Stock price forecasting for companies listed on Tehran stock exchange using multivariate adaptive regression splines model and semi-parametric splines technique

Science.gov (United States)

Rounaghi, Mohammad Mahdi; Abbaszadeh, Mohammad Reza; Arashi, Mohammad

2015-11-01

One of the most important topics of interest to investors is stock price changes. Investors whose goals are long term are sensitive to stock price and its changes and react to them. In this regard, we used multivariate adaptive regression splines (MARS) model and semi-parametric splines technique for predicting stock price in this study. The MARS model as a nonparametric method is an adaptive method for regression and it fits for problems with high dimensions and several variables. semi-parametric splines technique was used in this study. Smoothing splines is a nonparametric regression method. In this study, we used 40 variables (30 accounting variables and 10 economic variables) for predicting stock price using the MARS model and using semi-parametric splines technique. After investigating the models, we select 4 accounting variables (book value per share, predicted earnings per share, P/E ratio and risk) as influencing variables on predicting stock price using the MARS model. After fitting the semi-parametric splines technique, only 4 accounting variables (dividends, net EPS, EPS Forecast and P/E Ratio) were selected as variables effective in forecasting stock prices.

PEMODELAN JUMLAH ANAK PUTUS SEKOLAH DI PROVINSI BALI DENGAN PENDEKATAN SEMI-PARAMETRIC GEOGRAPHICALLY WEIGHTED POISSON REGRESSION

Directory of Open Access Journals (Sweden)

GUSTI AYU RATIH ASTARI

2013-11-01

Full Text Available Dropout number is one of the important indicators to measure the human progress resources in education sector. This research uses the approaches of Semi-parametric Geographically Weighted Poisson Regression to get the best model and to determine the influencing factors of dropout number for primary education in Bali. The analysis results show that there are no significant differences between the Poisson regression model with GWPR and Semi-parametric GWPR. Factors which significantly influence the dropout number for primary education in Bali are the ratio of students to school, ratio of students to teachers, the number of families with the latest educational fathers is elementary or junior high school, illiteracy rates, and the average number of family members.

Sparse adaptive Taylor approximation algorithms for parametric and stochastic elliptic PDEs

KAUST Repository

Chkifa, Abdellah

2012-11-29

The numerical approximation of parametric partial differential equations is a computational challenge, in particular when the number of involved parameter is large. This paper considers a model class of second order, linear, parametric, elliptic PDEs on a bounded domain D with diffusion coefficients depending on the parameters in an affine manner. For such models, it was shown in [9, 10] that under very weak assumptions on the diffusion coefficients, the entire family of solutions to such equations can be simultaneously approximated in the Hilbert space V = H0 1(D) by multivariate sparse polynomials in the parameter vector y with a controlled number N of terms. The convergence rate in terms of N does not depend on the number of parameters in V, which may be arbitrarily large or countably infinite, thereby breaking the curse of dimensionality. However, these approximation results do not describe the concrete construction of these polynomial expansions, and should therefore rather be viewed as benchmark for the convergence analysis of numerical methods. The present paper presents an adaptive numerical algorithm for constructing a sequence of sparse polynomials that is proved to converge toward the solution with the optimal benchmark rate. Numerical experiments are presented in large parameter dimension, which confirm the effectiveness of the adaptive approach. © 2012 EDP Sciences, SMAI.

A semi-analytical study of positive corona discharge in wire–plane electrode configuration

International Nuclear Information System (INIS)

Yanallah, K; Pontiga, F; Chen, J H

2013-01-01

Wire-to-plane positive corona discharge in air has been studied using an analytical model of two species (electrons and positive ions). The spatial distributions of electric field and charged species are obtained by integrating Gauss's law and the continuity equations of species along the Laplacian field lines. The experimental values of corona current intensity and applied voltage, together with Warburg's law, have been used to formulate the boundary condition for the electron density on the corona wire. To test the accuracy of the model, the approximate electric field distribution has been compared with the exact numerical solution obtained from a finite element analysis. A parametrical study of wire-to-plane corona discharge has then been undertaken using the approximate semi-analytical solutions. Thus, the spatial distributions of electric field and charged particles have been computed for different values of the gas pressure, wire radius and electrode separation. Also, the two dimensional distribution of ozone density has been obtained using a simplified plasma chemistry model. The approximate semi-analytical solutions can be evaluated in a negligible computational time, yet provide precise estimates of corona discharge variables. (paper)

A semi-analytical study of positive corona discharge in wire-plane electrode configuration

Science.gov (United States)

Yanallah, K.; Pontiga, F.; Chen, J. H.

2013-08-01

Wire-to-plane positive corona discharge in air has been studied using an analytical model of two species (electrons and positive ions). The spatial distributions of electric field and charged species are obtained by integrating Gauss's law and the continuity equations of species along the Laplacian field lines. The experimental values of corona current intensity and applied voltage, together with Warburg's law, have been used to formulate the boundary condition for the electron density on the corona wire. To test the accuracy of the model, the approximate electric field distribution has been compared with the exact numerical solution obtained from a finite element analysis. A parametrical study of wire-to-plane corona discharge has then been undertaken using the approximate semi-analytical solutions. Thus, the spatial distributions of electric field and charged particles have been computed for different values of the gas pressure, wire radius and electrode separation. Also, the two dimensional distribution of ozone density has been obtained using a simplified plasma chemistry model. The approximate semi-analytical solutions can be evaluated in a negligible computational time, yet provide precise estimates of corona discharge variables.

Semi-parametric modelling of investments in heating installations: The case of the Dutch glasshouse industry

NARCIS (Netherlands)

Oude Lansink, A.G.J.M.; Pietola, K.

2005-01-01

This paper applies a semi-parametric approach to estimating a generalised model of investments in heating installations. The results suggest that marginal costs of investments in heating installations increase quickly at small investment levels, whereas the increase slows down at higher investment

The triangular density to approximate the normal density: decision rules-of-thumb

International Nuclear Information System (INIS)

Scherer, William T.; Pomroy, Thomas A.; Fuller, Douglas N.

2003-01-01

In this paper we explore the approximation of the normal density function with the triangular density function, a density function that has extensive use in risk analysis. Such an approximation generates a simple piecewise-linear density function and a piecewise-quadratic distribution function that can be easily manipulated mathematically and that produces surprisingly accurate performance under many instances. This mathematical tractability proves useful when it enables closed-form solutions not otherwise possible, as with problems involving the embedded use of the normal density. For benchmarking purposes we compare the basic triangular approximation with two flared triangular distributions and with two simple uniform approximations; however, throughout the paper our focus is on using the triangular density to approximate the normal for reasons of parsimony. We also investigate the logical extensions of using a non-symmetric triangular density to approximate a lognormal density. Several issues associated with using a triangular density as a substitute for the normal and lognormal densities are discussed, and we explore the resulting numerical approximation errors for the normal case. Finally, we present several examples that highlight simple decision rules-of-thumb that the use of the approximation generates. Such rules-of-thumb, which are useful in risk and reliability analysis and general business analysis, can be difficult or impossible to extract without the use of approximations. These examples include uses of the approximation in generating random deviates, uses in mixture models for risk analysis, and an illustrative decision analysis problem. It is our belief that this exploratory look at the triangular approximation to the normal will provoke other practitioners to explore its possible use in various domains and applications

Local density approximations for relativistic exchange energies

International Nuclear Information System (INIS)

MacDonald, A.H.

1986-01-01

The use of local density approximations to approximate exchange interactions in relativistic electron systems is reviewed. Particular attention is paid to the physical content of these exchange energies by discussing results for the uniform relativistic electron gas from a new point of view. Work on applying these local density approximations in atoms and solids is reviewed and it is concluded that good accuracy is usually possible provided self-interaction corrections are applied. The local density approximations necessary for spin-polarized relativistic systems are discussed and some new results are presented

Bayesian spatial semi-parametric modeling of HIV variation in Kenya.

Directory of Open Access Journals (Sweden)

Oscar Ngesa

Full Text Available Spatial statistics has seen rapid application in many fields, especially epidemiology and public health. Many studies, nonetheless, make limited use of the geographical location information and also usually assume that the covariates, which are related to the response variable, have linear effects. We develop a Bayesian semi-parametric regression model for HIV prevalence data. Model estimation and inference is based on fully Bayesian approach via Markov Chain Monte Carlo (McMC. The model is applied to HIV prevalence data among men in Kenya, derived from the Kenya AIDS indicator survey, with n = 3,662. Past studies have concluded that HIV infection has a nonlinear association with age. In this study a smooth function based on penalized regression splines is used to estimate this nonlinear effect. Other covariates were assumed to have a linear effect. Spatial references to the counties were modeled as both structured and unstructured spatial effects. We observe that circumcision reduces the risk of HIV infection. The results also indicate that men in the urban areas were more likely to be infected by HIV as compared to their rural counterpart. Men with higher education had the lowest risk of HIV infection. A nonlinear relationship between HIV infection and age was established. Risk of HIV infection increases with age up to the age of 40 then declines with increase in age. Men who had STI in the last 12 months were more likely to be infected with HIV. Also men who had ever used a condom were found to have higher likelihood to be infected by HIV. A significant spatial variation of HIV infection in Kenya was also established. The study shows the practicality and flexibility of Bayesian semi-parametric regression model in analyzing epidemiological data.

Parametrized post-Newtonian approximation and Rastall's gravitational field equations

International Nuclear Information System (INIS)

Smalley, L.L.

1978-01-01

The parametrized post-Newtonian (PPN) approximation is generalized to accomodate Rastall's modification of Einstein's theory of gravity, which allows nonzero divergence of the energy-momentum tensor. Rastall's theory is then shown to have consistent field equations, gauge conditions, and the correct Newtonian limit of the equations of motion. The PPN parameters are obtained and shown to agree experimentally with those for the Einstein theory. In light of the nonzero divergence condition, integral conservation laws are investigated and shown to yield conserved energy-momentum and angular-momentum. We conclude that the above generalization of metric theories, within the PPN framework, is a natural extension of the concept of metric theories

Relativistic mean field theory with density dependent coupling constants for nuclear matter and finite nuclei with large charge asymmetry

Energy Technology Data Exchange (ETDEWEB)

Typel, S; Wolter, H H [Sektion Physik, Univ. Muenchen, Garching (Germany)

1998-06-01

Nuclear matter and ground state properties for (proton and neutron) semi-closed shell nuclei are described in relativistic mean field theory with coupling constants which depend on the vector density. The parametrization of the density dependence for {sigma}-, {omega}- and {rho}-mesons is obtained by fitting to properties of nuclear matter and some finite nuclei. The equation of state for symmetric and asymmetric nuclear matter is discussed. Finite nuclei are described in Hartree approximation, including a charge and an improved center-of-mass correction. Pairing is considered in the BCS approximation. Special attention is directed to the predictions for properties at the neutron and proton driplines, e.g. for separation energies, spin-orbit splittings and density distributions. (orig.)

Forecasting Exchange Rate Density Using Parametric Models: the Case of Brazil

Directory of Open Access Journals (Sweden)

Benjamin Miranda Tabak

2007-06-01

Full Text Available This paper employs a recently developed parametric technique to obtain density forecasts for the Brazilian exchange rate, using the exchange rate options market. Empirical results suggest that the option market contains useful information about future exchange rate density. These results suggests that density forecasts using options markets may add value for portfolio and risk management, and may be useful for financial regulators to assess financial stability.

Density Fluctuations in the Solar Wind Driven by Alfvén Wave Parametric Decay

Science.gov (United States)

Bowen, Trevor A.; Badman, Samuel; Hellinger, Petr; Bale, Stuart D.

2018-02-01

Measurements and simulations of inertial compressive turbulence in the solar wind are characterized by anti-correlated magnetic fluctuations parallel to the mean field and density structures. This signature has been interpreted as observational evidence for non-propagating pressure balanced structures, kinetic ion-acoustic waves, as well as the MHD slow-mode. Given the high damping rates of parallel propagating compressive fluctuations, their ubiquity in satellite observations is surprising and suggestive of a local driving process. One possible candidate for the generation of compressive fluctuations in the solar wind is the Alfvén wave parametric instability. Here, we test the parametric decay process as a source of compressive waves in the solar wind by comparing the collisionless damping rates of compressive fluctuations with growth rates of the parametric decay instability daughter waves. Our results suggest that generation of compressive waves through parametric decay is overdamped at 1 au, but that the presence of slow-mode-like density fluctuations is correlated with the parametric decay of Alfvén waves.

Full and semi-analytic analyses of two-pump parametric amplification with pump depletion

DEFF Research Database (Denmark)

Steffensen, Henrik; Ott, Johan Raunkjær; Rottwitt, Karsten

2011-01-01

This paper solves the four coupled equations describing non-degenerate four-wave mixing, with the focus on amplifying a signal in a fiber optical parametric amplifier (FOPA). Based on the full analytic solution, a simple approximate solution describing the gain is developed. The advantage...... of this new approximation is that it includes the depletion of the pumps, which is lacking in the usual quasi-linearized approximation. With the proposed model it is thus simple to predict the gain of a FOPA, which we demonstrate with a highly nonlinear fiber to show that an undepleted FOPA can produce a flat...

Tight-binding approximations to time-dependent density functional theory — A fast approach for the calculation of electronically excited states

Energy Technology Data Exchange (ETDEWEB)

Rüger, Robert, E-mail: rueger@scm.com [Scientific Computing & Modelling NV, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands); Department of Theoretical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands); Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Linnéstr. 2, 04103 Leipzig (Germany); Lenthe, Erik van [Scientific Computing & Modelling NV, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands); Heine, Thomas [Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Linnéstr. 2, 04103 Leipzig (Germany); Visscher, Lucas [Department of Theoretical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands)

2016-05-14

We propose a new method of calculating electronically excited states that combines a density functional theory based ground state calculation with a linear response treatment that employs approximations used in the time-dependent density functional based tight binding (TD-DFTB) approach. The new method termed time-dependent density functional theory TD-DFT+TB does not rely on the DFTB parametrization and is therefore applicable to systems involving all combinations of elements. We show that the new method yields UV/Vis absorption spectra that are in excellent agreement with computationally much more expensive TD-DFT calculations. Errors in vertical excitation energies are reduced by a factor of two compared to TD-DFTB.

Kernel bandwidth estimation for non-parametric density estimation: a comparative study

CSIR Research Space (South Africa)

Van der Walt, CM

2013-12-01

Full Text Available We investigate the performance of conventional bandwidth estimators for non-parametric kernel density estimation on a number of representative pattern-recognition tasks, to gain a better understanding of the behaviour of these estimators in high...

Approximate spin projected spin-unrestricted density functional theory method: Application to diradical character dependences of second hyperpolarizabilities

Energy Technology Data Exchange (ETDEWEB)

Nakano, Masayoshi, E-mail: mnaka@cheng.es.osaka-u.ac.jp; Minami, Takuya, E-mail: mnaka@cheng.es.osaka-u.ac.jp; Fukui, Hitoshi, E-mail: mnaka@cheng.es.osaka-u.ac.jp; Yoneda, Kyohei, E-mail: mnaka@cheng.es.osaka-u.ac.jp; Shigeta, Yasuteru, E-mail: mnaka@cheng.es.osaka-u.ac.jp; Kishi, Ryohei, E-mail: mnaka@cheng.es.osaka-u.ac.jp [Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Champagne, Benoît; Botek, Edith [Laboratoire de Chimie Théorique, Facultés Universitaires Notre-Dame de la Paix (FUNDP), rue de Bruxelles, 61, 5000 Namur (Belgium)

2015-01-22

We develop a novel method for the calculation and the analysis of the one-electron reduced densities in open-shell molecular systems using the natural orbitals and approximate spin projected occupation numbers obtained from broken symmetry (BS), i.e., spin-unrestricted (U), density functional theory (DFT) calculations. The performance of this approximate spin projection (ASP) scheme is examined for the diradical character dependence of the second hyperpolarizability (γ) using several exchange-correlation functionals, i.e., hybrid and long-range corrected UDFT schemes. It is found that the ASP-LC-UBLYP method with a range separating parameter μ = 0.47 reproduces semi-quantitatively the strongly-correlated [UCCSD(T)] result for p-quinodimethane, i.e., the γ variation as a function of the diradical character.

Sparse-grid, reduced-basis Bayesian inversion: Nonaffine-parametric nonlinear equations

Energy Technology Data Exchange (ETDEWEB)

Chen, Peng, E-mail: peng@ices.utexas.edu [The Institute for Computational Engineering and Sciences, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX 78712-1229 (United States); Schwab, Christoph, E-mail: christoph.schwab@sam.math.ethz.ch [Seminar für Angewandte Mathematik, Eidgenössische Technische Hochschule, Römistrasse 101, CH-8092 Zürich (Switzerland)

2016-07-01

We extend the reduced basis (RB) accelerated Bayesian inversion methods for affine-parametric, linear operator equations which are considered in [16,17] to non-affine, nonlinear parametric operator equations. We generalize the analysis of sparsity of parametric forward solution maps in [20] and of Bayesian inversion in [48,49] to the fully discrete setting, including Petrov–Galerkin high-fidelity (“HiFi”) discretization of the forward maps. We develop adaptive, stochastic collocation based reduction methods for the efficient computation of reduced bases on the parametric solution manifold. The nonaffinity and nonlinearity with respect to (w.r.t.) the distributed, uncertain parameters and the unknown solution is collocated; specifically, by the so-called Empirical Interpolation Method (EIM). For the corresponding Bayesian inversion problems, computational efficiency is enhanced in two ways: first, expectations w.r.t. the posterior are computed by adaptive quadratures with dimension-independent convergence rates proposed in [49]; the present work generalizes [49] to account for the impact of the PG discretization in the forward maps on the convergence rates of the Quantities of Interest (QoI for short). Second, we propose to perform the Bayesian estimation only w.r.t. a parsimonious, RB approximation of the posterior density. Based on the approximation results in [49], the infinite-dimensional parametric, deterministic forward map and operator admit N-term RB and EIM approximations which converge at rates which depend only on the sparsity of the parametric forward map. In several numerical experiments, the proposed algorithms exhibit dimension-independent convergence rates which equal, at least, the currently known rate estimates for N-term approximation. We propose to accelerate Bayesian estimation by first offline construction of reduced basis surrogates of the Bayesian posterior density. The parsimonious surrogates can then be employed for online data

Accuracy of the Hartree-Fock and local density approximations for electron densities: a study for light atoms

International Nuclear Information System (INIS)

Almbladh, C.-O.; Ekenberg, U.; Pedroza, A.C.

1983-01-01

The authors compare the electron densities and Hartree potentials in the local density and the Hartree-Fock approximations to the corresponding quantities obtained from more accurate correlated wavefunctions. The comparison is made for a number of two-electron atoms, Li, and for Be. The Hartree-Fock approximation is more accurate than the local density approximation within the 1s shell and for the spin polarization in Li, while the local density approximation is slightly better than the Hartree-Fock approximation for charge densities in the 2s shell. The inaccuracy of the Hartree-Fock and local density approximations to the Hartree potential is substantially smaller than the inaccuracy of the local density approximation to the ground-state exchange-correlation potential. (Auth.)

Ultra-fast computation of electronic spectra for large systems by tight-binding based simplified Tamm-Dancoff approximation (sTDA-xTB)

International Nuclear Information System (INIS)

Grimme, Stefan; Bannwarth, Christoph

2016-01-01

The computational bottleneck of the extremely fast simplified Tamm-Dancoff approximated (sTDA) time-dependent density functional theory procedure [S. Grimme, J. Chem. Phys. 138, 244104 (2013)] for the computation of electronic spectra for large systems is the determination of the ground state Kohn-Sham orbitals and eigenvalues. This limits such treatments to single structures with a few hundred atoms and hence, e.g., sampling along molecular dynamics trajectories for flexible systems or the calculation of chromophore aggregates is often not possible. The aim of this work is to solve this problem by a specifically designed semi-empirical tight binding (TB) procedure similar to the well established self-consistent-charge density functional TB scheme. The new special purpose method provides orbitals and orbital energies of hybrid density functional character for a subsequent and basically unmodified sTDA procedure. Compared to many previous semi-empirical excited state methods, an advantage of the ansatz is that a general eigenvalue problem in a non-orthogonal, extended atomic orbital basis is solved and therefore correct occupied/virtual orbital energy splittings as well as Rydberg levels are obtained. A key idea for the success of the new model is that the determination of atomic charges (describing an effective electron-electron interaction) and the one-particle spectrum is decoupled and treated by two differently parametrized Hamiltonians/basis sets. The three-diagonalization-step composite procedure can routinely compute broad range electronic spectra (0-8 eV) within minutes of computation time for systems composed of 500-1000 atoms with an accuracy typical of standard time-dependent density functional theory (0.3-0.5 eV average error). An easily extendable parametrization based on coupled-cluster and density functional computed reference data for the elements H–Zn including transition metals is described. The accuracy of the method termed sTDA-xTB is first

Ultra-fast computation of electronic spectra for large systems by tight-binding based simplified Tamm-Dancoff approximation (sTDA-xTB)

Energy Technology Data Exchange (ETDEWEB)

Grimme, Stefan, E-mail: grimme@thch.uni-bonn.de; Bannwarth, Christoph [Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, Rheinische Friedrich-Wilhelms Universität Bonn, Beringstraße 4, 53115 Bonn (Germany)

2016-08-07

The computational bottleneck of the extremely fast simplified Tamm-Dancoff approximated (sTDA) time-dependent density functional theory procedure [S. Grimme, J. Chem. Phys. 138, 244104 (2013)] for the computation of electronic spectra for large systems is the determination of the ground state Kohn-Sham orbitals and eigenvalues. This limits such treatments to single structures with a few hundred atoms and hence, e.g., sampling along molecular dynamics trajectories for flexible systems or the calculation of chromophore aggregates is often not possible. The aim of this work is to solve this problem by a specifically designed semi-empirical tight binding (TB) procedure similar to the well established self-consistent-charge density functional TB scheme. The new special purpose method provides orbitals and orbital energies of hybrid density functional character for a subsequent and basically unmodified sTDA procedure. Compared to many previous semi-empirical excited state methods, an advantage of the ansatz is that a general eigenvalue problem in a non-orthogonal, extended atomic orbital basis is solved and therefore correct occupied/virtual orbital energy splittings as well as Rydberg levels are obtained. A key idea for the success of the new model is that the determination of atomic charges (describing an effective electron-electron interaction) and the one-particle spectrum is decoupled and treated by two differently parametrized Hamiltonians/basis sets. The three-diagonalization-step composite procedure can routinely compute broad range electronic spectra (0-8 eV) within minutes of computation time for systems composed of 500-1000 atoms with an accuracy typical of standard time-dependent density functional theory (0.3-0.5 eV average error). An easily extendable parametrization based on coupled-cluster and density functional computed reference data for the elements H–Zn including transition metals is described. The accuracy of the method termed sTDA-xTB is first

The approximate inverse in action: IV. Semi-discrete equations in a Banach space setting

International Nuclear Information System (INIS)

Schuster, T; Schöpfer, F; Rieder, A

2012-01-01

This article concerns the method of approximate inverse to solve semi-discrete, linear operator equations in Banach spaces. Semi-discrete means that we search for a solution in an infinite-dimensional Banach space having only a finite number of data available. In this sense the situation is applicable to a large variety of applications where a measurement process delivers a discretization of an infinite-dimensional data space. The method of approximate inverse computes scalar products of the data with pre-computed reconstruction kernels which are associated with mollifiers and the dual of the model operator. The convergence, approximation power and regularization property of this method when applied to semi-discrete operator equations in Hilbert spaces has been investigated in three prequels to this paper. Here we extend these results to a Banach space setting. We prove convergence and stability for general Banach spaces and reproduce the results specifically for the integration operator acting on the space of continuous functions. (paper)

Local density approximation for exchange in excited-state density functional theory

OpenAIRE

Harbola, Manoj K.; Samal, Prasanjit

2004-01-01

Local density approximation for the exchange energy is made for treatment of excited-states in density-functional theory. It is shown that taking care of the state-dependence of the LDA exchange energy functional leads to accurate excitation energies.

Semi-Parametric Maximum Likelihood Method for Interaction in Case-Mother Control-Mother Designs: Package SPmlficmcm

Directory of Open Access Journals (Sweden)

Moliere Nguile-Makao

2015-12-01

Full Text Available The analysis of interaction effects involving genetic variants and environmental exposures on the risk of adverse obstetric and early-life outcomes is generally performed using standard logistic regression in the case-mother and control-mother design. However such an analysis is inefficient because it does not take into account the natural family-based constraints present in the parent-child relationship. Recently, a new approach based on semi-parametric maximum likelihood estimation was proposed. The advantage of this approach is that it takes into account the parental relationship between the mother and her child in estimation. But a package implementing this method has not been widely available. In this paper, we present SPmlficmcm, an R package implementing this new method and we propose an extension of the method to handle missing offspring genotype data by maximum likelihood estimation. Our choice to treat missing data of the offspring genotype was motivated by the fact that in genetic association studies where the genetic data of mother and child are available, there are usually more missing data on the genotype of the offspring than that of the mother. The package builds a non-linear system from the data and solves and computes the estimates from the gradient and the Hessian matrix of the log profile semi-parametric likelihood function. Finally, we analyze a simulated dataset to show the usefulness of the package.

Semi-classical approximation to path integrals - phases and catastrophes

International Nuclear Information System (INIS)

Levit, S.

1977-01-01

Problems of phases and catastrophes were encountered when trying to apply the classical S-matrix theory to the scattering phenomena in nuclear physics. The path integral formulation provided a suitable basis for the treatment of these and related problems. Within conventional mathematical language it was possible to give practical prescriptions and discuss their limitations. Since the semi-classical (stationary phase) approximation is commonly used in any application of the path integral method, the results are not restricted to the scattering problems and may be of general interest. The derivation of the uniform approximations in the energy representation should use the exact path integral expression as the starting point, rather than performing Fourier transforms on the expressions derived in the present lecture. (B.G.)

H-mode profile parametrization for extrapolation and control

International Nuclear Information System (INIS)

Imre, K.; Riedel, K.S.; Schissel, D.P.; Schunke, B.

1996-01-01

A steady-state ELMy H-mode profile data set of 68 DIII-D discharges and 74 JET discharges is fitted with an error of 7-8%. The advantages of a parametrization of the plasma profiles in terms of a semi-parametric representation, T(ρ, I p , n-bar, B t , P L , R), are described. The shape of the temperature profile depends almost exclusively upon the size, R and q 95 , with a secondary dependence on the heating power. The density profile depends primarily upon q95 with a secondary dependence on n-bar. The line-average temperature T-bar e scales as n-bar -0.31 instead of T-bar∼''n-bar'' -1.0 . The predicted ITER temperature is T-bar = 17.1 keV. (Author)

On exact and approximate exchange-energy densities

DEFF Research Database (Denmark)

Springborg, Michael; Dahl, Jens Peder

1999-01-01

Based on correspondence rules between quantum-mechanical operators and classical functions in phase space we construct exchange-energy densities in position space. Whereas these are not unique but depend on the chosen correspondence rule, the exchange potential is unique. We calculate this exchange......-energy density for 15 closed-shell atoms, and compare it with kinetic- and Coulomb-energy densities. It is found that it has a dominating local-density character, but electron-shell effects are recognizable. The approximate exchange-energy functionals that have been proposed so far are found to account only...

Application of semi parametric modelling to times series forecasting: case of the electricity consumption; Modeles semi-parametriques appliques a la prevision des series temporelles. Cas de la consommation d'electricite

Energy Technology Data Exchange (ETDEWEB)

Lefieux, V

2007-10-15

Reseau de Transport d'Electricite (RTE), in charge of operating the French electric transportation grid, needs an accurate forecast of the power consumption in order to operate it correctly. The forecasts used everyday result from a model combining a nonlinear parametric regression and a SARIMA model. In order to obtain an adaptive forecasting model, nonparametric forecasting methods have already been tested without real success. In particular, it is known that a nonparametric predictor behaves badly with a great number of explanatory variables, what is commonly called the curse of dimensionality. Recently, semi parametric methods which improve the pure nonparametric approach have been proposed to estimate a regression function. Based on the concept of 'dimension reduction', one those methods (called MAVE : Moving Average -conditional- Variance Estimate) can apply to time series. We study empirically its effectiveness to predict the future values of an autoregressive time series. We then adapt this method, from a practical point of view, to forecast power consumption. We propose a partially linear semi parametric model, based on the MAVE method, which allows to take into account simultaneously the autoregressive aspect of the problem and the exogenous variables. The proposed estimation procedure is practically efficient. (author)

Parametric excitation of nonlinear longitudinal oscillations in a magnetoactive plasma

International Nuclear Information System (INIS)

Demchenko, V.V.

1977-01-01

Parametric excitation by HF field of nonlinear longitudinal electron oscillations in the region of hybrid resonances of a cold nonrelativistic plasma has been investigated. It is shown that the inhomogeneity of a pumping field and that of the equilibrium plasma density result in the parametric instability. Expressions are derived for the increments of instable oscillations and the widths of the instability regions are determined. The increments of instable oscillations in the order of magnitude due to the inhomogeneities of the pumping field (γsub(E)) or of the plasma density (γsub(N)) are egual to γsub(E) approximately k(zetasub(0)) ωsub(pe), γsub(N) approximately (zetasub(0))/Lωsub(pe), where (zetasub(0))=(e)Esub(0)/msub(e)ωsub(0)sup(2) is the amplitude of displacement of an electron from the equilibrium state, k, ω 0 , E 0 are the wave number, frequency and amplitude of the pumping field, L is the characteristic size of the inhomogeneity of the plasma density, ωsub(pe) is the electron plasma frequency

Discrete least squares polynomial approximation with random evaluations − application to parametric and stochastic elliptic PDEs

KAUST Repository

Chkifa, Abdellah

2015-04-08

Motivated by the numerical treatment of parametric and stochastic PDEs, we analyze the least-squares method for polynomial approximation of multivariate functions based on random sampling according to a given probability measure. Recent work has shown that in the univariate case, the least-squares method is quasi-optimal in expectation in [A. Cohen, M A. Davenport and D. Leviatan. Found. Comput. Math. 13 (2013) 819–834] and in probability in [G. Migliorati, F. Nobile, E. von Schwerin, R. Tempone, Found. Comput. Math. 14 (2014) 419–456], under suitable conditions that relate the number of samples with respect to the dimension of the polynomial space. Here “quasi-optimal” means that the accuracy of the least-squares approximation is comparable with that of the best approximation in the given polynomial space. In this paper, we discuss the quasi-optimality of the polynomial least-squares method in arbitrary dimension. Our analysis applies to any arbitrary multivariate polynomial space (including tensor product, total degree or hyperbolic crosses), under the minimal requirement that its associated index set is downward closed. The optimality criterion only involves the relation between the number of samples and the dimension of the polynomial space, independently of the anisotropic shape and of the number of variables. We extend our results to the approximation of Hilbert space-valued functions in order to apply them to the approximation of parametric and stochastic elliptic PDEs. As a particular case, we discuss “inclusion type” elliptic PDE models, and derive an exponential convergence estimate for the least-squares method. Numerical results confirm our estimate, yet pointing out a gap between the condition necessary to achieve optimality in the theory, and the condition that in practice yields the optimal convergence rate.

The tensor hypercontracted parametric reduced density matrix algorithm: coupled-cluster accuracy with O(r(4)) scaling.

Science.gov (United States)

Shenvi, Neil; van Aggelen, Helen; Yang, Yang; Yang, Weitao; Schwerdtfeger, Christine; Mazziotti, David

2013-08-07

Tensor hypercontraction is a method that allows the representation of a high-rank tensor as a product of lower-rank tensors. In this paper, we show how tensor hypercontraction can be applied to both the electron repulsion integral tensor and the two-particle excitation amplitudes used in the parametric 2-electron reduced density matrix (p2RDM) algorithm. Because only O(r) auxiliary functions are needed in both of these approximations, our overall algorithm can be shown to scale as O(r(4)), where r is the number of single-particle basis functions. We apply our algorithm to several small molecules, hydrogen chains, and alkanes to demonstrate its low formal scaling and practical utility. Provided we use enough auxiliary functions, we obtain accuracy similar to that of the standard p2RDM algorithm, somewhere between that of CCSD and CCSD(T).

Parametric reduced models for the nonlinear Schrödinger equation.

Science.gov (United States)

Harlim, John; Li, Xiantao

2015-05-01

Reduced models for the (defocusing) nonlinear Schrödinger equation are developed. In particular, we develop reduced models that only involve the low-frequency modes given noisy observations of these modes. The ansatz of the reduced parametric models are obtained by employing a rational approximation and a colored-noise approximation, respectively, on the memory terms and the random noise of a generalized Langevin equation that is derived from the standard Mori-Zwanzig formalism. The parameters in the resulting reduced models are inferred from noisy observations with a recently developed ensemble Kalman filter-based parametrization method. The forecasting skill across different temperature regimes are verified by comparing the moments up to order four, a two-time correlation function statistics, and marginal densities of the coarse-grained variables.

Dynamic hysteresis of a uniaxial superparamagnet: Semi-adiabatic approximation

International Nuclear Information System (INIS)

Poperechny, I.S.; Raikher, Yu.L.; Stepanov, V.I.

2014-01-01

The semi-adiabatic theory of magnetic response of a uniaxial single-domain ferromagnetic particle is presented. The approach is developed in the context of the kinetic theory and allows for any orientation of the external field. Within this approximation, the dynamic magnetic hysteresis loops in an ac field are calculated. It is demonstrated that they very closely resemble those obtained by the full kinetic theory. The behavior of the effective coercive force is analyzed in detail, and for it a simple formula is proposed. This relation accounts not only for the temperature behavior of the coercive force, as the previous ones do, but also yields the dependence on the frequency and amplitude of the applied field

truncSP: An R Package for Estimation of Semi-Parametric Truncated Linear Regression Models

Directory of Open Access Journals (Sweden)

Maria Karlsson

2014-05-01

Full Text Available Problems with truncated data occur in many areas, complicating estimation and inference. Regarding linear regression models, the ordinary least squares estimator is inconsistent and biased for these types of data and is therefore unsuitable for use. Alternative estimators, designed for the estimation of truncated regression models, have been developed. This paper presents the R package truncSP. The package contains functions for the estimation of semi-parametric truncated linear regression models using three different estimators: the symmetrically trimmed least squares, quadratic mode, and left truncated estimators, all of which have been shown to have good asymptotic and ?nite sample properties. The package also provides functions for the analysis of the estimated models. Data from the environmental sciences are used to illustrate the functions in the package.

B97-3c: A revised low-cost variant of the B97-D density functional method

Science.gov (United States)

Brandenburg, Jan Gerit; Bannwarth, Christoph; Hansen, Andreas; Grimme, Stefan

2018-02-01

A revised version of the well-established B97-D density functional approximation with general applicability for chemical properties of large systems is proposed. Like B97-D, it is based on Becke's power-series ansatz from 1997 and is explicitly parametrized by including the standard D3 semi-classical dispersion correction. The orbitals are expanded in a modified valence triple-zeta Gaussian basis set, which is available for all elements up to Rn. Remaining basis set errors are mostly absorbed in the modified B97 parametrization, while an established atom-pairwise short-range potential is applied to correct for the systematically too long bonds of main group elements which are typical for most semi-local density functionals. The new composite scheme (termed B97-3c) completes the hierarchy of "low-cost" electronic structure methods, which are all mainly free of basis set superposition error and account for most interactions in a physically sound and asymptotically correct manner. B97-3c yields excellent molecular and condensed phase geometries, similar to most hybrid functionals evaluated in a larger basis set expansion. Results on the comprehensive GMTKN55 energy database demonstrate its good performance for main group thermochemistry, kinetics, and non-covalent interactions, when compared to functionals of the same class. This also transfers to metal-organic reactions, which is a major area of applicability for semi-local functionals. B97-3c can be routinely applied to hundreds of atoms on a single processor and we suggest it as a robust computational tool, in particular, for more strongly correlated systems where our previously published "3c" schemes might be problematic.

A Robust Semi-Parametric Test for Detecting Trait-Dependent Diversification.

Science.gov (United States)

Rabosky, Daniel L; Huang, Huateng

2016-03-01

Rates of species diversification vary widely across the tree of life and there is considerable interest in identifying organismal traits that correlate with rates of speciation and extinction. However, it has been challenging to develop methodological frameworks for testing hypotheses about trait-dependent diversification that are robust to phylogenetic pseudoreplication and to directionally biased rates of character change. We describe a semi-parametric test for trait-dependent diversification that explicitly requires replicated associations between character states and diversification rates to detect effects. To use the method, diversification rates are reconstructed across a phylogenetic tree with no consideration of character states. A test statistic is then computed to measure the association between species-level traits and the corresponding diversification rate estimates at the tips of the tree. The empirical value of the test statistic is compared to a null distribution that is generated by structured permutations of evolutionary rates across the phylogeny. The test is applicable to binary discrete characters as well as continuous-valued traits and can accommodate extremely sparse sampling of character states at the tips of the tree. We apply the test to several empirical data sets and demonstrate that the method has acceptable Type I error rates. © The Author(s) 2015. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Spin-Density Functionals from Current-Density Functional Theory and Vice Versa: A Road towards New Approximations

International Nuclear Information System (INIS)

Capelle, K.; Gross, E.

1997-01-01

It is shown that the exchange-correlation functional of spin-density functional theory is identical, on a certain set of densities, with the exchange-correlation functional of current-density functional theory. This rigorous connection is used to construct new approximations of the exchange-correlation functionals. These include a conceptually new generalized-gradient spin-density functional and a nonlocal current-density functional. copyright 1997 The American Physical Society

Hamiltonian structure of isospectral deformation equation and semi-classical approximation to factorized S-matrices

International Nuclear Information System (INIS)

Chudnovsky, D.V.; Chudnovsky, G.V.

1980-01-01

We consider semi-classical approximation to factorized S-matrices. We show that this new class of matrices, called s-matrices, defines Hamiltonian structures for isospectral deformation equations. Concrete examples of factorized s-matrices are constructed and they are used to define Hamiltonian structure for general two-dimensional isospectral deformation systems. (orig.)

Calculation of the level density parameter using semi-classical approach

International Nuclear Information System (INIS)

Canbula, B.; Babacan, H.

2011-01-01

The level density parameters (level density parameter a and energy shift δ) for back-shifted Fermi gas model have been determined for 1136 nuclei for which complete level scheme is available. Level density parameter is calculated by using the semi-classical single particle level density, which can be obtained analytically through spherical harmonic oscillator potential. This method also enables us to analyze the Coulomb potential's effect on the level density parameter. The dependence of this parameter on energy has been also investigated. Another parameter, δ, is determined by fitting of the experimental level scheme and the average resonance spacings for 289 nuclei. Only level scheme is used for optimization procedure for remaining 847 nuclei. Level densities for some nuclei have been calculated by using these parameter values. Obtained results have been compared with the experimental level scheme and the resonance spacing data.

Subsystem density functional theory with meta-generalized gradient approximation exchange-correlation functionals.

Science.gov (United States)

Śmiga, Szymon; Fabiano, Eduardo; Laricchia, Savio; Constantin, Lucian A; Della Sala, Fabio

2015-04-21

We analyze the methodology and the performance of subsystem density functional theory (DFT) with meta-generalized gradient approximation (meta-GGA) exchange-correlation functionals for non-bonded molecular systems. Meta-GGA functionals depend on the Kohn-Sham kinetic energy density (KED), which is not known as an explicit functional of the density. Therefore, they cannot be directly applied in subsystem DFT calculations. We propose a Laplacian-level approximation to the KED which overcomes this limitation and provides a simple and accurate way to apply meta-GGA exchange-correlation functionals in subsystem DFT calculations. The so obtained density and energy errors, with respect to the corresponding supermolecular calculations, are comparable with conventional approaches, depending almost exclusively on the approximations in the non-additive kinetic embedding term. An embedding energy error decomposition explains the accuracy of our method.

Semi-implicit magnetohydrodynamic calculations

International Nuclear Information System (INIS)

Schnack, D.D.; Barnes, D.C.; Mikic, Z.; Harned, D.S.; Caramana, E.J.

1987-01-01

A semi-implicit algorithm for the solution of the nonlinear, three-dimensional, resistive MHD equations in cylindrical geometry is presented. The specific model assumes uniform density and pressure, although this is not a restriction of the method. The spatial approximation employs finite differences in the radial coordinate, and the pseudo-spectral algorithm in the periodic poloidal and axial coordinates. A leapfrog algorithm is used to advance wave-like terms; advective terms are treated with a simple predictor--corrector method. The semi-implicit term is introduced as a simple modification to the momentum equation. Dissipation is treated implicitly. The resulting algorithm is unconditionally stable with respect to normal modes. A general discussion of the semi-implicit method is given, and specific forms of the semi-implicit operator are compared in physically relevant test cases. Long-time simulations are presented. copyright 1987 Academic Press, Inc

Parametric FEM for geometric biomembranes

Science.gov (United States)

Bonito, Andrea; Nochetto, Ricardo H.; Sebastian Pauletti, M.

2010-05-01

We consider geometric biomembranes governed by an L2-gradient flow for bending energy subject to area and volume constraints (Helfrich model). We give a concise derivation of a novel vector formulation, based on shape differential calculus, and corresponding discretization via parametric FEM using quadratic isoparametric elements and a semi-implicit Euler method. We document the performance of the new parametric FEM with a number of simulations leading to dumbbell, red blood cell and toroidal equilibrium shapes while exhibiting large deformations.

Quantal density functional theory II. Approximation methods and applications

International Nuclear Information System (INIS)

Sahni, Viraht

2010-01-01

This book is on approximation methods and applications of Quantal Density Functional Theory (QDFT), a new local effective-potential-energy theory of electronic structure. What distinguishes the theory from traditional density functional theory is that the electron correlations due to the Pauli exclusion principle, Coulomb repulsion, and the correlation contribution to the kinetic energy -- the Correlation-Kinetic effects -- are separately and explicitly defined. As such it is possible to study each property of interest as a function of the different electron correlations. Approximations methods based on the incorporation of different electron correlations, as well as a many-body perturbation theory within the context of QDFT, are developed. The applications are to the few-electron inhomogeneous electron gas systems in atoms and molecules, as well as to the many-electron inhomogeneity at metallic surfaces. (orig.)

Bridge density functional approximation for non-uniform hard core repulsive Yukawa fluid

International Nuclear Information System (INIS)

Zhou Shiqi

2008-01-01

In this work, a bridge density functional approximation (BDFA) (J. Chem. Phys. 112, 8079 (2000)) for a non-uniform hard-sphere fluid is extended to a non-uniform hard-core repulsive Yukawa (HCRY) fluid. It is found that the choice of a bulk bridge functional approximation is crucial for both a uniform HCRY fluid and a non-uniform HCRY fluid. A new bridge functional approximation is proposed, which can accurately predict the radial distribution function of the bulk HCRY fluid. With the new bridge functional approximation and its associated bulk second order direct correlation function as input, the BDFA can be used to well calculate the density profile of the HCRY fluid subjected to the influence of varying external fields, and the theoretical predictions are in good agreement with the corresponding simulation data. The calculated results indicate that the present BDFA captures quantitatively the phenomena such as the coexistence of solid-like high density phase and low density gas phase, and the adsorption properties of the HCRY fluid, which qualitatively differ from those of the fluids combining both hard-core repulsion and an attractive tail. (condensed matter: structure, thermal and mechanical properties)

Semi-empirical neutron tool calibration (one and two-group approximation)

International Nuclear Information System (INIS)

Czubek, J.A.

1988-01-01

The physical principles of the new method of calibration of neutron tools for the rock porosity determination are given. A short description of the physics of neutron transport in the matter is presented together with some remarks on the elementary interactions of neutrons with nuclei (cross sections, group cross sections etc.). The definitions of the main integral parameters characterizing the neutron transport in the rock media are given. The three main approaches to the calibration problem: empirical, theoretical and semi-empirical are presented with some more detailed description of the latter one. The new semi-empirical approach is described. The method is based on the definition of the apparent slowing down or migration length for neutrons sensed by the neutron tool situated in the real borehole-rock conditions. To calculate this apparent slowing down or migration lengths the ratio of the proper space moments of the neutron distribution along the borehole axis is used. Theoretical results are given for one- and two-group diffusion approximations in the rock-borehole geometrical conditions when the tool is in the sidewall position. The physical and chemical parameters are given for the calibration blocks of the Logging Company in Zielona Gora. Using these data the neutron parameters of the calibration blocks have been calculated. An example, how to determine the calibration curve for the dual detector tool applying this new method and using the neutron parameters mentioned above together with the measurements performed in the calibration blocks, is given. The most important advantage of the new semi-empirical method of calibration is the possibility of setting on the unique calibration curve all experimental calibration data obtained for a given neutron tool for different porosities, lithologies and borehole diameters. 52 refs., 21 figs., 21 tabs. (author)

Balancing Exchange Mixing in Density-Functional Approximations for Iron Porphyrin.

Science.gov (United States)

Berryman, Victoria E J; Boyd, Russell J; Johnson, Erin R

2015-07-14

Predicting the correct ground-state multiplicity for iron(II) porphyrin, a high-spin quintet, remains a significant challenge for electronic-structure methods, including commonly employed density functionals. An even greater challenge for these methods is correctly predicting favorable binding of O2 to iron(II) porphyrin, due to the open-shell singlet character of the adduct. In this work, the performance of a modest set of contemporary density-functional approximations is assessed and the results interpreted using Bader delocalization indices. It is found that inclusion of greater proportions of Hartree-Fock exchange, in hybrid or range-separated hybrid functionals, has opposing effects; it improves the ability of the functional to identify the ground state but is detrimental to predicting favorable dioxygen binding. Because of the uncomplementary nature of these properties, accurate prediction of both the relative spin-state energies and the O2 binding enthalpy eludes conventional density-functional approximations.

Parametric resonance in neutrino oscillation: A guide to control the effects of inhomogeneous matter density

International Nuclear Information System (INIS)

Koike, Masafumi; Ota, Toshihiko; Saito, Masako; Sato, Joe

2016-01-01

Effects of the inhomogeneous matter density on the three-generation neutrino oscillation probability are analyzed. Realistic profile of the matter density is expanded into a Fourier series. Taking in the Fourier modes one by one, we demonstrate that each mode has its corresponding target energy. The high Fourier mode selectively modifies the oscillation probability of the low-energy region. This rule is well described by the parametric resonance between the neutrino oscillation and the matter effect. The Fourier analysis gives a simple guideline to systematically control the uncertainty of the oscillation probability caused by the uncertain density of matter. Precise analysis of the oscillation probability down to the low-energy region requires accurate evaluation of the Fourier coefficients of the matter density up to the corresponding high modes.

Applications of Skyrme energy-density functional to fusion reactions spanning the fusion barriers

International Nuclear Information System (INIS)

Liu Min; Wang, Ning; Li Zhuxia; Wu Xizhen; Zhao Enguang

2006-01-01

The Skyrme energy density functional has been applied to the study of heavy-ion fusion reactions. The barriers for fusion reactions are calculated by the Skyrme energy density functional with proton and neutron density distributions determined by using restricted density variational (RDV) method within the same energy density functional together with semi-classical approach known as the extended semi-classical Thomas-Fermi method. Based on the fusion barrier obtained, we propose a parametrization of the empirical barrier distribution to take into account the multi-dimensional character of real barrier and then apply it to calculate the fusion excitation functions in terms of barrier penetration concept. A large number of measured fusion excitation functions spanning the fusion barriers can be reproduced well. The competition between suppression and enhancement effects on sub-barrier fusion caused by neutron-shell-closure and excess neutron effects is studied

Smooth semi-nonparametric (SNP) estimation of the cumulative incidence function.

Science.gov (United States)

Duc, Anh Nguyen; Wolbers, Marcel

2017-08-15

This paper presents a novel approach to estimation of the cumulative incidence function in the presence of competing risks. The underlying statistical model is specified via a mixture factorization of the joint distribution of the event type and the time to the event. The time to event distributions conditional on the event type are modeled using smooth semi-nonparametric densities. One strength of this approach is that it can handle arbitrary censoring and truncation while relying on mild parametric assumptions. A stepwise forward algorithm for model estimation and adaptive selection of smooth semi-nonparametric polynomial degrees is presented, implemented in the statistical software R, evaluated in a sequence of simulation studies, and applied to data from a clinical trial in cryptococcal meningitis. The simulations demonstrate that the proposed method frequently outperforms both parametric and nonparametric alternatives. They also support the use of 'ad hoc' asymptotic inference to derive confidence intervals. An extension to regression modeling is also presented, and its potential and challenges are discussed. © 2017 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd. © 2017 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd.

APPROXIMATION OF FREE-FORM CURVE – AIRFOIL SHAPE

Directory of Open Access Journals (Sweden)

CHONG PERK LIN

2013-12-01

Full Text Available Approximation of free-form shape is essential in numerous engineering applications, particularly in automotive and aircraft industries. Commercial CAD software for the approximation of free-form shape is based almost exclusively on parametric polynomial and rational parametric polynomial. The parametric curve is defined by vector function of one independent variable R(u = (x(u, y(u, z(u, where 0≤u≤1. Bézier representation is one of the parametric functions, which is widely used in the approximating of free-form shape. Given a string of points with the assumption of sufficiently dense to characterise airfoil shape, it is desirable to approximate the shape with Bézier representation. The expectation is that the representation function is close to the shape within an acceptable working tolerance. In this paper, the aim is to explore the use of manual and automated methods for approximating section curve of airfoil with Bézier representation.

Semi-local machine-learned kinetic energy density functional with third-order gradients of electron density

Science.gov (United States)

Seino, Junji; Kageyama, Ryo; Fujinami, Mikito; Ikabata, Yasuhiro; Nakai, Hiromi

2018-06-01

A semi-local kinetic energy density functional (KEDF) was constructed based on machine learning (ML). The present scheme adopts electron densities and their gradients up to third-order as the explanatory variables for ML and the Kohn-Sham (KS) kinetic energy density as the response variable in atoms and molecules. Numerical assessments of the present scheme were performed in atomic and molecular systems, including first- and second-period elements. The results of 37 conventional KEDFs with explicit formulae were also compared with those of the ML KEDF with an implicit formula. The inclusion of the higher order gradients reduces the deviation of the total kinetic energies from the KS calculations in a stepwise manner. Furthermore, our scheme with the third-order gradient resulted in the closest kinetic energies to the KS calculations out of the presented functionals.

Total-energy Assisted Tight-binding Method Based on Local Density Approximation of Density Functional Theory

Science.gov (United States)

Fujiwara, Takeo; Nishino, Shinya; Yamamoto, Susumu; Suzuki, Takashi; Ikeda, Minoru; Ohtani, Yasuaki

2018-06-01

A novel tight-binding method is developed, based on the extended Hückel approximation and charge self-consistency, with referring the band structure and the total energy of the local density approximation of the density functional theory. The parameters are so adjusted by computer that the result reproduces the band structure and the total energy, and the algorithm for determining parameters is established. The set of determined parameters is applicable to a variety of crystalline compounds and change of lattice constants, and, in other words, it is transferable. Examples are demonstrated for Si crystals of several crystalline structures varying lattice constants. Since the set of parameters is transferable, the present tight-binding method may be applicable also to molecular dynamics simulations of large-scale systems and long-time dynamical processes.

Finite Gaussian Mixture Approximations to Analytically Intractable Density Kernels

DEFF Research Database (Denmark)

Khorunzhina, Natalia; Richard, Jean-Francois

The objective of the paper is that of constructing finite Gaussian mixture approximations to analytically intractable density kernels. The proposed method is adaptive in that terms are added one at the time and the mixture is fully re-optimized at each step using a distance measure that approxima...

Recent developments in LIBXC - A comprehensive library of functionals for density functional theory

Science.gov (United States)

Lehtola, Susi; Steigemann, Conrad; Oliveira, Micael J. T.; Marques, Miguel A. L.

2018-01-01

LIBXC is a library of exchange-correlation functionals for density-functional theory. We are concerned with semi-local functionals (or the semi-local part of hybrid functionals), namely local-density approximations, generalized-gradient approximations, and meta-generalized-gradient approximations. Currently we include around 400 functionals for the exchange, correlation, and the kinetic energy, spanning more than 50 years of research. Moreover, LIBXC is by now used by more than 20 codes, not only from the atomic, molecular, and solid-state physics, but also from the quantum chemistry communities.

The relationship between multilevel models and non-parametric multilevel mixture models: Discrete approximation of intraclass correlation, random coefficient distributions, and residual heteroscedasticity.

Science.gov (United States)

Rights, Jason D; Sterba, Sonya K

2016-11-01

Multilevel data structures are common in the social sciences. Often, such nested data are analysed with multilevel models (MLMs) in which heterogeneity between clusters is modelled by continuously distributed random intercepts and/or slopes. Alternatively, the non-parametric multilevel regression mixture model (NPMM) can accommodate the same nested data structures through discrete latent class variation. The purpose of this article is to delineate analytic relationships between NPMM and MLM parameters that are useful for understanding the indirect interpretation of the NPMM as a non-parametric approximation of the MLM, with relaxed distributional assumptions. We define how seven standard and non-standard MLM specifications can be indirectly approximated by particular NPMM specifications. We provide formulas showing how the NPMM can serve as an approximation of the MLM in terms of intraclass correlation, random coefficient means and (co)variances, heteroscedasticity of residuals at level 1, and heteroscedasticity of residuals at level 2. Further, we discuss how these relationships can be useful in practice. The specific relationships are illustrated with simulated graphical demonstrations, and direct and indirect interpretations of NPMM classes are contrasted. We provide an R function to aid in implementing and visualizing an indirect interpretation of NPMM classes. An empirical example is presented and future directions are discussed. © 2016 The British Psychological Society.

Parametric dependence of density limits in the Tokamak Experiment for Technology Oriented Research (TEXTOR): Comparison of thermal instability theory with experiment

International Nuclear Information System (INIS)

Kelly, F.A.; Stacey, W.M.; Rapp, J.

2001-01-01

The observed dependence of the TEXTOR [Tokamak Experiment for Technology Oriented Research: E. Hintz, P. Bogen, H. A. Claassen et al., Contributions to High Temperature Plasma Physics, edited by K. H. Spatschek and J. Uhlenbusch (Akademie Verlag, Berlin, 1994), p. 373] density limit on global parameters (I, B, P, etc.) and wall conditioning is compared with the predicted density limit parametric scaling of thermal instability theory. It is necessary first to relate the edge parameters of the thermal instability theory to n(bar sign) and the other global parameters. The observed parametric dependence of the density limit in TEXTOR is generally consistent with the predicted density limit scaling of thermal instability theory. The observed wall conditioning dependence of the density limit can be reconciled with the theory in terms of the radiative emissivity temperature dependence of different impurities in the plasma edge. The thermal instability theory also provides an explanation of why symmetric detachment precedes radiative collapse for most low power shots, while a multifaceted asymmetric radiation from the edge MARFE precedes detachment for most high power shots

Cuckoo Search Algorithm with Lévy Flights for Global-Support Parametric Surface Approximation in Reverse Engineering

Directory of Open Access Journals (Sweden)

Andrés Iglesias

2018-03-01

Full Text Available This paper concerns several important topics of the Symmetry journal, namely, computer-aided design, computational geometry, computer graphics, visualization, and pattern recognition. We also take advantage of the symmetric structure of the tensor-product surfaces, where the parametric variables u and v play a symmetric role in shape reconstruction. In this paper we address the general problem of global-support parametric surface approximation from clouds of data points for reverse engineering applications. Given a set of measured data points, the approximation is formulated as a nonlinear continuous least-squares optimization problem. Then, a recent metaheuristics called Cuckoo Search Algorithm (CSA is applied to compute all relevant free variables of this minimization problem (namely, the data parameters and the surface poles. The method includes the iterative generation of new solutions by using the Lévy flights to promote the diversity of solutions and prevent stagnation. A critical advantage of this method is its simplicity: the CSA requires only two parameters, many fewer than any other metaheuristic approach, so the parameter tuning becomes a very easy task. The method is also simple to understand and easy to implement. Our approach has been applied to a benchmark of three illustrative sets of noisy data points corresponding to surfaces exhibiting several challenging features. Our experimental results show that the method performs very well even for the cases of noisy and unorganized data points. Therefore, the method can be directly used for real-world applications for reverse engineering without further pre/post-processing. Comparative work with the most classical mathematical techniques for this problem as well as a recent modification of the CSA called Improved CSA (ICSA is also reported. Two nonparametric statistical tests show that our method outperforms the classical mathematical techniques and provides equivalent results to ICSA

Common approximations for density operators may lead to imaginary entropy

International Nuclear Information System (INIS)

Lendi, K.; Amaral Junior, M.R. do

1983-01-01

The meaning and validity of usual second order approximations for density operators are illustrated with the help of a simple exactly soluble two-level model in which all relevant quantities can easily be controlled. This leads to exact upper bound error estimates which help to select more precisely permissible correlation times as frequently introduced if stochastic potentials are present. A final consideration of information entropy reveals clearly the limitations of this kind of approximation procedures. (Author) [pt

Weighted density approximation for bonding in molecules: ring and cage polymers

CERN Document Server

Sweatman, M B

2003-01-01

The focus of this work is the bonded contribution to the intrinsic Helmholtz free energy of molecules. A weighted density approximation (WDA) for this contribution is presented within the interaction site model (ISM) for ring and cage polymers. The resulting density functional theory (ISM/WDA) for these systems is no more complex than theories for a pure simple fluid, and much less complex than density functional approaches that treat the bonding functional exactly. The ISM/WDA bonding functional is much more accurate than either the ISM/HNC or ISM/PY bonding functionals, which are related to the reference interaction-site model (RISM)/HNC and RISM/PY integral equations respectively, for ideal ring polymers. This means that the ISM/WDA functional should generally be more accurate for most 'real' ring or cage polymer systems when any reasonable approximation for the 'excess' contribution to the intrinsic Helmholtz free energy is employed.

