) a time-dependent inclined dipole field. The last two starting models were estimated by using directly the archaeomagnetic data. These starting models have been perturbed in order to obtain a regional model with a higher spatial and temporal variability. We have compared the model with the recent published palaeosecular variation curves and with the global model for the Holocene: CALS10K.1b. Our model fits reasonably well the different palaeosecular variation curves and improves the prediction of the CALS10K.1b global model.
Phase diagram of the classical Heisenberg model in a trimodal random field distribution
Santos-Filho, A.; Albuquerque, D. F. de; Santos-Filho, J. B.; Batista, T. S. Araujo
2016-11-01
The classical spin 1 / 2 Heisenberg model on a simple cubic lattice, with fluctuating bond interactions between nearest neighbors and in the presence of a random magnetic field, is investigated by effective field theory based on two-spin cluster. The random field is drawn from the asymmetric and anisotropic trimodal probability distribution. The fluctuating bond is extracted from the symmetric and anisotropic bimodal probability. We estimate the transition temperatures, and the phase diagram in the Tc- h, Tc- p and Tc - α planes. We observe that the temperature of the tricritical point decreases with the increase of disorder in exchange interactions until the system ceases to display tricritical behavior. The disorder of the interactions and reentrant phenomena depends on the trimodal distribution of the random field.
Plasmon polaritons in cubic lattices of spherical metallic nanoparticles
Lamowski, Simon; Mariani, Eros; Weick, Guillaume; Pauly, Fabian
2016-01-01
We investigate theoretically plasmon polaritons in cubic lattices of interacting spherical metallic nanoparticles. Dipolar localized surface plasmons on each nanoparticle couple through the near field dipole-dipole interaction and form collective plasmons which extend over the whole metamaterial. Coupling these collective plasmons in turn to photons leads to plasmon polaritons. We derive within a quantum model general semi-analytical expressions to evaluate both plasmon and plasmon-polariton dispersions that fully account for nonlocal effects in the dielectric function of the metamaterial. Within this model, we discuss the influence of different lattice symmetries and predict related polaritonic gaps within the near-infrared to the visible range of the spectrum that depend on wavevector direction and polarization.
Phase Field Modeling Using PetIGA
Vignal, Philippe A.
2013-06-01
Phase field modeling has become a widely used framework in the computational material science community. Its ability to model different problems by defining appropriate phase field parameters and relating it to a free energy functional makes it highly versatile. Thermodynamically consistent partial differential equations can then be generated by assuming dissipative dynamics, and setting up the problem as one of minimizing this free energy. The equations are nonetheless challenging to solve, and having a highly efficient and parallel framework to solve them is necessary. In this work, a brief review on phase field models is given, followed by a short analysis of the Phase Field Crystal Model solved with Isogeometric Analysis us- ing PetIGA. We end with an introduction to a new modeling concept, where free energy functions are built with a periodic equilibrium structure in mind.
A combinatorial wind field model
DEFF Research Database (Denmark)
Soleimanzadeh, Maryam; Wisniewski, Rafal; Sloth, Christoffer
2010-01-01
of ordinary dierential equations (ODE). Considering some assumptions on the ow model (e.g. steadiness), the sys- tem can be approximated by a linear n dimensional system. Partitioning the state space into cells is performed by dening Lyapunov function sets, such that each cell is the region between two...... neighboring level surfaces of Lyapunov functions. The resulting discrete system facilitates a supervisory approach to the control....
A combinatorial wind field model
DEFF Research Database (Denmark)
Soleimanzadeh, Maryam; Wisniewski, Rafal; Sloth, Christoffer
2010-01-01
of ordinary dierential equations (ODE). Considering some assumptions on the ow model (e.g. steadiness), the sys- tem can be approximated by a linear n dimensional system. Partitioning the state space into cells is performed by dening Lyapunov function sets, such that each cell is the region between two...... neighboring level surfaces of Lyapunov functions. The resulting discrete system facilitates a supervisory approach to the control....
Unified Dark Matter Scalar Field Models
Directory of Open Access Journals (Sweden)
Daniele Bertacca
2010-01-01
of a single scalar field accounts for a unified description of the Dark Matter and Dark Energy sectors, dubbed Unified Dark Matter (UDM models. In this framework, we consider the general Lagrangian of -essence, which allows to find solutions around which the scalar field describes the desired mixture of Dark Matter and Dark Energy. We also discuss static and spherically symmetric solutions of Einstein's equations for a scalar field with noncanonical kinetic term, in connection with galactic halo rotation curves.
Interpolating solutions in cubic superstring field theory
Arroyo, E Aldo
2016-01-01
Performing a gauge transformation of an identity based solution, we construct a one-parameter family of solutions, and by evaluating the energy associated to these solutions, we show that depending on the value of the parameter, the solution interpolates between three distinct gauge orbits corresponding to the perturbative vacuum, the half brane and the tachyon vacuum solution.
Comparison of Present SST Gravity Field Models
Institute of Scientific and Technical Information of China (English)
LUO Jia; SHI Chuang; ZOU Xiancai; WANG Haihong
2006-01-01
Taking the main land of Europe as the region to be studied, the potential of the new satellite gravity technique: satellite-to-satellite tracking (SST) and improving the accuracy of regional gravity field model with the SST models are investigated. The drawbacks of these models are discussed. With GPM98C as the reference, the gravity anomaly residuals of several other models, the latest SST global gravity field models (EIGEN series and GGM series), were computed and compared. The results of the comparison show that in the selected region, some systematic errors with periodical properties exist in the EIGEN and GGM's S series models in the high degree and order. Some information that was not shown in the classic gravity models is detected in the low and middle degree and order of EIGEN and GGM's S series models. At last, the effective maximum degrees and orders of SST models are suggested.
Mathematical Properties Relevant to Geomagnetic Field Modeling
DEFF Research Database (Denmark)
Sabaka, Terence J.; Hulot, Gauthier; Olsen, Nils
2010-01-01
properties of those spatial mathematical representations are also discussed, especially in view of providing a formal justification for the fact that geomagnetic field models can indeed be constructed from ground-based and satellite-born observations, provided those reasonably approximate the ideal......Geomagnetic field modeling consists in converting large numbers of magnetic observations into a linear combination of elementary mathematical functions that best describes those observations.The set of numerical coefficients defining this linear combination is then what one refers...... be directly measured. In this chapter, the mathematical foundation of global (as opposed to regional) geomagnetic field modeling is reviewed, and the spatial modeling of the field in spherical coordinates is focussed. Time can be dealt with as an independent variable and is not explicitly considered...
Mathematical Properties Relevant to Geomagnetic Field Modeling
DEFF Research Database (Denmark)
Sabaka, Terence J.; Hulot, Gauthier; Olsen, Nils
2014-01-01
properties of those spatial mathematical representations are also discussed, especially in view of providing a formal justification for the fact that geomagnetic field models can indeed be constructed from ground-based and satellite-born observations, provided those reasonably approximate the ideal situation......Geomagnetic field modeling consists in converting large numbers of magnetic observations into a linear combination of elementary mathematical functions that best describes those observations. The set of numerical coefficients defining this linear combination is then what one refers...... be directly measured. In this chapter, the mathematical foundation of global (as opposed to regional) geomagnetic field modeling is reviewed, and the spatial modeling of the field in spherical coordinates is focused. Time can be dealt with as an independent variable and is not explicitly considered...
Orientational phase transition in cubic liquid crystals with positional order
Pokrovsky, V.L.; Saidachmetov, P.A.
1988-01-01
An electric field can give rise to a shear deformation of a cubic liquid crystal with long-range positional order fixed by two plates. The critical value of the field does not depend on the size of the system and depends crucially on the orientation.
Cubication of Conservative Nonlinear Oscillators
Belendez, Augusto; Alvarez, Mariela L.; Fernandez, Elena; Pascual, Immaculada
2009-01-01
A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear…
Cryptographic Analysis in Cubic Time
DEFF Research Database (Denmark)
Nielson, Flemming; Nielson, Hanne Riis; Seidl, H.
2004-01-01
The spi-calculus is a variant of the polyadic pi-calculus that admits symmetric cryptography and that admits expressing communication protocols in a precise though still abstract way. This paper shows that context-independent control flow analysis can be calculated in cubic time despite the fact ...
The diagonalization of cubic matrices
Cocolicchio, D.; Viggiano, M.
2000-08-01
This paper is devoted to analysing the problem of the diagonalization of cubic matrices. We extend the familiar algebraic approach which is based on the Cardano formulae. We rewrite the complex roots of the associated resolvent secular equation in terms of transcendental functions and we derive the diagonalizing matrix.
Flow field mapping in data rack model
Directory of Open Access Journals (Sweden)
Matěcha J.
2013-04-01
Full Text Available The main objective of this study was to map the flow field inside the data rack model, fitted with three 1U server models. The server model is based on the common four-processor 1U server. The main dimensions of the data rack model geometry are taken fully from the real geometry. Only the model was simplified with respect to the greatest possibility in the experimental measurements. The flow field mapping was carried out both experimentally and numerically. PIV (Particle Image Velocimetry method was used for the experimental flow field mapping, when the flow field has been mapped for defined regions within the 2D/3D data rack model. Ansys CFX and OpenFOAM software were used for the numerical solution. Boundary conditions for numerical model were based on data obtained from experimental measurement of velocity profile at the output of the server mockup. This velocity profile was used as the input boundary condition in the calculation. In order to achieve greater consistency of the numerical model with experimental data, the numerical model was modified with regard to the results of experimental measurements. Results from the experimental and numerical measurements were compared and the areas of disparateness were identified. In further steps the obtained proven numerical model will be utilized for the real geometry of data racks and data.
Supersymmetric structures in topological field models
Pisar, T
2000-01-01
formalism with the latter proposed method. Besides the calculation of the vector supersymmetry the formalism admits the derivation of another scalar supersymmetry which is present in some particular models. The work is organized as follows. In Chapter 2 we give the technical details, Chapter 3 presents a review of the relevant aspects of topological field theories, in Chapter 4 we introduce a formalism which admits the calculation of the vectorial supersymmetry of the basic fields, and the following Chapter 5 demonstrates its application in the case of a six-dimensional Witten type model. Chapter 6 combines this method with the Batalin-Vilkovisky formalism, also including the BRST doublets and Chapter 7 gives three different applications of the latter procedure. During the eighties topological quantum field theory appears the first time as a new link between topology and quantum field theory. In the actual understanding we distinguish two types of topological field theories, the first one originally introduce...
Arbitrary scalar field and quintessence cosmological models
Harko, Tiberiu; Mak, M K
2014-01-01
The mechanism of the initial inflationary scenario of the universe and of its late-time acceleration can be described by assuming the existence of some gravitationally coupled scalar fields $\\phi $, with the inflaton field generating inflation and the quintessence field being responsible for the late accelerated expansion. Various inflationary and late-time accelerated scenarios are distinguished by the choice of an effective self-interaction potential $V(\\phi)$, which simulates a temporarily non-vanishing cosmological term. In this work, we present a new formalism for the analysis of scalar fields in flat isotropic and homogeneous cosmological models. The basic evolution equation of the models can be reduced to a first order non-linear differential equation. Approximate solutions of this equation can be constructed in the limiting cases of the scalar field kinetic energy and potential energy dominance, respectively, as well as in the intermediate regime. Moreover, we present several new accelerating and dece...
Black holes in a cubic Galileon universe
Babichev, Eugeny; Lehébel, Antoine; Moskalets, Tetiana
2016-01-01
We find and study the properties of black hole solutions for a subclass of Horndeski theory including the cubic Galileon term. The theory under study has shift symmetry but not reflection symmetry for the scalar field. The Galileon is assumed to have linear time dependence characterized by a velocity parameter. We give analytic 3-dimensional solutions that are akin to the BTZ solutions but with a non-trivial scalar field that modifies the effective cosmological constant. We then study the 4-dimensional asymptotically flat and de Sitter solutions. The latter present three different branches according to their effective cosmological constant. For two of these branches, we find families of black hole solutions, parametrized by the velocity of the scalar field. These spherically symmetric solutions, obtained numerically, are different from GR solutions close to the black hole event horizon, while they have the same de-Sitter asymptotic behavior. The velocity parameter represents black hole primary hair.
DEFF Research Database (Denmark)
Olsen, Nils; Holme, R.; Hulot, G.
2000-01-01
Magnetic measurements taken by the Orsted satellite during geomagnetic quiet conditions around January 1, 2000 have been used to derive a spherical harmonic model of the Earth's magnetic field for epoch 2000.0. The maximum degree and order of the model is 19 for internal, and 2 for external, sour...
Integrated field modelling[Oil and gas fields
Energy Technology Data Exchange (ETDEWEB)
Nazarian, Bamshad
2002-07-01
This research project studies the feasibility of developing and applying an integrated field simulator to simulate the production performance of an entire oil or gas field. It integrates the performance of the reservoir, the wells, the chokes, the gathering system, the surface processing facilities and whenever applicable, gas and water injection systems. The approach adopted for developing the integrated simulator is to couple existing commercial reservoir and process simulators using available linking technologies. The simulators are dynamically linked and customised into a single hybrid application that benefits from the concept of open software architecture. The integrated field simulator is linked to an optimisation routine developed based on the genetic algorithm search strategies. This enables optimisation of the system at field level, from the reservoir to the process. Modelling the wells and the gathering network is achieved by customising the process simulator. This study demonstrated that the integrated simulation improves current capabilities to simulate the performance of the entire field and optimise its design. This is achieved by evaluating design options including spread and layout of the wells and gathering system, processing alternatives, reservoir development schemes and production strategies. Effectiveness of the integrated simulator is demonstrated and tested through several field-level case studies that discuss and investigate technical problems relevant to offshore field development. The case studies cover topics such as process optimisation, optimum tie-in of satellite wells into existing process facilities, optimal well location and field layout assessment of a high pressure high temperature deepwater oil field. Case study results confirm the viability of the total field simulator by demonstrating that the field performance simulation and optimal design were obtained in an automated process with treasonable computation time. No significant
Integrated field modelling[Oil and gas fields
Energy Technology Data Exchange (ETDEWEB)
Nazarian, Bamshad
2002-07-01
This research project studies the feasibility of developing and applying an integrated field simulator to simulate the production performance of an entire oil or gas field. It integrates the performance of the reservoir, the wells, the chokes, the gathering system, the surface processing facilities and whenever applicable, gas and water injection systems. The approach adopted for developing the integrated simulator is to couple existing commercial reservoir and process simulators using available linking technologies. The simulators are dynamically linked and customised into a single hybrid application that benefits from the concept of open software architecture. The integrated field simulator is linked to an optimisation routine developed based on the genetic algorithm search strategies. This enables optimisation of the system at field level, from the reservoir to the process. Modelling the wells and the gathering network is achieved by customising the process simulator. This study demonstrated that the integrated simulation improves current capabilities to simulate the performance of the entire field and optimise its design. This is achieved by evaluating design options including spread and layout of the wells and gathering system, processing alternatives, reservoir development schemes and production strategies. Effectiveness of the integrated simulator is demonstrated and tested through several field-level case studies that discuss and investigate technical problems relevant to offshore field development. The case studies cover topics such as process optimisation, optimum tie-in of satellite wells into existing process facilities, optimal well location and field layout assessment of a high pressure high temperature deepwater oil field. Case study results confirm the viability of the total field simulator by demonstrating that the field performance simulation and optimal design were obtained in an automated process with treasonable computation time. No significant
Bicritical universality of the anisotropic Heisenberg model in a crystal field.
Freire, R T S; Plascak, J A
2015-03-01
The bicritical properties of the three-dimensional classical anisotropic Heisenberg model in a crystal field are investigated through extensive Monte Carlo simulations on a simple cubic lattice, using Metropolis and Wolff algorithms. Field-mixing and multidimensional histogram techniques were employed in order to compute the probability distribution function of the extensive conjugate variables of interest and, using finite-size scaling analysis, the first-order transition line of the model was precisely located. The fourth-order cumulant of the order parameter was then calculated along this line and the bicritical point located with good precision from the cumulant crossings. The bicritical properties of this point were further investigated through the measurement of the universal probability distribution function of the order parameter. The results lead us to conclude that the studied bicritical point belongs in fact to the three-dimensional Heisenberg universality class.
IMP 8 magnetosheath field comparisons with models
Directory of Open Access Journals (Sweden)
Z. Kaymaz
Full Text Available This study presents cross-sectional vector maps of the magnetic field derived from IMP 8 magnetometer in the magnetosheath at 30 R_{e} behind the Earth. In addition the vector patterns of the magnetosheath field for northward, southward, and east-west interplanetary magnetic field (IMF directions are qualitatively compared with those obtained from the Spreiter-Stahara gas dynamic (GD and Fedder-Lyon magnetohydrodynamic models (MHD. The main purpose is to display the cross-sectional differences in relation to the dayside merging with different IMF directions, allowing the reader to make direct visual comparisons of the vector patterns. It is seen that for east-west IMF directions, the data-based and MHD-based patterns differ noticeably in a similar way from the GD model, presumably reflecting the influence of dayside magnetic merging of the Earth's magnetic field with the y-component of the interplanetary magnetic field. All three northward IMF cross sections show comparable field draping patterns as expected for a closed magnetosphere. For southward IMF case, on the other hand, differences between the three cross-sectional patterns are greater as seen in the field vector sizes and directions, especially closer to the magnetopause where more disturbed magnetospheric conditions are known to be exist. The data comparisons with the MHD and GD models show that the differences result from the magnetic field-flow coupling and that the effects of dayside reconnection are present in IMP 8 magnetic field measurements.
Keywords. Vector maps · IMP 8 magnetometer · Inter-planetary magnetic fields
Spinor bose gases in cubic optical lattice
Energy Technology Data Exchange (ETDEWEB)
Mobarak, Mohamed Saidan Sayed Mohamed
2014-01-27
In recent years the quantum simulation of condensed-matter physics problems has resulted from exciting experimental progress in the realm of ultracold atoms and molecules in optical lattices. In this thesis we analyze theoretically a spinor Bose gas loaded into a three-dimensional cubic optical lattice. In order to account for different superfluid phases of spin-1 bosons with a linear Zeeman effect, we work out a Ginzburg-Landau theory for the underlying spin-1 Bose-Hubbard model. To this end we add artificial symmetry-breaking currents to the spin-1 Bose-Hubbard Hamiltonian in order to break the global U (1) symmetry. With this we determine a diagrammatic expansion of the grand-canonical free energy up to fourth order in the symmetry-breaking currents and up to the leading non-trivial order in the hopping strength which is of first order. As a cross-check we demonstrate that the resulting grand-canonical free energy allows to recover the mean-field theory. Applying a Legendre transformation to the grand-canonical free energy, where the symmetry-breaking currents are transformed to order parameters, we obtain the effective Ginzburg-Landau action. With this we calculate in detail at zero temperature the Mott insulator-superfluid quantum phase boundary as well as condensate and particle number density in the superfluid phase. We find that both mean-field and Ginzburg-Landau theory yield the same quantum phase transition between the Mott insulator and superfluid phases, but the range of validity of the mean-field theory turns out to be smaller than that of the Ginzburg-Landau theory. Due to this finding we expect that the Ginzburg-Landau theory gives better results for the superfluid phase and, thus, we restrict ourselves to extremize only the effective Ginzburg-Landau action with respect to the order parameters. Without external magnetic field the superfluid phase is a polar (ferromagnetic) state for anti-ferromagnetic (ferromagnetic) interactions, i.e. only the
Improving lognormal models for cosmological fields
Xavier, Henrique S; Joachimi, Benjamin
2016-01-01
It is common practice in cosmology to model large-scale structure observables as lognormal random fields, and this approach has been successfully applied in the past to the matter density and weak lensing convergence fields separately. We argue that this approach has fundamental limitations which prevent its use for jointly modelling these two fields since the lognormal distribution's shape can prevent certain correlations to be attainable. Given the need of ongoing and future large-scale structure surveys for fast joint simulations of clustering and weak lensing, we propose two ways of overcoming these limitations. The first approach slightly distorts the power spectra of the fields using one of two algorithms that minimises either the absolute or the fractional distortions. The second one is by obtaining more accurate convergence marginal distributions, for which we provide a fitting function, by integrating the lognormal density along the line of sight. The latter approach also provides a way to determine ...
Cubication of conservative nonlinear oscillators
Energy Technology Data Exchange (ETDEWEB)
Belendez, Augusto; Alvarez, Mariela L [Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain); Fernandez, Elena; Pascual, Inmaculada [Departamento de Optica, FarmacologIa y Anatomia, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain)], E-mail: a.belendez@ua.es
2009-09-15
A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear and cubic terms depend on the initial amplitude, A, while in a Taylor expansion of the restoring force these coefficients are independent of A. The replacement of the original nonlinear equation by an approximate Duffing equation allows us to obtain an approximate frequency-amplitude relation as a function of the complete elliptic integral of the first kind. Some conservative nonlinear oscillators are analysed to illustrate the usefulness and effectiveness of this scheme.
A Hamiltonian Five-Field Gyrofluid Model
Keramidas Charidakos, Ioannis; Waelbroeck, Francois; Morrison, Philip
2015-11-01
Reduced fluid models constitute versatile tools for the study of multi-scale phenomena. Examples include magnetic islands, edge localized modes, resonant magnetic perturbations, and fishbone and Alfven modes. Gyrofluid models improve over Braginskii-type models by accounting for the nonlocal response due to particle orbits. A desirable property for all models is that they not only have a conserved energy, but also that they be Hamiltonian in the ideal limit. Here, a Lie-Poisson bracket is presented for a five-field gyrofluid model, thereby showing the model to be Hamiltonian. The model includes the effects of magnetic field curvature and describes the evolution of electron and ion densities, the parallel component of ion and electron velocities and ion temperature. Quasineutrality and Ampere's law determine respectively the electrostatic potential and magnetic flux. The Casimir invariants are presented, and shown to be associated to five Lagrangian invariants advected by distinct velocity fields. A linear, local study of the model is conducted both with and without Landau and diamagnetic resonant damping terms. Stability criteria and dispersion relations for the electrostatic and the electromagnetic cases are derived and compared with their analogs for fluid and kinetic models. This work was funded by U.S. DOE Contract No. DE-FG02-04ER-54742.
Cubic Matrix, Nambu Mechanics and Beyond
Kawamura, Y
2002-01-01
We propose a generalization of cubic matrix mechanics by introducing a canonical triplet and study its relation to Nambu mechanics. The generalized cubic matrix mechanics we consider can be interpreted as a “quantum” generalization of Nambu mechanics.
Cubic interactions of Maxwell-like higher spins
Francia, Dario; Mkrtchyan, Karapet
2016-01-01
We study the cubic vertices for Maxwell-like higher-spins in flat space. Reducibility of their free spectra implies that a single cubic vertex involving any three fields subsumes a number of couplings among different particles of various spins. The resulting vertices do not involve traces of the fields and in this sense are simpler than their Fronsdal counterparts. We propose an extension of both the free theory and of its cubic deformation to a more general class of partially reducible systems, that one can obtain from the original theory upon imposing trace constraints of various orders. The key to our results is a version of the Noether procedure allowing to systematically account for the deformations of the transversality conditions to be imposed on the gauge parameters at the free level.
Numbers for reducible cubic scrolls
Directory of Open Access Journals (Sweden)
Israel Vainsencher
2004-12-01
Full Text Available We show how to compute the number of reducible cubic scrolls of codimension 2 in (math blackboard symbol Pn incident to the appropriate number of linear spaces.Mostramos como calcular o número de rolos cúbicos redutíveis de codimensão 2 em (math blackboard symbol Pn incidentes a espaços lineares apropriados.
Field Assessment Techniques for Bank Erosion Modeling
1990-11-22
Field Assessment Techniques for Bank Erosion Modeling First Interim Report Prepared for US Army European Research Office US AR DS G-. EDISON HOUSE...SEDIMENTATION ANALYSIS SHEETS and GUIDELINES FOR THE USE OF SEDIMENTATION ANALYSIS SHEETS IN THE FIELD Prepared for US Army Engineer Waterways Experiment...Material Type 3 Material Type 4 Cobbles Toe[’ Toe Toefl Toefl Protection Status Cobbles/boulders Mid-Bnak .. Mid-na.k Mid-Bnask[ Mid-Boak
Fractal Symmetries: Ungauging the Cubic Code
Williamson, Dominic J
2016-01-01
Gauging is a ubiquitous tool in many-body physics. It allows one to construct highly entangled topological phases of matter from relatively simple phases and to relate certain characteristics of the two. Here we develop a gauging procedure for general submanifold symmetries of Pauli Hamiltonians, including symmetries of fractal type. We show a relation between the pre- and post- gauging models and use this to construct short range entangled phases with fractal like symmetries, one of which is mapped to the cubic code by the gauging.
String Field Equations from Generalized Sigma Model
Energy Technology Data Exchange (ETDEWEB)
Bardakci, K.; Bernardo, L.M.
1997-01-29
We propose a new approach for deriving the string field equations from a general sigma model on the world-sheet. This approach leads to an equation which combines some of the attractive features of both the renormalization group method and the covariant beta function treatment of the massless excitations. It has the advantage of being covariant under a very general set of both local and non-local transformations in the field space. We apply it to the tachyon, massless and first massive level, and show that the resulting field equations reproduce the correct spectrum of a left-right symmetric closed bosonic string.
Modeling emotional dynamics : currency versus field.
Energy Technology Data Exchange (ETDEWEB)
Sallach, D .L.; Decision and Information Sciences; Univ. of Chicago
2008-08-01
Randall Collins has introduced a simplified model of emotional dynamics in which emotional energy, heightened and focused by interaction rituals, serves as a common denominator for social exchange: a generic form of currency, except that it is active in a far broader range of social transactions. While the scope of this theory is attractive, the specifics of the model remain unconvincing. After a critical assessment of the currency theory of emotion, a field model of emotion is introduced that adds expressiveness by locating emotional valence within its cognitive context, thereby creating an integrated orientation field. The result is a model which claims less in the way of motivational specificity, but is more satisfactory in modeling the dynamic interaction between cognitive and emotional orientations at both individual and social levels.
Cubic colloids : Synthesis, functionalization and applications
Castillo, S.I.R.
2015-01-01
This thesis is a study on cubic colloids: micron-sized cubic particles with rounded corners (cubic superballs). Owing to their shape, particle packing for cubes is more efficient than for spheres and results in fascinating phase and packing behavior. For our cubes, the particle volume fraction when
Cubic colloids : Synthesis, functionalization and applications
Castillo, S.I.R.
2015-01-01
This thesis is a study on cubic colloids: micron-sized cubic particles with rounded corners (cubic superballs). Owing to their shape, particle packing for cubes is more efficient than for spheres and results in fascinating phase and packing behavior. For our cubes, the particle volume fraction when
Solving Cubic Equations by Polynomial Decomposition
Kulkarni, Raghavendra G.
2011-01-01
Several mathematicians struggled to solve cubic equations, and in 1515 Scipione del Ferro reportedly solved the cubic while participating in a local mathematical contest, but did not bother to publish his method. Then it was Cardano (1539) who first published the solution to the general cubic equation in his book "The Great Art, or, The Rules of…
Field modeling for transcranial magnetic stimulation
DEFF Research Database (Denmark)
Thielscher, Axel; Antunes, Andre; Saturnino, Guilherme B
2015-01-01
Electric field calculations based on numerical methods and increasingly realistic head models are more and more used in research on Transcranial Magnetic Stimulation (TMS). However, they are still far from being established as standard tools for the planning and analysis in practical applications...... of TMS. Here, we start by delineating three main challenges that need to be addressed to unravel their full potential. This comprises (i) identifying and dealing with the model uncertainties, (ii) establishing a clear link between the induced fields and the physiological stimulation effects, and (iii...
Preliminary Phase Field Computational Model Development
Energy Technology Data Exchange (ETDEWEB)
Li, Yulan [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hu, Shenyang Y. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Xu, Ke [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Suter, Jonathan D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McCloy, John S. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Johnson, Bradley R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Ramuhalli, Pradeep [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2014-12-15
This interim report presents progress towards the development of meso-scale models of magnetic behavior that incorporate microstructural information. Modeling magnetic signatures in irradiated materials with complex microstructures (such as structural steels) is a significant challenge. The complexity is addressed incrementally, using the monocrystalline Fe (i.e., ferrite) film as model systems to develop and validate initial models, followed by polycrystalline Fe films, and by more complicated and representative alloys. In addition, the modeling incrementally addresses inclusion of other major phases (e.g., martensite, austenite), minor magnetic phases (e.g., carbides, FeCr precipitates), and minor nonmagnetic phases (e.g., Cu precipitates, voids). The focus of the magnetic modeling is on phase-field models. The models are based on the numerical solution to the Landau-Lifshitz-Gilbert equation. From the computational standpoint, phase-field modeling allows the simulation of large enough systems that relevant defect structures and their effects on functional properties like magnetism can be simulated. To date, two phase-field models have been generated in support of this work. First, a bulk iron model with periodic boundary conditions was generated as a proof-of-concept to investigate major loop effects of single versus polycrystalline bulk iron and effects of single non-magnetic defects. More recently, to support the experimental program herein using iron thin films, a new model was generated that uses finite boundary conditions representing surfaces and edges. This model has provided key insights into the domain structures observed in magnetic force microscopy (MFM) measurements. Simulation results for single crystal thin-film iron indicate the feasibility of the model for determining magnetic domain wall thickness and mobility in an externally applied field. Because the phase-field model dimensions are limited relative to the size of most specimens used in
Cosmological aspects of a vector field model
Sadatian, S Davood
2012-01-01
We have studied a DGP-inspired braneworld scenario where the idea of Lorentz invariance violation has been combined into a specifying preferred frame that embed a dynamical normal vector field to brane. We propose the Lorentz violating DGP brane models with enough parameters can explain crossing of phantom divide line. Also we have considered the model for proper cosmological evolution that is according to the observed behavior of the equation of state. In other view point, we have described a Rip singularity solution of model that occur in this model.
Energy Technology Data Exchange (ETDEWEB)
Burgess, Ward A.; Tapriyal, Deepak; Morreale, Bryan D.; Soong, Yee; Baled, Hseen O.; Enick, Robert M.; Wu, Yue; Bamgbade, Babatunde A.; McHugh, Mark A.
2013-12-01
This research focuses on providing the petroleum reservoir engineering community with robust models of hydrocarbon density and viscosity at the extreme temperature and pressure conditions (up to 533 K and 276 MPa, respectively) characteristic of ultra-deep reservoirs, such as those associated with the deepwater wells in the Gulf of Mexico. Our strategy is to base the volume-translated (VT) Peng–Robinson (PR) and Soave–Redlich–Kwong (SRK) cubic equations of state (EoSs) and perturbed-chain, statistical associating fluid theory (PC-SAFT) on an extensive data base of high temperature (278–533 K), high pressure (6.9–276 MPa) density rather than fitting the models to low pressure saturated liquid density data. This high-temperature, high-pressure (HTHP) data base consists of literature data for hydrocarbons ranging from methane to C{sub 40}. The three new models developed in this work, HTHP VT-PR EoS, HTHP VT-SRK EoS, and hybrid PC-SAFT, yield mean absolute percent deviation values (MAPD) for HTHP hydrocarbon density of ~2.0%, ~1.5%, and <1.0%, respectively. An effort was also made to provide accurate hydrocarbon viscosity models based on literature data. Viscosity values are estimated with the frictional theory (f-theory) and free volume (FV) theory of viscosity. The best results were obtained when the PC-SAFT equation was used to obtain both the attractive and repulsive pressure inputs to f-theory, and the density input to FV theory. Both viscosity models provide accurate results at pressures to 100 MPa but experimental and model results can deviate by more than 25% at pressures above 200 MPa.
Magnetic field screening effect in electroweak model
Bakry, A; Zhang, P M; Zou, L P
2014-01-01
It is shown that in the Weinberg-Salam model a magnetic field screening effect for static magnetic solutions takes place. The origin of that phenomenon is conditioned by features of the electro-weak interaction, namely, there is mutual cancellation of Abelian magnetic fields created by the SU(2) gauge fields and Higgs boson. The effect implies monopole charge screening in finite energy system of monopoles and antimonopoles. We consider another manifestation of the screening effect which leads to an essential energy decrease of magnetic solutions. Applying variational method we have found a magnetic field configuration with a topological azimuthal magnetic flux which minimizes the energy functional and possesses a total energy of order 1 TeV. We suppose that corresponding magnetic bound state exists in the electroweak theory and can be detected in experiment.
Invisible dynamo in mean-field models
Reshetnyak, M. Yu.
2016-07-01
The inverse problem in a spherical shell to find the two-dimensional spatial distributions of the α-effect and differential rotation in a mean-field dynamo model has been solved. The derived distributions lead to the generation of a magnetic field concentrated inside the convection zone. The magnetic field is shown to have no time to rise from the region of maximum generation located in the lower layers to the surface in the polarity reversal time due to magnetic diffusion. The ratio of the maximum magnetic energy in the convection zone to its value at the outer boundary reaches two orders of magnitude or more. This result is important in interpreting the observed stellar and planetary magnetic fields. The proposed method of solving the inverse nonlinear dynamo problem is easily adapted for a wide class of mathematical-physics problems.