Weighted density approximation for bonding in molecules: ring and cage polymers

International Nuclear Information System (INIS)

Sweatman, M B

2003-01-01

The focus of this work is the bonded contribution to the intrinsic Helmholtz free energy of molecules. A weighted density approximation (WDA) for this contribution is presented within the interaction site model (ISM) for ring and cage polymers. The resulting density functional theory (ISM/WDA) for these systems is no more complex than theories for a pure simple fluid, and much less complex than density functional approaches that treat the bonding functional exactly. The ISM/WDA bonding functional is much more accurate than either the ISM/HNC or ISM/PY bonding functionals, which are related to the reference interaction-site model (RISM)/HNC and RISM/PY integral equations respectively, for ideal ring polymers. This means that the ISM/WDA functional should generally be more accurate for most 'real' ring or cage polymer systems when any reasonable approximation for the 'excess' contribution to the intrinsic Helmholtz free energy is employed

Pairing renormalization and regularization within the local density approximation

International Nuclear Information System (INIS)

Borycki, P.J.; Dobaczewski, J.; Nazarewicz, W.; Stoitsov, M.V.

2006-01-01

We discuss methods used in mean-field theories to treat pairing correlations within the local density approximation. Pairing renormalization and regularization procedures are compared in spherical and deformed nuclei. Both prescriptions give fairly similar results, although the theoretical motivation, simplicity, and stability of the regularization procedure make it a method of choice for future applications

Semi-classical approximation and the problem of boundary conditions in the theory of relativistic particle radiation

International Nuclear Information System (INIS)

Akhiezer, A.I.; Shul'ga, N.F.

1991-01-01

The process of relativistic particle radiation in an external field has been studied in the semi-classical approximation rather extensively. The main problem arising in the studies is in expressing the formula of the quantum theory of radiation in terms of classical quantities, for example of the classical trajectories. However, it still remains unclear how the particle trajectory is assigned, that is which particular initial or boundary conditions determine the trajectory in semi-classical approximation quantum theory of radiation. We shall try to solve this problem. Its importance comes from the fact that in some cases one and the same boundary conditions may give rise to two or more trajectories. We demonstrate that this fact must necessarily be taken into account on deriving the classical limit for the formulae of the quantum theory of radiation, since it leads to a specific interference effect in radiation. The method we used to deal with the problem is similar to the method employed by Fock to analyze the problem of a canonical transformation in classical and quantum mechanics. (author)

Semi-analytical modelling of positive corona discharge in air

Science.gov (United States)

Pontiga, Francisco; Yanallah, Khelifa; Chen, Junhong

2013-09-01

Semianalytical approximate solutions of the spatial distribution of electric field and electron and ion densities have been obtained by solving Poisson's equations and the continuity equations for the charged species along the Laplacian field lines. The need to iterate for the correct value of space charge on the corona electrode has been eliminated by using the corona current distribution over the grounded plane derived by Deutsch, which predicts a cos m θ law similar to Warburg's law. Based on the results of the approximated model, a parametric study of the influence of gas pressure, the corona wire radius, and the inter-electrode wire-plate separation has been carried out. Also, the approximate solutions of the electron number density has been combined with a simplified plasma chemistry model in order to compute the ozone density generated by the corona discharge in the presence of a gas flow. This work was supported by the Consejeria de Innovacion, Ciencia y Empresa (Junta de Andalucia) and by the Ministerio de Ciencia e Innovacion, Spain, within the European Regional Development Fund contracts FQM-4983 and FIS2011-25161.

A test of the mean density approximation for Lennard-Jones mixtures with large size ratios

International Nuclear Information System (INIS)

Ely, J.F.

1986-01-01

The mean density approximation for mixture radial distribution functions plays a central role in modern corresponding-states theories. This approximation is reasonably accurate for systems that do not differ widely in size and energy ratios and which are nearly equimolar. As the size ratio increases, however, or if one approaches an infinite dilution of one of the components, the approximation becomes progressively worse, especially for the small molecule pair. In an attempt to better understand and improve this approximation, isothermal molecular dynamics simulations have been performed on a series of Lennard-Jones mixtures. Thermodynamic properties, including the mixture radial distribution functions, have been obtained at seven compositions ranging from 5 to 95 mol%. In all cases the size ratio was fixed at two and three energy ratios were investigated, 22 / 11 =0.5, 1.0, and 1.5. The results of the simulations are compared with the mean density approximation and a modification to integrals evaluated with the mean density approximation is proposed

Semi-automatic assessment of skin capillary density: proof of principle and validation.

Science.gov (United States)

Gronenschild, E H B M; Muris, D M J; Schram, M T; Karaca, U; Stehouwer, C D A; Houben, A J H M

2013-11-01

Skin capillary density and recruitment have been proven to be relevant measures of microvascular function. Unfortunately, the assessment of skin capillary density from movie files is very time-consuming, since this is done manually. This impedes the use of this technique in large-scale studies. We aimed to develop a (semi-) automated assessment of skin capillary density. CapiAna (Capillary Analysis) is a newly developed semi-automatic image analysis application. The technique involves four steps: 1) movement correction, 2) selection of the frame range and positioning of the region of interest (ROI), 3) automatic detection of capillaries, and 4) manual correction of detected capillaries. To gain insight into the performance of the technique, skin capillary density was measured in twenty participants (ten women; mean age 56.2 [42-72] years). To investigate the agreement between CapiAna and the classic manual counting procedure, we used weighted Deming regression and Bland-Altman analyses. In addition, intra- and inter-observer coefficients of variation (CVs), and differences in analysis time were assessed. We found a good agreement between CapiAna and the classic manual method, with a Pearson's correlation coefficient (r) of 0.95 (Pdifferences between the two methods, with an intercept of the Deming regression of 1.75 (-6.04; 9.54), while the Bland-Altman analysis showed a mean difference (bias) of 2.0 (-13.5; 18.4) capillaries/mm(2). The intra- and inter-observer CVs of CapiAna were 2.5% and 5.6% respectively, while for the classic manual counting procedure these were 3.2% and 7.2%, respectively. Finally, the analysis time for CapiAna ranged between 25 and 35min versus 80 and 95min for the manual counting procedure. We have developed a semi-automatic image analysis application (CapiAna) for the assessment of skin capillary density, which agrees well with the classic manual counting procedure, is time-saving, and has a better reproducibility as compared to the

Long-range-corrected Rung 3.5 density functional approximations

Science.gov (United States)

Janesko, Benjamin G.; Proynov, Emil; Scalmani, Giovanni; Frisch, Michael J.

2018-03-01

Rung 3.5 functionals are a new class of approximations for density functional theory. They provide a flexible intermediate between exact (Hartree-Fock, HF) exchange and semilocal approximations for exchange. Existing Rung 3.5 functionals inherit semilocal functionals' limitations in atomic cores and density tails. Here we address those limitations using range-separated admixture of HF exchange. We present three new functionals. LRC-ωΠLDA combines long-range HF exchange with short-range Rung 3.5 ΠLDA exchange. SLC-ΠLDA combines short- and long-range HF exchange with middle-range ΠLDA exchange. LRC-ωΠLDA-AC incorporates a combination of HF, semilocal, and Rung 3.5 exchange in the short range, based on an adiabatic connection. We test these in a new Rung 3.5 implementation including up to analytic fourth derivatives. LRC-ωΠLDA and SLC-ΠLDA improve atomization energies and reaction barriers by a factor of 8 compared to the full-range ΠLDA. LRC-ωΠLDA-AC brings further improvement approaching the accuracy of standard long-range corrected schemes LC-ωPBE and SLC-PBE. The new functionals yield highest occupied orbital energies closer to experimental ionization potentials and describe correctly the weak charge-transfer complex of ethylene and dichlorine and the hole-spin distribution created by an Al defect in quartz. This study provides a framework for more flexible range-separated Rung 3.5 approximations.

Characterising root density of peach trees in a semi-arid Chernozem to increase plant density

Science.gov (United States)

Paltineanu, Cristian; Septar, Leinar; Gavat, Corina; Chitu, Emil; Oprita, Alexandru; Moale, Cristina; Calciu, Irina; Vizitiu, Olga; Lamureanu, Gheorghe

2016-01-01

The available information on root system in fully mature peach orchards in semi-arid regions is insufficient. This paper presents a study on the root system density in an irrigated peach orchard from Dobrogea, Romania, using the trench technique. The old orchard has clean cultivation in inter-row and in-row. The objectives of the study were to: test the hypothesis that the roots of fully mature peach trees occupy the whole soil volume; find out if root repulsive effect of adjacent plants occurred for the rootstocks and soil conditions; find relationships between root system and soil properties and analyse soil state trend. Some soil physical properties were significantly deteriorated in inter-row versus in-row, mainly due to soil compaction induced by technological traffic. Density of total roots was higher in-row than inter-row, but the differences were not significant. Root density decreased more intensely with soil depth than with distance from tree trunks. Root density correlated with some soil properties. No repulsive effect of the roots of adjacent peach trees was noted. The decrease of root density with distance from trunk can be used in optimising tree arrangement. The conclusions could also be used in countries with similar growth conditions.

Approximation of the semi-infinite interval

Directory of Open Access Journals (Sweden)

A. McD. Mercer

1980-01-01

Full Text Available The approximation of a function f∈C[a,b] by Bernstein polynomials is well-known. It is based on the binomial distribution. O. Szasz has shown that there are analogous approximations on the interval [0,∞ based on the Poisson distribution. Recently R. Mohapatra has generalized Szasz' result to the case in which the approximating function is αe−ux∑k=N∞(uxkα+β−1Γ(kα+βf(kαuThe present note shows that these results are special cases of a Tauberian theorem for certain infinite series having positive coefficients.

Self-consistent-field calculations of atoms and ions using a modified local-density approximation

International Nuclear Information System (INIS)

Liberman, D.A.; Albritton, J.R.; Wilson, B.G.; Alley, W.E.

1994-01-01

Local-density-approximation calculations of atomic structure are useful for the description of atoms and ions in plasmas. The large number of different atomic configurations that exist in typical plasmas leads one to consider the expression of total energies in terms of a Taylor series in the orbital occupation numbers. Two schemes for computing the second derivative Taylor-series coefficients are given; the second, and better one, uses the linear response method developed by Zangwill and Soven [Phys. Rev. A 21, 1561 (1980)] for the calculation of optical response in atoms. A defect in the local-density approximation causes some second derivatives involving Rydberg orbitals to be infinite. This is corrected by using a modified local-density approximation that had previously been proposed [Phys. Rev. B 2, 244 (1970)

Parametric Study on the Characteristics of Multiphase Laminar Flow with Density Difference in Various Microchannels

International Nuclear Information System (INIS)

Paek, Seung Ho; Kim, Dong Sung; Choi, Young Ki

2009-01-01

In this paper, we have performed a parametric study on the characteristics of multiphase laminar flow with density difference in various microchannels. The interface between multiphase fluids is rotated by the gravitational forces induced by density difference. The numerical simulations were carried out via commercial CFD package to study the characteristics of multiphase laminar flow. The results of the numerical simulations in this study were verified by comparing with the previously reported experimental results in the literature. We have also proposed a new dimensionless relationship between dimensionless rotation angle of interface and dimensionless parameters are proposed for square microchannels with various aspect ratios. The dimensionless relationship could be widely applied to the reliable design of various microfluidic devices dealing with multiphase laminar flow

Identifying Some Risk Factors for the Time to Death of the Elderly Using the Semi-Parametric Blended Model of Survival Analysis With Competing Risks

Directory of Open Access Journals (Sweden)

Samane Hajiabbasi

2018-01-01

Conclusion In single-variable fitting, age, history of myocardial infarction, history of stroke, and kidney problems were identified to have significant effects on the time to death of the elderly. Based on one-variable semi-parametric competing risk mixture fitted models, more significant risk factors for the time to death of elderly was identified when compared with a fitted multivariate mode to the data. This implies that the role of some independent variables can be explained by other independent variables.

Predictive densities for day-ahead electricity prices using time-adaptive quantile regression

DEFF Research Database (Denmark)

Jónsson, Tryggvi; Pinson, Pierre; Madsen, Henrik

2014-01-01

A large part of the decision-making problems actors of the power system are facing on a daily basis requires scenarios for day-ahead electricity market prices. These scenarios are most likely to be generated based on marginal predictive densities for such prices, then enhanced with a temporal...... dependence structure. A semi-parametric methodology for generating such densities is presented: it includes: (i) a time-adaptive quantile regression model for the 5%–95% quantiles; and (ii) a description of the distribution tails with exponential distributions. The forecasting skill of the proposed model...

Modelling biochemical networks with intrinsic time delays: a hybrid semi-parametric approach

Directory of Open Access Journals (Sweden)

Oliveira Rui

2010-09-01

Full Text Available Abstract Background This paper presents a method for modelling dynamical biochemical networks with intrinsic time delays. Since the fundamental mechanisms leading to such delays are many times unknown, non conventional modelling approaches become necessary. Herein, a hybrid semi-parametric identification methodology is proposed in which discrete time series are incorporated into fundamental material balance models. This integration results in hybrid delay differential equations which can be applied to identify unknown cellular dynamics. Results The proposed hybrid modelling methodology was evaluated using two case studies. The first of these deals with dynamic modelling of transcriptional factor A in mammalian cells. The protein transport from the cytosol to the nucleus introduced a delay that was accounted for by discrete time series formulation. The second case study focused on a simple network with distributed time delays that demonstrated that the discrete time delay formalism has broad applicability to both discrete and distributed delay problems. Conclusions Significantly better prediction qualities of the novel hybrid model were obtained when compared to dynamical structures without time delays, being the more distinctive the more significant the underlying system delay is. The identification of the system delays by studies of different discrete modelling delays was enabled by the proposed structure. Further, it was shown that the hybrid discrete delay methodology is not limited to discrete delay systems. The proposed method is a powerful tool to identify time delays in ill-defined biochemical networks.

On the radiation emitted by a particle falling into a black hole in the semi-relativistic approximation

International Nuclear Information System (INIS)

Coretti, C.; Ferrari, V.

1986-01-01

In this paper the limits of applicability of the semi-relativistic approximation for estimating the radiation emitted in processes of capture of particles by black holes are discussed. It is shown that it gives reliable estimates in the case of spherically symmetric black holes, but it fails in the case of rotating black holes

Dissipative particle dynamics: Systematic parametrization using water-octanol partition coefficients

Science.gov (United States)

Anderson, Richard L.; Bray, David J.; Ferrante, Andrea S.; Noro, Massimo G.; Stott, Ian P.; Warren, Patrick B.

2017-09-01

We present a systematic, top-down, thermodynamic parametrization scheme for dissipative particle dynamics (DPD) using water-octanol partition coefficients, supplemented by water-octanol phase equilibria and pure liquid phase density data. We demonstrate the feasibility of computing the required partition coefficients in DPD using brute-force simulation, within an adaptive semi-automatic staged optimization scheme. We test the methodology by fitting to experimental partition coefficient data for twenty one small molecules in five classes comprising alcohols and poly-alcohols, amines, ethers and simple aromatics, and alkanes (i.e., hexane). Finally, we illustrate the transferability of a subset of the determined parameters by calculating the critical micelle concentrations and mean aggregation numbers of selected alkyl ethoxylate surfactants, in good agreement with reported experimental values.

Nuclear ``pasta'' phase within density dependent hadronic models

Science.gov (United States)

Avancini, S. S.; Brito, L.; Marinelli, J. R.; Menezes, D. P.; de Moraes, M. M. W.; Providência, C.; Santos, A. M.

2009-03-01

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

Nuclear 'pasta' phase within density dependent hadronic models

International Nuclear Information System (INIS)

Avancini, S. S.; Marinelli, J. R.; Menezes, D. P.; Moraes, M. M. W. de; Brito, L.; Providencia, C.; Santos, A. M.

2009-01-01

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

Relativistic time-dependent local-density approximation theory and applications to atomic physics

International Nuclear Information System (INIS)

Parpia, F.Z.

1984-01-01

A time-dependent linear-response theory appropriate to the relativistic local-density approximation (RLDA) to quantum electrodynamics (QED) is developed. The resulting theory, the relativistic time-dependent local-density approximation (RTDLDA) is specialized to the treatment of electric excitations in closed-shell atoms. This formalism is applied to the calculation of atomic photoionization parameters in the dipole approximation. The static-field limit of the RTDLDA is applied to the calculation of dipole polarizabilities. Extensive numerical calculations of the photoionization parameters for the rare gases neon, argon, krypton, and xenon, and for mercury from the RTDLDA are presented and compared in detail with the results of other theories, in particular the relativistic random-phase approximation (RRPA), and with experimental measurements. The predictions of the RTDLDA are comparable with the RRPA calculations made to date. This is remarkable in that the RTDLDA entails appreciably less computational effort. Finally, the dipole polarizabilities predicted by the static-field RTDLDA are compared with other determinations of these quantities. In view of its simplicity, the static-field RTDLDA demonstrates itself to be one of the most powerful theories available for the calculation of dipole polarizabilities

Many-body perturbation theory using the density-functional concept: beyond the GW approximation.

Science.gov (United States)

Bruneval, Fabien; Sottile, Francesco; Olevano, Valerio; Del Sole, Rodolfo; Reining, Lucia

2005-05-13

We propose an alternative formulation of many-body perturbation theory that uses the density-functional concept. Instead of the usual four-point integral equation for the polarizability, we obtain a two-point one, which leads to excellent optical absorption and energy-loss spectra. The corresponding three-point vertex function and self-energy are then simply calculated via an integration, for any level of approximation. Moreover, we show the direct impact of this formulation on the time-dependent density-functional theory. Numerical results for the band gap of bulk silicon and solid argon illustrate corrections beyond the GW approximation for the self-energy.

REIONIZATION ON LARGE SCALES. I. A PARAMETRIC MODEL CONSTRUCTED FROM RADIATION-HYDRODYNAMIC SIMULATIONS

International Nuclear Information System (INIS)

Battaglia, N.; Trac, H.; Cen, R.; Loeb, A.

2013-01-01

We present a new method for modeling inhomogeneous cosmic reionization on large scales. Utilizing high-resolution radiation-hydrodynamic simulations with 2048 3 dark matter particles, 2048 3 gas cells, and 17 billion adaptive rays in a L = 100 Mpc h –1 box, we show that the density and reionization redshift fields are highly correlated on large scales (∼> 1 Mpc h –1 ). This correlation can be statistically represented by a scale-dependent linear bias. We construct a parametric function for the bias, which is then used to filter any large-scale density field to derive the corresponding spatially varying reionization redshift field. The parametric model has three free parameters that can be reduced to one free parameter when we fit the two bias parameters to simulation results. We can differentiate degenerate combinations of the bias parameters by combining results for the global ionization histories and correlation length between ionized regions. Unlike previous semi-analytic models, the evolution of the reionization redshift field in our model is directly compared cell by cell against simulations and performs well in all tests. Our model maps the high-resolution, intermediate-volume radiation-hydrodynamic simulations onto lower-resolution, larger-volume N-body simulations (∼> 2 Gpc h –1 ) in order to make mock observations and theoretical predictions

Approximate solution of the Saha equation - temperature as an explicit function of particle densities

International Nuclear Information System (INIS)

Sato, M.

1991-01-01

The Saha equation for a plasma in thermodynamic equilibrium (TE) is approximately solved to give the temperature as an explicit function of population densities. It is shown that the derived expressions for the Saha temperature are valid approximations to the exact solution. An application of the approximate temperature to the calculation of TE plasma parameters is also described. (orig.)

Low default credit scoring using two-class non-parametric kernel density estimation

CSIR Research Space (South Africa)

Rademeyer, E

2016-12-01

Full Text Available This paper investigates the performance of two-class classification credit scoring data sets with low default ratios. The standard two-class parametric Gaussian and non-parametric Parzen classifiers are extended, using Bayes’ rule, to include either...

Parametric plasma surface instabilities with s-polarized radiation

International Nuclear Information System (INIS)

Rappaport, H.L.

1994-01-01

The authors argue that parametric plasma surface mode excitation is a viable broadband instability mechanism in the microwave regime since the wavelength of incident radiation ca be large compared to plasma ion density gradient scale lengths. They restrict their attention to plasmas which are uniform in the planes perpendicular to the density gradients. The boundary is characterized by three parameters: (1) the ion density gradient scale length, (2) the electron Debye length, and (3) the excursion of boundary electrons as they move in response to monochromatic radiation. For s-polarized radiation, equilibrium fluid motion is parallel to the boundary when the ratio of the pump quiver velocity to the speed of light is small. In this case, an abruptly bounded plasma may be modeled with no transition width. If in this case the cold fluid approximation is used as well, the specular and diffuse boundary approximations become the same. A new formation is presented in which pump induced perturbations are expressed as an explicit superposition of linear and non-linear plasma half-space modes. A four-wave interaction is found to produce instability as well as surface wave frequency-shift. This mode is compared against other modes known to exist in this geometry. The theory of surface wave linear mode conversion is reviewed with special attention paid to power flow and energy conservation in this system

Absolute decay parametric instability of high-temperature plasma

International Nuclear Information System (INIS)

Zozulya, A.A.; Silin, V.P.; Tikhonchuk, V.T.

1986-01-01

A new absolute decay parametric instability having wide spatial localization region is shown to be possible near critical plasma density. Its excitation is conditioned by distributed feedback of counter-running Langmuir waves occurring during parametric decay of incident and reflected pumping wave components. In a hot plasma with the temperature of the order of kiloelectronvolt its threshold is lower than that of a known convective decay parametric instability. Minimum absolute instability threshold is shown to be realized under conditions of spatial parametric resonance of higher orders

Markovian Dynamics of Josephson Parametric Amplification

Directory of Open Access Journals (Sweden)

W. Kaiser

2017-09-01

Full Text Available In this work, we derive the dynamics of the lossy DC pumped non-degenerate Josephson parametric amplifier (DCPJPA. The main element in a DCPJPA is the superconducting Josephson junction. The DC bias generates the AC Josephson current varying the nonlinear inductance of the junction. By this way the Josephson junction acts as the pump oscillator as well as the time varying reactance of the parametric amplifier. In quantum-limited amplification, losses and noise have an increased impact on the characteristics of an amplifier. We outline the classical model of the lossy DCPJPA and derive the available noise power spectral densities. A classical treatment is not capable of including properties like spontaneous emission which is mandatory in case of amplification at the quantum limit. Thus, we derive a quantum mechanical model of the lossy DCPJPA. Thermal losses are modeled by the quantum Langevin approach, by coupling the quantized system to a photon heat bath in thermodynamic equilibrium. The mode occupation in the bath follows the Bose-Einstein statistics. Based on the second quantization formalism, we derive the Heisenberg equations of motion of both resonator modes. We assume the dynamics of the system to follow the Markovian approximation, i.e. the system only depends on its actual state and is memory-free. We explicitly compute the time evolution of the contributions to the signal mode energy and give numeric examples based on different damping and coupling constants. Our analytic results show, that this model is capable of including thermal noise into the description of the DC pumped non-degenerate Josephson parametric amplifier.

Markovian Dynamics of Josephson Parametric Amplification

Science.gov (United States)

Kaiser, Waldemar; Haider, Michael; Russer, Johannes A.; Russer, Peter; Jirauschek, Christian

2017-09-01

In this work, we derive the dynamics of the lossy DC pumped non-degenerate Josephson parametric amplifier (DCPJPA). The main element in a DCPJPA is the superconducting Josephson junction. The DC bias generates the AC Josephson current varying the nonlinear inductance of the junction. By this way the Josephson junction acts as the pump oscillator as well as the time varying reactance of the parametric amplifier. In quantum-limited amplification, losses and noise have an increased impact on the characteristics of an amplifier. We outline the classical model of the lossy DCPJPA and derive the available noise power spectral densities. A classical treatment is not capable of including properties like spontaneous emission which is mandatory in case of amplification at the quantum limit. Thus, we derive a quantum mechanical model of the lossy DCPJPA. Thermal losses are modeled by the quantum Langevin approach, by coupling the quantized system to a photon heat bath in thermodynamic equilibrium. The mode occupation in the bath follows the Bose-Einstein statistics. Based on the second quantization formalism, we derive the Heisenberg equations of motion of both resonator modes. We assume the dynamics of the system to follow the Markovian approximation, i.e. the system only depends on its actual state and is memory-free. We explicitly compute the time evolution of the contributions to the signal mode energy and give numeric examples based on different damping and coupling constants. Our analytic results show, that this model is capable of including thermal noise into the description of the DC pumped non-degenerate Josephson parametric amplifier.

Calculation of photon attenuation coefficients of elements and compounds from approximate semi-analytical formulae

Energy Technology Data Exchange (ETDEWEB)

Roteta, M; Baro, J; Fernandez-Varea, J M; Salvat, F

1994-07-01

The FORTRAN 77 code PHOTAC to compute photon attenuation coefficients of elements and compounds is described. The code is based on the semi analytical approximate atomic cross sections proposed by Baro et al. (1994). Photoelectric cross sections for coherent and incoherent scattering and for pair production are obtained as integrals of the corresponding differential cross sections. These integrals are evaluated, to a pre-selected accuracy, by using a 20-point Gauss adaptive integration algorithm. Calculated attenuation coefficients agree with recently compiled databases to within - 1%, in the energy range from 1 keV to 1 GeV. The complete source listing of the program PHOTAC is included. (Author) 14 refs.

Calculation of photon attenuation coefficients of elements and compounds from approximate semi-analytical formulae

International Nuclear Information System (INIS)

Roteta, M.; Baro, J.; Fernandez-Varea, J. M.; Salvat, F.

1994-01-01

The FORTRAN 77 code PHOTAC to compute photon attenuation coefficients of elements and compounds is described. The code is based on the semi analytical approximate atomic cross sections proposed by Baro et al. (1994). Photoelectric cross sections for coherent and incoherent scattering and for pair production are obtained as integrals of the corresponding differential cross sections. These integrals are evaluated, to a pre-selected accuracy, by using a 20-point Gauss adaptive integration algorithm. Calculated attenuation coefficients agree with recently compiled databases to within - 1%, in the energy range from 1 keV to 1 GeV. The complete source listing of the program PHOTAC is included. (Author) 14 refs

Combination of Wavefunction and Density Functional Approximations for Describing Electronic Correlation

Science.gov (United States)

Garza, Alejandro J.

Perhaps the most important approximations to the electronic structure problem in quantum chemistry are those based on coupled cluster and density functional theories. Coupled cluster theory has been called the ``gold standard'' of quantum chemistry due to the high accuracy that it achieves for weakly correlated systems. Kohn-Sham density functionals based on semilocal approximations are, without a doubt, the most widely used methods in chemistry and material science because of their high accuracy/cost ratio. The root of the success of coupled cluster and density functionals is their ability to efficiently describe the dynamic part of the electron correlation. However, both traditional coupled cluster and density functional approximations may fail catastrophically when substantial static correlation is present. This severely limits the applicability of these methods to a plethora of important chemical and physical problems such as, e.g., the description of bond breaking, transition states, transition metal-, lanthanide- and actinide-containing compounds, and superconductivity. In an attempt to tackle this problem, nonstandard (single-reference) coupled cluster-based techniques that aim to describe static correlation have been recently developed: pair coupled cluster doubles (pCCD) and singlet-paired coupled cluster doubles (CCD0). The ability to describe static correlation in pCCD and CCD0 comes, however, at the expense of important amounts of dynamic correlation so that the high accuracy of standard coupled cluster becomes unattainable. Thus, the reliable and efficient description of static and dynamic correlation in a simultaneous manner remains an open problem for quantum chemistry and many-body theory in general. In this thesis, different ways to combine pCCD and CCD0 with density functionals in order to describe static and dynamic correlation simultaneously (and efficiently) are explored. The combination of wavefunction and density functional methods has a long

Electron momentum density and Compton profile by a semi-empirical approach

Science.gov (United States)

Aguiar, Julio C.; Mitnik, Darío; Di Rocco, Héctor O.

2015-08-01

Here we propose a semi-empirical approach to describe with good accuracy the electron momentum densities and Compton profiles for a wide range of pure crystalline metals. In the present approach, we use an experimental Compton profile to fit an analytical expression for the momentum densities of the valence electrons. This expression is similar to a Fermi-Dirac distribution function with two parameters, one of which coincides with the ground state kinetic energy of the free-electron gas and the other resembles the electron-electron interaction energy. In the proposed scheme conduction electrons are neither completely free nor completely bound to the atomic nucleus. This procedure allows us to include correlation effects. We tested the approach for all metals with Z=3-50 and showed the results for three representative elements: Li, Be and Al from high-resolution experiments.

Parametric nanomechanical amplification at very high frequency.

Science.gov (United States)

Karabalin, R B; Feng, X L; Roukes, M L

2009-09-01

Parametric resonance and amplification are important in both fundamental physics and technological applications. Here we report very high frequency (VHF) parametric resonators and mechanical-domain amplifiers based on nanoelectromechanical systems (NEMS). Compound mechanical nanostructures patterned by multilayer, top-down nanofabrication are read out by a novel scheme that parametrically modulates longitudinal stress in doubly clamped beam NEMS resonators. Parametric pumping and signal amplification are demonstrated for VHF resonators up to approximately 130 MHz and provide useful enhancement of both resonance signal amplitude and quality factor. We find that Joule heating and reduced thermal conductance in these nanostructures ultimately impose an upper limit to device performance. We develop a theoretical model to account for both the parametric response and nonequilibrium thermal transport in these composite nanostructures. The results closely conform to our experimental observations, elucidate the frequency and threshold-voltage scaling in parametric VHF NEMS resonators and sensors, and establish the ultimate sensitivity limits of this approach.

Site-occupation embedding theory using Bethe ansatz local density approximations

Science.gov (United States)

Senjean, Bruno; Nakatani, Naoki; Tsuchiizu, Masahisa; Fromager, Emmanuel

2018-06-01

Site-occupation embedding theory (SOET) is an alternative formulation of density functional theory (DFT) for model Hamiltonians where the fully interacting Hubbard problem is mapped, in principle exactly, onto an impurity-interacting (rather than a noninteracting) one. It provides a rigorous framework for combining wave-function (or Green function)-based methods with DFT. In this work, exact expressions for the per-site energy and double occupation of the uniform Hubbard model are derived in the context of SOET. As readily seen from these derivations, the so-called bath contribution to the per-site correlation energy is, in addition to the latter, the key density functional quantity to model in SOET. Various approximations based on Bethe ansatz and perturbative solutions to the Hubbard and single-impurity Anderson models are constructed and tested on a one-dimensional ring. The self-consistent calculation of the embedded impurity wave function has been performed with the density-matrix renormalization group method. It has been shown that promising results are obtained in specific regimes of correlation and density. Possible further developments have been proposed in order to provide reliable embedding functionals and potentials.

Empirical Bayes Estimation of Semi-parametric Hierarchical Mixture Models for Unbiased Characterization of Polygenic Disease Architectures

Directory of Open Access Journals (Sweden)

Jo Nishino

2018-04-01

Full Text Available Genome-wide association studies (GWAS suggest that the genetic architecture of complex diseases consists of unexpectedly numerous variants with small effect sizes. However, the polygenic architectures of many diseases have not been well characterized due to lack of simple and fast methods for unbiased estimation of the underlying proportion of disease-associated variants and their effect-size distribution. Applying empirical Bayes estimation of semi-parametric hierarchical mixture models to GWAS summary statistics, we confirmed that schizophrenia was extremely polygenic [~40% of independent genome-wide SNPs are risk variants, most within odds ratio (OR = 1.03], whereas rheumatoid arthritis was less polygenic (~4 to 8% risk variants, significant portion reaching OR = 1.05 to 1.1. For rheumatoid arthritis, stratified estimations revealed that expression quantitative loci in blood explained large genetic variance, and low- and high-frequency derived alleles were prone to be risk and protective, respectively, suggesting a predominance of deleterious-risk and advantageous-protective mutations. Despite genetic correlation, effect-size distributions for schizophrenia and bipolar disorder differed across allele frequency. These analyses distinguished disease polygenic architectures and provided clues for etiological differences in complex diseases.

Quantum and Raman Noise in a Depleted Fiber Optical Parametric Amplifier

DEFF Research Database (Denmark)

Friis, Søren Michael Mørk; Rottwitt, Karsten; McKinstrie, Colin J.

2013-01-01

The noise properties of both phase-sensitive and phase-insensitive saturated parametric amplifiers are studied using a semi-classical approach. Vacuum fluctuations as well as spontaneous Raman scattering are included in the analysis....

Calculation of photon attenuation coefficients of elements and compounds from approximate semi-analytical formulae

International Nuclear Information System (INIS)

Roteta, M.; Baro, J.; Fernandez-Varea, J.M.; Salvat, F.

1994-01-01

The FORTRAN 77 code PHOTAC to compute photon attenuation coefficients of elements and compounds is described. The code is based on the semi-analytical approximate atomic cross sections proposed by Baro et al. (1994). Photoelectric cross sections are calculated directly from a simple analytical expression. Atomic cross sections for coherent and incoherent scattering and for pair production are obtained as integrals of the corresponding differential cross sections. These integrals are evaluated, to a pre-selected accuracy, by using a 20-point Gauss adaptive integration algorithm. Calculated attenuation coefficients agree with recently compiled databases to within equal 1%, in the energy range from 1 KeV to 1 GeV. The complete source listing of the program PHOTAC is included

Local density approximation for a perturbative equation of state

International Nuclear Information System (INIS)

Astrakharchik, G. E.

2005-01-01

Knowledge of a series expansion of the equation of state provides a deep insight into the physical nature of a quantum system. Starting from a generic 'perturbative' equation of state of a homogeneous ultracold gas we make predictions for the properties of the gas in the presence of harmonic confinement. The local density approximation is used to obtain the chemical potential, total and release energies, Thomas-Fermi size, and density profile of a trapped system in three-, two-, and one-dimensional geometries. The frequencies of the lowest breathing modes are calculated using scaling and sum-rule approaches and could be used in an experiment as a high-precision tool for obtaining the expansion terms of the equation of state. The derived formalism is applied to dilute Bose and Fermi gases in different dimensions and to integrable one-dimensional models. The physical meaning of the expansion terms in a number of systems is discussed

SU-G-JeP2-02: A Unifying Multi-Atlas Approach to Electron Density Mapping Using Multi-Parametric MRI for Radiation Treatment Planning

Energy Technology Data Exchange (ETDEWEB)

Ren, S [Stanford University, Stanford, CA (United States); Tianjin University, Tianjin (China); Hara, W; Le, Q; Wang, L; Xing, L; Li, R [Stanford University, Stanford, CA (United States)

2016-06-15

Purpose: MRI has a number of advantages over CT as a primary modality for radiation treatment planning (RTP). However, one key bottleneck problem still remains, which is the lack of electron density information in MRI. In the work, a reliable method to map electron density is developed by leveraging the differential contrast of multi-parametric MRI. Methods: We propose a probabilistic Bayesian approach for electron density mapping based on T1 and T2-weighted MRI, using multiple patients as atlases. For each voxel, we compute two conditional probabilities: (1) electron density given its image intensity on T1 and T2-weighted MR images, and (2) electron density given its geometric location in a reference anatomy. The two sources of information (image intensity and spatial location) are combined into a unifying posterior probability density function using the Bayesian formalism. The mean value of the posterior probability density function provides the estimated electron density. Results: We evaluated the method on 10 head and neck patients and performed leave-one-out cross validation (9 patients as atlases and remaining 1 as test). The proposed method significantly reduced the errors in electron density estimation, with a mean absolute HU error of 138, compared with 193 for the T1-weighted intensity approach and 261 without density correction. For bone detection (HU>200), the proposed method had an accuracy of 84% and a sensitivity of 73% at specificity of 90% (AUC = 87%). In comparison, the AUC for bone detection is 73% and 50% using the intensity approach and without density correction, respectively. Conclusion: The proposed unifying method provides accurate electron density estimation and bone detection based on multi-parametric MRI of the head with highly heterogeneous anatomy. This could allow for accurate dose calculation and reference image generation for patient setup in MRI-based radiation treatment planning.

SU-G-JeP2-02: A Unifying Multi-Atlas Approach to Electron Density Mapping Using Multi-Parametric MRI for Radiation Treatment Planning

International Nuclear Information System (INIS)

Ren, S; Hara, W; Le, Q; Wang, L; Xing, L; Li, R

2016-01-01

Purpose: MRI has a number of advantages over CT as a primary modality for radiation treatment planning (RTP). However, one key bottleneck problem still remains, which is the lack of electron density information in MRI. In the work, a reliable method to map electron density is developed by leveraging the differential contrast of multi-parametric MRI. Methods: We propose a probabilistic Bayesian approach for electron density mapping based on T1 and T2-weighted MRI, using multiple patients as atlases. For each voxel, we compute two conditional probabilities: (1) electron density given its image intensity on T1 and T2-weighted MR images, and (2) electron density given its geometric location in a reference anatomy. The two sources of information (image intensity and spatial location) are combined into a unifying posterior probability density function using the Bayesian formalism. The mean value of the posterior probability density function provides the estimated electron density. Results: We evaluated the method on 10 head and neck patients and performed leave-one-out cross validation (9 patients as atlases and remaining 1 as test). The proposed method significantly reduced the errors in electron density estimation, with a mean absolute HU error of 138, compared with 193 for the T1-weighted intensity approach and 261 without density correction. For bone detection (HU>200), the proposed method had an accuracy of 84% and a sensitivity of 73% at specificity of 90% (AUC = 87%). In comparison, the AUC for bone detection is 73% and 50% using the intensity approach and without density correction, respectively. Conclusion: The proposed unifying method provides accurate electron density estimation and bone detection based on multi-parametric MRI of the head with highly heterogeneous anatomy. This could allow for accurate dose calculation and reference image generation for patient setup in MRI-based radiation treatment planning.

Noise-enhanced Parametric Resonance in Perturbed Galaxies

Science.gov (United States)

Sideris, Ioannis V.; Kandrup, Henry E.

2004-02-01

This paper describes how parametric resonances associated with a galactic potential subjected to relatively low-amplitude, strictly periodic time-dependent perturbations can be impacted by pseudo-random variations in the pulsation frequency, modeled as colored noise. One aim thereby is to allow for the effects of a changing oscillation frequency as the density distribution associated with a galaxy evolves during violent relaxation. Another is to mimic the possible effects of internal substructures, satellite galaxies, and/or a high-density environment. The principal conclusions are that allowing for a variable frequency does not vitiate the effects of parametric resonance, and that, in at least some cases, such variations can increase the overall importance of parametric resonance associated with systematic pulsations. In memory of Professor H. E. Kandrup, a brilliant scientist, excellent teacher, and good friend. His genius and sense of humor will be greatly missed.

Asymmetric battery having a semi-solid cathode and high energy density anode

Energy Technology Data Exchange (ETDEWEB)

Tan, Taison; Chiang, Yet-Ming; Ota, Naoki; Wilder, Throop; Duduta, Mihai

2017-11-28

Embodiments described herein relate generally to devices, systems and methods of producing high energy density batteries having a semi-solid cathode that is thicker than the anode. An electrochemical cell can include a positive electrode current collector, a negative electrode current collector and an ion-permeable membrane disposed between the positive electrode current collector and the negative electrode current collector. The ion-permeable membrane is spaced a first distance from the positive electrode current collector and at least partially defines a positive electroactive zone. The ion-permeable membrane is spaced a second distance from the negative electrode current collector and at least partially defines a negative electroactive zone. The second distance is less than the first distance. A semi-solid cathode that includes a suspension of an active material and a conductive material in a non-aqueous liquid electrolyte is disposed in the positive electroactive zone, and an anode is disposed in the negative electroactive zone.

Observational Signatures of Parametric Instability at 1AU

Science.gov (United States)

Bowen, T. A.; Bale, S. D.; Badman, S.

2017-12-01

Observations and simulations of inertial compressive turbulence in the solar wind are characterized by density structures anti-correlated with magnetic fluctuations parallel to the mean field. This signature has been interpreted as observational evidence for non-propagating pressure balanced structures (PBS), kinetic ion acoustic waves, as well as the MHD slow mode. Recent work, specifically Verscharen et al. (2017), has highlighted the unexpected fluid like nature of the solar wind. Given the high damping rates of parallel propagating compressive fluctuations, their ubiquity in satellite observations is surprising and suggests the presence of a driving process. One possible candidate for the generation of compressive fluctuations in the solar wind is the parametric instability, in which large amplitude Alfvenic fluctuations decay into parallel propagating compressive waves. This work employs 10 years of WIND observations in order to test the parametric decay process as a source of compressive waves in the solar wind through comparing collisionless damping rates of compressive fluctuations with growth rates of the parametric instability. Preliminary results suggest that generation of compressive waves through parametric decay is overdamped at 1 AU. However, the higher parametric decay rates expected in the inner heliosphere likely allow for growth of the slow mode-the remnants of which could explain density fluctuations observed at 1AU.

Some remarks on off-shell scattering in the eikonal approximation and applications to semi-inclusive reactions

International Nuclear Information System (INIS)

Rinat, A.S.; Taragin, M.F.

1997-01-01

Using the Abel inversion for the eikonal phase as function of the interaction we derive simple integral relations between half and on-shell eikonal phases. A frequently used short-range approximation for the half off-shell phase and profile appears supported by the above-mentioned relation. We work out some examples and also address the half off-shell eikonal phase pertinent to a diffractive amplitude. The latter is relevant for a calculation of selected transparencies T of nuclei for a proton, knocked-out in selected semi-inclusive A(e,e'p)X reactions. Some numerical results for T are given. (orig.)

Intermolecular interaction potentials of the methane dimer from the local density approximation

International Nuclear Information System (INIS)

Chen Xiangrong; Bai Yulin; Zhu Jun; Yang Xiangdong

2004-01-01

The intermolecular interaction potentials of methane (CH 4 ) dimer are calculated within the density functional theory in the local density approximation (LDA). It is found that the calculated potentials have minima when the intermolecular distance of CH 4 dimer is about 7.0 a.u., which is in good agreement with the experiment. The depth of the potential is 0.017 eV. The results obtained by our LDA calculations seem to agree well with those obtained by MP2, MP3, and CCSD from the Moeller-Plesset and coupled cluster methods by Tsuzuki et al. and with the experimental data

High frequency parametric wave phenomena and plasma heating: a review

International Nuclear Information System (INIS)

Porkolab, M.

1975-11-01

A survey of parametric instabilities in plasma, and associated particle heating, is presented. A brief summary of linear theory is given. The physical mechanism of decay instability, the purely growing mode (oscillating two-stream instability) and soliton and density cavity formation is presented. Effects of density gradients are discussed. Possible nonlinear saturation mechanisms are pointed out. Experimental evidence for the existence of parametric instabilities in both unmagnetized and magnetized plasmas is reviewed in some detail. Experimental observation of plasma heating associated with the presence of parametric instabilities is demonstrated by a number of examples. Possible application of these phenomena to heating of pellets by lasers and heating of magnetically confined fusion plasmas by high power microwave sources is discussed

Current-driven parametric resonance in magnetic multilayers

International Nuclear Information System (INIS)

Wang, C; Seinige, H; Tsoi, M

2013-01-01

Current-induced parametric excitations were observed in point-contact spin-valve nanodevices. Point contacts were used to inject high densities of direct and microwave currents into spin valves, thus producing oscillating spin-transfer and Oersted-field torques on magnetic moments. The resulting magnetodynamics were observed electrically by measuring rectified voltage signals across the contact. In addition to the spin-torque-driven ferromagnetic resonance we observe doubled-frequency signals which correspond to the parametric excitation of magnetic moments. Numerical simulations suggest that while both spin-transfer torque and ac Oersted field contribute to the parametrically excited dynamics, the ac spin torque dominates, and dc spin torque can switch it on and off. The dc bias dependence of the parametric resonance signal enabled the mapping of instability regions characterizing the nonlinearity of the oscillation. (paper)

Parametrization of the increase of the aeolian erosion threshold wind friction velocity due to soil moisture for arid and semi-arid areas

Directory of Open Access Journals (Sweden)

F. Fécan

1999-01-01

Full Text Available Large-scale simulation of the soil-derived dust emission in semi-arid regions needs to account for the influence of the soil moisture on the wind erosion threshold. Soil water retention consists of molecular adsorption on the soil grain surface and capillary forces between the grain. Interparticle capillary forces (characterized by the moisture tension are the main factor responsible for the increase of the wind erosion threshold observed when the soil moisture increases. When the soil moisture content is close to but smaller than the maximum amount of adsorbed water, w' (depending on the soil texture, these capillary forces are considered as not strong enough to significantly increase the erosion threshold. An expression of the moisture tension as a function of soil moisture and w' is derived from retention curves. From this expression, a parametrization of the ratio of the wet to dry erosion thresholds has been developed as a function of soil moisture and soil texture. The coefficients of this parametrization have been determined by using experimental data from the literature. An empirical relationship between w' and soil clay content has been established. The erosion threshold ratios simulated for different soil textures were found to be in good agreement with the experimental data.Key words. Atmospheric composition and structure (Aerosols and particles · Hydrology (soil moisture

Measurements of the parametric decay of CO2 laser radiation into plasma waves at quarter critical density using ruby laser Thomson scattering

International Nuclear Information System (INIS)

Schuss, J.J.; Chu, T.K.; Johnson, L.C.

1977-11-01

We report the results of small-angle ruby laser Thomson scattering measurements of the parametric excitation of plasma waves by CO 2 laser radiation at quarter-critical density in a laser-heated gas target plasma. From supplementary data obtained from interferometry and large-angle ruby laser scattering we infer that the threshold conditions for a convective decay are satisfied

A simple semi-empirical approximation for bond energy

International Nuclear Information System (INIS)

Jorge, F.E.; Giambiagi, M.; Giambiagi, M.S. de.

1985-01-01

A simple semi-empirical expression for bond energy, related with a generalized bond index, is proposed and applied within the IEH framework. The correlation with experimental data is good for the intermolecular bond energy of base pairs of nucleic acids and other hydrogen bonded systems. The intramolecular bond energies for a sample of molecules containing typical bonds and for hydrides are discussed. The results are compared with those obtained by other methods. (Author) [pt

Efficient Characterization of Parametric Uncertainty of Complex (Biochemical Networks.

Directory of Open Access Journals (Sweden)

Claudia Schillings

2015-08-01

Full Text Available Parametric uncertainty is a particularly challenging and relevant aspect of systems analysis in domains such as systems biology where, both for inference and for assessing prediction uncertainties, it is essential to characterize the system behavior globally in the parameter space. However, current methods based on local approximations or on Monte-Carlo sampling cope only insufficiently with high-dimensional parameter spaces associated with complex network models. Here, we propose an alternative deterministic methodology that relies on sparse polynomial approximations. We propose a deterministic computational interpolation scheme which identifies most significant expansion coefficients adaptively. We present its performance in kinetic model equations from computational systems biology with several hundred parameters and state variables, leading to numerical approximations of the parametric solution on the entire parameter space. The scheme is based on adaptive Smolyak interpolation of the parametric solution at judiciously and adaptively chosen points in parameter space. As Monte-Carlo sampling, it is "non-intrusive" and well-suited for massively parallel implementation, but affords higher convergence rates. This opens up new avenues for large-scale dynamic network analysis by enabling scaling for many applications, including parameter estimation, uncertainty quantification, and systems design.

Parametric excitation of drift waves in a sheared slab geometry

International Nuclear Information System (INIS)

Vranjes, J.; Weiland, J.

1992-01-01

The threshold for parametric excitation of drift waves in a sheared slab geometry is calculated for a pump wave that is a standing wave along the magnetic field, using the Hasegawa-Mima nonlinearity. The shear damping is counteracted by the parametric coupling and the eigenvalue problem is solved analytically using Taylor's strong coupling approximation. (au)

spa: Semi-Supervised Semi-Parametric Graph-Based Estimation in R

Directory of Open Access Journals (Sweden)

Mark Culp

2011-04-01

Full Text Available In this paper, we present an R package that combines feature-based (X data and graph-based (G data for prediction of the response Y . In this particular case, Y is observed for a subset of the observations (labeled and missing for the remainder (unlabeled. We examine an approach for fitting Y = Xβ + f(G where β is a coefficient vector and f is a function over the vertices of the graph. The procedure is semi-supervised in nature (trained on the labeled and unlabeled sets, requiring iterative algorithms for fitting this estimate. The package provides several key functions for fitting and evaluating an estimator of this type. The package is illustrated on a text analysis data set, where the observations are text documents (papers, the response is the category of paper (either applied or theoretical statistics, the X information is the name of the journal in which the paper resides, and the graph is a co-citation network, with each vertex an observation and each edge the number of times that the two papers cite a common paper. An application involving classification of protein location using a protein interaction graph and an application involving classification on a manifold with part of the feature data converted to a graph are also presented.

Extending the random-phase approximation for electronic correlation energies: the renormalized adiabatic local density approximation

DEFF Research Database (Denmark)

Olsen, Thomas; Thygesen, Kristian S.

2012-01-01

The adiabatic connection fluctuation-dissipation theorem with the random phase approximation (RPA) has recently been applied with success to obtain correlation energies of a variety of chemical and solid state systems. The main merit of this approach is the improved description of dispersive forces...... while chemical bond strengths and absolute correlation energies are systematically underestimated. In this work we extend the RPA by including a parameter-free renormalized version of the adiabatic local-density (ALDA) exchange-correlation kernel. The renormalization consists of a (local) truncation...... of the ALDA kernel for wave vectors q > 2kF, which is found to yield excellent results for the homogeneous electron gas. In addition, the kernel significantly improves both the absolute correlation energies and atomization energies of small molecules over RPA and ALDA. The renormalization can...

Fine features of parametric X-ray radiation by relativistic electrons and ions

Directory of Open Access Journals (Sweden)

K.B. Korotchenko

2017-11-01

Full Text Available In present work within the frame of dynamic theory for parametric X-ray radiation in two-beam approximation we have presented detailed studies on parametric radiation emitted by relativistic both electrons and ions at channeling in crystals that is highly requested at planned experiments. The analysis done has shown that the intensity of radiation at relativistic electron channeling in Si (110 with respect to the conventional parametric radiation intensity has up to 5% uncertainty, while the error of approximate formulas for calculating parametric X-ray radiation maxima does not exceed 1.2%. We have demonstrated that simple expressions for the Fourier components of Si crystal susceptibility χ0 and χgσ could be reduced, as well as the temperature dependence for radiation maxima in Si crystal (diffraction plane (110 within Debye model. Moreover, for any types of channeled ions it is shown that the parametric X-ray radiation intensity is proportional to z2−b(Z,z/z with the function b(Z,z depending on the screening parameter and the ion charge number z=Z−Ze.

Raman and loss induced quantum noise in depleted fiber optical parametric amplifiers

DEFF Research Database (Denmark)

Friis, Søren Michael Mørk; Rottwitt, Karsten; McKinstrie, C. J.

2013-01-01

We present a semi-classical approach for predicting the quantum noise properties of fiber optical parametric amplifiers. The unavoidable contributors of noise, vacuum fluctuations, loss-induced noise, and spontaneous Raman scattering, are included in the analysis of both phase-insensitive and phase...

Two-Sample Statistics for Testing the Equality of Survival Functions Against Improper Semi-parametric Accelerated Failure Time Alternatives: An Application to the Analysis of a Breast Cancer Clinical Trial

Science.gov (United States)

BROËT, PHILIPPE; TSODIKOV, ALEXANDER; DE RYCKE, YANN; MOREAU, THIERRY

2010-01-01

This paper presents two-sample statistics suited for testing equality of survival functions against improper semi-parametric accelerated failure time alternatives. These tests are designed for comparing either the short- or the long-term effect of a prognostic factor, or both. These statistics are obtained as partial likelihood score statistics from a time-dependent Cox model. As a consequence, the proposed tests can be very easily implemented using widely available software. A breast cancer clinical trial is presented as an example to demonstrate the utility of the proposed tests. PMID:15293627

Two-sample statistics for testing the equality of survival functions against improper semi-parametric accelerated failure time alternatives: an application to the analysis of a breast cancer clinical trial.

Science.gov (United States)

Broët, Philippe; Tsodikov, Alexander; De Rycke, Yann; Moreau, Thierry

2004-06-01

This paper presents two-sample statistics suited for testing equality of survival functions against improper semi-parametric accelerated failure time alternatives. These tests are designed for comparing either the short- or the long-term effect of a prognostic factor, or both. These statistics are obtained as partial likelihood score statistics from a time-dependent Cox model. As a consequence, the proposed tests can be very easily implemented using widely available software. A breast cancer clinical trial is presented as an example to demonstrate the utility of the proposed tests.

When Density Functional Approximations Meet Iron Oxides.

Science.gov (United States)

Meng, Yu; Liu, Xing-Wu; Huo, Chun-Fang; Guo, Wen-Ping; Cao, Dong-Bo; Peng, Qing; Dearden, Albert; Gonze, Xavier; Yang, Yong; Wang, Jianguo; Jiao, Haijun; Li, Yongwang; Wen, Xiao-Dong

2016-10-11

Three density functional approximations (DFAs), PBE, PBE+U, and Heyd-Scuseria-Ernzerhof screened hybrid functional (HSE), were employed to investigate the geometric, electronic, magnetic, and thermodynamic properties of four iron oxides, namely, α-FeOOH, α-Fe 2 O 3 , Fe 3 O 4 , and FeO. Comparing our calculated results with available experimental data, we found that HSE (a = 0.15) (containing 15% "screened" Hartree-Fock exchange) can provide reliable values of lattice constants, Fe magnetic moments, band gaps, and formation energies of all four iron oxides, while standard HSE (a = 0.25) seriously overestimates the band gaps and formation energies. For PBE+U, a suitable U value can give quite good results for the electronic properties of each iron oxide, but it is challenging to accurately get other properties of the four iron oxides using the same U value. Subsequently, we calculated the Gibbs free energies of transformation reactions among iron oxides using the HSE (a = 0.15) functional and plotted the equilibrium phase diagrams of the iron oxide system under various conditions, which provide reliable theoretical insight into the phase transformations of iron oxides.

Parametric and Non-Parametric System Modelling

DEFF Research Database (Denmark)

Nielsen, Henrik Aalborg

1999-01-01

the focus is on combinations of parametric and non-parametric methods of regression. This combination can be in terms of additive models where e.g. one or more non-parametric term is added to a linear regression model. It can also be in terms of conditional parametric models where the coefficients...... considered. It is shown that adaptive estimation in conditional parametric models can be performed by combining the well known methods of local polynomial regression and recursive least squares with exponential forgetting. The approach used for estimation in conditional parametric models also highlights how...... networks is included. In this paper, neural networks are used for predicting the electricity production of a wind farm. The results are compared with results obtained using an adaptively estimated ARX-model. Finally, two papers on stochastic differential equations are included. In the first paper, among...

A parametric study of dispersion processes in semi-enclosed basins

Energy Technology Data Exchange (ETDEWEB)

Buffoni, G. [ENEA, Centro Ricerche S. Teresa, La Spezia (Italy). Dipt. di Innovazione; Bellucci, A.; Zambianchi, E. [Istituto Universitario Navale, Neapel (Italy); Griffa, A. [Consiglio Nazionale delle Ricerche, La Spezia (Italy)

1999-07-01

The dispersion processes in semi-enclosed basins with stationary flows have been studied by means of an Eulerian advection-diffusion model. Special interest have been given to quantities which characterize the macroscopic state of the system: the normalized total quantity C(t) (C (0) = 1) of a tracer inside the basin, and its residence time T. Also the principal eigenvalue {tau}{sub 0} of the advection-diffusion problem has been considered, since for stationery flows C (t) attains, for time t long enough, an exponential decay shape C{sub 0}exp (-t/{tau}{sub 0} ). The focus is one the comparison between cases where the flow is rotational with re circulations, represented by a flow with a gyre at the outflow. The sensitivity of the results to a number of parameters, including initial and boundary conditions and the eddy diffusivity coefficient, have been studied. It is found that for small Peclet numbers, when the flow is highly diffusive, the results do not depend strongly on the flow structure. {tau}{sub 0} tends to a constant limit (dependent on the boundary conditions) at decreasing Peclet number, and T is approximated by T asymptotically equal to {tau}{sub 0}. For high Peclet numbers, instead, the rotational and irrotational cases are qualitatively different. For rotational flows, {tau}{sub 0}, tends to zero at increasing Peclet number, and T tends toward the advective time scale. For flows with re circulations, in which the tracer tends to be trapped inside the gyre, {tau}{sub 0} increases at increasing Peclet numbers and T asymptotically equal to {tau}{sub 0}, for all initial and boundary conditions. The values of T and {tau}{sub 0} do not change significantly in the range of realistic Peclet numbers considered. This suggests that, for flows with re circulations, the macroscopic dispersion properties depend only weakly on the eddy diffusion coefficient. [Italian] Processi di dispersione in bacini semi-chiusi caratterizzati da flussi stazionari sono stati

Principal component analysis of the CT density histogram to generate parametric response maps of COPD

Science.gov (United States)

Zha, N.; Capaldi, D. P. I.; Pike, D.; McCormack, D. G.; Cunningham, I. A.; Parraga, G.

2015-03-01

Pulmonary x-ray computed tomography (CT) may be used to characterize emphysema and airways disease in patients with chronic obstructive pulmonary disease (COPD). One analysis approach - parametric response mapping (PMR) utilizes registered inspiratory and expiratory CT image volumes and CT-density-histogram thresholds, but there is no consensus regarding the threshold values used, or their clinical meaning. Principal-component-analysis (PCA) of the CT density histogram can be exploited to quantify emphysema using data-driven CT-density-histogram thresholds. Thus, the objective of this proof-of-concept demonstration was to develop a PRM approach using PCA-derived thresholds in COPD patients and ex-smokers without airflow limitation. Methods: Fifteen COPD ex-smokers and 5 normal ex-smokers were evaluated. Thoracic CT images were also acquired at full inspiration and full expiration and these images were non-rigidly co-registered. PCA was performed for the CT density histograms, from which the components with the highest eigenvalues greater than one were summed. Since the values of the principal component curve correlate directly with the variability in the sample, the maximum and minimum points on the curve were used as threshold values for the PCA-adjusted PRM technique. Results: A significant correlation was determined between conventional and PCA-adjusted PRM with 3He MRI apparent diffusion coefficient (p<0.001), with CT RA950 (p<0.0001), as well as with 3He MRI ventilation defect percent, a measurement of both small airways disease (p=0.049 and p=0.06, respectively) and emphysema (p=0.02). Conclusions: PRM generated using PCA thresholds of the CT density histogram showed significant correlations with CT and 3He MRI measurements of emphysema, but not airways disease.

Semi-automatic dimension and density measuring system for UO{sub 2} pellets

Energy Technology Data Exchange (ETDEWEB)

Subramanian, K S; Shyam, P G; Muralidhara Rao, J V; Laxminarayana, B; Suryaprakash, M [Nuclear Fuel Complex, Hyderabad (India)

1994-12-31

The parameters like diameter, length, L/D ratio and sintered density of cylindrical UO{sub 2} pellets are critical in both the PHWR and BWR fuels. A semi-automatic system is developed by interfacing a laser micrometer, a digital electronic balance with a PC-XT and incorporating menu-driven, user-friendly software developed in-house. The advantages are data storage, acquisition, statistical analysis with histograms and print out of acquired and computed values with respective set-up limits along with the production details like lot number, press number, furnace number etc. This paper describes the details of the above system and the software. 3 figs., 2 ills.

Piezoelectric energy harvesting with parametric uncertainty

International Nuclear Information System (INIS)

Ali, S F; Friswell, M I; Adhikari, S

2010-01-01

The design and analysis of energy harvesting devices is becoming increasing important in recent years. Most of the literature has focused on the deterministic analysis of these systems and the problem of uncertain parameters has received less attention. Energy harvesting devices exhibit parametric uncertainty due to errors in measurement, errors in modelling and variability in the parameters during manufacture. This paper investigates the effect of parametric uncertainty in the mechanical system on the harvested power, and derives approximate explicit formulae for the optimal electrical parameters that maximize the mean harvested power. The maximum of the mean harvested power decreases with increasing uncertainty, and the optimal frequency at which the maximum mean power occurs shifts. The effect of the parameter variance on the optimal electrical time constant and optimal coupling coefficient are reported. Monte Carlo based simulation results are used to further analyse the system under parametric uncertainty

Relativistic parametric instabilities in extended extragalactic radio sources

Energy Technology Data Exchange (ETDEWEB)

Ferrari, A [Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica; Trussoni, E; Zaninetti, L

1978-01-01

A general discussion is presented of parametric instabilities of electromagnetic waves in cold plasmas. Previous results for f = eE/msub(e)c..omega../sub 0/ >> 1 and << 1 are extended and the intermediate range f approximately 1, which could be relevant in some astrophysical applications, is analysed by numerical techniques. In the final section a model for particle acceleration and radiation emission by turbulent plasma modes excited in extended radiosources by parametric absorption of strong electromagnetic waves is tentatively discussed.

Correlated random-phase approximation from densities and in-medium matrix elements

Energy Technology Data Exchange (ETDEWEB)

Trippel, Richard; Roth, Robert [Institut fuer Kernphysik, Technische Universitaet Darmstadt (Germany)

2016-07-01

The random-phase approximation (RPA) as well as the second RPA (SRPA) are established tools for the study of collective excitations in nuclei. Addressing the well known lack of correlations, we derived a universal framework for a fully correlated RPA based on the use of one- and two-body densities. We apply densities from coupled cluster theory and investigate the impact of correlations. As an alternative approach to correlations we use matrix elements transformed via in-medium similarity renormalization group (IM-SRG) in combination with RPA and SRPA. We find that within SRPA the use of IM-SRG matrix elements leads to the disappearance of instabilities of low-lying states. For the calculations we use normal-ordered two- plus three-body interactions derived from chiral effective field theory. We apply different Hamiltonians to a number of doubly-magic nuclei and calculate electric transition strengths.

Approximate Implicitization Using Linear Algebra

Directory of Open Access Journals (Sweden)

Oliver J. D. Barrowclough

2012-01-01

Full Text Available We consider a family of algorithms for approximate implicitization of rational parametric curves and surfaces. The main approximation tool in all of the approaches is the singular value decomposition, and they are therefore well suited to floating-point implementation in computer-aided geometric design (CAGD systems. We unify the approaches under the names of commonly known polynomial basis functions and consider various theoretical and practical aspects of the algorithms. We offer new methods for a least squares approach to approximate implicitization using orthogonal polynomials, which tend to be faster and more numerically stable than some existing algorithms. We propose several simple propositions relating the properties of the polynomial bases to their implicit approximation properties.

Efficient Characterization of Parametric Uncertainty of Complex (Bio)chemical Networks.

Science.gov (United States)

Schillings, Claudia; Sunnåker, Mikael; Stelling, Jörg; Schwab, Christoph

2015-08-01

Parametric uncertainty is a particularly challenging and relevant aspect of systems analysis in domains such as systems biology where, both for inference and for assessing prediction uncertainties, it is essential to characterize the system behavior globally in the parameter space. However, current methods based on local approximations or on Monte-Carlo sampling cope only insufficiently with high-dimensional parameter spaces associated with complex network models. Here, we propose an alternative deterministic methodology that relies on sparse polynomial approximations. We propose a deterministic computational interpolation scheme which identifies most significant expansion coefficients adaptively. We present its performance in kinetic model equations from computational systems biology with several hundred parameters and state variables, leading to numerical approximations of the parametric solution on the entire parameter space. The scheme is based on adaptive Smolyak interpolation of the parametric solution at judiciously and adaptively chosen points in parameter space. As Monte-Carlo sampling, it is "non-intrusive" and well-suited for massively parallel implementation, but affords higher convergence rates. This opens up new avenues for large-scale dynamic network analysis by enabling scaling for many applications, including parameter estimation, uncertainty quantification, and systems design.

Mass distribution of fission fragments within the Born-Oppenheimer approximation

Energy Technology Data Exchange (ETDEWEB)

Pomorski, K.; Nerlo-Pomorska, B. [M.C.S. University, Department of Theoretical Physics, Lublin (Poland); Ivanyuk, F.A. [Institute for Nuclear Research, Kiev (Ukraine)

2017-03-15

The fission fragments mass-yield of {sup 236} U is obtained by an approximate solution of the eigenvalue problem of the collective Hamiltonian that describes the dynamics of the fission process whose degrees of freedom are: the fission (elongation), the neck and mass-asymmetry modes. The macroscopic-microscopic method is used to evaluate the potential energy surface. The macroscopic energy part is calculated using the liquid drop model and the microscopic corrections are obtained using a Woods-Saxon single-particle levels. The four-dimensional modified Cassini ovals shape parametrization is used to describe the shape of the fissioning nucleus. The mass tensor is taken within a cranking-type approximation. The final fragment mass distribution is obtained by weighting the adiabatic density distribution in the collective space with the neck-dependent fission probability. The neck degree of freedom is found to play a significant role in determining the final fragment mass distribution. (orig.)

Deorbitalization strategies for meta-generalized-gradient-approximation exchange-correlation functionals

Science.gov (United States)

Mejia-Rodriguez, Daniel; Trickey, S. B.

2017-11-01

We explore the simplification of widely used meta-generalized-gradient approximation (mGGA) exchange-correlation functionals to the Laplacian level of refinement by use of approximate kinetic-energy density functionals (KEDFs). Such deorbitalization is motivated by the prospect of reducing computational cost while recovering a strictly Kohn-Sham local potential framework (rather than the usual generalized Kohn-Sham treatment of mGGAs). A KEDF that has been rather successful in solid simulations proves to be inadequate for deorbitalization, but we produce other forms which, with parametrization to Kohn-Sham results (not experimental data) on a small training set, yield rather good results on standard molecular test sets when used to deorbitalize the meta-GGA made very simple, Tao-Perdew-Staroverov-Scuseria, and strongly constrained and appropriately normed functionals. We also study the difference between high-fidelity and best-performing deorbitalizations and discuss possible implications for use in ab initio molecular dynamics simulations of complicated condensed phase systems.

New parametrization for the scale dependent growth function in general relativity

International Nuclear Information System (INIS)

Dent, James B.; Dutta, Sourish; Perivolaropoulos, Leandros

2009-01-01

We study the scale-dependent evolution of the growth function δ(a,k) of cosmological perturbations in dark energy models based on general relativity. This scale dependence is more prominent on cosmological scales of 100h -1 Mpc or larger. We derive a new scale-dependent parametrization which generalizes the well-known Newtonian approximation result f 0 (a)≡(dlnδ 0 /dlna)=Ω(a) γ (γ=(6/11) for ΛCDM) which is a good approximation on scales less than 50h -1 Mpc. Our generalized parametrization is of the form f(a)=(f 0 (a)/1+ξ(a,k)), where ξ(a,k)=(3H 0 2 Ω 0m )/(ak 2 ). We demonstrate that this parametrization fits the exact result of a full general relativistic evaluation of the growth function up to horizon scales for both ΛCDM and dynamical dark energy. In contrast, the scale independent parametrization does not provide a good fit on scales beyond 5% of the horizon scale (k≅0.01h -1 Mpc).

Interplay between parametric instabilities in fusion - relevant laser plasmas

International Nuclear Information System (INIS)

Huller, St.

2003-01-01

The control of parametric instabilities plays an important role in laser fusion. They are driven by the incident laser beams in the underdense plasma surrounding a fusion capsule and hinder the absorption process of incident laser light which is necessary to heat the fusion target. Due to its high intensity and power, the laser light modifies the plasma density dynamically, such that two or more parametric instabilities compete, in particular stimulated Brillouin scattering and the filamentation instability. The complicated interplay between these parametric instabilities is studied in detail by developing an adequate model accompanied by numerical simulations with multidimensional codes. The model is applied to generic and to smoothed laser beams, which are necessary to limit parametric instabilities, with parameters close to experimental conditions. (author)

Regular black holes from semi-classical down to Planckian size

Science.gov (United States)

Spallucci, Euro; Smailagic, Anais

In this paper, we review various models of curvature singularity free black holes (BHs). In the first part of the review, we describe semi-classical solutions of the Einstein equations which, however, contains a “quantum” input through the matter source. We start by reviewing the early model by Bardeen where the metric is regularized by-hand through a short-distance cutoff, which is justified in terms of nonlinear electro-dynamical effects. This toy-model is useful to point-out the common features shared by all regular semi-classical black holes. Then, we solve Einstein equations with a Gaussian source encoding the quantum spread of an elementary particle. We identify, the a priori arbitrary, Gaussian width with the Compton wavelength of the quantum particle. This Compton-Gauss model leads to the estimate of a terminal density that a gravitationally collapsed object can achieve. We identify this density to be the Planck density, and reformulate the Gaussian model assuming this as its peak density. All these models, are physically reliable as long as the BH mass is big enough with respect to the Planck mass. In the truly Planckian regime, the semi-classical approximation breaks down. In this case, a fully quantum BH description is needed. In the last part of this paper, we propose a nongeometrical quantum model of Planckian BHs implementing the Holographic Principle and realizing the “classicalization” scenario recently introduced by Dvali and collaborators. The classical relation between the mass and radius of the BH emerges only in the classical limit, far away from the Planck scale.

Theoretical studies of defects in insulators within the framework of the local density approximation

International Nuclear Information System (INIS)

Pederson, M.R.; Klein, B.M.

1989-01-01

The muffin-tin Green's function method and a linear combination of atomic orbitals cluster method for defect studies are discussed. These methods have been used to carry out calculations on F-like centers in MgO, CaO and LiF. Although the local density approximation leads to qualitatively correct information pertaining to the occupied states, in addition to the usual perfect-crystal band gap problem, the unoccupied defect levels are found to lie above the onset of the conducting band, in disagreement with the experimental measurements. Results using two methods for incorporating many-electron corrections into an LDA-like computational algorithm are discussed. These methods are the 'scissor-operator' approach to the band gap problem, and the self-interaction-correction (SIC) framework for improving the local spin density approximation. SIC results for the defect excitation spectra are in very good agreement with experiment. This method, when fully developed, should give an excellent ab initio description of defects in insulators. (author) 29 refs., 3 figs., 1 tab

Relativistic mean-field approximation with density-dependent screening meson masses in nuclear matter

International Nuclear Information System (INIS)

Sun, Baoxi; Lu, Xiaofu; Shen, Pengnian; Zhao, Enguang

2003-01-01

The Debye screening masses of the σ, ω and neutral ρ mesons and the photon are calculated in the relativistic mean-field approximation. As the density of the nucleon increases, all the screening masses of mesons increase. A different result with Brown–Rho scaling is shown, which implies a reduction in the mass of all the mesons in the nuclear matter, except the pion. Replacing the masses of the mesons with their corresponding screening masses in the Walecka-1 model, five saturation properties of the nuclear matter are fixed reasonably, and then a density-dependent relativistic mean-field model is proposed without introducing the nonlinear self-coupling terms of mesons. (author)

Density functional theory of electron transfer beyond the Born-Oppenheimer approximation: Case study of LiF

Science.gov (United States)

Li, Chen; Requist, Ryan; Gross, E. K. U.

2018-02-01

We perform model calculations for a stretched LiF molecule, demonstrating that nonadiabatic charge transfer effects can be accurately and seamlessly described within a density functional framework. In alkali halides like LiF, there is an abrupt change in the ground state electronic distribution due to an electron transfer at a critical bond length R = Rc, where an avoided crossing of the lowest adiabatic potential energy surfaces calls the validity of the Born-Oppenheimer approximation into doubt. Modeling the R-dependent electronic structure of LiF within a two-site Hubbard model, we find that nonadiabatic electron-nuclear coupling produces a sizable elongation of the critical Rc by 0.5 bohr. This effect is very accurately captured by a simple and rigorously derived correction, with an M-1 prefactor, to the exchange-correlation potential in density functional theory, M = reduced nuclear mass. Since this nonadiabatic term depends on gradients of the nuclear wave function and conditional electronic density, ∇Rχ(R) and ∇Rn(r, R), it couples the Kohn-Sham equations at neighboring R points. Motivated by an observed localization of nonadiabatic effects in nuclear configuration space, we propose a local conditional density approximation—an approximation that reduces the search for nonadiabatic density functionals to the search for a single function y(n).

Relativistic effects in ultra-high-intensity laser-plasma interaction: electron parametric instabilities and ponderomotive force

International Nuclear Information System (INIS)

Quesnel, Brice

1998-01-01

This research thesis reports a theoretical and numeric study of the behaviour of two non linear phenomena of the laser-plasma interaction physics in a relativistic regime: the electronic parametric instabilities, and the ponderomotive force. In a first part, the author establishes the three-dimensional scattering relationship of electron parametric instabilities for a circularly polarised wave propagating in a homogeneous and cold plasma, without limitations of wave intensity, nor of plasma density. Results are verified by comparison with those of two-dimensional numerical simulations. The Weibel instability is also briefly studied in relativistic regime. In the second part, the author establishes an expression of the ponderomotive force exerted by an ultra-intense laser pulse in the vacuum about the focus point. A numerical code of integration of equations of motion of an electron in the laser field is used for the different expressions corresponding different approximation degrees. Results are used to interpret a recent experiment, and to critic other theoretical works [fr

An inductive algorithm for smooth approximation of functions

International Nuclear Information System (INIS)

Kupenova, T.N.

2011-01-01

An inductive algorithm is presented for smooth approximation of functions, based on the Tikhonov regularization method and applied to a specific kind of the Tikhonov parametric functional. The discrepancy principle is used for estimation of the regularization parameter. The principle of heuristic self-organization is applied for assessment of some parameters of the approximating function

Intermolecular interactions in the condensed phase: Evaluation of semi-empirical quantum mechanical methods.

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Christensen, Anders S; Kromann, Jimmy C; Jensen, Jan H; Cui, Qiang

2017-10-28

To facilitate further development of approximate quantum mechanical methods for condensed phase applications, we present a new benchmark dataset of intermolecular interaction energies in the solution phase for a set of 15 dimers, each containing one charged monomer. The reference interaction energy in solution is computed via a thermodynamic cycle that integrates dimer binding energy in the gas phase at the coupled cluster level and solute-solvent interaction with density functional theory; the estimated uncertainty of such calculated interaction energy is ±1.5 kcal/mol. The dataset is used to benchmark the performance of a set of semi-empirical quantum mechanical (SQM) methods that include DFTB3-D3, DFTB3/CPE-D3, OM2-D3, PM6-D3, PM6-D3H+, and PM7 as well as the HF-3c method. We find that while all tested SQM methods tend to underestimate binding energies in the gas phase with a root-mean-squared error (RMSE) of 2-5 kcal/mol, they overestimate binding energies in the solution phase with an RMSE of 3-4 kcal/mol, with the exception of DFTB3/CPE-D3 and OM2-D3, for which the systematic deviation is less pronounced. In addition, we find that HF-3c systematically overestimates binding energies in both gas and solution phases. As most approximate QM methods are parametrized and evaluated using data measured or calculated in the gas phase, the dataset represents an important first step toward calibrating QM based methods for application in the condensed phase where polarization and exchange repulsion need to be treated in a balanced fashion.

Intermolecular interactions in the condensed phase: Evaluation of semi-empirical quantum mechanical methods

Science.gov (United States)

Christensen, Anders S.; Kromann, Jimmy C.; Jensen, Jan H.; Cui, Qiang

2017-10-01

To facilitate further development of approximate quantum mechanical methods for condensed phase applications, we present a new benchmark dataset of intermolecular interaction energies in the solution phase for a set of 15 dimers, each containing one charged monomer. The reference interaction energy in solution is computed via a thermodynamic cycle that integrates dimer binding energy in the gas phase at the coupled cluster level and solute-solvent interaction with density functional theory; the estimated uncertainty of such calculated interaction energy is ±1.5 kcal/mol. The dataset is used to benchmark the performance of a set of semi-empirical quantum mechanical (SQM) methods that include DFTB3-D3, DFTB3/CPE-D3, OM2-D3, PM6-D3, PM6-D3H+, and PM7 as well as the HF-3c method. We find that while all tested SQM methods tend to underestimate binding energies in the gas phase with a root-mean-squared error (RMSE) of 2-5 kcal/mol, they overestimate binding energies in the solution phase with an RMSE of 3-4 kcal/mol, with the exception of DFTB3/CPE-D3 and OM2-D3, for which the systematic deviation is less pronounced. In addition, we find that HF-3c systematically overestimates binding energies in both gas and solution phases. As most approximate QM methods are parametrized and evaluated using data measured or calculated in the gas phase, the dataset represents an important first step toward calibrating QM based methods for application in the condensed phase where polarization and exchange repulsion need to be treated in a balanced fashion.

Measurements of parametric instability near the critical density and the resultant electron heating: Final report

International Nuclear Information System (INIS)

Mizuno, K.; De Groot, J.S.; Seka, W.

1986-01-01

Detailed studies of the ion acoustic parametric decay instability have been made. Theoretical and particle simulation results indicate these instabilities are important in long scale length plasma irradiated by moderate intensity laser light (10'' ≤ Iλ 2 /T/sub e/ (W/cm 2 ) (μm 2 )/(keV) ≤ 5 x 10 14 ). Laser light (λ 0 ≅ 1/2 μm) is focused onto a CH target. The parametric decay instability has been measured by detecting the emission spectrum at frequencies near 2ω 0 . The experimental results clearly indicate that this parametric instability is important for short wavelength (1/2 μm) laser light irradiation. The threshold of the parametric instability (λ 0 = 1/2 μm) was only slightly higher than that of 1 μm laser case. The measured wavelength shift of the Stokes component (λ 0 = 1/2 μm) compared very well with the 1 μm laser results

Semi-discrete approximations to nonlinear systems of conservation laws; consistency and L(infinity)-stability imply convergence. Final report

International Nuclear Information System (INIS)

Tadmor, E.

1988-07-01

A convergence theory for semi-discrete approximations to nonlinear systems of conservation laws is developed. It is shown, by a series of scalar counter-examples, that consistency with the conservation law alone does not guarantee convergence. Instead, a notion of consistency which takes into account both the conservation law and its augmenting entropy condition is introduced. In this context it is concluded that consistency and L(infinity)-stability guarantee for a relevant class of admissible entropy functions, that their entropy production rate belongs to a compact subset of H(loc)sup -1 (x,t). One can now use compensated compactness arguments in order to turn this conclusion into a convergence proof. The current state of the art for these arguments includes the scalar and a wide class of 2 x 2 systems of conservation laws. The general framework of the vanishing viscosity method is studied as an effective way to meet the consistency and L(infinity)-stability requirements. How this method is utilized to enforce consistency and stability for scalar conservation laws is shown. In this context we prove, under the appropriate assumptions, the convergence of finite difference approximations (e.g., the high resolution TVD and UNO methods), finite element approximations (e.g., the Streamline-Diffusion methods) and spectral and pseudospectral approximations (e.g., the Spectral Viscosity methods)

On Parametric (and Non-Parametric Variation

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Neil Smith

2009-11-01

Full Text Available This article raises the issue of the correct characterization of ‘Parametric Variation’ in syntax and phonology. After specifying their theoretical commitments, the authors outline the relevant parts of the Principles–and–Parameters framework, and draw a three-way distinction among Universal Principles, Parameters, and Accidents. The core of the contribution then consists of an attempt to provide identity criteria for parametric, as opposed to non-parametric, variation. Parametric choices must be antecedently known, and it is suggested that they must also satisfy seven individually necessary and jointly sufficient criteria. These are that they be cognitively represented, systematic, dependent on the input, deterministic, discrete, mutually exclusive, and irreversible.

Radiation parametric generation in non-linear crystals

International Nuclear Information System (INIS)

Pacheco, M.T.; Pereira, M.A.C.Q.

1983-01-01

A short historical development review is presented on the optical parametric oscillators. Analysis on behaviour of the simple resonant oscillators (SRO), double resonant oscillators (DRO) and ring resonant oscillators (RRO), in the plane wave pumping approximation is shown. Comparision between the three oscillators types is given. (Author) [pt

Approximating distributions from moments

Science.gov (United States)

Pawula, R. F.

1987-11-01

A method based upon Pearson-type approximations from statistics is developed for approximating a symmetric probability density function from its moments. The extended Fokker-Planck equation for non-Markov processes is shown to be the underlying foundation for the approximations. The approximation is shown to be exact for the beta probability density function. The applicability of the general method is illustrated by numerous pithy examples from linear and nonlinear filtering of both Markov and non-Markov dichotomous noise. New approximations are given for the probability density function in two cases in which exact solutions are unavailable, those of (i) the filter-limiter-filter problem and (ii) second-order Butterworth filtering of the random telegraph signal. The approximate results are compared with previously published Monte Carlo simulations in these two cases.

Approximate self-consistent potentials for density-functional-theory exchange-correlation functionals

International Nuclear Information System (INIS)

Cafiero, Mauricio; Gonzalez, Carlos

2005-01-01

We show that potentials for exchange-correlation functionals within the Kohn-Sham density-functional-theory framework may be written as potentials for simpler functionals multiplied by a factor close to unity, and in a self-consistent field calculation, these effective potentials find the correct self-consistent solutions. This simple theory is demonstrated with self-consistent exchange-only calculations of the atomization energies of some small molecules using the Perdew-Kurth-Zupan-Blaha (PKZB) meta-generalized-gradient-approximation (meta-GGA) exchange functional. The atomization energies obtained with our method agree with or surpass previous meta-GGA calculations performed in a non-self-consistent manner. The results of this work suggest the utility of this simple theory to approximate exchange-correlation potentials corresponding to energy functionals too complicated to generate closed forms for their potentials. We hope that this method will encourage the development of complex functionals which have correct boundary conditions and are free of self-interaction errors without the worry that the functionals are too complex to differentiate to obtain potentials

Statistical density of nuclear excited states

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V. M. Kolomietz

2015-10-01

Full Text Available A semi-classical approximation is applied to the calculations of single-particle and statistical level densities in excited nuclei. Landau's conception of quasi-particles with the nucleon effective mass m* < m is used. The approach provides the correct description of the continuum contribution to the level density for realistic finite-depth potentials. It is shown that the continuum states does not affect significantly the thermodynamic calculations for sufficiently small temperatures T ≤ 1 MeV but reduce strongly the results for the excitation energy at high temperatures. By use of standard Woods - Saxon potential and nucleon effective mass m* = 0.7m the A-dependency of the statistical level density parameter K was evaluated in a good qualitative agreement with experimental data.

Whole brain analysis of postmortem density changes of grey and white matter on computed tomography by statistical parametric mapping

Energy Technology Data Exchange (ETDEWEB)

Nishiyama, Yuichi; Mori, Hiroshi; Katsube, Takashi; Kitagaki, Hajime [Shimane University Faculty of Medicine, Department of Radiology, Izumo-shi, Shimane (Japan); Kanayama, Hidekazu; Tada, Keiji; Yamamoto, Yasushi [Shimane University Hospital, Department of Radiology, Izumo-shi, Shimane (Japan); Takeshita, Haruo [Shimane University Faculty of Medicine, Department of Legal Medicine, Izumo-shi, Shimane (Japan); Kawakami, Kazunori [Fujifilm RI Pharma, Co., Ltd., Tokyo (Japan)

2017-06-15

This study examined the usefulness of statistical parametric mapping (SPM) for investigating postmortem changes on brain computed tomography (CT). This retrospective study included 128 patients (23 - 100 years old) without cerebral abnormalities who underwent unenhanced brain CT before and after death. The antemortem CT (AMCT) scans and postmortem CT (PMCT) scans were spatially normalized using our original brain CT template, and postmortem changes of CT values (in Hounsfield units; HU) were analysed by the SPM technique. Compared with AMCT scans, 58.6 % and 98.4 % of PMCT scans showed loss of the cerebral sulci and an unclear grey matter (GM)-white matter (WM) interface, respectively. SPM analysis revealed a significant decrease in cortical GM density within 70 min after death on PMCT scans, suggesting cytotoxic brain oedema. Furthermore, there was a significant increase in the density of the WM, lenticular nucleus and thalamus more than 120 min after death. The SPM technique demonstrated typical postmortem changes on brain CT scans, and revealed that the unclear GM-WM interface on early PMCT scans is caused by a rapid decrease in cortical GM density combined with a delayed increase in WM density. SPM may be useful for assessment of whole brain postmortem changes. (orig.)

Whole brain analysis of postmortem density changes of grey and white matter on computed tomography by statistical parametric mapping

International Nuclear Information System (INIS)

Nishiyama, Yuichi; Mori, Hiroshi; Katsube, Takashi; Kitagaki, Hajime; Kanayama, Hidekazu; Tada, Keiji; Yamamoto, Yasushi; Takeshita, Haruo; Kawakami, Kazunori

2017-01-01

This study examined the usefulness of statistical parametric mapping (SPM) for investigating postmortem changes on brain computed tomography (CT). This retrospective study included 128 patients (23 - 100 years old) without cerebral abnormalities who underwent unenhanced brain CT before and after death. The antemortem CT (AMCT) scans and postmortem CT (PMCT) scans were spatially normalized using our original brain CT template, and postmortem changes of CT values (in Hounsfield units; HU) were analysed by the SPM technique. Compared with AMCT scans, 58.6 % and 98.4 % of PMCT scans showed loss of the cerebral sulci and an unclear grey matter (GM)-white matter (WM) interface, respectively. SPM analysis revealed a significant decrease in cortical GM density within 70 min after death on PMCT scans, suggesting cytotoxic brain oedema. Furthermore, there was a significant increase in the density of the WM, lenticular nucleus and thalamus more than 120 min after death. The SPM technique demonstrated typical postmortem changes on brain CT scans, and revealed that the unclear GM-WM interface on early PMCT scans is caused by a rapid decrease in cortical GM density combined with a delayed increase in WM density. SPM may be useful for assessment of whole brain postmortem changes. (orig.)

Fourier analysis of the parametric resonance in neutrino oscillations

International Nuclear Information System (INIS)

Koike, Masafumi; Ota, Toshihiko; Saito, Masako; Sato, Joe

2009-01-01

Parametric enhancement of the appearance probability of the neutrino oscillation under the inhomogeneous matter is studied. Fourier expansion of the matter density profile leads to a simple resonance condition and manifests that each Fourier mode modifies the energy spectrum of oscillation probability at around the corresponding energy; below the MSW resonance energy, a large-scale variation modifies the spectrum in high energies while a small-scale one does in low energies. In contrast to the simple parametric resonance, the enhancement of the oscillation probability is itself an slow oscillation as demonstrated by a numerical analysis with a single Fourier mode of the matter density. We derive an analytic solution to the evolution equation on the resonance energy, including the expression of frequency of the slow oscillation.

Transport of optical excitations on dendrimers in the continuum approximation

International Nuclear Information System (INIS)

Vlaming, S.M.; Heijs, D.J.; Knoester, J.

2005-01-01

We study the incoherent transport of optical excitations created at the rim of a dendritic molecule to a trap occurring at the core. The corresponding discrete random walk is treated in a continuum approximation, resulting in a diffusion-like process which admits semi-analytical solutions. The thus obtained arrival time distribution for the excitation at the trap is compared with the one for the original, discrete problem. In the case of an inward bias or even a weak outward one, the agreement is very good and the continuum approximation provides a good alternative description of the energy transfer process, even for small dendrimers. In the case of a strong outward bias, the mean trapping time, which sets the time scale for the entire distribution, depends exponentially on the number of generations in both approaches, but with a different base. The failure of the continuum approximation for this case is explained from the peaked behavior of the excitation density near the rim

Parametrization of the average ionization and radiative cooling rates of carbon plasmas in a wide range of density and temperature

International Nuclear Information System (INIS)

Gil, J.M.; Rodriguez, R.; Florido, R.; Rubiano, J.G.; Mendoza, M.A.; Nuez, A. de la; Espinosa, G.; Martel, P.; Minguez, E.

2013-01-01

In this work we present an analysis of the influence of the thermodynamic regime on the monochromatic emissivity, the radiative power loss and the radiative cooling rate for optically thin carbon plasmas over a wide range of electron temperature and density assuming steady state situations. Furthermore, we propose analytical expressions depending on the electron density and temperature for the average ionization and cooling rate based on polynomial fittings which are valid for the whole range of plasma conditions considered in this work. -- Highlights: ► We compute the average ionization, cooling rates and emissivities of carbon plasmas. ► We compare LTE and NLTE calculations of these magnitudes. ► We perform a parametrization of these magnitudes in a wide range of plasma conditions. ► We provide information about where LTE regime assumption is accurate

Semi-quartic force fields retrieved from multi-mode expansions: Accuracy, scaling behavior, and approximations

Energy Technology Data Exchange (ETDEWEB)

Ramakrishnan, Raghunathan [Institute of Physical Chemistry and National Center for Computational Design and Discovery of Novel Materials (MARVEL), Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel (Switzerland); Rauhut, Guntram, E-mail: rauhut@theochem.uni-stuttgart.de [Institute for Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart (Germany)

2015-04-21

Semi-quartic force fields (QFF) rely on a Taylor-expansion of the multi-dimensional Born-Oppenheimer potential energy surface (PES) and are frequently used within the calculation of anharmonic vibrational frequencies based on 2nd order vibrational perturbation theory (VPT2). As such they are usually determined by differentiation of the electronic energy with respect to the nuclear coordinates. Alternatively, potential energy surfaces can be expanded in terms of multi-mode expansions, which typically do not require any derivative techniques. The computational effort to retrieve QFF from size-reduced multi-mode expansions has been studied and has been compared with standard Taylor-expansions. As multi-mode expansions allow for the convenient introduction of subtle approximations, these will be discussed in some detail. In addition, a preliminary study about the applicability of a generalized Duschinsky transformation to QFFs is provided. This transformation allows for the efficient evaluation of VPT2 frequencies of isotopologues from the PES of the parent compound and thus avoids the recalculation of PESs in different axes systems.

Theory of fluctuations and parametric noise in a point nuclear reactor model

International Nuclear Information System (INIS)

Rodriguez, M.A.; San Miguel, M.; Sancho, J.M.

1984-01-01

We present a joint description of internal fluctuations and parametric noise in a point nuclear reactor model in which delayed neutrons and a detector are considered. We obtain kinetic equations for the first moments and define effective kinetic parameters which take into account the effect of parametric Gaussian white noise. We comment on the validity of Langevin approximations for this problem. We propose a general method to deal with weak but otherwise arbitrary non-white parametric noise. Exact kinetic equations are derived for Gaussian non-white noise. (author)

The parametrized simulation of electromagnetic showers

International Nuclear Information System (INIS)

Peters, S.

1992-09-01

The simulation of electromagnetic showers in calorimeters by detailed tracking of all secondary particles is extremely computer time consuming. Without loosing considerably in precision, the use of parametrizations for global shower properties may reduce the computing time by factors of 10 1 to 10 4 , depending on the energy, the degree of parametrization, and the complexity in the material description and the cut off energies in the detailed simulation. To arrive at a high degree of universality, parametrizations of individual electromagnetic showers in homogeneous media are developed, taking the dependence of the shower development on the material into account. In sampling calorimeters, the inhomogeneous material distribution leads to additional effects which can be taken into account by geometry dependent terms in the parametrization of the longitudinal and radial energy density distributions. Comparisons with detailed simulations of homogeneous and sampling calorimeters show very good agreement in the fluctuations, correlations, and signal averages of spatial energy distributions. Verifications of the algorithms for the simulation of the H1 detector are performed using calorimeter test data for different moduls of the H1 liquid argon calorimeter. Special attention has been paid to electron pion separation, which is of great importance for physics analysis. (orig.) [de

Padé approximations and diophantine geometry.

Science.gov (United States)

Chudnovsky, D V; Chudnovsky, G V

1985-04-01

Using methods of Padé approximations we prove a converse to Eisenstein's theorem on the boundedness of denominators of coefficients in the expansion of an algebraic function, for classes of functions, parametrized by meromorphic functions. This result is applied to the Tate conjecture on the effective description of isogenies for elliptic curves.

APPROXIMATIONS TO PERFORMANCE MEASURES IN QUEUING SYSTEMS

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Kambo, N. S.

2012-11-01

Full Text Available Approximations to various performance measures in queuing systems have received considerable attention because these measures have wide applicability. In this paper we propose two methods to approximate the queuing characteristics of a GI/M/1 system. The first method is non-parametric in nature, using only the first three moments of the arrival distribution. The second method treads the known path of approximating the arrival distribution by a mixture of two exponential distributions by matching the first three moments. Numerical examples and optimal analysis of performance measures of GI/M/1 queues are provided to illustrate the efficacy of the methods, and are compared with benchmark approximations.

Two-parametric model of electron beam in computational dosimetry for radiation processing

International Nuclear Information System (INIS)

Lazurik, V.M.; Lazurik, V.T.; Popov, G.; Zimek, Z.

2016-01-01

Computer simulation of irradiation process of various materials with electron beam (EB) can be applied to correct and control the performances of radiation processing installations. Electron beam energy measurements methods are described in the international standards. The obtained results of measurements can be extended by implementation computational dosimetry. Authors have developed the computational method for determination of EB energy on the base of two-parametric fitting of semi-empirical model for the depth dose distribution initiated by mono-energetic electron beam. The analysis of number experiments show that described method can effectively consider random displacements arising from the use of aluminum wedge with a continuous strip of dosimetric film and minimize the magnitude uncertainty value of the electron energy evaluation, calculated from the experimental data. Two-parametric fitting method is proposed for determination of the electron beam model parameters. These model parameters are as follow: E 0 – energy mono-energetic and mono-directional electron source, X 0 – the thickness of the aluminum layer, located in front of irradiated object. That allows obtain baseline data related to the characteristic of the electron beam, which can be later on applied for computer modeling of the irradiation process. Model parameters which are defined in the international standards (like E p – the most probably energy and R p – practical range) can be linked with characteristics of two-parametric model (E 0 , X 0 ), which allows to simulate the electron irradiation process. The obtained data from semi-empirical model were checked together with the set of experimental results. The proposed two-parametric model for electron beam energy evaluation and estimation of accuracy for computational dosimetry methods on the base of developed model are discussed. - Highlights: • Experimental and computational methods of electron energy evaluation. • Development

Consistent Atomic Geometries and Electronic Structure of Five Phases of Potassium Niobate from Density-Functional Theory

Directory of Open Access Journals (Sweden)

Falko Schmidt

2017-01-01

Full Text Available We perform a comprehensive theoretical study of the structural and electronic properties of potassium niobate (KNbO3 in the cubic, tetragonal, orthorhombic, monoclinic, and rhombohedral phase, based on density-functional theory. The influence of different parametrizations of the exchange-correlation functional on the investigated properties is analyzed in detail, and the results are compared to available experimental data. We argue that the PBEsol and AM05 generalized gradient approximations as well as the RTPSS meta-generalized gradient approximation yield consistently accurate structural data for both the external and internal degrees of freedom and are overall superior to the local-density approximation or other conventional generalized gradient approximations for the structural characterization of KNbO3. Band-structure calculations using a HSE-type hybrid functional further indicate significant near degeneracies of band-edge states in all phases which are expected to be relevant for the optical response of the material.

Many-body perturbation theory using the density-functional concept: beyond the GW approximation

OpenAIRE

Bruneval, Fabien; Sottile, Francesco; Olevano, Valerio; Del Sole, Rodolfo; Reining, Lucia

2005-01-01

We propose an alternative formulation of Many-Body Perturbation Theory that uses the density-functional concept. Instead of the usual four-point integral equation for the polarizability, we obtain a two-point one, that leads to excellent optical absorption and energy loss spectra. The corresponding three-point vertex function and self-energy are then simply calculated via an integration, for any level of approximation. Moreover, we show the direct impact of this formulation on the time-depend...

Density dependent hadron field theory

International Nuclear Information System (INIS)

Fuchs, C.; Lenske, H.; Wolter, H.H.

1995-01-01

A fully covariant approach to a density dependent hadron field theory is presented. The relation between in-medium NN interactions and field-theoretical meson-nucleon vertices is discussed. The medium dependence of nuclear interactions is described by a functional dependence of the meson-nucleon vertices on the baryon field operators. As a consequence, the Euler-Lagrange equations lead to baryon rearrangement self-energies which are not obtained when only a parametric dependence of the vertices on the density is assumed. It is shown that the approach is energy-momentum conserving and thermodynamically consistent. Solutions of the field equations are studied in the mean-field approximation. Descriptions of the medium dependence in terms of the baryon scalar and vector density are investigated. Applications to infinite nuclear matter and finite nuclei are discussed. Density dependent coupling constants obtained from Dirac-Brueckner calculations with the Bonn NN potentials are used. Results from Hartree calculations for energy spectra, binding energies, and charge density distributions of 16 O, 40,48 Ca, and 208 Pb are presented. Comparisons to data strongly support the importance of rearrangement in a relativistic density dependent field theory. Most striking is the simultaneous improvement of charge radii, charge densities, and binding energies. The results indicate the appearance of a new ''Coester line'' in the nuclear matter equation of state

Unconventional application of the two-flux approximation for the calculation of the Ambartsumyan-Chandrasekhar function and the angular spectrum of the backward-scattered radiation for a semi-infinite isotropically scattering medium

Science.gov (United States)

Remizovich, V. S.

2010-06-01

It is commonly accepted that the Schwarzschild-Schuster two-flux approximation (1905, 1914) can be employed only for the calculation of the energy characteristics of the radiation field (energy density and energy flux density) and cannot be used to characterize the angular distribution of radiation field. However, such an inference is not valid. In several cases, one can calculate the radiation intensity inside matter and the reflected radiation with the aid of this simplest approximation in the transport theory. In this work, we use the results of the simplest one-parameter variant of the two-flux approximation to calculate the angular distribution (reflection function) of the radiation reflected by a semi-infinite isotropically scattering dissipative medium when a relatively broad beam is incident on the medium at an arbitrary angle relative to the surface. We do not employ the invariance principle and demonstrate that the reflection function exhibits the multiplicative property. It can be represented as a product of three functions: the reflection function corresponding to the single scattering and two identical h functions, which have the same physical meaning as the Ambartsumyan-Chandrasekhar function ( H) has. This circumstance allows a relatively easy derivation of simple analytical expressions for the H function, total reflectance, and reflection function. We can easily determine the relative contribution of the true single scattering in the photon backscattering at an arbitrary probability of photon survival Λ. We compare all of the parameters of the backscattered radiation with the data resulting from the calculations using the exact theory of Ambartsumyan, Chandrasekhar, et al., which was developed decades after the two-flux approximation. Thus, we avoid the application of fine mathematical methods (the Wiener-Hopf method, the Case method of singular functions, etc.) and obtain simple analytical expressions for the parameters of the scattered radiation

Parametric evaluation of laser ablation and ionization time-of-flight mass spectrometry with ion guide cooling cell

International Nuclear Information System (INIS)

Peng Ding; He Jian; Yu Quan; Chen Lizhi; Hang Wei; Huang Benli

2008-01-01

A novel laser ablation and ionization time-of-flight mass spectrometer has been used for direct elemental analysis of alloys. The system was incorporated with an ion guide cooling cell to reduce the kinetic energy distribution for the purpose of better resolution. Parametric studies have been conducted on the system with respect to the buffer gas pressure and the distance from sample to the nozzle to obtain the maximal signal intensities. In order to obtain satisfactory relative sensitivity coefficients (RSC) for different elements, the influence of the laser irradiance, nozzle voltage, rf frequency and voltage of the hexapole were also investigated. Under the optimized conditions, the RSC of different elements were available for direct semi-quantitative analysis. The mass resolving power (FWHM) of the spectrometer was approximately 7000 (m/Δm) and the limit of detection (LOD) was 10 -6 g/g

Semi-metallic polymers

DEFF Research Database (Denmark)

Bubnova, Olga; Khan, Zia Ullah; Wang, Hui

2014-01-01

Polymers are lightweight, flexible, solution-processable materials that are promising for low-cost printed electronics as well as for mass-produced and large-area applications. Previous studies demonstrated that they can possess insulating, semiconducting or metallic properties; here we report...... that polymers can also be semi-metallic. Semi-metals, exemplified by bismuth, graphite and telluride alloys, have no energy bandgap and a very low density of states at the Fermi level. Furthermore, they typically have a higher Seebeck coefficient and lower thermal conductivities compared with metals, thus being...... a Fermi glass to a semi-metal. The high Seebeck value, the metallic conductivity at room temperature and the absence of unpaired electron spins makes polymer semi-metals attractive for thermoelectrics and spintronics....

Exchange-correlation energy from pairing matrix fluctuation and the particle-particle random phase approximation.

Science.gov (United States)

van Aggelen, Helen; Yang, Yang; Yang, Weitao

2014-05-14

Despite their unmatched success for many applications, commonly used local, semi-local, and hybrid density functionals still face challenges when it comes to describing long-range interactions, static correlation, and electron delocalization. Density functionals of both the occupied and virtual orbitals are able to address these problems. The particle-hole (ph-) Random Phase Approximation (RPA), a functional of occupied and virtual orbitals, has recently known a revival within the density functional theory community. Following up on an idea introduced in our recent communication [H. van Aggelen, Y. Yang, and W. Yang, Phys. Rev. A 88, 030501 (2013)], we formulate more general adiabatic connections for the correlation energy in terms of pairing matrix fluctuations described by the particle-particle (pp-) propagator. With numerical examples of the pp-RPA, the lowest-order approximation to the pp-propagator, we illustrate the potential of density functional approximations based on pairing matrix fluctuations. The pp-RPA is size-extensive, self-interaction free, fully anti-symmetric, describes the strong static correlation limit in H2, and eliminates delocalization errors in H2(+) and other single-bond systems. It gives surprisingly good non-bonded interaction energies--competitive with the ph-RPA--with the correct R(-6) asymptotic decay as a function of the separation R, which we argue is mainly attributable to its correct second-order energy term. While the pp-RPA tends to underestimate absolute correlation energies, it gives good relative energies: much better atomization energies than the ph-RPA, as it has no tendency to underbind, and reaction energies of similar quality. The adiabatic connection in terms of pairing matrix fluctuation paves the way for promising new density functional approximations.

Exchange-correlation energy from pairing matrix fluctuation and the particle-particle random phase approximation

International Nuclear Information System (INIS)

Aggelen, Helen van; Yang, Yang; Yang, Weitao

2014-01-01

Despite their unmatched success for many applications, commonly used local, semi-local, and hybrid density functionals still face challenges when it comes to describing long-range interactions, static correlation, and electron delocalization. Density functionals of both the occupied and virtual orbitals are able to address these problems. The particle-hole (ph-) Random Phase Approximation (RPA), a functional of occupied and virtual orbitals, has recently known a revival within the density functional theory community. Following up on an idea introduced in our recent communication [H. van Aggelen, Y. Yang, and W. Yang, Phys. Rev. A 88, 030501 (2013)], we formulate more general adiabatic connections for the correlation energy in terms of pairing matrix fluctuations described by the particle-particle (pp-) propagator. With numerical examples of the pp-RPA, the lowest-order approximation to the pp-propagator, we illustrate the potential of density functional approximations based on pairing matrix fluctuations. The pp-RPA is size-extensive, self-interaction free, fully anti-symmetric, describes the strong static correlation limit in H 2 , and eliminates delocalization errors in H 2 + and other single-bond systems. It gives surprisingly good non-bonded interaction energies – competitive with the ph-RPA – with the correct R −6 asymptotic decay as a function of the separation R, which we argue is mainly attributable to its correct second-order energy term. While the pp-RPA tends to underestimate absolute correlation energies, it gives good relative energies: much better atomization energies than the ph-RPA, as it has no tendency to underbind, and reaction energies of similar quality. The adiabatic connection in terms of pairing matrix fluctuation paves the way for promising new density functional approximations

Involute Spur Gear Template Development by Parametric Technique ...

African Journals Online (AJOL)

There are many methods available for developing profiles of gear and spline teeth. Most of the techniques are inaccurate because they use only an approximation of the involute curve profile. The parametric method developed in this paper provides accurate involute curve creation using formulas and exact geometric ...

Semi-implicit iterative methods for low Mach number turbulent reacting flows: Operator splitting versus approximate factorization

Science.gov (United States)

MacArt, Jonathan F.; Mueller, Michael E.

2016-12-01

Two formally second-order accurate, semi-implicit, iterative methods for the solution of scalar transport-reaction equations are developed for Direct Numerical Simulation (DNS) of low Mach number turbulent reacting flows. The first is a monolithic scheme based on a linearly implicit midpoint method utilizing an approximately factorized exact Jacobian of the transport and reaction operators. The second is an operator splitting scheme based on the Strang splitting approach. The accuracy properties of these schemes, as well as their stability, cost, and the effect of chemical mechanism size on relative performance, are assessed in two one-dimensional test configurations comprising an unsteady premixed flame and an unsteady nonpremixed ignition, which have substantially different Damköhler numbers and relative stiffness of transport to chemistry. All schemes demonstrate their formal order of accuracy in the fully-coupled convergence tests. Compared to a (non-)factorized scheme with a diagonal approximation to the chemical Jacobian, the monolithic, factorized scheme using the exact chemical Jacobian is shown to be both more stable and more economical. This is due to an improved convergence rate of the iterative procedure, and the difference between the two schemes in convergence rate grows as the time step increases. The stability properties of the Strang splitting scheme are demonstrated to outpace those of Lie splitting and monolithic schemes in simulations at high Damköhler number; however, in this regime, the monolithic scheme using the approximately factorized exact Jacobian is found to be the most economical at practical CFL numbers. The performance of the schemes is further evaluated in a simulation of a three-dimensional, spatially evolving, turbulent nonpremixed planar jet flame.

Electronic structure of the Fe2 molecule in the local-spin-density approximation

International Nuclear Information System (INIS)

Dhar, S.; Kestner, N.R.

1988-01-01

Ab initio self-consistent all-electron spin-polarized calculations have been performed for the ground-state properties of the Fe 2 molecule using the local-spin-density approximation. A Gaussian orbital basis is employed and all the two-electron integrals are evaluated analytically. The matrix elements of the exchange-correlation potential are computed numerically. The total energy, the binding energy, the equilibrium distance, vibrational frequency, and the ground-state configurations are reported and compared with other calculations and experimental results

Classification rates: non‐parametric verses parametric models using ...

African Journals Online (AJOL)

This research sought to establish if non parametric modeling achieves a higher correct classification ratio than a parametric model. The local likelihood technique was used to model fit the data sets. The same sets of data were modeled using parametric logit and the abilities of the two models to correctly predict the binary ...

Dynamical pion production via parametric resonance from disoriented chiral condensates

Science.gov (United States)

Hiro-Oka, Hideaki; Minakata, Hisakazu

2000-04-01

We discuss a dynamical mechanism of pion production from disoriented chiral condensates. It leads to an explosive production of pions via the parametric resonance mechanism, which is similar to the reheating mechanism in inflationary cosmology. Classically it is related with the instability in the solutions of the Mathieu equation and we explore the quantum aspects of the mechanism. We show that nonlinearities and back reactions can be ignorable for a sufficiently long time under the small amplitude approximations of background σ oscillations, which may be appropriate for the late stage of a nonequilibrium phase transition. It allows us to obtain an explicit quantum state of the produced pions and σ, the squeezed state of BCS type. Single particle distributions and two pion correlation functions are computed within these approximations. The results obtained illuminate the characteristic features of multipion states produced through the parametric amplification mechanism. In particular, two pion correlations of various charge combinations contain back-to-back correlations which cannot be masked by the identical particle interference effect. We suggest that the parametric resonance mechanism might be a cause of the long lasting amplification of low-momentum modes in linear sigma model simulations.

Learning about the energy density of liquid and semi-solid foods.

Science.gov (United States)

Hogenkamp, P S; Stafleu, A; Mars, M; de Graaf, C

2012-09-01

People learn about a food's satiating capacity by exposure and consequently adjust their energy intake. To investigate the effect of energy density and texture on subsequent energy intake adjustments during repeated consumption. In a randomized crossover design, participants (n=27, age: 21±2.4 years, body mass index: 22.2±1.6 kg m(-2)) repeatedly consumed highly novel foods that were either low-energy-dense (LE: 30 kcal per 100 g) or high-energy-dense (HE: 130 kcal per 100 g), and either liquid or semi-solid, resulting in four product conditions. In each condition, a fixed portion of test food was consumed nine times as an obligatory part of breakfast, lunch and dinner on 3 consecutive days. All meals continued with an ad libitum buffet; food items for evening consumption were provided and the intake (kcal per day) was measured. Buffet intake depended on energy density and day of consumption of the test foods (day*energy interaction: P=0.02); daily buffet intake increased from day 1 (1745±577 kcal) to day 3 (1979±567 kcal) in the LE conditions; intake did not change in the HE conditions (day 1: 1523±429 kcal, day 3: 1589±424 kcal). Food texture did not affect the intake (P=0.56). Intake did depend on energy density of the test foods; participants increased their buffet intake over days in response to learning about the satiating capacity of the LE foods, but did not change buffet intake over days when repeatedly consuming a HE food as part of their meal. The adjustments in intake were made irrespective of the food texture.