The influence of coordinated defects on inhomogeneous broadening in cubic lattices
Matheson, P. L.; Sullivan, Francis P.; Evenson, William E.
2016-12-01
The joint probability distribution function (JPDF) of electric field gradient (EFG) tensor components in cubic materials is dominated by coordinated pairings of defects in shells near probe nuclei. The contributions from these inner shell combinations and their surrounding structures contain the essential physics that determine the PAC-relevant quantities derived from them. The JPDF can be used to predict the nature of inhomogeneous broadening (IHB) in perturbed angular correlation (PAC) experiments by modeling the G 2 spectrum and finding expectation values for V zz and η. The ease with which this can be done depends upon the representation of the JPDF. Expanding on an earlier work by Czjzek et al. (Hyperfine Interact. 14, 189-194, 1983), Evenson et al. (Hyperfine Interact. 237, 119, 2016) provide a set of coordinates constructed from the EFG tensor invariants they named W 1 and W 2. Using this parameterization, the JPDF in cubic structures was constructed using a point charge model in which a single trapped defect (TD) is the nearest neighbor to a probe nucleus. Individual defects on nearby lattice sites pair with the TD to provide a locus of points in the W 1- W 2 plane around which an amorphous-like distribution of probability density grows. Interestingly, however, marginal, separable PDFs appear adequate to model IHB relevant cases. We present cases from simulations in cubic materials illustrating the importance of these near-shell coordinations.
Improved modeling techniques for turbomachinery flow fields
Energy Technology Data Exchange (ETDEWEB)
Lakshminarayana, B.; Fagan, J.R. Jr.
1995-12-31
This program has the objective of developing an improved methodology for modeling turbomachinery flow fields, including the prediction of losses and efficiency. Specifically, the program addresses the treatment of the mixing stress tensor terms attributed to deterministic flow field mechanisms required in steady-state Computational Fluid Dynamic (CFD) models for turbomachinery flow fields. These mixing stress tensors arise due to spatial and temporal fluctuations (in an absolute frame of reference) caused by rotor-stator interaction due to various blade rows and by blade-to-blade variation of flow properties. This will be accomplished in a cooperative program by Penn State University and the Allison Engine Company. These tasks include the acquisition of previously unavailable experimental data in a high-speed turbomachinery environment, the use of advanced techniques to analyze the data, and the development of a methodology to treat the deterministic component of the mixing stress tenor.
Cubic metaplectic forms and theta functions
Proskurin, Nikolai
1998-01-01
The book is an introduction to the theory of cubic metaplectic forms on the 3-dimensional hyperbolic space and the author's research on cubic metaplectic forms on special linear and symplectic groups of rank 2. The topics include: Kubota and Bass-Milnor-Serre homomorphisms, cubic metaplectic Eisenstein series, cubic theta functions, Whittaker functions. A special method is developed and applied to find Fourier coefficients of the Eisenstein series and cubic theta functions. The book is intended for readers, with beginning graduate-level background, interested in further research in the theory of metaplectic forms and in possible applications.
$C$-field cosmological models: revisited
Yadav, A K; Ray, Saibal; Rahaman, F; Sardar, I H
2015-01-01
We investigate plane symmetric space-time filled with perfect fluid in the $C$-field cosmology of Hoyle and Narlikar. A new class of exact solutions have been obtained by considering the creation field $C$ as a function of time only. To get the deterministic solution, it has been assumed that the rate of creation of matter-energy density is proportional to the strength of the existing $C$-field energy density. Several physical aspects and geometrical properties of the models are discussed in detail, especially it is shown that some of our solutions of $C$-field cosmology are free from singularity in contrast to the Big Bang cosmology. A comparative study has been carried out between two models, one singular and the other nonsingular, by contrasting the behaviour of the physical parameters and noted that the model in a unique way represents both the features of the accelerating as well as decelerating Universe depending on the parameters and thus seems provides glimpses of the oscillating or cyclic model of th...
Gelfgat, Alexander Yu.
2017-08-01
Transition from steady to oscillatory buoyancy convection of air in a laterally heated cubic box is studied numerically by straight-forward time integration of Boussinesq equations using a series of gradually refined finite volume grids. Horizontal and spanwise cube boundaries are assumed to be either perfectly thermally conducting or perfectly thermally insulated, which results in four different sets of thermal boundary conditions. Critical Grashof numbers are obtained by interpolation of numerically extracted growth/decay rates of oscillation amplitude to zero. Slightly supercritical flow regimes are described by time-averaged flows, snapshots, and spatial distribution of the oscillation amplitude. Possible similarities and dissimilarities with two-dimensional instabilities in laterally heated square cavities are discussed. Break of symmetries and sub- or supercritical character of bifurcations are examined. Three consequent transitions from steady to the oscillatory regime, from the oscillatory to the steady regime, and finally to the oscillatory flow, are found in the case of perfectly insulated horizontal and spanwise boundaries. Arguments for grid and time-step independence of the results are given.
Weighted cubic and biharmonic splines
Kvasov, Boris; Kim, Tae-Wan
2017-01-01
In this paper we discuss the design of algorithms for interpolating discrete data by using weighted cubic and biharmonic splines in such a way that the monotonicity and convexity of the data are preserved. We formulate the problem as a differential multipoint boundary value problem and consider its finite-difference approximation. Two algorithms for automatic selection of shape control parameters (weights) are presented. For weighted biharmonic splines the resulting system of linear equations can be efficiently solved by combining Gaussian elimination with successive over-relaxation method or finite-difference schemes in fractional steps. We consider basic computational aspects and illustrate main features of this original approach.
Invisible 'glue' bosons in model field theory
Shirokov, M I
2002-01-01
Fermionic psi(x) and bosonic phi(x) fields with vector coupling are discussed. It is shown that 'clothed' bosons of the model do not interact with fermions and between themselves. If phi(x) does not interact with other fields of the particle physics, then the 'clothed' bosons have properties of the cosmological 'dark' matter': they cannot be detected in Earth's laboratories. This cause of the boson invisibility contrasts with the origin of the unobservability of the isolated gluons in QCD which is explained by the confinement of colour
Improved modeling techniques for turbomachinery flow fields
Energy Technology Data Exchange (ETDEWEB)
Lakshminarayana, B. [Pennsylvania State Univ., University Park, PA (United States); Fagan, J.R. Jr. [Allison Engine Company, Indianapolis, IN (United States)
1995-10-01
This program has the objective of developing an improved methodology for modeling turbomachinery flow fields, including the prediction of losses and efficiency. Specifically, the program addresses the treatment of the mixing stress tensor terms attributed to deterministic flow field mechanisms required in steady-state Computational Fluid Dynamic (CFD) models for turbo-machinery flow fields. These mixing stress tensors arise due to spatial and temporal fluctuations (in an absolute frame of reference) caused by rotor-stator interaction due to various blade rows and by blade-to-blade variation of flow properties. These tasks include the acquisition of previously unavailable experimental data in a high-speed turbomachinery environment, the use of advanced techniques to analyze the data, and the development of a methodology to treat the deterministic component of the mixing stress tensor. Penn State will lead the effort to make direct measurements of the momentum and thermal mixing stress tensors in high-speed multistage compressor flow field in the turbomachinery laboratory at Penn State. They will also process the data by both conventional and conditional spectrum analysis to derive momentum and thermal mixing stress tensors due to blade-to-blade periodic and aperiodic components, revolution periodic and aperiodic components arising from various blade rows and non-deterministic (which includes random components) correlations. The modeling results from this program will be publicly available and generally applicable to steady-state Navier-Stokes solvers used for turbomachinery component (compressor or turbine) flow field predictions. These models will lead to improved methodology, including loss and efficiency prediction, for the design of high-efficiency turbomachinery and drastically reduce the time required for the design and development cycle of turbomachinery.
Energy Technology Data Exchange (ETDEWEB)
Parente, Walter E.F.; Pacobahyba, J.T.M.; Araújo, Ijanílio G. [Departamento de Física, Universidade Federal de Roraima, BR 174, Km 12. Bairro Monte Cristo. CEP: 69300-000 Boa Vista, Roraima (Brazil); Neto, Minos A., E-mail: minos@pq.cnpq.br [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-000, Manaus-AM (Brazil); Ricardo de Sousa, J. [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-000, Manaus-AM (Brazil); National Institute of Science and Technology for Complex Systems, 3000, Japiim, 69077-000, Manaus-AM (Brazil); Akinci, Ümit [Department of Physics, Dokuz Eylül University, Tr-35160 Izmir (Turkey)
2014-04-15
In this paper we study the quantum spin-1/2 anisotropic Heisenberg antiferromagnet model in the presence of a Dzyaloshinskii–Moriya interaction (D) and a uniform longitudinal (H) magnetic field. Using the effective-field theory with a finite cluster N=2 spin (EFT-2) we calculate the phase diagrams in the H−T and D−T planes on a simple cubic lattice (z=6). We have only observed second order phase transitions for values between Δ∈[0,1], where the cases were analysed: Ising (Δ=1), anisotropic Heisenberg (Δ=0.6) and isotropic Heisenberg (Δ=0). - Highlights: • Anisotropic Heisenberg antiferromagnet on a simple cubic lattice. • Effective-field theory. • Dzyaloshinskii–Moriya interaction.
On the plane-wave cubic vertex
Lucietti, J; Sinha, A K; Lucietti, James; Schäfer-Nameki, Sakura; Sinha, Aninda
2004-01-01
The exact bosonic Neumann matrices of the cubic vertex in plane-wave light-cone string field theory are derived using the contour integration techniques developed in our earlier paper. This simplifies the original derivation of the vertex. In particular, the Neumann matrices are written in terms of \\mu-deformed Gamma-functions, thus casting them into a form that elegantly generalizes the well-known flat-space solution. The asymptotics of the \\mu-deformed Gamma-functions allow one to determine the large-\\mu behaviour of the Neumann matrices including exponential corrections. We provide an explicit expression for the first exponential correction and make a conjecture for the subsequent exponential correction terms.
On the Stability of Cubic Galileon Accretion
Bergliaffa, Santiago P E
2016-01-01
We examine the stability of steady-state galileon accretion for the case of a Schwarzshild black hole. Considering the galileon action up to the cubic term in a static and spherically symmetric background we obtain the general solution for the equation of motion which is divided in two branches. By perturbing this solution we define an effective metric which determines the propagation of fluctuations. In this general picture we establish the position of the sonic horizon together with the matching condition of the two branches on it. Restricting to the case of a Schwarzschild background, we show, via the analysis of the energy of the perturbations and its time derivative, that the accreting field is linearly stable.
Transparent polycrystalline cubic silicon nitride
Nishiyama, Norimasa; Ishikawa, Ryo; Ohfuji, Hiroaki; Marquardt, Hauke; Kurnosov, Alexander; Taniguchi, Takashi; Kim, Byung-Nam; Yoshida, Hidehiro; Masuno, Atsunobu; Bednarcik, Jozef; Kulik, Eleonora; Ikuhara, Yuichi; Wakai, Fumihiro; Irifune, Tetsuo
2017-01-01
Glasses and single crystals have traditionally been used as optical windows. Recently, there has been a high demand for harder and tougher optical windows that are able to endure severe conditions. Transparent polycrystalline ceramics can fulfill this demand because of their superior mechanical properties. It is known that polycrystalline ceramics with a spinel structure in compositions of MgAl2O4 and aluminum oxynitride (γ-AlON) show high optical transparency. Here we report the synthesis of the hardest transparent spinel ceramic, i.e. polycrystalline cubic silicon nitride (c-Si3N4). This material shows an intrinsic optical transparency over a wide range of wavelengths below its band-gap energy (258 nm) and is categorized as one of the third hardest materials next to diamond and cubic boron nitride (cBN). Since the high temperature metastability of c-Si3N4 in air is superior to those of diamond and cBN, the transparent c-Si3N4 ceramic can potentially be used as a window under extremely severe conditions. PMID:28303948
Rheological properties of Cubic colloidal suspensions
Boromand, Arman; Maia, Joao
2016-11-01
Colloidal and non-colloidal suspensions are ubiquitous in many industrial application. There are numerous studies on these systems to understand and relate their complex rheological properties to their microstructural evolution under deformation. Although most of the experimental and simulation studies are centered on spherical particles, in most of the industrial applications the geometry of the colloidal particles deviate from the simple hard sphere and more complex geometries exist. Recent advances in microfabrication paved the way to fabricate colloidal particles with complex geometries for applications in different areas such as drug delivery where the fundamental understanding of their dynamics has remained unexplored. In this study, using dissipative particle dynamics, we investigate the rheological properties of cubic (superball) particles which are modeled as the cluster of core-modified DPD particles. Explicit representation of solvent particles in the DPD scheme will conserve the full hydrodynamic interactions between colloidal particles. Rheological properties of these cubic suspensions are investigated in the dilute and semi-dilute regimes. The Einstein and Huggins coefficients for these particles with different superball exponent will be calculate which represent the effect of single particle's geometry and multibody interactions on viscosity, respectively. The response of these suspensions is investigated under simple shear and oscillatory shear where it is shown that under oscillation these particles tend to form crystalline structure giving rise to stronger shear-thinning behavior recently measured experimentally.
High-performance phase-field modeling
Vignal, Philippe
2015-04-27
Many processes in engineering and sciences involve the evolution of interfaces. Among the mathematical frameworks developed to model these types of problems, the phase-field method has emerged as a possible solution. Phase-fields nonetheless lead to complex nonlinear, high-order partial differential equations, whose solution poses mathematical and computational challenges. Guaranteeing some of the physical properties of the equations has lead to the development of efficient algorithms and discretizations capable of recovering said properties by construction [2, 5]. This work builds-up on these ideas, and proposes novel discretization strategies that guarantee numerical energy dissipation for both conserved and non-conserved phase-field models. The temporal discretization is based on a novel method which relies on Taylor series and ensures strong energy stability. It is second-order accurate, and can also be rendered linear to speed-up the solution process [4]. The spatial discretization relies on Isogeometric Analysis, a finite element method that possesses the k-refinement technology and enables the generation of high-order, high-continuity basis functions. These basis functions are well suited to handle the high-order operators present in phase-field models. Two-dimensional and three dimensional results of the Allen-Cahn, Cahn-Hilliard, Swift-Hohenberg and phase-field crystal equation will be presented, which corroborate the theoretical findings, and illustrate the robustness of the method. Results related to more challenging examples, namely the Navier-Stokes Cahn-Hilliard and a diusion-reaction Cahn-Hilliard system, will also be presented. The implementation was done in PetIGA and PetIGA-MF, high-performance Isogeometric Analysis frameworks [1, 3], designed to handle non-linear, time-dependent problems.
Heisenberg necklace model in a magnetic field
Tsvelik, A. M.; Zaliznyak, I. A.
2016-08-01
We study the low-energy sector of the Heisenberg necklace model. Using the field-theory methods, we estimate how the coupling of the electronic spins with the paramagnetic Kondo spins affects the overall spin dynamics and evaluate its dependence on a magnetic field. We are motivated by the experimental realizations of the spin-1/2 Heisenberg chains in SrCuO2 and Sr2CuO3 cuprates, which remain one-dimensional Luttinger liquids down to temperatures much lower than the in-chain exchange coupling J . We consider the perturbation of the energy spectrum caused by the interaction γ with nuclear spins (I =3 /2 ) present on the same sites. We find that the resulting necklace model has a characteristic energy scale, Λ ˜J1 /3(γI ) 2 /3 , at which the coupling between (nuclear) spins of the necklace and the spins of the Heisenberg chain becomes strong. This energy scale is insensitive to a magnetic field B . For μBB >Λ we find two gapless bosonic modes that have different velocities, whose ratio at strong fields approaches a universal number, √{2 }+1 .
Mechanical models of physical fields and particles
Dmitriyev, V P
1999-01-01
Earlier obtained results on mechanical analogies of physical fields and particles are reviewed. The approach rests on the concept of the substratum - a mechanical medium, which occupies all the space and serves as a seat to support the light and to transmit interactions. A turbulent ideal fluid was chosen for the substratum. The turbulence is supposed to be homogeneous and isotropic in its ground state. Perturbations of the turbulence model physical fields. Particles originate from the voids in the fluid. Symmetrical pairs of particle-antiparticle find analogies in mechanical pairs of cyclone-anticyclone. A quantum particle is modeled by the dispersion of a point discontinuity (defect) in the stochastic medium. Gravitation relates to emitting by defects the continual flow of the transient point dilatation. The shock wave mechanism of the re-collection a discontinuity in the incompressible medium governs such phenomena as the "wave function collapse" and instantaneous quantum correlations. Microscopically, the...
The Structure of the Cubic Coincident Site Lattice Rotation Group
Energy Technology Data Exchange (ETDEWEB)
Reed, B W; Minich, R W; Rudd, R E; Kumar, M
2004-01-13
This work is intended to be a mathematical underpinning for the field of grain boundary engineering and its relatives. The interrelationships within the set of rotations producing coincident site lattices in cubic crystals are examined in detail. Besides combining previously established but widely scattered results into a unified context, the present work details newly developed representations of the group structure in terms of strings of generators (based on quaternionic number theory, and including uniqueness proofs and rules for algebraic manipulation) as well as an easily visualized topological network model. Important results that were previously obscure or not universally understood (e.g. the {Sigma} combination rule governing triple junctions) are clarified in these frameworks. The methods also facilitate several general observations, including the very different natures of twin-limited structures in two and three dimensions, the inadequacy of the {Sigma} combination rule to determine valid quadruple nodes, and a curious link between allowable grain boundary assignments and the four-color map theorem. This kind of understanding is essential to the generation of realistic statistical models of grain boundary networks (particularly in twin-dominated systems) and is especially applicable to the field of grain boundary engineering.
Hysteresis modeling in graphene field effect transistors
Energy Technology Data Exchange (ETDEWEB)
Winters, M.; Rorsman, N. [Department of Microtechnology and Nanoscience, Chalmers University of Technology, 412-96 Göteborg (Sweden); Sveinbjörnsson, E. Ö. [Science Institute, University of Iceland, IS-107 Reykjavik (Iceland)
2015-02-21
Graphene field effect transistors with an Al{sub 2}O{sub 3} gate dielectric are fabricated on H-intercalated bilayer graphene grown on semi-insulating 4H-SiC by chemical vapour deposition. DC measurements of the gate voltage v{sub g} versus the drain current i{sub d} reveal a severe hysteresis of clockwise orientation. A capacitive model is used to derive the relationship between the applied gate voltage and the Fermi energy. The electron transport equations are then used to calculate the drain current for a given applied gate voltage. The hysteresis in measured data is then modeled via a modified Preisach kernel.
Mean-field models for disordered crystals
Cancès, Eric; Lewin, Mathieu
2012-01-01
In this article, we set up a functional setting for mean-field electronic structure models of Hartree-Fock or Kohn-Sham types for disordered crystals. The electrons are quantum particles and the nuclei are classical point-like articles whose positions and charges are random. We prove the existence of a minimizer of the energy per unit volume and the uniqueness of the ground state density of such disordered crystals, for the reduced Hartree-Fock model (rHF). We consider both (short-range) Yukawa and (long-range) Coulomb interactions. In the former case, we prove in addition that the rHF ground state density matrix satisfies a self-consistent equation, and that our model for disordered crystals is the thermodynamic limit of the supercell model.
Energy Technology Data Exchange (ETDEWEB)
Pandey, Rishikesh; Singh, Akhilesh Kumar, E-mail: akhilesh-bhu@yahoo.com [School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)
2014-10-20
The results of x-ray diffraction studies on 0.65Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-0.35PbTiO{sub 3} solid solution poled at various electric fields are presented. After poling, significant value of planar electromechanical coupling coefficient (k{sub P}) is observed for this composition having cubic structure in unpoled state. The cubic structure of 0.65Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-0.35PbTiO{sub 3} transforms to monoclinic structure with space group Pm for the poling field ≥5 kV/cm. Large c-axis microscopic lattice strain (1.6%) is achieved at 30 kV/cm poling field. The variation of the c-axis strain and unit cell volume with poling field shows a drastic jump similar to that observed for strain versus electric field curve in (1 − x)Pb(Mg{sub 1/3}Nb{sub 2/3}) O{sub 3}-xPbTiO{sub 3} and (1 − x)Pb(Zn{sub 1/3}Nb{sub 2/3})O{sub 3}-xPbTiO{sub 3}.
A geomagnetic field model for the Holocene based on archaeomagnetic and lava flow data
Pavón-Carrasco, Francisco Javier; Osete, María Luisa; Torta, Joan Miquel; De Santis, Angelo
2014-02-01
We propose a new geomagnetic field model for the Holocene period based on archaeomagnetic and lava flow data, avoiding the use of lake sediment data. The source of data comes from the GEOMAGIA50v2 database which has been updated with the new archaeomagnetic and volcanic studies published during the last 3 yr. The model, called SHA.DIF.14k, allows us to analyse the behaviour of the geomagnetic field for the last 14 000 yr: from 12 000 BC to 1900 AD. For the model construction we use the spherical harmonic analysis in space and the penalized cubic B-splines in time. Both spatial and temporal regularization norms are used to constrain the inversion problem and applied at the core-mantle boundary (CMB) to assure the convergence of the model. For the last 3 ka, the model predictions agree with those given by the global model ARCH3k.1 and the European model SCHA.DIF.3k. For older epochs, the new model presents a clear improvement in field resolution with respect to other current models of the geomagnetic field for the Holocene. For the last 9 ka, the time evolution of the dipolar moment obtained from the dipole field shows a clear minimum between 5500 BC and 3000 BC, and the well-known continuous decreasing trend of the geomagnetic field strength for the last millennium and a half. A general view of the time-average evolution of the geomagnetic field flux lobes at the CMB for the northern hemisphere suggests a marked lobe of positive magnetic flux when the dipole moment was maximum. This lobe vanishes when the dipolar field is decreasing. The north polar wander paths of both north magnetic dip and geomagnetic poles were obtained showing an average rate of motion of 5.1 km/yr and 3.7 km/yr respectively. The model shows that the geomagnetic field can be averaged as axial dipolar in ˜2000 yr within an error of 5°, the typical uncertainty of the palaeomagnetic studies. Finally, and following the recent definition of archaeomagnetic jerks, we found 8 critical events in the
MODELING FUZZY GEOGRAPHIC OBJECTS WITHIN FUZZY FIELDS
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
To improve the current GIS functions in describing geographic objects w ith fuzziness,this paper begins with a discussion on the distance measure of sp atial objects based on the theory of sets and an introduction of dilation and er osion operators.Under the assumption that changes of attributes in a geographic region are gradual,the analytic expressions for the fuzzy objects of points,l ines and areas,and the description of their formal structures are presented.Th e analytic model of geographic objects by means of fuzzy fields is developed.We have shown that the 9-intersection model proposed by Egenhofer and Franzosa (19 91) is a special case of the model presented in the paper.
Epitaxial and bulk growth of cubic silicon carbide on off-oriented 4H-silicon carbide substrates
Norén, Olof
2015-01-01
The growth of bulk cubic silicon carbide has for a long time seemed to be something for the future. However, in this thesis the initial steps towards bulk cubic silicon carbide have been taken. The achievement of producing bulk cubic silicon carbide will have a great impact in various fields of science and industry such as for example the fields of semiconductor technology within electronic- and optoelectronic devices and bio-medical applications. The process that has been used to grow the bu...
Small shear modulus of cubic CaSiO3 perovskite
Kawai, Kenji; Tsuchiya, Taku
2015-04-01
Ca-perovskite (CaPv) is considered to be one of the most abundant minerals in the Earth's lower mantle (LM). Furthermore, previous static calculations and mean-field theory suggest that it has a much larger shear modulus than bridgmanite (MgPv). In this study, the elasticity of cubic CaPv was reinvestigated using the density functional constant-temperature first principles molecular dynamics method under the correct conditions to simulate its elasticity. Our new results clearly demonstrate that cubic CaPv has comparable bulk and slightly smaller shear moduli than Fe-bearing MgPv. This is because the boundary condition for the supercell used in this study allows for the rotational phonon motion of SiO6 octahedra under strain, which predominantly affects the decrease in C11 and C44. Acoustic wave velocities determined from the elastic moduli indicate that cubic CaPv has slower velocities and larger densities than Fe-bearing MgPv and preliminary reference Earth model in the LM. This suggests that if CaPv-rich material exists, it can accumulate in the lowermost LM and produce a seismically low-velocity anomaly.
Counting perfect matchings of cubic graphs in the geometric dual
Jiménez, Andrea
2010-01-01
Lov\\'asz and Plummer conjectured, in the mid 1970's, that every cubic graph G with no cutedge has an exponential in |V(G)| number of perfect matchings. In this work we show that every cubic planar graph G whose geometric dual graph is a stack triangulation has at least 3 times the golden ratio to |V(G)|/72 distinct perfect matchings. Our work builds on a novel approach relating Lov\\'asz and Plummer's conjecture and the number of so called groundstates of the widely studied Ising model from statistical physics.
Relativistic mean-field mass models
Peña-Arteaga, D.; Goriely, S.; Chamel, N.
2016-10-01
We present a new effort to develop viable mass models within the relativistic mean-field approach with density-dependent meson couplings, separable pairing and microscopic estimations for the translational and rotational correction energies. Two interactions, DD-MEB1 and DD-MEB2, are fitted to essentially all experimental masses, and also to charge radii and infinite nuclear matter properties as determined by microscopic models using realistic interactions. While DD-MEB1 includes the σ, ω and ρ meson fields, DD-MEB2 also considers the δ meson. Both mass models describe the 2353 experimental masses with a root mean square deviation of about 1.1 MeV and the 882 measured charge radii with a root mean square deviation of 0.029 fm. In addition, we show that the Pb isotopic shifts and moments of inertia are rather well reproduced, and the equation of state in pure neutron matter as well as symmetric nuclear matter are in relatively good agreement with existing realistic calculations. Both models predict a maximum neutron-star mass of more than 2.6 solar masses, and thus are able to accommodate the heaviest neutron stars observed so far. However, the new Lagrangians, like all previously determined RMF models, present the drawback of being characterized by a low effective mass, which leads to strong shell effects due to the strong coupling between the spin-orbit splitting and the effective mass. Complete mass tables have been generated and a comparison with other mass models is presented.
Relativistic mean-field mass models
Energy Technology Data Exchange (ETDEWEB)
Pena-Arteaga, D.; Goriely, S.; Chamel, N. [Universite Libre de Bruxelles, Institut d' Astronomie et d' Astrophysique, CP-226, Brussels (Belgium)
2016-10-15
We present a new effort to develop viable mass models within the relativistic mean-field approach with density-dependent meson couplings, separable pairing and microscopic estimations for the translational and rotational correction energies. Two interactions, DD-MEB1 and DD-MEB2, are fitted to essentially all experimental masses, and also to charge radii and infinite nuclear matter properties as determined by microscopic models using realistic interactions. While DD-MEB1 includes the σ, ω and ρ meson fields, DD-MEB2 also considers the δ meson. Both mass models describe the 2353 experimental masses with a root mean square deviation of about 1.1 MeV and the 882 measured charge radii with a root mean square deviation of 0.029 fm. In addition, we show that the Pb isotopic shifts and moments of inertia are rather well reproduced, and the equation of state in pure neutron matter as well as symmetric nuclear matter are in relatively good agreement with existing realistic calculations. Both models predict a maximum neutron-star mass of more than 2.6 solar masses, and thus are able to accommodate the heaviest neutron stars observed so far. However, the new Lagrangians, like all previously determined RMF models, present the drawback of being characterized by a low effective mass, which leads to strong shell effects due to the strong coupling between the spin-orbit splitting and the effective mass. Complete mass tables have been generated and a comparison with other mass models is presented. (orig.)
General complex envelope solutions of coupled-mode optics with quadratic or cubic nonlinearity
Hesketh, Graham D
2015-01-01
The analytic general solutions for the complex field envelopes are derived using Weierstrass elliptic functions for two and three mode systems of differential equations coupled via quadratic $\\chi_2$ type nonlinearity as well as two mode systems coupled via cubic $\\chi_3$ type nonlinearity. For the first time, a compact form of the solutions is given involving simple ratios of Weierstrass sigma functions (or equivalently Jacobi theta functions). A Fourier series is also given. All possible launch states are considered. The models describe sum and difference frequency generation, polarization dynamics, parity-time dynamics and optical processing applications.
Atomic density functional and diagram of structures in the phase field crystal model
Ankudinov, V. E.; Galenko, P. K.; Kropotin, N. V.; Krivilyov, M. D.
2016-02-01
The phase field crystal model provides a continual description of the atomic density over the diffusion time of reactions. We consider a homogeneous structure (liquid) and a perfect periodic crystal, which are constructed from the one-mode approximation of the phase field crystal model. A diagram of 2D structures is constructed from the analytic solutions of the model using atomic density functionals. The diagram predicts equilibrium atomic configurations for transitions from the metastable state and includes the domains of existence of homogeneous, triangular, and striped structures corresponding to a liquid, a body-centered cubic crystal, and a longitudinal cross section of cylindrical tubes. The method developed here is employed for constructing the diagram for the homogeneous liquid phase and the body-centered iron lattice. The expression for the free energy is derived analytically from density functional theory. The specific features of approximating the phase field crystal model are compared with the approximations and conclusions of the weak crystallization and 2D melting theories.
Phase-field modeling of hydraulic fracture
Wilson, Zachary A.; Landis, Chad M.
2016-11-01
In this work a theoretical framework implementing the phase-field approach to fracture is used to couple the physics of flow through porous media and cracks with the mechanics of fracture. The main modeling challenge addressed in this work, which is a challenge for all diffuse crack representations, is on how to allow for the flow of fluid and the action of fluid pressure on the aggregate within the diffuse damage zone of the cracks. The theory is constructed by presenting the general physical balance laws and conducting a consistent thermodynamic analysis to constrain the constitutive relationships. Constitutive equations that reproduce the desired responses at the various limits of the phase-field parameter are proposed in order to capture Darcy-type flow in the intact porous medium and Stokes-type flow within open cracks. A finite element formulation for the solution of the governing model equations is presented and discussed. Finally, the theoretical and numerical model is shown to compare favorably to several important analytical solutions. More complex and interesting calculations are also presented to illustrate some of the advantageous features of the approach.
Near Field Environment Process Model Report
Energy Technology Data Exchange (ETDEWEB)
R.A. Wagner
2000-11-14
Waste emplacement and activities associated with construction of a repository system potentially will change environmental conditions within the repository system. These environmental changes principally result from heat generated by the decay of the radioactive waste, which elevates temperatures within the repository system. Elevated temperatures affect distribution of water, increase kinetic rates of geochemical processes, and cause stresses to change in magnitude and orientation from the stresses resulting from the overlying rock and from underground construction activities. The recognition of this evolving environment has been reflected in activities, studies and discussions generally associated with what has been termed the Near-Field Environment (NFE). The NFE interacts directly with waste packages and engineered barriers as well as potentially changing the fluid composition and flow conditions within the mountain. As such, the NFE defines the environment for assessing the performance of a potential Monitored Geologic Repository at Yucca Mountain, Nevada. The NFe evolves over time, and therefore is not amenable to direct characterization or measurement in the ambient system. Analysis or assessment of the NFE must rely upon projections based on tests and models that encompass the long-term processes of the evolution of this environment. This NFE Process Model Report (PMR) describes the analyses and modeling based on current understanding of the evolution of the near-field within the rock mass extending outward from the drift wall.
Cubic meter volume optical coherence tomography
WANG, ZHAO; POTSAID, BENJAMIN; CHEN, LONG; DOERR, CHRIS; LEE, HSIANG-CHIEH; NIELSON, TORBEN; JAYARAMAN, VIJAYSEKHAR; CABLE, ALEX E.; SWANSON, ERIC; FUJIMOTO, JAMES G.
2017-01-01
Optical coherence tomography (OCT) is a powerful three-dimensional (3D) imaging modality with micrometer-scale axial resolution and up to multi-GigaVoxel/s imaging speed. However, the imaging range of high-speed OCT has been limited. Here, we report 3D OCT over cubic meter volumes using a long coherence length, 1310 nm vertical-cavity surface-emitting laser and silicon photonic integrated circuit dual-quadrature receiver technology combined with enhanced signal processing. We achieved 15 µm depth resolution for tomographic imaging at a 100 kHz axial scan rate over a 1.5 m range. We show 3D macroscopic imaging examples of a human mannequin, bicycle, machine shop gauge blocks, and a human skull/brain model. High-bandwidth, meter-range OCT demonstrates new capabilities that promise to enable a wide range of biomedical, scientific, industrial, and research applications. PMID:28239628
Triangulation of cubic panorama for view synthesis.