Fabrication of metal matrix composite by semi-solid powder processing

Energy Technology Data Exchange (ETDEWEB)

Wu, Yufeng [Iowa State Univ., Ames, IA (United States)

2011-01-01

Various metal matrix composites (MMCs) are widely used in the automotive, aerospace and electrical industries due to their capability and flexibility in improving the mechanical, thermal and electrical properties of a component. However, current manufacturing technologies may suffer from insufficient process stability and reliability and inadequate economic efficiency and may not be able to satisfy the increasing demands placed on MMCs. Semi-solid powder processing (SPP), a technology that combines traditional powder metallurgy and semi-solid forming methods, has potential to produce MMCs with low cost and high efficiency. In this work, the analytical study and experimental investigation of SPP on the fabrication of MMCs were explored. An analytical model was developed to understand the deformation mechanism of the powder compact in the semi-solid state. The densification behavior of the Al6061 and SiC powder mixtures was investigated with different liquid fractions and SiC volume fractions. The limits of SPP were analyzed in terms of reinforcement phase loading and its impact on the composite microstructure. To explore adoption of new materials, carbon nanotube (CNT) was investigated as a reinforcing material in aluminum matrix using SPP. The process was successfully modeled for the mono-phase powder (Al6061) compaction and the density and density distribution were predicted. The deformation mechanism at low and high liquid fractions was discussed. In addition, the compaction behavior of the ceramic-metal powder mixture was understood, and the SiC loading limit was identified by parametric study. For the fabrication of CNT reinforced Al6061 composite, the mechanical alloying of Al6061-CNT powders was first investigated. A mathematical model was developed to predict the CNT length change during the mechanical alloying process. The effects of mechanical alloying time and processing temperature during SPP were studied on the mechanical, microstructural and

Coupled oscillators in identification of nonlinear damping of a real parametric pendulum

Science.gov (United States)

Olejnik, Paweł; Awrejcewicz, Jan

2018-01-01

A damped parametric pendulum with friction is identified twice by means of its precise and imprecise mathematical model. A laboratory test stand designed for experimental investigations of nonlinear effects determined by a viscous resistance and the stick-slip phenomenon serves as the model mechanical system. An influence of accurateness of mathematical modeling on the time variability of the nonlinear damping coefficient of the oscillator is proved. A free decay response of a precisely and imprecisely modeled physical pendulum is dependent on two different time-varying coefficients of damping. The coefficients of the analyzed parametric oscillator are identified with the use of a new semi-empirical method based on a coupled oscillators approach, utilizing the fractional order derivative of the discrete measurement series treated as an input to the numerical model. Results of application of the proposed method of identification of the nonlinear coefficients of the damped parametric oscillator have been illustrated and extensively discussed.

Approximating centrality in evolving graphs: toward sublinearity

Science.gov (United States)

Priest, Benjamin W.; Cybenko, George

2017-05-01

The identification of important nodes is a ubiquitous problem in the analysis of social networks. Centrality indices (such as degree centrality, closeness centrality, betweenness centrality, PageRank, and others) are used across many domains to accomplish this task. However, the computation of such indices is expensive on large graphs. Moreover, evolving graphs are becoming increasingly important in many applications. It is therefore desirable to develop on-line algorithms that can approximate centrality measures using memory sublinear in the size of the graph. We discuss the challenges facing the semi-streaming computation of many centrality indices. In particular, we apply recent advances in the streaming and sketching literature to provide a preliminary streaming approximation algorithm for degree centrality utilizing CountSketch and a multi-pass semi-streaming approximation algorithm for closeness centrality leveraging a spanner obtained through iteratively sketching the vertex-edge adjacency matrix. We also discuss possible ways forward for approximating betweenness centrality, as well as spectral measures of centrality. We provide a preliminary result using sketched low-rank approximations to approximate the output of the HITS algorithm.

Multiple gamma lines from semi-annihilation

International Nuclear Information System (INIS)

D'Eramo, Francesco; McCullough, Matthew; Thaler, Jesse

2013-01-01

Hints in the Fermi data for a 130 GeV gamma line from the galactic center have ignited interest in potential gamma line signatures of dark matter. Explanations of this line based on dark matter annihilation face a parametric tension since they often rely on large enhancements of loop-suppressed cross sections. In this paper, we pursue an alternative possibility that dark matter gamma lines could arise from ''semi-annihilation'' among multiple dark sector states. The semi-annihilation reaction ψ i ψ j → ψ k γ with a single final state photon is typically enhanced relative to ordinary annihilation ψ i ψ-bar i → γγ into photon pairs. Semi-annihilation allows for a wide range of dark matter masses compared to the fixed mass value required by annihilation, opening the possibility to explain potential dark matter signatures at higher energies. The most striking prediction of semi-annihilation is the presence of multiple gamma lines, with as many as order N 3 lines possible for N dark sector states, allowing for dark sector spectroscopy. A smoking gun signature arises in the simplest case of degenerate dark matter, where a strong semi-annihilation line at 130 GeV would be accompanied by a weaker annihilation line at 173 GeV. As a proof of principle, we construct two explicit models of dark matter semi-annihilation, one based on non-Abelian vector dark matter and the other based on retrofitting Rayleigh dark matter

Understanding uncertainties in non-linear population trajectories: a Bayesian semi-parametric hierarchical approach to large-scale surveys of coral cover.

Directory of Open Access Journals (Sweden)

Julie Vercelloni

Full Text Available Recently, attempts to improve decision making in species management have focussed on uncertainties associated with modelling temporal fluctuations in populations. Reducing model uncertainty is challenging; while larger samples improve estimation of species trajectories and reduce statistical errors, they typically amplify variability in observed trajectories. In particular, traditional modelling approaches aimed at estimating population trajectories usually do not account well for nonlinearities and uncertainties associated with multi-scale observations characteristic of large spatio-temporal surveys. We present a Bayesian semi-parametric hierarchical model for simultaneously quantifying uncertainties associated with model structure and parameters, and scale-specific variability over time. We estimate uncertainty across a four-tiered spatial hierarchy of coral cover from the Great Barrier Reef. Coral variability is well described; however, our results show that, in the absence of additional model specifications, conclusions regarding coral trajectories become highly uncertain when considering multiple reefs, suggesting that management should focus more at the scale of individual reefs. The approach presented facilitates the description and estimation of population trajectories and associated uncertainties when variability cannot be attributed to specific causes and origins. We argue that our model can unlock value contained in large-scale datasets, provide guidance for understanding sources of uncertainty, and support better informed decision making.

Semi-Local DFT Functionals with Exact-Exchange-Like Features: Beyond the AK13

Science.gov (United States)

Armiento, Rickard

The Armiento-Kümmel functional from 2013 (AK13) is a non-empirical semi-local exchange functional on generalized gradient approximation form (GGA) in Kohn-Sham (KS) density functional theory (DFT). Recent works have established that AK13 gives improved electronic-structure exchange features over other semi-local methods, with a qualitatively improved orbital description and band structure. For example, the Kohn-Sham band gap is greatly extended, as it is for exact exchange. This talk outlines recent efforts towards new exchange-correlation functionals based on, and extending, the AK13 design ideas. The aim is to improve the quantitative accuracy, the description of energetics, and to address other issues found with the original formulation. Swedish e-Science Research Centre (SeRC).

Relativistic Random-Phase Approximation with Density-dependent Meson-nucleon Couplings at Finite Temperature

International Nuclear Information System (INIS)

Niu, Y.; Paar, N.; Vretenar, D.; Meng, J.

2009-01-01

The fully self-consistent relativistic random-phase approximation (RRPA) framework based on effective interactions with a phenomenological density dependence is extended to finite temperatures. The RRPA configuration space is built from the spectrum of single-nucleon states at finite temperature obtained by the temperature dependent relativistic mean field (RMF-T) theory based on effective Lagrangian with density dependent meson-nucleon vertex functions. As an illustration, the dependence of binding energy, radius, entropy and single particle levels on temperature for spherical nucleus 2 08P b is investigated in RMF-T theory. The finite temperature RRPA has been employed in studies of giant monopole and dipole resonances, and the evolution of resonance properties has been studied as a function of temperature. In addition, exotic modes of excitation have been systematically explored at finite temperatures, with an emphasis on the case of pygmy dipole resonances.(author)

Nonlinear dynamics of parametrically driven particles in a Φ6 potential

International Nuclear Information System (INIS)

Tchawoua, C; Siewe Siewe, M; Tchatchueng, S; Moukam Kakmeni, F M

2008-01-01

A general parametrically excited mechanical system is considered. Approximate solutions are determined by applying the method of multiple time scales. It is shown that only combination parametric resonance of the additive type is possible for the system examined. For this case, the existence and stability properties of the fixed points of the averaged equations corresponding to the nontrivial periodic solutions of the original system are investigated. Thus, emphasis is placed on understanding the chaotic behaviour of the extended Duffing oscillator in the Φ 6 potential under parametric excitation for a specific parameter choice. From the Melnikov-type technique, we obtain the conditions for the existence of homoclinic or heteroclinic bifurcation. Our analysis is carried out in the case of a triple well with a double hump which does not lead to unbounded motion; this analysis is complemented by numerical simulations from which we illustrate the fractality of the basins of attraction. The results show that the threshold amplitude of parametric excitation moves upwards as the parametric intensity increases. Numerical simulations including bifurcation diagrams, Lyapunov exponents, phase portraits and Poincaré maps are shown

The shell effects in s-wave neutron resonance level densities ρ according to combinatorial calculations and on the basis of the semi-classical approach

International Nuclear Information System (INIS)

Kaczmarczyk, Maria

2005-01-01

The results of calculations of level densities ρ, in the vicinity of the neutron binding energy S n , are presented. These results were obtained using the Boehning combinatorial method for the calculation of particle-hole state densities dependent on the number of decompositions of the nucleus excitation energy to energies of independent fermions. The calculation was based on the semi-classical model description in the computation of particle-hole state densities and then of the level densities ρ, and takes into account the existence of energy gaps Δ, located near the Fermi level, in a single particle level scheme. This procedure considerably improved and extended the Boehning calculation method. The results, which were obtained in this way for ρ, for 220 nuclei, reproduce the regularities observed in the experimental values of ρ, which are dependent on the neutron number N, and they agree with the experimental data within two orders of magnitude. In addition, the neutron resonance densities ρ were calculated on the basis of the particle-hole state densities obtained using the analytical formula from Boehning's paper. To make the calculations possible, the values of 'complexity' k, as given in the semi-classical model, and the spin factors R(J), according to the paper by Ryckbosch, were used

A non-parametric Bayesian approach to decompounding from high frequency data

NARCIS (Netherlands)

Gugushvili, Shota; van der Meulen, F.H.; Spreij, Peter

2016-01-01

Given a sample from a discretely observed compound Poisson process, we consider non-parametric estimation of the density f0 of its jump sizes, as well as of its intensity λ0. We take a Bayesian approach to the problem and specify the prior on f0 as the Dirichlet location mixture of normal densities.

Shell Effect and Temperature Influence on Nuclear Level Density Parameter: the role of the effective mass interaction

International Nuclear Information System (INIS)

Queipo-Ruiz, J.; Guzman-Martinez, F.; Rodriguez-Hoyos, O.

2011-01-01

The level density parameter is a very important ingredient in statistic study of nuclear reaction, it has been studied to low energies excitation E < 2MeV where it values is approximately constant, experimental results to energies of excitation more than 2 MeV has been obtained of evaporation spectrum, to nuclei with A=160. In this work we present a calculation of densities level parameter, for a wide range of mass and temperature, taking in accounts the shell effects and the mass effective interaction. The result has been carried out within the semi classical approximation, for the single particle level densities. We results have a reasonable agreement with the experimental data available. (Author)

Charge transfer excitations from exact and approximate ensemble Kohn-Sham theory

Science.gov (United States)

Gould, Tim; Kronik, Leeor; Pittalis, Stefano

2018-05-01

By studying the lowest excitations of an exactly solvable one-dimensional soft-Coulomb molecular model, we show that components of Kohn-Sham ensembles can be used to describe charge transfer processes. Furthermore, we compute the approximate excitation energies obtained by using the exact ensemble densities in the recently formulated ensemble Hartree-exchange theory [T. Gould and S. Pittalis, Phys. Rev. Lett. 119, 243001 (2017)]. Remarkably, our results show that triplet excitations are accurately reproduced across a dissociation curve in all cases tested, even in systems where ground state energies are poor due to strong static correlations. Singlet excitations exhibit larger deviations from exact results but are still reproduced semi-quantitatively.

Study of parametric instabilities during the Alcator C lower hybrid wave heating experiments

International Nuclear Information System (INIS)

Takase, Y.

1983-10-01

Parametric excitation of ion-cyclotron quasi-modes (ω/sub R/ approx. = nω/sub ci/) and ion-sound quasi-modes (ω/sub R/ approx. = k/sub parallel to/v/sub ti/) during lower hybrid wave heating of tokamak plasmas have been studied in detail. Such instabilities may significantly modify the incident wavenumber spectrum near the plasma edge. Convective losses for these instabilities are high if well-defined resonance cones exist, but they are significantly reduced if the resonance cones spread and fill the plasma volume (or some region of it). These instabilities preferentially excite lower hybrid waves with larger values of n/sub parallel to/ than themselves possess, and the new waves tend to be absorbed near the outer layers of the plasma. Parametric instabilities during lower hybrid heating of Alcator C plasmas have been investigated using rf probes (to study tilde phi and tilde n/sub i/) and CO 2 scattering technique (to study tilde n/sub e/). At lower densities (anti n/sub e/ less than or equal to 0.5 x 10 14 cm -3 ) where waves observed in the plasma interior using CO 2 scattering appear to be localized, parametric decay is very weak. Both ion-sound and ion-cyclotron parametric decay processes have been observed at higher densities (anti n greater than or equal to 1.5 x 10 14 cm -3 ) where waves appear to be unlocalized. Finally, at still higher densities (anti n /sub e/ greater than or equal to 2 x 10 4 cm -3 ) pump depletion has been observed. Above these densities heating and current drive efficiencies are expected to degrade significantly

Parametric study on the performance of automotive MR shock absorbers

Science.gov (United States)

Gołdasz, J.; Dzierżek, S.

2016-09-01

The paper contains the results of a parametric study to explore the influence of various quantities on the performance range of semi-active automotive shock absorbers using the magnetorheological (MR) fluid under steady-state and transient excitations. The analysis was performed with simulated data and using a standard single-tube shock absorber configuration with a single-gap MR valve. Additionally, the impact of material variables and valves geometry was examined as the parameters were varied and its dynamic range studied.

Semi-analytical quasi-normal mode theory for the local density of states in coupled photonic crystal cavity-waveguide structures

DEFF Research Database (Denmark)

de Lasson, Jakob Rosenkrantz; Kristensen, Philip Trøst; Mørk, Jesper

2015-01-01

We present and validate a semi-analytical quasi-normal mode (QNM) theory for the local density of states (LDOS) in coupled photonic crystal (PhC) cavity-waveguide structures. By means of an expansion of the Green's function on one or a few QNMs, a closed-form expression for the LDOS is obtained, ......-trivial spectrum with a peak and a dip is found, which is reproduced only when including both the two relevant QNMs in the theory. In both cases, we find relative errors below 1% in the bandwidth of interest.......We present and validate a semi-analytical quasi-normal mode (QNM) theory for the local density of states (LDOS) in coupled photonic crystal (PhC) cavity-waveguide structures. By means of an expansion of the Green's function on one or a few QNMs, a closed-form expression for the LDOS is obtained......, and for two types of two-dimensional PhCs, with one and two cavities side-coupled to an extended waveguide, the theory is validated against numerically exact computations. For the single cavity, a slightly asymmetric spectrum is found, which the QNM theory reproduces, and for two cavities a non...

Two-parametric model of metals hardening during cold working

International Nuclear Information System (INIS)

Khajkin, B.E.

1985-01-01

Mathematical models of cold working metal resistance σ depending on deformation degree have been analyzed. Advantage of two-parametric formula combining simplicity with satisfactory accuracy of experimental data approximation is noted. The formula is convenient when determining value σ, which is average with respect of deformation location, as average geometric value

Elastic full-waveform inversion and parametrization analysis applied to walk-away vertical seismic profile data for unconventional (heavy oil) reservoir characterization

Science.gov (United States)

Pan, Wenyong; Innanen, Kristopher A.; Geng, Yu

2018-06-01

Seismic full-waveform inversion (FWI) methods hold strong potential to recover multiple subsurface elastic properties for hydrocarbon reservoir characterization. Simultaneously updating multiple physical parameters introduces the problem of interparameter trade-off, arising from the simultaneous variations of different physical parameters, which increase the nonlinearity and uncertainty of multiparameter FWI. The coupling effects of different physical parameters are significantly influenced by model parametrization and acquisition arrangement. An appropriate choice of model parametrization is important to successful field data applications of multiparameter FWI. The objective of this paper is to examine the performance of various model parametrizations in isotropic-elastic FWI with walk-away vertical seismic profile (W-VSP) data for unconventional heavy oil reservoir characterization. Six model parametrizations are considered: velocity-density (α, β and ρ΄), modulus-density (κ, μ and ρ), Lamé-density (λ, μ΄ and ρ‴), impedance-density (IP, IS and ρ″), velocity-impedance-I (α΄, β΄ and I_P^' }) and velocity-impedance-II (α″, β″ and I_S^' }). We begin analysing the interparameter trade-off by making use of scattering radiation patterns, which is a common strategy for qualitative parameter resolution analysis. We discuss the advantages and limitations of the scattering radiation patterns and recommend that interparameter trade-offs be evaluated using interparameter contamination kernels, which provide quantitative, second-order measurements of the interparameter contaminations and can be constructed efficiently with an adjoint-state approach. Synthetic W-VSP isotropic-elastic FWI experiments in the time domain verify our conclusions about interparameter trade-offs for various model parametrizations. Density profiles are most strongly influenced by the interparameter contaminations; depending on model parametrization, the inverted density

Effect of Stocking Density on Performance of Growing Rabbits in Semi-Humid Tropics

Directory of Open Access Journals (Sweden)

Iyeghe-Erakpotobor Grace, T.

2005-01-01

rabbits as stocking density increases in week 1-2 and 3-4. Feed conversion ratio was poorer at higher densities (16.7, 20 rabbits/m2 than at lower densities (6.7, 10, 13.3 rabbits/m2. There was no definite relationship between stocking density and mortality rate of rabbits. Rabbits stocked at 6.7 to 13.3 rabbits/m2 had significantly higher body condition score and fur condition compared with those stocked at 16.7 and 20 rabbits/m2. There were no differences in fighty bites for all the stocking densities. It is concluded from this study that the optimum stocking density for rabbits in the semi-humid tropics is 13.3 rabbits/m2.

Soliton–antisoliton interaction in a parametrically driven easy-plane magnetic wire

Energy Technology Data Exchange (ETDEWEB)

Urzagasti, D., E-mail: deterlino@yahoo.com [Instituto de Investigaciones Físicas, UMSA, P.O. Box 8635, La Paz (Bolivia, Plurinational State of); Aramayo, A. [Instituto de Investigaciones Físicas, UMSA, P.O. Box 8635, La Paz (Bolivia, Plurinational State of); Laroze, D. [Instituto de Alta Investigación, Universidad de Tarapacá, Casilla 7D, Arica (Chile); Max Planck Institute for Polymer Research, 55021 Mainz (Germany)

2014-07-11

In the present work we study the soliton–antisoliton interaction in an anisotropic easy-plane magnetic wire forced by a transverse uniform and oscillatory magnetic field. This system is described in the continuous framework by the Landau–Lifshitz–Gilbert equation. We find numerically that the spatio-temporal magnetization field exhibits both annihilative and repulsive soliton–antisoliton interactions. We also describe this system with the aim of the associated Parametrically Driven and Damped Nonlinear Schrödinger amplitude equation and give an approximate analytical solution that roughly describes the repulsive interaction. - Highlights: • We study the interactions of solitons with opposite polarity with the LLG equation. • We found that there exists both annihilative and repulsive interactions. • Similar results we found for the Parametrically Driven and Damped NLS equation. • We obtain an approximate analytical solution for the repulsive interaction.

Explicit free parametrization of the modified tetrahedron equation

CERN Document Server

Gehlen, G V; Sergeev, S

2003-01-01

The modified tetrahedron equation (MTE) with affine Weyl quantum variables at the Nth root of unity is solved by a rational mapping operator which is obtained from the solution of a linear problem. We show that the solutions can be parametrized in terms of eight free parameters and 16 discrete phase choices, thus providing a broad starting point for the construction of three-dimensional integrable lattice models. The Fermat-curve points parametrizing the representation of the mapping operator in terms of cyclic functions are expressed in terms of the independent parameters. An explicit formula for the density factor of the MTE is derived. For the example N=2 we write the MTE in full detail.

Explicit free parametrization of the modified tetrahedron equation

International Nuclear Information System (INIS)

Gehlen, G von; Pakuliak, S; Sergeev, S

2003-01-01

The modified tetrahedron equation (MTE) with affine Weyl quantum variables at the Nth root of unity is solved by a rational mapping operator which is obtained from the solution of a linear problem. We show that the solutions can be parametrized in terms of eight free parameters and 16 discrete phase choices, thus providing a broad starting point for the construction of three-dimensional integrable lattice models. The Fermat-curve points parametrizing the representation of the mapping operator in terms of cyclic functions are expressed in terms of the independent parameters. An explicit formula for the density factor of the MTE is derived. For the example N=2 we write the MTE in full detail

Dunkl Generalization of q-Parametric Szasz-Mirakjan Operators

Directory of Open Access Journals (Sweden)

M. Mursaleen

2017-03-01

Full Text Available In this paper, we construct q-parametric Szász-Mirakjan operators generated by the q-Dunkl generalization of the exponential function. We obtain Korovkin’s type approximation theorem and compute convergence of these operators by using the modulus of continuity. Furthermore, we obtain the rate of convergence of these operators for functions belonging to the Lipschitz class.

Electron density of states in a one-dimensional distorted system with impurities: Coherent potential approximation

International Nuclear Information System (INIS)

Bulka, B.R.

1982-04-01

A tight-binding one-dimensional distorted system with impurities is considered and the electron density of states is calculated in the coherent potential approximation. It is shown that two types of impurities, an impurity built in a chain and a domain wall (a soliton), play the essential role and a drastic reduction of the energy gap is observed for a few per cent of impurities. The experimental situation in polyacetylene is also discussed. (author)

Comparison between linear and non-parametric regression models for genome-enabled prediction in wheat.

Science.gov (United States)

Pérez-Rodríguez, Paulino; Gianola, Daniel; González-Camacho, Juan Manuel; Crossa, José; Manès, Yann; Dreisigacker, Susanne

2012-12-01

In genome-enabled prediction, parametric, semi-parametric, and non-parametric regression models have been used. This study assessed the predictive ability of linear and non-linear models using dense molecular markers. The linear models were linear on marker effects and included the Bayesian LASSO, Bayesian ridge regression, Bayes A, and Bayes B. The non-linear models (this refers to non-linearity on markers) were reproducing kernel Hilbert space (RKHS) regression, Bayesian regularized neural networks (BRNN), and radial basis function neural networks (RBFNN). These statistical models were compared using 306 elite wheat lines from CIMMYT genotyped with 1717 diversity array technology (DArT) markers and two traits, days to heading (DTH) and grain yield (GY), measured in each of 12 environments. It was found that the three non-linear models had better overall prediction accuracy than the linear regression specification. Results showed a consistent superiority of RKHS and RBFNN over the Bayesian LASSO, Bayesian ridge regression, Bayes A, and Bayes B models.

Absolute differential yield of parametric x-ray radiation

International Nuclear Information System (INIS)

Shchagin, A.V.; Pristupa, V.I.; Khizhnyak, N.A.

1993-01-01

The results of measurements of absolute differential yield of parametric X-ray radiation (PXR) in thin single crystal are presented for the first time. It has been established that the experimental results are in good agreement with theoretical calculations according with kinematical theory. The influence of density effect on PXR properties is discussed. (author). 19 refs., 7 figs

Parametric dependences of momentum pinch and Prandtl number in JET

NARCIS (Netherlands)

Tala, T.; Salmi, A.; Angioni, C.; Casson, F. J.; Corrigan, G.; Ferreira, J.; Giroud, C.; Mantica, P.; Naulin, V.; Peeters, A.G.; Solomon, W. M.; Strintzi, D.; Tsalas, M.; Versloot, T. W.; de Vries, P. C.; Zastrow, K. D.

2011-01-01

Several parametric scans have been performed to study momentum transport on JET. A neutral beam injection modulation technique has been applied to separate the diffusive and convective momentum transport terms. The magnitude of the inward momentum pinch depends strongly on the inverse density

Demographics and practices of semi-intensive free-range farming systems in Australia with an outdoor stocking density of ≤1500 hens/hectare

OpenAIRE

Singh, Mini; Ruhnke, Isabelle; de Koning, Carolyn; Drake, Kelly; Skerman, Alan G.; Hinch, Geoff N.; Glatz, Philip C.

2017-01-01

Baseline information on demographics and practices on semi-intensive free-range egg farms with an outdoor stocking density of ≤1500 hens/hectare in Australia is presented. Free-range egg production is changing the structure of the egg industry in Australia and a broad variety and tiers of free-range systems have emerged due to lack of concrete legislative standards on outdoor stocking densities in the past. Information was extracted from a pre-existing online free-range poultry survey dataset...

Communication: Random phase approximation renormalized many-body perturbation theory

International Nuclear Information System (INIS)

Bates, Jefferson E.; Furche, Filipp

2013-01-01

We derive a renormalized many-body perturbation theory (MBPT) starting from the random phase approximation (RPA). This RPA-renormalized perturbation theory extends the scope of single-reference MBPT methods to small-gap systems without significantly increasing the computational cost. The leading correction to RPA, termed the approximate exchange kernel (AXK), substantially improves upon RPA atomization energies and ionization potentials without affecting other properties such as barrier heights where RPA is already accurate. Thus, AXK is more balanced than second-order screened exchange [A. Grüneis et al., J. Chem. Phys. 131, 154115 (2009)], which tends to overcorrect RPA for systems with stronger static correlation. Similarly, AXK avoids the divergence of second-order Møller-Plesset (MP2) theory for small gap systems and delivers a much more consistent performance than MP2 across the periodic table at comparable cost. RPA+AXK thus is an accurate, non-empirical, and robust tool to assess and improve semi-local density functional theory for a wide range of systems previously inaccessible to first-principles electronic structure calculations

Effects of quadratic and cubic nonlinearities on a perfectly tuned parametric amplifier

DEFF Research Database (Denmark)

Neumeyer, Stefan; Sorokin, Vladislav; Thomsen, Jon Juel

2016-01-01

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...

Pairing in the BCS and LN approximations using continuum single particle level density

International Nuclear Information System (INIS)

Id Betan, R.M.; Repetto, C.E.

2017-01-01

Understanding the properties of drip line nuclei requires to take into account the correlations with the continuum spectrum of energy of the system. This paper has the purpose to show that the continuum single particle level density is a convenient way to consider the pairing correlation in the continuum. Isospin mean-field and isospin pairing strength are used to find the Bardeen–Cooper–Schrieffer (BCS) and Lipkin–Nogami (LN) approximate solutions of the pairing Hamiltonian. Several physical properties of the whole chain of the Tin isotope, as gap parameter, Fermi level, binding energy, and one- and two-neutron separation energies, were calculated and compared with other methods and with experimental data when they exist. It is shown that the use of the continuum single particle level density is an economical way to include explicitly the correlations with the continuum spectrum of energy in large scale mass calculation. It is also shown that the computed properties are in good agreement with experimental data and with more sophisticated treatment of the pairing interaction.

Parametric study of lower-hybrid current drive in the FED-A design

International Nuclear Information System (INIS)

Iida, H.; Ehst, D.A.; Peng, Y.K.M.

1983-08-01

In the FED-A concept, a quasi-steady-state operating scenario is conceived in which the plasma current is maintained by the transformer coil during burn at high density and by the lower hybrid wave during transformer recharge at low density. A parametric study is carried out to obtain optimum plasma and wave parameters in the recharging phase

Function parametrization by using 4-point transforms

International Nuclear Information System (INIS)

Dikusar, N.D.

1996-01-01

A continuous parametrization of the smooth curve f(x)=f(x;R) is suggested on a basis of four-point transformations. Coordinates of three reference points of the curve are chosen as parameters R. This approach allows to derive a number of advantages in function approximation and fitting of empiric data. The transformations have made possible to derive a new class of polynomials (monosplines) having the better approximation quality than monomials {x n }. A behaviour of an error of the approximation has a uniform character. A three-point model of the cubic spline (TPS) is proposed. The model allows to reduce a number of unknown parameters in twice and to obtain an advantage in a computing aspect. The new approach to the function approximation and fitting are shown on a number of examples. The proposed approach gives a new mathematical tool and a new possibility in both practical applications and theoretical research of numerical and computational methods. 13 refs., 13 figs., 2 tabs

Existence theorem and optimality conditions for a class of convex semi-infinite problems with noncompact index sets

Directory of Open Access Journals (Sweden)

Olga Kostyukova

2017-11-01

Full Text Available The paper is devoted to study of a special class of semi-infinite problems arising in nonlinear parametric Semi-infinite Programming, when the differential properties of the solutions are being studied. These problems are convex and possess noncompact index sets. In the paper, we present conditions guaranteeing the existence of optimal solutions, and prove new optimality criterion. An example illustrating the obtained results is presented.

Non-Intrusive Solution of Stochastic and Parametric Equations

KAUST Repository

Matthies, Hermann

2015-01-07

Many problems depend on parameters, which may be a finite set of numerical values, or mathematically more complicated objects like for example processes or fields. We address the situation where we have an equation which depends on parameters; stochastic equations are a special case of such parametric problems where the parameters are elements from a probability space. One common way to represent this dependability on parameters is by evaluating the state (or solution) of the system under investigation for different values of the parameters. But often one wants to evaluate the solution quickly for a new set of parameters where it has not been sampled. In this situation it may be advantageous to express the parameter dependent solution with an approximation which allows for rapid evaluation of the solution. Such approximations are also called proxy or surrogate models, response functions, or emulators. All these methods may be seen as functional approximations—representations of the solution by an “easily computable” function of the parameters, as opposed to pure samples. The most obvious methods of approximation used are based on interpolation, in this context often labelled as collocation. In the frequent situation where one has a “solver” for the equation for a given parameter value, i.e. a software component or a program, it is evident that this can be used to independently—if desired in parallel—solve for all the parameter values which subsequently may be used either for the interpolation or in the quadrature for the projection. Such methods are therefore uncoupled for each parameter value, and they additionally often carry the label “non-intrusive”. Without much argument all other methods— which produce a coupled system of equations–are almost always labelled as “intrusive”, meaning that one cannot use the original solver. We want to show here that this not necessarily the case. Another approach is to choose some other projection onto

Non-Intrusive Solution of Stochastic and Parametric Equations

KAUST Repository

Matthies, Hermann

2015-01-01

Many problems depend on parameters, which may be a finite set of numerical values, or mathematically more complicated objects like for example processes or fields. We address the situation where we have an equation which depends on parameters; stochastic equations are a special case of such parametric problems where the parameters are elements from a probability space. One common way to represent this dependability on parameters is by evaluating the state (or solution) of the system under investigation for different values of the parameters. But often one wants to evaluate the solution quickly for a new set of parameters where it has not been sampled. In this situation it may be advantageous to express the parameter dependent solution with an approximation which allows for rapid evaluation of the solution. Such approximations are also called proxy or surrogate models, response functions, or emulators. All these methods may be seen as functional approximations—representations of the solution by an “easily computable” function of the parameters, as opposed to pure samples. The most obvious methods of approximation used are based on interpolation, in this context often labelled as collocation. In the frequent situation where one has a “solver” for the equation for a given parameter value, i.e. a software component or a program, it is evident that this can be used to independently—if desired in parallel—solve for all the parameter values which subsequently may be used either for the interpolation or in the quadrature for the projection. Such methods are therefore uncoupled for each parameter value, and they additionally often carry the label “non-intrusive”. Without much argument all other methods— which produce a coupled system of equations–are almost always labelled as “intrusive”, meaning that one cannot use the original solver. We want to show here that this not necessarily the case. Another approach is to choose some other projection onto

Parametrization of the scattering wave functions of the Paris potential

International Nuclear Information System (INIS)

Loiseau, B.; Mathelitsch, L.

1996-10-01

The neutron-proton scattering wave functions of the Paris nucleon-nucleon potential are parametrized for partial waves of total angular momenta less than 5. The inner parts of the wave functions are approximated by polynomials with a continuous transition to the outer parts, which are given by the asymptotic regime and determined by the respective phase shifts. The scattering wave functions can then be calculated at any given energy below 400 MeV. Special attention is devoted to the zero-energy limit of the low partial waves. An easy-to-use FORTRAN program, which allows the user to calculate these parametrized wave functions, is available via electronic mail. (author)

Density forecasts of crude-oil prices using option-implied and ARCH-type models

DEFF Research Database (Denmark)

Høg, Esben; Tsiaras, Leonicas

2011-01-01

of derivative contracts. Risk-neutral densities, obtained from panels of crude-oil option prices, are adjusted to reflect real-world risks using either a parametric or a non-parametric calibration approach. The relative performance of the models is evaluated for the entire support of the density, as well...... obtained by option prices and non-parametric calibration methods over those constructed using historical returns and simulated ARCH processes. © 2010 Wiley Periodicals, Inc. Jrl Fut Mark...

Demographics and practices of semi-intensive free-range farming systems in Australia with an outdoor stocking density of ≤1500 hens/hectare.

Science.gov (United States)

Singh, Mini; Ruhnke, Isabelle; de Koning, Carolyn; Drake, Kelly; Skerman, Alan G; Hinch, Geoff N; Glatz, Philip C

2017-01-01

Baseline information on demographics and practices on semi-intensive free-range egg farms with an outdoor stocking density of ≤1500 hens/hectare in Australia is presented. Free-range egg production is changing the structure of the egg industry in Australia and a broad variety and tiers of free-range systems have emerged due to lack of concrete legislative standards on outdoor stocking densities in the past. Information was extracted from a pre-existing online free-range poultry survey dataset, consisting of a total of 79 questions related to nutrition, pasture management, welfare and health, animal housing, environmental impact and economics. Forty-one free-range egg farms, with an outdoor stocking density of ≤1500 hens/hectare, were identified in the dataset from all major Australian states. Two types of semi-intensive free-range housing systems were documented: mobile (modified caravan/trailer) housing (56%), and fixed sheds (44%). Seventy-two percent of respondents reported >75% of the hens in the flock used the outdoor range. All respondents reported ingestion of range components by hens in the form of vegetation, insects, stones and grit. Up to 10% mortality was reported by 40% respondents with predation (34%), cannibalism (29%), heat stress (24%) and grass impaction (19.5%) as major causes. Biosecurity on farms was sub-optimal with 8 of the 10 actions implemented by free-range egg production. This study resulted in identification of current practices and key challenges on semi-intensive free-range egg farms. Applied research and communication of results to farmers is highly recommended to ensure optimum health and welfare of free-range laying hens and sustained egg production.

High-Power-Density, High-Energy-Density Fluorinated Graphene for Primary Lithium Batteries

Directory of Open Access Journals (Sweden)

Guiming Zhong

2018-03-01

Full Text Available Li/CFx is one of the highest-energy-density primary batteries; however, poor rate capability hinders its practical applications in high-power devices. Here we report a preparation of fluorinated graphene (GFx with superior performance through a direct gas fluorination method. We find that the so-called “semi-ionic” C-F bond content in all C-F bonds presents a more critical impact on rate performance of the GFx in comparison with sp2 C content in the GFx, morphology, structure, and specific surface area of the materials. The rate capability remains excellent before the semi-ionic C-F bond proportion in the GFx decreases. Thus, by optimizing semi-ionic C-F content in our GFx, we obtain the optimal x of 0.8, with which the GF0.8 exhibits a very high energy density of 1,073 Wh kg−1 and an excellent power density of 21,460 W kg−1 at a high current density of 10 A g−1. More importantly, our approach opens a new avenue to obtain fluorinated carbon with high energy densities without compromising high power densities.

Machine learning-based dual-energy CT parametric mapping.

Science.gov (United States)

Su, Kuan-Hao; Kuo, Jung-Wen; Jordan, David W; Van Hedent, Steven; Klahr, Paul; Wei, Zhouping; Al Helo, Rose; Liang, Fan; Qian, Pengjiang; Pereira, Gisele C; Rassouli, Negin; Gilkeson, Robert C; Traughber, Bryan J; Cheng, Chee-Wai; Muzic, Raymond F

2018-05-22

The aim is to develop and evaluate machine learning methods for generating quantitative parametric maps of effective atomic number (Z_eff), relative electron density (ρ_e), mean excitation energy (I_x), and relative stopping power (RSP) from clinical dual-energy CT data. The maps could be used for material identification and radiation dose calculation. Machine learning methods of historical centroid (HC), random forest (RF), and artificial neural networks (ANN) were used to learn the relationship between dual-energy CT input data and ideal output parametric maps calculated for phantoms from the known compositions of 13 tissue substitutes. After training and model selection steps, the machine learning predictors were used to generate parametric maps from independent phantom and patient input data. Precision and accuracy were evaluated using the ideal maps. This process was repeated for a range of exposure doses, and performance was compared to that of the clinically-used dual-energy, physics-based method which served as the reference. The machine learning methods generated more accurate and precise parametric maps than those obtained using the reference method. Their performance advantage was particularly evident when using data from the lowest exposure, one-fifth of a typical clinical abdomen CT acquisition. The RF method achieved the greatest accuracy. In comparison, the ANN method was only 1% less accurate but had much better computational efficiency than RF, being able to produce parametric maps in 15 seconds. Machine learning methods outperformed the reference method in terms of accuracy and noise tolerance when generating parametric maps, encouraging further exploration of the techniques. Among the methods we evaluated, ANN is the most suitable for clinical use due to its combination of accuracy, excellent low-noise performance, and computational efficiency. . © 2018 Institute of Physics and Engineering in

Parametric instability analysis of truncated conical shells using the Haar wavelet method

Science.gov (United States)

Dai, Qiyi; Cao, Qingjie

2018-05-01

In this paper, the Haar wavelet method is employed to analyze the parametric instability of truncated conical shells under static and time dependent periodic axial loads. The present work is based on the Love first-approximation theory for classical thin shells. The displacement field is expressed as the Haar wavelet series in the axial direction and trigonometric functions in the circumferential direction. Then the partial differential equations are reduced into a system of coupled Mathieu-type ordinary differential equations describing dynamic instability behavior of the shell. Using Bolotin's method, the first-order and second-order approximations of principal instability regions are determined. The correctness of present method is examined by comparing the results with those in the literature and very good agreement is observed. The difference between the first-order and second-order approximations of principal instability regions for tensile and compressive loads is also investigated. Finally, numerical results are presented to bring out the influences of various parameters like static load factors, boundary conditions and shell geometrical characteristics on the domains of parametric instability of conical shells.

Coarse Grained Exponential Variational Autoencoders

KAUST Repository

Sun, Ke

2017-02-25

Variational autoencoders (VAE) often use Gaussian or category distribution to model the inference process. This puts a limit on variational learning because this simplified assumption does not match the true posterior distribution, which is usually much more sophisticated. To break this limitation and apply arbitrary parametric distribution during inference, this paper derives a \\\\emph{semi-continuous} latent representation, which approximates a continuous density up to a prescribed precision, and is much easier to analyze than its continuous counterpart because it is fundamentally discrete. We showcase the proposition by applying polynomial exponential family distributions as the posterior, which are universal probability density function generators. Our experimental results show consistent improvements over commonly used VAE models.

Physical mechanism of parametric instabilities near the lower-hybrid frequency in inhomogeneous plasma

International Nuclear Information System (INIS)

Porkolab, M.

1974-10-01

The dispersion relation for parametric instabilities near the lower-hybrid frequency is obtained from model fluid equations. The following instabilities are discussed: for rf pump frequencies ω 0 greater than or equal to 3ω/sub LH/, ω/sub pe/ approximately equal to Ω/sub e/, resonant decay into ion sound (ion cyclotron) modes (previously predicted) is found. In the regime of 1 less than or equal to ω 0 /ω/sub LH/ less than or equal to 3, ω/sub pe/ approximately equal to Ω/sub e/, decay into ion quasi-modes is found. In strong magnetic fields decay into quasi-modes is also found for 3 less than or equal to ω 0 /ω/sub LH/. This mechanism is similar to nonlinear Landau damping in weak turbulence theory. In addition, decay into the purely growing mode and fluid-quasi modes may also occur. The results are compared with recent calculations from the Vlasov equation. The effects of plasma-inhomogeneities are considered, including effective thresholds due to density gradients and finite pump extent. The implications of these results to rf heating of tokamaks near the lower-hybrid frequency are discussed. (auth)

What semi-inclusive data say about clusters

International Nuclear Information System (INIS)

Arneodo, A.; Plaut, G.

1976-01-01

A global analysis of inclusive high-energy multi-particle production data in the cluster model framework is extended to semi-inclusive data. The cluster model embodies leading particle effects and kinematical constraints, which are shown to be of great importance. It appears that models with light clusters decaying on average into approximately equal to 2 charged particles, with a rapidity width delta approximately equal to 0.6 - 0.7 and a distribution much narrower than a Poisson-type, allow one to fit in a nice way both inclusive and semi-inclusive data. It is pointed out that the most constraining semi-inclusive data are those regarding longitudinal correlations, which definitely exclude heavy cluster models, whereas the data on zone characteristics only bear out that a non-negligible percentage of clusters have to carry an electric charge. (Auth.)

Comparison of parametric and bootstrap method in bioequivalence test.

Science.gov (United States)

Ahn, Byung-Jin; Yim, Dong-Seok

2009-10-01

The estimation of 90% parametric confidence intervals (CIs) of mean AUC and Cmax ratios in bioequivalence (BE) tests are based upon the assumption that formulation effects in log-transformed data are normally distributed. To compare the parametric CIs with those obtained from nonparametric methods we performed repeated estimation of bootstrap-resampled datasets. The AUC and Cmax values from 3 archived datasets were used. BE tests on 1,000 resampled datasets from each archived dataset were performed using SAS (Enterprise Guide Ver.3). Bootstrap nonparametric 90% CIs of formulation effects were then compared with the parametric 90% CIs of the original datasets. The 90% CIs of formulation effects estimated from the 3 archived datasets were slightly different from nonparametric 90% CIs obtained from BE tests on resampled datasets. Histograms and density curves of formulation effects obtained from resampled datasets were similar to those of normal distribution. However, in 2 of 3 resampled log (AUC) datasets, the estimates of formulation effects did not follow the Gaussian distribution. Bias-corrected and accelerated (BCa) CIs, one of the nonparametric CIs of formulation effects, shifted outside the parametric 90% CIs of the archived datasets in these 2 non-normally distributed resampled log (AUC) datasets. Currently, the 80~125% rule based upon the parametric 90% CIs is widely accepted under the assumption of normally distributed formulation effects in log-transformed data. However, nonparametric CIs may be a better choice when data do not follow this assumption.

Quantitative ultrasound of the calcaneus with parametric imaging: correlation with bone mineral density at different sites and with anthropometric data in menopausal women

International Nuclear Information System (INIS)

Louis, O.; Kaufman, L.; Osteaux, M.

2000-01-01

Objective: To prospectively study the relationship of quantitative ultrasound of the calcaneus with anthromopometric variables and with bone mineral density (BMD) assessed at the level of the calcaneus as well as at other sites. Method: Osteosonography of the non-dominant calcaneus was performed in 135 menopausal women, using a DTU-one device with parametric imaging. Broadband ultrasound attenuation (BUA) and speed of sound (SOS) were assessed. BMD of the calcaneus (BMDcal) was measured using dual energy X-ray absorptiometry (DXA), in a subregion matched with the region of interest for osteosonography. BMD of the lumbar trabecular bone was measured using quantitative computed tomography (BMD QCT) while the non-dominant hip was studied using DXA, which provided the total bone mineral density (BMDhip) and that of the Ward triangle (BMDWard). Results: The Pearson correlation coefficients between BUA, SOS and the various measurements of BMD ranged from 0.305 (SOS versus BMDhip) to 0.717 (BUA versus BMDcal). BMD QCT and BMDWard were found to depend on age, but not on weight or height, while BUA, SOS, BMDcal, BMDhip were unrelated to age, but correlated with weight (SOS, BMDhip) or with weight and height (BUA, BMDcal). In a multiple stepwise regression analysis, age was a significant predictor for BMD QCT, BMD hip and BMDWard; BMD QCT, BMDWard and BMDhip admitted BUA as sole predictor, while BMDcal was significantly related to both BUA and SOS. Conclusion: BUA and SOS of the calcaneus, assessed in 135 menopausal women using a parametric imaging device, reflected BMDcal, measured with DXA at a matched region of interest, and did not decline significantly with age

Quantitative ultrasound of the calcaneus with parametric imaging: correlation with bone mineral density at different sites and with anthropometric data in menopausal women

Energy Technology Data Exchange (ETDEWEB)

Louis, O.; Kaufman, L.; Osteaux, M

2000-07-01

Objective: To prospectively study the relationship of quantitative ultrasound of the calcaneus with anthromopometric variables and with bone mineral density (BMD) assessed at the level of the calcaneus as well as at other sites. Method: Osteosonography of the non-dominant calcaneus was performed in 135 menopausal women, using a DTU-one device with parametric imaging. Broadband ultrasound attenuation (BUA) and speed of sound (SOS) were assessed. BMD of the calcaneus (BMDcal) was measured using dual energy X-ray absorptiometry (DXA), in a subregion matched with the region of interest for osteosonography. BMD of the lumbar trabecular bone was measured using quantitative computed tomography (BMD QCT) while the non-dominant hip was studied using DXA, which provided the total bone mineral density (BMDhip) and that of the Ward triangle (BMDWard). Results: The Pearson correlation coefficients between BUA, SOS and the various measurements of BMD ranged from 0.305 (SOS versus BMDhip) to 0.717 (BUA versus BMDcal). BMD QCT and BMDWard were found to depend on age, but not on weight or height, while BUA, SOS, BMDcal, BMDhip were unrelated to age, but correlated with weight (SOS, BMDhip) or with weight and height (BUA, BMDcal). In a multiple stepwise regression analysis, age was a significant predictor for BMD QCT, BMD hip and BMDWard; BMD QCT, BMDWard and BMDhip admitted BUA as sole predictor, while BMDcal was significantly related to both BUA and SOS. Conclusion: BUA and SOS of the calcaneus, assessed in 135 menopausal women using a parametric imaging device, reflected BMDcal, measured with DXA at a matched region of interest, and did not decline significantly with age.

Parametric Sensitivity Tests- European PEM Fuel Cell Stack Test Procedures

DEFF Research Database (Denmark)

Araya, Samuel Simon; Andreasen, Søren Juhl; Kær, Søren Knudsen

2014-01-01

performed based on test procedures proposed by a European project, Stack-Test. The sensitivity of a Nafion-based low temperature PEMFC stack’s performance to parametric changes was the main objective of the tests. Four crucial parameters for fuel cell operation were chosen; relative humidity, temperature......As fuel cells are increasingly commercialized for various applications, harmonized and industry-relevant test procedures are necessary to benchmark tests and to ensure comparability of stack performance results from different parties. This paper reports the results of parametric sensitivity tests......, pressure, and stoichiometry at varying current density. Furthermore, procedures for polarization curve recording were also tested both in ascending and descending current directions....

Demographics and practices of semi-intensive free-range farming systems in Australia with an outdoor stocking density of ≤1500 hens/hectare.

Directory of Open Access Journals (Sweden)

Mini Singh

Full Text Available Baseline information on demographics and practices on semi-intensive free-range egg farms with an outdoor stocking density of ≤1500 hens/hectare in Australia is presented. Free-range egg production is changing the structure of the egg industry in Australia and a broad variety and tiers of free-range systems have emerged due to lack of concrete legislative standards on outdoor stocking densities in the past. Information was extracted from a pre-existing online free-range poultry survey dataset, consisting of a total of 79 questions related to nutrition, pasture management, welfare and health, animal housing, environmental impact and economics. Forty-one free-range egg farms, with an outdoor stocking density of ≤1500 hens/hectare, were identified in the dataset from all major Australian states. Two types of semi-intensive free-range housing systems were documented: mobile (modified caravan/trailer housing (56%, and fixed sheds (44%. Seventy-two percent of respondents reported >75% of the hens in the flock used the outdoor range. All respondents reported ingestion of range components by hens in the form of vegetation, insects, stones and grit. Up to 10% mortality was reported by 40% respondents with predation (34%, cannibalism (29%, heat stress (24% and grass impaction (19.5% as major causes. Biosecurity on farms was sub-optimal with 8 of the 10 actions implemented by <50% respondents. Customer demand, consumer sentiment and welfare were the major factors for farmers moving into free-range egg production. This study resulted in identification of current practices and key challenges on semi-intensive free-range egg farms. Applied research and communication of results to farmers is highly recommended to ensure optimum health and welfare of free-range laying hens and sustained egg production.

Semi adiabatic theory of seasonal Markov processes

Energy Technology Data Exchange (ETDEWEB)

Talkner, P [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1999-08-01

The dynamics of many natural and technical systems are essentially influenced by a periodic forcing. Analytic solutions of the equations of motion for periodically driven systems are generally not known. Simulations, numerical solutions or in some limiting cases approximate analytic solutions represent the known approaches to study the dynamics of such systems. Besides the regime of weak periodic forces where linear response theory works, the limit of a slow driving force can often be treated analytically using an adiabatic approximation. For this approximation to hold all intrinsic processes must be fast on the time-scale of a period of the external driving force. We developed a perturbation theory for periodically driven Markovian systems that covers the adiabatic regime but also works if the system has a single slow mode that may even be slower than the driving force. We call it the semi adiabatic approximation. Some results of this approximation for a system exhibiting stochastic resonance which usually takes place within the semi adiabatic regime are indicated. (author) 1 fig., 8 refs.

Error Decomposition and Adaptivity for Response Surface Approximations from PDEs with Parametric Uncertainty

KAUST Repository

Bryant, C. M.; Prudhomme, S.; Wildey, T.

2015-01-01

In this work, we investigate adaptive approaches to control errors in response surface approximations computed from numerical approximations of differential equations with uncertain or random data and coefficients. The adaptivity of the response surface approximation is based on a posteriori error estimation, and the approach relies on the ability to decompose the a posteriori error estimate into contributions from the physical discretization and the approximation in parameter space. Errors are evaluated in terms of linear quantities of interest using adjoint-based methodologies. We demonstrate that a significant reduction in the computational cost required to reach a given error tolerance can be achieved by refining the dominant error contributions rather than uniformly refining both the physical and stochastic discretization. Error decomposition is demonstrated for a two-dimensional flow problem, and adaptive procedures are tested on a convection-diffusion problem with discontinuous parameter dependence and a diffusion problem, where the diffusion coefficient is characterized by a 10-dimensional parameter space.

A Non-Structural Investigation of VIX Risk Neutral Density

DEFF Research Database (Denmark)

Barletta, Andrea; Santucci de Magistris, Paolo; Violante, Francesco

We propose a non-structural pricing method to derive the risk-neutral density (RND) implied by options on the CBOE Volatility Index (VIX). The methodology is based on orthogonal polynomial expansions around a kernel density and yields the RND of the underlying asset without the need for a paramet......We propose a non-structural pricing method to derive the risk-neutral density (RND) implied by options on the CBOE Volatility Index (VIX). The methodology is based on orthogonal polynomial expansions around a kernel density and yields the RND of the underlying asset without the need...... for a parametric specification. The classic family of Laguerre expansions is extended to include the GIG and the generalized Weibull kernels, thus relaxing the conditions required on the tail decay rate of the RND to ensure convergence. We show that the proposed methodology yields an accurate approximation...... of the RND in a large variety of cases, also when the no-arbitrage and efficient option prices are contaminated by measurement errors. Our empirical investigation, based on a panel of traded VIX options, reveals some stylized facts on the RND of VIX. We find that a common stochastic factor drives the dynamic...

On the accuracy of Rüger's approximation for reflection coefficients in HTI media: implications for the determination of fracture density and orientation from seismic AVAZ data

International Nuclear Information System (INIS)

Ali, Aamir; Jakobsen, Morten

2011-01-01

We have investigated the accuracy of Rüger's approximation for PP reflection coefficients in HTI media (relative to an exact generalization of Zoeppritz to anisotropy derived by Schoenberg and Protazio) within the context of seismic fracture characterization. We consider the inverse problem of seismic amplitude-versus-angle and azimuth (AVAZ) inversion with respect to fracture density and azimuthal fracture orientation, as well as the forward problem of calculating PP reflection coefficients for different contrasts and anisotropy levels. The T-matrix approach was used to relate the contrast and anisotropy level to the parameters of the fractures (in the case of a single set of vertical fractures). We have found that Rüger's approximation can be used to recover the true fracture density with small uncertainty if, and only if, the fracture density and contrast are significantly smaller than the values that are believed to occur in many practically interesting cases of fractured (carbonate) reservoirs. In one example involving a minimal contrast and a fracture density in the range 0.05–0.1, Rüger's approximation performed satisfactorily for inversion, although the forward modelling results were not very accurate at high incident angles. But for fracture densities larger than 0.1 (which we believe may well occur in real cases), Rüger's approximation did not perform satisfactorily for forward or inverse modelling. However, it appears that Rüger's approximation can always be used to obtain estimates of the azimuthal fracture orientation with small uncertainty, even when the contrast and anisotropy levels are extremely large. In order to illustrate the significance of our findings within the context of seismic fracture characterization, we analysed a set of synthetic seismic AVAZ data associated with a fault facies model where the fracture density decreases exponentially with distance from the fault core, and a set of real seismic AVAZ data involving offset

Analysis of the Behaviour of Semi Rigid Steel End Plate Connections

Directory of Open Access Journals (Sweden)

Bahaz A.

2018-01-01

Full Text Available The analysis of steel-framed building structures with full strength beam to column joints is quite standard nowadays. Buildings utilizing such framing systems are widely used in design practice. However, there is a growing recognition of significant benefits in designing joints as partial strength/semi-rigid. The design of joints within this partial strength/semi-rigid approach is becoming more and more popular. This requires the knowledge of the full nonlinear moment-rotation behaviour of the joint, which is also a design parameter. The rotational behaviour of steel semi rigid connections can be studied using the finite element method for the following three reasons: i such models are inexpensive; ii they allow the understanding of local effects, which are difficult to measure accurately physically, and iii they can be used to generate extensive parametric studies. This paper presents a three-dimensional finite element model using ABAQUS software in order to identify the effect of different parameters on the behaviour of semi rigid steel beam to column end plate connections. Contact and sliding between different elements, bolt pretension and geometric and material non-linearity are included in this model. A parametric study is conducted using a model of two end-plate configurations: flush and extended end plates. The studied parameters were as follows: bolts type, end plate thickness and column web stiffener. Then, the model was calibrated and validated with experimental results taken from the literature and with the model proposed by Eurocode3. The procedure for determining the moment–rotation curve using finite element analysis is also given together with a brief explanation of how the design moment resistance and the initial rotational stiffness of the joint are obtained.

Sgr A* Emission Parametrizations from GRMHD Simulations

Science.gov (United States)

Anantua, Richard; Ressler, Sean; Quataert, Eliot

2018-06-01

Galactic Center emission near the vicinity of the central black hole, Sagittarius (Sgr) A*, is modeled using parametrizations involving the electron temperature, which is found from general relativistic magnetohydrodynamic (GRMHD) simulations to be highest in the disk-outflow corona. Jet-motivated prescriptions generalizing equipartition of particle and magnetic energies, e.g., by scaling relativistic electron energy density to powers of the magnetic field strength, are also introduced. GRMHD jet (or outflow)/accretion disk/black hole (JAB) simulation postprocessing codes IBOTHROS and GRMONTY are employed in the calculation of images and spectra. Various parametric models reproduce spectral and morphological features, such as the sub-mm spectral bump in electron temperature models and asymmetric photon rings in equipartition-based models. The Event Horizon Telescope (EHT) will provide unprecedentedly high-resolution 230+ GHz observations of the "shadow" around Sgr A*'s supermassive black hole, which the synthetic models presented here will reverse-engineer. Both electron temperature and equipartition-based models can be constructed to be compatible with EHT size constraints for the emitting region of Sgr A*. This program sets the groundwork for devising a unified emission parametrization flexible enough to model disk, corona and outflow/jet regions with a small set of parameters including electron heating fraction and plasma beta.

Atomic Cholesky decompositions: A route to unbiased auxiliary basis sets for density fitting approximation with tunable accuracy and efficiency

Science.gov (United States)

Aquilante, Francesco; Gagliardi, Laura; Pedersen, Thomas Bondo; Lindh, Roland

2009-04-01

Cholesky decomposition of the atomic two-electron integral matrix has recently been proposed as a procedure for automated generation of auxiliary basis sets for the density fitting approximation [F. Aquilante et al., J. Chem. Phys. 127, 114107 (2007)]. In order to increase computational performance while maintaining accuracy, we propose here to reduce the number of primitive Gaussian functions of the contracted auxiliary basis functions by means of a second Cholesky decomposition. Test calculations show that this procedure is most beneficial in conjunction with highly contracted atomic orbital basis sets such as atomic natural orbitals, and that the error resulting from the second decomposition is negligible. We also demonstrate theoretically as well as computationally that the locality of the fitting coefficients can be controlled by means of the decomposition threshold even with the long-ranged Coulomb metric. Cholesky decomposition-based auxiliary basis sets are thus ideally suited for local density fitting approximations.

Parametric approximation of airfoil aerodynamic coefficients at high angles of attack

DEFF Research Database (Denmark)

Skrzypinski, Witold Robert; Zahle, Frederik; Bak, Christian

2014-01-01

, and the third method, also utilizing trigonometric functions, was developed with the scope on stall-regulated turbines. The method of the even sine and cosine functions was further developed in the present work by using two independent harmonic approximations in the positive and negative α regions...

Primary damage in tungsten using the binary collision approximation, molecular dynamic simulations and the density functional theory

International Nuclear Information System (INIS)

De Backer, A; Sand, A; Ortiz, C J; Domain, C; Olsson, P; Berthod, E; Becquart, C S

2016-01-01

The damage produced by primary knock-on atoms (PKA) in W has been investigated from the threshold displacement energy (TDE) where it produces one self interstitial atom–vacancy pair to larger energies, up to 100 keV, where a large molten volume is formed. The TDE has been determined in different crystal directions using the Born–Oppenheimer density functional molecular dynamics (DFT-MD). A significant difference has been observed without and with the semi-core electrons. Classical MD has been used with two different empirical potentials characterized as ‘soft’ and ‘hard’ to obtain statistics on TDEs. Cascades of larger energy have been calculated, with these potentials, using a model that accounts for electronic losses (Sand et al 2013 Europhys. Lett. 103 46003). Two other sets of cascades have been produced using the binary collision approximation (BCA): a Monte Carlo BCA using SDTrimSP (Eckstein et al 2011 SDTrimSP: Version 5.00. Report IPP 12/8) (similar to SRIM www.srim.org) and MARLOWE (RSICC Home Page. (https://rsicc.ornl.gov/codes/psr/psr1/psr-137.html) (accessed May, 2014)). The comparison of these sets of cascades gave a recombination distance equal to 12 Å which is significantly larger from the one we reported in Hou et al (2010 J. Nucl. Mater. 403 89) because, here, we used bulk cascades rather than surface cascades which produce more defects (Stoller 2002 J. Nucl. Mater. 307 935, Nordlund et al 1999 Nature 398 49). Investigations on the defect clustering aspect showed that the difference between BCA and MD cascades is considerably reduced after the annealing of the cascade debris at 473 K using our Object Kinetic Monte Carlo model, LAKIMOCA (Domain et al 2004 J. Nucl. Mater. 335 121). (paper)

Parametric instabilities in shallow water magnetohydrodynamics of astrophysical plasma in external magnetic field

Energy Technology Data Exchange (ETDEWEB)

Klimachkov, D.A., E-mail: klimachkovdmitry@gmail.com [Space Research Institute of Russian Academy of Science, 84/32, Profsoyuznaya str., Moscow, 117997 (Russian Federation); Petrosyan, A.S. [Space Research Institute of Russian Academy of Science, 84/32, Profsoyuznaya str., Moscow, 117997 (Russian Federation); Moscow Institute of Physics and Technology (State University), 9 Institutskyi per., Dolgoprudny, Moscow Region, 141700 (Russian Federation)

2017-01-15

This article deals with magnetohydrodynamic (MHD) flows of a thin rotating layer of astrophysical plasma in external magnetic field. We use the shallow water approximation to describe thin rotating plasma layer with a free surface in a vertical external magnetic field. The MHD shallow water equations with external vertical magnetic field are revised by supplementing them with the equations that are consequences of the magnetic field divergence-free conditions and reveal the existence of third component of the magnetic field in such approximation providing its relation with the horizontal magnetic field. It is shown that the presence of a vertical magnetic field significantly changes the dynamics of the wave processes in astrophysical plasma compared to the neutral fluid and plasma layer in a toroidal magnetic field. The equations for the nonlinear wave packets interactions are derived using the asymptotic multiscale method. The equations for three magneto-Poincare waves interactions, for three magnetostrophic waves interactions, for the interactions of two magneto-Poincare waves and for one magnetostrophic wave and two magnetostrophic wave and one magneto-Poincare wave interactions are obtained. The existence of parametric decay and parametric amplifications is predicted. We found following four types of parametric decay instabilities: magneto-Poincare wave decays into two magneto-Poincare waves, magnetostrophic wave decays into two magnetostrophic waves, magneto-Poincare wave decays into one magneto-Poincare wave and one magnetostrophic wave, magnetostrophic wave decays into one magnetostrophic wave and one magneto-Poincare wave. Following mechanisms of parametric amplifications are found: parametric amplification of magneto-Poincare waves, parametric amplification of magnetostrophic waves, magneto-Poincare wave amplification in magnetostrophic wave presence and magnetostrophic wave amplification in magneto-Poincare wave presence. The instabilities growth rates

A minimax stochastic optimal semi-active control strategy for uncertain quasi-integrable Hamiltonian systems using magneto-rheological dampers

DEFF Research Database (Denmark)

Feng, Ju; Ying, Zu-Guang; Zhu, Wei-Qiu

2012-01-01

A minimax stochastic optimal semi-active control strategy for stochastically excited quasi-integrable Hamiltonian systems with parametric uncertainty by using magneto-rheological (MR) dampers is proposed. Firstly, the control problem is formulated as an n-degree-of-freedom (DOF) controlled, uncer...

A variational approach to parametric instabilities in inhomogeneous plasmas

Energy Technology Data Exchange (ETDEWEB)

Afeyan, B.B.

1993-12-31

A variational principle is constructed for the pump strength of a three-wave parametric instability in a spatially nonuniform medium. Using this expression together with appropriate trial functions, analytic estimates of the growth rate of the most unstable mode of a given parametric instability may be calculated. The usefullness of the variational method is first demonstrated on the Rosenbluth model problem with a power-law phase-mismatch, followed by a treatment of the Liu, Rosenbluth, and White sidescattering model equation. Two particular instabilities which are of interest in laser fusion and laser-plasma interaction experiments are treated next. These are Stimulated Raman Scattering and Two-Plasmon Decay. Various incidence and scattering geometries, and different density profiles are considered. Previously known results are reproduced in a unified manner and extended to cases where the usual local-expansion techniques do not apply. In particular, using the variational approach, the growth rate of the Two-Plasmon Decay instability occurring at or anywhere below the apex of a parabolic density profile is obtained for the first time. Similarly, Stimulated Raman Scattering from a density extremum at or anywhere below quarter critical, and for all scattering angles from backscattering to sidescattering inclusively is considered for the first time. The limit where the Two-Plasmon Decay and Stimulated Raman Scattering instabilities merge and become indistinguishable is also treated.

Ionospheric F2-Layer Semi-Annual Variation in Middle Latitude by Solar Activity

Directory of Open Access Journals (Sweden)

Yoon-Kyung Park

2010-12-01

Full Text Available We examine the ionospheric F2-layer electron density variation by solar activity in middle latitude by using foF2 observed at the Kokubunji ionosonde station in Japan for the period from 1997 to 2008. The semi-annual variation of foF2 shows obviously in high solar activity (2000-2002 than low solar activity (2006-2008. It seems that variation of geomagnetic activity by solar activity influences on the semi-annual variation of the ionospheric F2-layer electron density. According to the Lomb-Scargle periodogram analysis of foF2 and Ap index, interplanetary magnetic field (IMF Bs (IMF Bz <0 component, solar wind speed, solar wind number density and flow pressure which influence the geomagnetic activity, we examine how the geomagnetic activity affects the ionospheric F2-layer electron density variation. We find that the semi-annual variation of daily foF2, Ap index and IMF Bs appear clearly during the high solar activity. It suggests that the semi-annual variation of geomagnetic activity, caused by Russell-McPherron effect, contributes greatly to the ionospheric F2-layer semi-annual electron density variation, except dynamical effects in the thermosphere.

Constrained Convolutional Sparse Coding for Parametric Based Reconstruction of Line Drawings

KAUST Repository

Shaheen, Sara

2017-12-25

Convolutional sparse coding (CSC) plays an essential role in many computer vision applications ranging from image compression to deep learning. In this work, we spot the light on a new application where CSC can effectively serve, namely line drawing analysis. The process of drawing a line drawing can be approximated as the sparse spatial localization of a number of typical basic strokes, which in turn can be cast as a non-standard CSC model that considers the line drawing formation process from parametric curves. These curves are learned to optimize the fit between the model and a specific set of line drawings. Parametric representation of sketches is vital in enabling automatic sketch analysis, synthesis and manipulation. A couple of sketch manipulation examples are demonstrated in this work. Consequently, our novel method is expected to provide a reliable and automatic method for parametric sketch description. Through experiments, we empirically validate the convergence of our method to a feasible solution.

'LTE-diffusion approximation' for arc calculations

International Nuclear Information System (INIS)

Lowke, J J; Tanaka, M

2006-01-01

This paper proposes the use of the 'LTE-diffusion approximation' for predicting the properties of electric arcs. Under this approximation, local thermodynamic equilibrium (LTE) is assumed, with a particular mesh size near the electrodes chosen to be equal to the 'diffusion length', based on D e /W, where D e is the electron diffusion coefficient and W is the electron drift velocity. This approximation overcomes the problem that the equilibrium electrical conductivity in the arc near the electrodes is almost zero, which makes accurate calculations using LTE impossible in the limit of small mesh size, as then voltages would tend towards infinity. Use of the LTE-diffusion approximation for a 200 A arc with a thermionic cathode gives predictions of total arc voltage, electrode temperatures, arc temperatures and radial profiles of heat flux density and current density at the anode that are in approximate agreement with more accurate calculations which include an account of the diffusion of electric charges to the electrodes, and also with experimental results. Calculations, which include diffusion of charges, agree with experimental results of current and heat flux density as a function of radius if the Milne boundary condition is used at the anode surface rather than imposing zero charge density at the anode

Analysis of Nonlinear Dispersion of a Pollutant Ejected by an External Source into a Channel Flow

Directory of Open Access Journals (Sweden)

T. Chinyoka

2010-01-01

Full Text Available This paper focuses on the transient analysis of nonlinear dispersion of a pollutant ejected by an external source into a laminar flow of an incompressible fluid in a channel. The influence of density variation with pollutant concentration is approximated according to the Boussinesq approximation, and the nonlinear governing equations of momentum and pollutant concentration are obtained. The problem is solved numerically using a semi-implicit finite difference method. Solutions are presented in graphical form and given in terms of fluid velocity, pollutant concentration, skin friction, and wall mass transfer rate for various parametric values. The model can be a useful tool for understanding the polluting situations of an improper discharge incident and evaluating the effects of decontaminating measures for the water body.

Multi-parametric variational data assimilation for hydrological forecasting

Science.gov (United States)

Alvarado-Montero, R.; Schwanenberg, D.; Krahe, P.; Helmke, P.; Klein, B.

2017-12-01

Ensemble forecasting is increasingly applied in flow forecasting systems to provide users with a better understanding of forecast uncertainty and consequently to take better-informed decisions. A common practice in probabilistic streamflow forecasting is to force deterministic hydrological model with an ensemble of numerical weather predictions. This approach aims at the representation of meteorological uncertainty but neglects uncertainty of the hydrological model as well as its initial conditions. Complementary approaches use probabilistic data assimilation techniques to receive a variety of initial states or represent model uncertainty by model pools instead of single deterministic models. This paper introduces a novel approach that extends a variational data assimilation based on Moving Horizon Estimation to enable the assimilation of observations into multi-parametric model pools. It results in a probabilistic estimate of initial model states that takes into account the parametric model uncertainty in the data assimilation. The assimilation technique is applied to the uppermost area of River Main in Germany. We use different parametric pools, each of them with five parameter sets, to assimilate streamflow data, as well as remotely sensed data from the H-SAF project. We assess the impact of the assimilation in the lead time performance of perfect forecasts (i.e. observed data as forcing variables) as well as deterministic and probabilistic forecasts from ECMWF. The multi-parametric assimilation shows an improvement of up to 23% for CRPS performance and approximately 20% in Brier Skill Scores with respect to the deterministic approach. It also improves the skill of the forecast in terms of rank histogram and produces a narrower ensemble spread.

Radiographic diagnoses and treatment decisions on approximal caries

International Nuclear Information System (INIS)

Espelid, I.

1987-01-01

Mineral loss which represents a threshold value for radiographic diagnosis, cannot be defined exactly. For clinical use 10% mineral loss in the direction of the X-ray beam may constitute a border line lesion for radiographic detection, and caries lesions without cavitation seemed to be beyond this diagnostic threshold. The degree of caries estimated by using radiographs is fairly closely related to the depth of the tissue changes recorded in the prepared cavity. Radiographic examinations more often lead to underestimation than overestimation of the degree of caries. Radiographic caries diagnoses made at different degrees of penetration toward the pulp showed insignificant variations with respect to quality, but the observers were more confident of caries being present (used more strict criterion) when they scored caries in inner dentin. Consensus on diagnostic criteria and improved diagnostic quality are considerably more important to the quality of therapeutic decisions on approximal caries than viewing conditions and film density. A semi-radiopaque material in Class II fillings seems to offer advantages compared to amalgam in respect of the diagnosis of secondary caries and marginal defects. There is a danger that dentists will restore approximal caries lesions too early and before these can be diagnosed in dentin radiographically

Parametric Resonance in Dynamical Systems

CERN Document Server

Nijmeijer, Henk

2012-01-01

Parametric Resonance in Dynamical Systems discusses the phenomenon of parametric resonance and its occurrence in mechanical systems,vehicles, motorcycles, aircraft and marine craft, and micro-electro-mechanical systems. The contributors provide an introduction to the root causes of this phenomenon and its mathematical equivalent, the Mathieu-Hill equation. Also included is a discussion of how parametric resonance occurs on ships and offshore systems and its frequency in mechanical and electrical systems. This book also: Presents the theory and principles behind parametric resonance Provides a unique collection of the different fields where parametric resonance appears including ships and offshore structures, automotive vehicles and mechanical systems Discusses ways to combat, cope with and prevent parametric resonance including passive design measures and active control methods Parametric Resonance in Dynamical Systems is ideal for researchers and mechanical engineers working in application fields such as MEM...

Weighted Branching Simulation Distance for Parametric Weighted Kripke Structures

DEFF Research Database (Denmark)

Foshammer, Louise; Larsen, Kim Guldstrand; Mariegaard, Anders

2016-01-01

This paper concerns branching simulation for weighted Kripke structures with parametric weights. Concretely, we consider a weighted extension of branching simulation where a single transitions can be matched by a sequence of transitions while preserving the branching behavior. We relax this notion...... to allow for a small degree of deviation in the matching of weights, inducing a directed distance on states. The distance between two states can be used directly to relate properties of the states within a sub-fragment of weighted CTL. The problem of relating systems thus changes to minimizing the distance...... which, in the general parametric case, corresponds to finding suitable parameter valuations such that one system can approximately simulate another. Although the distance considers a potentially infinite set of transition sequences we demonstrate that there exists an upper bound on the length...

Sparse approximation of multilinear problems with applications to kernel-based methods in UQ

KAUST Repository

Nobile, Fabio; Tempone, Raul; Wolfers, Sö ren

2017-01-01

We provide a framework for the sparse approximation of multilinear problems and show that several problems in uncertainty quantification fit within this framework. In these problems, the value of a multilinear map has to be approximated using approximations of different accuracy and computational work of the arguments of this map. We propose and analyze a generalized version of Smolyak’s algorithm, which provides sparse approximation formulas with convergence rates that mitigate the curse of dimension that appears in multilinear approximation problems with a large number of arguments. We apply the general framework to response surface approximation and optimization under uncertainty for parametric partial differential equations using kernel-based approximation. The theoretical results are supplemented by numerical experiments.

Sparse approximation of multilinear problems with applications to kernel-based methods in UQ

KAUST Repository

Nobile, Fabio

2017-11-16

We provide a framework for the sparse approximation of multilinear problems and show that several problems in uncertainty quantification fit within this framework. In these problems, the value of a multilinear map has to be approximated using approximations of different accuracy and computational work of the arguments of this map. We propose and analyze a generalized version of Smolyak’s algorithm, which provides sparse approximation formulas with convergence rates that mitigate the curse of dimension that appears in multilinear approximation problems with a large number of arguments. We apply the general framework to response surface approximation and optimization under uncertainty for parametric partial differential equations using kernel-based approximation. The theoretical results are supplemented by numerical experiments.

A general theory of electronic parametric instability of relativistically intense laser light in plasma

International Nuclear Information System (INIS)

Parr, D.M.

2000-04-01

This thesis studies the propagation and stability of ultraintense laser light in plasma. A new method is devised, both general and inclusive yet requiring only modest computational effort. The exact anharmonic waveforms for laser light are established. An examination of their stability extends the theory of electron parametric instabilities to relativistic regimes in plasmas of any density including classically overdense plasma accessible by self-induced transparency. Such instabilities can rapidly degrade intense pulses, but can also be harnessed, for example in the self-resonant laser wakefield accelerator. Understanding both the new and established regimes is thus basic to the success of many applications arising in high-field science, including novel x-ray sources and ignition of laser fusion targets, as well as plasma-based accelerator schemes. A covariant formulation of a cold electron fluid plasma is Lorentz transformed to the laser group velocity frame; this is the essence of the method and produces a very simple final model. Then, first, the zero-order laser 'driver' model is developed, in this frame representing a spatially homogeneous environment and thus soluble numerically as ordinary differential equations. The linearised first-order system leads to a further set of differential equations, whose solution defines the growth and other characteristics of an instability. The method is exact, rugged and flexible, avoiding the many approximations and restrictions previously necessary. This approach unifies all theory on purely electronic parametric instabilities over the last 30 years and, for the first time in generality, extends it into the ultrahigh relativistic regime. Besides extensions to familiar parametric instabilities, such as Stimulated Raman Scattering and Two-Plasmon Decay, strong stimulated harmonic generation emerges across a wide range of harmonics with high growth rates, presenting a varied and complex physical entity

Chiral dynamics and peripheral transverse densities

Energy Technology Data Exchange (ETDEWEB)

Granados, Carlos G. [Uppsala University (Sweden); Weiss, Christian [JLAB, Newport News, VA (United States)

2014-01-01

In the partonic (or light-front) description of relativistic systems the electromagnetic form factors are expressed in terms of frame-independent charge and magnetization densities in transverse space. This formulation allows one to identify the chiral components of nucleon structure as the peripheral densities at transverse distances b = O(M{sub {pi}}{sup -1}) and compute them in a parametrically controlled manner. A dispersion relation connects the large-distance behavior of the transverse charge and magnetization densities to the spectral functions of the Dirac and Pauli form factors near the two--pion threshold at timelike t = 4 M{ sub {pi}}{sup 2}, which can be computed in relativistic chiral effective field theory. Using the leading-order approximation we (a) derive the asymptotic behavior (Yukawa tail) of the isovector transverse densities in the "chiral" region b = O(M{sub {pi}}{sup -1}) and the "molecular" region b = O(M{sub N}{sup 2}/M{sub {pi}}{sup 3}); (b) perform the heavy-baryon expansion of the transverse densities; (c) explain the relative magnitude of the peripheral charge and magnetization densities in a simple mechanical picture; (d) include Delta isobar intermediate states and study the peripheral transverse densities in the large-N{ sub c} limit of QCD; (e) quantify the region of transverse distances where the chiral components of the densities are numerically dominant; (f) calculate the chiral divergences of the b{sup 2}-weighted moments of the isovector transverse densities (charge and anomalous magnetic radii) in the limit M{sub {pi}} -> 0 and determine their spatial support. Our approach provides a concise formulation of the spatial structure of the nucleon's chiral component and offers new insights into basic properties of the chiral expansion. It relates the information extracted from low-t elastic form factors to the generalized parton distributions probed in peripheral high-energy scattering processes.

Parametrization of the radiation induced leakage current increase of NMOS transistors

CERN Document Server

Backhaus, Malte

2017-01-13

The increase of the leakage current of NMOS transistors during exposure to ionizing radiation is known and well studied. Radiation hardness by design techniques have been developed to mitigate this effect and have been successfully used. More recent developments in smaller feature size technologies do not make use of these techniques due to their drawbacks in terms of logic density and requirement of dedicated libraries. During operation the resulting increase of the supply current is a serious challenge and needs to be considered during the system design. A simple parametrization of the leakage current of NMOS transistors as a function of total ionizing dose is presented. The parametrization uses a transistor transfer characteristics of the parasitic transistor along the shallow trench isolation to describe the leakage current of the nominal transistor. Together with a parametrization of the number of positive charges trapped in the silicon dioxide and number of activated interface traps in the silicon to si...

Prestack traveltime approximations

KAUST Repository

Alkhalifah, Tariq Ali

2011-01-01

Most prestack traveltime relations we tend work with are based on homogeneous (or semi-homogenous, possibly effective) media approximations. This includes the multi-focusing or double square-root (DSR) and the common reflection stack (CRS) equations. Using the DSR equation, I analyze the associated eikonal form in the general source-receiver domain. Like its wave-equation counterpart, it suffers from a critical singularity for horizontally traveling waves. As a result, I derive expansion based solutions of this eikonal based on polynomial expansions in terms of the reflection and dip angles in a generally inhomogenous background medium. These approximate solutions are free of singularities and can be used to estimate travetimes for small to moderate offsets (or reflection angles) in a generally inhomogeneous medium. A Marmousi example demonstrates the usefulness of the approach. © 2011 Society of Exploration Geophysicists.

Improved parametric fits for the HeH2 ab initio energy surface

International Nuclear Information System (INIS)

Muchnick, P.

1992-01-01

A brief history of the development of ab initio calculations for the HeH 2 quasi-molecule energy surface, and the parametric fits to these ab initio calculations, is presented. The concept of 'physical reasonableness' of the parametric fit is discussed. Several new improved parametric fits for the energy surface, meeting these requirements, are then proposed. One fit extends the Russek-Garcia parametric fit for the deep repulsion region to include r-dependent parameters, resulting in a more physically reasonable fit with smaller average error. This improved surface fit is applied to quasi-elastic collisions of He on H 2 in the impulse approximation. Previous classical calculations of the scaled inelastic vibrorotational excitation energy distributions are improved with this more accurate parametric fit of the energy surface and with the incorporation of quantum effects in vibrational excitation. It is shown that Sigmund's approach in developing his scaling law is incomplete in the contribution of the three-body interactions to vibrational excitation of the H 2 molecule is concerned. The Sigmund theory is extended to take into account for r-dependency of three-body interactions. A parametric fit for the entire energy surface from essentially 0 ≤R≤∞ and 1.2≤r≤1.6 a.u., where R is the intermolecular spacing and r is the hydrogen bonding length, is also presented. This fit is physically reasonable in all asymptotic limits. This first, full surface parametric fit is based primarily upon a composite of ab initio studies by Russek and Garcia and Meyer, Hariharan and Kutzelnigg. Parametric fits for the H 2 (1sσ g ) 2 , H 2 + (1sσ g ), H 2 + (2pσ u ) and (LiH 2 ) + energy surfaces are also presented. The new parametric fits for H 2 , H 2 + (1sσ g ) are shown to be improvements over the well-known Morse potentials for these surfaces

The method of varying amplitudes for solving (non)linear problems involving strong parametric excitation

DEFF Research Database (Denmark)

Sorokin, Vladislav; Thomsen, Jon Juel

2015-01-01

Parametrically excited systems appear in many fields of science and technology, intrinsically or imposed purposefully; e.g. spatially periodic structures represent an important class of such systems [4]. When the parametric excitation can be considered weak, classical asymptotic methods like...... the method of averaging [2] or multiple scales [6] can be applied. However, with many practically important applications this simplification is inadequate, e.g. with spatially periodic structures it restricts the possibility to affect their effective dynamic properties by a structural parameter modulation...... of considerable magnitude. Approximate methods based on Floquet theory [4] for analyzing problems involving parametric excitation, e.g. the classical Hill’s method of infinite determinants [3,4], can be employed also in cases of strong excitation; however, with Floquet theory being applicable only for linear...

Heating tokamaks by parametric decay of intense extraordinary mode radiation

International Nuclear Information System (INIS)

Elder, G.B.; Perkins, F.W.

1979-08-01

Intense electron beam technology has developed coherent, very high power (350 megawatts) microwave sources at frequencies which are a modest fraction of the electron cyclotron frequency in tokamaks. Propagation into a plasma occurs via the extraordinary mode which is subject to parametric decay instabilities in the density range ω/sub o/ 2 2 < ω/sub o/(ω/sub o/ + Ω/sub e/). For an incident wave focused onto a hot spot by a dish antenna of radius rho, the effective threshold power P/sub o/ required to induced effective parametric heating is P/sub o/ approx. = 10 MW x/rho Ω/sub e//ω/sub o/ (T/sub e//1 keV)/sup 3/2/ where x denotes the distance to the hot spot

Design of semi-rigid type of flexible pavements

Directory of Open Access Journals (Sweden)

Pranshoo Solanki

2017-03-01

Full Text Available The primary objective of the study presented in this paper is to develop design curves for performance prediction of stabilized layers and to compare semi-rigid flexible pavement designs between the empirical AASHTO 1993 and the mechanistic-empirical pavement design methodologies. Specifically, comparisons were made for a range of different sections consisting of cementitious layers stabilized with different types and percentages of additives. It is found that the design thickness is influenced by the type of soil, additive, selection of material property and design method. Cost comparisons of sections stabilized with different percentage and type of additives showed that CKD-stabilization provides economically low cost sections as compared to lime- and CFA-stabilized sections. Knowledge gained from the parametric analysis of different sections using AASHTO 1993 and MEPDG is expected to be useful to pavement designers and others in implementation of the new MEPDG for future pavement design. Keywords: Semi-rigid, Mechanistic, Resilient modulus, Fatigue life, Reliability, Traffic

Efficiency Analysis of German Electricity Distribution Utilities : Non-Parametric and Parametric Tests

OpenAIRE

von Hirschhausen, Christian R.; Cullmann, Astrid

2005-01-01

Abstract This paper applies parametric and non-parametric and parametric tests to assess the efficiency of electricity distribution companies in Germany. We address traditional issues in electricity sector benchmarking, such as the role of scale effects and optimal utility size, as well as new evidence specific to the situation in Germany. We use labour, capital, and peak load capacity as inputs, and units sold and the number of customers as output. The data cover 307 (out of 553) ...

Electronic structure of PrBa2Cu3O7: A local-spin-density approximation with on-site Coulomb interaction

International Nuclear Information System (INIS)

Biagini, M.; Calandra, C.; Ossicini, S.

1995-01-01

Electronic structure calculations based on the local-spin-density approximation (LSDA) fail to reproduce the antiferromagnetic ground state of PrBa 2 Cu 3 O 7 (PBCO). We have performed linear muffin-tin orbital--atomic sphere approximation calculations, based on the local-spin-density approximation with on-site Coulomb correlation applied to Cu(1) and Cu(2) 3d states. We have found that inclusion of the on-site Coulomb interaction modifies qualitatively the electronic structure of PBCO with respect to the LSDA results, and gives Cu spin moments in good agreement with the experimental values. The Cu(2) upper Hubbard band lies about 1 eV above the Fermi energy, indicating a Cu II oxidation state. On the other hand, the Cu(1) upper Hubbard band is located across the Fermi level, which implies an intermediate oxidation state for the Cu(1) ion, between Cu I and Cu II . The metallic character of the CuO chains is preserved, in agreement with optical reflectivity [K. Takenaka et al., Phys. Rev. B 46, 5833 (1992)] and positron annihilation experiments [L. Hoffmann et al., Phys. Rev. Lett. 71, 4047 (1993)]. These results support the view of an extrinsic origin of the insulating character of PrBa 2 Cu 3 O 7

Tree-space statistics and approximations for large-scale analysis of anatomical trees

DEFF Research Database (Denmark)

Feragen, Aasa; Owen, Megan; Petersen, Jens

2013-01-01

parametrize the relevant parts of tree-space well. Using the developed approximate statistics, we illustrate how the structure and geometry of airway trees vary across a population and show that airway trees with Chronic Obstructive Pulmonary Disease come from a different distribution in tree-space than...

Parametric Sensitivity Tests—European Polymer Electrolyte Membrane Fuel Cell Stack Test Procedures

DEFF Research Database (Denmark)

Araya, Samuel Simon; Andreasen, Søren Juhl; Kær, Søren Knudsen

2014-01-01

performed based on test procedures proposed by a European project, Stack-Test. The sensitivity of a Nafion-based low temperature PEMFC stack’s performance to parametric changes was the main objective of the tests. Four crucial parameters for fuel cell operation were chosen; relative humidity, temperature......As fuel cells are increasingly commercialized for various applications, harmonized and industry-relevant test procedures are necessary to benchmark tests and to ensure comparability of stack performance results from different parties. This paper reports the results of parametric sensitivity tests......, pressure, and stoichiometry at varying current density. Furthermore, procedures for polarization curve recording were also tested both in ascending and descending current directions....

Density Forecasts of Crude-Oil Prices Using Option-Implied and ARCH-Type Models

DEFF Research Database (Denmark)

Tsiaras, Leonidas; Høg, Esben

  The predictive accuracy of competing crude-oil price forecast densities is investigated for the 1994-2006 period. Moving beyond standard ARCH models that rely exclusively on past returns, we examine the benefits of utilizing the forward-looking information that is embedded in the prices...... as for regions and intervals that are of special interest for the economic agent. We find that non-parametric adjustments of risk-neutral density forecasts perform significantly better than their parametric counterparts. Goodness-of-fit tests and out-of-sample likelihood comparisons favor forecast densities...

Assessing pupil and school performance by non-parametric and parametric techniques

NARCIS (Netherlands)

de Witte, K.; Thanassoulis, E.; Simpson, G.; Battisti, G.; Charlesworth-May, A.

2010-01-01

This paper discusses the use of the non-parametric free disposal hull (FDH) and the parametric multi-level model (MLM) as alternative methods for measuring pupil and school attainment where hierarchical structured data are available. Using robust FDH estimates, we show how to decompose the overall

Modeling a nucleon system: static and dynamical properties - density fluctuations

International Nuclear Information System (INIS)

Idier, D.

1997-01-01

This thesis sets forth a quasi-particle model for the static and dynamical properties of nuclear matter. This model is based on a scale ratio of quasi-particle to nucleons and the projection of the semi-classical distribution on a coherent Gaussian state basis. The first chapter is dealing with the transport equations, particularly with the Vlasov equation for Wigner distribution function. The second one is devoted to the statics of nuclear matter. Here, the sampling effect upon the nuclear density is treated and the state equation of the Gaussian fluid is compared with that given by Hartree-Fock approximation. We define state equation as the relationship between the nucleon binding energy and density, for a given temperature. The curvature around the state equation minimum of the quasi-particle system is shown to be related to the speed of propagation of density perturbation. The volume energy and the surface properties of a (semi-)infinite nucleon system are derived. For the resultant saturated auto-coherent semi-infinite system of quasi-particles the surface coefficient appearing in the mass formula is extracted as well as the system density profile. The third chapter treats the dynamics of the two-particle residual interactions. The effect of different parameters on relaxation of a nucleon system without a mean field is studied by means of a Eulerian and Lagrangian modeling. The fourth chapter treats the volume instabilities (spinodal decomposition) in nuclear matter. The quasi-particle systems, initially prepared in the spinodal region of the utilized interaction, are set to evolve. It is shown then that the scale ratio acts upon the amount of fluctuations injected in the system. The inhomogeneity degree and a proper time are defined and the role of collisions in the spinodal decomposition as well as that of the initial temperature and density, are investigated. Assuming different effective macroscopic interactions, the influence of quantities as

Coupled dimensionality reduction and classification for supervised and semi-supervised multilabel learning.

Science.gov (United States)

Gönen, Mehmet

2014-03-01

Coupled training of dimensionality reduction and classification is proposed previously to improve the prediction performance for single-label problems. Following this line of research, in this paper, we first introduce a novel Bayesian method that combines linear dimensionality reduction with linear binary classification for supervised multilabel learning and present a deterministic variational approximation algorithm to learn the proposed probabilistic model. We then extend the proposed method to find intrinsic dimensionality of the projected subspace using automatic relevance determination and to handle semi-supervised learning using a low-density assumption. We perform supervised learning experiments on four benchmark multilabel learning data sets by comparing our method with baseline linear dimensionality reduction algorithms. These experiments show that the proposed approach achieves good performance values in terms of hamming loss, average AUC, macro F 1 , and micro F 1 on held-out test data. The low-dimensional embeddings obtained by our method are also very useful for exploratory data analysis. We also show the effectiveness of our approach in finding intrinsic subspace dimensionality and semi-supervised learning tasks.

Towards Stabilizing Parametric Active Contours

DEFF Research Database (Denmark)

Liu, Jinchao; Fan, Zhun; Olsen, Søren Ingvor

2014-01-01

Numerical instability often occurs in evolving of parametric active contours. This is mainly due to the undesired change of parametrization during evolution. In this paper, we propose a new tangential diffusion term to compensate this undesired change. As a result, the parametrization will converge...

Demographics and practices of semi-intensive free-range farming systems in Australia with an outdoor stocking density of ≤1500 hens/hectare

Science.gov (United States)

Ruhnke, Isabelle; de Koning, Carolyn; Drake, Kelly; Skerman, Alan G.; Hinch, Geoff N.; Glatz, Philip C.

2017-01-01

Baseline information on demographics and practices on semi-intensive free-range egg farms with an outdoor stocking density of ≤1500 hens/hectare in Australia is presented. Free-range egg production is changing the structure of the egg industry in Australia and a broad variety and tiers of free-range systems have emerged due to lack of concrete legislative standards on outdoor stocking densities in the past. Information was extracted from a pre-existing online free-range poultry survey dataset, consisting of a total of 79 questions related to nutrition, pasture management, welfare and health, animal housing, environmental impact and economics. Forty-one free-range egg farms, with an outdoor stocking density of ≤1500 hens/hectare, were identified in the dataset from all major Australian states. Two types of semi-intensive free-range housing systems were documented: mobile (modified caravan/trailer) housing (56%), and fixed sheds (44%). Seventy-two percent of respondents reported >75% of the hens in the flock used the outdoor range. All respondents reported ingestion of range components by hens in the form of vegetation, insects, stones and grit. Up to 10% mortality was reported by 40% respondents with predation (34%), cannibalism (29%), heat stress (24%) and grass impaction (19.5%) as major causes. Biosecurity on farms was sub-optimal with 8 of the 10 actions implemented by farms. Applied research and communication of results to farmers is highly recommended to ensure optimum health and welfare of free-range laying hens and sustained egg production. PMID:29065169

Critical appraisal of semi-quantitative analysis of 2-deoxyglucose autoradiograms

Energy Technology Data Exchange (ETDEWEB)

Kelly, P T; McCulloch, J [Glasgow Univ. (UK)

1983-06-13

Semi-quantitative analysis (e.g. optical density ratios) of (/sup 14/C)2-deoxyglucose autoradiograms is widely used in neuroscience research. The authors demonstrate that a fixed ratio of /sup 14/C-concentrations in the CNS does not yield a constant optical density ratio but is dependent upon the exposure time in the preparation of the autoradiograms and the absolute amounts of /sup 14/C from which the concentration ratio is derived. The failure of a fixed glucose utilization ratio to result in a constant optical density ratio represents a major interpretative difficulty in investigations where only semi-quantitative analysis of (/sup 14/C)2-deoxyglucose autoradiograms is undertaken.

Analysis and implementation issues for the numerical approximation of parabolic equations with random coefficients

KAUST Repository

Nobile, Fabio; Tempone, Raul

2009-01-01

We consider the problem of numerically approximating statistical moments of the solution of a time- dependent linear parabolic partial differential equation (PDE), whose coefficients and/or forcing terms are spatially correlated random fields. The stochastic coefficients of the PDE are approximated by truncated Karhunen-Loève expansions driven by a finite number of uncorrelated random variables. After approxi- mating the stochastic coefficients, the original stochastic PDE turns into a new deterministic parametric PDE of the same type, the dimension of the parameter set being equal to the number of random variables introduced. After proving that the solution of the parametric PDE problem is analytic with respect to the parameters, we consider global polynomial approximations based on tensor product, total degree or sparse polynomial spaces and constructed by either a Stochastic Galerkin or a Stochastic Collocation approach. We derive convergence rates for the different cases and present numerical results that show how these approaches are a valid alternative to the more traditional Monte Carlo Method for this class of problems. © 2009 John Wiley & Sons, Ltd.

Analysis and implementation issues for the numerical approximation of parabolic equations with random coefficients

KAUST Repository

Nobile, Fabio

2009-11-05

We consider the problem of numerically approximating statistical moments of the solution of a time- dependent linear parabolic partial differential equation (PDE), whose coefficients and/or forcing terms are spatially correlated random fields. The stochastic coefficients of the PDE are approximated by truncated Karhunen-Loève expansions driven by a finite number of uncorrelated random variables. After approxi- mating the stochastic coefficients, the original stochastic PDE turns into a new deterministic parametric PDE of the same type, the dimension of the parameter set being equal to the number of random variables introduced. After proving that the solution of the parametric PDE problem is analytic with respect to the parameters, we consider global polynomial approximations based on tensor product, total degree or sparse polynomial spaces and constructed by either a Stochastic Galerkin or a Stochastic Collocation approach. We derive convergence rates for the different cases and present numerical results that show how these approaches are a valid alternative to the more traditional Monte Carlo Method for this class of problems. © 2009 John Wiley & Sons, Ltd.

Accelerated failure time models for semi-competing risks data in the presence of complex censoring.

Science.gov (United States)

Lee, Kyu Ha; Rondeau, Virginie; Haneuse, Sebastien

2017-12-01

Statistical analyses that investigate risk factors for Alzheimer's disease (AD) are often subject to a number of challenges. Some of these challenges arise due to practical considerations regarding data collection such that the observation of AD events is subject to complex censoring including left-truncation and either interval or right-censoring. Additional challenges arise due to the fact that study participants under investigation are often subject to competing forces, most notably death, that may not be independent of AD. Towards resolving the latter, researchers may choose to embed the study of AD within the "semi-competing risks" framework for which the recent statistical literature has seen a number of advances including for the so-called illness-death model. To the best of our knowledge, however, the semi-competing risks literature has not fully considered analyses in contexts with complex censoring, as in studies of AD. This is particularly the case when interest lies with the accelerated failure time (AFT) model, an alternative to the traditional multiplicative Cox model that places emphasis away from the hazard function. In this article, we outline a new Bayesian framework for estimation/inference of an AFT illness-death model for semi-competing risks data subject to complex censoring. An efficient computational algorithm that gives researchers the flexibility to adopt either a fully parametric or a semi-parametric model specification is developed and implemented. The proposed methods are motivated by and illustrated with an analysis of data from the Adult Changes in Thought study, an on-going community-based prospective study of incident AD in western Washington State. © 2017, The International Biometric Society.

Semi-analytic techniques for calculating bubble wall profiles

International Nuclear Information System (INIS)

Akula, Sujeet; Balazs, Csaba; White, Graham A.

2016-01-01

We present semi-analytic techniques for finding bubble wall profiles during first order phase transitions with multiple scalar fields. Our method involves reducing the problem to an equation with a single field, finding an approximate analytic solution and perturbing around it. The perturbations can be written in a semi-analytic form. We assert that our technique lacks convergence problems and demonstrate the speed of convergence on an example potential. (orig.)

Semi-nonparametric VaR forecasts for hedge funds during the recent crisis

Science.gov (United States)

Del Brio, Esther B.; Mora-Valencia, Andrés; Perote, Javier

2014-05-01

The need to provide accurate value-at-risk (VaR) forecasting measures has triggered an important literature in econophysics. Although these accurate VaR models and methodologies are particularly demanded for hedge fund managers, there exist few articles specifically devoted to implement new techniques in hedge fund returns VaR forecasting. This article advances in these issues by comparing the performance of risk measures based on parametric distributions (the normal, Student’s t and skewed-t), semi-nonparametric (SNP) methodologies based on Gram-Charlier (GC) series and the extreme value theory (EVT) approach. Our results show that normal-, Student’s t- and Skewed t- based methodologies fail to forecast hedge fund VaR, whilst SNP and EVT approaches accurately success on it. We extend these results to the multivariate framework by providing an explicit formula for the GC copula and its density that encompasses the Gaussian copula and accounts for non-linear dependences. We show that the VaR obtained by the meta GC accurately captures portfolio risk and outperforms regulatory VaR estimates obtained through the meta Gaussian and Student’s t distributions.

Variance in parametric images: direct estimation from parametric projections

International Nuclear Information System (INIS)

Maguire, R.P.; Leenders, K.L.; Spyrou, N.M.

2000-01-01

Recent work has shown that it is possible to apply linear kinetic models to dynamic projection data in PET in order to calculate parameter projections. These can subsequently be back-projected to form parametric images - maps of parameters of physiological interest. Critical to the application of these maps, to test for significant changes between normal and pathophysiology, is an assessment of the statistical uncertainty. In this context, parametric images also include simple integral images from, e.g., [O-15]-water used to calculate statistical parametric maps (SPMs). This paper revisits the concept of parameter projections and presents a more general formulation of the parameter projection derivation as well as a method to estimate parameter variance in projection space, showing which analysis methods (models) can be used. Using simulated pharmacokinetic image data we show that a method based on an analysis in projection space inherently calculates the mathematically rigorous pixel variance. This results in an estimation which is as accurate as either estimating variance in image space during model fitting, or estimation by comparison across sets of parametric images - as might be done between individuals in a group pharmacokinetic PET study. The method based on projections has, however, a higher computational efficiency, and is also shown to be more precise, as reflected in smooth variance distribution images when compared to the other methods. (author)

Commercial aspects of semi-reusable launch systems

Science.gov (United States)

Obersteiner, M. H.; Müller, H.; Spies, H.

2003-07-01

This paper presents a business planning model for a commercial space launch system. The financing model is based on market analyses and projections combined with market capture models. An operations model is used to derive the annual cash income. Parametric cost modeling, development and production schedules are used for quantifying the annual expenditures, the internal rate of return, break even point of positive cash flow and the respective prices per launch. Alternative consortia structures, cash flow methods, capture rates and launch prices are used to examine the sensitivity of the model. Then the model is applied for a promising semi-reusable launcher concept, showing the general achievability of the commercial approach and the necessary pre-conditions.

Semi-transparent a-IGZO thin-film transistors with polymeric gate dielectric.

Science.gov (United States)

Hyung, Gun Woo; Wang, Jian-Xun; Li, Zhao-Hui; Koo, Ja-Ryong; Kwon, Sang Jik; Cho, Eou-Sik; Kim, Young Kwan

2013-06-01

We report the fabrication of semi-transparent a-IGZO-based thin-film transistors (TFTs) with crosslinked poly-4-vinylphenol (PVP) gate dielectric layers on PET substrate and thermally-evaporated Al/Ag/Al source and drain (S&D) electrodes, which showed a transmittance of 64% at a 500-nm wavelength and sheet resistance of 16.8 omega/square. The semi-transparent a-IGZO TFTs with a PVP layer exhibited decent saturation mobilities (maximum approximately 5.8 cm2Ns) and on/off current ratios of approximately 10(6).

Magneto-optical properties of semi-parabolic plus semi-inverse squared quantum wells

Science.gov (United States)

Tung, Luong V.; Vinh, Pham T.; Phuc, Huynh V.

2018-06-01

We theoretically study the optical absorption in a quantum well with the semi-parabolic potential plus the semi-inverse squared potential (SPSIS) in the presence of a static magnetic field in which both one- and two-photon absorption processes have been taken into account. The expression of the magneto-optical absorption coefficient (MOAC) is expressed by the second-order golden rule approximation including the electron-LO phonon interaction. We also use the profile method to obtain the full width at half maximum (FWHM) of the absorption peaks. Our numerical results show that either MOAC or FWHM strongly depends on the confinement frequency, temperature, and magnetic field but their dependence on the parameter β is very weak. The temperature dependence of FWHM is consistent with the previous theoretical and experimental works.

Dirac particle in a plane wave field and the semi-classical approximation

Energy Technology Data Exchange (ETDEWEB)

Bourouaine, S. [Department of Physics, Faculty of Sciences, Mentouri University, Constantine (Algeria)

2005-04-01

In this paper we investigate the influence of photon represented by plane wave field on Dirac particle in the context of path integral approach given by Fradkin and Gitman formalism. In our case, although the action relative to Dirac particle in plane wave field seems to be non quadratic, the result obtained by semi-classical approach is the same as that found by an exact calculation. Hence; when we add the plane wave field to any quadratic actions related to Fradkin and Gitman approach, the total action behaves like quadratic. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

Dirac particle in a plane wave field and the semi-classical approximation

International Nuclear Information System (INIS)

Bourouaine, S.

2005-01-01

In this paper we investigate the influence of photon represented by plane wave field on Dirac particle in the context of path integral approach given by Fradkin and Gitman formalism. In our case, although the action relative to Dirac particle in plane wave field seems to be non quadratic, the result obtained by semi-classical approach is the same as that found by an exact calculation. Hence; when we add the plane wave field to any quadratic actions related to Fradkin and Gitman approach, the total action behaves like quadratic. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

Learning Mixtures of Polynomials of Conditional Densities from Data

DEFF Research Database (Denmark)

L. López-Cruz, Pedro; Nielsen, Thomas Dyhre; Bielza, Concha

2013-01-01

Mixtures of polynomials (MoPs) are a non-parametric density estimation technique for hybrid Bayesian networks with continuous and discrete variables. We propose two methods for learning MoP ap- proximations of conditional densities from data. Both approaches are based on learning MoP approximatio...

Molecular Excitation Energies from Time-Dependent Density Functional Theory Employing Random-Phase Approximation Hessians with Exact Exchange.

Science.gov (United States)

Heßelmann, Andreas

2015-04-14

Molecular excitation energies have been calculated with time-dependent density-functional theory (TDDFT) using random-phase approximation Hessians augmented with exact exchange contributions in various orders. It has been observed that this approach yields fairly accurate local valence excitations if combined with accurate asymptotically corrected exchange-correlation potentials used in the ground-state Kohn-Sham calculations. The inclusion of long-range particle-particle with hole-hole interactions in the kernel leads to errors of 0.14 eV only for the lowest excitations of a selection of three alkene, three carbonyl, and five azabenzene molecules, thus surpassing the accuracy of a number of common TDDFT and even some wave function correlation methods. In the case of long-range charge-transfer excitations, the method typically underestimates accurate reference excitation energies by 8% on average, which is better than with standard hybrid-GGA functionals but worse compared to range-separated functional approximations.

Comparison of approximations to the transition rate in the DDHMS preequilibrium model

International Nuclear Information System (INIS)

Brito, L.; Carlson, B.V.

2014-01-01

The double differential hybrid Monte Carlo simulation model (DDHMS) originally used exciton model densities and transition densities with approximate angular distributions obtained using linear momentum conservation. Because the model uses only the simplest transition rates, calculations using more complex approximations to these are still viable. We compare calculations using the original approximation to one using a nonrelativistic Fermi gas transition densities with the approximate angular distributions and with exact nonrelativistic and relativistic transition transition densities. (author)

A Semi-Analytical Extraction Method for Interface and Bulk Density of States in Metal Oxide Thin-Film Transistors.

Science.gov (United States)

Chen, Weifeng; Wu, Weijing; Zhou, Lei; Xu, Miao; Wang, Lei; Ning, Honglong; Peng, Junbiao

2018-03-11

A semi-analytical extraction method of interface and bulk density of states (DOS) is proposed by using the low-frequency capacitance-voltage characteristics and current-voltage characteristics of indium zinc oxide thin-film transistors (IZO TFTs). In this work, an exponential potential distribution along the depth direction of the active layer is assumed and confirmed by numerical solution of Poisson's equation followed by device simulation. The interface DOS is obtained as a superposition of constant deep states and exponential tail states. Moreover, it is shown that the bulk DOS may be represented by the superposition of exponential deep states and exponential tail states. The extracted values of bulk DOS and interface DOS are further verified by comparing the measured transfer and output characteristics of IZO TFTs with the simulation results by a 2D device simulator ATLAS (Silvaco). As a result, the proposed extraction method may be useful for diagnosing and characterising metal oxide TFTs since it is fast to extract interface and bulk density of states (DOS) simultaneously.

A Semi-Analytical Extraction Method for Interface and Bulk Density of States in Metal Oxide Thin-Film Transistors

Directory of Open Access Journals (Sweden)

Weifeng Chen

2018-03-01

Full Text Available A semi-analytical extraction method of interface and bulk density of states (DOS is proposed by using the low-frequency capacitance–voltage characteristics and current–voltage characteristics of indium zinc oxide thin-film transistors (IZO TFTs. In this work, an exponential potential distribution along the depth direction of the active layer is assumed and confirmed by numerical solution of Poisson’s equation followed by device simulation. The interface DOS is obtained as a superposition of constant deep states and exponential tail states. Moreover, it is shown that the bulk DOS may be represented by the superposition of exponential deep states and exponential tail states. The extracted values of bulk DOS and interface DOS are further verified by comparing the measured transfer and output characteristics of IZO TFTs with the simulation results by a 2D device simulator ATLAS (Silvaco. As a result, the proposed extraction method may be useful for diagnosing and characterising metal oxide TFTs since it is fast to extract interface and bulk density of states (DOS simultaneously.

Nuclear densities of 1fsub(7/2) nuclei from elastic alpha-particle scattering

International Nuclear Information System (INIS)

Friedman, E.; Gils, H.J.; Rebel, H.

1983-12-01

The elastic scattering of 104 MeV α particles by sup(40,42,43,44,48)Ca, 50 Ti, 51 V, 52 Cr has been analyzed by phenomenological and semimicroscopic optical potentials in order to get information on isotopic and isotonic differences of the α particle optical potentials and of nuclear matter densities. The phenomenological optical potentials based on a Fourier-Bessel description of the real part reveal different behaviour in size and shape for the isotonic chain as compared to the isotopic chain. Odd-even effects are also indicated to be different for isotones and isotopes. The semi-microscopic analyses use a single-folding model with a density-dependent effective αN-interaction including a realistic local density approximation. The calculated potentials are fully consistent with the phenomenological ones. Isopotic and isotonic differences of the nuclear matter densities obtained from the folding model in general show a similar behavior as the optical potential differences. The results on matter densities are compared to other investigations. (orig.) [de

Exact exchange-correlation potential and approximate exchange potential in terms of density matrices

International Nuclear Information System (INIS)

Holas, A.; March, N.H.

1995-01-01

An exact expression in terms of density matrices (DM) is derived for δF[n]/δn(r), the functional derivative of the Hohenberg-Kohn functional. The derivation starts from the differential form of the virial theorem, obtained here for an electron system with arbitrary interactions, and leads to an expression taking the form of an integral over a path that can be chosen arbitrarily. After applying this approach to the equivalent system of noninteracting electrons (Slater-Kohn-Sham scheme) and combining the corresponding result with the previous one, an exact expression for the exchange-correlation potential v xc (r) is obtained which is analogous in character to that for δF[n]/δn(r), but involving, besides the interacting-system DMs, also the noninteracitng DMs. Equating the former DMs to the latter ones, we reduce the result for the exact v xc (r) to that for an approximate exchange-only potential v x (r). This leads naturally to the Harbola-Sahni exchange-only potential

Parametric interaction of waves in the plasma with random large-scale inhomogeneities

International Nuclear Information System (INIS)

Abramovich, B.S.; Tamojkin, V.V.

1980-01-01

Parametric processes of the decay and fusion of three waves in a weakly turbulent plasma with random inhomogeneities, the size of which is too big as compared with wave-lengths are considered. Under the diffusive approximation applicability closed equations are obtained, which determine the behaviour of all the intensity moments of parametrically bound waves. It is shown that under the conditions when the characteristic length of the multiple scattering is considerably less than the nonlinear interaction, length the effective increment of average intensity increase and its moments at dissociation processes is too small as compared with the homogeneous plasma case. At fusion processes the same increment (decrement) determines the distance at which all intensity moments are in the saturation regime

Semi-Automatic Modelling of Building FAÇADES with Shape Grammars Using Historic Building Information Modelling

Science.gov (United States)

Dore, C.; Murphy, M.

2013-02-01

This paper outlines a new approach for generating digital heritage models from laser scan or photogrammetric data using Historic Building Information Modelling (HBIM). HBIM is a plug-in for Building Information Modelling (BIM) software that uses parametric library objects and procedural modelling techniques to automate the modelling stage. The HBIM process involves a reverse engineering solution whereby parametric interactive objects representing architectural elements are mapped onto laser scan or photogrammetric survey data. A library of parametric architectural objects has been designed from historic manuscripts and architectural pattern books. These parametric objects were built using an embedded programming language within the ArchiCAD BIM software called Geometric Description Language (GDL). Procedural modelling techniques have been implemented with the same language to create a parametric building façade which automatically combines library objects based on architectural rules and proportions. Different configurations of the façade are controlled by user parameter adjustment. The automatically positioned elements of the façade can be subsequently refined using graphical editing while overlaying the model with orthographic imagery. Along with this semi-automatic method for generating façade models, manual plotting of library objects can also be used to generate a BIM model from survey data. After the 3D model has been completed conservation documents such as plans, sections, elevations and 3D views can be automatically generated for conservation projects.

A study of density effects in plasmas using analytical approximations for the self-consistent potential

Science.gov (United States)

Poirier, M.

2015-06-01

Density effects in ionized matter require particular attention since they modify energies, wavefunctions and transition rates with respect to the isolated-ion situation. The approach chosen in this paper is based on the ion-sphere model involving a Thomas-Fermi-like description for free electrons, the bound electrons being described by a full quantum mechanical formalism. This permits to deal with plasmas out of thermal local equilibrium, assuming only a Maxwell distribution for free electrons. For H-like ions, such a theory provides simple and rather accurate analytical approximations for the potential created by free electrons. Emphasis is put on the plasma potential rather than on the electron density, since the energies and wavefunctions depend directly on this potential. Beyond the uniform electron gas model, temperature effects may be analyzed. In the case of H-like ions, this formalism provides analytical perturbative expressions for the energies, wavefunctions and transition rates. Explicit expressions are given in the case of maximum orbital quantum number, and compare satisfactorily with results from a direct integration of the radial Schrödinger equation. Some formulas for lower orbital quantum numbers are also proposed.

Right unitarity triangles, stable CP-violating phases and approximate quark-lepton complementarity

International Nuclear Information System (INIS)

Xing Zhizhong

2009-01-01

Current experimental data indicate that two unitarity triangles of the CKM quark mixing matrix V are almost the right triangles with α∼90 deg. We highlight a very suggestive parametrization of V and show that its CP-violating phase φ is nearly equal to α (i.e., φ-α∼1.1 deg.). Both φ and α are stable against the renormalizaton-group evolution from the electroweak scale M Z to a superhigh energy scale M X or vice versa, and thus it is impossible to obtain α=90 deg. at M Z from φ=90 deg. at M X . We conjecture that there might also exist a maximal CP-violating phase φ∼90 deg. in the MNS lepton mixing matrix U. The approximate quark-lepton complementarity relations, which hold in the standard parametrizations of V and U, can also hold in our particular parametrizations of V and U simply due to the smallness of |V ub | and |V e3 |.

Parametric instabilities in inhomogeneous plasma

International Nuclear Information System (INIS)

Nicholson, D.R.