Zhang, Chunxiao; Zhao, Yan; Wu, Falin
2011-08-01
An unstructured triangulation approach, new to our knowledge, is proposed to apply triangular meshes for representing and rendering a scene on a cubic panorama (CP). It sophisticatedly converts a complicated three-dimensional triangulation into a simple three-step triangulation. First, a two-dimensional Delaunay triangulation is individually carried out on each face. Second, an improved polygonal triangulation is implemented in the intermediate regions of each of two faces. Third, a cobweblike triangulation is designed for the remaining intermediate regions after unfolding four faces to the top/bottom face. Since the last two steps well solve the boundary problem arising from cube edges, the triangulation with irregular-distribution feature points is implemented in a CP as a whole. The triangular meshes can be warped from multiple reference CPs onto an arbitrary viewpoint by face-to-face homography transformations. The experiments indicate that the proposed triangulation approach provides a good modeling for the scene with photorealistic rendered CPs.
Depinning transition and thermal fluctuations in the random-field Ising model.
Roters, L; Hucht, A; Lübeck, S; Nowak, U; Usadel, K D
1999-11-01
We analyze the depinning transition of a driven interface in the three-dimensional (3D) random field Ising model (RFIM) with quenched disorder by means of Monte Carlo simulations. The interface initially built into the system is perpendicular to the [111] direction of a simple cubic lattice. We introduce an algorithm which is capable of simulating such an interface independent of the considered dimension and time scale. This algorithm is applied to the 3D RFIM to study both the depinning transition and the influence of thermal fluctuations on this transition. It turns out that in the RFIM characteristics of the depinning transition depend crucially on the existence of overhangs. Our analysis yields critical exponents of the interface velocity, the correlation length, and the thermal rounding of the transition. We find numerical evidence for a scaling relation for these exponents and the dimension d of the system.
Renyi Correlations and Phase Transitions in the Transverse-Field Ising model
Singh, Rajiv; Devakul, Trithep
2015-03-01
We calculate T = 0 spin-spin correlation functions with respect to a probability distribution given by an integer power (n) of the reduced density matrix ρcirc;A, when a transverse-field Ising model (TFIM) system is bipartitioned by a planar interface. Using series expansion methods these calculations are done in the thermodynamic limit for arbitrary positive integer n, with n = 1 giving us the bulk correlations. We study the TFIM system on isotropic and anisotropic simple-cubic lattices. We examine the evidence for whether the critical point of the transition deviates from the bulk critical point as a function of n and whether the critical behavior lies in the 2 D or 4 D Ising universality classes as would be expected from a surface transition at finite temperature and a T = 0 bulk transition, respectively. Work supported in part by NSF Grant Number DMR-1306048.
Optimization Models for Petroleum Field Exploitation
Energy Technology Data Exchange (ETDEWEB)
Jonsbraaten, Tore Wiig
1998-12-31
This thesis presents and discusses various models for optimal development of a petroleum field. The objective of these optimization models is to maximize, under many uncertain parameters, the project`s expected net present value. First, an overview of petroleum field optimization is given from the point of view of operations research. Reservoir equations for a simple reservoir system are derived and discretized and included in optimization models. Linear programming models for optimizing production decisions are discussed and extended to mixed integer programming models where decisions concerning platform, wells and production strategy are optimized. Then, optimal development decisions under uncertain oil prices are discussed. The uncertain oil price is estimated by a finite set of price scenarios with associated probabilities. The problem is one of stochastic mixed integer programming, and the solution approach is to use a scenario and policy aggregation technique developed by Rockafellar and Wets although this technique was developed for continuous variables. Stochastic optimization problems with focus on problems with decision dependent information discoveries are also discussed. A class of ``manageable`` problems is identified and an implicit enumeration algorithm for finding optimal decision policy is proposed. Problems involving uncertain reservoir properties but with a known initial probability distribution over possible reservoir realizations are discussed. Finally, a section on Nash-equilibrium and bargaining in an oil reservoir management game discusses the pool problem arising when two lease owners have access to the same underlying oil reservoir. Because the oil tends to migrate, both lease owners have incentive to drain oil from the competitors part of the reservoir. The discussion is based on a numerical example. 107 refs., 31 figs., 14 tabs.
An effective packing density of binary cubic crystals
Eremin, I. E.; Eremina, V. V.; Sychev, M. S.; Moiseenko, V. G.
2015-04-01
The methodology of effective macroscopic calculation of numerical values of internuclear distances in binary crystals of a cubic crystal system is based on the use of coefficients of the structural packing density of the crystal lattice. The possibility of combining the reference data on the main physicochemical parameters of the substance is implemented by synthesis of the corresponding mathematical models.
Trace spaces in a pre-cubical complex
DEFF Research Database (Denmark)
Raussen, Martin
In directed algebraic topology, (spaces of) directed irreversible (d)-paths are studied from a topological and from a categorical point of view. Motivated by models for concurrent computation, we study in this paper spaces of d-paths in a pre-cubical complex. Such paths are equipped with a natural...
Heisenberg Model in a Rotating Magnetic Field
Institute of Scientific and Technical Information of China (English)
LIN Qiong-Gui
2005-01-01
We study the Heisenberg model under the influence of a rotating magnetic field. By using a time-dependent unitary transformation, the time evolution operator for the Schrodinger equation is obtained, which involves no chronological product. The spin vectors (mean values of the spin operators) are obtained as explicit functions of time in the most general case. A series of cyclic solutions are presented. The nonadiabatic geometric phases of these cyclic solutions are calculated, and are expressed in terms of the solid angle subtended by the closed trace of the total spin vector, as well as in terms of those of the individual spins.
A matrix model from string field theory
Directory of Open Access Journals (Sweden)
Syoji Zeze
2016-09-01
Full Text Available We demonstrate that a Hermitian matrix model can be derived from level truncated open string field theory with Chan-Paton factors. The Hermitian matrix is coupled with a scalar and U(N vectors which are responsible for the D-brane at the tachyon vacuum. Effective potential for the scalar is evaluated both for finite and large N. Increase of potential height is observed in both cases. The large $N$ matrix integral is identified with a system of N ZZ branes and a ghost FZZT brane.
Geomagnetic Core Field Secular Variation Models
DEFF Research Database (Denmark)
Gillet, N.; Lesur, V.; Olsen, Nils
2010-01-01
We analyse models describing time changes of the Earth’s core magnetic field (secular variation) covering the historical period (several centuries) and the more recent satellite era (previous decade), and we illustrate how both the information contained in the data and the a priori information...... highlight the difficulty of resolving the time variability of the high degree secular variation coefficients (i.e. the secular acceleration), arising for instance from the challenge to properly separate sources of internal and of external origin. In addition, the regularisation process may also result...
A matrix model from string field theory
Zeze, Syoji
2016-09-01
We demonstrate that a Hermitian matrix model can be derived from level truncated open string field theory with Chan-Paton factors. The Hermitian matrix is coupled with a scalar and U(N) vectors which are responsible for the D-brane at the tachyon vacuum. Effective potential for the scalar is evaluated both for finite and large N. Increase of potential height is observed in both cases. The large N matrix integral is identified with a system of N ZZ branes and a ghost FZZT brane.
Model-checking mean-field models: algorithms & applications
Kolesnichenko, Anna Victorovna
2014-01-01
Large systems of interacting objects are highly prevalent in today's world. In this thesis we primarily address such large systems in computer science. We model such large systems using mean-field approximation, which allows to compute the limiting behaviour of an infinite population of identical o
Computer Forensics Field Triage Process Model
Directory of Open Access Journals (Sweden)
Marcus K. Rogers
2006-06-01
Full Text Available With the proliferation of digital based evidence, the need for the timely identification, analysis and interpretation of digital evidence is becoming more crucial. In many investigations critical information is required while at the scene or within a short period of time - measured in hours as opposed to days. The traditional cyber forensics approach of seizing a system(s/media, transporting it to the lab, making a forensic image(s, and then searching the entire system for potential evidence, is no longer appropriate in some circumstances. In cases such as child abductions, pedophiles, missing or exploited persons, time is of the essence. In these types of cases, investigators dealing with the suspect or crime scene need investigative leads quickly; in some cases it is the difference between life and death for the victim(s. The Cyber Forensic Field Triage Process Model (CFFTPM proposes an onsite or field approach for providing the identification, analysis and interpretation of digital evidence in a short time frame, without the requirement of having to take the system(s/media back to the lab for an in-depth examination or acquiring a complete forensic image(s. The proposed model adheres to commonly held forensic principles, and does not negate the ability that once the initial field triage is concluded, the system(s/storage media be transported back to a lab environment for a more thorough examination and analysis. The CFFTPM has been successfully used in various real world cases, and its investigative importance and pragmatic approach has been amply demonstrated. Furthermore, the derived evidence from these cases has not been challenged in the court proceedings where it has been introduced. The current article describes the CFFTPM in detail, discusses the model’s forensic soundness, investigative support capabilities and practical considerations.
Stability of the high-pressure body-centered-cubic phase of helium
Frenkel, D.
1986-01-01
This paper report absolute free-energy calculations of the fluid, body-centered-cubic, and face-centered-cubic phases of helium at T=327.04 K. We find that at and around this temperature the model potential proposed by Aziz et al. doe not yield a stable bcc phase. Quantum corrections do not alter th
Stability of the high-pressure body-centered-cubic phase of helium
Frenkel, D.
1987-01-01
This paper report absolute free-energy calculations of the fluid, body-centered-cubic, and face-centered-cubic phases of helium at T=327.04 K. We find that at and around this temperature the model potential proposed by Aziz et al. doe not yield a stable bcc phase. Quantum corrections do not alter this conclusion
DEFF Research Database (Denmark)
Arya, Alay; Liang, Xiaodong; von Solms, Nicolas
2016-01-01
: All three models require the same number of experimental data points (at least three upper onset pressures and one bubble pressure) in order to obtain model parameters.:Different types of asphaltene phase behavior for different reservoir fluids, where asphaltene solubility either decreases...... this study. The sensitivity of SARA data to the modeling approach based On PC-SAFT (WOA) is also analyzed. Finally, the relationship between the binary interaction parameter of the asphaltene-CO2 pair and crossover temperature, below which asphaltene solubility increases in reservoir fluid, with CO2 gas...
A domino model for geomagnetic field reversals
Mori, N; Ferriz-Mas, A; Wicht, J; Mouri, H; Nakamichi, A; Morikawa, M
2011-01-01
We solve the equations of motion of a one-dimensional planar Heisenberg (or Vaks-Larkin) model consisting of a system of interacting macro-spins aligned along a ring. Each spin has unit length and is described by its angle with respect to the rotational axis. The orientation of the spins can vary in time due to random forcing and spin-spin interaction. We statistically describe the behaviour of the sum of all spins for different parameters. The term "domino model" in the title refers to the interaction among the spins. We compare the model results with geomagnetic field reversals and find strikingly similar behaviour. The aggregate of all spins keeps the same direction for a long time and, once in a while, begins flipping to change the orientation by almost 180 degrees (mimicking a geomagnetic reversal) or to move back to the original direction (mimicking an excursion). Most of the time the spins are aligned or anti-aligned and deviate only slightly with respect to the rotational axis (mimicking the secular v...
Water Modeling of Optimizing Tundish Flow Field
Institute of Scientific and Technical Information of China (English)
LIU Jin-gang; YAN Hui-cheng; LIU Liu; WANG Xin-hua
2007-01-01
In the water modeling experiments, three cases were considered, i.e. , a bare tundish, a tundish equipped with a turbulence inhibitor, and a rectangular tundish equipped with weirs (dams) and a turbulence inhibitor. Comparing the RTD curves, inclusion separation, and the result of the streamline experiment, it can be found that the tundish equipped with weirs (dams) and a turbulence inhibitor has a great effect on the flow field and the inclusion separation when compared with the sole use or no use of the turbulent inhibitor or weirs (dams). In addition, the enlargement of the distance between the weir and dam will result in a better effect when the tundish equipped with weirs (dam) and a turbulence inhibitor was used.
Ultrahard nanotwinned cubic boron nitride.
Tian, Yongjun; Xu, Bo; Yu, Dongli; Ma, Yanming; Wang, Yanbin; Jiang, Yingbing; Hu, Wentao; Tang, Chengchun; Gao, Yufei; Luo, Kun; Zhao, Zhisheng; Wang, Li-Min; Wen, Bin; He, Julong; Liu, Zhongyuan
2013-01-17
Cubic boron nitride (cBN) is a well known superhard material that has a wide range of industrial applications. Nanostructuring of cBN is an effective way to improve its hardness by virtue of the Hall-Petch effect--the tendency for hardness to increase with decreasing grain size. Polycrystalline cBN materials are often synthesized by using the martensitic transformation of a graphite-like BN precursor, in which high pressures and temperatures lead to puckering of the BN layers. Such approaches have led to synthetic polycrystalline cBN having grain sizes as small as ∼14 nm (refs 1, 2, 4, 5). Here we report the formation of cBN with a nanostructure dominated by fine twin domains of average thickness ∼3.8 nm. This nanotwinned cBN was synthesized from specially prepared BN precursor nanoparticles possessing onion-like nested structures with intrinsically puckered BN layers and numerous stacking faults. The resulting nanotwinned cBN bulk samples are optically transparent with a striking combination of physical properties: an extremely high Vickers hardness (exceeding 100 GPa, the optimal hardness of synthetic diamond), a high oxidization temperature (∼1,294 °C) and a large fracture toughness (>12 MPa m(1/2), well beyond the toughness of commercial cemented tungsten carbide, ∼10 MPa m(1/2)). We show that hardening of cBN is continuous with decreasing twin thickness down to the smallest sizes investigated, contrasting with the expected reverse Hall-Petch effect below a critical grain size or the twin thickness of ∼10-15 nm found in metals and alloys.
Cubic III-nitrides: potential photonic materials
Onabe, K.; Sanorpim, S.; Kato, H.; Kakuda, M.; Nakamura, T.; Nakamura, K.; Kuboya, S.; Katayama, R.
2011-01-01
The growth and characterization of some cubic III-nitride films on suitable cubic substrates have been done, namely, c- GaN on GaAs by MOVPE, c-GaN and c-AlGaN on MgO by RF-MBE, and c-InN and c-InGaN (In-rich) on YSZ by RFMBE. This series of study has been much focused on the cubic-phase purity as dependent on the respective growth conditions and resulting electrical and optical properties. For c-GaN and c-InN films, a cubic-phase purity higher than 95% is attained in spite of the metastable nature of the cubic III-nitrides. However, for c-AlGaN and c-InGaN films, the cubic-phase purity is rapidly degraded with significant incorporation of the hexagonal phase through stacking faults on cubic {111} faces which may be exposed on the roughened growing or substrate surface. It has been shown that the electron mobilities in c-GaN and c-AlGaN films are much related to phase purity.
Energy Technology Data Exchange (ETDEWEB)
Almasi, Mohammad, E-mail: m.almasi@khouzestan.srbiau.ac.ir [Department of Chemistry, Science and Research Branch, Islamic Azad University, Khouzestan (Iran, Islamic Republic of)
2013-03-01
Densities and viscosities for binary mixtures of dimethyl carbonate with 2-propanol up to 2-heptanol were measured at various temperatures and ambient pressure. From experimental data, excess molar volumes, V{sub m}{sup E}. were calculated and correlated by the Redlich–Kister equation to obtain the binary coefficients and the standard deviations. Excess molar volumes, V{sub m}{sup E}, are positive for all studied mixtures over the entire range of the mole fraction. The ERAS-model has been applied for describing the binary excess molar volumes and also Peng–Robinson–Stryjek–Vera (PRSV) equation of state (EOS) has been used to predict the binary excess molar volumes and viscosities. Also several semi-empirical models were used to correlate the viscosity of binary mixtures.
Institute of Scientific and Technical Information of China (English)
Xu Quan; Tian Qiang
2009-01-01
This paper discusses the two-dimensional discrete monatomic Fermi-Pasta-Ulam lattice, by using the method of multiple-scale and the quasi-discreteness approach. By taking into account the interaction between the atoms in the lattice and their nearest neighbours, it obtains some classes of two-dimensional local models as follows: two-dimensional bright and dark discrete soliton trains, two-dimensional bright and dark line discrete breathers, and two-dimensional bright and dark discrete breather.
DEFF Research Database (Denmark)
Cismondi, Martin; Mollerup, Jørgen M.; Zabaloy, Marcelo S.
2010-01-01
interaction parameters) in modern equations of state.In particular, the phase equilibria of binary mixtures containing CO2 and heavy n-alkanes have been studied by an important number of authors and using different types of models, achieving only partially accurate results and realizing the difficulties...... for the first time a quite successful complete description of asymmetric CO2+n-alkane binary systems, with n-alkane carbon number from 14 to 22....
Near-field/altered-zone models report
Energy Technology Data Exchange (ETDEWEB)
Hardin, E. L., LLNL
1998-03-01
nonlithophysal and lower lithophysal units. These units are made up of moderately to densely welded, devitrified, fractured tuff. The rock's chemical composition is comparable to that of typical granite, but has textural features and mineralogical characteristics of large-scale, silicic volcanism. Because the repository horizon will be approximately 300 m below the ground surface and 200 m above the water table, the repository will be partially saturated. The welded tuff matrix in the host units is highly impermeable, but water and gas flow readily through fractures. The degree of fracturing in these units is highly variable, and the hydrologic significance of fracturing is an important aspect of site investigation. This report describes the characterization and modeling of a region around the potential repository--the altered zone--a region in which the temperature will be increased significantly by waste-generated heat. Numerical simulation has shown that, depending on the boundary conditions, rock properties, and repository design features incorporated in the models, the altered zone (AZ) may extend from the water table to the ground surface. This report also describes models of the near field, the region comprising the repository emplacement drifts and the surrounding rock, which are critical to the performance of engineered components. Investigations of near-field and altered-zone (NF/AZ) processes support the design of underground repository facilities and engineered barriers and also provide constraint data for probabilistic calculations of waste-isolation performance (i.e., performance assessment). The approach to investigation, which is an iterative process involving hypothesis testing and experimentation, has relied on conceptualizing engineered barriers and on performance analysis. This report is a collection, emphasizing conceptual and numerical models, of the recent results contributed from studies of NF/AZ processes and of quantitative measures of NF
Near-field/altered-zone models report
Energy Technology Data Exchange (ETDEWEB)
Hardin, E. L., LLNL
1998-03-01
nonlithophysal and lower lithophysal units. These units are made up of moderately to densely welded, devitrified, fractured tuff. The rock's chemical composition is comparable to that of typical granite, but has textural features and mineralogical characteristics of large-scale, silicic volcanism. Because the repository horizon will be approximately 300 m below the ground surface and 200 m above the water table, the repository will be partially saturated. The welded tuff matrix in the host units is highly impermeable, but water and gas flow readily through fractures. The degree of fracturing in these units is highly variable, and the hydrologic significance of fracturing is an important aspect of site investigation. This report describes the characterization and modeling of a region around the potential repository--the altered zone--a region in which the temperature will be increased significantly by waste-generated heat. Numerical simulation has shown that, depending on the boundary conditions, rock properties, and repository design features incorporated in the models, the altered zone (AZ) may extend from the water table to the ground surface. This report also describes models of the near field, the region comprising the repository emplacement drifts and the surrounding rock, which are critical to the performance of engineered components. Investigations of near-field and altered-zone (NF/AZ) processes support the design of underground repository facilities and engineered barriers and also provide constraint data for probabilistic calculations of waste-isolation performance (i.e., performance assessment). The approach to investigation, which is an iterative process involving hypothesis testing and experimentation, has relied on conceptualizing engineered barriers and on performance analysis. This report is a collection, emphasizing conceptual and numerical models, of the recent results contributed from studies of NF/AZ processes and of quantitative measures of NF
Rapid 3-D forward modeling of gravity and gravity gradient tensor fields
Longwei, C.; Dai, S.; Zhang, Q.
2014-12-01
Three-dimensional inversion are the key process in gravity exploration. In the commonly used scheme of inversion, the subsurface of the earth is usually divided into many small prism blocks (or grids) with variable density values. A key task in gravity inversion is to calculate the composite fields (gravity and gravity gradient tensor) generated by all these grids, this is known as forward modeling. In general forward modeling is memory-demanding and time-consuming. One scheme to rapidly calculate the fields is to implement it in Fourier domain and use fast Fourier transform algorithm. The advantage of the Fourier domain method is, obviously, much faster. However, the intrinsic edge effect of the Fourier domain method degrades the precision of the calculated fields. We have developed an innovative scheme to directly calculate the fields in spatial domain. There are two key points in this scheme. One key point is spatial discretization. Spatial convolution formula is discretized using an approach similar to normal difference method. A key idea during discretization is to use the analytical formula of a cubic prism, and this makes the resultant discrete formula have clear physical meaning: it embodies the superposition principle of the fields and is the exact formula to calculate the fields generated by all grids. The discretization only requires the grids have the same dimension in horizontal directions, and grids in different layers may have different dimension in vertical direction, and this offers more flexibility for inversion. Another key point is discrete convolution calculation. We invoke a high efficient two-dimensional discrete convolution algorithm, and it guarantees both time-saving and memory-saving. Its memory cost has the same order as the number of grids. Numerical test result shows that for a model with a dimension of 1000x1000x201 grids, it takes about 300s to calculate the fields on 1000x1000 field points in a personal computer with 3.4-GHz CPU
Model for predicting mountain wave field uncertainties
Damiens, Florentin; Lott, François; Millet, Christophe; Plougonven, Riwal
2017-04-01
Studying the propagation of acoustic waves throughout troposphere requires knowledge of wind speed and temperature gradients from the ground up to about 10-20 km. Typical planetary boundary layers flows are known to present vertical low level shears that can interact with mountain waves, thereby triggering small-scale disturbances. Resolving these fluctuations for long-range propagation problems is, however, not feasible because of computer memory/time restrictions and thus, they need to be parameterized. When the disturbances are small enough, these fluctuations can be described by linear equations. Previous works by co-authors have shown that the critical layer dynamics that occur near the ground produces large horizontal flows and buoyancy disturbances that result in intense downslope winds and gravity wave breaking. While these phenomena manifest almost systematically for high Richardson numbers and when the boundary layer depth is relatively small compare to the mountain height, the process by which static stability affects downslope winds remains unclear. In the present work, new linear mountain gravity wave solutions are tested against numerical predictions obtained with the Weather Research and Forecasting (WRF) model. For Richardson numbers typically larger than unity, the mesoscale model is used to quantify the effect of neglected nonlinear terms on downslope winds and mountain wave patterns. At these regimes, the large downslope winds transport warm air, a so called "Foehn" effect than can impact sound propagation properties. The sensitivity of small-scale disturbances to Richardson number is quantified using two-dimensional spectral analysis. It is shown through a pilot study of subgrid scale fluctuations of boundary layer flows over realistic mountains that the cross-spectrum of mountain wave field is made up of the same components found in WRF simulations. The impact of each individual component on acoustic wave propagation is discussed in terms of
Regional gravity field modelling from GOCE observables
Pitoňák, Martin; Šprlák, Michal; Novák, Pavel; Tenzer, Robert
2017-01-01
In this article we discuss a regional recovery of gravity disturbances at the mean geocentric sphere approximating the Earth over the area of Central Europe from satellite gravitational gradients. For this purpose, we derive integral formulas which allow converting the gravity disturbances onto the disturbing gravitational gradients in the local north-oriented frame (LNOF). The derived formulas are free of singularities in case of r ≠ R . We then investigate three numerical approaches for solving their inverses. In the initial approach, the integral formulas are firstly modified for solving individually the near- and distant-zone contributions. While the effect of the near-zone gravitational gradients is solved as an inverse problem, the effect of the distant-zone gravitational gradients is computed by numerical integration from the global gravitational model (GGM) TIM-r4. In the second approach, we further elaborate the first scenario by reducing measured gravitational gradients for gravitational effects of topographic masses. In the third approach, we apply additional modification by reducing gravitational gradients for the reference GGM. In all approaches we determine the gravity disturbances from each of the four accurately measured gravitational gradients separately as well as from their combination. Our regional gravitational field solutions are based on the GOCE EGG_TRF_2 gravitational gradients collected within the period from November 1 2009 until January 11 2010. Obtained results are compared with EGM2008, DIR-r1, TIM-r1 and SPW-r1. The best fit, in terms of RMS (2.9 mGal), is achieved for EGM2008 while using the third approach which combine all four well-measured gravitational gradients. This is explained by the fact that a-priori information about the Earth's gravitational field up to the degree and order 180 was used.
Institute of Scientific and Technical Information of China (English)
郭灿; 王锦程; 王志军; 李俊杰; 郭耀麟; 唐赛
2015-01-01
通过在自由能泛函中引入各向异性参数得到了一个基于高斯内核的改进晶体相场模型，并采用该模型研究了体心立方结构(BCC)枝晶生长的原子堆垛过程。结果表明，在BCC由正十二面体平衡形貌演化为枝晶组织过程中，形核位置经历了由面心({110}面)到尖端(⟨100⟩取向)的转移，进而发生界面失稳形成枝晶组织；枝晶生长过程中，新的固相原子首先在枝晶尖端附近形核，并快速向尖端及根部生长，枝晶尖端被新原子完全包覆后将再次诱发液相原子附着形核及生长；随初始液相密度的增加，固-液界面移动速率增加，速率系数的各向异性也增强。%On the basis of the Gaussian kernel phase field crystal model (PFC), we propose a modified PFC model. The atom-attaching process of three-dimensional body-center-cubic (BCC) dendritic growth is examined by using the modified PFC model. Our simulations indicate that in the process of the morphology evolution from regular dodecahedron to dendrite shape, the nucleation position of new layer is transferred from the center of {110} planes into the region of{110}plane near the⟨100⟩tips, and then the BCC dendritic morphology is obtained. In the process of dendritic growth, first, new solid atom absorption takes place near dendrite tips, then liquid atoms start to grow up on the existing solid phase rapidly. After the dendrite tips are completely occupied by new atoms, new nuclei begin to form again. Increasing the initial atom density n will increase the velocity coeﬃcient C and the anisotropy of C.
Bag model for DNA migration during pulsed-field electrophoresis.
Chu, G
1991-01-01
A model for pulsed-field electrophoresis was developed by picturing large DNA as a deformable "bag" that (i) moves with limiting mobility in a continuous electric field, (ii) adopts an orientation aligned with the field direction, and (iii) reorients after a change in field direction in a size-dependent manner. The model correctly predicted the resolution of large DNA in a pulsed field including the surprising phenomena of mobility inversion, lateral band spreading, and improved resolution fo...
DEFF Research Database (Denmark)
Finlay, Chris; Olsen, Nils; Gillet, Nicolas
We present a new ensemble of time-dependent magnetic field models constructed from satellite and observatory data spanning 1997-2013 that are compatible with prior information concerning the temporal spectrum of core field variations. These models allow sharper field changes compared to traditional....... We report spherical harmonic spectra, comparisons to observatory monthly means, and maps of the radial field at the core-mantle boundary, from the resulting ensemble of core field models. We find that inter-annual fluctuations in the external field (for example related to high solar-driven activity...
DEFF Research Database (Denmark)
Tsivintzelis, Ioannis; Ali, Shahid; Kontogeorgis, Georgios
2014-01-01
density data for both CO2 and CO2–water and for vapor–liquid equilibrium for mixtures of CO2 with various compounds present in transport systems. In all of these cases we consider various possibilities for modeling CO2 (inert, self-associating using two-, three-, and four sites) and the possibility...... of cross-association with water. Finally, we evaluate the predictive performance of CPA for multicomponent CO2 mixtures in transport systems which also include water, methane, and H2S. The results are compared to both experimental data and selected other approaches from literature. The results...... of CO2 with water is accounted for or when CO2 is considered to be a self-associating molecule (with three or four sites). The final choice on the best approach requires investigating a much larger set of mixtures including also alcohols and glycols, which will be considered in future works....
MOVING SCREW DISLOCATION IN CUBIC QUASICRYSTAL
Institute of Scientific and Technical Information of China (English)
ZHOU Wang-min; SONG Yu-hai
2005-01-01
The elasticity theory of the dislocation of cubic quasicrystals is developed.The governing equations of anti-plane elasticity dynamics problem of the quasicrystals were reduced to a solution of wave equations by introducing displacement functions,and the analytical expressions of displacements, stresses and energies induced by a moving screw dislocation in the cubic quasicrystalline and the velocity limit of the dislocation were obtained. These provide important information for studying the plastic deformation of the new solid material.
2-rational Cubic Spline Involving Tension Parameters
Indian Academy of Sciences (India)
M Shrivastava; J Joseph
2000-08-01
In the present paper, 1-piecewise rational cubic spline function involving tension parameters is considered which produces a monotonic interpolant to a given monotonic data set. It is observed that under certain conditions the interpolant preserves the convexity property of the data set. The existence and uniqueness of a 2-rational cubic spline interpolant are established. The error analysis of the spline interpolant is also given.
Semisymmetric Cubic Graphs of Order 162
Indian Academy of Sciences (India)
Mehdi Alaeiyan; Hamid A Tavallaee; B N Onagh
2010-02-01
An undirected graph without isolated vertices is said to be semisymmetric if its full automorphism group acts transitively on its edge set but not on its vertex set. In this paper, we inquire the existence of connected semisymmetric cubic graphs of order 162. It is shown that for every odd prime , there exists a semisymmetric cubic graph of order 162 and its structure is explicitly specified by giving the corresponding voltage rules generating the covering projections.
Cubical version of combinatorial differential forms
DEFF Research Database (Denmark)
Kock, Anders
2010-01-01
The theory of combinatorial differential forms is usually presented in simplicial terms. We present here a cubical version; it depends on the possibility of forming affine combinations of mutual neighbour points in a manifold, in the context of synthetic differential geometry.......The theory of combinatorial differential forms is usually presented in simplicial terms. We present here a cubical version; it depends on the possibility of forming affine combinations of mutual neighbour points in a manifold, in the context of synthetic differential geometry....
Parameter estimation of hidden periodic model in random fields
Institute of Scientific and Technical Information of China (English)
何书元
1999-01-01
Two-dimensional hidden periodic model is an important model in random fields. The model is used in the field of two-dimensional signal processing, prediction and spectral analysis. A method of estimating the parameters for the model is designed. The strong consistency of the estimators is proved.
Quantum spectra and classical periodic orbit in the cubic billiard
Institute of Scientific and Technical Information of China (English)
Dehua Wang; Yongjiang Yu; Shenglu Lin
2006-01-01
Quantum billiards have attracted much interest in many fields. People have made a lot of researches on the two-dimensional (2D) billiard systems. Contrary to the 2D billiard, due to the complication of its classical periodic orbits, no one has studied the correspondence between the quantum spectra and the classical orbits of the three-dimensional (3D) billiards. Taking the cubic billiard as an example, using the periodic orbit theory, we find the periodic orbit of the cubic billiard and study the correspondence between the quantum spectra and the length of the classical orbits in 3D system. The Fourier transformed spectrum of this system has allowed direct comparison between peaks in such plot and the length of the periodic orbits, which verifies the correctness of the periodic orbit theory. This is another example showing that semiclassical method provides a bridge between quantum and classical mechanics.
Quantum Phase Transitions in Anti-ferromagnetic Planar Cubic Lattices
Wellard, C J; Wellard, Cameron; Orus, Roman
2004-01-01
Motivated by its relation to an NP-hard problem we analyze the ground state properties of anti-ferromagnetic Ising-spin networks in planar cubic lattices under the action of homogeneous transverse and longitudinal magnetic fields. We consider different instances of the cubic geometry and find a set of quantum phase transitions for each one of the systems, which we characterize by means of entanglement behavior and majorization theory. Entanglement scaling at the critical region is in agreement with results arising from conformal symmetry, therefore even the simplest planar systems can display very large amounts of quantum correlation. No conclusion can be made as to the scaling behavior of the minimum energy gap, with the data allowing equally good fits to exponential and power law decays. Analysis of entanglement and especially of majorization instead of the energy spectrum proves to be a good way of detecting quantum phase transitions in highly frustrated configurations.
Quantum correlated cluster mean-field theory applied to the transverse Ising model.
Zimmer, F M; Schmidt, M; Maziero, Jonas
2016-06-01
Mean-field theory (MFT) is one of the main available tools for analytical calculations entailed in investigations regarding many-body systems. Recently, there has been a surge of interest in ameliorating this kind of method, mainly with the aim of incorporating geometric and correlation properties of these systems. The correlated cluster MFT (CCMFT) is an improvement that succeeded quite well in doing that for classical spin systems. Nevertheless, even the CCMFT presents some deficiencies when applied to quantum systems. In this article, we address this issue by proposing the quantum CCMFT (QCCMFT), which, in contrast to its former approach, uses general quantum states in its self-consistent mean-field equations. We apply the introduced QCCMFT to the transverse Ising model in honeycomb, square, and simple cubic lattices and obtain fairly good results both for the Curie temperature of thermal phase transition and for the critical field of quantum phase transition. Actually, our results match those obtained via exact solutions, series expansions or Monte Carlo simulations.
A model to localize gauge fields on thick branes
Chumbes, A E R; Hott, M B
2011-01-01
It is shown that the introduction of a suitable function in the higher dimensional gauge field action may be used in order to achieve gauge bosons localization on a thick brane. The model is constructed upon analogies to the effective coupling of neutral scalar field to electromagnetic field and to the Friedberg-Lee model for hadrons.
A physical data model for fields and agents
de Jong, Kor; de Bakker, Merijn; Karssenberg, Derek
2016-04-01
Two approaches exist in simulation modeling: agent-based and field-based modeling. In agent-based (or individual-based) simulation modeling, the entities representing the system's state are represented by objects, which are bounded in space and time. Individual objects, like an animal, a house, or a more abstract entity like a country's economy, have properties representing their state. In an agent-based model this state is manipulated. In field-based modeling, the entities representing the system's state are represented by fields. Fields capture the state of a continuous property within a spatial extent, examples of which are elevation, atmospheric pressure, and water flow velocity. With respect to the technology used to create these models, the domains of agent-based and field-based modeling have often been separate worlds. In environmental modeling, widely used logical data models include feature data models for point, line and polygon objects, and the raster data model for fields. Simulation models are often either agent-based or field-based, even though the modeled system might contain both entities that are better represented by individuals and entities that are better represented by fields. We think that the reason for this dichotomy in kinds of models might be that the traditional object and field data models underlying those models are relatively low level. We have developed a higher level conceptual data model for representing both non-spatial and spatial objects, and spatial fields (De Bakker et al. 2016). Based on this conceptual data model we designed a logical and physical data model for representing many kinds of data, including the kinds used in earth system modeling (e.g. hydrological and ecological models). The goal of this work is to be able to create high level code and tools for the creation of models in which entities are representable by both objects and fields. Our conceptual data model is capable of representing the traditional feature data
Theoretical and Experimental Study of Time Reversal in Cubic Crystals
Institute of Scientific and Technical Information of China (English)
陆铭慧; 张碧星; 汪承灏
2004-01-01
The self-adaptive focusing of the time reversal in anisotropic media is studied theoretically and experimentally. It is conducted for the compressional wave field in the cubic crystal silicon. The experimental result is in agreement with our theoretical analysis. The focusing gain and the displacement distributions of the time reversal field are analysed in detail. It is shown that the waves from different elements of the transducer array arrive at the original place of the source simultaneously after the time reversal operation. The waveform distortions caused by the velocity anisotropy can automatically be compensated for after the time reversal processing.
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.
Campuzano, Saioa A.; Gómez-Paccard, Miriam; Pavón-Carrasco, Francisco Javier; Osete, María Luisa
2016-04-01
The knowledge of the ancient Earth's magnetic field is crucial to understand its origin and future evolution. In this context, the palaeomagnetic studies provide useful information about the past geomagnetic field registered in rocks, lava flows, sediments or archaeological materials. The continuous upgrade of the palaeomagnetic database during the last decade has allowed the generation of global geomagnetic field models based on different palaeomagnetic data and techniques (such as the SHA.DIF.14K, ARCH3K.1, CALS3K.4b, pfm9k.1a models, among others). Some recent studies have pointed out that the archaeointensity database might not be reliable enough, by observing high scatter in the records. Here, we present a new global geomagnetic model for the last 2000 years, SHAQ2K, based on high quality archaeomagnetic and volcanic intensity data. For this purpose we classify the palaeointensity data in two quality categories following widely accepted palaeomagnetic criteria based on the methodology used during the laboratory treatment of the samples and on the number of specimens finally used to calculate the mean intensities. Respect to the modelling process, we use the spherical harmonic analysis in space and cubic b-splines in time, also applying a spatial and temporal regularization which minimizes the energy of the geomagnetic field at the core-mantle boundary. The implications of the differences between this new model and other previously published global geomagnetic models are discussed.
Experimental core electron density of cubic boron nitride
DEFF Research Database (Denmark)
Wahlberg, Nanna; Bindzus, Niels; Bjerg, Lasse
candidate because of its many similarities with diamond: bonding pattern in the extended network structure, hardness, and the quality of the crystallites.3 However, some degree ionic interaction is a part of the bonding in boron nitride, which is not present in diamond. By investigating the core density...... beyond multipolar modeling of the valence density. As was recently shown in a benchmark study of diamond by Bindzus et al.1 The next step is to investigate more complicated chemical bonding motives, to determine the effect of bonding on the core density. Cubic boron nitride2 lends itself as a perfect...... in boron nitride we may obtain a deeper understanding of the effect of bonding on the total density. We report here a thorough investigation of the charge density of cubic boron nitride with a detailed modelling of the inner atom charge density. By combining high resolution powder X-ray diffraction data...
HOSHI, Akinari; Miyake, Katsuya
2007-01-01
We study the field isomorphism problem for a cubic generic polynomial $X^3+sX+s$ via Tschirnhausen transformation. Through this process, there naturally appears a $2$-dimensional involutive Cremona transformation. We show that the fixed field under the action of the transformation is purely transcendental over an arbitrary base field.
Model to localize gauge and tensor fields on thick branes
Chumbes, A. E. R.; Hoff da Silva, J. M.; Hott, M. B.
2012-04-01
It is shown that the introduction of a suitable function in the higher-dimensional gauge field action may be used in order to achieve gauge bosons localization on a thick brane. The model is constructed upon analogies to the effective coupling of neutral scalar field to electromagnetic field and to the Friedberg-Lee model for hadrons. After that we move forward studying the localization of the Kalb-Ramond field via this procedure.
FIELD EXPERIMENTS AND MODELING AT CDG AIRPORTS
Ramaroson, R.
2009-12-01
Richard Ramaroson1,4, Klaus Schaefer2, Stefan Emeis2, Carsten Jahn2, Gregor Schürmann2, Maria Hoffmann2, Mikhael Zatevakhin3, Alexandre Ignatyev3. 1ONERA, Châtillon, France; 4SEAS, Harvard University, Cambridge, USA; 2FZK, Garmisch, Germany; (3)FSUE SPbAEP, St Petersburg, Russia. 2-month field campaigns have been organized at CDG airports in autumn 2004 and summer 2005. Air quality and ground air traffic emissions have been monitored continuously at terminals and taxi-runways, along with meteorological parameters onboard trucks and with a SODAR. This paper analyses the commercial engine emissions characteristics at airports and their effects on gas pollutants and airborne particles coupled to meteorology. LES model results for PM dispersion coupled to microphysics in the PBL are compared to measurements. Winds and temperature at the surface and their vertical profiles have been stored with turbulence. SODAR observations show the time-development of the mixing layer depth and turbulent mixing in summer up to 800m. Active low level jets and their regional extent have been observed and analyzed. PM number and mass size distribution, morphology and chemical contents are investigated. Formation of new ultra fine volatile (UFV) particles in the ambient plume downstream of running engines is observed. Soot particles are mostly observed at significant level at high power thrusts at take-off (TO) and on touch-down whereas at lower thrusts at taxi and aprons ultra the UFV PM emissions become higher. Ambient airborne PM1/2.5 is closely correlated to air traffic volume and shows a maximum beside runways. PM number distribution at airports is composed mainly by volatile UF PM abundant at apron. Ambient PM mass in autumn is higher than in summer. The expected differences between TO and taxi emissions are confirmed for NO, NO2, speciated VOC and CO. NO/NO2 emissions are larger at runways due to higher power. Reactive VOC and CO are more produced at low powers during idling at
Modeling of coastal effluent transport: an approach to linking far-field and near-field models
Institute of Scientific and Technical Information of China (English)
YANG Zhaoqing; KHANGAOKAR Tarang
2008-01-01
One of the challenges in effluent transport modeling in coastal tidal environments is the proper specification of initial dilution in connection with the far-field transport phenomena. An approach of external linkage of far-field and near-field effluent transport models is presented, and applied to simulating the effluent transport in the Port Angeles Harbor, Washington in the Strait of Juan de Fuea. A near-field plume model was used to calculate the effluent initial dilution and a three-dimensional (3-D) hydrodynamic model was developed to simulate the tidal circulation and far-field effluent transport in the Port Angeles Harbor. The hydrodynamic model was driven by tides and surface winds. Observed water surface elevation and velocity data were used to calibrate the model over a period covering the neap-spring tidal cycle. The model was also validated with observed surface drogue trajectory data. The model successfully reproduced the tidal dynamics in the study area and good agreements between model results and observed data were obtained. It is demonstrated that the linkage between the near-field and far-field models in effluent transport modeling can be achieved through iteratively adjusting the model grid sizes such that the dilution ratio and effluent concentration in the circulation model grid cell match the concentration calculated by the near-field plume model.
Relativistic Mean-Field Models and Nuclear Matter Constraints
Dutra, M; Carlson, B V; Delfino, A; Menezes, D P; Avancini, S S; Stone, J R; Providência, C; Typel, S
2013-01-01
This work presents a preliminary study of 147 relativistic mean-field (RMF) hadronic models used in the literature, regarding their behavior in the nuclear matter regime. We analyze here different kinds of such models, namely: (i) linear models, (ii) nonlinear \\sigma^3+\\sigma^4 models, (iii) \\sigma^3+\\sigma^4+\\omega^4 models, (iv) models containing mixing terms in the fields \\sigma and \\omega, (v) density dependent models, and (vi) point-coupling ones. In the finite range models, the attractive (repulsive) interaction is described in the Lagrangian density by the \\sigma (\\omega) field. The isospin dependence of the interaction is modeled by the \\rho meson field. We submit these sets of RMF models to eleven macroscopic (experimental and empirical) constraints, used in a recent study in which 240 Skyrme parametrizations were analyzed. Such constraints cover a wide range of properties related to symmetric nuclear matter (SNM), pure neutron matter (PNM), and both SNM and PNM.
Xiaolong Wang; Yi Wang; Zhizhu Cao; Weizhong Zou; Liping Wang; Guojun Yu; Bo Yu; Jinjun Zhang
2013-01-01
In general, proper orthogonal decomposition (POD) method is used to deal with single-parameter problems in engineering practice, and the linear interpolation is employed to establish the reduced model. Recently, this method is extended to solve the double-parameter problems with the amplitudes being achieved by cubic B-spline interpolation. In this paper, the accuracy of reduced models, which are established with linear interpolation and cubic B-spline interpolation, respectively, is verified...
Fifth generation lithospheric magnetic field model from CHAMP satellite measurements
Maus, S.; Hermann Lühr; Martin Rother; Hemant, K.; Balasis, G.; Patricia Ritter; Claudia Stolle
2007-01-01
Six years of low-orbit CHAMP satellite magnetic measurements have provided an exceptionally high-quality data resource for lithospheric magnetic field modeling and interpretation. Here we describe the fifth-generation satellite-only magnetic field model MF5. The model extends to spherical harmonic degree 100. As a result of careful data selection, extensive corrections, filtering, and line leveling, the model has low noise levels, even if evaluated at the Earth's surface. The model is particu...
Cosmological model with non-minimally coupled fermionic field
Ribas, M O; Kremer, G M
2007-01-01
A model for the Universe is proposed whose constituents are: (a) a dark energy field modeled by a fermionic field non-minimally coupled with the gravitational field, (b) a matter field which consists of pressureless baryonic and dark matter fields and (c) a field which represents the radiation and the neutrinos. The coupled system of Dirac's equations and Einstein field equations is solved numerically by considering a spatially flat homogeneous and isotropic Universe. It is shown that the proposed model can reproduce the expected red-shift behaviors of the deceleration parameter, of the density parameters of each constituent and of the luminosity distance. Furthermore, for small values of the red-shift the constant which couples the fermionic and gravitational fields has a remarkable influence on the density and deceleration parameters.
Testing of a one dimensional model for Field II calibration
DEFF Research Database (Denmark)
Bæk, David; Jensen, Jørgen Arendt; Willatzen, Morten
2008-01-01
to the calibrated Field II program for 1, 4, and 10 cycle excitations. Two parameter sets were applied for modeling, one real valued Pz27 parameter set, manufacturer supplied, and one complex valued parameter set found in literature, Alguer´o et al. [11]. The latter implicitly accounts for attenuation. Results show......Field II is a program for simulating ultrasound transducer fields. It is capable of calculating the emitted and pulse-echoed fields for both pulsed and continuous wave transducers. To make it fully calibrated a model of the transducer’s electro-mechanical impulse response must be included. We...... examine an adapted one dimensional transducer model originally proposed by Willatzen [9] to calibrate Field II. This model is modified to calculate the required impulse responses needed by Field II for a calibrated field pressure and external circuit current calculation. The testing has been performed...
DEFF Research Database (Denmark)
Finlay, Chris; Olsen, Nils; Gillet, Nicolas
. We report spherical harmonic spectra, comparisons to observatory monthly means, and maps of the radial field at the core-mantle boundary, from the resulting ensemble of core field models. We find that inter-annual fluctuations in the external field (for example related to high solar-driven activity...
Structure of the body-centered cubic phase of lipid systems.
Saludjian, P; Reiss-Husson, F
1980-12-01
A new model is proposed for the structure of the body-centered cubic phase of lipid systems. Infinite rods of polar groups (and water) are arranged with axes parallel to the four cubic [unk]1 1 1[unk] directions. The hydrocarbon chains fill the space between the rods to form a continuous matrix. With this unified topology, the model explains satisfactorily the x-ray diffraction patterns of strontium soaps, lecithin, galactolipids, potassium soaps, and hexadecyltrimethylammonium bromide and explains the transition between cubic/H(II) phases. The paradoxical thermal effects on the lipid cubic phase, in particular the decrease of unit cell dimensions with increasing temperature, can be explained with the proposed model by mechanisms similar to those used for the monodimensional and bidimensional (mesomorphic) phases.
Energy Technology Data Exchange (ETDEWEB)
Nakai, T.; Tanahashi, T. [Keio University, Tokyo (Japan). Faculty of Science and Technology
1997-06-25
Generally speaking, the finite-element method in computational fluid dynamics is universally accepted, however computation by the CPU is time-consuming and requires large memory capacity for data storage. Therefore development of an analytical formulation to reduce the time and storage required for calculation is desired. In this paper, we propose a novel discrete del operator method in order to overcome these defects. This method is formulated using the discrete del operator as the element coefficient matrices in finite-element analysis, and low-memory and high-speed calculations are carried out. In particular, we examine whether this method is effective for the numerical analysis of natural convection of thermoelectrically conducting fluids in a cubic cavity. Moreover, we estimate the effect of heat transfer enhancement under a weak magnetic field on the Hartmann number. 13 refs., 5 figs., 6 tabs.
Energy Technology Data Exchange (ETDEWEB)
Lookman, Turab [Los Alamos National Laboratory; Vasseur, Romain [ECOLE NORMALE SUPERIEURE
2009-01-01
We obtain the microstructure of ferroelastic transitions in two and three dimensions from the solution of their corresponding discrete pseudo-spin models. In two dimensions we consider two transitions each from the high symmetry square and triangle symmetries: square-to-rectangle (SR), square-to-oblique (SO), triangle-to-centered rectangle (TR) and triangle-to-oblique (TO). In three dimensions we study the corresponding spin model for the cubic to tetragonal transition. The Landau free energies for these transitions result in N+ I states clock models (Z{sub N}) with long range interactions and we derive mean-field self-consistency equations for the clock model Hamiltonians. The microstructures from the mean-field solutions of the models are very similar to those obtained from the original continuum models or Monte Carlo simulations on the spin models (in the SR case), illustrating that these discrete models capture the salient physics. The models, in the presence of disorder, provide the basis for the study of the strain glass phase observed in martensitic alloys.
Near-field model of ultrasonic array data
Velichko, Alexander
2017-02-01
One method of efficiently modelling of ultrasonic array data is based on a combination of a ray-tracing approach and far-field scattering amplitude of a scatterer. This technique uses two main assumptions: all scatterers are located in the far-field from each array element and the size of each scatterer is small relative to its distance to array elements. The key part of the model is the so-called scattering matrix, which provides the amplitude and phase of scattered waves in the far-field of the scatterer. However, the far-field approximation fails when the size of the scatterer becomes comparable to its distance to array elements. In this paper a near-field model of ultrasonic array data is developed. In particular, it is shown that the near-field scattering behavior can be extracted from the scattering matrix. The applications of the model are discussed and supported with modelling examples.
Superhard BC(3) in cubic diamond structure.
Zhang, Miao; Liu, Hanyu; Li, Quan; Gao, Bo; Wang, Yanchao; Li, Hongdong; Chen, Changfeng; Ma, Yanming
2015-01-01
We solve the crystal structure of recently synthesized cubic BC(3) using an unbiased swarm structure search, which identifies a highly symmetric BC(3) phase in the cubic diamond structure (d-BC(3)) that contains a distinct B-B bonding network along the body diagonals of a large 64-atom unit cell. Simulated x-ray diffraction and Raman peaks of d-BC(3) are in excellent agreement with experimental data. Calculated stress-strain relations of d-BC(3) demonstrate its intrinsic superhard nature and reveal intriguing sequential bond-breaking modes that produce superior ductility and extended elasticity, which are unique among superhard solids. The present results establish the first boron carbide in the cubic diamond structure with remarkable properties, and these new findings also provide insights for exploring other covalent solids with complex bonding configurations.
Cubical Cohomology Ring of 3D Photographs
Gonzalez-Diaz, Rocio; Medrano, Belen; 10.1002/ima.20271
2011-01-01
Cohomology and cohomology ring of three-dimensional (3D) objects are topological invariants that characterize holes and their relations. Cohomology ring has been traditionally computed on simplicial complexes. Nevertheless, cubical complexes deal directly with the voxels in 3D images, no additional triangulation is necessary, facilitating efficient algorithms for the computation of topological invariants in the image context. In this paper, we present formulas to directly compute the cohomology ring of 3D cubical complexes without making use of any additional triangulation. Starting from a cubical complex $Q$ that represents a 3D binary-valued digital picture whose foreground has one connected component, we compute first the cohomological information on the boundary of the object, $\\partial Q$ by an incremental technique; then, using a face reduction algorithm, we compute it on the whole object; finally, applying the mentioned formulas, the cohomology ring is computed from such information.
Satellite data for geomagnetic field modeling
Langel, R. A.; Baldwin, R. T.
1992-06-01
Satellite measurements of the geomagnetic fields began with the launch of Sputnik 3 in May of 1958 and have continued sporadically. Spacecraft making significant contributions to main field geomagnetism will be reviewed and the characteristics of their data discussed, including coverage, accuracy, resolution and data availability. Of particular interest are Vanguard 3; Cosmos 49, Ogo's -2, -4, and -6; Magsat; DE-2; and POGS. Spacecraft make measurements on a moving platfrom above the ionosphere as opposed to measurements from fixed observatories and surveys, both below the ionosphere. Possible future missions, such as Aristoteles and GOS are reviewed.
Satellite Data for Geomagnetic Field Modeling
Langel, R. A.; Baldwin, R. T.
1992-01-01
Satellite measurements of the geomagnetic fields began with the launch of Sputnik 3 in May of 1958 and have continued sporadically. Spacecraft making significant contributions to main field geomagnetism will be reviewed and the characteristics of their data discussed, including coverage, accuracy, resolution and data availability. Of particular interest are Vanguard 3; Cosmos 49, Ogo's -2, -4, and -6; Magsat; DE-2; and POGS. Spacecraft make measurements on a moving platfrom above the ionosphere as opposed to measurements from fixed observatories and surveys, both below the ionosphere. Possible future missions, such as Aristoteles and GOS are reviewed.
Phase field modeling of dendrite growth
Institute of Scientific and Technical Information of China (English)
Yutuo ZHANG; Chengzhi WANG; Dianzhong LI; Yiyi LI
2009-01-01
Single dendrite and multi-dendrite growth for A1-2 mol pct Si alloy during isothermal solidification are simulated by phase field method. In the case of single equiaxed dendrite growth, the secondary and the necking phenomenon can be observed. For multi-dendrite growth, there exists the competitive growth among the dendrites dur-ing solidification. As solidification proceeds, growing and coarsening of the primary arms occurs, together with the branching and coarsening of the secondary arms.When the diffusion fields of dendrite tips come into contact with those of the branches growing from the neighboring dendrites, the dendrites stop growing and being to ripen and thicken.
Modeling the interaction of DNA with alternating fields
Bergues-Pupo, Ana Elisa; Falo, Fernando; 10.1103/PhysRevE.87.022703
2013-01-01
We study the influence of a THz field on thermal properties of DNA molecules. A Peyrard- Bishop-Dauxois model with the inclusion of a solvent interaction term is considered. The THz field is included as a sinusoidal driven force in the equation of mo tion. We show how under certain field and system parameters, melting transition and bubble formation are modified.
Updated Hungarian Gravity Field Solution Based on Fifth Generation GOCE Gravity Field Models
Toth, Gyula; Foldvary, Lorant
2015-03-01
With the completion of the ESA's GOCE satellite's mission fifth generation gravity field models are available from the ESA's GOCE High Processing Facility. Our contribution is an updated gravity field solution for Hungary using the latest DIR R05 GOCE gravity field model. The solution methodology is least squares gravity field parameter estimation using Spherical Radial Base Functions (SRBF). Regional datasets include deflections of the vertical (DOV), gravity anomalies and quasigeoid heights by GPS/levelling. The GOCE DIR R05 model has been combined with the EGM20008 model and has been evaluated in comparison with the EGM2008 and EIGEN-6C3stat models to assess the performance of our regional gravity field solution.
Institute of Scientific and Technical Information of China (English)
REN ZhiPeng; WAN WeiXing; WEI Yong; LIU LiBo; YU Tao
2008-01-01
The geomagnetic fields, which play important roles in the ionospheric dynamo, can greatly affect the global distribution of ionospheric electric fields, currents and other ionospheric electrodynamics phenomena. In the study of ionospheric electrodynamics phenomena, such as the longitudinal variations of ionospheric electric fields, the non-dipolar component of the geomagnetic fields must be taken into account. In this paper, we deduce a theoretical electric field model for ionospheric dynamo at midand low-latitude which adopt a modified magnetic apex coordinates system. In the new electric field model, the geomagnetic fields can be calculated from either the IGRF model or the dipole field model,and the neutral winds and conductivities are calculated based on empirical models. Then the dynamo equation for the electric potential is finally solved in terms of the line-by-line iteration method, and the ionospheric electric fields and currents are derived from the calculated potential. Our model can reproduce the main features of the ionospheric electrodynamics processes, so it will be a useful tool for the investigation of the upper atmosphere and ionosphere.
Propulsion Physics Under the Changing Density Field Model
Robertson, Glen A.
2011-01-01
To grow as a space faring race, future spaceflight systems will requires new propulsion physics. Specifically a propulsion physics model that does not require mass ejection without limiting the high thrust necessary to accelerate within or beyond our solar system and return within a normal work period or lifetime. In 2004 Khoury and Weltman produced a density dependent cosmology theory they called Chameleon Cosmology, as at its nature, it is hidden within known physics. This theory represents a scalar field within and about an object, even in the vacuum. Whereby, these scalar fields can be viewed as vacuum energy fields with definable densities that permeate all matter; having implications to dark matter/energy with universe acceleration properties; implying a new force mechanism for propulsion physics. Using Chameleon Cosmology, the author has developed a new propulsion physics model, called the Changing Density Field (CDF) Model. This model relates to density changes in these density fields, where the density field density changes are related to the acceleration of matter within an object. These density changes in turn change how an object couples to the surrounding density fields. Whereby, thrust is achieved by causing a differential in the coupling to these density fields about an object. Since the model indicates that the density of the density field in an object can be changed by internal mass acceleration, even without exhausting mass, the CDF model implies a new propellant-less propulsion physics model
Butera, P
2010-01-01
We have substantially extended the high-temperature and low-magnetic-field (and the related low-temperature and high-magnetic-field) bivariate expansions of the free energy for the conventional three-dimensional Ising model and for a variety of other spin systems generally assumed to belong to the same critical universality class. In particular, we have also derived the analogous expansions for the Ising models with spin s=1,3/2,.. and for the lattice euclidean scalar field theory with quartic self-interaction, on the simple cubic and the body-centered cubic lattices. Our bivariate high-temperature expansions, which extend through K^24, enable us to compute, through the same order, all higher derivatives of the free energy with respect to the field, namely all higher susceptibilities. These data make more accurate checks possible, in critical conditions, both of the scaling and the universality properties with respect to the lattice and the interaction structure and also help to improve an approximate paramet...
Temperature-dependent EXAFS study of the local structure and lattice dynamics in cubic Y₂O₃.
Jonane, Inga; Lazdins, Karlis; Timoshenko, Janis; Kuzmin, Alexei; Purans, Juris; Vladimirov, Pavel; Gräning, Tim; Hoffmann, Jan
2016-03-01
The local structure and lattice dynamics in cubic Y2O3 were studied at the Y K-edge by X-ray absorption spectroscopy in the temperature range from 300 to 1273 K. The temperature dependence of the extended X-ray absorption fine structure was successfully interpreted using classical molecular dynamics and a novel reverse Monte Carlo method, coupled with the evolutionary algorithm. The obtained results allowed the temperature dependence of the yttria atomic structure to be followed up to ∼6 Å and to validate two force-field models.
On the Potts Model Partition Function in an External Field
McDonald, Leslie M.; Moffatt, Iain
2012-03-01
We study the partition function of the Potts model in an external (magnetic) field, and its connections with the zero-field Potts model partition function. Using a deletion-contraction formulation for the partition function Z for this model, we show that it can be expanded in terms of the zero-field partition function. We also show that Z can be written as a sum over the spanning trees, and the spanning forests, of a graph G. Our results extend to Z the well-known spanning tree expansion for the zero-field partition function that arises though its connections with the Tutte polynomial.
Positive random fields for modeling material stiffness and compliance
DEFF Research Database (Denmark)
Hasofer, Abraham Michael; Ditlevsen, Ove Dalager; Tarp-Johansen, Niels Jacob
1998-01-01
with material properties modeled in terms of the considered random fields.The paper addsthe gamma field, the Fisher field, the beta field, and their reciprocal fields to the catalogue. These fields are all defined on the basis of sums of squares of independent standard Gaussian random variables.All the existing...... marginal moments and the correlation functions are obtained explicitly. Also an inverse Gaussian fieldis added to the catalogue. It is defined in terms of first passage times in correlated joint Brownian motions. Finally an n-dimensional random vector of positive components is defined such that it can...
Shape Modelling Using Markov Random Field Restoration of Point Correspondences
DEFF Research Database (Denmark)
Paulsen, Rasmus Reinhold; Hilger, Klaus Baggesen
2003-01-01
A method for building statistical point distribution models is proposed. The novelty in this paper is the adaption of Markov random field regularization of the correspondence field over the set of shapes. The new approach leads to a generative model that produces highly homogeneous polygonized sh...
Temperature fields in machining processes and heat transfer models
Energy Technology Data Exchange (ETDEWEB)
Palazzo, G.; Pasquino, R. [University of Salerno Via Ponte Donmelillo, Fisciano (Italy). Department of Mechanical Engineering; Bellomo, N. [Politecnico Torino Corso Duca degli Abruzzi, Torino (Italy). Department of Mathematics
2002-07-01
This paper deals with the modelling of the heat transfer process with special attention to the characterization of the thermal field during turning processes. Specifically, the measurement of the thermal field and the selection of the proper heat transfer models are dealt with. The analysis is developed in view of the solution of direct and inverse problems. (author)
Inhomogeneous atomic Bose-Fermi mixtures in cubic lattices.
Cramer, M; Eisert, J; Illuminati, F
2004-11-05
We determine the ground state properties of inhomogeneous mixtures of bosons and fermions in cubic lattices and parabolic confining potentials. For finite hopping we determine the domain boundaries between Mott-insulator plateaux and hopping-dominated regions for lattices of arbitrary dimension within mean-field and perturbation theory. The results are compared with a new numerical method that is based on a Gutzwiller variational approach for the bosons and an exact treatment for the fermions. The findings can be applied as a guideline for future experiments with trapped atomic Bose-Fermi mixtures in optical lattices.
Energy Technology Data Exchange (ETDEWEB)
Hu, Shenyang [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Burkes, Douglas E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lavender, Curt A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Senor, David J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Setyawan, Wahyu [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Xu, Zhijie [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2016-07-08
Nano-gas bubble superlattices are often observed in irradiated UMo nuclear fuels. However, the for- mation mechanism of gas bubble superlattices is not well understood. A number of physical processes may affect the gas bubble nucleation and growth; hence, the morphology of gas bubble microstructures including size and spatial distributions. In this work, a phase-field model integrating a first-passage Monte Carlo method to investigate the formation mechanism of gas bubble superlattices was devel- oped. Six physical processes are taken into account in the model: 1) heterogeneous generation of gas atoms, vacancies, and interstitials informed from atomistic simulations; 2) one-dimensional (1-D) migration of interstitials; 3) irradiation-induced dissolution of gas atoms; 4) recombination between vacancies and interstitials; 5) elastic interaction; and 6) heterogeneous nucleation of gas bubbles. We found that the elastic interaction doesn’t cause the gas bubble alignment, and fast 1-D migration of interstitials along $\\langle$110$\\rangle$ directions in the body-centered cubic U matrix causes the gas bubble alignment along $\\langle$110$\\rangle$ directions. It implies that 1-D interstitial migration along [110] direction should be the primary mechanism of a fcc gas bubble superlattice which is observed in bcc UMo alloys. Simulations also show that fission rates, saturated gas concentration, and elastic interaction all affect the morphology of gas bubble microstructures.
Hu, Shenyang; Burkes, Douglas E.; Lavender, Curt A.; Senor, David J.; Setyawan, Wahyu; Xu, Zhijie
2016-10-01
Nano-gas bubble superlattices are often observed in irradiated UMo nuclear fuels. However, the formation mechanism of gas bubble superlattices is not well understood. A number of physical processes may affect the gas bubble nucleation and growth; hence, the morphology of gas bubble microstructures including size and spatial distributions. In this work, a phase-field model integrating a first-passage Monte Carlo method to investigate the formation mechanism of gas bubble superlattices was developed. Six physical processes are taken into account in the model: 1) heterogeneous generation of gas atoms, vacancies, and interstitials informed from atomistic simulations; 2) one-dimensional (1-D) migration of interstitials; 3) irradiation-induced dissolution of gas atoms; 4) recombination between vacancies and interstitials; 5) elastic interaction; and 6) heterogeneous nucleation of gas bubbles. We found that the elastic interaction doesn't cause the gas bubble alignment, and fast 1-D migration of interstitials along directions in the body-centered cubic U matrix causes the gas bubble alignment along directions. It implies that 1-D interstitial migration along [110] direction should be the primary mechanism of a fcc gas bubble superlattice which is observed in bcc UMo alloys. Simulations also show that fission rates, saturated gas concentration, and elastic interaction all affect the morphology of gas bubble microstructures.
Field theory model of brain extracellular matrix
Molochkov, Alexander; Goy, Vladimir; Tolstonogov, Anton
2014-01-01
The perineural net (PNN) is responsible for synaptic stabilization of adult brain. It plays an important role in brain signal processing and non-synaptic signal transfer as well [ 1]. Since it is composed of largely negatively charged chains of disaccharides, it can be easily affected by strong external electromagnetic field irradiated by high-energy particles passing brain tissues. One of the effects of such exposure is a cognitive impairment. Since outside of the Bragg peak area local elect...
On Application of Non-cubic EoS to Compositional Reservoir Simulation
DEFF Research Database (Denmark)
Yan, Wei; Michelsen, Michael Locht; Stenby, Erling Halfdan
Compositional reservoir simulation uses almost exclusively cubic equations of state (EoS) such as the SRK EoS and the PR EoS. This is in contrast with process simulation in the downstream industry where more recent and advanced thermodynamic models are quickly adopted. Many of these models are non......-cubic EoS, such as the PC-SAFT EoS. A major reason for the use of the conventional cubic EoS in reservoir simulation is the concern over computation time. Flash computation is the most time consuming part in compositional reservoir simulation, and the extra complexity of the non-cubic EoS may significantly...... such models. In this work we test the feasibility of applying a non-cubic EoS to reservoir simulation, using a slimtube simulator to simulate multicomponent gas injection using both the traditional SRK EoS and the non-cubic PC-SAFT EoS. Computation times for both models were compared. In addition, C7...
Post-processing scheme for modelling the lithospheric magnetic field
Directory of Open Access Journals (Sweden)
V. Lesur
2013-03-01
Full Text Available We investigated how the noise in satellite magnetic data affects magnetic lithospheric field models derived from these data in the special case where this noise is correlated along satellite orbit tracks. For this we describe the satellite data noise as a perturbation magnetic field scaled independently for each orbit, where the scaling factor is a random variable, normally distributed with zero mean. Under this assumption, we have been able to derive a model for errors in lithospheric models generated by the correlated satellite data noise. Unless the perturbation field is known, estimating the noise in the lithospheric field model is a non-linear inverse problem. We therefore proposed an iterative post-processing technique to estimate both the lithospheric field model and its associated noise model. The technique has been successfully applied to derive a lithospheric field model from CHAMP satellite data up to spherical harmonic degree 120. The model is in agreement with other existing models. The technique can, in principle, be extended to all sorts of potential field data with "along-track" correlated errors.