1975-01-01

The nonlinear coupling of three waves in a plasma is considered. One of the waves is assumed large and constant; its amplitude is the parameter of the parametric instability. The spatial-temporal evolution of the other two waves is treated theoretically, in one dimension, by analytic methods and by direct numerical integration of the basic equations. Various monotonic forms of inhomogeneity are considered; agreement with previous work is found and new results are established. Nonmonotonic inhomogeneities are considered, in the form of turbulence and, as a model problem, in the form of a simple sinusoidal modulation. Relatively small amounts of nonmonotonic inhomogeneity, in the presence of a linear density gradient, are found to destabilize the well-known convective saturation, absolute growth occurring instead. (U.S.)

Speaker Linking and Applications using Non-Parametric Hashing Methods

Science.gov (United States)

2016-09-08

nonparametric estimate of a multivariate density function,” The Annals of Math- ematical Statistics , vol. 36, no. 3, pp. 1049–1051, 1965. [9] E. A. Patrick...Speaker Linking and Applications using Non-Parametric Hashing Methods† Douglas Sturim and William M. Campbell MIT Lincoln Laboratory, Lexington, MA...with many approaches [1, 2]. For this paper, we focus on using i-vectors [2], but the methods apply to any embedding. For the task of speaker QBE and

Dispersions in Semi-Classical Dynamics

International Nuclear Information System (INIS)

Zielinska-Pfabe, M.; Gregoire, C.

1987-01-01

Dispersions around mean values of one-body observables are obtained by restoring classical many-body correlations in Vlasov and Landau-Vlasov dynamics. The method is applied to the calculation of fluctuations in mass, charge and linear momentum in heavy-ion collisions. Results are compared to those obtained by the Balian-Veneroni variational principle in semi-classical approximation

Efficient, approximate and parallel Hartree-Fock and hybrid DFT calculations. A 'chain-of-spheres' algorithm for the Hartree-Fock exchange

International Nuclear Information System (INIS)

Neese, Frank; Wennmohs, Frank; Hansen, Andreas; Becker, Ute

2009-01-01

In this paper, the possibility is explored to speed up Hartree-Fock and hybrid density functional calculations by forming the Coulomb and exchange parts of the Fock matrix by different approximations. For the Coulomb part the previously introduced Split-RI-J variant (F. Neese, J. Comput. Chem. 24 (2003) 1740) of the well-known 'density fitting' approximation is used. The exchange part is formed by semi-numerical integration techniques that are closely related to Friesner's pioneering pseudo-spectral approach. Our potentially linear scaling realization of this algorithm is called the 'chain-of-spheres exchange' (COSX). A combination of semi-numerical integration and density fitting is also proposed. Both Split-RI-J and COSX scale very well with the highest angular momentum in the basis sets. It is shown that for extended basis sets speed-ups of up to two orders of magnitude compared to traditional implementations can be obtained in this way. Total energies are reproduced with an average error of <0.3 kcal/mol as determined from extended test calculations with various basis sets on a set of 26 molecules with 20-200 atoms and up to 2000 basis functions. Reaction energies agree to within 0.2 kcal/mol (Hartree-Fock) or 0.05 kcal/mol (hybrid DFT) with the canonical values. The COSX algorithm parallelizes with a speedup of 8.6 observed for 10 processes. Minimum energy geometries differ by less than 0.3 pm in the bond distances and 0.5 deg. in the bond angels from their canonical values. These developments enable highly efficient and accurate self-consistent field calculations including nonlocal Hartree-Fock exchange for large molecules. In combination with the RI-MP2 method and large basis sets, second-order many body perturbation energies can be obtained for medium sized molecules with unprecedented efficiency. The algorithms are implemented into the ORCA electronic structure system

A Monte Carlo-adjusted goodness-of-fit test for parametric models describing spatial point patterns

KAUST Repository

Dao, Ngocanh; Genton, Marc G.

2014-01-01

Assessing the goodness-of-fit (GOF) for intricate parametric spatial point process models is important for many application fields. When the probability density of the statistic of the GOF test is intractable, a commonly used procedure is the Monte

Parametrically induced low-frequency waves in weakly inhomogeneous magnetized plasmas

International Nuclear Information System (INIS)

Pesic, S.

1981-01-01

The linear dispersion relation governing the parametric interaction of a lower hybrid pump wave with a weakly-inhomogeneous current carrying hot plasma confined by a helical magnetic field is derived and solved numerically. The stability boundaries are delineated over a wide range in the k-space. The frequency and growth rate of decay instabilities are calculated for plasma parameters relevant to lower hybrid plasma heating experiments. The parametric excitation of drift waves and ion cyclotron current instabilities is discussed. In the low-density plasma region low minimum thresholds and high growth rates are obtained for the pump decay into ion cyclotron and nonresonant quasimodes. The spatial amplification of hot ion Bernstein waves and nonresonant quasimodes dominate in the plasma core (ω 0 /ωsub(LH) < 2). The presented theoretical results are in qualitative agreement with current LH plasma heating experiments. (author)

Conditions of equilibrium of a rotating ideal fluid in the parametrized post-Newtonian formalism

International Nuclear Information System (INIS)

Bondarenko, N.P.

1986-01-01

Conditions of equilibrium of a rotating ideal fluid in parametrized post-Newtonian hydrodynamics are obtained by the variational method. They generalize the analogous equilibrium conditions in the post-Newtonian approximation of the general theory of relativity. A conservation law for the total energy is obtained by integrating the equations of motion

STATCAT, Statistical Analysis of Parametric and Non-Parametric Data

International Nuclear Information System (INIS)

David, Hugh

1990-01-01

1 - Description of program or function: A suite of 26 programs designed to facilitate the appropriate statistical analysis and data handling of parametric and non-parametric data, using classical and modern univariate and multivariate methods. 2 - Method of solution: Data is read entry by entry, using a choice of input formats, and the resultant data bank is checked for out-of- range, rare, extreme or missing data. The completed STATCAT data bank can be treated by a variety of descriptive and inferential statistical methods, and modified, using other standard programs as required

A critical appraisal of semi-quantitative analysis of 2-deoxyglucose autoradiograms

International Nuclear Information System (INIS)

Kelly, P.T.; McCulloch, J.

1983-01-01

Semi-quantitative analysis (e.g. optical density ratios) of [ 14 C]2-deoxyglucose autoradiograms is widely used in neuroscience research. The authors demonstrate that a fixed ratio of 14 C-concentrations in the CNS does not yield a constant optical density ratio but is dependent upon the exposure time in the preparation of the autoradiograms and the absolute amounts of 14 C from which the concentration ratio is derived. The failure of a fixed glucose utilization ratio to result in a constant optical density ratio represents a major interpretative difficulty in investigations where only semi-quantitative analysis of [ 14 C]2-deoxyglucose autoradiograms is undertaken. (Auth.)

Analytic energy gradients for the coupled-cluster singles and doubles method with the density-fitting approximation

International Nuclear Information System (INIS)

Bozkaya, Uğur; Sherrill, C. David

2016-01-01

An efficient implementation is presented for analytic gradients of the coupled-cluster singles and doubles (CCSD) method with the density-fitting approximation, denoted DF-CCSD. Frozen core terms are also included. When applied to a set of alkanes, the DF-CCSD analytic gradients are significantly accelerated compared to conventional CCSD for larger molecules. The efficiency of our DF-CCSD algorithm arises from the acceleration of several different terms, which are designated as the “gradient terms”: computation of particle density matrices (PDMs), generalized Fock-matrix (GFM), solution of the Z-vector equation, formation of the relaxed PDMs and GFM, back-transformation of PDMs and GFM to the atomic orbital (AO) basis, and evaluation of gradients in the AO basis. For the largest member of the alkane set (C 10 H 22 ), the computational times for the gradient terms (with the cc-pVTZ basis set) are 2582.6 (CCSD) and 310.7 (DF-CCSD) min, respectively, a speed up of more than 8-folds. For gradient related terms, the DF approach avoids the usage of four-index electron repulsion integrals. Based on our previous study [U. Bozkaya, J. Chem. Phys. 141, 124108 (2014)], our formalism completely avoids construction or storage of the 4-index two-particle density matrix (TPDM), using instead 2- and 3-index TPDMs. The DF approach introduces negligible errors for equilibrium bond lengths and harmonic vibrational frequencies.

Investigation of the energy-averaged double transition density of isoscalar monopole excitations in medium-heavy mass spherical nuclei

Energy Technology Data Exchange (ETDEWEB)

Gorelik, M.L.; Shlomo, S. [National Research Nuclear University “MEPhI”, Moscow 115409 (Russian Federation); Cyclotron Institute, Texas A& M University, College Station, TX 77843 (United States); Tulupov, B.A. [National Research Nuclear University “MEPhI”, Moscow 115409 (Russian Federation); Institute for Nuclear Research, RAS, Moscow 117312 (Russian Federation); Urin, M.H., E-mail: urin@theor.mephi.ru [National Research Nuclear University “MEPhI”, Moscow 115409 (Russian Federation)

2016-11-15

The particle–hole dispersive optical model, developed recently, is applied to study properties of high-energy isoscalar monopole excitations in medium-heavy mass spherical nuclei. The energy-averaged strength functions of the isoscalar giant monopole resonance and its overtone in {sup 208}Pb are analyzed. In particular, we analyze the energy-averaged isoscalar monopole double transition density, the key quantity in the description of the hadron–nucleus inelastic scattering, and studied the validity of the factorization approximation using semi classical and microscopic one body transition densities, respectively, in calculating the cross sections for the excitation of isoscalar giant resonances by inelastic alpha scattering.

Screened Coulomb interactions in metallic alloys. II. Screening beyond the single-site and atomic-sphere approximations

DEFF Research Database (Denmark)

Ruban, Andrei; Simak, S.I.; Korzhavyi, P.A.

2002-01-01

-electron potential and energy. In the case of a random alloy such interactions can be accounted for only by lifting the atomic-sphere and single-site approximations, in order to include the polarization due to local environment effects. Nevertheless, a simple parametrization of the screened Coulomb interactions...... for the ordinary single-site methods, including the generalized perturbation method, is still possible. We obtained such a parametrization for bulk and surface NiPt alloys, which allows one to obtain quantitatively accurate effective interactions in this system....

Using the electron localization function to correct for confinement physics in semi-local density functional theory

International Nuclear Information System (INIS)

Hao, Feng; Mattsson, Ann E.; Armiento, Rickard

2014-01-01

We have previously proposed that further improved functionals for density functional theory can be constructed based on the Armiento-Mattsson subsystem functional scheme if, in addition to the uniform electron gas and surface models used in the Armiento-Mattsson 2005 functional, a model for the strongly confined electron gas is also added. However, of central importance for this scheme is an index that identifies regions in space where the correction provided by the confined electron gas should be applied. The electron localization function (ELF) is a well-known indicator of strongly localized electrons. We use a model of a confined electron gas based on the harmonic oscillator to show that regions with high ELF directly coincide with regions where common exchange energy functionals have large errors. This suggests that the harmonic oscillator model together with an index based on the ELF provides the crucial ingredients for future improved semi-local functionals. For a practical illustration of how the proposed scheme is intended to work for a physical system we discuss monoclinic cupric oxide, CuO. A thorough discussion of this system leads us to promote the cell geometry of CuO as a useful benchmark for future semi-local functionals. Very high ELF values are found in a shell around the O ions, and take its maximum value along the Cu–O directions. An estimate of the exchange functional error from the effect of electron confinement in these regions suggests a magnitude and sign that could account for the error in cell geometry

Properties of semi-infinite nuclei

International Nuclear Information System (INIS)

El-Jaick, L.J.; Kodama, T.

1976-04-01

Several relations among density distributions and energies of semi-infinite and infinite nuclei are iventigated in the framework of Wilets's statistical model. The model is shown to be consistent with the theorem of surface tension given by Myers and Swiatecki. Some numerical results are shown by using an appropriate nuclear matter equation of state

Parametric System Model for a Stirling Radioisotope Generator

Science.gov (United States)

Schmitz, Paul C.

2015-01-01

A Parametric System Model (PSM) was created in order to explore conceptual designs, the impact of component changes and power level on the performance of the Stirling Radioisotope Generator (SRG). Using the General Purpose Heat Source (GPHS approximately 250 Wth) modules as the thermal building block from which a SRG is conceptualized, trade studies are performed to understand the importance of individual component scaling on isotope usage. Mathematical relationships based on heat and power throughput, temperature, mass, and volume were developed for each of the required subsystems. The PSM uses these relationships to perform component- and system-level trades.

Ab initio quasi-particle approximation bandgaps of silicon nanowires calculated at density functional theory/local density approximation computational effort

Energy Technology Data Exchange (ETDEWEB)

Ribeiro, M., E-mail: ribeiro.jr@oorbit.com.br [Office of Operational Research for Business Intelligence and Technology, Principal Office, Buffalo, Wyoming 82834 (United States)

2015-06-21

Ab initio calculations of hydrogen-passivated Si nanowires were performed using density functional theory within LDA-1/2, to account for the excited states properties. A range of diameters was calculated to draw conclusions about the ability of the method to correctly describe the main trends of bandgap, quantum confinement, and self-energy corrections versus the diameter of the nanowire. Bandgaps are predicted with excellent accuracy if compared with other theoretical results like GW, and with the experiment as well, but with a low computational cost.

Ab initio quasi-particle approximation bandgaps of silicon nanowires calculated at density functional theory/local density approximation computational effort

International Nuclear Information System (INIS)

Ribeiro, M.

2015-01-01

Ab initio calculations of hydrogen-passivated Si nanowires were performed using density functional theory within LDA-1/2, to account for the excited states properties. A range of diameters was calculated to draw conclusions about the ability of the method to correctly describe the main trends of bandgap, quantum confinement, and self-energy corrections versus the diameter of the nanowire. Bandgaps are predicted with excellent accuracy if compared with other theoretical results like GW, and with the experiment as well, but with a low computational cost

Combining the modified Skyrme-like model and the local density approximation to determine the symmetry energy of nuclear matter

Science.gov (United States)

Liu, Jian; Ren, Zhongzhou; Xu, Chang

2018-07-01

Combining the modified Skyrme-like model and the local density approximation model, the slope parameter L of symmetry energy is extracted from the properties of finite nuclei with an improved iterative method. The calculations of the iterative method are performed within the framework of the spherical symmetry. By choosing 200 neutron rich nuclei on 25 isotopic chains as candidates, the slope parameter is constrained to be 50 MeV nuclear matter can be obtained together.

Parametrization of the radiation induced leakage current increase of NMOS transistors

International Nuclear Information System (INIS)

Backhaus, M.

2017-01-01

The increase of the leakage current of NMOS transistors during exposure to ionizing radiation is known and well studied. Radiation hardness by design techniques have been developed to mitigate this effect and have been successfully used. More recent developments in smaller feature size technologies do not make use of these techniques due to their drawbacks in terms of logic density and requirement of dedicated libraries. During operation the resulting increase of the supply current is a serious challenge and needs to be considered during the system design. A simple parametrization of the leakage current of NMOS transistors as a function of total ionizing dose is presented. The parametrization uses a transistor transfer characteristics of the parasitic transistor along the shallow trench isolation to describe the leakage current of the nominal transistor. Together with a parametrization of the number of positive charges trapped in the silicon dioxide and number of activated interface traps in the silicon to silicon dioxide interface the leakage current results as a function of the exposure time to ionizing radiation. This function is fitted to data of the leakage current of single transistors as well as to data of the supply current of full ASICs.

Parametric dependences of momentum pinch and Prandtl number in JET

DEFF Research Database (Denmark)

Tala, T.; Salmi, A.; Angioni, C.

2011-01-01

Several parametric scans have been performed to study momentum transport on JET. A neutral beam injection modulation technique has been applied to separate the diffusive and convective momentum transport terms. The magnitude of the inward momentum pinch depends strongly on the inverse density...... gradient length, with an experimental scaling for the pinch number being -Rvpinch/χφ = 1.2R/Ln +1.4. There is no dependence of the pinch number on collisionality, whereas the pinch seems to depend weakly on q-profile, the pinch number decreasing with increasing q. The Prandtl number was not found to depend...... either on R/Ln, collisionality or on q. The gyro-kinetic simulations show qualitatively similar dependence of the pinch number on R/Ln, but the dependence is weaker in the simulations. Gyro-kinetic simulations do not find any clear parametric dependence in the Prandtl number, in agreement...

Motivations of parametric studies

International Nuclear Information System (INIS)

Birac, C.

1988-01-01

The paper concerns the motivations of parametric studies in connection with the Programme for the Inspection of Steel Components PISC II. The objective of the PISC II exercise is to evaluate the effectiveness of current and advanced NDT techniques for inspection of reactor pressure vessel components. The parametric studies were initiated to determine the influence of some parameters on defect detection and dimensioning, and to increase the technical bases of the Round Robin Tests. A description is given of the content of the parametric studies including:- the effect of the defects' characteristics, the effect of equipment characteristics, the effect of cladding, and possible use of electromagnetic techniques. (U.K.)

Non-dipole angular anisotropy parameters of photoelectrons from semi-filled shell atoms

Energy Technology Data Exchange (ETDEWEB)

Amusia, M Ya [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Chernysheva, L V [Ioffe Physical-Technical Institute, St-Petersburg 194021 (Russian Federation)

2006-11-28

We present the results of calculations of outer and next to outer shell non-dipole angular anisotropy parameters of photoelectrons for semi-filled shell atoms in the Hartree-Fock (HF) one-electron approximation and in the frame of the spin polarized random phase approximation with exchange (SP RPAE) which takes into account inter-electron correlations. We demonstrate for the first time that this characteristic of the photoionization process is essentially sensitive to whether the photoelectron has the same or opposite spin orientation to that of the semi-filled shell.

Non-dipole angular anisotropy parameters of photoelectrons from semi-filled shell atoms

International Nuclear Information System (INIS)

Amusia, M Ya; Chernysheva, L V

2006-01-01

We present the results of calculations of outer and next to outer shell non-dipole angular anisotropy parameters of photoelectrons for semi-filled shell atoms in the Hartree-Fock (HF) one-electron approximation and in the frame of the spin polarized random phase approximation with exchange (SP RPAE) which takes into account inter-electron correlations. We demonstrate for the first time that this characteristic of the photoionization process is essentially sensitive to whether the photoelectron has the same or opposite spin orientation to that of the semi-filled shell

A Parametric k-Means Algorithm

Science.gov (United States)

Tarpey, Thaddeus

2007-01-01

Summary The k points that optimally represent a distribution (usually in terms of a squared error loss) are called the k principal points. This paper presents a computationally intensive method that automatically determines the principal points of a parametric distribution. Cluster means from the k-means algorithm are nonparametric estimators of principal points. A parametric k-means approach is introduced for estimating principal points by running the k-means algorithm on a very large simulated data set from a distribution whose parameters are estimated using maximum likelihood. Theoretical and simulation results are presented comparing the parametric k-means algorithm to the usual k-means algorithm and an example on determining sizes of gas masks is used to illustrate the parametric k-means algorithm. PMID:17917692

Assessment of time-dependent density functional theory with the restricted excitation space approximation for excited state calculations of large systems

Science.gov (United States)

Hanson-Heine, Magnus W. D.; George, Michael W.; Besley, Nicholas A.

2018-06-01

The restricted excitation subspace approximation is explored as a basis to reduce the memory storage required in linear response time-dependent density functional theory (TDDFT) calculations within the Tamm-Dancoff approximation. It is shown that excluding the core orbitals and up to 70% of the virtual orbitals in the construction of the excitation subspace does not result in significant changes in computed UV/vis spectra for large molecules. The reduced size of the excitation subspace greatly reduces the size of the subspace vectors that need to be stored when using the Davidson procedure to determine the eigenvalues of the TDDFT equations. Furthermore, additional screening of the two-electron integrals in combination with a reduction in the size of the numerical integration grid used in the TDDFT calculation leads to significant computational savings. The use of these approximations represents a simple approach to extend TDDFT to the study of large systems and make the calculations increasingly tractable using modest computing resources.

General 4–zero texture mass matrix parametrizations

International Nuclear Information System (INIS)

Barranco, J; Delepine, D; Lopez-Lozano, L

2014-01-01

It is performed the diagonalization of a non–Hermitian four–zero texture Yukawa matrix with a general formalism. This procedure leads to 3 possibilities to parametrize the relation between the fermion masses and the elements of the corresponding Yukawa matrix. Then, the matrices that diagonalize each Yukawa mass matrix are combined in order to obtain 9 different theoretical CKM or PMNS mixing matrices [1]. Through a χ 2 analysis, we have constrained the values of the remaining free parameters such as the theoretical mixing matrix matches the latest experimental measurements of the mixing matrices. This analysis was done without assuming any approximations. In the case of the quark sector, it is found that only four different theoretical mixing matrices are compatible with the actual high precision experimental measurement of the CKM matrix elements. For the lepton sector, where the masses of neutrinos are not known, we found that independently of the parametrization that have been chosen, the updated experimental measurements of the mixing angles in the PMNS matrix, imply a mass for the heaviest left–handed neutrino to be ∼ 0.05eV

Monitoring coastal marshes biomass with CASI: a comparison of parametric and non-parametric models

Science.gov (United States)

Mo, Y.; Kearney, M.

2017-12-01

Coastal marshes are important carbon sinks that face multiple natural and anthropogenic stresses. Optical remote sensing is a powerful tool for closely monitoring the biomass of coastal marshes. However, application of hyperspectral sensors on assessing the biomass of diverse coastal marsh ecosystems is limited. This study samples spectral and biophysical data from coastal freshwater, intermediate, brackish, and saline marshes in Louisiana, and develops parametric and non-parametric models for using the Compact Airborne Spectrographic Imager (CASI) to retrieve the marshes' biomass. Linear models and random forest models are developed from simulated CASI data (48 bands, 380-1050 nm, bandwidth 14 nm). Linear models are also developed using narrowband vegetation indices computed from all possible band combinations from the blue, red, and near infrared wavelengths. It is found that the linear models derived from the optimal narrowband vegetation indices provide strong predictions for the marshes' Leaf Area Index (LAI; R2 > 0.74 for ARVI), but not for their Aboveground Green Biomass (AGB; R2 > 0.25). The linear models derived from the simulated CASI data strongly predict the marshes' LAI (R2 = 0.93) and AGB (R2 = 0.71) and have 27 and 30 bands/variables in the final models through stepwise regression, respectively. The random forest models derived from the simulated CASI data also strongly predict the marshes' LAI and AGB (R2 = 0.91 and 0.84, respectively), where the most important variables for predicting LAI are near infrared bands at 784 and 756 nm and for predicting ABG are red bands at 684 and 670 nm. In sum, the random forest model is preferable for assessing coastal marsh biomass using CASI data as it offers high R2 for both LAI and AGB. The superior performance of the random forest model is likely to due to that it fully utilizes the full-spectrum data and makes no assumption of the approximate normality of the sampling population. This study offers solutions

Nonlocal theory of electromagnetic wave decay into two electromagnetic waves in a rippled density plasma channel

International Nuclear Information System (INIS)

Sati, Priti; Tripathi, V. K.

2012-01-01

Parametric decay of a large amplitude electromagnetic wave into two electromagnetic modes in a rippled density plasma channel is investigated. The channel is taken to possess step density profile besides a density ripple of axial wave vector. The density ripple accounts for the momentum mismatch between the interacting waves and facilitates nonlinear coupling. For a given pump wave frequency, the requisite ripple wave number varies only a little w.r.t. the frequency of the low frequency decay wave. The radial localization of electromagnetic wave reduces the growth rate of the parametric instability. The growth rate decreases with the frequency of low frequency electromagnetic wave.

Parametric Design Optimization Of A Novel Permanent Magnet Coupling Using Finite Element Analysis

DEFF Research Database (Denmark)

Högberg, Stig; Mijatovic, Nenad; Holbøll, Joachim

2014-01-01

A parametric design optimization routine has been applied to a novel magnetic coupling with improved recyclability. Coupling designs are modeled in a 3-D finite element environ- ment, and evaluated by three design objectives: pull-out torque, torque density by magnet mass, and torque density...... by total mass. Magnet and outer core thicknesses are varied discretely, whereas outer dimensions and air-gap length are kept constant. Comparative trends as a function of pole number and dimensions are depicted. A compromise exist between the design objectives, in which favoring one might reduce the other...

Investigation of Parametric Instability of the Planetary Gear under Speed Fluctuations

Directory of Open Access Journals (Sweden)

Xinghui Qiu

2017-01-01

Full Text Available Planetary gear is widely used in engineering and usually has symmetrical structure. As the number of teeth in contact changes during rotation, the time-varying mesh stiffness parametrically excites the planetary gear and may cause severe vibrations and instabilities. Taking speed fluctuations into account, the time-varying mesh stiffness is frequency modulated, and therefore sideband instabilities may arise and original instabilities are significantly affected. Considering two different speed fluctuations, original and sideband instabilities are numerically and analytically investigated. A rotational lumped-parameter model of the planetary gear is developed, in which the time-varying mesh stiffness, input speed fluctuations, and damping are considered. Closed-form approximations of instability boundaries for primary and combination instabilities are obtained by perturbation analysis and verified by numerical analysis. The effects of speed fluctuations and damping on parametric instability are systematically examined. Because of the frequency modulation, whether a parametric instability occurs cannot be simply predicted by the planet meshing phase which is applicable to constant speed. Besides adjusting the planet meshing phase, speed fluctuation supplies a new thought to minimize certain instability by adjusting the amplitude or frequency of the speed fluctuation. Both original and sideband instabilities are shrunken by damping, and speed fluctuation further shrinks the original instability.

Approximate treatment of semicore states in GW calculations with application to Au clusters.

Science.gov (United States)

Xian, Jiawei; Baroni, Stefano; Umari, P

2014-03-28

We address the treatment of transition metal atoms in GW electronic-structure calculations within the plane-wave pseudo-potential formalism. The contributions of s and p semi-core electrons to the self-energy, which are essential to grant an acceptable accuracy, are dealt with using a recently proposed scheme whereby the exchange components are treated exactly at the G0W0 level, whereas a suitable approximation to the correlation components is devised. This scheme is benchmarked for small gold nano-clusters, resulting in ionization potentials, electron affinities, and density of states in very good agreement with those obtained from calculations where s and p semicore states are treated as valence orbitals, and allowing us to apply this same scheme to clusters of intermediate size, Au20 and Au32, that would be otherwise very difficult to deal with.

Approximate treatment of semicore states in GW calculations with application to Au clusters

Energy Technology Data Exchange (ETDEWEB)

Xian, Jiawei [SISSA – Scuola Internazionale Superiore di Studi Avanzati, Via Bonomea 265, I-34136 Trieste (Italy); Baroni, Stefano [SISSA – Scuola Internazionale Superiore di Studi Avanzati, Via Bonomea 265, I-34136 Trieste (Italy); CNR-IOM Democritos, Theory-Elettra group, Trieste (Italy); Umari, P., E-mail: paolo.umari@unipd.it [CNR-IOM Democritos, Theory-Elettra group, Trieste (Italy); Dipartimento di Fisica e Astronomia, Università di Padova, Via Marzolo 8, I-35131 Padova (Italy)

2014-03-28

We address the treatment of transition metal atoms in GW electronic-structure calculations within the plane-wave pseudo-potential formalism. The contributions of s and p semi-core electrons to the self-energy, which are essential to grant an acceptable accuracy, are dealt with using a recently proposed scheme whereby the exchange components are treated exactly at the G{sub 0}W{sub 0} level, whereas a suitable approximation to the correlation components is devised. This scheme is benchmarked for small gold nano-clusters, resulting in ionization potentials, electron affinities, and density of states in very good agreement with those obtained from calculations where s and p semicore states are treated as valence orbitals, and allowing us to apply this same scheme to clusters of intermediate size, Au{sub 20} and Au{sub 32}, that would be otherwise very difficult to deal with.

Approximate treatment of semicore states in GW calculations with application to Au clusters

International Nuclear Information System (INIS)

Xian, Jiawei; Baroni, Stefano; Umari, P.

2014-01-01

We address the treatment of transition metal atoms in GW electronic-structure calculations within the plane-wave pseudo-potential formalism. The contributions of s and p semi-core electrons to the self-energy, which are essential to grant an acceptable accuracy, are dealt with using a recently proposed scheme whereby the exchange components are treated exactly at the G 0 W 0 level, whereas a suitable approximation to the correlation components is devised. This scheme is benchmarked for small gold nano-clusters, resulting in ionization potentials, electron affinities, and density of states in very good agreement with those obtained from calculations where s and p semicore states are treated as valence orbitals, and allowing us to apply this same scheme to clusters of intermediate size, Au 20 and Au 32 , that would be otherwise very difficult to deal with

Planar Parametrization in Isogeometric Analysis

DEFF Research Database (Denmark)

Gravesen, Jens; Evgrafov, Anton; Nguyen, Dang-Manh

2012-01-01

Before isogeometric analysis can be applied to solving a partial differential equation posed over some physical domain, one needs to construct a valid parametrization of the geometry. The accuracy of the analysis is affected by the quality of the parametrization. The challenge of computing...... and maintaining a valid geometry parametrization is particularly relevant in applications of isogemetric analysis to shape optimization, where the geometry varies from one optimization iteration to another. We propose a general framework for handling the geometry parametrization in isogeometric analysis and shape...... are suitable for our framework. The non-linear methods we consider are based on solving a constrained optimization problem numerically, and are divided into two classes, geometry-oriented methods and analysis-oriented methods. Their performance is illustrated through a few numerical examples....

Suppression of Growth by Multiplicative White Noise in a Parametric Resonant System

Science.gov (United States)

Ishihara, Masamichi

2015-02-01

The growth of the amplitude in a Mathieu-like equation with multiplicative white noise is studied. To obtain an approximate analytical expression for the exponent at the extremum on parametric resonance regions, a time-interval width is introduced. To determine the exponents numerically, the stochastic differential equations are solved by a symplectic numerical method. The Mathieu-like equation contains a parameter α determined by the intensity of noise and the strength of the coupling between the variable and noise; without loss of generality, only non-negative α can be considered. The exponent is shown to decrease with α, reach a minimum and increase after that. The minimum exponent is obtained analytically and numerically. As a function of α, the minimum at α≠0, occurs on the parametric resonance regions of α=0. This minimum indicates suppression of growth by multiplicative white noise.

Range-separated density-functional theory for molecular excitation energies

International Nuclear Information System (INIS)

Rebolini, E.

2014-01-01

Linear-response time-dependent density-functional theory (TDDFT) is nowadays a method of choice to compute molecular excitation energies. However, within the usual adiabatic semi-local approximations, it is not able to describe properly Rydberg, charge-transfer or multiple excitations. Range separation of the electronic interaction allows one to mix rigorously density-functional methods at short range and wave function or Green's function methods at long range. When applied to the exchange functional, it already corrects most of these deficiencies but multiple excitations remain absent as they need a frequency-dependent kernel. In this thesis, the effects of range separation are first assessed on the excitation energies of a partially-interacting system in an analytic and numerical study in order to provide guidelines for future developments of range-separated methods for excitation energy calculations. It is then applied on the exchange and correlation TDDFT kernels in a single-determinant approximation in which the long-range part of the correlation kernel vanishes. A long-range frequency-dependent second-order correlation kernel is then derived from the Bethe-Salpeter equation and added perturbatively to the range-separated TDDFT kernel in order to take into account the effects of double excitations. (author)

Parametric x-ray FEL operating with external Bragg reflectors

International Nuclear Information System (INIS)

Baryshevsky, V.G.; Batrakov, K.G.; Dubovskaya, I.Ya.

1995-01-01

In the crystal X-ray FELs using channeling and parametric quasi-Cherenkov mechanisms of spontaneous radiation were considered as versions of FEL allowing, in principle, to obtain coherent X-ray source. In this case a crystal is both radiator and resonator for X-rays emitted by a particle beam passing through crystal. However, it is well-known that a beam current density required for lasing is extremely high in X-ray spectral range for any radiation mechanisms and it is very important to find a way to lower its magnitude. The application of three-dimensional distributed feedback formed by dynamical diffraction of emitted photons permitted to reduce starting beam current density 10 2 -10 4 times up to 10 9 . One of ways to lower the starting current is the formation of multi-wave distributed feedback the another one is the application of external reflectors. The thing is that lasing regime was shown to be produced at frequencies in the vicinity of degeneration point for roots of dispersion equation describing radiation modes excited in an active medium (crystal plus particle beam). Unfortunately, in case of parametric quasi-Cherenkov FEL this region coincides with the region of strong self-absorption of radiation inside a crystal. That fact, obviously, increases the starting beam current. In this report we have shown that the application of external Bragg reflectors gives the possibility to lower radiation self-absorption inside a crystal by modifying radiation modes excited in the active medium under consideration. The corresponding dispersion equation and the expression for excited modes are derived. The generation equation determining starting conditions for lasing is obtained. Using these expressions we have shown that the application of external Bragg reflectors permits to reduce starting beam current density more than 10 times

Influence of spatial beam inhomogeneities on the parameters of a petawatt laser system based on multi-stage parametric amplification

International Nuclear Information System (INIS)

Frolov, S A; Trunov, V I; Pestryakov, Efim V; Leshchenko, V E

2013-01-01

We have developed a technique for investigating the evolution of spatial inhomogeneities in high-power laser systems based on multi-stage parametric amplification. A linearised model of the inhomogeneity development is first devised for parametric amplification with the small-scale self-focusing taken into account. It is shown that the application of this model gives the results consistent (with high accuracy and in a wide range of inhomogeneity parameters) with the calculation without approximations. Using the linearised model, we have analysed the development of spatial inhomogeneities in a petawatt laser system based on multi-stage parametric amplification, developed at the Institute of Laser Physics, Siberian Branch of the Russian Academy of Sciences (ILP SB RAS). (control of laser radiation parameters)

Volume generation of negative ions in high density hydrogen discharges

International Nuclear Information System (INIS)

Hiskes, J.R.; Karo, A.M.

1983-01-01

A parametric survey is made of a high-density tandem two-chamber hydrogen negative ion system. The optimum extracted negative ion current densities are sensitive to the atom concentration in the discharge and to the system scale length. For scale lengths ranging from 10 cm to 0.1 cm optimum current densities range from of order 1 to 100 mA cm -2 , respectively

Developing a Parametric Urban Design Tool

DEFF Research Database (Denmark)

Steinø, Nicolai; Obeling, Esben

2014-01-01

Parametric urban design is a potentially powerful tool for collaborative urban design processes. Rather than making one- off designs which need to be redesigned from the ground up in case of changes, parametric design tools make it possible keep the design open while at the same time allowing...... for a level of detailing which is high enough to facilitate an understan- ding of the generic qualities of proposed designs. Starting from a brief overview of parametric design, this paper presents initial findings from the development of a parametric urban design tool with regard to developing a structural...... logic which is flexible and expandable. It then moves on to outline and discuss further development work. Finally, it offers a brief reflection on the potentials and shortcomings of the software – CityEngine – which is used for developing the parametric urban design tool....

Comparison of approximations in density functional theory calculations: Energetics and structure of binary oxides

Science.gov (United States)

Hinuma, Yoyo; Hayashi, Hiroyuki; Kumagai, Yu; Tanaka, Isao; Oba, Fumiyasu

2017-09-01

High-throughput first-principles calculations based on density functional theory (DFT) are a powerful tool in data-oriented materials research. The choice of approximation to the exchange-correlation functional is crucial as it strongly affects the accuracy of DFT calculations. This study compares performance of seven approximations, six of which are based on Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) with and without Hubbard U and van der Waals corrections (PBE, PBE+U, PBED3, PBED3+U, PBEsol, and PBEsol+U), and the strongly constrained and appropriately normed (SCAN) meta-GGA on the energetics and crystal structure of elementary substances and binary oxides. For the latter, only those with closed-shell electronic structures are considered, examples of which include C u2O , A g2O , MgO, ZnO, CdO, SnO, PbO, A l2O3 , G a2O3 , I n2O3 , L a2O3 , B i2O3 , Si O2 , Sn O2 , Pb O2 , Ti O2 , Zr O2 , Hf O2 , V2O5 , N b2O5 , T a2O5 , Mo O3 , and W O3 . Prototype crystal structures are selected from the Inorganic Crystal Structure Database (ICSD) and cation substitution is used to make a set of existing and hypothetical oxides. Two indices are proposed to quantify the extent of lattice and internal coordinate relaxation during a calculation. The former is based on the second invariant and determinant of the transformation matrix of basis vectors from before relaxation to after relaxation, and the latter is derived from shifts of internal coordinates of atoms in the unit cell. PBED3, PBEsol, and SCAN reproduce experimental lattice parameters of elementary substances and oxides well with few outliers. Notably, PBEsol and SCAN predict the lattice parameters of low dimensional structures comparably well with PBED3, even though these two functionals do not explicitly treat van der Waals interactions. SCAN gives formation enthalpies and Gibbs free energies closest to experimental data, with mean errors (MEs) of 0.01 and -0.04 eV, respectively, and root

Convective cell excitation by inertial Alfven waves in a low density plasma

International Nuclear Information System (INIS)

Pokhotelov, O.A.; Onishchenko, O.G.; Sagdeev, R.Z.; Srenflo, L.; Balikhin, M.A.

2005-01-01

The parametric interaction of inertial Alfven waves with large-scale convective cells in a low-density plasma is investigated. It is shown that, in plasmas where the Alfven velocity is comparable to or exceeds the speed of light, the parametric interaction is substantially suppressed. A compact expression for the optimal scale and instability growth rate of the fastest growing mode is obtained [ru

Semiclassical Wigner distribution for a two-mode entangled state generated by an optical parametric oscillator

International Nuclear Information System (INIS)

Dechoum, K.; Hahn, M. D.; Khoury, A. Z.; Vallejos, R. O.

2010-01-01

We derive the steady-state solution of the Fokker-Planck equation that describes the dynamics of the nondegenerate optical parametric oscillator in the truncated Wigner representation of the density operator. We assume that the pump mode is strongly damped, which permits its adiabatic elimination. When the elimination is correctly executed, the resulting stochastic equations contain multiplicative noise terms and do not admit a potential solution. However, we develop a heuristic scheme leading to a satisfactory steady-state solution. This provides a clear view of the intracavity two-mode entangled state valid in all operating regimes of the optical parametric oscillator. A non-Gaussian distribution is obtained for the above threshold solution.

Parametric uncertainty modeling for robust control

DEFF Research Database (Denmark)

Rasmussen, K.H.; Jørgensen, Sten Bay

1999-01-01

The dynamic behaviour of a non-linear process can often be approximated with a time-varying linear model. In the presented methodology the dynamics is modeled non-conservatively as parametric uncertainty in linear lime invariant models. The obtained uncertainty description makes it possible...... to perform robustness analysis on a control system using the structured singular value. The idea behind the proposed method is to fit a rational function to the parameter variation. The parameter variation can then be expressed as a linear fractional transformation (LFT), It is discussed how the proposed...... point changes. It is shown that a diagonal PI control structure provides robust performance towards variations in feed flow rate or feed concentrations. However including both liquid and vapor flow delays robust performance specifications cannot be satisfied with this simple diagonal control structure...

Ionospheric modification and parametric instabilities

International Nuclear Information System (INIS)

Fejer, J.A.

1979-01-01

Thresholds and linear growth rates for stimulated Brillouin and Raman scattering and for the parametric decay instability are derived by using arguments of energy transfer. For this purpose an expression for the ponderomotive force is derived. Conditions under which the partial pressure force due to differential dissipation exceeds the ponderomotive force are also discussed. Stimulated Brillouin and Raman scattering are weakly excited by existing incoherent backscatter radars. The parametric decay instability is strongly excited in ionospheric heating experiments. Saturation theories of the parametric decay instability are therefore described. After a brief discussion of the purely growing instability the effect of using several pumps is discussed as well as the effects of inhomogenicity. Turning to detailed theories of ionospheric heating, artificial spread F is discussed in terms of a purely growing instability where the nonlinearity is due to dissipation. Field-aligned short-scale striations are explained in terms of dissipation of the parametrically excited Langmuir waves (plasma oscillations): they might be further amplified by an explosive instability (except the magnetic equator). Broadband absorption is probably responsible for the 'overshoot' effect: the initially observed level of parametrically excited Langmuir waves is much higher than the steady state level

Detection of Parametric Roll on Ships

DEFF Research Database (Denmark)

Galeazzi, Roberto; Blanke, Mogens; Poulsen, Niels Kjølstad

2012-01-01

phenomenon could make the navigator change ship’s speed and heading, and these remedial actions could make the vessel escape the bifurcation. This chapter proposes non-parametric methods to detect the onset of parametric roll resonance. Theoretical conditions for parametric resonance are re...... on experimental data from towing tank tests and data from a container ship passing an Atlantic storm....

An equivalent method for optimization of particle tuned mass damper based on experimental parametric study

Science.gov (United States)

Lu, Zheng; Chen, Xiaoyi; Zhou, Ying

2018-04-01

A particle tuned mass damper (PTMD) is a creative combination of a widely used tuned mass damper (TMD) and an efficient particle damper (PD) in the vibration control area. The performance of a one-storey steel frame attached with a PTMD is investigated through free vibration and shaking table tests. The influence of some key parameters (filling ratio of particles, auxiliary mass ratio, and particle density) on the vibration control effects is investigated, and it is shown that the attenuation level significantly depends on the filling ratio of particles. According to the experimental parametric study, some guidelines for optimization of the PTMD that mainly consider the filling ratio are proposed. Furthermore, an approximate analytical solution based on the concept of an equivalent single-particle damper is proposed, and it shows satisfied agreement between the simulation and experimental results. This simplified method is then used for the preliminary optimal design of a PTMD system, and a case study of a PTMD system attached to a five-storey steel structure following this optimization process is presented.

A general range-separated double-hybrid density-functional theory.

Science.gov (United States)

Kalai, Cairedine; Toulouse, Julien

2018-04-28

A range-separated double-hybrid (RSDH) scheme which generalizes the usual range-separated hybrids and double hybrids is developed. This scheme consistently uses a two-parameter Coulomb-attenuating-method (CAM)-like decomposition of the electron-electron interaction for both exchange and correlation in order to combine Hartree-Fock exchange and second-order Møller-Plesset (MP2) correlation with a density functional. The RSDH scheme relies on an exact theory which is presented in some detail. Several semi-local approximations are developed for the short-range exchange-correlation density functional involved in this scheme. After finding optimal values for the two parameters of the CAM-like decomposition, the RSDH scheme is shown to have a relatively small basis dependence and to provide atomization energies, reaction barrier heights, and weak intermolecular interactions globally more accurate or comparable to range-separated MP2 or standard MP2. The RSDH scheme represents a new family of double hybrids with minimal empiricism which could be useful for general chemical applications.

The influence of parametric and external noise in act-and-wait control with delayed feedback.

Science.gov (United States)

Wang, Jiaxing; Kuske, Rachel

2017-11-01

We apply several novel semi-analytic approaches for characterizing and calculating the effects of noise in a system with act-and-wait control. For concrete illustration, we apply these to a canonical balance model for an inverted pendulum to study the combined effect of delay and noise within the act-and-wait setting. While the act-and-wait control facilitates strong stabilization through deadbeat control, a comparison of different models with continuous vs. discrete updating of the control strategy in the active period illustrates how delays combined with the imprecise application of the control can seriously degrade the performance. We give several novel analyses of a generalized act-and-wait control strategy, allowing flexibility in the updating of the control strategy, in order to understand the sensitivities to delays and random fluctuations. In both the deterministic and stochastic settings, we give analytical and semi-analytical results that characterize and quantify the dynamics of the system. These results include the size and shape of stability regions, densities for the critical eigenvalues that capture the rate of reaching the desired stable equilibrium, and amplification factors for sustained fluctuations in the context of external noise. They also provide the dependence of these quantities on the length of the delay and the active period. In particular, we see that the combined influence of delay, parametric error, or external noise and on-off control can qualitatively change the dynamics, thus reducing the robustness of the control strategy. We also capture the dependence on how frequently the control is updated, allowing an interpolation between continuous and frequent updating. In addition to providing insights for these specific models, the methods we propose are generalizable to other settings with noise, delay, and on-off control, where analytical techniques are otherwise severely scarce.

Surface properties of semi-infinite Fermi systems

International Nuclear Information System (INIS)

Campi, X.; Stringari, S.

1979-10-01

A functional relation between the kinetic energy density and the total density is used to analyse the surface properties of semi-infinite Fermi systems. One find an explicit expression for the surface thickness in which the role of the infinite matter compressibility, binding energy and non-locality effects is clearly shown. The method, which holds both for nuclear and electronic systems (liquid metals), yields a very simple relation between the surface thickness and the surface energy

Supersonic beams at high particle densities: model description beyond the ideal gas approximation.

Science.gov (United States)

Christen, Wolfgang; Rademann, Klaus; Even, Uzi

2010-10-28

Supersonic molecular beams constitute a very powerful technique in modern chemical physics. They offer several unique features such as a directed, collision-free flow of particles, very high luminosity, and an unsurpassed strong adiabatic cooling during the jet expansion. While it is generally recognized that their maximum flow velocity depends on the molecular weight and the temperature of the working fluid in the stagnation reservoir, not a lot is known on the effects of elevated particle densities. Frequently, the characteristics of supersonic beams are treated in diverse approximations of an ideal gas expansion. In these simplified model descriptions, the real gas character of fluid systems is ignored, although particle associations are responsible for fundamental processes such as the formation of clusters, both in the reservoir at increased densities and during the jet expansion. In this contribution, the various assumptions of ideal gas treatments of supersonic beams and their shortcomings are reviewed. It is shown in detail that a straightforward thermodynamic approach considering the initial and final enthalpy is capable of characterizing the terminal mean beam velocity, even at the liquid-vapor phase boundary and the critical point. Fluid properties are obtained using the most accurate equations of state available at present. This procedure provides the opportunity to naturally include the dramatic effects of nonideal gas behavior for a large variety of fluid systems. Besides the prediction of the terminal flow velocity, thermodynamic models of isentropic jet expansions permit an estimate of the upper limit of the beam temperature and the amount of condensation in the beam. These descriptions can even be extended to include spinodal decomposition processes, thus providing a generally applicable tool for investigating the two-phase region of high supersaturations not easily accessible otherwise.

Global scaling for semi-quantitative analysis in FP-CIT SPECT.

Science.gov (United States)

Kupitz, D; Apostolova, I; Lange, C; Ulrich, G; Amthauer, H; Brenner, W; Buchert, R

2014-01-01

Semi-quantitative characterization of dopamine transporter availability from single photon emission computed tomography (SPECT) with 123I-ioflupane (FP-CIT) is based on uptake ratios relative to a reference region. The aim of this study was to evaluate the whole brain as reference region for semi-quantitative analysis of FP-CIT SPECT. The rationale was that this might reduce statistical noise associated with the estimation of non-displaceable FP-CIT uptake. 150 FP-CIT SPECTs were categorized as neurodegenerative or non-neurodegenerative by an expert. Semi-quantitative analysis of specific binding ratios (SBR) was performed with a custom-made tool based on the Statistical Parametric Mapping software package using predefined regions of interest (ROIs) in the anatomical space of the Montreal Neurological Institute. The following reference regions were compared: predefined ROIs for frontal and occipital lobe and whole brain (without striata, thalamus and brainstem). Tracer uptake in the reference region was characterized by the mean, median or 75th percentile of its voxel intensities. The area (AUC) under the receiver operating characteristic curve was used as performance measure. The highest AUC of 0.973 was achieved by the SBR of the putamen with the 75th percentile in the whole brain as reference. The lowest AUC for the putamen SBR of 0.937 was obtained with the mean in the frontal lobe as reference. We recommend the 75th percentile in the whole brain as reference for semi-quantitative analysis in FP-CIT SPECT. This combination provided the best agreement of the semi-quantitative analysis with visual evaluation of the SPECT images by an expert and, therefore, is appropriate to support less experienced physicians.

Explicit approximations to estimate the perturbative diffusivity in the presence of convectivity and damping. I. Semi-infinite slab approximations

NARCIS (Netherlands)

Berkel, van M.; Zwart, Heiko J.; Tamura, N.; Hogeweij, G.M.D.; Inagaki, S.; de Baar, M.R.; Ida, K.

2014-01-01

In this paper, a number of new approximations are introduced to estimate the perturbative diffusivity (χ), convectivity (V), and damping (τ) in cylindrical geometry. For this purpose, the harmonic components of heat waves induced by localized deposition of modulated power are used. The

Size-dependent error of the density functional theory ionization potential in vacuum and solution.

Science.gov (United States)

Sosa Vazquez, Xochitl A; Isborn, Christine M

2015-12-28

Density functional theory is often the method of choice for modeling the energetics of large molecules and including explicit solvation effects. It is preferable to use a method that treats systems of different sizes and with different amounts of explicit solvent on equal footing. However, recent work suggests that approximate density functional theory has a size-dependent error in the computation of the ionization potential. We here investigate the lack of size-intensivity of the ionization potential computed with approximate density functionals in vacuum and solution. We show that local and semi-local approximations to exchange do not yield a constant ionization potential for an increasing number of identical isolated molecules in vacuum. Instead, as the number of molecules increases, the total energy required to ionize the system decreases. Rather surprisingly, we find that this is still the case in solution, whether using a polarizable continuum model or with explicit solvent that breaks the degeneracy of each solute, and we find that explicit solvent in the calculation can exacerbate the size-dependent delocalization error. We demonstrate that increasing the amount of exact exchange changes the character of the polarization of the solvent molecules; for small amounts of exact exchange the solvent molecules contribute a fraction of their electron density to the ionized electron, but for larger amounts of exact exchange they properly polarize in response to the cationic solute. In vacuum and explicit solvent, the ionization potential can be made size-intensive by optimally tuning a long-range corrected hybrid functional.

On the semi-classical approximation to the wave function of the universe and its stochastic interpretation

International Nuclear Information System (INIS)

Pollock, M.D.

1988-01-01

In quantum cosmology, a wave function Ψ for a given theory can be obtained by solving the Wheeler-DeWitt equation, using the semi-classical approximation to the path integral over euclidean metrics to impose the boundary condition, as described by Hawking and his collaborators. If the universe is expanding as a quasi-de Sitter space-time, then it is possible to derive a Fokker-Planck equation for the probability distribution P, as shown by Starobinsky. Arguing by analogy with quantum mechanics in flat space-time, one would expect that P ∝ ΨΨ * . We examine this assertion by reference to the scale-invariant theory L = -1/24 βR 2 , whose wave function has been calculated in mini-superspace by Horowitz, and whose classical solutions are de Sitter space-times. It appears that deviations from the relation P ∝ ΨΨ * are attributable to long-wavelength fluctuations δΦ e ≅ H/2π in the effective inflaton field Φ c =√(βR)=√(12β) H. Their existence is taken into account in the derivation of the Fokker-Planck equation, but not in the derivation of Ψ when this is restricted to mini-superspace. In the limit β → ∞, we find that δΦ e /Φ c → 0 and that P ∝ ΨΨ * . The scale-invariant theory L = (1/2εφ 2 R-1/4λΦ 4 ) can be similarly analyzed. Inclusion of a kinetic term 1/2Φ; k Φ ;k destroys this similarity, which is restored however upon addition of a term (-1/24βR 2 ). (orig.)

Parametric optimal control of uncertain systems under an optimistic value criterion

Science.gov (United States)

Li, Bo; Zhu, Yuanguo

2018-01-01

It is well known that the optimal control of a linear quadratic model is characterized by the solution of a Riccati differential equation. In many cases, the corresponding Riccati differential equation cannot be solved exactly such that the optimal feedback control may be a complex time-oriented function. In this article, a parametric optimal control problem of an uncertain linear quadratic model under an optimistic value criterion is considered for simplifying the expression of optimal control. Based on the equation of optimality for the uncertain optimal control problem, an approximation method is presented to solve it. As an application, a two-spool turbofan engine optimal control problem is given to show the utility of the proposed model and the efficiency of the presented approximation method.

High-frequency emissions during the propagation of an electron beam in a high-density plasma

International Nuclear Information System (INIS)

Lalita and Tripathi, V.K.

1988-01-01

A relativistic annular electron beam passing through a high-density plasma excites Langmuir waves via Cerenkov interaction. The Langmuir waves are backscattered off ions via nonlinear ion Landau damping. At moderately high amplitudes these waves are parametrically up-converted by the beam into high-frequency electromagnetic radiation, as observed in some recent experiments. A nonlocal theory of this process is developed in a cylindrical geometry. It is seen that the growth rate of the Langmuir wave scales as one-third power of beam density. The growth rate of parametric instability scales as one-fourth power of beam density and the square root of beam thickness

Hybrid Model of Inhomogeneous Solar Wind Plasma Heating by Alfven Wave Spectrum: Parametric Studies

Science.gov (United States)

Ofman, L.

2010-01-01

Observations of the solar wind plasma at 0.3 AU and beyond show that a turbulent spectrum of magnetic fluctuations is present. Remote sensing observations of the corona indicate that heavy ions are hotter than protons and their temperature is anisotropic (T(sub perpindicular / T(sub parallel) >> 1). We study the heating and the acceleration of multi-ion plasma in the solar wind by a turbulent spectrum of Alfvenic fluctuations using a 2-D hybrid numerical model. In the hybrid model the protons and heavy ions are treated kinetically as particles, while the electrons are included as neutralizing background fluid. This is the first two-dimensional hybrid parametric study of the solar wind plasma that includes an input turbulent wave spectrum guided by observation with inhomogeneous background density. We also investigate the effects of He++ ion beams in the inhomogeneous background plasma density on the heating of the solar wind plasma. The 2-D hybrid model treats parallel and oblique waves, together with cross-field inhomogeneity, self-consistently. We investigate the parametric dependence of the perpendicular heating, and the temperature anisotropy in the H+-He++ solar wind plasma. It was found that the scaling of the magnetic fluctuations power spectrum steepens in the higher-density regions, and the heating is channeled to these regions from the surrounding lower-density plasma due to wave refraction. The model parameters are applicable to the expected solar wind conditions at about 10 solar radii.

Statistical mechanics of semi-supervised clustering in sparse graphs

International Nuclear Information System (INIS)

Ver Steeg, Greg; Galstyan, Aram; Allahverdyan, Armen E

2011-01-01

We theoretically study semi-supervised clustering in sparse graphs in the presence of pair-wise constraints on the cluster assignments of nodes. We focus on bi-cluster graphs and study the impact of semi-supervision for varying constraint density and overlap between the clusters. Recent results for unsupervised clustering in sparse graphs indicate that there is a critical ratio of within-cluster and between-cluster connectivities below which clusters cannot be recovered with better than random accuracy. The goal of this paper is to examine the impact of pair-wise constraints on the clustering accuracy. Our results suggest that the addition of constraints does not provide automatic improvement over the unsupervised case. When the density of the constraints is sufficiently small, their only impact is to shift the detection threshold while preserving the criticality. Conversely, if the density of (hard) constraints is above the percolation threshold, the criticality is suppressed and the detection threshold disappears

Parametric optimization of the MVC desalination plant with thermomechanical compressor

Science.gov (United States)

Blagin, E. V.; Biryuk, V. V.; Anisimov, M. Y.; Shimanov, A. A.; Gorshkalev, A. A.

2018-03-01

This article deals with parametric optimization of the Mechanical Vapour Compression (MVC) desalination plant with thermomechanical compressor. In this plants thermocompressor is used instead of commonly used centrifugal compressor. Influence of two main parameters was studied. These parameters are: inlet pressure and number of stages. Analysis shows that it is possible to achieve better plant performance in comparison with traditional MVC plant. But is required reducing the number of stages and utilization of low or high initial pressure with power consumption maximum at approximately 20-30 kPa.

Solid neutron matter the energy density in the relativistic harmonic approximation

International Nuclear Information System (INIS)

Cattani, M.; Fernandes, N.C.