Initial conditions in the neural field model
Valdes-Hernandez, Pedro A
2016-01-01
In spite of the large amount of existing neural models in the literature, there is a lack of a systematic review of the possible effect of choosing different initial conditions on the dynamic evolution of neural systems. In this short review we intend to give insights into this topic by discussing some published examples. First, we briefly introduce the different ingredients of a neural dynamical model. Secondly, we introduce some concepts used to describe the dynamic behavior of neural models, namely phase space and its portraits, time series, spectra, multistability and bifurcations. We end with an analysis of the irreversibility of processes and its implications on the functioning of normal and pathological brains.
Methods in Model Order Reduction (MOR) field
Institute of Scientific and Technical Information of China (English)
刘志超
2014-01-01
Nowadays, the modeling of systems may be quite large, even up to tens of thousands orders. In spite of the increasing computational powers, direct simulation of these large-scale systems may be impractical. Thus, to industry requirements, analytically tractable and computationally cheap models must be designed. This is the essence task of Model Order Reduction (MOR). This article describes the basics of MOR optimization, various way of designing MOR, and gives the conclusion about existing methods. In addition, it proposed some heuristic footpath.
Draping of the Interstellar Magnetic Field over the Heliopause - A Passive Field Model
Isenberg, Philip A; Mobius, Eberhard
2015-01-01
As the local interstellar plasma flows past our heliosphere, it is slowed and deflected around the magnetic obstacle of the heliopause. The interstellar magnetic field, frozen into this plasma, then becomes draped around the heliopause in a characteristic manner. We derive the analytical solution for this draped magnetic field in the limit of weak field intensity, assuming an ideal potential flow around the heliopause, which we model as a Rankine half-body. We compare the structure of the model magnetic field with observed properties of the IBEX ribbon and with in situ observations at the Voyager 1 spacecraft. We find reasonable qualitative agreement, given the idealizations of the model. This agreement lends support to the secondary ENA model of the IBEX ribbon and to the interpretation that Voyager 1 has crossed the heliopause. We also predict that the magnetic field measured by Voyager 2 after it crosses the heliopause will not be significantly rotated away from the direction of the undisturbed interstella...
GA Based Rational cubic B-Spline Representation for Still Image Interpolation
Samreen Abbas; Malik Zawwar Hussain; Misbah Irshad
2016-01-01
In this paper, an image interpolation scheme is designed for 2D natural images. A local support rational cubic spline with control parameters, as interpolatory function, is being optimized using Genetic Algorithm (GA). GA is applied to determine the appropriate values of control parameter used in the description of rational cubic spline. Three state-of-the-art Image Quality Assessment (IQA) models with traditional one are hired for comparison with existing image interpolation schemes and perc...
Exact Solutions of Discrete Complex Cubic Ginzburg-Landau Equation and Their Linear Stability
Institute of Scientific and Technical Information of China (English)
张金良; 刘治国
2011-01-01
The discrete complex cubic Ginzburg-Landau equation is an important model to describe a number of physical systems such as Taylor and frustrated vortices in hydrodynamics and semiconductor laser arrays in optics. In this paper, the exact solutions of the discrete complex cubic Ginzburg-Landau equation are derived using homogeneous balance principle and the GI/G-expansion method, and the linear stability of exact solutions is discussed.
Relations among Dirichlet series whose coefficients are class numbers of binary cubic forms II
Ohno, Yasuo
2011-01-01
As a continuation of the authors and Wakatsuki's previous paper [5], we study relations among Dirichlet series whose coefficients are class numbers of binary cubic forms. We show that for any integral models of the space of binary cubic forms, the associated Dirichlet series satisfies a simple explicit relation to that of the dual other than the usual functional equation. As an application, we write the functional equations of these Dirichlet series in self dual forms.
DEFICIENT CUBIC SPLINES WITH AVERAGE SLOPE MATCHING
Institute of Scientific and Technical Information of China (English)
V. B. Das; A. Kumar
2005-01-01
We obtain a deficient cubic spline function which matches the functions with certain area matching over a greater mesh intervals, and also provides a greater flexibility in replacing area matching as interpolation. We also study their convergence properties to the interpolating functions.
Counting rational points on cubic curves
Institute of Scientific and Technical Information of China (English)
HEATH-BROWN; Roger; TESTA; Damiano
2010-01-01
We prove upper bounds for the number of rational points on non-singular cubic curves defined over the rationals.The bounds are uniform in the curve and involve the rank of the corresponding Jacobian.The method used in the proof is a combination of the "determinant method" with an m-descent on the curve.
CONSTRAINED RATIONAL CUBIC SPLINE AND ITS APPLICATION
Institute of Scientific and Technical Information of China (English)
Qi Duan; Huan-ling Zhang; Xiang Lai; Nan Xie; Fu-hua (Frank) Cheng
2001-01-01
In this paper, a kind of rational cubic interpolation functionwith linear denominator is constructed. The constrained interpolation with constraint on shape of the interpolating curves and on the second-order derivative of the interpolating function is studied by using this interpolation, and as the consequent result, the convex interpolation conditions have been derived.
Anisotropy of a cubic ferromagnet at criticality
Kudlis, A.; Sokolov, A. I.
2016-10-01
Critical fluctuations change the effective anisotropy of cubic ferromagnet near the Curie point. If the crystal undergoes phase transition into orthorhombic phase and the initial anisotropy is not too strong, reduced anisotropy of nonlinear susceptibility acquires at Tc the universal value δ4*=2/v* 3 (u*+v*) where u* and v* are coordinates of the cubic fixed point on the flow diagram of renormalization group equations. In the paper, the critical value of the reduced anisotropy is estimated within the pseudo-ɛ expansion approach. The six-loop pseudo-ɛ expansions for u*, v*, and δ4* are derived for the arbitrary spin dimensionality n . For cubic crystals (n =3 ) higher-order coefficients of the pseudo-ɛ expansions obtained turn out to be so small that use of simple Padé approximants yields reliable numerical results. Padé resummation of the pseudo-ɛ series for u*, v*, and δ4* leads to the estimate δ4*=0.079 ±0.006 , indicating that detection of the anisotropic critical behavior of cubic ferromagnets in physical and computer experiments is certainly possible.
The cactus rank of cubic forms
Bernardi, Alessandra
2011-01-01
We prove that the smallest degree of an apolar 0-dimensional scheme to a general cubic form in $n+1$ variables is at most $2n+2$, when $n\\geq 8$, and therefore smaller than the rank of the form. When n=8 we show that the bound is sharp, i.e. the smallest degree of an apolar subscheme is 18.
Uncertainty analysis for a field-scale P loss model
Models are often used to predict phosphorus (P) loss from agricultural fields. While it is commonly recognized that model predictions are inherently uncertain, few studies have addressed prediction uncertainties using P loss models. In this study we assessed the effect of model input error on predic...
A note on moving average models for Gaussian random fields
DEFF Research Database (Denmark)
Hansen, Linda Vadgård; Thorarinsdottir, Thordis L.
The class of moving average models offers a flexible modeling framework for Gaussian random fields with many well known models such as the Matérn covariance family and the Gaussian covariance falling under this framework. Moving average models may also be viewed as a kernel smoothing of a Lévy...
Mean-field approximation for the potts model of a diluted magnet in the external field
Semkin, S. V.; Smagin, V. P.
2016-07-01
The Potts model of a diluted magnet with an arbitrary number of states placed in the external field has been considered. Phase transitions of this model have been studied in the mean-field approximation, the dependence of the critical temperature on the external field and the density of magnetic atoms has been found, and the magnetic susceptibility has been calculated. An improved mean-field technique has been proposed, which provides more accurate account of the effects associated with nonmagnetic dilution. The influence of dilution on the first-order phase transition curve and the magnetization jump at the phase transition has been studied by this technique.
Use of along-track magnetic field differences in lithospheric field modelling
DEFF Research Database (Denmark)
Kotsiaros, Stavros; Finlay, Chris; Olsen, Nils
2015-01-01
, using 2 yr of low altitude data from the CHAMP satellite, we show that use of along-track differences of vector field data results in an enhanced recovery of the small scale lithospheric field, compared to the use of the vector field data themselves. We show that the along-track technique performs....... Experiments in modelling the Earth's lithospheric magnetic field with along-track differences are presented here as a proof of concept. We anticipate that use of such along-track differences in combination with east–west field differences, as are now provided by the Swarm satellite constellation...
Numerical modeling of 3-D terrain effect on MT field
Institute of Scientific and Technical Information of China (English)
徐世浙; 阮百尧; 周辉; 陈乐寿; 徐师文
1997-01-01
Using the boundary element method, the numerical modeling problem of three-dimensional terrain effect on magnetotelluric (MT) field is solved. This modeling technique can be run on PC in the case of adopting special net division. The result of modeling test for 2-D terrain by this modeling technique is basically coincident with that by 2-D modeling technique, but there is a great difference between the results of 3-D and 2-D modeling for 3-D terrain.
Cubic Plus Association Equation of State for Flow Assurance Projects
DEFF Research Database (Denmark)
dos Santos, Leticia Cotia; Abunahman, Samir Silva; Tavares, Frederico Wanderley
2015-01-01
Thermodynamic hydrate inhibitors such as methanol, ethanol, (mono) ethylene glycol (MEG), and triethylene glycol (TEG) are widely used in the oil and gas industry. On modeling these compounds, we show here how the CPA equation of state was implemented in an in-house process simulator as an in......-built model: To validate the implementation, we show calulations for binary systems containing hydrate inhibitors and water or hydrocarbons using the Cubic Plus Association (CPA) and Soave-Redlich-Kwong (SRK) equation of states, also comparing against experimental data. For streams containing natural gas...
The 1995 revision of the joint US/UK geomagnetic field models. II: Main field
Quinn, J.M.; Coleman, R.J.; Macmillan, S.; Barraclough, D.R.
1997-01-01
This paper presents the 1995 main-field revision of the World Magnetic Model (WMM-95). It is based on Project MAGNET high-level (??? 15,000 ft.) vector aeromagnetic survey data collected between 1988 and 1994 and on scalar total intensity data collected by the Polar Orbiting Geomagnetic Survey (POGS) satellite during the period 1991 through 1993. The spherical harmonic model produced from these data describes that portion of the Earth's magnetic field generated internal to the Earth's surface at the 1995.0 Epoch. When combined with the spherical harmonic model of the Earth's secular variation described in paper I, the Earth's main magnetic field is fully characterized between the years 1995 and 2000. Regional magnetic field models for the conterminous United States, Alaska and, Hawaii were generated as by-products of the global modeling process.
Mean field models for spin glasses
Talagrand, Michel
2011-01-01
This is a new, completely revised, updated and enlarged edition of the author's Ergebnisse vol. 46: "Spin Glasses: A Challenge for Mathematicians". This new edition will appear in two volumes, the present first volume presents the basic results and methods, the second volume is expected to appear in 2011. In the eighties, a group of theoretical physicists introduced several models for certain disordered systems, called "spin glasses". These models are simple and rather canonical random structures, of considerable interest for several branches of science (statistical physics, neural networks and computer science). The physicists studied them by non-rigorous methods and predicted spectacular behaviors. This book introduces in a rigorous manner this exciting new area to the mathematically minded reader. It requires no knowledge whatsoever of any physics. The first volume of this new and completely rewritten edition presents six fundamental models and the basic techniques to study them.
Regularity of solutions of a phase field model
Amler, Thomas
2013-01-01
Phase field models are widely-used for modelling phase transition processes such as solidification, freezing or CO2 sequestration. In this paper, a phase field model proposed by G. Caginalp is considered. The existence and uniqueness of solutions are proved in the case of nonsmooth initial data. Continuity of solutions with respect to time is established. In particular, it is shown that the governing initial boundary value problem can be considered as a dynamical system. © 2013 International Press.
Field Guide to Plant Model Systems.
Chang, Caren; Bowman, John L; Meyerowitz, Elliot M
2016-10-06
For the past several decades, advances in plant development, physiology, cell biology, and genetics have relied heavily on the model (or reference) plant Arabidopsis thaliana. Arabidopsis resembles other plants, including crop plants, in many but by no means all respects. Study of Arabidopsis alone provides little information on the evolutionary history of plants, evolutionary differences between species, plants that survive in different environments, or plants that access nutrients and photosynthesize differently. Empowered by the availability of large-scale sequencing and new technologies for investigating gene function, many new plant models are being proposed and studied. Copyright © 2016 Elsevier Inc. All rights reserved.
Phase field modelling of interfaces from first principles
Energy Technology Data Exchange (ETDEWEB)
Pruessner, G [Mathematics Institute, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL (United Kingdom); Sutton, A P [Department of Physics, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom)], E-mail: g.pruessner@imperial.ac.uk, E-mail: a.sutton@imperial.ac.uk
2008-01-15
Phase field modelling is a technique in (computational) material science that utilises diffuse interface constructions to simulate the dynamics of microstructural evolution. To date, phase field modelling of crystalline interfaces has been guided mainly by phenomenology and symmetry considerations, rather than microscopic physics. The central equation of motion minimises a free energy with respect to the phase field, which is considered as a space and time dependent, coarse-grained, continuous degree of freedom of the system. However, it is neither clear how to interpret the phase field microscopically, nor how to derive the equation of motion from atomic interactions. Based on the (classical) density functional theory by Haymet and Oxtoby, we derive the phase field model by Allen and Cahn, which is commonly used for modelling crystalline interfaces. In the present article, we summarise the physical implications of the various observables and parameters as well as the underlying approximations.
Vector field models of inflation and dark energy
Energy Technology Data Exchange (ETDEWEB)
Koivisto, Tomi; Mota, David F, E-mail: T.Koivisto@thphys.uni-heidelberg.de, E-mail: D.Mota@thphys.uni-heidelberg.de [Institute for Theoretical Physics, University of Heidelberg, 69120 Heidelberg (Germany)
2008-08-15
We consider several new classes of viable vector field alternatives to the inflaton and quintessence scalar fields. Spatial vector fields are shown to be compatible with the cosmological anisotropy bounds if only slightly displaced from the potential minimum while dominant, or if driving an anisotropic expansion with nearly vanishing quadrupole today. The Bianchi I model with a spatial field and an isotropic fluid is studied as a dynamical system, and scaling solutions of several types are found. On the other hand, time-like fields are automatically compatible with large-scale isotropy. We show that they can be dynamically important if non-minimal gravity couplings are taken into account. We reconstruct as an example a vector-Gauss-Bonnet model which generates the concordance model acceleration at late times and supports an inflationary epoch at high curvatures. The evolution of the vortical perturbations in such models is computed.
Modified Mean Field approximation for the Ising Model
Di Bartolo, Cayetano
2009-01-01
We study a modified mean-field approximation for the Ising Model in arbitrary dimension. Instead of taking a "central" spin, or a small "drop" of fluctuating spins coupled to the effective field of their nearest neighbors as in the Mean-Field or the Bethe-Peierls-Weiss methods, we take an infinite chain of fluctuating spins coupled to the mean field of the rest of the lattice. This results in a significative improvement of the Mean-Field approximation with a small extra effort.
Effects of quadratic and cubic nonlinearities on a perfectly tuned parametric amplifier
Neumeyer, S.; Sorokin, V. S.; Thomsen, J. J.
2017-01-01
We consider the performance of a parametric amplifier with perfect tuning (two-to-one ratio between the parametric and direct excitation frequencies) and quadratic and cubic nonlinearities. A forced Duffing-Mathieu equation with appended quadratic nonlinearity is considered as the model system, and approximate analytical steady-state solutions and corresponding stabilities are obtained by the method of varying amplitudes. Some general effects of pure quadratic, and mixed quadratic and cubic nonlinearities on parametric amplification are shown. In particular, the effects of mixed quadratic and cubic nonlinearities may generate additional amplitude-frequency solutions. In this case an increased response and a more phase sensitive amplitude (phase between excitation frequencies) is obtained, as compared to the case with either pure quadratic or cubic nonlinearity. Furthermore, jumps and bi-stability in the amplitude-phase characteristics are predicted, supporting previously reported experimental observations.
Russier, V.
2016-07-01
The low temperature behavior of densely packed interacting spherical single domain nanoparticles (MNP) is investigated by Monte Carlo simulations in the framework of an effective one spin model. The particles are distributed through a hard sphere like distribution with periodic boundary conditions and interact through the dipole dipole interaction (DDI) with an anisotropy energy including both cubic and uniaxial symmetry components. The cubic component is shown to play a sizable role on the value of the blocking temperature Tb only when the MNP easy axes are parallel to the cubic easy direction ([111] direction for a negative cubic anisotropy constant). The nature of the collective low temperature state, either ferromagnetic or spin glass like, is found to depend on the ratio of the anisotropy to the dipolar energies characterizing partly the disorder in the system.
Is inner core seismic anisotropy a marker of plastic flow of cubic iron?
Lincot, A; Cardin, Philippe
2015-01-01
This paper investigates whether observations of seismic anisotropy are compatible with a cubic structure of the inner core Fe alloy. We assume that anisotropy is the result of plastic deformation within a large scale flow induced by preferred growth at the inner core equator. Based on elastic moduli from the literature, bcc- or fcc-Fe produce seismic anisotropy well below seismic observations ($\\textless{}0.4\\%$). A Monte-Carlo approach allows us to generalize this result to any form of elastic anisotropy in a cubic system. Within our model, inner core global anisotropy is not compatible with a cubic structure of Fe alloy. Hence, if the inner core material is indeed cubic, large scale coherent anisotropic structures, incompatible with plastic deformation induced by large scale flow, must be present.
Rotation-limited growth of three-dimensional body-centered-cubic crystals.
Tarp, Jens M; Mathiesen, Joachim
2015-07-01
According to classical grain growth laws, grain growth is driven by the minimization of surface energy and will continue until a single grain prevails. These laws do not take into account the lattice anisotropy and the details of the microscopic rearrangement of mass between grains. Here we consider coarsening of body-centered-cubic polycrystalline materials in three dimensions using the phase field crystal model. We observe, as a function of the quenching depth, a crossover between a state where grain rotation halts and the growth stagnates and a state where grains coarsen rapidly by coalescence through rotation and alignment of the lattices of neighboring grains. We show that the grain rotation per volume change of a grain follows a power law with an exponent of -1.25. The scaling exponent is consistent with theoretical considerations based on the conservation of dislocations.
Ytterbium: Transition at High Pressure from Face-Centered Cubic to Body-Centered Cubic Structure.
Hall, H T; Barnett, J D; Merrill, L
1963-01-11
Pressure of 40,000 atmospheres at 25 degrees C induces a phase transformation in ytterbium metal; the face-centered cubic structure changes to body-centered cubic. The radius of the atom changes from 1.82 to 1.75 A. At the same time the atom's volume decreases by 11 percent and the volume, observed macroscopically, decreases 3.2 percent.
The Frontier Fields Lens Modeling Comparison Project
Meneghetti, M; Coe, D; Contini, E; De Lucia, G; Giocoli, C; Acebron, A; Borgani, S; Bradac, M; Diego, J M; Hoag, A; Ishigaki, M; Johnson, T L; Jullo, E; Kawamata, R; Lam, D; Limousin, M; Liesenborgs, J; Oguri, M; Sebesta, K; Sharon, K; Williams, L L R; Zitrin, A
2016-01-01
Gravitational lensing by clusters of galaxies offers a powerful probe of their structure and mass distribution. Deriving a lens magnification map for a galaxy cluster is a classic inversion problem and many methods have been developed over the past two decades to solve it. Several research groups have developed techniques independently to map the predominantly dark matter distribution in cluster lenses. While these methods have all provided remarkably high precision mass maps, particularly with exquisite imaging data from the Hubble Space Telescope (HST), the reconstructions themselves have never been directly compared. In this paper, we report the results of comparing various independent lens modeling techniques employed by individual research groups in the community. Here we present for the first time a detailed and robust comparison of methodologies for fidelity, accuracy and precision. For this collaborative exercise, the lens modeling community was provided simulated cluster images -- of two clusters Are...
TMS field modelling-status and next steps
DEFF Research Database (Denmark)
Thielscher, Axel
2013-01-01
In the recent years, an increasing number of studies used geometrically accurate head models and finite element (FEM) or finite difference methods (FDM) to estimate the electric field induced by non-invasive neurostimulation techniques such as transcranial magnetic stimulation (TMS) or transcranial......, field estimates based on accurate head models have already proven highly useful for a better understanding of the biophysics of non-invasive brain stimulation. The improved software tools now allow for systematic tests of the links between the estimated fields and the physiological effects in multi...... weak current stimulation (tCS; e.g., Datta et al., 2010; Thielscher et al., 2011). A general outcome was that the field estimates based on these more realistic models differ substantially from the results obtained with simpler head models. This suggests that the former models are indeed needed...
Anisotropy in wavelet-based phase field models
Korzec, Maciek
2016-04-01
When describing the anisotropic evolution of microstructures in solids using phase-field models, the anisotropy of the crystalline phases is usually introduced into the interfacial energy by directional dependencies of the gradient energy coefficients. We consider an alternative approach based on a wavelet analogue of the Laplace operator that is intrinsically anisotropic and linear. The paper focuses on the classical coupled temperature/Ginzburg--Landau type phase-field model for dendritic growth. For the model based on the wavelet analogue, existence, uniqueness and continuous dependence on initial data are proved for weak solutions. Numerical studies of the wavelet based phase-field model show dendritic growth similar to the results obtained for classical phase-field models.
A quantum model of a real scalar field
Institute of Scientific and Technical Information of China (English)
吴宁; 阮图南
1997-01-01
A quantum model of a real scalar field with local operator gauge symmetry is discussed. In the localized theory, in order to keep the local operator gauge symmetry, an operator gauge potential Bμ is needed. By combining the constraint of operator gauge potential Bμ and the microscopic causality theorem, the usual canonical quantization condition of a real scalar field is obtained. Therefore, a quantum model of a real scalar field without the usual procedure of quantizing a related classical model can be directly constructed.
Phase field modeling of tetragonal to monoclinic phase transformation in zirconia
Mamivand, Mahmood
Zirconia based ceramics are strong, hard, inert, and smooth, with low thermal conductivity and good biocompatibility. Such properties made zirconia ceramics an ideal material for different applications form thermal barrier coatings (TBCs) to biomedicine applications like femoral implants and dental bridges. However, this unusual versatility of excellent properties would be mediated by the metastable tetragonal (or cubic) transformation to the stable monoclinic phase after a certain exposure at service temperatures. This transformation from tetragonal to monoclinic, known as LTD (low temperature degradation) in biomedical application, proceeds by propagation of martensite, which corresponds to transformation twinning. As such, tetragonal to monoclinic transformation is highly sensitive to mechanical and chemomechanical stresses. It is known in fact that this transformation is the source of the fracture toughening in stabilized zirconia as it occurs at the stress concentration regions ahead of the crack tip. This dissertation is an attempt to provide a kinetic-based model for tetragonal to monoclinic transformation in zirconia. We used the phase field technique to capture the temporal and spatial evolution of monoclinic phase. In addition to morphological patterns, we were able to calculate the developed internal stresses during tetragonal to monoclinic transformation. The model was started form the two dimensional single crystal then was expanded to the two dimensional polycrystalline and finally to the three dimensional single crystal. The model is able to predict the most physical properties associated with tetragonal to monoclinic transformation in zirconia including: morphological patterns, transformation toughening, shape memory effect, pseudoelasticity, surface uplift, and variants impingement. The model was benched marked with several experimental works. The good agreements between simulation results and experimental data, make the model a reliable tool for
Numerical Modelling of Electromagnetic Field in a Tornado
Directory of Open Access Journals (Sweden)
Pavel Fiala
2008-01-01
Full Text Available This study deals with the numerical model of both the physical and the chemical processes in the tornado. Within the paper, a basic theoretical model and a numerical solution are presented. We prepared numerical models based on the combined finite element method (FEM and the finite volume method (FVM. The model joins the magnetic, electric and current fields, the flow field and a chemical nonlinear ion model. The results were obtained by means of the FEM/FVM as a main application in ANSYS software.
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.
Observational constraints on inflation models with nonminimal scalar field
Noh, H
2001-01-01
We present the power spectra of the scalar- and tensor-type structures generated in an inflation model based on the nonminimally coupled scalar field with a self coupling. By comparing the contributions of these structures to the anisotropy of the cosmic microwave background radiation with the four year COBE DMR data we derive strong constraints on model parameters and the inflation model.
Negativity in the Extended Hubbard Model under External Magnetic Field
Institute of Scientific and Technical Information of China (English)
YANG Zhen; NING Wen-Qiang
2008-01-01
We exactly calculate the negativity,a measurement of entanglement,in the two-site extended Hubbard model with external magnetic field.Its behaviour at different temperatures is presented.The negativity reduces with the increasing temperature or with the increasing uniform external magnetic field.It is also found that a non-uniform external magnetic field can be used to modulate or to increase the negativity.
Nonequilibrium Dynamical Mean-Field Theory for Bosonic Lattice Models
2015-01-01
We develop the nonequilibrium extension of bosonic dynamical mean-field theory and a Nambu real-time strong-coupling perturbative impurity solver. In contrast to Gutzwiller mean-field theory and strong-coupling perturbative approaches, nonequilibrium bosonic dynamical mean-field theory captures not only dynamical transitions but also damping and thermalization effects at finite temperature. We apply the formalism to quenches in the Bose-Hubbard model, starting from both the normal and the Bos...
A class of effective field theory models of cosmic acceleration
Energy Technology Data Exchange (ETDEWEB)
Bloomfield, Jolyon K.; Flanagan, Éanna É., E-mail: jkb84@cornell.edu, E-mail: eef3@cornell.edu [Center for Radiophysics and Space Research, Cornell University, Space Science Building, Ithaca, NY 14853 (United States)
2012-10-01
We explore a class of effective field theory models of cosmic acceleration involving a metric and a single scalar field. These models can be obtained by starting with a set of ultralight pseudo-Nambu-Goldstone bosons whose couplings to matter satisfy the weak equivalence principle, assuming that one boson is lighter than all the others, and integrating out the heavier fields. The result is a quintessence model with matter coupling, together with a series of correction terms in the action in a covariant derivative expansion, with specific scalings for the coefficients. After eliminating higher derivative terms and exploiting the field redefinition freedom, we show that the resulting theory contains nine independent free functions of the scalar field when truncated at four derivatives. This is in contrast to the four free functions found in similar theories of single-field inflation, where matter is not present. We discuss several different representations of the theory that can be obtained using the field redefinition freedom. For perturbations to the quintessence field today on subhorizon lengthscales larger than the Compton wavelength of the heavy fields, the theory is weakly coupled and natural in the sense of t'Hooft. The theory admits a regime where the perturbations become modestly nonlinear, but very strong nonlinearities lie outside its domain of validity.
Up and down cascades: three-dimensional magnetic field model.
Blanter, E M; Shnirman, M G; Le Mouël, J L
2002-06-01
In our previous works we already have proposed a two-dimensional model of geodynamo. Now we use the same approach to build a three-dimensional self-excited geodynamo model that generates a large scale magnetic field from whatever small initial field, using the up and down cascade effects of a multiscale turbulent system of cyclones. The multiscale system of turbulent cyclones evolves in six domains of an equatorial cylindrical layer of the core. The appearance of new cyclones is realized by two cascades: a turbulent direct cascade and an inverse cascade of coupling of similar cyclones. The interaction between the different domains is effected through a direct cascade parameter which is essential for the statistics of the long-life symmetry breaking. Generation of the secondary magnetic field results from the interaction of the components of the primary magnetic field with the turbulent cyclones. The amplification of the magnetic field is due to the transfer of energy from the turbulent helical motion to the generated magnetic field. The model demonstrates a phase transition through the parameter characterizing this energy transfer. In the supercritical domain we obtain long-term intervals of constant polarity (chrons) and quick reversals; relevant time constants agree with paleomagnetic observations. Possible application of the model to the study of the geometrical structure of the geomagnetic field (and briefly other planetary fields) is discussed.
Geologic model of the Cerro Prieto geothermal field
Halfman, S. E.; Howard, J. H.; Vonderhaar, S. P.
1982-09-01
One of the tasks under the Mexican-American cooperative agreement is the comprehensive geologic study of the Cerro Prieto geothermal field. Using logs from over seventy deep wells as the basic source of information on the subsurface geology, a working model of the Cerro Prieto geothermal field is developed.
Face-Centered-Cubic Nanostructured Polymer Foams
Cui, C.; Baughman, R. H.; Liu, L. M.; Zakhidov, A. A.; Khayrullin, I. I.
1998-03-01
Beautifully iridescent polymer foams having Fm-3m cubic symmetry and periodicities on the scale of the wavelength of light have been synthesized by the templating of porous synthetic opals. These fabrication processes involve the filling of porous SiO2 opals (with typical cubic lattice parameters of 250 nm) with either polymers or polymer precursors, polymerization of the precursors if necessary, and removal of the fcc array of SiO2 balls to provide an all-polymer structure. The structures of these foams are similar to periodic minimal surfaces, although the Gaussian curvature can have both positive and negative values. Depending upon whether the internal surfaces of the opal are polymer filled or polymer coated, the polymer replica has either one or two sets of independent channels. We fill these channels with semiconductors, metals, or superconductors to provide electronic and optical materials with novel properties dependent on the nanoscale periodicity.
Large field excursions from a few site relaxion model
Fonseca, N.; de Lima, L.; Machado, C. S.; Matheus, R. D.
2016-07-01
Relaxion models are an interesting new avenue to explain the radiative stability of the Standard Model scalar sector. They require very large field excursions, which are difficult to generate in a consistent UV completion and to reconcile with the compact field space of the relaxion. We propose an N -site model which naturally generates the large decay constant needed to address these issues. Our model offers distinct advantages with respect to previous proposals: the construction involves non-Abelian fields, allowing for controlled high-energy behavior and more model building possibilities, both in particle physics and inflationary models, and also admits a continuum limit when the number of sites is large, which may be interpreted as a warped extra dimension.
Geomagnetic core field models in the satellite era
DEFF Research Database (Denmark)
Lesur, Vincent; Olsen, Nils; Thomson, Alan W. P.
2011-01-01
After a brief review of the theoretical basis and difficulties that modelers are facing, we present three recent models of the geomagnetic field originating in the Earth’s core. All three modeling approaches are using recent observatory and near-Earth orbiting survey satellite data. In each case...... the specific aims and techniques used by the modelers are described together with a presentation of the main results achieved. The three different modeling approaches are giving similar results. For a snap shot of the core magnetic field at a given epoch and observed at the Earth’s surface, the differences...... only up to degree 8 or 9. For higher time derivatives of core field models, only the very first degrees are robustly derived....
Cubic Polynomials with Rational Roots and Critical Points
Gupta, Shiv K.; Szymanski, Waclaw
2010-01-01
If you want your students to graph a cubic polynomial, it is best to give them one with rational roots and critical points. In this paper, we describe completely all such cubics and explain how to generate them.
Use of Pom Pons to Illustrate Cubic Crystal Structures.
Cady, Susan G.
1997-01-01
Describes a method that uses olefin pom pons to illustrate cubic crystal structure. Facilitates hands-on examination of different packing arrangements such as hexagonal close-packed and cubic close-packed structures. (JRH)
A tilted plane as a gravitational field model
Hale, D. P.
1980-09-01
Gravitational models have been widely used to study the effects of fields on particle motion. The advantages of such models are: (1) They are often easier or cheaper to construct and use than the system which they represent. (2) Particle motion is readily seen and may be photographed. (3) Events lasting for a fraction of a microsecond as, for example, with electrons moving in electrostatic fields, may be demonstrated in models as events which take a few seconds. The article describes the use of a tilted plane as a two-dimensional, uniform gravitational field. It has been used successfully as a sixth-form physics experiment to demonstrate the motion of projectiles fairly close to the Earth over a limited range. Thus it shows the motion of artillery shells (ignoring air resistance) but not of artificial satellites or long-range rockets, for which a simple uniform field model is not valid.
Shape preserving rational bi-cubic function
Directory of Open Access Journals (Sweden)
Malik Zawwar Hussain
2012-11-01
Full Text Available The study is dedicated to the development of shape preserving interpolation scheme for monotone and convex data. A rational bi-cubic function with parameters is used for interpolation. To preserve the shape of monotone and convex data, the simple data dependent constraints are developed on these parameters in each rectangular patch. The developed scheme of this paper is confined, cheap to run and produce smooth surfaces.
Cubic Lienard Equations with Quadratic Damping (Ⅱ)
Institute of Scientific and Technical Information of China (English)
Yu-quan Wang; Zhu-jun Jing
2002-01-01
Applying Hopf bifurcation theory and qualitative theory, we show that the general cubic Lienard equations with quadratic damping have at most three limit cycles. This implies that the guess in which the system has at most two limit cycles is false. We give the sufficient conditions for the system has at most three limit cycles or two limit cycles. We present two examples with three limit cycles or two limit cycles by using numerical simulation.
Method of synthesizing cubic system boron nitride
Energy Technology Data Exchange (ETDEWEB)
Yuzu, S.; Sumiya, H.; Degawa, J.
1987-10-13
A method is described for synthetically growing cubic system boron nitride crystals by using boron nitride sources, solvents for dissolving the boron nitride sources, and seed crystals under conditions of ultra-high pressure and high temperature for maintaining the cubic system boron nitride stable. The method comprises the following steps: preparing a synthesizing vessel having at least two chambers, arrayed in order in the synthesizing vessel so as to be heated according to a temperature gradient; placing the solvents having different eutectic temperatures in each chamber with respect to the boron nitride sources according to the temperature gradient; placing the boron nitride source in contact with a portion of each of the solvents heated at a relatively higher temperature and placing at least a seed crystal in a portion of each of the solvents heated at a relatively lower temperature; and growing at least one cubic system boron nitride crystal in each of the solvents in the chambers by heating the synthesizing vessel for establishing the temperature gradient while maintaining conditions of ultra-high pressure and high temperature.
LATTICE BOLTZMANN EQUATION MODEL IN THE CORIOLIS FIELD
Institute of Scientific and Technical Information of China (English)
FENG SHI-DE; MAO JIANG-YU; ZHANG QIONG
2001-01-01
In a large-scale field of rotational fluid, various unintelligible and surprising dynamic phenomena are produced due to the effect of the Coriolis force. The lattice Boltzmann equation (LBE) model in the Coriolis field is developed based on previous works.[1-4] Geophysical fluid dynamics equations are derived from the model. Numerical simulations have been made on an ideal atmospheric circulation of the Northern Hemisphere by using the model and they reproduce the Rossby wave motion well. Hence the applicability of the model is verified in both theory and experiment.
Relativistic mean-field models and nuclear matter constraints
Energy Technology Data Exchange (ETDEWEB)
Dutra, M.; Lourenco, O.; Carlson, B. V. [Departamento de Fisica, Instituto Tecnologico de Aeronautica-CTA, 12228-900, Sao Jose dos Campos, SP (Brazil); Delfino, A. [Instituto de Fisica, Universidade Federal Fluminense, 24210-150, Boa Viagem, Niteroi, RJ (Brazil); Menezes, D. P.; Avancini, S. S. [Departamento de Fisica, CFM, Universidade Federal de Santa Catarina, CP. 476, CEP 88.040-900, Florianopolis, SC (Brazil); Stone, J. R. [Oxford Physics, University of Oxford, OX1 3PU Oxford (United Kingdom) and Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996 (United States); Providencia, C. [Centro de Fisica Computacional, Department of Physics, University of Coimbra, P-3004-516 Coimbra (Portugal); Typel, S. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Theorie, Planckstrasse 1,D-64291 Darmstadt (Germany)
2013-05-06
This work presents a preliminary study of 147 relativistic mean-field (RMF) hadronic models used in the literature, regarding their behavior in the nuclear matter regime. We analyze here different kinds of such models, namely: (i) linear models, (ii) nonlinear {sigma}{sup 3}+{sigma}{sup 4} models, (iii) {sigma}{sup 3}+{sigma}{sup 4}+{omega}{sup 4} models, (iv) models containing mixing terms in the fields {sigma} and {omega}, (v) density dependent models, and (vi) point-coupling ones. In the finite range models, the attractive (repulsive) interaction is described in the Lagrangian density by the {sigma} ({omega}) field. The isospin dependence of the interaction is modeled by the {rho} meson field. We submit these sets of RMF models to eleven macroscopic (experimental and empirical) constraints, used in a recent study in which 240 Skyrme parametrizations were analyzed. Such constraints cover a wide range of properties related to symmetric nuclear matter (SNM), pure neutron matter (PNM), and both SNM and PNM.
A novel cubic phase of medium chain lipid origin for the delivery of poorly water soluble drugs.
Kossena, Greg A; Charman, William N; Boyd, Ben J; Porter, Christopher J H
2004-09-30
The existence of a novel cubic liquid crystalline phase is described within the pseudo-ternary system comprising lauric acid, monolaurin, and simulated endogenous intestinal fluid (SEIF). This phase behaviour has been characterized using cross-polarizing light microscopy (CPLM), and the structure of the cubic phase identified by small angle X-ray scattering (SAXS). The presence of the cubic phase was found to be temperature sensitive within the 20-37 degrees C range making it putative material for in situ gelation purposes. The cubic phase was shown to have a high capacity to solubilise a model poorly water-soluble drug, cinnarizine, and initial in vitro release data highlight the potential of this phase to provide sustained release. Absorption of cinnarizine from the cubic phase was studied in an unconscious rat model via duodenal administration and blood sampling via the carotid artery. The rate of absorption was significantly reduced when compared to a simple suspension formulation, a likely combination of retarded erosion of the cubic phase together with hindered drug release from the cubic matrix. The results of this study suggest that this cubic phase may potentially be of benefit in the delivery of poorly water-soluble compounds due to its high loading capacity and potential for sustained release. The ability to manipulate this system using temperature may warrant further interest in delivery applications via other routes of administration.
Modeling and analysis of magnetic dipoles in weak magnetic field
Institute of Scientific and Technical Information of China (English)
2008-01-01
The magnetic leakage field distribution resulting from linear defects of a tube sample in the geomagnetic field is modeled according to the magnetic dipole theory.The formula to compute the normal component of the weak magnetic field is deduced based on the spatial distribution of the magnetic dipole.The shape and characteristics of the zero line (an important criterion for magnetic memory testing) of the normal field is analyzed under different longitudinal magnetizations.Results show that the characteristics of the zero line should be considered when the metal magnetic memory testing method is used to find and locate the defect.
Holographic superconductor models with the Maxwell field strength corrections
Pan, Qiyuan; Wang, Bin
2011-01-01
We study the effect of the quadratic field strength correction to the usual Maxwell field on the holographic dual models in the backgrounds of AdS black hole and AdS soliton. We find that in the black hole background, the higher correction to the Maxwell field makes the condensation harder to form and changes the expected relation in the gap frequency. This effect is similar to that caused by the curvature correction. However, in the soliton background we find that different from the curvature effect, the correction to the Maxwell field does not influence the holographic superconductor and insulator phase transition.
Memristive model of hysteretic field emission from carbon nanotube arrays
Gorodetskiy, Dmitriy V.; Gusel'nikov, Artem V.; Shevchenko, Sergey N.; Kanygin, Mikhail A.; Okotrub, Alexander V.; Pershin, Yuriy V.
2016-01-01
Some instances of electron field emitters are characterized by frequency-dependent hysteresis in their current-voltage characteristics. We argue that such emitters can be classified as memristive systems and introduce a general framework to describe their response. As a specific example of our approach, we consider field emission from a carbon nanotube array. Our experimental results demonstrate a low-field hysteresis, which is likely caused by an electrostatic alignment of some of the nanotubes in the applied field. We formulate a memristive model of such phenomena, whose results are in agreement with the experimental results.
Creep motion in a random-field Ising model.
Roters, L; Lübeck, S; Usadel, K D
2001-02-01
We analyze numerically a moving interface in the random-field Ising model which is driven by a magnetic field. Without thermal fluctuations the system displays a depinning phase transition, i.e., the interface is pinned below a certain critical value of the driving field. For finite temperatures the interface moves even for driving fields below the critical value. In this so-called creep regime the dependence of the interface velocity on the temperature is expected to obey an Arrhenius law. We investigate the details of this Arrhenius behavior in two and three dimensions and compare our results with predictions obtained from renormalization group approaches.
Mean-field theory and self-consistent dynamo modeling
Energy Technology Data Exchange (ETDEWEB)
Yoshizawa, Akira; Yokoi, Nobumitsu [Tokyo Univ. (Japan). Inst. of Industrial Science; Itoh, Sanae-I [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics; Itoh, Kimitaka [National Inst. for Fusion Science, Toki, Gifu (Japan)
2001-12-01
Mean-field theory of dynamo is discussed with emphasis on the statistical formulation of turbulence effects on the magnetohydrodynamic equations and the construction of a self-consistent dynamo model. The dynamo mechanism is sought in the combination of the turbulent residual-helicity and cross-helicity effects. On the basis of this mechanism, discussions are made on the generation of planetary magnetic fields such as geomagnetic field and sunspots and on the occurrence of flow by magnetic fields in planetary and fusion phenomena. (author)
Large field inflation models from higher-dimensional gauge theories
Furuuchi, Kazuyuki; Koyama, Yoji
2015-02-01
Motivated by the recent detection of B-mode polarization of CMB by BICEP2 which is possibly of primordial origin, we study large field inflation models which can be obtained from higher-dimensional gauge theories. The constraints from CMB observations on the gauge theory parameters are given, and their naturalness are discussed. Among the models analyzed, Dante's Inferno model turns out to be the most preferred model in this framework.
Large field inflation models from higher-dimensional gauge theories
Energy Technology Data Exchange (ETDEWEB)
Furuuchi, Kazuyuki [Manipal Centre for Natural Sciences, Manipal University, Manipal, Karnataka 576104 (India); Koyama, Yoji [Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan R.O.C. (China)
2015-02-23
Motivated by the recent detection of B-mode polarization of CMB by BICEP2 which is possibly of primordial origin, we study large field inflation models which can be obtained from higher-dimensional gauge theories. The constraints from CMB observations on the gauge theory parameters are given, and their naturalness are discussed. Among the models analyzed, Dante’s Inferno model turns out to be the most preferred model in this framework.
Matrix-model dualities in the collective field formulation
Andric, I
2005-01-01
We establish a strong-weak coupling duality between two types of free matrix models. In the large-N limit, the real-symmetric matrix model is dual to the quaternionic-real matrix model. Using the large-N conformal invariant collective field formulation, the duality is displayed in terms of the generators of the conformal group. The conformally invariant master Hamiltonian is constructed and we conjecture that the master Hamiltonian corresponds to the hermitian matrix model.
Application of the Chameleon Model to EM Field Momentum
Robertson, Glen A.
2008-01-01
The Chameleon scalar field model proposed by Khoury and Weltman presents an alternative mechanism for circumventing the constraints from local tests of gravity by mediating a fifth force for cosmological expansion, which could result in experimental signatures detectable through modest improvements of current laboratory set-ups in the vicinity of oscillating matter. In this paper, the oscillation of a dielectric by a crossed EM field is investigated in light of the Chameleon model. An EM excited Chameleon field-force equation is developed and compared to several EM experiments using the Barium Titanate based dielectric material.
A Two-Field Dilaton Model of Dark Energy
Institute of Scientific and Technical Information of China (English)
LIANG Nan; GAO Chang-Jun; ZHANG Shuang-Nan
2009-01-01
We investigate the cosmological evolution of a two-field model of dark energy,where one is a dilaton field with canonical kinetic energy and the other is a phantom field with a negative kinetic energy term.Phase-plane analysis shows that the "phantom"-dominated scaling solution is the stable late-time attractor of this type of model.We find that during the evolution of the universe,the equation of state w changes from w＞-1 to w＜-1,which is consistent with recent observations.
A cubic autocatalytic reaction in a continuous stirred tank reactor
Energy Technology Data Exchange (ETDEWEB)
Yakubu, Aisha Aliyu; Yatim, Yazariah Mohd [School of Mathematical Sciences, Universiti Sains Malaysia, 11800 USM, Penang Malaysia (Malaysia)
2015-10-22
In the present study, the dynamics of the cubic autocatalytic reaction model in a continuous stirred tank reactor with linear autocatalyst decay is studied. This model describes the behavior of two chemicals (reactant and autocatalyst) flowing into the tank reactor. The behavior of the model is studied analytically and numerically. The steady state solutions are obtained for two cases, i.e. with the presence of an autocatalyst and its absence in the inflow. In the case with an autocatalyst, the model has a stable steady state. While in the case without an autocatalyst, the model exhibits three steady states, where one of the steady state is stable, the second is a saddle point while the last is spiral node. The last steady state losses stability through Hopf bifurcation and the location is determined. The physical interpretations of the results are also presented.
Seasonal Gravity Field Variations from GRACE and Hydrological Models
DEFF Research Database (Denmark)
Andersen, Ole Baltazar; Hinderer, Jacques; Lemoine, Frank G.
2004-01-01
This study present an investigation of the newly released 18 monthly gravity field solutions from the GRACE twin space-crafts with emphasis on the global scale annual gravity field variations observed from GRACE and modeled from hydrological models as annual changes in terrestrial water storage....... Four global hydrological models covering the same period in 2002–2003 as the GRACE observations were investigated to for their mutual consistency in estimates of annual variation in terrestrial water storage and related temporal changes in gravity field. The hydrological models differ by a maximum of 2...... µGal or nearly 5 cm equivalent water storage in selected regions. Integrated over all land masses the standard deviation among the annual signal from the four hydrological models are 0.6 µGal equivalent to around 1.4 cm in equivalent water layer thickness. The estimated accuracy of the annual...
Seasonal Gravity Field Variations from GRACE and Hydrological Models
DEFF Research Database (Denmark)
Andersen, Ole Baltazar; Hinderer, Jacques; Lemoine, Frank G.
2004-01-01
This study present an investigation of the newly released 18 monthly gravity field solutions from the GRACE twin space-crafts with emphasis on the global scale annual gravity field variations observed from GRACE and modeled from hydrological models as annual changes in terrestrial water storage....... Four global hydrological models covering the same period in 2002–2003 as the GRACE observations were investigated to for their mutual consistency in estimates of annual variation in terrestrial water storage and related temporal changes in gravity field. The hydrological models differ by a maximum of 2...... variation in gravity from GRACE is around 0.4 µGal (0.9 cm water layer thickness) on 2000 km length scales. This makes the GRACE observations of terrestrial water storage on global annual scales more accurate than present-day hydrological models....
Theory of optomechanics: Oscillator-field model of moving mirrors
Galley, Chad R; Hu, B L
2012-01-01
In this paper we present a model for the kinematics and dynamics of optomechanics which describe the coupling between an optical field, here modeled by a massless scalar field, and the internal (e.g., determining its reflectivity) and mechanical (e.g., displacement) degrees of freedom of a moveable mirror. As opposed to implementing boundary conditions on the field we highlight the internal dynamics of the mirror which provides added flexibility to describe a variety of setups relevant to current experiments. The inclusion of the internal degrees of freedom in this model allows for a variety of optical activities of mirrors from those exhibiting broadband reflective properties to the cases where reflection is suppressed except for a narrow band centered around the characteristic frequency associated with the mirror's internal dynamics. After establishing the model and the reflective properties of the mirror we show how appropriate parameter choices lead to useful optomechanical models such as the well known B...
Evaluation of candidate geomagnetic field models for IGRF-11
DEFF Research Database (Denmark)
Finlay, Chris; Maus, S.; Beggan, C. D.
2010-01-01
The eleventh generation of the International Geomagnetic Reference Field (IGRF) was agreed in December 2009 by a task force appointed by the International Association of Geomagnetism and Aeronomy (IAGA) Division V Working Group V-MOD. New spherical harmonic main field models for epochs 2005.0 (DGRF...... coefficients is also reported. Maps of differences in the vertical field intensity at Earth’s surface between the candidates and weighted mean models are presented. Candidates with anomalous aspects are identified and efforts made to pinpoint both troublesome coefficients and geographical regions where large...... vector satellite data is demonstrated; based on internal consistency DGRF-2005 has a formal root mean square vector field error over Earth’s surface of 1.0 nT. Difficulties nevertheless remain in accurately forecasting field evolution only five years into the future....
Magnetic field measurements of JT-60SA CS model coil
Energy Technology Data Exchange (ETDEWEB)
Obana, Tetsuhiro, E-mail: obana.tetsuhiro@LHD.nifs.ac.jp [National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); Takahata, Kazuya; Hamaguchi, Shinji; Chikaraishi, Hirotaka; Mito, Toshiyuki; Imagawa, Shinsaku [National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); Kizu, Kaname; Murakami, Haruyuki; Natsume, Kyohei; Yoshida, Kiyoshi [Japan Atomic Energy Agency, 801-1 Mukoyama, Naka, Ibaraki 311-0193 (Japan)
2015-01-15
Highlights: • Magnetic fields of the JT-60SA CS model coil were measured. • While the coil current was held constant at 20 kA, magnetic fields varied slightly with several different long time constants. • We investigated coils consisting of CIC conductors and having long time constants. - Abstract: In a cold test of the JT-60SA CS model coil, which has a quad-pancake configuration consisting of a Nb{sub 3}Sn cable-in-conduit (CIC) conductor, magnetic fields were measured using Hall sensors. For a holding coil current of 20 kA, measured magnetic fields varied slightly with long time constants in the range 17–571 s, which was much longer than the time constant derived from a measurement using a short straight sample. To validate the measurements, the magnetic fields of the model coil were calculated using a computational model representing the positions of Nb{sub 3}Sn strands inside the CIC conductor. The calculated results were in good agreement with the measurements. Consequently, the validity of the magnetic field measurements was confirmed. Next, we investigated other coils consisting of CIC conductors and having long time constants. The only commonality among the coils was the use of CIC conductors. At present, there is no obvious way to prevent generation of such magnetic-field variations with long time constants.
DEFF Research Database (Denmark)
Olsen, Nils; Sabaka, T.J.; Lowes, F.
2005-01-01
When deriving spherical harmonic models of the Earth's magnetic field, low-degree external field contributions are traditionally considered by assuming that their expansion coefficient q(1)(0) varies linearly with the D-st-index, while induced contributions are considered assuming a constant ratio...
Gravity field models derived from Swarm GPS data
Teixeira da Encarnação, João; Arnold, Daniel; Bezděk, Aleš; Dahle, Christoph; Doornbos, Eelco; van den IJssel, Jose; Jäggi, Adrian; Mayer-Gürr, Torsten; Sebera, Josef; Visser, Pieter; Zehentner, Norbert
2016-07-01
It is of great interest to numerous geophysical studies that the time series of global gravity field models derived from Gravity Recovery and Climate Experiment (GRACE) data remains uninterrupted after the end of this mission. With this in mind, some institutes have been spending efforts to estimate gravity field models from alternative sources of gravimetric data. This study focuses on the gravity field solutions estimated from Swarm global positioning system (GPS) data, produced by the Astronomical Institute of the University of Bern, the Astronomical Institute (ASU, Czech Academy of Sciences) and Institute of Geodesy (IfG, Graz University of Technology). The three sets of solutions are based on different approaches, namely the celestial mechanics approach, the acceleration approach and the short-arc approach, respectively. We derive the maximum spatial resolution of the time-varying gravity signal in the Swarm gravity field models to be degree 12, in comparison with the more accurate models obtained from K-band ranging data of GRACE. We demonstrate that the combination of the GPS-driven models produced with the three different approaches improves the accuracy in all analysed monthly solutions, with respect to any of them. In other words, the combined gravity field model consistently benefits from the individual strengths of each separate solution. The improved accuracy of the combined model is expected to bring benefits to the geophysical studies during the period when no dedicated gravimetric mission is operational.
Assessing a soft twin tunneling numerical model using field data
Institute of Scientific and Technical Information of China (English)
Ke-shuan Ma; Lie-yun Ding
2009-01-01
Using a five-floor building affected by the Yangtze River highway tunnels in Wuhan as the engineering background, we have constructed a free-field model and a coupled model to study the soil, lining, foundations and upper structure, and analyze the rules of movements of building foundation and ground induced by single tunnel and twin tunnel excavation with the Finite Element Analysis method. It is shown that for the coupled model, the longitudinal displacement of each foundation increases slowly when the tunnel face gets close to the foundation section and then increases fast when the tunnel face moves away from the foundation during the single and twin tunneling. For a single tunnel, the surface settlements are overestimated by the free-field and coupled tunnel. This might be crucial in urban areas. Regarding the maximum settlements and the width of the settlement trough, the difference between the free-field model and the coupled model is quite obvious. This comparison with the field measurement value reveals that the coupled model seems to be superior to the free-field model. These results are of instructive significance for design and excavation.
Geomagnetic core field models in the satellite era
DEFF Research Database (Denmark)
Lesur, Vincent; Olsen, Nils; Thomson, Alan W. P.
2011-01-01
After a brief review of the theoretical basis and difficulties that modelers are facing, we present three recent models of the geomagnetic field originating in the Earth’s core. All three modeling approaches are using recent observatory and near-Earth orbiting survey satellite data. In each case ...... only up to degree 8 or 9. For higher time derivatives of core field models, only the very first degrees are robustly derived.......After a brief review of the theoretical basis and difficulties that modelers are facing, we present three recent models of the geomagnetic field originating in the Earth’s core. All three modeling approaches are using recent observatory and near-Earth orbiting survey satellite data. In each case...... the specific aims and techniques used by the modelers are described together with a presentation of the main results achieved. The three different modeling approaches are giving similar results. For a snap shot of the core magnetic field at a given epoch and observed at the Earth’s surface, the differences...
3D computation of non-linear eddy currents: Variational method and superconducting cubic bulk
Pardo, Enric; Kapolka, Milan
2017-09-01
Computing the electric eddy currents in non-linear materials, such as superconductors, is not straightforward. The design of superconducting magnets and power applications needs electromagnetic computer modeling, being in many cases a three-dimensional (3D) problem. Since 3D problems require high computing times, novel time-efficient modeling tools are highly desirable. This article presents a novel computing modeling method based on a variational principle. The self-programmed implementation uses an original minimization method, which divides the sample into sectors. This speeds-up the computations with no loss of accuracy, while enabling efficient parallelization. This method could also be applied to model transients in linear materials or networks of non-linear electrical elements. As example, we analyze the magnetization currents of a cubic superconductor. This 3D situation remains unknown, in spite of the fact that it is often met in material characterization and bulk applications. We found that below the penetration field and in part of the sample, current flux lines are not rectangular and significantly bend in the direction parallel to the applied field. In conclusion, the presented numerical method is able to time-efficiently solve fully 3D situations without loss of accuracy.
Variability modes in core flows inverted from geomagnetic field models
Pais, Maria A; Schaeffer, Nathanaël
2014-01-01
We use flows that we invert from two geomagnetic field models spanning centennial time periods (gufm1 and COV-OBS), and apply Principal Component Analysis and Singular Value Decomposition of coupled fields to extract the main modes characterizing their spatial and temporal variations. The quasi geostrophic flows inverted from both geomagnetic field models show similar features. However, COV-OBS has a less energetic mean flow and larger time variability. The statistical significance of flow components is tested from analyses performed on subareas of the whole domain. Bootstrapping methods are also used to extract robust flow features required by both gufm1 and COV-OBS. Three main empirical circulation modes emerge, simultaneously constrained by both geomagnetic field models and expected to be robust against the particular a priori used to build them. Mode 1 exhibits three large robust vortices at medium/high latitudes, with opposite circulation under the Atlantic and the Pacific hemispheres. Mode 2 interesting...
DRAPING OF THE INTERSTELLAR MAGNETIC FIELD OVER THE HELIOPAUSE: A PASSIVE FIELD MODEL
Energy Technology Data Exchange (ETDEWEB)
Isenberg, Philip A.; Forbes, Terry G.; Möbius, Eberhard [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States)
2015-06-01
As the local interstellar plasma flows past our heliosphere, it is slowed and deflected around the magnetic obstacle of the heliopause. The interstellar magnetic field, frozen into this plasma, then becomes draped around the heliopause in a characteristic manner. We derive the analytical solution for this draped magnetic field in the limit of weak field intensity, assuming an ideal potential flow around the heliopause, which we model as a Rankine half-body. We compare the structure of the model magnetic field with observed properties of the Interstellar Boundary Explorer (IBEX) ribbon and with in situ observations at the Voyager 1 spacecraft. We find reasonable qualitative agreement, given the idealizations of the model. This agreement lends support to the secondary ENA model of the IBEX ribbon and to the interpretation that Voyager 1 has crossed the heliopause. We also predict that the magnetic field measured by Voyager 2 after it crosses the heliopause will not be significantly rotated away from the direction of the undisturbed interstellar field.
Mean Field Games Models-A Brief Survey
Gomes, Diogo A.
2013-11-20
The mean-field framework was developed to study systems with an infinite number of rational agents in competition, which arise naturally in many applications. The systematic study of these problems was started, in the mathematical community by Lasry and Lions, and independently around the same time in the engineering community by P. Caines, Minyi Huang, and Roland Malhamé. Since these seminal contributions, the research in mean-field games has grown exponentially, and in this paper we present a brief survey of mean-field models as well as recent results and techniques. In the first part of this paper, we study reduced mean-field games, that is, mean-field games, which are written as a system of a Hamilton-Jacobi equation and a transport or Fokker-Planck equation. We start by the derivation of the models and by describing some of the existence results available in the literature. Then we discuss the uniqueness of a solution and propose a definition of relaxed solution for mean-field games that allows to establish uniqueness under minimal regularity hypothesis. A special class of mean-field games that we discuss in some detail is equivalent to the Euler-Lagrange equation of suitable functionals. We present in detail various additional examples, including extensions to population dynamics models. This section ends with a brief overview of the random variables point of view as well as some applications to extended mean-field games models. These extended models arise in problems where the costs incurred by the agents depend not only on the distribution of the other agents, but also on their actions. The second part of the paper concerns mean-field games in master form. These mean-field games can be modeled as a partial differential equation in an infinite dimensional space. We discuss both deterministic models as well as problems where the agents are correlated. We end the paper with a mean-field model for price impact. © 2013 Springer Science+Business Media New York.
Multi-scale gravity field modeling in space and time
Wang, Shuo; Panet, Isabelle; Ramillien, Guillaume; Guilloux, Frédéric
2016-04-01
The Earth constantly deforms as it undergoes dynamic phenomena, such as earthquakes, post-glacial rebound and water displacement in its fluid envelopes. These processes have different spatial and temporal scales and are accompanied by mass displacements, which create temporal variations of the gravity field. Since 2002, the GRACE satellite missions provide an unprecedented view of the gravity field spatial and temporal variations. Gravity models built from these satellite data are essential to study the Earth's dynamic processes (Tapley et al., 2004). Up to present, time variations of the gravity field are often modelled using spatial spherical harmonics functions averaged over a fixed period, as 10 days or 1 month. This approach is well suited for modeling global phenomena. To better estimate gravity related to local and/or transient processes, such as earthquakes or floods, and adapt the temporal resolution of the model to its spatial resolution, we propose to model the gravity field using localized functions in space and time. For that, we build a model of the gravity field in space and time with a four-dimensional wavelet basis, well localized in space and time. First we design the 4D basis, then, we study the inverse problem to model the gravity field from the potential differences between the twin GRACE satellites, and its regularization using prior knowledge on the water cycle. Our demonstration of surface water mass signals decomposition in time and space is based on the use of synthetic along-track gravitational potential data. We test the developed approach on one year of 4D gravity modeling and compare the reconstructed water heights to those of the input hydrological model. Perspectives of this work is to apply the approach on real GRACE data, addressing the challenge of a realistic noise, to better describe and understand physical processus with high temporal resolution/low spatial resolution or the contrary.
NOC model of the earth's main magnetic field
Institute of Scientific and Technical Information of China (English)
XU; Wenyao(徐文耀)
2003-01-01
The method of natural orthogonal components (NOC) is used to analyze the earth's main magnetic field IGRF 1900-2000, and the NOC model of the field is established. The first step of the analysis is to calculate eigen modes of the field from the Gauss coefficients of IGRF 1900-2000. Then the magnetic field for each epoch is expanded in a series at the basic function set constructed by the eigen modes, and the intensity coefficients of the eigen modes are calculated. Test of the convergency and stability of the NOC model shows that the model has very short series and much rapid convergency in comparison with the conventional spherical harmonic models of IGRF. Comparison of the eigen modes obtained from different IGRF model groups indicates that the low-degree eigen modes are rather stable, while the high-degree modes show a relatively large variability. The physical meaning of the eigen modes in the NOC model is discussed, and an interesting relationship is found between the spatial structure of the main field and its secular variation.
Critical fluctuations for quantum mean-field models
Energy Technology Data Exchange (ETDEWEB)
Fannes, M.; Kossakowski, A.; Verbeure, A. (Univ. Louvain (Belgium))
1991-11-01
A Ginzburg-Landau-type approximation is proposed for the local Gibbs states for quantum mean-field models that leads to the exact thermodynamics. Using this approach, the spin fluctuations are computed for some spin-1/2 models. At the critical temperature, the distribution function showing abnormal fluctuations is found explicitly.
Longitudinal static-field model for HD lasers
Baets, R.; Lagasse, P. E.
1984-01-01
A new static model for double-heterostructure lasers is presented which can take into account longitudinal effects in the cavity. The model makes use of the beam-propagation method to calculate the field propagation through the lasing waveguide structure.
Chiral field theories as models for hadron substructure
Energy Technology Data Exchange (ETDEWEB)
Kahana, S.H.
1987-03-01
A model for the nucleon as soliton of quarks interacting with classical meson fields is described. The theory, based on the linear sigma model, is renormalizable and capable of including sea quarks straightforwardly. Application to nuclear matter is made in a Wigner-Seitz approximation.
Modelling of evapotranspiration at field and landscape scales. Abstract
DEFF Research Database (Denmark)
Overgaard, Jesper; Butts, M.B.; Rosbjerg, Dan
2002-01-01
observations from a nearby weather station. Detailed land-use and soil maps were used to set up the model. Leaf area index was derived from NDVI (Normalized Difference Vegetation Index) images. To validate the model at field scale the simulated evapotranspiration rates were compared to eddy...
Non Linear Force Free Field Modeling for a Pseudostreamer
Karna, Nishu; Savcheva, Antonia; Gibson, Sarah; Tassev, Svetlin V.
2017-08-01
In this study we present a magnetic configuration of a pseudostreamer observed on April 18, 2015 on southern west limb embedding a filament cavity. We constructed Non Linear Force Free Field (NLFFF) model using the flux rope insertion method. The NLFFF model produces the three-dimensional coronal magnetic field constrained by observed coronal structures and photospheric magnetogram. SDO/HMI magnetogram was used as an input for the model. The high spatial and temporal resolution of the SDO/AIA allows us to select best-fit models that match the observations. The MLSO/CoMP observations provide full-Sun observations of the magnetic field in the corona. The primary observables of CoMP are the four Stokes parameters (I, Q, U, V). In addition, we perform a topology analysis of the models in order to determine the location of quasi-separatrix layers (QSLs). QSLs are used as a proxy to determine where the strong electric current sheets can develop in the corona and also provide important information about the connectivity in complicated magnetic field configuration. We present the major properties of the 3D QSL and FLEDGE maps and the evolution of 3D coronal structures during the magnetofrictional process. We produce FORWARD-modeled observables from our NLFFF models and compare to a toy MHD FORWARD model and the observations.
Multilayer piezoelectric transducer models combined with Field II
DEFF Research Database (Denmark)
Bæk, David; Willatzen, Morten; Jensen, Jørgen Arendt
2012-01-01
with a polymer ring, and submerged into water. The transducer models are developed to account for any external electrical loading impedance in the driving circuit. The models are adapted to calculate the surface acceleration needed by the Field II software in predicting pressure pulses at any location in front...
Institute of Scientific and Technical Information of China (English)
辜旭赞; 张兵; 王明欢
2011-01-01
In this paper, from the Navier-Stokes primitive equations and Eulerian operator, forecasting equations are deduced with 2-order time and space differential remainder by Taylor series expansion, and incorporated to the Bicubic Numerical Model (BiNM for short), which is with a quasi-Lagrangian integration scheme of fitting cubic spline/bicubic surface to all physical variables in atmospheric equation sets on spherical discrete meshes. Their first-order and second-order derivatives as well as their upstream points were determined, and discrete time integration was performed in cubic space for the governing equations, I.e.With a new algorithm of "fitting bicubic surface - time step integration - fitting bicubic surface -......". Then,BiNM's mathematical foundation of numerical analysis was discussed for the cubic spline and its mathematical polar characters. It was pointed out that, as a spectrum model, BiNM shows mathematical "convergence" of the cubic spline and the bicubic surface contracting to the original function as well as its first-order and second-order derivatives, with the "optimality" of the second-order derivative of the cubic spline being optimal approximation to that of the original function. It was indicated that Hermite bicubic patches are equivalent in performing operation to the secondary derivative "mesh" variables. It was identified that the slope and curvature of the centred difference are respectively three-point smooth of that of the cubic spline. Using a global BiNM with latitude-longitude grids, and keeping the non-static and total field compressible, adiabatic and non-frictional, and running the so called "shallow atmosphere" equations in the spherical coordinate, and along with a quasi -Lagrangian time integration scheme, an ideal global simulation case was shown by adopting the re-analysis data of NCEP for getting an initial model atmosphere. Lastly, we had to say that, because atmospheric motion can be essentially non-linear, future Bi
Energy Density Bounds in Cubic Quasi-Topological Cosmology
dS, U Camara; Sotkov, G M
2013-01-01
We investigate the thermodynamical and causal consistency of cosmological models of the cubic Quasi-Topological Gravity (QTG) in four dimensions, as well as their phenomenological consequences. Specific restrictions on the maximal values of the matter densities are derived by requiring the apparent horizon's entropy to be a non-negative, non-decreasing function of time. The QTG counterpart of the Einstein-Hilbert (EH) gravity model of linear equation of state is studied in detail. An important feature of this particular QTG cosmological model is the new early-time acceleration period of the evolution of the Universe, together with the standard late-time acceleration present in the original EH model. The QTG correction to the causal diamond's volume is also calculated.