A relativistic expression for the energy density as a function of particle density for solid neutron matter is obtained using Dirac's equation with a truncated harmonic potential. Ultrabaric and superluminous effects are not found in our approach [pt

PARAMETRIC DIAGNOSTICS OF THE CENTRIFUGAL SUPERCHARGER'S TECHNICAL CONDITION DURING OPERATION

Directory of Open Access Journals (Sweden)

Regina A. Khuramshina

2017-01-01

Full Text Available Abstract. Objectives The main aim is to develop a mathematical model of a centrifugal compressor and carry out a parametric diagnostics of a centrifugal supercharger's technical condition during operation. Methods  A model is proposed for calculating the thermodynamic properties of natural gas, reducing the parameters of a centrifugal compressor to the initial conditions and to the rotation frequency, as well as the integral indicators of the supercharger's technical state. The technical state of the gas path of the centrifugal supercharger of the compressor unit is determined by the parametric diagnostic method. Results  The software implementation of the mathematical model of centrifugal compressor is carried out using a DVIGwT PC. The analysis of calculations indicates that the model is appropriate, with the error being due to taking into account the properties of iso-butane and i-hexane, in contrast with the VNIIGAZ technique. The evaluation studies of a centrifugal compressor's state are indicative of the presence or absence of its defects. Conclusion  Among a number of the diagnostic methods for evaluating a centrifugal supercharger, the most effective is vibrodiagnostics. However, the search for malfunctions and nascent defects in the flowing part of the centrifugal compressor cannot be limited only to vibrodiagnostic data, which provides about 60% of the reliable information about the state of the gas-air tract. About 20% of the compressor's malfunctions and approximately half of the dangerous modes of the supercharger's flow-through part is detected using thermogasdynamic parametric analysis (parametric diagnostics. The main difficulty of the control over the technical state of the flow-through part of the centrifugal supercharger is in the complication of the quantitative evaluation of the processes taking place in the supercharger, which leads to problems in providing reliable diagnosis during a reasonable period of time.

Parametric plasma surface instabilities with p-polarized radiation

International Nuclear Information System (INIS)

Rappaport, H.L.

1994-01-01

The authors argue that parametric plasma surface mode excitation is a viable broadband instability mechanism in the microwave regime since the wavelength of incident radiation can be large compared to plasma ion density gradient scale lengths. The authors restrict their attention to plasmas which are uniform in the planes perpendicular to the density gradients. The boundary region is characterized by three parameters: (1) the ion density gradient length; (2) the electron Debye length; and (3) the excursion of boundary electrons as they move in response to monochromatic p-polarized radiation. A thin vacuum plasma transition layer, in which the ion density gradient scale length is large compared with the Debye length and the electron excursion, is included in the analysis of plasma stability. The recently proposed Lagrangian Frame Two-Plasmon Decay mode (LFTPD) is investigated in the regime in which the instability is not resonantly coupled to surface waves propagating along the boundary region. In this case they have found both spatially dependent growth rate profiles and spatially dependent transit layer magnetic fields due to nonlinear surface currents. LFTPD growth rate profiles are displayed as a function of pump amplitude. The results of a time domain simulation of this mode is also shown

Effects of Boundary Conditions on the Parametric Resonance of Cylindrical Shells under Axial Loading

Directory of Open Access Journals (Sweden)

T.Y. Ng

1998-01-01

Full Text Available In this paper, a formulation for the dynamic stability analysis of circular cylindrical shells under axial compression with various boundary conditions is presented. The present study uses Love’s first approximation theory for thin shells and the characteristic beam functions as approximate axial modal functions. Applying the Ritz procedure to the Lagrangian energy expression yields a system of Mathieu–Hill equations the stability of which is analyzed using Bolotin’s method. The present study examines the effects of different boundary conditions on the parametric response of homogeneous isotropic cylindrical shells for various transverse modes and length parameters.

Carbon storage potential in size–density fractions from semi-natural grassland ecosystems with different productivities over varying soil depths

International Nuclear Information System (INIS)

Breulmann, Marc; Boettger, Tatjana; Buscot, François; Gruendling, Ralf; Schulz, Elke

2016-01-01

Researchers have increasingly recognised a profound need for more information on SOC stocks in the soil and the factors governing their stability and dynamics. Many questions still remain unanswered about the interplay between changes in plant communities and the extent to which changes in aboveground productivity affect the carbon dynamics in soils through changes in its quantity and quality. Therefore, the main aim of this research was to examine the SOC accumulation potential of semi-natural grasslands of different productivities and determine the distribution of SOM fractions over varying soil depth intervals (0–10, 10–20, 20–30 30–50 50–80 and 80 + cm). SOM fractionation was considered as a relative measure of stability to separate SOM associated with clay minerals from SOM of specific light densities less than 2 g cm"−"3 (size-density fractionation). Two clay-associated fractions (CF1, < 1 μm; and CF2, 1–2 μm) and two light fractions (LF1, < 1.8 g cm"−"3; and LF2, 1.8–2.0 g cm"−"3) were separated. The stability of these fractions was characterised by their carbon hot water extractability (C_H_W_E) and stable carbon isotope composition. In the semi-natural grasslands studied, most OC was stored in the top 30 cm, where turnover is rapid. Effects of low productivity grasslands became only significantly apparent when fractional OC contributions of total SOM was considered (CF1 and LF1). In deeper soil depths OC was largely attributed to the CF1 fraction of low productivity grasslands. We suggest that the majority of OM in deeper soil depth intervals is microbially-derived, as evidenced by decreasing C/N ratios and decreasing δ"1"3C values. The hot water extraction and natural δ"1"3C abundance, employed here allowed the characterisation of SOM stabilisation properties, however how climatic changes affect the fate of OM within different soil depth intervals is still unknown. - Highlights: • OC stocks over varying soil depths in extensively

Carbon storage potential in size–density fractions from semi-natural grassland ecosystems with different productivities over varying soil depths

Energy Technology Data Exchange (ETDEWEB)

Breulmann, Marc [Helmholtz-Centre for Environmental Research – UFZ, Department of Soil Ecology, Theodor-Lieser-Str. 4, 06120 Halle (Germany); Helmholtz-Centre for Environmental Research – UFZ, Environmental and Biotechnology Centre (UBZ), Permoserstraße 15, 04318 Leipzig (Germany); Boettger, Tatjana [Helmholtz-Centre for Environmental Research – UFZ, Department of Isotope Hydrology, Theodor-Lieser-Str. 4, D-06120 Halle (Germany); Buscot, François [Helmholtz-Centre for Environmental Research – UFZ, Department of Soil Ecology, Theodor-Lieser-Str. 4, 06120 Halle (Germany); German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103 Leipzig (Germany); Gruendling, Ralf [Helmholtz-Centre for Environmental Research – UFZ, Department, Department of Soil Physics, Theodor-Lieser-Str. 4, D-06120 Halle (Germany); Schulz, Elke [Helmholtz-Centre for Environmental Research – UFZ, Department of Soil Ecology, Theodor-Lieser-Str. 4, 06120 Halle (Germany)

2016-03-01

Researchers have increasingly recognised a profound need for more information on SOC stocks in the soil and the factors governing their stability and dynamics. Many questions still remain unanswered about the interplay between changes in plant communities and the extent to which changes in aboveground productivity affect the carbon dynamics in soils through changes in its quantity and quality. Therefore, the main aim of this research was to examine the SOC accumulation potential of semi-natural grasslands of different productivities and determine the distribution of SOM fractions over varying soil depth intervals (0–10, 10–20, 20–30 30–50 50–80 and 80 + cm). SOM fractionation was considered as a relative measure of stability to separate SOM associated with clay minerals from SOM of specific light densities less than 2 g cm{sup −3} (size-density fractionation). Two clay-associated fractions (CF1, < 1 μm; and CF2, 1–2 μm) and two light fractions (LF1, < 1.8 g cm{sup −3}; and LF2, 1.8–2.0 g cm{sup −3}) were separated. The stability of these fractions was characterised by their carbon hot water extractability (C{sub HWE}) and stable carbon isotope composition. In the semi-natural grasslands studied, most OC was stored in the top 30 cm, where turnover is rapid. Effects of low productivity grasslands became only significantly apparent when fractional OC contributions of total SOM was considered (CF1 and LF1). In deeper soil depths OC was largely attributed to the CF1 fraction of low productivity grasslands. We suggest that the majority of OM in deeper soil depth intervals is microbially-derived, as evidenced by decreasing C/N ratios and decreasing δ{sup 13}C values. The hot water extraction and natural δ{sup 13}C abundance, employed here allowed the characterisation of SOM stabilisation properties, however how climatic changes affect the fate of OM within different soil depth intervals is still unknown. - Highlights: • OC stocks over varying

Locality of correlation in density functional theory

Energy Technology Data Exchange (ETDEWEB)

Burke, Kieron [Department of Chemistry, University of California, Irvine, California 92697 (United States); Cancio, Antonio [Department of Physics and Astronomy, Ball State University, Muncie, Indiana 47306 (United States); Gould, Tim [Qld Micro- and Nanotechnology Centre, Griffith University, Nathan, Qld 4111 (Australia); Pittalis, Stefano [CNR-Istituto di Nanoscienze, Via Campi 213A, I-41125 Modena (Italy)

2016-08-07

The Hohenberg-Kohn density functional was long ago shown to reduce to the Thomas-Fermi (TF) approximation in the non-relativistic semiclassical (or large-Z) limit for all matter, i.e., the kinetic energy becomes local. Exchange also becomes local in this limit. Numerical data on the correlation energy of atoms support the conjecture that this is also true for correlation, but much less relevant to atoms. We illustrate how expansions around a large particle number are equivalent to local density approximations and their strong relevance to density functional approximations. Analyzing highly accurate atomic correlation energies, we show that E{sub C} → −A{sub C} ZlnZ + B{sub C}Z as Z → ∞, where Z is the atomic number, A{sub C} is known, and we estimate B{sub C} to be about 37 mhartree. The local density approximation yields A{sub C} exactly, but a very incorrect value for B{sub C}, showing that the local approximation is less relevant for the correlation alone. This limit is a benchmark for the non-empirical construction of density functional approximations. We conjecture that, beyond atoms, the leading correction to the local density approximation in the large-Z limit generally takes this form, but with B{sub C} a functional of the TF density for the system. The implications for the construction of approximate density functionals are discussed.

The C{sub n} method for approximation of the Boltzmann equation; La methode C{sub n} d'approximation de l'equation de Boltzmann

Energy Technology Data Exchange (ETDEWEB)

Benoist, P; Kavenoky, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1968-01-15

In a new method of approximation of the Boltzmann equation, one starts from a particular form of the equation which involves only the angular flux at the boundary of the considered medium and where the space variable does not appear explicitly. Expanding in orthogonal polynomials the angular flux of neutrons leaking from the medium and making no assumption about the angular flux within the medium, very good approximations to several classical plane geometry problems, i.e. the albedo of slabs and the transmission by slabs, the extrapolation length of the Milne problem, the spectrum of neutrons reflected by a semi-infinite slowing down medium. The method can be extended to other geometries. (authors) [French] On etablit une nouvelle methode d'approximation pour l'equation de Boltzmann en partant d'une forme particuliere de cette equation qui n'implique que le flux angulaire a la frontiere du milieu et ou les variables d'espace n'apparaissent pas explicitement. Par un developpement en polynomes orthogonaux du flux angulaire sortant du milieu et sans faire d'hypothese sur le flux angulaire a l'interieur du milieu, on obtient de tres bonnes approximations pour plusieurs problemes classiques en geometrie plane: l'albedo et le facteur de transmission des plaques, la longueur d'extrapolation du probleme de Milne, le spectre des neutrons reflechis par un milieu semi-infini ralentisseur. La methode se generalise a d'autres geometries. (auteurs)

Semi-supervised sparse coding

KAUST Repository

Wang, Jim Jing-Yan; Gao, Xin

2014-01-01

Sparse coding approximates the data sample as a sparse linear combination of some basic codewords and uses the sparse codes as new presentations. In this paper, we investigate learning discriminative sparse codes by sparse coding in a semi-supervised manner, where only a few training samples are labeled. By using the manifold structure spanned by the data set of both labeled and unlabeled samples and the constraints provided by the labels of the labeled samples, we learn the variable class labels for all the samples. Furthermore, to improve the discriminative ability of the learned sparse codes, we assume that the class labels could be predicted from the sparse codes directly using a linear classifier. By solving the codebook, sparse codes, class labels and classifier parameters simultaneously in a unified objective function, we develop a semi-supervised sparse coding algorithm. Experiments on two real-world pattern recognition problems demonstrate the advantage of the proposed methods over supervised sparse coding methods on partially labeled data sets.

Semi-supervised sparse coding

KAUST Repository

Wang, Jim Jing-Yan

2014-07-06

Sparse coding approximates the data sample as a sparse linear combination of some basic codewords and uses the sparse codes as new presentations. In this paper, we investigate learning discriminative sparse codes by sparse coding in a semi-supervised manner, where only a few training samples are labeled. By using the manifold structure spanned by the data set of both labeled and unlabeled samples and the constraints provided by the labels of the labeled samples, we learn the variable class labels for all the samples. Furthermore, to improve the discriminative ability of the learned sparse codes, we assume that the class labels could be predicted from the sparse codes directly using a linear classifier. By solving the codebook, sparse codes, class labels and classifier parameters simultaneously in a unified objective function, we develop a semi-supervised sparse coding algorithm. Experiments on two real-world pattern recognition problems demonstrate the advantage of the proposed methods over supervised sparse coding methods on partially labeled data sets.

Newtonian and post-Newtonian approximations are asymptotic to general relativity

International Nuclear Information System (INIS)

Futamase, T.; Schutz, B.F.

1983-01-01

A precise definition of the Newtonian and post-Newtonian hierarchy of approximations to general relativity is given by studying a C/sup infinity/ sequence of solutions to Einstein's equations that is defined by initial data having the Newtonian scaling property: v/sup i/approx.epsilon, rhoapprox.epsilon 2 , papprox.epsilon 4 , where epsilon is the parameter along the sequence. We map one solution in the sequence to another by identifying them at constant spatial position x/sup i/ and Newtonian dynamical time tau = epsilont. This mapping defines a congruence parametrized by epsilon, and the various post-Newtonian approximations emerge as derivatives of the relativistic solutions along this congruence. We thereby show for the first time that the approximations are genuine asymptotic approximations to general relativity. The proof is given in detail up to first post-Newtonian order, but is easily extended. The results will be applied in the following paper to radiation reaction in binary star systems, to give a proof of the validity of the ''quadrupole formula'' free from any divergences

Parametric and non-parametric approach for sensory RATA (Rate-All-That-Apply) method of ledre profile attributes

Science.gov (United States)

Hastuti, S.; Harijono; Murtini, E. S.; Fibrianto, K.

2018-03-01

This current study is aimed to investigate the use of parametric and non-parametric approach for sensory RATA (Rate-All-That-Apply) method. Ledre as Bojonegoro unique local food product was used as point of interest, in which 319 panelists were involved in the study. The result showed that ledre is characterized as easy-crushed texture, sticky in mouth, stingy sensation and easy to swallow. It has also strong banana flavour with brown in colour. Compared to eggroll and semprong, ledre has more variances in terms of taste as well the roll length. As RATA questionnaire is designed to collect categorical data, non-parametric approach is the common statistical procedure. However, similar results were also obtained as parametric approach, regardless the fact of non-normal distributed data. Thus, it suggests that parametric approach can be applicable for consumer study with large number of respondents, even though it may not satisfy the assumption of ANOVA (Analysis of Variances).

Supercritical extraction of oleaginous: parametric sensitivity analysis

Directory of Open Access Journals (Sweden)

Santos M.M.

2000-01-01

Full Text Available The economy has become universal and competitive, thus the industries of vegetable oil extraction must advance in the sense of minimising production costs and, at the same time, generating products that obey more rigorous patterns of quality, including solutions that do not damage the environment. The conventional oilseed processing uses hexane as solvent. However, this solvent is toxic and highly flammable. Thus the search of substitutes for hexane in oleaginous extraction process has increased in the last years. The supercritical carbon dioxide is a potential substitute for hexane, but it is necessary more detailed studies to understand the phenomena taking place in such process. Thus, in this work a diffusive model for semi-continuous (batch for the solids and continuous for the solvent isothermal and isobaric extraction process using supercritical carbon dioxide is presented and submitted to a parametric sensitivity analysis by means of a factorial design in two levels. The model parameters were disturbed and their main effects analysed, so that it is possible to propose strategies for high performance operation.

Functional approximations to posterior densities: a neural network approach to efficient sampling

NARCIS (Netherlands)

L.F. Hoogerheide (Lennart); J.F. Kaashoek (Johan); H.K. van Dijk (Herman)

2002-01-01

textabstractThe performance of Monte Carlo integration methods like importance sampling or Markov Chain Monte Carlo procedures greatly depends on the choice of the importance or candidate density. Usually, such a density has to be "close" to the target density in order to yield numerically accurate

Experimental Sentinel-2 LAI estimation using parametric, non-parametric and physical retrieval methods - A comparison

NARCIS (Netherlands)

Verrelst, Jochem; Rivera, Juan Pablo; Veroustraete, Frank; Muñoz-Marí, Jordi; Clevers, J.G.P.W.; Camps-Valls, Gustau; Moreno, José

2015-01-01

Given the forthcoming availability of Sentinel-2 (S2) images, this paper provides a systematic comparison of retrieval accuracy and processing speed of a multitude of parametric, non-parametric and physically-based retrieval methods using simulated S2 data. An experimental field dataset (SPARC),

Unified triminimal parametrizations of quark and lepton mixing matrices

International Nuclear Information System (INIS)

He Xiaogang; Li Shiwen; Ma Boqiang

2009-01-01

We present a detailed study on triminimal parametrizations of quark and lepton mixing matrices with different basis matrices. We start with a general discussion on the triminimal expansion of the mixing matrix and on possible unified quark and lepton parametrization using quark-lepton complementarity. We then consider several interesting basis matrices and compare the triminimal parametrizations with the Wolfenstein-like parametrizations. The usual Wolfenstein parametrization for quark mixing is a triminimal expansion around the unit matrix as the basis. The corresponding quark-lepton complementarity lepton mixing matrix is a triminimal expansion around the bimaximal basis. Current neutrino oscillation data show that the lepton mixing matrix is very well represented by the tribimaximal mixing. It is natural to take it as an expanding basis. The corresponding zeroth order basis for quark mixing in this case makes the triminimal expansion converge much faster than the usual Wolfenstein parametrization. The triminimal expansion based on tribimaximal mixing can be converted to the Wolfenstein-like parametrizations discussed in the literature. We thus have a unified description between different kinds of parametrizations for quark and lepton sectors: the standard parametrizations, the Wolfenstein-like parametrizations, and the triminimal parametrizations.

Excitonic effects in solids : time-dependent density functional theory versus the Bethe-Salpeter equation

International Nuclear Information System (INIS)

Sagmeister, S.

2009-01-01

The aim of this work is to compare two state-of-the-art methods for the investigation of excitonic effects in solids, namely Time-Dependent Density Functional Theory (TDDFT) and Many-Body Perturbation Theory (MBPT), for selected simple gap systems as well as semiconducting polymers. Within TDDFT, the linear response framework is used and the Dyson equation for the density-density response function is solved, whereas within MBPT, the Bethe-Salpeter equation (BSE) for the electron-hole correlation function is solved. The dielectric function is obtained as a last step. Both techniques take into account the excitonic effects caused by the interaction of electron-hole pairs. In the former these effects are included in the exchange-correlation (xc) kernel, whereas in the latter they are located in the interaction kernel of the BSE. Kohn-Sham single-particle wave functions obtained from Density Functional Theory within the linearized augmented planewave (LAPW) method are used to calculate all relevant quantities of the formalism. For the simple systems GaAs, Si and LiF are chosen. The role of several approximations to the xc kernel is studied and it is found that for GaAs and Si simple semi-empirical models provide a dielectric function in accordance with the BSE. For the case of LiF, being a system with a weak screening and a strongly bound exciton, only an xc kernel derived from MBPT yields reasonable results but still a slight discrepancy to the BSE is observed. Finally, the semiconducting polymers poly-acetylene and poly(phenylene-vinylene) (PPV) are studied. For both materials the concept of semi-empirical approximations to the xc kernel turns out to be ambiguous due to their low-dimensional character. In the case of poly-acetylene, the xc kernel derived from MBPT yields a dielectric function which is in close but not exact agreement with the one obtained from the BSE. (author) [de

Semi-classical limit of relativistic quantum mechanics

Indian Academy of Sciences (India)

It is shown that the semi-classical limit of solutions to the Klein–Gordon equation gives the particle probability density that is in direct proportion to the inverse of the particle velocity. It is also shown that in the case of the Dirac equation a different result is obtained.

Forced and free convection flow with viscous dissipation effects: The method of parametric differentiation

International Nuclear Information System (INIS)

Hossain, M.A.; Arbad, O.

1988-07-01

Effect of buoyancy force in a laminar uniform forced convection flow past a semi-infinite vertical plate has been analyzed near the leading edge, taking into account the viscous dissipation. The coupled non-linear locally similar equations, which govern the flow, are solved by the method of parametric differentiation. Effects of the buoyancy force and the heat due to viscous dissipation on the flow and the temperature fields as well as on the wall shear-stress and the heat transfer at the surface of the plate are shown graphically for the values of the Prandtl number σ ranging from 10 -1 to 1.0. (author). 20 refs, 3 figs, 2 tabs

Parametric model of the scala tympani for haptic-rendered cochlear implantation.

Science.gov (United States)

Todd, Catherine; Naghdy, Fazel

2005-01-01

A parametric model of the human scala tympani has been designed for use in a haptic-rendered computer simulation of cochlear implant surgery. It will be the first surgical simulator of this kind. A geometric model of the Scala Tympani has been derived from measured data for this purpose. The model is compared with two existing descriptions of the cochlear spiral. A first approximation of the basilar membrane is also produced. The structures are imported into a force-rendering software application for system development.

Beyond the random phase approximation

DEFF Research Database (Denmark)

Olsen, Thomas; Thygesen, Kristian S.

2013-01-01

We assess the performance of a recently proposed renormalized adiabatic local density approximation (rALDA) for ab initio calculations of electronic correlation energies in solids and molecules. The method is an extension of the random phase approximation (RPA) derived from time-dependent density...... functional theory and the adiabatic connection fluctuation-dissipation theorem and contains no fitted parameters. The new kernel is shown to preserve the accurate description of dispersive interactions from RPA while significantly improving the description of short-range correlation in molecules, insulators......, and metals. For molecular atomization energies, the rALDA is a factor of 7 better than RPA and a factor of 4 better than the Perdew-Burke-Ernzerhof (PBE) functional when compared to experiments, and a factor of 3 (1.5) better than RPA (PBE) for cohesive energies of solids. For transition metals...

Parametric instabilities in large plasmas

International Nuclear Information System (INIS)

Brambilla, Marco; Liberman, Bernardo.

1979-01-01

Parametric decay processes in large plasmas are considered as the linear stage of a three wave interaction (pump, sideband and beat wave) in which the amplitude of the externally excited pump is sufficiently large to neglect pump depletion to first order, yet sufficiently small to allow a linearized treatment of the pump propagation to zeroth order. The coupling coefficients are then obtained from an iterative solution of Vlasov equation, and a compact expression is derived, in which the multiple series over Bessel functions is explicitly summed. Even in the limit of a very long wavelength pump, the dispersion relation obtained in this way does not coincide with the one obtained using the well-known ''dipole'' approximation, unless both the sideband and beat wave are resonant modes of the plasma. An analysis of the origin of this discrepancy allows us to conclude that ''quasimodes'' (evanescent waves driven absolutely unstable by the pump) are more correctly described by the iterative approach

Nonlinear electronic excitations in crystalline solids using meta-generalized gradient approximation and hybrid functional in time-dependent density functional theory

Energy Technology Data Exchange (ETDEWEB)

Sato, Shunsuke A. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan); Taniguchi, Yasutaka [Center for Computational Science, University of Tsukuba, Tsukuba 305-8571 (Japan); Department of Medical and General Sciences, Nihon Institute of Medical Science, 1276 Shimogawara, Moroyama-Machi, Iruma-Gun, Saitama 350-0435 (Japan); Shinohara, Yasushi [Max Planck Institute of Microstructure Physics, 06120 Halle (Germany); Yabana, Kazuhiro [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan); Center for Computational Science, University of Tsukuba, Tsukuba 305-8571 (Japan)

2015-12-14

We develop methods to calculate electron dynamics in crystalline solids in real-time time-dependent density functional theory employing exchange-correlation potentials which reproduce band gap energies of dielectrics; a meta-generalized gradient approximation was proposed by Tran and Blaha [Phys. Rev. Lett. 102, 226401 (2009)] (TBm-BJ) and a hybrid functional was proposed by Heyd, Scuseria, and Ernzerhof [J. Chem. Phys. 118, 8207 (2003)] (HSE). In time evolution calculations employing the TB-mBJ potential, we have found it necessary to adopt the predictor-corrector step for a stable time evolution. We have developed a method to evaluate electronic excitation energy without referring to the energy functional which is unknown for the TB-mBJ potential. For the HSE functional, we have developed a method for the operation of the Fock-like term in Fourier space to facilitate efficient use of massive parallel computers equipped with graphic processing units. We compare electronic excitations in silicon and germanium induced by femtosecond laser pulses using the TB-mBJ, HSE, and a simple local density approximation (LDA). At low laser intensities, electronic excitations are found to be sensitive to the band gap energy: they are close to each other using TB-mBJ and HSE and are much smaller in LDA. At high laser intensities close to the damage threshold, electronic excitation energies do not differ much among the three cases.

Towards improved local hybrid functionals by calibration of exchange-energy densities

International Nuclear Information System (INIS)

Arbuznikov, Alexei V.; Kaupp, Martin

2014-01-01

A new approach for the calibration of (semi-)local and exact exchange-energy densities in the context of local hybrid functionals is reported. The calibration functions are derived from only the electron density and its spatial derivatives, avoiding spatial derivatives of the exact-exchange energy density or other computationally unfavorable contributions. The calibration functions fulfill the seven more important out of nine known exact constraints. It is shown that calibration improves substantially the definition of a non-dynamical correlation energy term for generalized gradient approximation (GGA)-based local hybrids. Moreover, gauge artifacts in the potential-energy curves of noble-gas dimers may be corrected by calibration. The developed calibration functions are then evaluated for a large range of energy-related properties (atomization energies, reaction barriers, ionization potentials, electron affinities, and total atomic energies) of three sets of local hybrids, using a simple one-parameter local-mixing. The functionals are based on (a) local spin-density approximation (LSDA) or (b) Perdew-Burke-Ernzerhof (PBE) exchange and correlation, and on (c) Becke-88 (B88) exchange and Lee-Yang-Parr (LYP) correlation. While the uncalibrated GGA-based functionals usually provide very poor thermochemical data, calibration allows a dramatic improvement, accompanied by only a small deterioration of reaction barriers. In particular, an optimized BLYP-based local-hybrid functional has been found that is a substantial improvement over the underlying global hybrids, as well as over previously reported LSDA-based local hybrids. It is expected that the present calibration approach will pave the way towards new generations of more accurate hyper-GGA functionals based on a local mixing of exchange-energy densities

Approximate analysis of rigid plate loading on elastic multi-layered systems

CSIR Research Space (South Africa)

Maina, JW

2008-07-01

Full Text Available , this distribution was approximated using uniformly distributed multiple loads and analysis performed using Games. Results have shown good agreement with the theory for the case of a semi-infinite medium. Furthermore, extension of this method to multilayered system...

Is there a limit to agglomeration? Evidence from productivity of Dutch firms

NARCIS (Netherlands)

Rizov, M.; Oskam, A.J.; Walsh, P.

2012-01-01

We compute aggregate productivity of three categories of regions, classified by the level of urbanization and density of economic activity in the Netherlands, from firm-specific total factor productivity (TFP) measures. TFP measures are estimated by a semi-parametric algorithm, within 2-digit

Diversity comparison of Pareto front approximations in many-objective optimization.

Science.gov (United States)

Li, Miqing; Yang, Shengxiang; Liu, Xiaohui

2014-12-01

Diversity assessment of Pareto front approximations is an important issue in the stochastic multiobjective optimization community. Most of the diversity indicators in the literature were designed to work for any number of objectives of Pareto front approximations in principle, but in practice many of these indicators are infeasible or not workable when the number of objectives is large. In this paper, we propose a diversity comparison indicator (DCI) to assess the diversity of Pareto front approximations in many-objective optimization. DCI evaluates relative quality of different Pareto front approximations rather than provides an absolute measure of distribution for a single approximation. In DCI, all the concerned approximations are put into a grid environment so that there are some hyperboxes containing one or more solutions. The proposed indicator only considers the contribution of different approximations to nonempty hyperboxes. Therefore, the computational cost does not increase exponentially with the number of objectives. In fact, the implementation of DCI is of quadratic time complexity, which is fully independent of the number of divisions used in grid. Systematic experiments are conducted using three groups of artificial Pareto front approximations and seven groups of real Pareto front approximations with different numbers of objectives to verify the effectiveness of DCI. Moreover, a comparison with two diversity indicators used widely in many-objective optimization is made analytically and empirically. Finally, a parametric investigation reveals interesting insights of the division number in grid and also offers some suggested settings to the users with different preferences.

Explicit/multi-parametric model predictive control (MPC) of linear discrete-time systems by dynamic and multi-parametric programming

KAUST Repository

Kouramas, K.I.

2011-08-01

This work presents a new algorithm for solving the explicit/multi- parametric model predictive control (or mp-MPC) problem for linear, time-invariant discrete-time systems, based on dynamic programming and multi-parametric programming techniques. The algorithm features two key steps: (i) a dynamic programming step, in which the mp-MPC problem is decomposed into a set of smaller subproblems in which only the current control, state variables, and constraints are considered, and (ii) a multi-parametric programming step, in which each subproblem is solved as a convex multi-parametric programming problem, to derive the control variables as an explicit function of the states. The key feature of the proposed method is that it overcomes potential limitations of previous methods for solving multi-parametric programming problems with dynamic programming, such as the need for global optimization for each subproblem of the dynamic programming step. © 2011 Elsevier Ltd. All rights reserved.

A domian Decomposition Method for Transient Neutron Transport with Pomrning-Eddington Approximation

International Nuclear Information System (INIS)

Hendi, A.A.; Abulwafa, E.E.

2008-01-01

The time-dependent neutron transport problem is approximated using the Pomraning-Eddington approximation. This approximation is two-flux approximation that expands the angular intensity in terms of the energy density and the net flux. This approximation converts the integro-differential Boltzmann equation into two first order differential equations. The A domian decomposition method that used to solve the linear or nonlinear differential equations is used to solve the resultant two differential equations to find the neutron energy density and net flux, which can be used to calculate the neutron angular intensity through the Pomraning-Eddington approximation

Combinations of coupled cluster, density functionals, and the random phase approximation for describing static and dynamic correlation, and van der Waals interactions

Science.gov (United States)

Garza, Alejandro J.; Bulik, Ireneusz W.; Alencar, Ana G. Sousa; Sun, Jianwei; Perdew, John P.; Scuseria, Gustavo E.

2016-04-01

Contrary to standard coupled cluster doubles (CCD) and Brueckner doubles (BD), singlet-paired analogues of CCD and BD (denoted here as CCD0 and BD0) do not break down when static correlation is present, but neglect substantial amounts of dynamic correlation. In fact, CCD0 and BD0 do not account for any contributions from multielectron excitations involving only same-spin electrons at all. We exploit this feature to add - without introducing double counting, self-interaction, or increase in cost - the missing correlation to these methods via meta-GGA (generalised gradient approximation) density functionals (Tao-Perdew-Staroverov-Scuseria and strongly constrained and appropriately normed). Furthermore, we improve upon these CCD0+DFT blends by invoking range separation: the short- and long-range correlations absent in CCD0/BD0 are evaluated with density functional theory and the direct random phase approximation, respectively. This corrects the description of long-range van der Waals forces. Comprehensive benchmarking shows that the combinations presented here are very accurate for weakly correlated systems, while also providing a reasonable description of strongly correlated problems without resorting to symmetry breaking.

High energy-density liquid rocket fuel performance

Science.gov (United States)

Rapp, Douglas C.

1990-01-01

A fuel performance database of liquid hydrocarbons and aluminum-hydrocarbon fuels was compiled using engine parametrics from the Space Transportation Engine Program as a baseline. Propellant performance parameters are introduced. General hydrocarbon fuel performance trends are discussed with respect to hydrogen-to-carbon ratio and heat of formation. Aluminum-hydrocarbon fuel performance is discussed with respect to aluminum metal loading. Hydrocarbon and aluminum-hydrocarbon fuel performance is presented with respect to fuel density, specific impulse and propellant density specific impulse.

Description of plasmon-like band in silver clusters: the importance of the long-range Hartree-Fock exchange in time-dependent density-functional theory simulations.

Science.gov (United States)

Rabilloud, Franck

2014-10-14

Absorption spectra of Ag20 and Ag55(q) (q = +1, -3) nanoclusters are investigated in the framework of the time-dependent density functional theory in order to analyse the role of the d electrons in plasmon-like band of silver clusters. The description of the plasmon-like band from calculations using density functionals containing an amount of Hartree-Fock exchange at long range, namely, hybrid and range-separated hybrid (RSH) density functionals, is in good agreement with the classical interpretation of the plasmon-like structure as a collective excitation of valence s-electrons. In contrast, using local or semi-local exchange functionals (generalized gradient approximations (GGAs) or meta-GGAs) leads to a strong overestimation of the role of d electrons in the plasmon-like band. The semi-local asymptotically corrected model potentials also describe the plasmon as mainly associated to d electrons, though calculated spectra are in fairly good agreement with those calculated using the RSH scheme. Our analysis shows that a portion of non-local exchange modifies the description of the plasmon-like band.

Improving Rydberg Excitations within Time-Dependent Density Functional Theory with Generalized Gradient Approximations: The Exchange-Enhancement-for-Large-Gradient Scheme.

Science.gov (United States)

Li, Shaohong L; Truhlar, Donald G

2015-07-14

Time-dependent density functional theory (TDDFT) with conventional local and hybrid functionals such as the local and hybrid generalized gradient approximations (GGA) seriously underestimates the excitation energies of Rydberg states, which limits its usefulness for applications such as spectroscopy and photochemistry. We present here a scheme that modifies the exchange-enhancement factor to improve GGA functionals for Rydberg excitations within the TDDFT framework while retaining their accuracy for valence excitations and for the thermochemical energetics calculated by ground-state density functional theory. The scheme is applied to a popular hybrid GGA functional and tested on data sets of valence and Rydberg excitations and atomization energies, and the results are encouraging. The scheme is simple and flexible. It can be used to correct existing functionals, and it can also be used as a strategy for the development of new functionals.

Pade approximants for the ground-state energy of closed-shell quantum dots

International Nuclear Information System (INIS)

Gonzalez, A.; Partoens, B.; Peeters, F.M.

1997-08-01

Analytic approximations to the ground-state energy of closed-shell quantum dots (number of electrons from 2 to 210) are presented in the form of two-point Pade approximants. These Pade approximants are constructed from the small- and large-density limits of the energy. We estimated that the maximum error, reached for intermediate densities, is less than ≤ 3%. Within that present approximation the ground-state is found to be unpolarized. (author). 21 refs, 3 figs, 2 tabs

Atmospheric density determination using high-accuracy satellite GPS data

Science.gov (United States)

Tingling, R.; Miao, J.; Liu, S.

2017-12-01

Atmospheric drag is the main error source in the orbit determination and prediction of low Earth orbit (LEO) satellites, however, empirical models which are used to account for atmosphere often exhibit density errors around 15 30%. Atmospheric density determination thus become an important topic for atmospheric researchers. Based on the relation between atmospheric drag force and the decay of orbit semi-major axis, we derived atmospheric density along the trajectory of CHAMP with its Rapid Science Orbit (RSO) data. Three primary parameters are calculated, including the ratio of cross sectional area to mass, drag coefficient, and the decay of semi-major axis caused by atmospheric drag. We also analyzed the source of error and made a comparison between GPS-derived and reference density. Result on 2 Dec 2008 shows that the mean error of GPS-derived density can decrease from 29.21% to 9.20% when time span adopted on the process of computation increase from 10min to 50min. Result for the whole December indicates that when the time span meet the condition that the amplitude of the decay of semi-major axis is much greater than its standard deviation, then density precision of 10% can be achieved.

Approximations to the Probability of Failure in Random Vibration by Integral Equation Methods

DEFF Research Database (Denmark)

Nielsen, Søren R.K.; Sørensen, John Dalsgaard

Close approximations to the first passage probability of failure in random vibration can be obtained by integral equation methods. A simple relation exists between the first passage probability density function and the distribution function for the time interval spent below a barrier before...... passage probability density. The results of the theory agree well with simulation results for narrow banded processes dominated by a single frequency, as well as for bimodal processes with 2 dominating frequencies in the structural response....... outcrossing. An integral equation for the probability density function of the time interval is formulated, and adequate approximations for the kernel are suggested. The kernel approximation results in approximate solutions for the probability density function of the time interval, and hence for the first...

Study of internal rotation in molecules using molecular orbital method in the CNDO/BW approximation

International Nuclear Information System (INIS)

Pedrosa, M.S.

1987-10-01

It is presented a LCAO-MO-SCF study of Internal Rotation for the molecules C 2 H 6 , CH 3 NH 2 , H 2 O 2 , and N 2 H 4 by ysing the CNDO/BW approximation and an M-center energy partition. Our results are compared with those obtained with the CNDO/2 approximation. It is shown that there are differences in the analysis of the process involved in the internal rotation barriers mechanism. Thus the interpretation of the results is strongly dependent on the parametrization used. (author) [pt

Excited state nuclear forces from the Tamm-Dancoff approximation to time-dependent density functional theory within the plane wave basis set framework

Science.gov (United States)

Hutter, Jürg

2003-03-01

An efficient formulation of time-dependent linear response density functional theory for the use within the plane wave basis set framework is presented. The method avoids the transformation of the Kohn-Sham matrix into the canonical basis and references virtual orbitals only through a projection operator. Using a Lagrangian formulation nuclear derivatives of excited state energies within the Tamm-Dancoff approximation are derived. The algorithms were implemented into a pseudo potential/plane wave code and applied to the calculation of adiabatic excitation energies, optimized geometries and vibrational frequencies of three low lying states of formaldehyde. An overall good agreement with other time-dependent density functional calculations, multireference configuration interaction calculations and experimental data was found.

PRODUCTION OF HIGH DENSITY PARTICLEBOARD USING MELAMINE-UREA-FORMALDEHYDE RESIN

Directory of Open Access Journals (Sweden)

Setsuo Iwakiri

2005-12-01

Full Text Available This research was developed aiming to evaluate the effects of board density and melamine-urea-formaldehyde resin onthe properties of particleboard for semi-structural applications. The boards were manufactured with nominal density of 0.65 g/cm³and 0.90 g/cm³ using urea-formaldehyde resin as control and melamine-urea-formaldehyde. The results showed a better dimensionallystability and mechanical properties of the boards manufactured with higher density and MUF resin content. The fine furnish usedfor external layer of particleboard in the industrial process, could be used for high density homogeneous board to semi-strucuturaluses, such as flooring applications.

Pade approximants in field theory: pion and kaon systems; Approximants de pade en theorie des champs: systeme de pions et de kaons

Energy Technology Data Exchange (ETDEWEB)

Zinn-Justin, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1969-07-01

We construct the Pade approximants of the S-matrix, starting from the perturbation series, in the case of two body pion and kaon systems. We have three parameters. The seven lowest lying two body resonances ({rho}, K{sup *}(890), {phi}, K{sup *}(1420), f{sub 0}, f', A{sub 2}) are obtained within a few per cent of their actual masses. The Regge trajectories are rising, the intercepts of the {rho} and f{sub 0} agree well with the experimental values. In the appendices we give some properties and applications of the Pade approximants. (author) [French] Nous avons construit les approximants de Pade de la matrice S a partir de la serie formelle des perturbations, dans le cas des systemes a deux corps de pions et de kaons. Le probleme depend de trois parametres. Nous avons obtenu les sept resonances meson-meson a deux corps ({rho}, K{sup *}(890), {phi}, K{sup *}(1420), f{sub 0}, f', A{sub 2}) a quelques pour cent de leurs masses experimentales. Les trajectoires de Regge sont trouvees croissantes, les intercepts du {rho} et du f{sub 0} sont en bon accord avec l'experience. Dans les appendices nous donnons quelques proprietes et applications des approximants de Pade. (auteur)

Pade approximants in field theory: pion and kaon systems; Approximants de pade en theorie des champs: systeme de pions et de kaons

Energy Technology Data Exchange (ETDEWEB)

Zinn-Justin, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1969-07-01

We construct the Pade approximants of the S-matrix, starting from the perturbation series, in the case of two body pion and kaon systems. We have three parameters. The seven lowest lying two body resonances ({rho}, K{sup *}(890), {phi}, K{sup *}(1420), f{sub 0}, f', A{sub 2}) are obtained within a few per cent of their actual masses. The Regge trajectories are rising, the intercepts of the {rho} and f{sub 0} agree well with the experimental values. In the appendices we give some properties and applications of the Pade approximants. (author) [French] Nous avons construit les approximants de Pade de la matrice S a partir de la serie formelle des perturbations, dans le cas des systemes a deux corps de pions et de kaons. Le probleme depend de trois parametres. Nous avons obtenu les sept resonances meson-meson a deux corps ({rho}, K{sup *}(890), {phi}, K{sup *}(1420), f{sub 0}, f', A{sub 2}) a quelques pour cent de leurs masses experimentales. Les trajectoires de Regge sont trouvees croissantes, les intercepts du {rho} et du f{sub 0} sont en bon accord avec l'experience. Dans les appendices nous donnons quelques proprietes et applications des approximants de Pade. (auteur)

Virtual prototyping of a semi-active transfemoral prosthetic leg.

Science.gov (United States)

Lui, Zhen Wei; Awad, Mohammed I; Abouhossein, Alireza; Dehghani-Sanij, Abbas A; Messenger, Neil

2015-05-01

This article presents a virtual prototyping study of a semi-active lower limb prosthesis to improve the functionality of an amputee during prosthesis-environment interaction for level ground walking. Articulated ankle-foot prosthesis and a single-axis semi-active prosthetic knee with active and passive operating modes were considered. Data for level ground walking were collected using a photogrammetric method in order to develop a base-line simulation model and with the hip kinematics input to verify the proposed design. The simulated results show that the semi-active lower limb prosthesis is able to move efficiently in passive mode, and the activation time of the knee actuator can be reduced by approximately 50%. Therefore, this semi-active system has the potential to reduce the energy consumption of the actuators required during level ground walking and requires less compensation from the amputee due to lower deviation of the vertical excursion of body centre of mass. © IMechE 2015.

Collision cross sections of N2 by H+ impact at keV energies within time-dependent density-functional theory

Science.gov (United States)

Yu, W.; Gao, C.-Z.; Zhang, Y.; Zhang, F. S.; Hutton, R.; Zou, Y.; Wei, B.

2018-03-01

We calculate electron capture and ionization cross sections of N2 impacted by the H+ projectile at keV energies. To this end, we employ the time-dependent density-functional theory coupled nonadiabatically to molecular dynamics. To avoid the explicit treatment of the complex density matrix in the calculation of cross sections, we propose an approximate method based on the assumption of constant ionization rate over the period of the projectile passing the absorbing boundary. Our results agree reasonably well with experimental data and semi-empirical results within the measurement uncertainties in the considered energy range. The discrepancies are mainly attributed to the inadequate description of exchange-correlation functional and the crude approximation for constant ionization rate. Although the present approach does not predict the experiments quantitatively for collision energies below 10 keV, it is still helpful to calculate total cross sections of ion-molecule collisions within a certain energy range.

Rate-dependent extensions of the parametric magneto-dynamic model with magnetic hysteresis

Directory of Open Access Journals (Sweden)

S. Steentjes

2017-05-01

Full Text Available This paper extends the parametric magneto-dynamic model of soft magnetic steel sheets to account for the phase shift between local magnetic flux density and magnetic field strength. This phase shift originates from the damped motion of domain walls and is strongly dependent on the microstructure of the material. In this regard, two different approaches to include the rate-dependent effects are investigated: a purely phenomenological, mathematical approach and a physical-based one.

Theoretical and algorithmic advances in multi-parametric programming and control

KAUST Repository

Pistikopoulos, Efstratios N.; Dominguez, Luis; Panos, Christos; Kouramas, Konstantinos; Chinchuluun, Altannar

2012-01-01

This paper presents an overview of recent theoretical and algorithmic advances, and applications in the areas of multi-parametric programming and explicit/multi-parametric model predictive control (mp-MPC). In multi-parametric programming, advances include areas such as nonlinear multi-parametric programming (mp-NLP), bi-level programming, dynamic programming and global optimization for multi-parametric mixed-integer linear programming problems (mp-MILPs). In multi-parametric/explicit MPC (mp-MPC), advances include areas such as robust multi-parametric control, multi-parametric nonlinear MPC (mp-NMPC) and model reduction in mp-MPC. A comprehensive framework for multi-parametric programming and control is also presented. Recent applications include a hydrogen storage device, a fuel cell power generation system, an unmanned autonomous vehicle (UAV) and a hybrid pressure swing adsorption (PSA) system. © 2012 Springer-Verlag.

Theoretical and algorithmic advances in multi-parametric programming and control

KAUST Repository

Pistikopoulos, Efstratios N.

2012-04-21

This paper presents an overview of recent theoretical and algorithmic advances, and applications in the areas of multi-parametric programming and explicit/multi-parametric model predictive control (mp-MPC). In multi-parametric programming, advances include areas such as nonlinear multi-parametric programming (mp-NLP), bi-level programming, dynamic programming and global optimization for multi-parametric mixed-integer linear programming problems (mp-MILPs). In multi-parametric/explicit MPC (mp-MPC), advances include areas such as robust multi-parametric control, multi-parametric nonlinear MPC (mp-NMPC) and model reduction in mp-MPC. A comprehensive framework for multi-parametric programming and control is also presented. Recent applications include a hydrogen storage device, a fuel cell power generation system, an unmanned autonomous vehicle (UAV) and a hybrid pressure swing adsorption (PSA) system. © 2012 Springer-Verlag.

Extraction of market expectations from risk-neutral density

Directory of Open Access Journals (Sweden)

Josip Arnerić

2015-12-01

Full Text Available The purpose of this paper is to investigate which of the proposed parametric models for extracting risk-neutral density; among Black-Scholes Merton, mixture of two log-normals and generalized beta; give the best fit. The model that fits sample data better is used to describe different characteristics (moments of the ex ante probability distribution. The empirical findings indicate that no matter which parametric model is used, the best fit is always obtained for short maturity horizon, but when comparing models in short-run, the mixture of two log-normals gives statistically significant smaller MSE. According to the pair-wise comparison results, the basic conclusion is that the mixture of two log-normals is superior to the other parametric models and has proven to be very flexible in capturing commonly observed characteristics of the underlying financial assets, such as asymmetries and “fat-tails” in implied probability distribution.

Electron Parametric Instabilities Driven by Relativistically Intense Laser Light in Plasma

Science.gov (United States)

Barr, H. C.; Mason, P.; Parr, D. M.

1999-08-01

A unified treatment of electron parametric instabilities driven by ultraintense laser light in plasma is described. It is valid for any intensity, polarization, plasma density, and scattering geometry. The method is applied to linearly polarized light in both underdense plasma and overdense plasma accessible by self-induced transparency. New options arise which are hybrids of stimulated Raman scattering, the two plasmon decay, the relativistic modulational and filamentation instabilities, and stimulated harmonic generation. There is vigorous growth over a wide range of wave numbers and harmonics.

Design and Parametric Study of the Magnetic Sensor for Position Detection in Linear Motor Based on Nonlinear Parametric model order reduction.

Science.gov (United States)

Paul, Sarbajit; Chang, Junghwan

2017-07-01

This paper presents a design approach for a magnetic sensor module to detect mover position using the proper orthogonal decomposition-dynamic mode decomposition (POD-DMD)-based nonlinear parametric model order reduction (PMOR). The parameterization of the sensor module is achieved by using the multipolar moment matching method. Several geometric variables of the sensor module are considered while developing the parametric study. The operation of the sensor module is based on the principle of the airgap flux density distribution detection by the Hall Effect IC. Therefore, the design objective is to achieve a peak flux density (PFD) greater than 0.1 T and total harmonic distortion (THD) less than 3%. To fulfill the constraint conditions, the specifications for the sensor module is achieved by using POD-DMD based reduced model. The POD-DMD based reduced model provides a platform to analyze the high number of design models very fast, with less computational burden. Finally, with the final specifications, the experimental prototype is designed and tested. Two different modes, 90° and 120° modes respectively are used to obtain the position information of the linear motor mover. The position information thus obtained are compared with that of the linear scale data, used as a reference signal. The position information obtained using the 120° mode has a standard deviation of 0.10 mm from the reference linear scale signal, whereas the 90° mode position signal shows a deviation of 0.23 mm from the reference. The deviation in the output arises due to the mechanical tolerances introduced into the specification during the manufacturing process. This provides a scope for coupling the reliability based design optimization in the design process as a future extension.

Transverse momentum in semi-inclusive deep inelastic scattering

International Nuclear Information System (INIS)

Ceccopieri, Federico Alberto; Trentadue, Luca

2006-01-01

Within the framework of perturbative quantum chromodynamics we derive the evolution equations for transverse momentum dependent distributions and apply them to the case of semi-inclusive deep inelastic scattering. The evolution equations encode the perturbative component of transverse momentum generated by collinear parton branchings. The current fragmentation is described via transverse momentum dependent parton densities and fragmentation functions. Target fragmentation instead is described via fracture functions. We present, to leading logarithmic accuracy, the corresponding semi-inclusive deep inelastic scattering cross-section, which applies to the entire phase space of the detected hadron. Some phenomenological implications and further developments are briefly outlined

PARAMETRIC DRAWINGS VS. AUTOLISP

OpenAIRE

PRUNĂ Liviu; SLONOVSCHI Andrei

2015-01-01

In this paper the authors make a critical analysis of the advantages offered by the parametric drawing use by comparison with the AutoLISP computer programs used when it comes about the parametric design. Studying and analysing these two work models the authors have got to some ideas and conclusions which should be considered in the moment in that someone must to decide if it is the case to elaborate a software, using the AutoLISP language, or to establish the base rules that must be followed...

Determination of the semi-empiric relationship among the physical density, the concentration and rate between hydrogen and manganese atoms, and a manganese sulfate solution; Determinacao da relacao semi-empirica entre a densidade fisica, concentracao e razao entre atomos de hidrogenio e manganes em uma solucao de sulfato de manganes

Energy Technology Data Exchange (ETDEWEB)

Bittencourt, Guilherme Rodrigues [Comissao Nacional de Energia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil). PIBIC; Castro, Leonardo Curvello de; Pereira, Walsan W.; Patrao, Karla C. de Souza; Fonseca, Evaldo S. da; Dantas, Maria Leticia [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Lab. Nacional de Metrologia das Radiacoes Ionizantes (LNMRI). Lab. de Neutrons

2009-07-01

The bath of a manganese sulfate (BMS) is a system for absolute standardization of the neutron sources. This work establishes a functional relationship based on semi-empirical methods for the theoretical prediction of physical density values, concentration and rate between the hydrogen and manganese atoms presents in the solution of the BMS

Impact of signal scattering and parametric uncertainties on receiver operating characteristics

Science.gov (United States)

Wilson, D. Keith; Breton, Daniel J.; Hart, Carl R.; Pettit, Chris L.

2017-05-01

The receiver operating characteristic (ROC curve), which is a plot of the probability of detection as a function of the probability of false alarm, plays a key role in the classical analysis of detector performance. However, meaningful characterization of the ROC curve is challenging when practically important complications such as variations in source emissions, environmental impacts on the signal propagation, uncertainties in the sensor response, and multiple sources of interference are considered. In this paper, a relatively simple but realistic model for scattered signals is employed to explore how parametric uncertainties impact the ROC curve. In particular, we show that parametric uncertainties in the mean signal and noise power substantially raise the tails of the distributions; since receiver operation with a very low probability of false alarm and a high probability of detection is normally desired, these tails lead to severely degraded performance. Because full a priori knowledge of such parametric uncertainties is rarely available in practice, analyses must typically be based on a finite sample of environmental states, which only partially characterize the range of parameter variations. We show how this effect can lead to misleading assessments of system performance. For the cases considered, approximately 64 or more statistically independent samples of the uncertain parameters are needed to accurately predict the probabilities of detection and false alarm. A connection is also described between selection of suitable distributions for the uncertain parameters, and Bayesian adaptive methods for inferring the parameters.

COMBINATION OF DENSITY AND ENERGY MODULATION IN MICROBUNCHING ANALYSIS

Energy Technology Data Exchange (ETDEWEB)

Tsai, Cheng Ying [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Li, Rui [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

2016-05-01

Microbunching instability (MBI) has been one of the most challenging issues in the transport of high-brightness electron beams for modern recirculating or energy recovery linac machines. Recently we have developed and implemented a Vlasov solver [1] to calculate the microbunching gain for an arbitrary beamline lattice, based on the extension of existing theoretical formulation [2-4] for the microbunching amplification from an initial density perturbation to the final density modulation. For more thorough analyses, in addition to the case of (initial) density to (final) density amplification, we extend in this paper the previous formulation to more general cases, including energy to density, density to energy and energy to energy amplifications for a recirculation machine. Such semi-analytical formulae are then incorporated into our Vlasov solver, and qualitative agreement is obtained when the semi-analytical Vlasov results are compared with particle tracking simulation using ELEGANT [5].

Semi-classical calculation of the spin-isospin response functions

International Nuclear Information System (INIS)

Chanfray, G.

1987-03-01

We present a semi-classical calculation of the nuclear response functions beyond the Thomas-Fermi approximation. We apply our formalism to the spin-isospin responses and show that the surface peaked h/2π corrections considerably decrease the ratio longitudinal/transverse as obtained through hadronic probes

Central depression of nuclear charge density distribution

International Nuclear Information System (INIS)

Chu Yanyun; Ren Zhongzhou; Wang Zaijun; Dong Tiekuang

2010-01-01

The center-depressed nuclear charge distributions are investigated with the parametrized distribution and the relativistic mean-field theory, and their corresponding charge form factors are worked out with the phase shift analysis method. The central depression of nuclear charge distribution of 46 Ar and 44 S is supported by the relativistic mean-field calculation. According to the calculation, the valence protons in 46 Ar and 44 S prefer to occupy the 1d 3/2 state rather than the 2s 1/2 state, which is different from that in the less neutron-rich argon and sulfur isotopes. As a result, the central proton densities of 46 Ar and 44 S are highly depressed, and so are their central charge densities. The charge form factors of some argon and sulfur isotopes are presented, and the minima of the charge form factors shift upward and inward when the central nuclear charge distributions are more depressed. Besides, the effect of the central depression on the charge form factors is studied with a parametrized distribution, when the root-mean-square charge radii remain constant.

Left-right asymmetry for pion and kaon production in the semi-inclusive deep-inelastic scattering process

International Nuclear Information System (INIS)

Sun, Bo; She, Jun; Zhang, Bing; Mao, Ya-Jun; Ma, Bo-Qiang

2010-01-01

We analyze the left-right asymmetry in the semi-inclusive deep-inelastic scattering (SIDIS) process without introducing any weighting functions. With the current theoretical understanding, we find that the Sivers effect plays a key role in our analysis. We use the latest parametrization of the Sivers and fragmentation functions to reanalyze the π ± production process and find that the results are sensitive to the parametrization. We also extend our calculation on the K ± production, which can help us know more about the Sivers distribution of the sea quarks and the unfavored fragmentation processes. HERMES kinematics with a proton target, COMPASS kinematics with a proton, deuteron, and neutron target (the information on the neutron target can be effectively extracted from the 3 He target), and JLab kinematics (both 6 GeV and 12 GeV) with a proton and neutron target are considered in our paper. (orig.)

Estimating technical efficiency in the hospital sector with panel data: a comparison of parametric and non-parametric techniques.

Science.gov (United States)

Siciliani, Luigi

2006-01-01

Policy makers are increasingly interested in developing performance indicators that measure hospital efficiency. These indicators may give the purchasers of health services an additional regulatory tool to contain health expenditure. Using panel data, this study compares different parametric (econometric) and non-parametric (linear programming) techniques for the measurement of a hospital's technical efficiency. This comparison was made using a sample of 17 Italian hospitals in the years 1996-9. Highest correlations are found in the efficiency scores between the non-parametric data envelopment analysis under the constant returns to scale assumption (DEA-CRS) and several parametric models. Correlation reduces markedly when using more flexible non-parametric specifications such as data envelopment analysis under the variable returns to scale assumption (DEA-VRS) and the free disposal hull (FDH) model. Correlation also generally reduces when moving from one output to two-output specifications. This analysis suggests that there is scope for developing performance indicators at hospital level using panel data, but it is important that extensive sensitivity analysis is carried out if purchasers wish to make use of these indicators in practice.

Connections between classical and parametric network entropies.

Directory of Open Access Journals (Sweden)

Matthias Dehmer

Full Text Available This paper explores relationships between classical and parametric measures of graph (or network complexity. Classical measures are based on vertex decompositions induced by equivalence relations. Parametric measures, on the other hand, are constructed by using information functions to assign probabilities to the vertices. The inequalities established in this paper relating classical and parametric measures lay a foundation for systematic classification of entropy-based measures of graph complexity.

Existence problem of proton semi-bubble structure in the 2{sub 1}{sup +} state of {sup 34}Si

Energy Technology Data Exchange (ETDEWEB)

Wu, Feng [China Institute of Atomic Energy, Beijing (China); Sichuan University, Key Laboratory of Radiation Physics and Technology of Ministry of Education, School of Physics Science and Technology, Chengdu (China); Bai, C.L. [Sichuan University, Key Laboratory of Radiation Physics and Technology of Ministry of Education, School of Physics Science and Technology, Chengdu (China); Yao, J.M. [University of North Carolina, Department of Physics and Astronomy, Chapel Hill, NC (United States); Southwest University, School of Physical Science and Technology, Chongqing (China); Zhang, H.Q.; Zhang, X.Z. [China Institute of Atomic Energy, Beijing (China)

2017-09-15

The fully self-consistent Hartree-Fock (HF) plus random phase approximation (RPA) based on Skyrme-type interaction is used to study the existence problem of proton semi-bubble structure in the 2{sub 1}{sup +} state of {sup 34}Si. The experimental excitation energy and the transition strength of the 2{sub 1}{sup +} state in {sup 34}Si can be reproduced quite well. The tensor effect is also studied. It is shown that the tensor interaction has a notable impact on the excitation energy of the 2{sub 1}{sup +} state and a small effect on the B(E2) value. Besides, its effect on the density distributions in the ground and 2{sub 1}{sup +} state of {sup 34}Si is negligible. Our present results with T36 and T44 show that the 2{sub 1}{sup +} state of {sup 34}Si is mainly caused by proton transition from π1d{sub 5/2} orbit to π2s{sub 1/2} orbit, and the existence of a proton semi-bubble structure in this state is very unlikely. (orig.)

Non-hydrostatic semi-elastic hybrid-coordinate SISL extension of HIRLAM. Part I: numerical scheme

Science.gov (United States)

Rõõm, Rein; Männik, Aarne; Luhamaa, Andres

2007-10-01

Two-time-level, semi-implicit, semi-Lagrangian (SISL) scheme is applied to the non-hydrostatic pressure coordinate equations, constituting a modified Miller-Pearce-White model, in hybrid-coordinate framework. Neutral background is subtracted in the initial continuous dynamics, yielding modified equations for geopotential, temperature and logarithmic surface pressure fluctuation. Implicit Lagrangian marching formulae for single time-step are derived. A disclosure scheme is presented, which results in an uncoupled diagnostic system, consisting of 3-D Poisson equation for omega velocity and 2-D Helmholtz equation for logarithmic pressure fluctuation. The model is discretized to create a non-hydrostatic extension to numerical weather prediction model HIRLAM. The discretization schemes, trajectory computation algorithms and interpolation routines, as well as the physical parametrization package are maintained from parent hydrostatic HIRLAM. For stability investigation, the derived SISL model is linearized with respect to the initial, thermally non-equilibrium resting state. Explicit residuals of the linear model prove to be sensitive to the relative departures of temperature and static stability from the reference state. Relayed on the stability study, the semi-implicit term in the vertical momentum equation is replaced to the implicit term, which results in stability increase of the model.

A tool for the estimation of the distribution of landslide area in R

Science.gov (United States)

Rossi, M.; Cardinali, M.; Fiorucci, F.; Marchesini, I.; Mondini, A. C.; Santangelo, M.; Ghosh, S.; Riguer, D. E. L.; Lahousse, T.; Chang, K. T.; Guzzetti, F.

2012-04-01

We have developed a tool in R (the free software environment for statistical computing, http://www.r-project.org/) to estimate the probability density and the frequency density of landslide area. The tool implements parametric and non-parametric approaches to the estimation of the probability density and the frequency density of landslide area, including: (i) Histogram Density Estimation (HDE), (ii) Kernel Density Estimation (KDE), and (iii) Maximum Likelihood Estimation (MLE). The tool is available as a standard Open Geospatial Consortium (OGC) Web Processing Service (WPS), and is accessible through the web using different GIS software clients. We tested the tool to compare Double Pareto and Inverse Gamma models for the probability density of landslide area in different geological, morphological and climatological settings, and to compare landslides shown in inventory maps prepared using different mapping techniques, including (i) field mapping, (ii) visual interpretation of monoscopic and stereoscopic aerial photographs, (iii) visual interpretation of monoscopic and stereoscopic VHR satellite images and (iv) semi-automatic detection and mapping from VHR satellite images. Results show that both models are applicable in different geomorphological settings. In most cases the two models provided very similar results. Non-parametric estimation methods (i.e., HDE and KDE) provided reasonable results for all the tested landslide datasets. For some of the datasets, MLE failed to provide a result, for convergence problems. The two tested models (Double Pareto and Inverse Gamma) resulted in very similar results for large and very large datasets (> 150 samples). Differences in the modeling results were observed for small datasets affected by systematic biases. A distinct rollover was observed in all analyzed landslide datasets, except for a few datasets obtained from landslide inventories prepared through field mapping or by semi-automatic mapping from VHR satellite imagery

Laser driven X-ray parametric amplification in neutral gases-a new brilliant light source in the XUV

International Nuclear Information System (INIS)

Aurand, B.; Seres, J.; Bagnoud, V.; Ecker, B.; Hochhaus, D.C.; Neumayer, P.; Seres, E.; Spielmann, C.; Zielbauer, B.; Zimmer, D.; Kuehl, T.

2011-01-01

In this paper we present the experimental setup and results showing a new type of strong-field parametric amplification of high-order harmonic radiation. With a simple semi-classical model, we can identify the most important experimental parameters, the spectral range and the small signal gain in gases. Using a single stage amplifier, a small signal gain of 8000 has been obtained in argon for the spectral range of 40-50 eV, using 350 fs, 7 mJ pulses at 1.05 μm. An outlook for an experiment employing a double stage gas system will be given.

Laser driven X-ray parametric amplification in neutral gases-a new brilliant light source in the XUV

Energy Technology Data Exchange (ETDEWEB)

Aurand, B., E-mail: b.aurand@gsi.de [GSI Helmholtz Centre for Heavy Ion Research, Planckstr. 1, 64291 Darmstadt (Germany); ExtreMe Matter Institute, Planckstr. 1, 64291 Darmstadt (Germany); Johannes Gutenberg University Mainz, Saarstr. 21, 55099 Mainz (Germany); Seres, J. [Friedrich-Schiller-University Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Bagnoud, V. [GSI Helmholtz Centre for Heavy Ion Research, Planckstr. 1, 64291 Darmstadt (Germany); Ecker, B. [GSI Helmholtz Centre for Heavy Ion Research, Planckstr. 1, 64291 Darmstadt (Germany); Helmholtz Institut Jena, Helmholtzweg 4, 07743 Jena (Germany); Johannes Gutenberg University Mainz, Saarstr. 21, 55099 Mainz (Germany); Hochhaus, D.C.; Neumayer, P. [GSI Helmholtz Centre for Heavy Ion Research, Planckstr. 1, 64291 Darmstadt (Germany); ExtreMe Matter Institute, Planckstr. 1, 64291 Darmstadt (Germany); Johann-Wolfgang von Goethe University, 60325 Frankfurt (Germany); Seres, E.; Spielmann, C. [Friedrich-Schiller-University Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Zielbauer, B. [GSI Helmholtz Centre for Heavy Ion Research, Planckstr. 1, 64291 Darmstadt (Germany); Helmholtz Institut Jena, Helmholtzweg 4, 07743 Jena (Germany); Zimmer, D. [GSI Helmholtz Centre for Heavy Ion Research, Planckstr. 1, 64291 Darmstadt (Germany); Kuehl, T. [GSI Helmholtz Centre for Heavy Ion Research, Planckstr. 1, 64291 Darmstadt (Germany); ExtreMe Matter Institute, Planckstr. 1, 64291 Darmstadt (Germany); Johannes Gutenberg University Mainz, Saarstr. 21, 55099 Mainz (Germany)

2011-10-11

In this paper we present the experimental setup and results showing a new type of strong-field parametric amplification of high-order harmonic radiation. With a simple semi-classical model, we can identify the most important experimental parameters, the spectral range and the small signal gain in gases. Using a single stage amplifier, a small signal gain of 8000 has been obtained in argon for the spectral range of 40-50 eV, using 350 fs, 7 mJ pulses at 1.05 {mu}m. An outlook for an experiment employing a double stage gas system will be given.

Nonscaling parametrization of hadronic spectra and dual parton model

International Nuclear Information System (INIS)

Gaponenko, O.N.

2001-01-01

Using the popular Wdowczyk-Wolfendale parametrization (WW-parametrization) as an example one studies restrictions imposed by a dual parton model for different nonscaling parametrizations of the pulsed hadron spectra in soft hadron-hadron and hadron-nuclear interactions. One derived a new parametrization free from basic drawback of the WW-formulae. In the central range the determined parametrization show agreement with the Wdowczyk-Wolfendale formula, but in contrast to the last-named one it does not result in contradiction with the experiment due to fast reduction of inelastic factor reduction with energy increase [ru

Direct application of Padé approximant for solving nonlinear differential equations.

Science.gov (United States)

Vazquez-Leal, Hector; Benhammouda, Brahim; Filobello-Nino, Uriel; Sarmiento-Reyes, Arturo; Jimenez-Fernandez, Victor Manuel; Garcia-Gervacio, Jose Luis; Huerta-Chua, Jesus; Morales-Mendoza, Luis Javier; Gonzalez-Lee, Mario

2014-01-01

This work presents a direct procedure to apply Padé method to find approximate solutions for nonlinear differential equations. Moreover, we present some cases study showing the strength of the method to generate highly accurate rational approximate solutions compared to other semi-analytical methods. The type of tested nonlinear equations are: a highly nonlinear boundary value problem, a differential-algebraic oscillator problem, and an asymptotic problem. The high accurate handy approximations obtained by the direct application of Padé method shows the high potential if the proposed scheme to approximate a wide variety of problems. What is more, the direct application of the Padé approximant aids to avoid the previous application of an approximative method like Taylor series method, homotopy perturbation method, Adomian Decomposition method, homotopy analysis method, variational iteration method, among others, as tools to obtain a power series solutions to post-treat with the Padé approximant. 34L30.

Solutions stability of one-dimensional parametric superconducting magnetic levitation model analysis by the first approximation

International Nuclear Information System (INIS)

Shvets', D.V.

2009-01-01

By the first approximation analyzing stability conditions of unperturbed solution of one-dimensional dynamic model with magnetic interaction between two superconducting rings obtained. The stability region in the frozen magnetic flux parameters space was constructed.

Parametric Methods for Order Tracking Analysis

DEFF Research Database (Denmark)

Nielsen, Jesper Kjær; Jensen, Tobias Lindstrøm

2017-01-01

Order tracking analysis is often used to find the critical speeds at which structural resonances are excited by a rotating machine. Typically, order tracking analysis is performed via non-parametric methods. In this report, however, we demonstrate some of the advantages of using a parametric method...

Explicit/multi-parametric model predictive control (MPC) of linear discrete-time systems by dynamic and multi-parametric programming

KAUST Repository

Kouramas, K.I.; Faí sca, N.P.; Panos, C.; Pistikopoulos, E.N.

2011-01-01

This work presents a new algorithm for solving the explicit/multi- parametric model predictive control (or mp-MPC) problem for linear, time-invariant discrete-time systems, based on dynamic programming and multi-parametric programming techniques

A new approach to the semi-classical relativistic two-body problem for charged fermions

International Nuclear Information System (INIS)

Leiter, D.

1978-01-01

Generalizing from a recently developed hybrid formulation of classical electrodynamics with ''direct (charge-field) action'' structure an analogous semi-classical Dirac formulation of the theory is constructed, which is capable of describing the semi-classical quantum mechanics of two identical spin-1/2 particles. This semi-classical formulation is to be used as a heuristic aid in searching for the theoretical structure of a fully ''second quantized'' theory. The Pauli exclusion principle is incorporated by making the interaction fields (in the action principle) antisymmetric with respect to ''charge-field'' labeling. In this manner, ''position correlation'' effects associated with ''configuration interaction'' can also be accounted for. By studying the nature of the stationary-state solutions, the formalism is compared with the conventional quantum-mechanical one (to understand the similarities and the differences between this approach and the usual correlated Hartree-Fock approximation of ordinary relativistic quantum theory). The stationary-state solutions to the semi-classical formalism are shown to closely approximate the usual quantum-mechanical solutions when the wave functions are represented as a superposition of Slater determinants of Dirac-Coulombic-type wave functions with radial parts having a form which extremizes the total Breit energy. The manner in which this semi-classical theory might be extended to a fully ''second quantized'' formalism is sketched. (author)

Approximated solutions to Born-Infeld dynamics

International Nuclear Information System (INIS)

Ferraro, Rafael; Nigro, Mauro

2016-01-01

The Born-Infeld equation in the plane is usefully captured in complex language. The general exact solution can be written as a combination of holomorphic and anti-holomorphic functions. However, this solution only expresses the potential in an implicit way. We rework the formulation to obtain the complex potential in an explicit way, by means of a perturbative procedure. We take care of the secular behavior common to this kind of approach, by resorting to a symmetry the equation has at the considered order of approximation. We apply the method to build approximated solutions to Born-Infeld electrodynamics. We solve for BI electromagnetic waves traveling in opposite directions. We study the propagation at interfaces, with the aim of searching for effects susceptible to experimental detection. In particular, we show that a reflected wave is produced when a wave is incident on a semi-space containing a magnetostatic field.

Approximated solutions to Born-Infeld dynamics

Energy Technology Data Exchange (ETDEWEB)

Ferraro, Rafael [Instituto de Astronomía y Física del Espacio (IAFE, CONICET-UBA),Casilla de Correo 67, Sucursal 28, 1428 Buenos Aires (Argentina); Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires,Ciudad Universitaria, Pabellón I, 1428 Buenos Aires (Argentina); Nigro, Mauro [Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires,Ciudad Universitaria, Pabellón I, 1428 Buenos Aires (Argentina)

2016-02-01

The Born-Infeld equation in the plane is usefully captured in complex language. The general exact solution can be written as a combination of holomorphic and anti-holomorphic functions. However, this solution only expresses the potential in an implicit way. We rework the formulation to obtain the complex potential in an explicit way, by means of a perturbative procedure. We take care of the secular behavior common to this kind of approach, by resorting to a symmetry the equation has at the considered order of approximation. We apply the method to build approximated solutions to Born-Infeld electrodynamics. We solve for BI electromagnetic waves traveling in opposite directions. We study the propagation at interfaces, with the aim of searching for effects susceptible to experimental detection. In particular, we show that a reflected wave is produced when a wave is incident on a semi-space containing a magnetostatic field.

Macromechanical Parametric Amplification

DEFF Research Database (Denmark)

Neumeyer, Stefan

between the two peaks can be altered. The first experimental bistable amplified steady-state responses are also reported. The derived analytical models and experimental setups can readily be extended to investigate other factors. Some of the results are also applicable to the more general field of systems...... for energy harvesting. Using analytical, numerical, and experimental methods, the thesis focuses on superthreshold pumping (above the systems parametric instability threshold), nonlinear effects, frequency response backbones, and frequency detuning effects for parametric amplifiers. Part one of the thesis...... covers superthreshold pumping and nonlinear effects. Superthresh-old pumping produces some useful characteristics. For instance, strong superthreshold pumping yields a high gain even though nonlinear effects tend to reduce it. In addition, a narrower excitation phase range is realized for which...

Comparative Study of Parametric and Non-parametric Approaches in Fault Detection and Isolation

DEFF Research Database (Denmark)

Katebi, S.D.; Blanke, M.; Katebi, M.R.

This report describes a comparative study between two approaches to fault detection and isolation in dynamic systems. The first approach uses a parametric model of the system. The main components of such techniques are residual and signature generation for processing and analyzing. The second...... approach is non-parametric in the sense that the signature analysis is only dependent on the frequency or time domain information extracted directly from the input-output signals. Based on these approaches, two different fault monitoring schemes are developed where the feature extraction and fault decision...

Tremor Detection Using Parametric and Non-Parametric Spectral Estimation Methods: A Comparison with Clinical Assessment

Science.gov (United States)

Martinez Manzanera, Octavio; Elting, Jan Willem; van der Hoeven, Johannes H.; Maurits, Natasha M.

2016-01-01

In the clinic, tremor is diagnosed during a time-limited process in which patients are observed and the characteristics of tremor are visually assessed. For some tremor disorders, a more detailed analysis of these characteristics is needed. Accelerometry and electromyography can be used to obtain a better insight into tremor. Typically, routine clinical assessment of accelerometry and electromyography data involves visual inspection by clinicians and occasionally computational analysis to obtain objective characteristics of tremor. However, for some tremor disorders these characteristics may be different during daily activity. This variability in presentation between the clinic and daily life makes a differential diagnosis more difficult. A long-term recording of tremor by accelerometry and/or electromyography in the home environment could help to give a better insight into the tremor disorder. However, an evaluation of such recordings using routine clinical standards would take too much time. We evaluated a range of techniques that automatically detect tremor segments in accelerometer data, as accelerometer data is more easily obtained in the home environment than electromyography data. Time can be saved if clinicians only have to evaluate the tremor characteristics of segments that have been automatically detected in longer daily activity recordings. We tested four non-parametric methods and five parametric methods on clinical accelerometer data from 14 patients with different tremor disorders. The consensus between two clinicians regarding the presence or absence of tremor on 3943 segments of accelerometer data was employed as reference. The nine methods were tested against this reference to identify their optimal parameters. Non-parametric methods generally performed better than parametric methods on our dataset when optimal parameters were used. However, one parametric method, employing the high frequency content of the tremor bandwidth under consideration

Quantum theory of parametric excitation in plasmas with the driving field space dispersion

International Nuclear Information System (INIS)

Vo Hong Anh

1998-11-01

A development of the quantum theory of parametric wave excitation in plasmas is presented to take into account the effects of space dispersion of the driving external fields. The quantum equation of motion method with the use of appropriate matrix formalism leads to the system of dispersion equations for the eigenmodes of vibrations. Calculations show the enlargement of the excitable waves region both in wave number values and directions as compared to the case of dipole approximation considered earlier. (author)

Energy scaling of terahertz-wave parametric sources.

Science.gov (United States)

Tang, Guanqi; Cong, Zhenhua; Qin, Zengguang; Zhang, Xingyu; Wang, Weitao; Wu, Dong; Li, Ning; Fu, Qiang; Lu, Qingming; Zhang, Shaojun

2015-02-23

Terahertz-wave parametric oscillators (TPOs) have advantages of room temperature operation, wide tunable range, narrow line-width, good coherence. They have also disadvantage of small pulse energy. In this paper, several factors preventing TPOs from generating high-energy THz pulses and the corresponding solutions are analyzed. A scheme to generate high-energy THz pulses by using the combination of a TPO and a Stokes-pulse-injected terahertz-wave parametric generator (spi-TPG) is proposed and demonstrated. A TPO is used as a source to generate a seed pulse for the surface-emitted spi-TPG. The time delay between the pump and Stokes pulses is adjusted to guarantee they have good temporal overlap. The pump pulses have a large pulse energy and a large beam size. The Stokes beam is enlarged to make its size be larger than the pump beam size to have a large effective interaction volume. The experimental results show that the generated THz pulse energy from the spi-TPG is 1.8 times as large as that obtained from the TPO for the same pumping pulse energy density of 0.90 J/cm(2) and the same pumping beam size of 3.0 mm. When the pumping beam sizes are 5.0 and 7.0 mm, the enhancement times are 3.7 and 7.5, respectively. The spi-TPG here is similar to a difference frequency generator; it can also be used as a Stokes pulse amplifier.

Irradiation sterilization of semi-crystalline polymers

International Nuclear Information System (INIS)

Williams, J.; Dunn, T.; Stannett, V.

1978-01-01

A semi-crystalline polymer such as polypropylene, is sterilized by high energy irradiation, with the polymer containing a non-crystalline mobilizing additive which increases the free volume of the polymer, to prevent embrittlement of the polymer during and subsequent to the irradiation. The additive has a density of from 0.6 to 1.9 g/cm 3 and a molecular weight from 100 to 10,000 g/mole

Zero- vs. one-dimensional, parametric vs. non-parametric, and confidence interval vs. hypothesis testing procedures in one-dimensional biomechanical trajectory analysis.

Science.gov (United States)

Pataky, Todd C; Vanrenterghem, Jos; Robinson, Mark A

2015-05-01

Biomechanical processes are often manifested as one-dimensional (1D) trajectories. It has been shown that 1D confidence intervals (CIs) are biased when based on 0D statistical procedures, and the non-parametric 1D bootstrap CI has emerged in the Biomechanics literature as a viable solution. The primary purpose of this paper was to clarify that, for 1D biomechanics datasets, the distinction between 0D and 1D methods is much more important than the distinction between parametric and non-parametric procedures. A secondary purpose was to demonstrate that a parametric equivalent to the 1D bootstrap exists in the form of a random field theory (RFT) correction for multiple comparisons. To emphasize these points we analyzed six datasets consisting of force and kinematic trajectories in one-sample, paired, two-sample and regression designs. Results showed, first, that the 1D bootstrap and other 1D non-parametric CIs were qualitatively identical to RFT CIs, and all were very different from 0D CIs. Second, 1D parametric and 1D non-parametric hypothesis testing results were qualitatively identical for all six datasets. Last, we highlight the limitations of 1D CIs by demonstrating that they are complex, design-dependent, and thus non-generalizable. These results suggest that (i) analyses of 1D data based on 0D models of randomness are generally biased unless one explicitly identifies 0D variables before the experiment, and (ii) parametric and non-parametric 1D hypothesis testing provide an unambiguous framework for analysis when one׳s hypothesis explicitly or implicitly pertains to whole 1D trajectories. Copyright © 2015 Elsevier Ltd. All rights reserved.

On the Influence of Piston and Cylinder Density in Tribodynamics of a Radial Piston Digital Fluid Power Displacement Motor

DEFF Research Database (Denmark)

Johansen, Per; Roemer, Daniel Beck; Andersen, Torben O.

2015-01-01

-stroke displacement simulations are used as basis for the parametric analysis. From the parametric analysis a change, in the minimum film thickness as function of piston and cylinder density, is shown for certain operating modes of the digital fluid power displacement motor. This indicate a need for careful....... In this paper the influence of the inertia term on the lubrication gaps of a radial piston motor are studied by a parametric analysis of the piston and cylinder density in a multibody tribodynamic simulation model. The motor is modeled as a digital fluid power displacement machine and a series of full...... assessment of the applicability, of the force balance condition, if it is used in multibody tribodynamic simulations of radial piston digital fluid power displacement motors....

Nuclear level density

International Nuclear Information System (INIS)

Cardoso Junior, J.L.

1982-10-01

Experimental data show that the number of nuclear states increases rapidly with increasing excitation energy. The properties of highly excited nuclei are important for many nuclear reactions, mainly those that go via processes of the compound nucleus type. In this case, it is sufficient to know the statistical properties of the nuclear levels. First of them is the function of nuclear levels density. Several theoretical models which describe the level density are presented. The statistical mechanics and a quantum mechanics formalisms as well as semi-empirical results are analysed and discussed. (Author) [pt

A Semi-Discrete Landweber-Kaczmarz Method for Cone Beam Tomography and Laminography Exploiting Geometric Prior Information

Science.gov (United States)

Vogelgesang, Jonas; Schorr, Christian

2016-12-01

We present a semi-discrete Landweber-Kaczmarz method for solving linear ill-posed problems and its application to Cone Beam tomography and laminography. Using a basis function-type discretization in the image domain, we derive a semi-discrete model of the underlying scanning system. Based on this model, the proposed method provides an approximate solution of the reconstruction problem, i.e. reconstructing the density function of a given object from its projections, in suitable subspaces equipped with basis function-dependent weights. This approach intuitively allows the incorporation of additional information about the inspected object leading to a more accurate model of the X-rays through the object. Also, physical conditions of the scanning geometry, like flat detectors in computerized tomography as used in non-destructive testing applications as well as non-regular scanning curves e.g. appearing in computed laminography (CL) applications, are directly taken into account during the modeling process. Finally, numerical experiments of a typical CL application in three dimensions are provided to verify the proposed method. The introduction of geometric prior information leads to a significantly increased image quality and superior reconstructions compared to standard iterative methods.

A general approach to optomechanical parametric instabilities

International Nuclear Information System (INIS)

Evans, M.; Barsotti, L.; Fritschel, P.

2010-01-01

We present a simple feedback description of parametric instabilities which can be applied to a variety of optical systems. Parametric instabilities are of particular interest to the field of gravitational-wave interferometry where high mechanical quality factors and a large amount of stored optical power have the potential for instability. In our use of Advanced LIGO as an example application, we find that parametric instabilities, if left unaddressed, present a potential threat to the stability of high-power operation.

Semi-solid metal forming of beryllium-reinforced aluminum alloys

International Nuclear Information System (INIS)

Haws, W.; Lane, L.; Marder, J.; Nicholas, N.

1995-01-01

A Powder Metallurgy (PM) based, Semi-Solid Metal (SSM) forming process has been developed to produce low cost near-net shapes of beryllium-reinforced aluminum alloys. Beryllium acts as a reinforcing additive to the aluminum, in which there is nearly no mutual solid solubility. The modulus of elasticity of the alloy dramatically increases, while the density and thermal expansion coefficient decrease with increasing beryllium content. The material is suitable for complex thermal management and vibration resistance applications, as well as for airborne components which are density and stiffness sensitive. The forming process involves heating a blank of the material to a temperature at which the aluminum is semi-solid and the beryllium is solid. The semi-solid blank is then injected without turbulence into a permanent mold. High quality, near net shape components can be produced which are functionally superior to those produced by other permanent mold processes. Dimensional accuracy is equivalent to or better than that obtained in high pressure die casting. Cost effectiveness is the primary advantage of this technique compared to other forming processes. The advantages and limitations of the process are described. Physical and mechanical property data are presented, as well as directions for future investigation

Density functionals from deep learning

OpenAIRE

McMahon, Jeffrey M.

2016-01-01

Density-functional theory is a formally exact description of a many-body quantum system in terms of its density; in practice, however, approximations to the universal density functional are required. In this work, a model based on deep learning is developed to approximate this functional. Deep learning allows computational models that are capable of naturally discovering intricate structure in large and/or high-dimensional data sets, with multiple levels of abstraction. As no assumptions are ...

Integrable multi parametric SU(N) chain

International Nuclear Information System (INIS)

Foerster, Angela; Roditi, Itzhak; Rodrigues, Ligia M.C.S.

1996-03-01

We analyse integrable models associated to a multi parametric SU(N) R-matrix. We show that the Hamiltonians describe SU(N) chains with twisted boundary conditions and that the underlying algebraic structure is the multi parametric deformation of SU(N) enlarged by the introduction of a central element. (author). 15 refs

Beyond-proximity-force-approximation Casimir force between two spheres at finite temperature

Science.gov (United States)

Bimonte, Giuseppe

2018-04-01

A recent experiment [J. L. Garrett, D. A. T. Somers, and J. N. Munday, Phys. Rev. Lett. 120, 040401 (2018), 10.1103/PhysRevLett.120.040401] measured for the first time the gradient of the Casimir force between two gold spheres at room temperature. The theoretical analysis of the data was carried out using the standard proximity force approximation (PFA). A fit of the data, using a parametrization of the force valid for the sphere-plate geometry, was used by the authors to place a bound on deviations from PFA. Motivated by this work, we compute the Casimir force between two gold spheres at finite temperature. The semianalytic formula for the Casimir force that we construct is valid for all separations, and can be easily used to interpret future experiments in both the sphere-plate and sphere-sphere configurations. We describe the correct parametrization of the corrections to PFA for two spheres that should be used in data analysis.

Parametric Thinking in Urban Design

DEFF Research Database (Denmark)

Steinø, Nicolai

2010-01-01

The paper states that most applications of parametric mod- elling to architecture and urban design fall into one of two strands of either form for form’s sake, or the negotiation of environmental con- cerns, while approaches which allow scenarios to be easily tested and modified without the appli...... of the paper. The pros and cons of this simple approach is discussed, and the paper con- cludes, that while it does not represent a suitable solution in all cases, it fills a gap among the existing approaches to parametric urban de- sign.......The paper states that most applications of parametric mod- elling to architecture and urban design fall into one of two strands of either form for form’s sake, or the negotiation of environmental con- cerns, while approaches which allow scenarios to be easily tested and modified without...

ASPEN: A fully kinetic, reduced-description particle-in-cell model for simulating parametric instabilities

International Nuclear Information System (INIS)

Vu, H.X.; Bezzerides, B.; DuBois, D.F.

1999-01-01

A fully kinetic, reduced-description particle-in-cell (RPIC) model is presented in which deviations from quasineutrality, electron and ion kinetic effects, and nonlinear interactions between low-frequency and high-frequency parametric instabilities are modeled correctly. The model is based on a reduced description where the electromagnetic field is represented by three separate temporal envelopes in order to model parametric instabilities with low-frequency and high-frequency daughter waves. Because temporal envelope approximations are invoked, the simulation can be performed on the electron time scale instead of the time scale of the light waves. The electrons and ions are represented by discrete finite-size particles, permitting electron and ion kinetic effects to be modeled properly. The Poisson equation is utilized to ensure that space-charge effects are included. The RPIC model is fully three dimensional and has been implemented in two dimensions on the Accelerated Strategic Computing Initiative (ASCI) parallel computer at Los Alamos National Laboratory, and the resulting simulation code has been named ASPEN. The authors believe this code is the first particle-in-cell code capable of simulating the interaction between low-frequency and high-frequency parametric instabilities in multiple dimensions. Test simulations of stimulated Raman scattering, stimulated Brillouin scattering, and Langmuir decay instability are presented

Towards a parametrization of multiparticle hadronic reactions

International Nuclear Information System (INIS)

Giffon, M.; Hama, Y.; Predazzi, E.

1979-11-01

An explicit parametrization of high energy exclusive production cross-sections is shown to give a reasonable account of inclusive data. This is a first step towards a phenomenological parametrization of multiparticle hadronic amplitudes

Convergent sum of gradient expansion of the kinetic-energy density functional up to the sixth order term using Padé approximant

Science.gov (United States)

Sergeev, A.; Alharbi, F. H.; Jovanovic, R.; Kais, S.

2016-04-01

The gradient expansion of the kinetic energy density functional, when applied to atoms or finite systems, usually grossly overestimates the energy in the fourth order and generally diverges in the sixth order. We avoid the divergence of the integral by replacing the asymptotic series including the sixth order term in the integrand by a rational function. Padé approximants show moderate improvements in accuracy in comparison with partial sums of the series. The results are discussed for atoms and Hooke’s law model for two-electron atoms.

Some notes on time dependent Thomas Fermi approximation

International Nuclear Information System (INIS)

Holzwarth, G.

1979-01-01

The successful use of effective density-dependent potentials in static Hartree-Fock calculations for nuclear ground-state properties has led to the question whether it is possible to obtain significant further simplification by approximating also the kinetic energy part of the ground state energy by a functional of the local density alone. The great advantage of such an approach is that its complexity is independent of particle number; the size of the system enters only through parameters, Z and N. The simple 'extended Thomas Fermi' functionals are based on the assumption of a spherically symmetric local Fermi surface throughout the nucleus and they represent the 'liquid drop' part of the static total energy. Given this static formalism which is solved directly for the local density without considering individual particles one might ask for a possible dynamical extension in the same sense as TDHF is a dynamical extension of the static HF approach. The aim of such a Time Dependent Thomas Fermi (TDTF) approximation would be to determine directly the time-dependent local single-particle density from given initial conditions and the single-particle current density without following each particle on its individual orbit

Approximate Inference and Deep Generative Models

CERN Multimedia

CERN. Geneva

2018-01-01

Advances in deep generative models are at the forefront of deep learning research because of the promise they offer for allowing data-efficient learning, and for model-based reinforcement learning. In this talk I'll review a few standard methods for approximate inference and introduce modern approximations which allow for efficient large-scale training of a wide variety of generative models. Finally, I'll demonstrate several important application of these models to density estimation, missing data imputation, data compression and planning.

Thermostatic properties of semi-infinite polarized nuclear matter

International Nuclear Information System (INIS)

Abd-Alla, M.; Hassan, M.Y.M.; Ramadan, S.

1988-03-01

The surface and curvature properties of semi-infinite polarized nuclear matter (SPNM) are calculated using an expansion for the Fermi integrals up to T 2 . A density matrix expansion is obtained for a modified form of Seyler-Blanchard interaction. New parameters that characterize the surface and curvature properties of SPNM are introduced. The level density parameter is extracted from the low temperature expansion of the free energy and compared with previous calculations. A reasonable agreement is obtained for the parameters calculated before. (author). 78 refs, 1 fig., 5 tabs

Autonomous Supervision and Control of Parametric Roll Resonance

DEFF Research Database (Denmark)

Galeazzi, Roberto

therefore two objectives. The first is to develop methods for detection of the inception of parametric roll resonance. The second is to develop control strategies to stabilize the motion after parametric roll has started. Stabilisation of parametric roll resonance points to two possible courses of action...... strategies are then combined to stabilise parametric roll resonance within few roll cycles. Limitations on the maximum stabilisable roll angle are analysed and linked to the ii slew rate saturation and hydrodynamic stall characteristics of the fin stabilisers. The study on maximum stabilisable roll angle...... leads to the requirements for early detection. Two novel detectors are proposed, which work within a shorttime prediction horizon, and issue early warnings of parametric roll inception within few roll cycles from its onset. The main idea behind these detection schemes is that of exploiting the link...

Comparing semi-analytic particle tagging and hydrodynamical simulations of the Milky Way's stellar halo

Science.gov (United States)

Cooper, Andrew P.; Cole, Shaun; Frenk, Carlos S.; Le Bret, Theo; Pontzen, Andrew

2017-08-01

Particle tagging is an efficient, but approximate, technique for using cosmological N-body simulations to model the phase-space evolution of the stellar populations predicted, for example, by a semi-analytic model of galaxy formation. We test the technique developed by Cooper et al. (which we call stings here) by comparing particle tags with stars in a smooth particle hydrodynamic (SPH) simulation. We focus on the spherically averaged density profile of stars accreted from satellite galaxies in a Milky Way (MW)-like system. The stellar profile in the SPH simulation can be recovered accurately by tagging dark matter (DM) particles in the same simulation according to a prescription based on the rank order of particle binding energy. Applying the same prescription to an N-body version of this simulation produces a density profile differing from that of the SPH simulation by ≲10 per cent on average between 1 and 200 kpc. This confirms that particle tagging can provide a faithful and robust approximation to a self-consistent hydrodynamical simulation in this regime (in contradiction to previous claims in the literature). We find only one systematic effect, likely due to the collisionless approximation, namely that massive satellites in the SPH simulation are disrupted somewhat earlier than their collisionless counterparts. In most cases, this makes remarkably little difference to the spherically averaged distribution of their stellar debris. We conclude that, for galaxy formation models that do not predict strong baryonic effects on the present-day DM distribution of MW-like galaxies or their satellites, differences in stellar halo predictions associated with the treatment of star formation and feedback are much more important than those associated with the dynamical limitations of collisionless particle tagging.

Electron heating caused by parametrically driven turbulence near the critical density

International Nuclear Information System (INIS)

Mizuno, K.; DeGroot, J.S.; Estabrook, K.G.

1986-01-01

Microwave-driven experiments and particle simulation calculations are presented that model s-polarized laser light incident on a pellet. In the microwave experiments, the incident microwaves are observed to decay into ion and electron waves near the critical density if the microwave power is above a well-defined threshold. Significant absorption, thermal electron heating, and hot electron generation are observed for microwave powers above a few times threshold. Strong absorption, strong profile modification, strongly heated hot electrons with a Maxwellian distribution, a hot-electron temperature that increases slowly with power, and a hot-electron density that is almost constant, are all observed in both the microwave experiments and simulation calculations for high powers. In addition, the thermal electrons are strongly heated for high powers in the microwave experiments

Parametric amplifications in the nonlinear transmission line

Energy Technology Data Exchange (ETDEWEB)

Kawata, T; Sakai, J; Inoue, H [Toyama Univ., Takaoka (Japan). Faculty of Engineering

1980-03-01

The parametric amplification in a transmission line with nonlinear capacitors is analysed theoretically using the equations of three wave interactions. Since this line has two modes, high frequency and low frequency modes, there may occur some mode coupling phenomena through the resonant interactions. We consider three waves with wave number k sub(j) and frequency ..omega..sub(j) in resonance with each other, that is, ..omega../sub 1/ + ..omega../sub 2/ = ..omega../sub 3/ and k/sub 1/ + k/sub 2/ = k/sub 3/, where 0 <= ..omega../sub 1/ <= ..omega../sub 2/ <= ..omega../sub 3/ and k/sub 3/ >= 0. Such conditions are realized in our network and there exist two states: ''forward state'' (each group velocity is positive) and ''backward state'' (one of the group velocities is negative). The coupled equations of three waves has two constant pumps: high frequency (HF) pump and low frequency (LF) pump. Using linear approximations, we examine the possible types of parametric amplification and obtain the power gains depending on the frequency deviation. For only the case of HF pump we get the gain between signals with seme frequency and also get the gain from the low frequency signal to the high frequency signal (''up-conversion'') for the LF pump. The nonlinear analysis gives the exact relation between input and output signals. For the forward state the gain is absolutely suppressed by the ratio of pumping power to input power, while the gain of backward state has no finite maximum and there may appear an ''oscillating state'' if the pumping power is comparatively small.

Interplay between topology and disorder in a two-dimensional semi-Dirac material

OpenAIRE

Sriluckshmy, P. V.; Saha, Kush; Moessner, Roderich

2017-01-01

We investigate the role of disorder in a two-dimensional semi-Dirac material characterized by a linear dispersion in one, and a parabolic dispersion in the orthogonal, direction. Using the self-consistent Born approximation, we show that disorder can drive a topological Lifshitz transition from an insulator to a semi-metal, as it generates a momentum independent off-diagonal contribution to the self-energy. Breaking time-reversal symmetry enriches the topological phase diagram with three dist...

Kernel-density estimation and approximate Bayesian computation for flexible epidemiological model fitting in Python.

Science.gov (United States)

Irvine, Michael A; Hollingsworth, T Déirdre

2018-05-26

Fitting complex models to epidemiological data is a challenging problem: methodologies can be inaccessible to all but specialists, there may be challenges in adequately describing uncertainty in model fitting, the complex models may take a long time to run, and it can be difficult to fully capture the heterogeneity in the data. We develop an adaptive approximate Bayesian computation scheme to fit a variety of epidemiologically relevant data with minimal hyper-parameter tuning by using an adaptive tolerance scheme. We implement a novel kernel density estimation scheme to capture both dispersed and multi-dimensional data, and directly compare this technique to standard Bayesian approaches. We then apply the procedure to a complex individual-based simulation of lymphatic filariasis, a human parasitic disease. The procedure and examples are released alongside this article as an open access library, with examples to aid researchers to rapidly fit models to data. This demonstrates that an adaptive ABC scheme with a general summary and distance metric is capable of performing model fitting for a variety of epidemiological data. It also does not require significant theoretical background to use and can be made accessible to the diverse epidemiological research community. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Audio Query by Example Using Similarity Measures between Probability Density Functions of Features

Directory of Open Access Journals (Sweden)

Marko Helén

2010-01-01

Full Text Available This paper proposes a query by example system for generic audio. We estimate the similarity of the example signal and the samples in the queried database by calculating the distance between the probability density functions (pdfs of their frame-wise acoustic features. Since the features are continuous valued, we propose to model them using Gaussian mixture models (GMMs or hidden Markov models (HMMs. The models parametrize each sample efficiently and retain sufficient information for similarity measurement. To measure the distance between the models, we apply a novel Euclidean distance, approximations of Kullback-Leibler divergence, and a cross-likelihood ratio test. The performance of the measures was tested in simulations where audio samples are automatically retrieved from a general audio database, based on the estimated similarity to a user-provided example. The simulations show that the distance between probability density functions is an accurate measure for similarity. Measures based on GMMs or HMMs are shown to produce better results than that of the existing methods based on simpler statistics or histograms of the features. A good performance with low computational cost is obtained with the proposed Euclidean distance.

Extended screened exchange functional derived from transcorrelated density functional theory.

Science.gov (United States)

Umezawa, Naoto

2017-09-14

We propose a new formulation of the correlation energy functional derived from the transcorrelated method in use in density functional theory (TC-DFT). An effective Hamiltonian, H TC , is introduced by a similarity transformation of a many-body Hamiltonian, H, with respect to a complex function F: H TC =1FHF. It is proved that an expectation value of H TC for a normalized single Slater determinant, D n , corresponds to the total energy: E[n] = ⟨Ψ n |H|Ψ n ⟩/⟨Ψ n |Ψ n ⟩ = ⟨D n |H TC |D n ⟩ under the two assumptions: (1) The electron density nr associated with a trial wave function Ψ n = D n F is v-representable and (2) Ψ n and D n give rise to the same electron density nr. This formulation, therefore, provides an alternative expression of the total energy that is useful for the development of novel correlation energy functionals. By substituting a specific function for F, we successfully derived a model correlation energy functional, which resembles the functional form of the screened exchange method. The proposed functional, named the extended screened exchange (ESX) functional, is described within two-body integrals and is parametrized for a numerically exact correlation energy of the homogeneous electron gas. The ESX functional does not contain any ingredients of (semi-)local functionals and thus is totally free from self-interactions. The computational cost for solving the self-consistent-field equation is comparable to that of the Hartree-Fock method. We apply the ESX functional to electronic structure calculations for a solid silicon, H - ion, and small atoms. The results demonstrate that the TC-DFT formulation is promising for the systematic improvement of the correlation energy functional.

Approximate Stokes Drift Profiles in Deep Water

Science.gov (United States)

Breivik, Øyvind; Janssen, Peter A. E. M.; Bidlot, Jean-Raymond

2014-09-01

A deep-water approximation to the Stokes drift velocity profile is explored as an alternative to the monochromatic profile. The alternative profile investigated relies on the same two quantities required for the monochromatic profile, viz the Stokes transport and the surface Stokes drift velocity. Comparisons with parametric spectra and profiles under wave spectra from the ERA-Interim reanalysis and buoy observations reveal much better agreement than the monochromatic profile even for complex sea states. That the profile gives a closer match and a more correct shear has implications for ocean circulation models since the Coriolis-Stokes force depends on the magnitude and direction of the Stokes drift profile and Langmuir turbulence parameterizations depend sensitively on the shear of the profile. The alternative profile comes at no added numerical cost compared to the monochromatic profile.

Universality for 1d Random Band Matrices: Sigma-Model Approximation

Science.gov (United States)

Shcherbina, Mariya; Shcherbina, Tatyana

2018-02-01

The paper continues the development of the rigorous supersymmetric transfer matrix approach to the random band matrices started in (J Stat Phys 164:1233-1260, 2016; Commun Math Phys 351:1009-1044, 2017). We consider random Hermitian block band matrices consisting of W× W random Gaussian blocks (parametrized by j,k \\in Λ =[1,n]^d\\cap Z^d ) with a fixed entry's variance J_{jk}=δ _{j,k}W^{-1}+β Δ _{j,k}W^{-2} , β >0 in each block. Taking the limit W→ ∞ with fixed n and β , we derive the sigma-model approximation of the second correlation function similar to Efetov's one. Then, considering the limit β , n→ ∞, we prove that in the dimension d=1 the behaviour of the sigma-model approximation in the bulk of the spectrum, as β ≫ n , is determined by the classical Wigner-Dyson statistics.

Density functional theory

International Nuclear Information System (INIS)

Das, M.P.

1984-07-01

The state of the art of the density functional formalism (DFT) is reviewed. The theory is quantum statistical in nature; its simplest version is the well-known Thomas-Fermi theory. The DFT is a powerful formalism in which one can treat the effect of interactions in inhomogeneous systems. After some introductory material, the DFT is outlined from the two basic theorems, and various generalizations of the theorems appropriate to several physical situations are pointed out. Next, various approximations to the density functionals are presented and some practical schemes, discussed; the approximations include an electron gas of almost constant density and an electron gas of slowly varying density. Then applications of DFT in various diverse areas of physics (atomic systems, plasmas, liquids, nuclear matter) are mentioned, and its strengths and weaknesses are pointed out. In conclusion, more recent developments of DFT are indicated

Parametric form of QCD travelling waves

OpenAIRE

Peschanski, R.

2005-01-01

We derive parametric travelling-wave solutions of non-linear QCD equations. They describe the evolution towards saturation in the geometric scaling region. The method, based on an expansion in the inverse of the wave velocity, leads to a solvable hierarchy of differential equations. A universal parametric form of travelling waves emerges from the first two orders of the expansion.

Bianchi surfaces: integrability in an arbitrary parametrization

International Nuclear Information System (INIS)

Nieszporski, Maciej; Sym, Antoni

2009-01-01

We discuss integrability of normal field equations of arbitrarily parametrized Bianchi surfaces. A geometric definition of the Bianchi surfaces is presented as well as the Baecklund transformation for the normal field equations in an arbitrarily chosen surface parametrization.

Single-particle energies and density of states in density functional theory

Science.gov (United States)

van Aggelen, H.; Chan, G. K.-L.

2015-07-01

Time-dependent density functional theory (TD-DFT) is commonly used as the foundation to obtain neutral excited states and transition weights in DFT, but does not allow direct access to density of states and single-particle energies, i.e. ionisation energies and electron affinities. Here we show that by extending TD-DFT to a superfluid formulation, which involves operators that break particle-number symmetry, we can obtain the density of states and single-particle energies from the poles of an appropriate superfluid response function. The standard Kohn- Sham eigenvalues emerge as the adiabatic limit of the superfluid response under the assumption that the exchange- correlation functional has no dependence on the superfluid density. The Kohn- Sham eigenvalues can thus be interpreted as approximations to the ionisation energies and electron affinities. Beyond this approximation, the formalism provides an incentive for creating a new class of density functionals specifically targeted at accurate single-particle eigenvalues and bandgaps.

Parametric and Non-Parametric Vibration-Based Structural Identification Under Earthquake Excitation

Science.gov (United States)

Pentaris, Fragkiskos P.; Fouskitakis, George N.

2014-05-01

The problem of modal identification in civil structures is of crucial importance, and thus has been receiving increasing attention in recent years. Vibration-based methods are quite promising as they are capable of identifying the structure's global characteristics, they are relatively easy to implement and they tend to be time effective and less expensive than most alternatives [1]. This paper focuses on the off-line structural/modal identification of civil (concrete) structures subjected to low-level earthquake excitations, under which, they remain within their linear operating regime. Earthquakes and their details are recorded and provided by the seismological network of Crete [2], which 'monitors' the broad region of south Hellenic arc, an active seismic region which functions as a natural laboratory for earthquake engineering of this kind. A sufficient number of seismic events are analyzed in order to reveal the modal characteristics of the structures under study, that consist of the two concrete buildings of the School of Applied Sciences, Technological Education Institute of Crete, located in Chania, Crete, Hellas. Both buildings are equipped with high-sensitivity and accuracy seismographs - providing acceleration measurements - established at the basement (structure's foundation) presently considered as the ground's acceleration (excitation) and at all levels (ground floor, 1st floor, 2nd floor and terrace). Further details regarding the instrumentation setup and data acquisition may be found in [3]. The present study invokes stochastic, both non-parametric (frequency-based) and parametric methods for structural/modal identification (natural frequencies and/or damping ratios). Non-parametric methods include Welch-based spectrum and Frequency response Function (FrF) estimation, while parametric methods, include AutoRegressive (AR), AutoRegressive with eXogeneous input (ARX) and Autoregressive Moving-Average with eXogeneous input (ARMAX) models[4, 5

PARAMETRIC DRAWINGS VS. AUTOLISP

Directory of Open Access Journals (Sweden)

PRUNĂ Liviu

2015-06-01

Full Text Available In this paper the authors make a critical analysis of the advantages offered by the parametric drawing use by comparison with the AutoLISP computer programs used when it comes about the parametric design. Studying and analysing these two work models the authors have got to some ideas and conclusions which should be considered in the moment in that someone must to decide if it is the case to elaborate a software, using the AutoLISP language, or to establish the base rules that must be followed by the drawing, in the idea to construct outlines or blocks which can be used in the projection process.

Fault detection and isolation in systems with parametric faults

DEFF Research Database (Denmark)

Stoustrup, Jakob; Niemann, Hans Henrik

1999-01-01

The problem of fault detection and isolation of parametric faults is considered in this paper. A fault detection problem based on parametric faults are associated with internal parameter variations in the dynamical system. A fault detection and isolation method for parametric faults is formulated...

Semiclassical approximations for gravity and the issue of backreaction

International Nuclear Information System (INIS)

Padmanabhan, T.

1989-01-01

Semiclassical approximations, which are useful in the study of a quantum system interacting with a classical system, are studied and compared. In particular, we consider the Born-Oppenheimer approximation (BOA) (corresponding to G → O at fixed ℎ), the effective action approach (ℎ → O at fixed G) and their combinations. We show that in the strict BOA limit there is no backreaction on gravity. In the effective action approach one can obtain a semi-classical description of gravity, if certain stringent requirements are satisfied. In most situations of interest these conditions will not be met and the O(ℎ) contribution from gravitons will be comparable to that from quantum fields. (author)

Pump to signal noise transfer in parametric fiber amplifiers

DEFF Research Database (Denmark)

Lund-Hansen, Toke; Rottwitt, Karsten; Peucheret, Christophe

2010-01-01

Fiber optic parametric amplifiers have been suggested due to their potential low spontaneous emission. However, by nature the parametric amplifier only work in a forward pumped configuration, which result in transfer of relative intensity noise in the pump to the signal.......Fiber optic parametric amplifiers have been suggested due to their potential low spontaneous emission. However, by nature the parametric amplifier only work in a forward pumped configuration, which result in transfer of relative intensity noise in the pump to the signal....

Parametric analysis of ATM solar array.

Science.gov (United States)

Singh, B. K.; Adkisson, W. B.

1973-01-01

The paper discusses the methods used for the calculation of ATM solar array performance characteristics and provides the parametric analysis of solar panels used in SKYLAB. To predict the solar array performance under conditions other than test conditions, a mathematical model has been developed. Four computer programs have been used to convert the solar simulator test data to the parametric curves. The first performs module summations, the second determines average solar cell characteristics which will cause a mathematical model to generate a curve matching the test data, the third is a polynomial fit program which determines the polynomial equations for the solar cell characteristics versus temperature, and the fourth program uses the polynomial coefficients generated by the polynomial curve fit program to generate the parametric data.

A variational approach to moment-closure approximations for the kinetics of biomolecular reaction networks

Science.gov (United States)

Bronstein, Leo; Koeppl, Heinz

2018-01-01

Approximate solutions of the chemical master equation and the chemical Fokker-Planck equation are an important tool in the analysis of biomolecular reaction networks. Previous studies have highlighted a number of problems with the moment-closure approach used to obtain such approximations, calling it an ad hoc method. In this article, we give a new variational derivation of moment-closure equations which provides us with an intuitive understanding of their properties and failure modes and allows us to correct some of these problems. We use mixtures of product-Poisson distributions to obtain a flexible parametric family which solves the commonly observed problem of divergences at low system sizes. We also extend the recently introduced entropic matching approach to arbitrary ansatz distributions and Markov processes, demonstrating that it is a special case of variational moment closure. This provides us with a particularly principled approximation method. Finally, we extend the above approaches to cover the approximation of multi-time joint distributions, resulting in a viable alternative to process-level approximations which are often intractable.

Parametric Instability in Advanced Laser Interferometer Gravitational Wave Detectors

International Nuclear Information System (INIS)

Ju, L; Grass, S; Zhao, C; Degallaix, J; Blair, D G

2006-01-01

High frequency parametric instabilities in optical cavities are radiation pressure induced interactions between test mass mechanical modes and cavity optical modes. The parametric gain depends on the cavity power and the quality factor of the test mass internal modes (usually in ultrasonic frequency range), as well as the overlap integral for the mechanical and optical modes. In advanced laser interferometers which require high optical power and very low acoustic loss test masses, parametric instabilities could prevent interferometer operation if not suppressed. Here we review the problem of parametric instabilities in advanced detector configurations for different combinations of sapphire and fused silica test masses, and compare three methods for control or suppression of parametric instabilities-thermal tuning, surface damping and active feedback

SemiBoost: boosting for semi-supervised learning.

Science.gov (United States)

Mallapragada, Pavan Kumar; Jin, Rong; Jain, Anil K; Liu, Yi

2009-11-01

Semi-supervised learning has attracted a significant amount of attention in pattern recognition and machine learning. Most previous studies have focused on designing special algorithms to effectively exploit the unlabeled data in conjunction with labeled data. Our goal is to improve the classification accuracy of any given supervised learning algorithm by using the available unlabeled examples. We call this as the Semi-supervised improvement problem, to distinguish the proposed approach from the existing approaches. We design a metasemi-supervised learning algorithm that wraps around the underlying supervised algorithm and improves its performance using unlabeled data. This problem is particularly important when we need to train a supervised learning algorithm with a limited number of labeled examples and a multitude of unlabeled examples. We present a boosting framework for semi-supervised learning, termed as SemiBoost. The key advantages of the proposed semi-supervised learning approach are: 1) performance improvement of any supervised learning algorithm with a multitude of unlabeled data, 2) efficient computation by the iterative boosting algorithm, and 3) exploiting both manifold and cluster assumption in training classification models. An empirical study on 16 different data sets and text categorization demonstrates that the proposed framework improves the performance of several commonly used supervised learning algorithms, given a large number of unlabeled examples. We also show that the performance of the proposed algorithm, SemiBoost, is comparable to the state-of-the-art semi-supervised learning algorithms.

Parametric distribution approach for flow availability in small hydro potential analysis

Science.gov (United States)

Abdullah, Samizee; Basri, Mohd Juhari Mat; Jamaluddin, Zahrul Zamri; Azrulhisham, Engku Ahmad; Othman, Jamel

2016-10-01

Small hydro system is one of the important sources of renewable energy and it has been recognized worldwide as clean energy sources. Small hydropower generation system uses the potential energy in flowing water to produce electricity is often questionable due to inconsistent and intermittent of power generated. Potential analysis of small hydro system which is mainly dependent on the availability of water requires the knowledge of water flow or stream flow distribution. This paper presented the possibility of applying Pearson system for stream flow availability distribution approximation in the small hydro system. By considering the stochastic nature of stream flow, the Pearson parametric distribution approximation was computed based on the significant characteristic of Pearson system applying direct correlation between the first four statistical moments of the distribution. The advantage of applying various statistical moments in small hydro potential analysis will have the ability to analyze the variation shapes of stream flow distribution.