Simplified Atmospheric Dispersion Model andModel Based Real Field Estimation System ofAir Pollution
Institute of Scientific and Technical Information of China (English)
2015-01-01
The atmospheric dispersion model has been well developed and applied in pollution emergency and prediction. Based on thesophisticated air diffusion model, this paper proposes a simplified model and some optimization about meteorological andgeological conditions. The model is suitable for what is proposed as Real Field Monitor and Estimation system. The principle ofsimplified diffusion model and its optimization is studied. The design of Real Field Monitor system based on this model and itsfundamental implementations are introduced.
Random field distributed Heisenberg model on a thin film geometry
Energy Technology Data Exchange (ETDEWEB)
Akıncı, Ümit, E-mail: umit.akinci@deu.edu.tr
2014-11-15
The effects of the bimodal random field distribution on the thermal and magnetic properties of the Heisenberg thin film have been investigated by making use of a two spin cluster with the decoupling approximation. Particular attention has been devoted to the obtaining of phase diagrams and magnetization behaviors. The physical behaviors of special as well as tricritical points are discussed for a wide range of selected Hamiltonian parameters. For example, it is found that when the strength of a magnetic field increases, the locations of the special point (which is the ratio of the surface exchange interaction and the exchange interaction of the inner layers that makes the critical temperature of the film independent of the thickness) in the related plane decrease. Moreover, tricritical behavior has been obtained for higher values of the magnetic field, and influences of the varying Hamiltonian parameters on its behavior have been elucidated in detail in order to have a better understanding of the mechanism underlying the considered system. - Highlights: • Effect of bimodal random field distribution within the Heisenberg model is investigated. • Phase diagrams of the random field Heisenberg model in a thin film geometry are obtained. • Effect of the random field on the magnetic properties is obtained. • Variation of the special point with random field is determined. • Variation of the tricritical point with random field is determined.
Minimally coupled scalar field cosmology in anisotropic cosmological model
Singh, C. P.; Srivastava, Milan
2017-02-01
We study a spatially homogeneous and anisotropic cosmological model in the Einstein gravitational theory with a minimally coupled scalar field. We consider a non-interacting combination of scalar field and perfect fluid as the source of matter components which are separately conserved. The dynamics of cosmic scalar fields with a zero rest mass and an exponential potential are studied, respectively. We find that both assumptions of potential along with the average scale factor as an exponential function of scalar field lead to the logarithmic form of scalar field in each case which further gives power-law form of the average scale factor. Using these forms of the average scale factor, exact solutions of the field equations are obtained to the metric functions which represent a power-law and a hybrid expansion, respectively. We find that the zero-rest-mass model expands with decelerated rate and behaves like a stiff matter. In the case of exponential potential function, the model decelerates, accelerates or shows the transition depending on the parameters. The isotropization is observed at late-time evolution of the Universe in the exponential potential model.
A hybrid random field model for scalable statistical learning.
Freno, A; Trentin, E; Gori, M
2009-01-01
This paper introduces hybrid random fields, which are a class of probabilistic graphical models aimed at allowing for efficient structure learning in high-dimensional domains. Hybrid random fields, along with the learning algorithm we develop for them, are especially useful as a pseudo-likelihood estimation technique (rather than a technique for estimating strict joint probability distributions). In order to assess the generality of the proposed model, we prove that the class of pseudo-likelihood distributions representable by hybrid random fields strictly includes the class of joint probability distributions representable by Bayesian networks. Once we establish this result, we develop a scalable algorithm for learning the structure of hybrid random fields, which we call 'Markov Blanket Merging'. On the one hand, we characterize some complexity properties of Markov Blanket Merging both from a theoretical and from the experimental point of view, using a series of synthetic benchmarks. On the other hand, we evaluate the accuracy of hybrid random fields (as learned via Markov Blanket Merging) by comparing them to various alternative statistical models in a number of pattern classification and link-prediction applications. As the results show, learning hybrid random fields by the Markov Blanket Merging algorithm not only reduces significantly the computational cost of structure learning with respect to several considered alternatives, but it also leads to models that are highly accurate as compared to the alternative ones.
A cavitation model based on Eulerian stochastic fields
Magagnato, F.; Dumond, J.
2013-12-01
Non-linear phenomena can often be described using probability density functions (pdf) and pdf transport models. Traditionally the simulation of pdf transport requires Monte-Carlo codes based on Lagrangian "particles" or prescribed pdf assumptions including binning techniques. Recently, in the field of combustion, a novel formulation called the stochastic-field method solving pdf transport based on Eulerian fields has been proposed which eliminates the necessity to mix Eulerian and Lagrangian techniques or prescribed pdf assumptions. In the present work, for the first time the stochastic-field method is applied to multi-phase flow and in particular to cavitating flow. To validate the proposed stochastic-field cavitation model, two applications are considered. Firstly, sheet cavitation is simulated in a Venturi-type nozzle. The second application is an innovative fluidic diode which exhibits coolant flashing. Agreement with experimental results is obtained for both applications with a fixed set of model constants. The stochastic-field cavitation model captures the wide range of pdf shapes present at different locations.
Minimally coupled scalar field cosmology in anisotropic cosmological model
Indian Academy of Sciences (India)
C P SINGH; MILAN SRIVASTAVA
2017-02-01
We study a spatially homogeneous and anisotropic cosmological model in the Einstein gravitational theory with a minimally coupled scalar field. We consider a non-interacting combination of scalar field and perfect fluid as the source of matter components which are separately conserved. The dynamics of cosmic scalar fields with a zero rest mass and an exponential potential are studied, respectively. We find that both assumptions of potential along with the average scale factor as an exponential function of scalar field lead to the logarithmic formof scalar field in each case which further gives power-law form of the average scale factor. Using these forms of the average scale factor, exact solutions of the field equations are obtained to the metric functions which represent a power-law and a hybrid expansion, respectively. We find that the zero-rest-mass model expands with decelerated rate and behaves like a stiff matter. In the case of exponential potential function, the model decelerates, accelerates or shows the transition depending on the parameters. The isotropization is observed at late-time evolution of the Universe in the exponential potential model.
Vacancy-induced mechanical stabilization of cubic tungsten nitride
Balasubramanian, Karthik; Khare, Sanjay; Gall, Daniel
2016-11-01
First-principles methods are employed to determine the structural, mechanical, and thermodynamic reasons for the experimentally reported cubic WN phase. The defect-free rocksalt phase is both mechanically and thermodynamically unstable, with a negative single crystal shear modulus C44=-86 GPa and a positive enthalpy of formation per formula unit Hf=0.623 eV with respect to molecular nitrogen and metallic W. In contrast, WN in the NbO phase is stable, with C44=175 GPa and Hf=-0.839 eV . A charge distribution analysis reveals that the application of shear strain along [100] in rocksalt WN results in an increased overlap of the t2 g orbitals which causes electron migration from the expanded to the shortened W-W bond axes, yielding a negative shear modulus due to an energy reduction associated with new bonding states 8.1-8.7 eV below the Fermi level. A corresponding shear strain in WN in the NbO phase results in an energy increase and a positive shear modulus. The mechanical stability transition from the NaCl to the NbO phase is explored using supercell calculations of the NaCl structure containing Cv=0 %-25 % cation and anion vacancies, while keeping the N-to-W ratio constant at unity. The structure is mechanically unstable for Cvconcentration, the isotropic elastic modulus E of cubic WN is zero, but increases steeply to E =445 GPa for Cv=10 % , and then less steeply to E =561 GPa for Cv=25 % . Correspondingly, the hardness estimated using Tian's model increases from 0 to 15 to 26 GPa as Cv increases from 5% to 10% to 25%, indicating that a relatively small vacancy concentration stabilizes the cubic WN phase and that the large variations in reported mechanical properties of WN can be attributed to relatively small changes in Cv.
Magnetic Behaviour of the Cubic La(Fe,Al)13 Compounds
Kraan, A.M. van der; Buschow, K.H.J.; Palstra, T.T.M.
1983-01-01
The magnetic properties of the cubic NaZn13 type pseudobinary compounds LaFexAl13-x were studied in the temperature range T=4.2 - 300 K by means of 57Fe-Mössbauer spectroscopy, magnetization and zero-field susceptibility measurements. The compounds LaFexAl13-x show a rather peculiar concentration de
New exact models for anisotropic matter with electric field
Indian Academy of Sciences (India)
JEFTA M SUNZU; PETRO DANFORD
2017-09-01
We generate two newexact models for the Einstein–Maxwell field equations. In our models, we consider the stellar object that is anisotropic and charged with linear equation of state consistent with quark stars. We have a new choice of measure of anisotropy that is physically reasonable. It is interesting that in our models we regain previous isotropic results as special cases. Isotropic exact solutions regained include models by Komathiraj and Maharaj; Mak and Harko; and Misner and Zapolsky. We can also obtain particular anisotropic models obtained by Maharaj, Sunzu, and Ray. The exact solutions corresponding to our models are found explicitly in terms of elementary functions. The graphical plots generated for the matter variables and the electric field are well behaved. We also generate relativistic stellar masses consistent with observations.
Phase field modeling of flexoelectricity in solid dielectrics
Chen, H. T.; Zhang, S. D.; Soh, A. K.; Yin, W. Y.
2015-07-01
A phase field model is developed to study the flexoelectricity in nanoscale solid dielectrics, which exhibit both structural and elastic inhomogeneity. The model is established for an elastic homogeneous system by taking into consideration all the important non-local interactions, such as electrostatic, elastic, polarization gradient, as well as flexoelectric terms. The model is then extended to simulate a two-phase system with strong elastic inhomogeneity. Both the microscopic domain structures and the macroscopic effective piezoelectricity are thoroughly studied using the proposed model. The results obtained show that the largest flexoelectric induced polarization exists at the interface between the matrix and the inclusion. The effective piezoelectricity is greatly influenced by the inclusion size, volume fraction, elastic stiffness, and the applied stress. The established model in the present study can provide a fundamental framework for computational study of flexoelectricity in nanoscale solid dielectrics, since various boundary conditions can be easily incorporated into the phase field model.
Accuracy Analysis for SST Gravity Field Model in China
Institute of Scientific and Technical Information of China (English)
LUO Jia; LUO Zhicai; ZOU Xiancai; WANG Haihong
2006-01-01
Taking China as the region for test, the potential of the new satellite gravity technique, satellite-to-satellite tracking for improving the accuracy of regional gravity field model is studied. With WDM94 as reference, the gravity anomaly residuals of three models, the latest two GRACE global gravity field model (EIGEN_GRACE02S, GGM02S) and EGM96, are computed and compared. The causes for the differences among the residuals of the three models are discussed. The comparison between the residuals shows that in the selected region, EIGEN_GRACE02S or GGM02S is better than EGM96 in lower degree part (less than 110 degree). Additionally, through the analysis of the model gravity anomaly residuals, it is found that some systematic errors with periodical properties exist in the higher degree part of EIGEN and GGM models, the results can also be taken as references in the validation of the SST gravity data.
Some effects of quiet geomagnetic field changes upon values used for main field modeling
Campbell, W.H.
1987-01-01
The effects of three methods of data selection upon the assumed main field levels for geomagnetic observatory records used in main field modeling were investigated for a year of very low solar-terrestrial activity. The first method concerned the differences between the year's average of quiet day field values and the average of all values during the year. For H these differences were 2-3 gammas, for D they were -0.04 to -0.12???, for Z the differences were negligible. The second method of selection concerned the effects of the daytime internal Sq variations upon the daily mean values of field. The midnight field levels when the Sq currents were a minimum deviated from the daily mean levels by as much as 4-7 gammas in H and Z but were negligible for D. The third method of selection was designed to avoid the annual and semi-annual quiet level changes of field caused by the seasonal changes in the magnetosphere. Contributions from these changes were found to be as much as 4-7 gammas in quiet years and expected to be greater than 10 gammas in active years. Suggestions for improved methods of improved data selection in main field modeling are given. ?? 1987.
Ridley, Victoria A.; Holme, Richard
2016-03-01
We present new models of Jupiter's internal magnetic field and secular variation from all available direct measurements from three decades of spacecraft observation. A regularized minimum norm approach allows the creation of smooth, numerically stable models displaying a high degree of structure. External field from the magnetodisk is modeled iteratively for each orbit. Jupiter's inner magnetosphere is highly stable with time, with no evidence for variation with solar activity. We compare two spherical harmonic models, one assuming a field constant in time and a second allowing for linear time variation. Including secular variation improves data fit with fewer additional parameters than increasing field complexity. Our favored solution indicates a ˜0.012% yr-1 increase in Jupiter's dipole magnetic moment from 1973 to 2003; this value is roughly one quarter of that for Earth. Inaccuracies in determination of the planetary reference frame cannot explain all the observed secular variation. Should more structure be allowed in the solutions, we find the northern hemispherical configuration resembles recent models based on satellite auroral footprint locations, and there is also evidence of a possible patch of reversed polar flux seen at the expected depth of the dynamo region, resembling that found at Earth and with implications for the Jovian interior. Finally, using our preferred model, we infer flow dynamics at the top of Jupiter's dynamo source. Though highly speculative, the results produce several gyres with some symmetry about the equator, similar to those seen at Earth's core-mantle boundary, suggesting motion on cylinders aligned with the rotation axis.
Integrated modeling and 3D visualization for mine complex fields
Institute of Scientific and Technical Information of China (English)
LI Zhong-xue; SUN En-ji; LI Cui-ping; MA Bin
2007-01-01
Proposed a novel approach to the problem of mine complex fields in a perspective of digital modeling and visual representation, and it aimed at developing a theoretical framework for mine complex fields with the factors and their relationships delineated in a unified manner and at building a prototype for an integrated system of methods, models,and techniques with mine complex fields modeled digitally and represented visually. Specifically, the paper addressed the issues of data mining and knowledge discovery techniques as used in the processing of geological and ore deposit samples, digital modeling techniques as used in the description of mine complex fields, 3D visual simulation techniques as used in the representation of ore bodies and underground excavations, seamless interfacing techniques with other systems such as CAD and web GIS as used in the restructuring of 2D data into 3D models and mapping of 3D models onto 2D graphics, and implementation techniques as used in the case of building a web based prototype system for the integrated modeling and visualization of underground mines.
Liu, Dong; Hostetler, Chris; Cook, Anthony; Miller, Ian; Hair, Johnathan
2011-11-01
High spectral resolution lidars (HSRLs) are increasingly being deployed on aircraft and called for on future space-based missions. The HSRL technique relies on spectral discrimination of the atmospheric backscatter signals to enable independent, unambiguous retrieval of aerosol extinction and backscatter. A compact, monolithic field-widened Michelson interferometer is being developed as the spectral discrimination filter for an HSRL system at NASA Langley Research Center. The interferometer consists of a cubic beam splitter, a solid glass arm, and an air arm. The spacer that connects the air arm mirror to the main part of the interferometer is designed to optimize thermal compensation such that the maximum interference can be tuned with great precision to the transmitted laser wavelength. In this paper, a comprehensive radiometric model for the field-widened Michelson interferometeric spectral filter is presented. The model incorporates the angular distribution and finite cross sectional area of the light source, reflectance of all surfaces, loss of absorption, and lack of parallelism between the air-arm and solid arm, etc. The model can be used to assess the performance of the interferometer and thus it is a useful tool to evaluate performance budgets and to set optical specifications for new designs of the same basic interferometer type.
Liu, Dong; Hostetler, Chris; Miller, Ian; Cook, Anthony; Hair, Jonathan
2011-10-01
High spectral resolution lidars (HSRLs) designed for aerosol and cloud remote sensing are increasingly being deployed on aircraft and called for on future space-based missions. The HSRL technique relies on spectral discrimination of the atmospheric backscatter signals to enable independent, unambiguous retrieval of aerosol extinction and backscatter. A compact, monolithic field-widened Michelson interferometer is being developed as the spectral discrimination filter for an HSRL system at NASA Langley Research Center. The Michelson interferometer consists of a cubic beam splitter, a solid glass arm, and an air arm. The spacer that connects the air arm mirror to the main part of the interferometer is designed to optimize thermal compensation such that the frequency of maximum interference can be tuned with great precision to the transmitted laser wavelength. In this paper, a comprehensive radiometric model for the field-widened Michelson interferometeric spectral filter is presented. The model incorporates the angular distribution and finite cross sectional area of the light source, reflectance of all surfaces, loss of absorption, and lack of parallelism between the airarm and solid arm, etc. The model can be used to assess the performance of the interferometer and thus it is a useful tool to evaluate performance budgets and to set optical specifications for new designs of the same basic interferometer type.
Dynamics in Nonlocal Cosmological Models Derived from String Field Theory
Joukovskaya, Liudmila
2007-01-01
A general class of nonlocal cosmological models is considered. A new method for solving nonlocal Friedmann equations is proposed, and solutions of the Friedmann equations with nonlocal operator are presented. The cosmological properties of these solutions are discussed. Especially indicated is $p$-adic cosmological model in which we have obtained nonsingular bouncing solution and string field theory tachyon model in which we have obtained full solution of nonlocal Friedmann equations with $w=...
Spinor-Helicity Three-Point Amplitudes from Local Cubic Interactions
Conde, Eduardo; Mkrtchyan, Karapet
2016-01-01
We make an explicit link between the cubic interactions of off-shell fields and the on-shell three-point amplitudes in four dimensions. Both the cubic interactions and the on-shell three-point amplitudes had been independently classified in the literature, but their relation has not been made explicit. The aim of this note is to provide such a relation and discuss similarities and differences of their constructions. For the completeness of our analysis, we also derive the covariant form of all parity-odd massless vertices.
Asymptotics of Mean-Field O( N) Models
Kirkpatrick, Kay; Nawaz, Tayyab
2016-12-01
We study mean-field classical N-vector models, for integers N≥2. We use the theory of large deviations and Stein's method to study the total spin and its typical behavior, specifically obtaining non-normal limit theorems at the critical temperatures and central limit theorems away from criticality. Important special cases of these models are the XY (N=2) model of superconductors, the Heisenberg (N=3) model [previously studied in Kirkpatrick and Meckes (J Stat Phys 152:54-92, 2013) but with a correction to the critical distribution here], and the Toy (N=4) model of the Higgs sector in particle physics.
Mean field theory, topological field theory, and multi-matrix models
Energy Technology Data Exchange (ETDEWEB)
Dijkgraaf, R. (Princeton Univ., NJ (USA). Joseph Henry Labs.); Witten, E. (Institute for Advanced Study, Princeton, NJ (USA). School of Natural Sciences)
1990-10-08
We show that the genus zero correlation functions of an arbitrary topological field theory coupled to two-dimensional topological gravity are determined by an appropriate Landau-Ginzburg potential. We determine the potentials that arise for topological sigma models with CP{sup 1} or a Calabi-Yau manifold for target space. We present substantial evidence that the multi-matrix models that have been studied recently are equivalent to certain topological field theories coupled to topological gravity. We also describe a topological version of the general 'string equation'. (orig.).
Mean field theory, topological field theory, and multi-matrix models
Dijkgraaf, Robbert; Witten, Edward
1990-10-01
We show that the genus zero correlation functions of an arbitrary topological field theory coupled to two-dimensional topological gravity are determined by an appropriate Landau-Ginzburg potential. We determine the potentials that arise for topological sigma models with CP 1 or a Calabi-Yau manifold for target space. We present substantial evidence that the multi-matrix models that have been studied recently are equivalent to certain topological field theories coupled to topological gravity. We also describe a topological version of the general "string equation".
Cherenkov and Scintillation Properties of Cubic Zirconium
Christl, M.J.; Adams, J.H.; Parnell, T.A.; Kuznetsov, E.N.
2008-01-01
Cubic zirconium (CZ) is a high index of refraction (n =2.17) material that we have investigated for Cherenkov counter applications. Laboratory and proton accelerator tests of an 18cc sample of CZ show that the expected fast Cherenkov response is accompanied by a longer scintillation component that can be separated by pulse shaping. This presents the possibility of novel particle spectrometers which exploits both properties of CZ. Other high index materials being examined for Cherenkov applications will be discussed. Results from laboratory tests and an accelerator exposure will be presented and a potential application in solar energetic particle instruments will be discussed
Generalized fairing algorithm of parametric cubic splines
Institute of Scientific and Technical Information of China (English)
WANG Yuan-jun; CAO Yuan
2006-01-01
Kjellander has reported an algorithm for fairing uniform parametric cubic splines. Poliakoff extended Kjellander's algorithm to non-uniform case. However, they merely changed the bad point's position, and neglected the smoothing of tangent at bad point. In this paper, we present a fairing algorithm that both changed point's position and its corresponding tangent vector. The new algorithm possesses the minimum property of energy. We also proved Poliakoff's fairing algorithm is a deduction of our fairing algorithm. Several fairing examples are given in this paper.
Competing structural instabilities in cubic perovskites
Vanderbilt, D
1994-01-01
We study the antiferrodistortive instability and its interaction with ferroelectricity in cubic perovskite compounds. Our first-principles calculations show that coexistence of both instabilities is very common. We develop a first-principles scheme to study the thermodynamics of these compounds when both instabilities are present, and apply it to SrTiO$_3$. We find that increased pressure enhances the antiferrodistortive instability while suppressing the ferroelectric one. Moreover, the presence of one instability tends to suppress the other. A very rich $P$--$T$ phase diagram results.
A numerical study of the transition to oscillatory flow in 3D lid-driven cubic cavity flows
Chiu, Shang-Huan; He, Jiwen; Guo, Aixia; Glowinski, Roland
2016-01-01
In this article, three dimensional (3D) lid-driven cubic cavity flows have been studied numerically for various values of Reynolds number ($Re$). The numerical solution of the Navier-Stokes equations modeling incompressible viscous fluid flow in a cubic cavity is obtained via a methodology combining a first order accurate operator-splitting, $L^2$-projection Stokes solver, a wave-like equation treatment of the advection and finite element methods. The numerical results obtained for Re$=$400, 1000, and 3200 show a good agreement with available numerical and experimental results in literature. Simulation results predict that the critical Re$_{cr}$ for the transition from steady flow to oscillatory (a Hopf bifurcation) is somewhere in [1870, 1875] for the mesh size $h=1/96$. Via studying the flow field distortion of fluid flow at Re before and after Re$_{cr}$, the occurrence of the first pair of Taylor-G\\"ortler-like vortices is connected to the flow field distortion at the transition from steady flow to oscilla...
Modeling the field of laser welding melt pool by RBFNN
Bracic, A Borstnik; Grabec, I
2007-01-01
Efficient control of a laser welding process requires the reliable prediction of process behavior. A statistical method of field modeling, based on normalized RBFNN, can be successfully used to predict the spatiotemporal dynamics of surface optical activity in the laser welding process. In this article we demonstrate how to optimize RBFNN to maximize prediction quality. Special attention is paid to the structure of sample vectors, which represent the bridge between the field distributions in the past and future.
Communication patterns in mean field models for wireless sensor networks
2015-01-01
Wireless sensor networks are usually composed of a large number of nodes, and with the increasing processing power and power consumption efficiency they are expected to run more complex protocols in the future. These pose problems in the field of verification and performance evaluation of wireless networks. In this paper, we tailor the mean-field theory as a modeling technique to analyze their behavior. We apply this method to the slotted ALOHA protocol, and establish results on the long term...
Cubic Derivative Interactions and Asymptotic Dynamics of the Galileon Vacuum
De Arcia, Roberto; León, Genly; Nucamendi, Ulises; Quiros, Israel
2015-01-01
In this paper we apply the tools of the dynamical systems theory in order to uncover the whole asymptotic structure of the vacuum interactions of a galileon model with a cubic derivative interaction term. It is shown that, contrary to what occurs in the presence of background matter, the galileon interactions of vacuum appreciably modify the late-time cosmic dynamics. In particular, a local late-time attractor representing phantom behavior arises which is inevitably associated with a big rip singularity. It seems that the gravitational interactions of the background matter with the galileon screen the effects of the gravitational self-interactions of the galileon, thus erasing any potential modification of the late-time dynamics by the galileon vacuum processes. Unlike other galileon models inspired in the DGP scenario, self-accelerating solutions do not arise in this model.
A stochastic phase-field model determined from molecular dynamics
von Schwerin, Erik
2010-03-17
The dynamics of dendritic growth of a crystal in an undercooled melt is determined by macroscopic diffusion-convection of heat and by capillary forces acting on the nanometer scale of the solid-liquid interface width. Its modelling is useful for instance in processing techniques based on casting. The phase-field method is widely used to study evolution of such microstructural phase transformations on a continuum level; it couples the energy equation to a phenomenological Allen-Cahn/Ginzburg-Landau equation modelling the dynamics of an order parameter determining the solid and liquid phases, including also stochastic fluctuations to obtain the qualitatively correct result of dendritic side branching. This work presents a method to determine stochastic phase-field models from atomistic formulations by coarse-graining molecular dynamics. It has three steps: (1) a precise quantitative atomistic definition of the phase-field variable, based on the local potential energy; (2) derivation of its coarse-grained dynamics model, from microscopic Smoluchowski molecular dynamics (that is Brownian or over damped Langevin dynamics); and (3) numerical computation of the coarse-grained model functions. The coarse-grained model approximates Gibbs ensemble averages of the atomistic phase-field, by choosing coarse-grained drift and diffusion functions that minimize the approximation error of observables in this ensemble average. © EDP Sciences, SMAI, 2010.
A conditional simulation model of intermittent rain fields
Directory of Open Access Journals (Sweden)
L. G. Lanza
2000-01-01
Full Text Available The synthetic generation of random fields with specified probability distribution, correlation structure and probability of no-rain areas is used as the basis for the formulation of a stochastic space-time rainfall model conditional on rain gauge observations. A new procedure for conditioning while preserving intermittence is developed to provide constraints to Monte Carlo realisations of possible rainfall scenarios. The method addresses the properties of the convolution operator involved in generating random field realisations and is actually independent of the numerical algorithm used for unconditional simulation. It requires only the solution of a linear system of algebraic equations the order of which is given by the number of the conditioning nodes. Applications of the methodology are expected in rainfall field reconstruction from sparse rain gauge data and in rainfall downscaling from the large scale information that may be provided by remote sensing devices or numerical weather prediction models. Keywords: Space-time rainfall; Conditioning; Stochastic models
Pedestrian simulations in hexagonal cell local field model
Leng, Biao; Wang, Jianyuan; Xiong, Zhang
2015-11-01
Pedestrian dynamics have caused wide concern over the recent years. This paper presents a local field (LF) model based on regular hexagonal cells to simulate pedestrian dynamics in scenarios such as corridors and bottlenecks. In this model, the simulation scenarios are discretized into regular hexagonal cells. The local field is a small region around pedestrian. Each pedestrian will choose his/her target cell according to the situation in his/her local field. Different walking strategies are considered in the simulation in corridor scenario and the fundamental graphs are used to verify this model. Different shapes of exit are also discussed in the bottleneck scenario. The statistics of push effect show that the smooth bottleneck exit may be more safe.
Continuous Molecular Fields Approach Applied to Structure-Activity Modeling
Baskin, Igor I
2013-01-01
The Method of Continuous Molecular Fields is a universal approach to predict various properties of chemical compounds, in which molecules are represented by means of continuous fields (such as electrostatic, steric, electron density functions, etc). The essence of the proposed approach consists in performing statistical analysis of functional molecular data by means of joint application of kernel machine learning methods and special kernels which compare molecules by computing overlap integrals of their molecular fields. This approach is an alternative to traditional methods of building 3D structure-activity and structure-property models based on the use of fixed sets of molecular descriptors. The methodology of the approach is described in this chapter, followed by its application to building regression 3D-QSAR models and conducting virtual screening based on one-class classification models. The main directions of the further development of this approach are outlined at the end of the chapter.
Higher-Rank Supersymmetric Models and Topological Field Theory
Kawai, T; Yang, S K; Kawai, Toshiya; Uchino, Taku; Yang, Sung-Kil
1993-01-01
In the first part of this paper we investigate the operator aspect of higher-rank supersymmetric model which is introduced as a Lie theoretic extension of the $N=2$ minimal model with the simplest case $su(2)$ corresponding to the $N=2$ minimal model. In particular we identify the analogs of chirality conditions and chiral ring. In the second part we construct a class of topological conformal field theories starting with this higher-rank supersymmetric model. We show the BRST-exactness of the twisted stress-energy tensor, find out physical observables and discuss how to make their correlation functions. It is emphasized that in the case of $su(2)$ the topological field theory constructed in this paper is distinct from the one obtained by twisting the $N=2$ minimal model through the usual procedure.
The Distance Field Model and Distance Constrained MAP Adaptation Algorithm
Institute of Scientific and Technical Information of China (English)
YUPeng; WANGZuoying
2003-01-01
Spatial structure information, i.e., the rel-ative position information of phonetic states in the feature space, is long to be carefully researched yet. In this pa-per, a new model named “Distance Field” is proposed to describe the spatial structure information. Based on this model, a modified MAP adaptation algorithm named dis-tance constrained maximum a poateriori (DCMAP) is in-troduced. The distance field model gives large penalty when the spatial structure is destroyed. As a result the DCMAP reserves the spatial structure information in adaptation process. Experiments show the Distance Field Model improves the performance of MAP adapta-tion. Further results show DCMAP has strong cross-state estimation ability, which is used to train a well-performed speaker-dependent model by data from only part of pho-
Cyclic Evolution of Coronal Fields from a Coupled Dynamo Potential-Field Source-Surface Model.
Dikpati, Mausumi; Suresh, Akshaya; Burkepile, Joan
The structure of the Sun's corona varies with the solar-cycle phase, from a near spherical symmetry at solar maximum to an axial dipole at solar minimum. It is widely accepted that the large-scale coronal structure is governed by magnetic fields that are most likely generated by dynamo action in the solar interior. In order to understand the variation in coronal structure, we couple a potential-field source-surface model with a cyclic dynamo model. In this coupled model, the magnetic field inside the convection zone is governed by the dynamo equation; these dynamo-generated fields are extended from the photosphere to the corona using a potential-field source-surface model. Assuming axisymmetry, we take linear combinations of associated Legendre polynomials that match the more complex coronal structures. Choosing images of the global corona from the Mauna Loa Solar Observatory at each Carrington rotation over half a cycle (1986 - 1991), we compute the coefficients of the associated Legendre polynomials up to degree eight and compare with observations. We show that at minimum the dipole term dominates, but it fades as the cycle progresses; higher-order multipolar terms begin to dominate. The amplitudes of these terms are not exactly the same for the two limbs, indicating that there is a longitude dependence. While both the 1986 and the 1996 minimum coronas were dipolar, the minimum in 2008 was unusual, since there was a substantial departure from a dipole. We investigate the physical cause of this departure by including a North-South asymmetry in the surface source of the magnetic fields in our flux-transport dynamo model, and find that this asymmetry could be one of the reasons for departure from the dipole in the 2008 minimum.
Energy Technology Data Exchange (ETDEWEB)
Cooper, F.
1996-12-31
We review the assumptions and domain of applicability of Landau`s Hydrodynamical Model. By considering two models of particle production, pair production from strong electric fields and particle production in the linear {sigma} model, we demonstrate that many of Landau`s ideas are verified in explicit field theory calculations.
Computational Models for Creating Homogeneous Magnetic Field Generation Systems
Directory of Open Access Journals (Sweden)
Gerlys M. Villalobos-Fontalvo
2013-11-01
Full Text Available It is increasingly common to use magnetic fields at the cellular level to assess their interaction with biological tissues. The stimulation is usually done with Helmholtz coils which generate a uniform magnetic field in the center of the system. However, assessing cellular behavior with different magnetic field characteristics can be a long and expensive process. For this, it can be used computational models to previously estimate the cellular behavior due to variety of field characteristics prior to in-vitro stimulation in a laboratory. In this paper, we present a methodology for the development of three computational models of homogeneous magnetic field generation systems for possible application in cell stimulation. The models were developed in the Ansys Workbench environment and it was evaluated the magnetic flux density behavior at different configurations. The results were validated with theoretical calculations from the Biot-Savart law. Validated models will be coupled to Ansys APDL environment in order to assess the harmonic response of the system.
The Research of the Driver Attention Field Modeling
Directory of Open Access Journals (Sweden)
Pengfei Tao
2014-01-01
Full Text Available For expanding the application scope of car-following, based on the basic idea of the noncontact interaction of the objects in physics, establish an attention field model to describe the driving behavior. Firstly, propose the time distance concept to describe the degree of driver perception to the front one-dimensional space and extend its application range to the two-dimensional space. Secondly, connect the point which has the same time distance to constitute the equipotential line of drivers’ attention field equipotent, and establish a model to describe it. Thirdly, define the effective range of the driver’s psychological field with the feature of the driver’s visual distance range increasing and the angle decreasing. Finally, design the calculation method to collect projection of the object in the psychological field scope and calculate the curve points to determine the object’s intensity of psychological field. Preliminarily build the driving behavior model and use the numerical simulation method to simulate the simple transport scenarios; initially verify the validity of the model.
On hyperbolicity violations in cosmological models with vector fields
Golovnev, Alexey
2014-01-01
Cosmological models with vector fields received much attention in recent years. Unfortunately, most of them are plagued with severe instabilities or other problems. In particular, it was noted by G. Esposito-Farese, C. Pitrou and J.-Ph. Uzan in arXiv:0912.0481 that the models with a non-linear function of the Maxwellian kinetic term do always imply violations of hyperbolicity somewhere in the phase space. In this work we make this statement more precise in several respects and show that those violations may not be present around spatially homogeneous configurations of the vector field.
Modelling of the plasma-MIG welding temperature field
Institute of Scientific and Technical Information of China (English)
Bai Yan; Gao Hongming; Wu Lin; Shi Lei
2006-01-01
A three-dimensional simulation model for the plasma-MIG welding process, which takes the interaction between the plasma arc and MIG arc into account, is presented and the quasi-steady temperature fields on the workpiece are calculated with the model. The 10 mm-5A06 aluminum alloy is welded and the temperature fields are measured with the thermoelectric couple. The simulation results and measured results show that the biggest deviation of peak temperature between them is below 20 ℃ , which indicates good coincidence between the simulation and measurement.
3-D rheologic model of earthquake preparation (Ⅲ): Precursor field
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
On the basis of the theory of viscoelastic displacement and strain field for the three-dimensional rheologic model of earthquake preparation, this paper mainly studies the theoretical solution of precursor field for the three-dimensional rheologic model of earthquake preparation. We derive the viscoelastic analytical expressions of the ground tilt, underground water level, earth resistivity at an arbitrary point (x, y, z) in the rheologic medium, and analyzed the earth resistivity preliminarily, providing a certain theoretical basis for the precursor analysis of seismogenic process.
Spurious Shell Closures in the Relativistic Mean Field Model
Geng, L S; Toki, H; Long, W H; Shen, G
2006-01-01
Following a systematic theoretical study of the ground-state properties of over 7000 nuclei from the proton drip line to the neutron drip line in the relativistic mean field model [Prog. Theor. Phys. 113 (2005) 785], which is in fair agreement with existing experimental data, we observe a few spurious shell closures, i.e. proton shell closures at Z=58 and Z=92. These spurious shell closures are found to persist in all the effective forces of the relativistic mean field model, e.g. TMA, NL3, PKDD and DD-ME2.
Model (1:10) of the Split-Field Magnet
1977-01-01
The photo shows Klaus Brand from the ISR BOM group with the working model of the Split-Field Magnet, while setting up the field measuring bench. The bench used Hall probes for which he had developed the electronics instrumentation (ISR-BOM Int. Note 12-01-1977). The SFM model made of mild steel with copper coils had been measured in the years 1969-1970. This new mapping campaign was related to the installation of a large calorimeter to one side of the magnet.
Luzzati, Vittorio; Tardieu, Annette; Gulik-Krzywicki, Tadeusz
1981-01-01
The observed intensities of the reflections from the body-centered cubic phase of lipid systems are shown to be incompatible with a recently reported model consisting of straight, indefinitely long rods.
Determination of asphaltene onset conditions using the cubic plus association equation of state
DEFF Research Database (Denmark)
Arya, Alay; von Solms, Nicolas; Kontogeorgis, Georgios M.
2015-01-01
The cubic-plus-association (CPA) equation of state (EoS) has already been proven to be a successful model for phase equilibrium calculations for systems containing associating components and has already been applied for asphaltene modeling by few researchers. In the present work, we apply the CPA...
Spatial 't Hooft loop to cubic order in hot QCD
Giovannangeli, P
2002-01-01
Spatial 't Hooft loops of strength k measure the qualitative change in the behaviour of electric colour flux in confined and deconfined phase of SU (N) gauge theory. They show an area law in the deconfined phase, known analytica lly to two loop order with a ``k-scaling'' law k(N-k). In this paper we comput e the O(g^3) correction to the tension. It is due to neutral gluon fields that get their mass through interaction with the wall. The simple k-scaling is lost in cubic order. The generic problem of non-convexity shows up in this order an d the cure is provided. The result for large N is explicitely given. We show tha t nonperturbative effects appear at O(g^5).
Quantum corrections for the cubic Galileon in the covariant language
Saltas, Ippocratis D.; Vitagliano, Vincenzo
2017-05-01
We present for the first time an explicit exposition of quantum corrections within the cubic Galileon theory including the effect of quantum gravity, in a background- and gauge-invariant manner, employing the field-reparametrisation approach of the covariant effective action at 1-loop. We show that the consideration of gravitational effects in combination with the non-linear derivative structure of the theory reveals new interactions at the perturbative level, which manifest themselves as higher-operators in the associated effective action, which' relevance is controlled by appropriate ratios of the cosmological vacuum and the Galileon mass scale. The significance and concept of the covariant approach in this context is discussed, while all calculations are explicitly presented.
Hairy black holes in cubic quasi-topological gravity
Dykaar, Hannah; Hennigar, Robie A.; Mann, Robert B.
2017-05-01
We construct a class of five dimensional black hole solutions to cubic quasi-topological gravity with conformal scalar hair and study their thermodynamics. We find these black holes provide the second example of black hole λ-lines: a line of second order (continuous) phase transitions, akin to the fluid/superfluid transition of 4He. Examples of isolated critical points are found for spherical black holes, marking the first in the literature to date. We also find various novel and interesting phase structures, including an isolated critical point occurring in conjunction with a double reentrant phase transition. The AdS vacua of the theory are studied, finding ghost-free configurations where the scalar field takes on a non-zero constant value, in notable contrast to the five dimensional Lovelock case.
Temperature Field-Wind Velocity Field Optimum Control of Greenhouse Environment Based on CFD Model
Directory of Open Access Journals (Sweden)
Yongbo Li
2014-01-01
Full Text Available The computational fluid dynamics technology is applied as the environmental control model, which can include the greenhouse space. Basic environmental factors are set to be the control objects, the field information is achieved via the division of layers by height, and numerical characteristics of each layer are used to describe the field information. Under the natural ventilation condition, real-time requirements, energy consumption, and distribution difference are selected as index functions. The optimization algorithm of adaptive simulated annealing is used to obtain optimal control outputs. A comparison with full-open ventilation shows that the whole index can be reduced at 44.21% and found that a certain mutual exclusiveness exists between the temperature and velocity field in the optimal course. All the results indicate that the application of CFD model has great advantages to improve the control accuracy of greenhouse.
Polarizable Mean-Field Model of Water for Biological Simulations with Amber and Charmm force fields
Leontyev, Igor
2015-01-01
Although a great number of computational models of water are available today, the majority of current biological simulations are done with simple models, such as TIP3P and SPC, developed almost thirty years ago and only slightly modified since then. The reason is that the non-polarizable force fields that are mostly used to describe proteins and other biological molecules are incompatible with more sophisticated modern polarizable models of water. The issue is electronic polarizability: in liquid state, in protein, and in vacuum the water molecule is polarized differently, and therefore has different properties; thus the only way to describe all these different media with the same model is to use a polarizable water model. However, to be compatible with the force field of the rest of the system, e.g. a protein, the latter should be polarizable as well. Here we describe a novel model of water that is in effect polarizable, and yet compatible with the standard non-polarizable force fields such as AMBER, CHARMM,...
Cubic optical elements for an accommodative intraocular lens.
Simonov, Aleksey N; Vdovin, Gleb; Rombach, Michiel C
2006-08-21
We present a new accommodative intraocular lens based on a two-element varifocal Alvarez lens. The intraocular lens consists of (1) an anterior element combining a spherical lens for refractive power with a cubic surface for the varifocal effect, and (2) a posterior element with a cubic surface only. The focal length of the IOL lens changes when the superimposed refractive elements shift in opposite directions in a plane perpendicular to the optical axis. The ciliary muscle will drive the accommodation by a natural process of contraction and relaxation. Results of ray-tracing simulations of the model eye with the two-element intraocular lens are presented for on-axis and off-axis vision. The configuration of the lens is optimized to reduce refractive errors as well as effects of misalignment. A prototype with a clear aperture of ~5.7 mm is manufactured and evaluated in air with a Shack-Hartmann wave-front sensor. It provides an accommodation range of ~4 dioptres in the eye at a ~0.75-mm lateral displacement of the optical elements. The experimentally measured on-axis optical performance of the IOL lens agrees with the theoretically predicted performance.
Magnetic fields in barred galaxies. V. Modelling NGC 1365
Moss, D; Englmaier, P; Shukurov, A; Beck, R; Sokoloff, D D; 10.1051/0004-6361:20066222
2009-01-01
We present a model of the global magnetic field in the barred galaxy NGC 1365 based jointly on the large-scale velocity field of interstellar gas fitted to HI and CO observations of this galaxy and on mean-field dynamo theory. The aim of the paper is to present a detailed quantitative comparison of a galactic dynamo model with independent radio observations. We consider several gas dynamical and nonlinear dynamo models that include plausible variations of parameters that are poorly known. Models of cosmic ray distribution in the galaxy are introduced to produce synthetic radio polarization maps allowing direct comparison with those observed at 3.5cm and 6.2cm. We show that the dynamo model is robust in that the most important magnetic features are controlled by the relatively well established properties of the density distribution and gas velocity field. The optimal agreement between the synthetic polarization maps and observations is obtained when a uniform cosmic ray distribution is adopted. We find some in...
Continuous global geomagnetic field models for the past 3000 years
Korte, Monika; Constable, Catherine
2003-11-01
Several global geomagnetic field models exist for recent decades, but due to limited data availability models for several centuries to millennia are rare. We present a continuous spherical harmonic model for almost 3 millennia from 1000 b.c. to 1800 a.d., based on a dataset of directional archaeo- and paleomagnetic data and axial dipole constraints. The model, named Continuous Archaeomagnetic and Lake Sediment Geomagnetic Model for the last 3k years (CALS3K.1), can be used to predict both the field and secular variation. Comparisons and tests with synthetic data lead to the conclusion that CALS3K.1 gives a good general, large-scale representation of the geomagnetic field, but lacks small-scale structure due to the limited resolution of the sparse dataset. In future applications the model can be used for comparisons with additional, new data for that time span. For better resolved regions, the agreement of data with CALS3K.1 will provide an idea about the general compatibility of the data with the field and secular variation in that region of the world. For poorly covered regions and time intervals we hope to iteratively improve the model by comparisons with and inclusion of new data. Animations and additional snapshot plots of model predictions as well as the model coefficients and a FORTRAN code to evaluate them for any time can be accessed under http://www.mahi.ucsd.edu/cathy/Holocene/holocene.html. The whole package is also stored in the Earthref digital archive at http://www.earthref.org/...
Generation of infant anatomical models for evaluating electromagnetic field exposures.
Li, Congsheng; Chen, Zhiye; Yang, Lei; Lv, Bin; Liu, Jianzhe; Varsier, Nadège; Hadjem, Abdelhamid; Wiart, Joe; Xie, Yi; Ma, Lin; Wu, Tongning
2015-01-01
Realistic anatomical modeling is essential in analyzing human exposure to electromagnetic fields. Infants have significant physical and anatomical differences compared with other age groups. However, few realistic infant models are available. In this work, we developed one 12-month-old male whole body model and one 17-month-old male head model from magnetic resonance images. The whole body and head models contained 28 and 30 tissues, respectively, at spatial resolution of 1 mm × 1 mm × 1 mm. Fewer identified tissues in the whole body model were a result of the low original image quality induced by the fast imaging sequence. The anatomical and physical parameters of the models were validated against findings in published literature (e.g., a maximum deviation as 18% in tissue mass was observed compared with the data from International Commission on Radiological Protection). Several typical exposure scenarios were realized for numerical simulation. Dosimetric comparison with various adult and child anatomical models was conducted. Significant differences in the physical and anatomical features between adult and child models demonstrated the importance of creating realistic infant models. Current safety guidelines for infant exposure to radiofrequency electromagnetic fields may not be conservative.
Modeling of electric field distribution in tissues during electroporation.
Corovic, Selma; Lackovic, Igor; Sustaric, Primoz; Sustar, Tomaz; Rodic, Tomaz; Miklavcic, Damijan
2013-02-21
Electroporation based therapies and treatments (e.g. electrochemotherapy, gene electrotransfer for gene therapy and DNA vaccination, tissue ablation with irreversible electroporation and transdermal drug delivery) require a precise prediction of the therapy or treatment outcome by a personalized treatment planning procedure. Numerical modeling of local electric field distribution within electroporated tissues has become an important tool in treatment planning procedure in both clinical and experimental settings. Recent studies have reported that the uncertainties in electrical properties (i.e. electric conductivity of the treated tissues and the rate of increase in electric conductivity due to electroporation) predefined in numerical models have large effect on electroporation based therapy and treatment effectiveness. The aim of our study was to investigate whether the increase in electric conductivity of tissues needs to be taken into account when modeling tissue response to the electroporation pulses and how it affects the local electric distribution within electroporated tissues. We built 3D numerical models for single tissue (one type of tissue, e.g. liver) and composite tissue (several types of tissues, e.g. subcutaneous tumor). Our computer simulations were performed by using three different modeling approaches that are based on finite element method: inverse analysis, nonlinear parametric and sequential analysis. We compared linear (i.e. tissue conductivity is constant) model and non-linear (i.e. tissue conductivity is electric field dependent) model. By calculating goodness of fit measure we compared the results of our numerical simulations to the results of in vivo measurements. The results of our study show that the nonlinear models (i.e. tissue conductivity is electric field dependent: σ(E)) fit experimental data better than linear models (i.e. tissue conductivity is constant). This was found for both single tissue and composite tissue. Our results of
Directory of Open Access Journals (Sweden)
Xiaolong Wang
2013-01-01
Full Text Available In general, proper orthogonal decomposition (POD method is used to deal with single-parameter problems in engineering practice, and the linear interpolation is employed to establish the reduced model. Recently, this method is extended to solve the double-parameter problems with the amplitudes being achieved by cubic B-spline interpolation. In this paper, the accuracy of reduced models, which are established with linear interpolation and cubic B-spline interpolation, respectively, is verified via two typical examples. Both results of the two methods are satisfying, and the results of cubic B-spline interpolation are more accurate than those of linear interpolation. The results are meaningful for guiding the application of the POD interpolation to complex multiparameter problems.
Grain coarsening in two-dimensional phase-field models with an orientation field
Korbuly, Bálint; Pusztai, Tamás; Henry, Hervé; Plapp, Mathis; Apel, Markus; Gránásy, László
2017-05-01
In the literature, contradictory results have been published regarding the form of the limiting (long-time) grain size distribution (LGSD) that characterizes the late stage grain coarsening in two-dimensional and quasi-two-dimensional polycrystalline systems. While experiments and the phase-field crystal (PFC) model (a simple dynamical density functional theory) indicate a log-normal distribution, other works including theoretical studies based on conventional phase-field simulations that rely on coarse grained fields, like the multi-phase-field (MPF) and orientation field (OF) models, yield significantly different distributions. In a recent work, we have shown that the coarse grained phase-field models (whether MPF or OF) yield very similar limiting size distributions that seem to differ from the theoretical predictions. Herein, we revisit this problem, and demonstrate in the case of OF models [R. Kobayashi, J. A. Warren, and W. C. Carter, Physica D 140, 141 (2000), 10.1016/S0167-2789(00)00023-3; H. Henry, J. Mellenthin, and M. Plapp, Phys. Rev. B 86, 054117 (2012), 10.1103/PhysRevB.86.054117] that an insufficient resolution of the small angle grain boundaries leads to a log-normal distribution close to those seen in the experiments and the molecular scale PFC simulations. Our paper indicates, furthermore, that the LGSD is critically sensitive to the details of the evaluation process, and raises the possibility that the differences among the LGSD results from different sources may originate from differences in the detection of small angle grain boundaries.
Quantum Field Theory and the Electroweak Standard Model
Boos, E
2015-01-01
The Standard Model is one of the main intellectual achievements for about the last 50 years, a result of many theoretical and experimental studies. In this lecture a brief introduction to the electroweak part of the Standard Model is given. Since the Standard Model is a quantum field theory, some aspects for understanding of quantization of abelian and non-abelian gauge theories are also briefly discussed. It is demonstrated how well the electroweak Standard Model works in describing a large variety of precise experimental measure- ments at lepton and hadron collider.
Plane problems of cubic quasicrystal media with an elliptic hole or a crack
Energy Technology Data Exchange (ETDEWEB)
Gao, Yang, E-mail: gaoyangg@gmail.com [Institute of Mechanics, University of Kassel, Kassel 34125 (Germany); Ricoeur, Andreas [Institute of Mechanics, University of Kassel, Kassel 34125 (Germany); Zhang, Liangliang [College of Science, China Agricultural University, Beijing 100083 (China)
2011-07-11
Based on the complex potential method, plane problems of cubic quasicrystal media containing an elliptic hole subjected to uniform remote loadings are solved. The explicit solutions for the coupled fields are given in the closed form. Degenerating the elliptic hole into a crack, the asymptotic distribution of the phonon and phason stress fields near the crack tip exhibits inverse square root singularities. Explicit expressions for the stress intensity factors, crack opening displacements and strain energy release rate are also presented. -- Highlights: → Lekhnitskii's formalism is extended to cubic QC solids. → The plane problem of an elliptic hole or crack is investigated. → Analytical expressions for both entire and asymptotic fields are determined. → The stress intensity factors are independent of material constants. → The coupled field strongly affects the configuration and strain energy of the crack.
TESTING GALACTIC MAGNETIC FIELD MODELS USING NEAR-INFRARED POLARIMETRY
Energy Technology Data Exchange (ETDEWEB)
Pavel, Michael D.; Clemens, D. P.; Pinnick, A. F., E-mail: pavelmi@bu.edu, E-mail: clemens@bu.edu, E-mail: apinnick@bu.edu [Institute for Astrophysical Research Boston University, 725 Commonwealth Ave, Boston, MA 02215 (United States)
2012-04-10
This work combines new observations of NIR starlight linear polarimetry with previously simulated observations in order to constrain dynamo models of the Galactic magnetic field. Polarimetric observations were obtained with the Mimir instrument on the Perkins Telescope in Flagstaff, AZ, along a line of constant Galactic longitude (l = 150 Degree-Sign ) with 17 pointings of the 10' Multiplication-Sign 10' field of view between -75 Degree-Sign < b < 10 Degree-Sign , with more frequent pointings toward the Galactic midplane. A total of 10,962 stars were photometrically measured and 1116 had usable polarizations. The observed distribution of polarization position angles with Galactic latitude and the cumulative distribution function of the measured polarizations are compared to predicted values. While the predictions lack the effects of turbulence and are therefore idealized, this comparison allows significant rejection of A0-type magnetic field models. S0 and disk-even halo-odd magnetic field geometries are also rejected by the observations, but at lower significance. New predictions of spiral-type, axisymmetric magnetic fields, when combined with these new NIR observations, constrain the Galactic magnetic field spiral pitch angle to -6 Degree-Sign {+-} 2 Degree-Sign .
A Solvatochromic Model Calibrates Nitriles’ Vibrational Frequencies to Electrostatic Fields
Bagchi, Sayan; Fried, Stephen D.; Boxer, Steven G.
2012-01-01
Electrostatic interactions provide a primary connection between a protein’s three-dimensional structure and its function. Infrared (IR) probes are useful because vibrational frequencies of certain chemical groups, such as nitriles, are linearly sensitive to local electrostatic field, and can serve as a molecular electric field meter. IR spectroscopy has been used to study electrostatic changes or fluctuations in proteins, but measured peak frequencies have not been previously mapped to total electric fields, because of the absence of a field-frequency calibration and the complication of local chemical effects such as H-bonds. We report a solvatochromic model that provides a means to assess the H-bonding status of aromatic nitrile vibrational probes, and calibrates their vibrational frequencies to electrostatic field. The analysis involves correlations between the nitrile’s IR frequency and its 13C chemical shift, whose observation is facilitated by a robust method for introducing isotopes into aromatic nitriles. The method is tested on the model protein Ribonuclease S (RNase S) containing a labeled p-CN-Phe near the active site. Comparison of the measurements in RNase S against solvatochromic data gives an estimate of the average total electrostatic field at this location. The value determined agrees quantitatively with MD simulations, suggesting broader potential for the use of IR probes in the study of protein electrostatics. PMID:22694663
A solvatochromic model calibrates nitriles' vibrational frequencies to electrostatic fields.
Bagchi, Sayan; Fried, Stephen D; Boxer, Steven G
2012-06-27
Electrostatic interactions provide a primary connection between a protein's three-dimensional structure and its function. Infrared probes are useful because vibrational frequencies of certain chemical groups, such as nitriles, are linearly sensitive to local electrostatic field and can serve as a molecular electric field meter. IR spectroscopy has been used to study electrostatic changes or fluctuations in proteins, but measured peak frequencies have not been previously mapped to total electric fields, because of the absence of a field-frequency calibration and the complication of local chemical effects such as H-bonds. We report a solvatochromic model that provides a means to assess the H-bonding status of aromatic nitrile vibrational probes and calibrates their vibrational frequencies to electrostatic field. The analysis involves correlations between the nitrile's IR frequency and its (13)C chemical shift, whose observation is facilitated by a robust method for introducing isotopes into aromatic nitriles. The method is tested on the model protein ribonuclease S (RNase S) containing a labeled p-CN-Phe near the active site. Comparison of the measurements in RNase S against solvatochromic data gives an estimate of the average total electrostatic field at this location. The value determined agrees quantitatively with molecular dynamics simulations, suggesting broader potential for the use of IR probes in the study of protein electrostatics.
Electric quadrupole interaction in cubic BCC α-Fe
Energy Technology Data Exchange (ETDEWEB)
Błachowski, A.; Komędera, K. [Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, ul. Podchorążych 2, PL-30-084 Kraków (Poland); Ruebenbauer, K., E-mail: sfrueben@cyf-kr.edu.pl [Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, ul. Podchorążych 2, PL-30-084 Kraków (Poland); Cios, G.; Żukrowski, J. [AGH University of Science and Technology, Academic Center for Materials and Nanotechnology, Av. A. Mickiewicza 30, PL-30-059 Kraków (Poland); Górnicki, R. [RENON, ul. Gliniana 15/15, PL-30-732 Kraków (Poland)
2016-07-15
Mössbauer transmission spectra for the 14.41-keV resonant line in {sup 57}Fe have been collected at room temperature by using {sup 57}Co(Rh) commercial source and α-Fe strain-free single crystal as an absorber. The absorber was magnetized to saturation in the absorber plane perpendicular to the γ-ray beam axis applying small external magnetic field. Spectra were collected for various orientations of the magnetizing field, the latter lying close to the [110] crystal plane. A positive electric quadrupole coupling constant was found practically independent on the field orientation. One obtains the following value V{sub zz} = +1.61(4) × 10{sup 19} Vm{sup −2} for the (average) principal component of the electric field gradient (EFG) tensor under assumption that the EFG tensor is axially symmetric and the principal axis is aligned with the magnetic hyperfine field acting on the {sup 57}Fe nucleus. The nuclear spectroscopic electric quadrupole moment for the first excited state of the {sup 57}Fe nucleus was adopted as +0.17 b. Similar measurement was performed at room temperature using as-rolled polycrystalline α-Fe foil of high purity in the zero external field. Corresponding value for the principal component of the EFG was found as V{sub zz} = +1.92(4) × 10{sup 19} Vm{sup −2}. Hence, it seems that the origin of the EFG is primarily due to the local (atomic) electronic wave function distortion caused by the spin–orbit interaction between effective electronic spin S and incompletely quenched electronic angular momentum L. It seems as well that the lowest order term proportional to the product L·λ·S dominates, as no direction dependence of the EFG principal component is seen. The lowest order term is isotropic for a cubic symmetry as one has λ=λ 1 for cubic systems with the symbol 1 denoting unit operator and λ being the coupling parameter. - Highlights: • Precision of MS the same as MAPON • Real scans versus magnetization direction • A challenge
Constraining Galactic Magnetic Field Models with Starlight Polarimetry
Pavel, Michael D
2011-01-01
This paper provides testable predictions about starlight polarizations to constrain the geometry of the Galactic magnetic field, in particular the nature of the poloidal component. Galactic dynamo simulations and Galactic dust distributions from the literature are combined with a Stokes radiative transfer model to predict the observed polarizations and position angles of near-infrared starlight, assuming the light is polarized by aligned anisotropic dust grains. S0 and A0 magnetic field models and the role of magnetic pitch angle are all examined. All-sky predictions are made, and particular directions are identified as providing diagnostic power for discriminating among the models. Cumulative distribution functions of the normalized degree of polarization and plots of polarization position angle vs. Galactic latitude are proposed as tools for testing models against observations.
On the Predictiveness of Single-Field Inflationary Models
Burgess, C.P.; Trott, Michael
2014-01-01
We re-examine the predictiveness of single-field inflationary models and discuss how an unknown UV completion can complicate determining inflationary model parameters from observations, even from precision measurements. Besides the usual naturalness issues associated with having a shallow inflationary potential, we describe another issue for inflation, namely, unknown UV physics modifies the running of Standard Model (SM) parameters and thereby introduces uncertainty into the potential inflationary predictions. We illustrate this point using the minimal Higgs Inflationary scenario, which is arguably the most predictive single-field model on the market, because its predictions for $A_s$, $r$ and $n_s$ are made using only one new free parameter beyond those measured in particle physics experiments, and run up to the inflationary regime. We find that this issue can already have observable effects. At the same time, this UV-parameter dependence in the Renormalization Group allows Higgs Inflation to occur (in prin...
Semiclassical two-step model for strong-field ionization
Shvetsov-Shilovski, N I; Madsen, L B; Räsänen, E; Lemell, C; Burgdörfer, J; Arbó, D G; Tőkési, K
2016-01-01
We present a semiclassical two-step model for strong-field ionization that accounts for path interferences of tunnel-ionized electrons in the ionic potential beyond perturbation theory. Within the framework of a classical trajectory Monte-Carlo representation of the phase-space dynamics, the model employs the semiclassical approximation to the phase of the full quantum propagator in the exit channel. By comparison with the exact numerical solution of the time-dependent Schr\\"odinger equation for strong-field ionization of hydrogen, we show that for suitable choices of the momentum distribution after the first tunneling step, the model yields good quantitative agreement with the full quantum simulation. The two-dimensional photoelectron momentum distributions, the energy spectra, and the angular distributions are found to be in good agreement with the corresponding quantum results. Specifically, the model quantitatively reproduces the fan-like interference patterns in the low-energy part of the two-dimensional...
Snowflake growth in three dimensions using phase field modelling
Demange, G; Patte, R; Brunel, M
2016-01-01
Snowflake growth provides us with a fascinating example of spontaneous pattern formation in nature. Attempts to understand this phenomenon have led to important insights in non-equilibrium dynamics observed in various active scientific fields, ranging from pattern formation in physical and chemical systems, to self-assembly problems in biology. Yet, very few models currently succeed in reproducing the diversity of snowflake forms in three dimensions, and the link between model parameters and thermodynamic quantities is not established. Here, we report a modified phase field model that describes the subtlety of the ice vapour phase transition, through anisotropic water molecules attachment and condensation, surface diffusion, and strong anisotropic surface tension, that guarantee the anisotropy, faceting and dendritic growth of snowflakes. We demonstrate that this model reproduces the growth dynamics of the most challenging morphologies of snowflakes from the Nakaya diagram. We find that the growth dynamics of...
Modelling the core magnetic field of the earth
Harrison, C. G. A.; Carle, H. M.
1982-01-01
It is suggested that radial off-center dipoles located within the core of the earth be used instead of spherical harmonics of the magnetic potential in modeling the core magnetic field. The off-center dipoles, in addition to more realistically modeling the physical current systems within the core, are if located deep within the core more effective at removing long wavelength signals of either potential or field. Their disadvantage is that their positions and strengths are more difficult to compute, and such effects as upward and downward continuation are more difficult to manipulate. It is nevertheless agreed with Cox (1975) and Alldredge and Hurwitz (1964) that physical realism in models is more important than mathematical convenience. A radial dipole model is presented which agrees with observations of secular variation and excursions.
Numerical Modeling of Electromagnetic Field Effects on the Human Body
Directory of Open Access Journals (Sweden)
Zuzana Psenakova
2006-01-01
Full Text Available Interactions of electromagnetic field (EMF with environment and with tissue of human beings are still under discussion and many research teams are investigating it. The human simulation models are used for biomedical research in a lot of areas, where it is advantage to replace real human body (tissue by the numerical model. Biological effects of EMF are one of the areas, where numerical models are used with many advantages. On the other side, this research is very specific and it is always quite hard to simulate realistic human tissue. This paper deals with different possibilities of numerical modelling of electromagnetic field effects on the human body (especially calculation of the specific absorption rate (SAR distribution in human body and thermal effect.
Local Cubic Law Simulation of Stress-dependent Aperture-based Permeability
Huo, D.; Benson, S. M.
2014-12-01
Research on calculating fracture permeability has been undergoing for decades (Witherspoon, 1980). Local Cubic Law (LCL) has been proposed to be one feasible way to simulate the fracture permeability with variable aperture changes (Brown, 1987). The purpose of this research is to present an evaluation of LCL based on a set of experimental results of permeability, aperture distribution and effective stress. We concurrently measure fracture permeability and fracture aperture distribution changes (using X-Ray CT) with cycling stress. Fractured Berea sandstone and Zenifim sandstone are measured, representing rough and smooth rock fracture surfaces. Using thin section data, we evaluate the grain size and apply Stokes fluid flow simulation in a synthetic field to estimate the stagnant fluid level between rock grains. By accounting for the stagnant fluid level, LCL simulation provides a reliable prediction for fracture permeability. Comparing with previous research (Konzuk and Kueper, 2004), we propose that LCL simulation requires detailed information about local grain arrangement. The experiment shows that permeability change is greater than expected from mean aperture change at different stress levels. LCL simulation demonstrates that this is mainly due to the change of fluid flow pattern with stress, which is caused by aperture distribution change. LCL simulation also exhibits that channeling behavior plays an important role in fluid flow in fractures, and sometimes a small number of channels dominate the flow. In the experiment, we apply different flow rates to assess the LCL simulation at different Reynolds number. The simulation results show that fluid flow rate (1.24 < Re < 15.28) does not have a large impact on LCL predictability in the highly tortuous and rough rock fractures, which agrees with the results of Konzuk and Kueper (2004). References: Brown, S. R., 1987, Fluid flow through rock joints: The effect of surface roughness, J. Geophys. Res., 92(B2), 1337
Belenkaya, Elena S.; Kalegaev, Vladimir V.; Cowley, Stanley W. H.; Provan, Gabrielle; Blokhina, Marina S.; Barinov, Oleg G.; Kirillov, Alexander A.; Grigoryan, Maria S.
2016-07-01
The paraboloid model of Saturn's magnetosphere describes the magnetic field as being due to the sum of contributions from the internal field of the planet, the ring current, and the tail current, all contained by surface currents inside a magnetopause boundary which is taken to be a paraboloid of revolution about the planet-Sun line. The parameters of the model have previously been determined by comparison with data from a few passes through Saturn's magnetosphere in compressed and expanded states, depending on the prevailing dynamic pressure of the solar wind. Here we significantly expand such comparisons through examination of Cassini magnetic field data from 18 near-equatorial passes that span wide ranges of local time, focusing on modelling the co-latitudinal field component that defines the magnetic flux passing through the equatorial plane. For 12 of these passes, spanning pre-dawn, via noon, to post-midnight, the spacecraft crossed the magnetopause during the pass, thus allowing an estimate of the concurrent subsolar radial distance of the magnetopause R1 to be made, considered to be the primary parameter defining the scale size of the system. The best-fit model parameters from these passes are then employed to determine how the parameters vary with R1, using least-squares linear fits, thus providing predictive model parameters for any value of R1 within the range. We show that the fits obtained using the linear approximation parameters are of the same order as those for the individually selected parameters. We also show that the magnetic flux mapping to the tail lobes in these models is generally in good accord with observations of the location of the open-closed field line boundary in Saturn's ionosphere, and the related position of the auroral oval. We then investigate the field data on six passes through the nightside magnetosphere, for which the spacecraft did not cross the magnetopause, such that in this case we compare the observations with three