Supplementary motor area as key structure for domain-general sequence processing: A unified account.

PubMed

Cona, Giorgia; Semenza, Carlo

2017-01-01

The Supplementary Motor Area (SMA) is considered as an anatomically and functionally heterogeneous region and is implicated in several functions. We propose that SMA plays a crucial role in domain-general sequence processes, contributing to the integration of sequential elements into higher-order representations regardless of the nature of such elements (e.g., motor, temporal, spatial, numerical, linguistic, etc.). This review emphasizes the domain-general involvement of the SMA, as this region has been found to support sequence operations in a variety of cognitive domains that, albeit different, share an inherent sequence processing. These include action, time and spatial processing, numerical cognition, music and language processing, and working memory. In this light, we reviewed and synthesized recent neuroimaging, stimulation and electrophysiological studies in order to compare and reconcile the distinct sources of data by proposing a unifying account for the role of the SMA. We also discussed the differential contribution of the pre-SMA and SMA-proper in sequence operations, and possible neural mechanisms by which such operations are executed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Working memory deficits in developmental dyscalculia: The importance of serial order.

PubMed

Attout, Lucie; Majerus, Steve

2015-01-01

Although a number of studies suggests a link between working memory (WM) storage capacity of short-term memory and calculation abilities, the nature of verbal WM deficits in children with developmental dyscalculia (DD) remains poorly understood. We explored verbal WM capacity in DD by focusing on the distinction between memory for item information (the items to be retained) and memory for order information (the order of the items within a list). We hypothesized that WM for order could be specifically related to impaired numerical abilities given that recent studies suggest close interactions between the representation of order information in WM and ordinal numerical processing. We investigated item and order WM abilities as well as basic numerical processing abilities in 16 children with DD (age: 8-11 years) and 16 typically developing children matched on age, IQ, and reading abilities. The DD group performed significantly poorer than controls in the order WM condition but not in the item WM condition. In addition, the DD group performed significantly slower than the control group on a numerical order judgment task. The present results show significantly reduced serial order WM abilities in DD coupled with less efficient numerical ordinal processing abilities, reflecting more general difficulties in explicit processing of ordinal information.

Efficient numerical evaluation of Feynman integrals

NASA Astrophysics Data System (ADS)

Li, Zhao; Wang, Jian; Yan, Qi-Shu; Zhao, Xiaoran

2016-03-01

Feynman loop integrals are a key ingredient for the calculation of higher order radiation effects, and are responsible for reliable and accurate theoretical prediction. We improve the efficiency of numerical integration in sector decomposition by implementing a quasi-Monte Carlo method associated with the CUDA/GPU technique. For demonstration we present the results of several Feynman integrals up to two loops in both Euclidean and physical kinematic regions in comparison with those obtained from FIESTA3. It is shown that both planar and non-planar two-loop master integrals in the physical kinematic region can be evaluated in less than half a minute with accuracy, which makes the direct numerical approach viable for precise investigation of higher order effects in multi-loop processes, e.g. the next-to-leading order QCD effect in Higgs pair production via gluon fusion with a finite top quark mass. Supported by the Natural Science Foundation of China (11305179 11475180), Youth Innovation Promotion Association, CAS, IHEP Innovation (Y4545170Y2), State Key Lab for Electronics and Particle Detectors, Open Project Program of State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, China (Y4KF061CJ1), Cluster of Excellence Precision Physics, Fundamental Interactions and Structure of Matter (PRISMA-EXC 1098)

Data Mining on Numeric Error in Computerized Physician Order Entry System Prescriptions.

PubMed

Wu, Xue; Wu, Changxu

2017-01-01

This study revealed the numeric error patterns related to dosage when doctors prescribed in computerized physician order entry system. Error categories showed that the '6','7', and '9' key produced a higher incidence of errors in Numpad typing, while the '2','3', and '0' key produced a higher incidence of errors in main keyboard digit line typing. Errors categorized as omission and substitution were higher in prevalence than transposition and intrusion.

Numerical Manifold Method for the Forced Vibration of Thin Plates during Bending

PubMed Central

Jun, Ding; Song, Chen; Wei-Bin, Wen; Shao-Ming, Luo; Xia, Huang

2014-01-01

A novel numerical manifold method was derived from the cubic B-spline basis function. The new interpolation function is characterized by high-order coordination at the boundary of a manifold element. The linear elastic-dynamic equation used to solve the bending vibration of thin plates was derived according to the principle of minimum instantaneous potential energy. The method for the initialization of the dynamic equation and its solution process were provided. Moreover, the analysis showed that the calculated stiffness matrix exhibited favorable performance. Numerical results showed that the generalized degrees of freedom were significantly fewer and that the calculation accuracy was higher for the manifold method than for the conventional finite element method. PMID:24883403

Python Open source Waveform ExtractoR (POWER): an open source, Python package to monitor and post-process numerical relativity simulations

NASA Astrophysics Data System (ADS)

Johnson, Daniel; Huerta, E. A.; Haas, Roland

2018-01-01

Numerical simulations of Einstein’s field equations provide unique insights into the physics of compact objects moving at relativistic speeds, and which are driven by strong gravitational interactions. Numerical relativity has played a key role to firmly establish gravitational wave astrophysics as a new field of research, and it is now paving the way to establish whether gravitational wave radiation emitted from compact binary mergers is accompanied by electromagnetic and astro-particle counterparts. As numerical relativity continues to blend in with routine gravitational wave data analyses to validate the discovery of gravitational wave events, it is essential to develop open source tools to streamline these studies. Motivated by our own experience as users and developers of the open source, community software, the Einstein Toolkit, we present an open source, Python package that is ideally suited to monitor and post-process the data products of numerical relativity simulations, and compute the gravitational wave strain at future null infinity in high performance environments. We showcase the application of this new package to post-process a large numerical relativity catalog and extract higher-order waveform modes from numerical relativity simulations of eccentric binary black hole mergers and neutron star mergers. This new software fills a critical void in the arsenal of tools provided by the Einstein Toolkit consortium to the numerical relativity community.

Earthquake Rupture Dynamics using Adaptive Mesh Refinement and High-Order Accurate Numerical Methods

NASA Astrophysics Data System (ADS)

Kozdon, J. E.; Wilcox, L.

2013-12-01

Our goal is to develop scalable and adaptive (spatial and temporal) numerical methods for coupled, multiphysics problems using high-order accurate numerical methods. To do so, we are developing an opensource, parallel library known as bfam (available at http://bfam.in). The first application to be developed on top of bfam is an earthquake rupture dynamics solver using high-order discontinuous Galerkin methods and summation-by-parts finite difference methods. In earthquake rupture dynamics, wave propagation in the Earth's crust is coupled to frictional sliding on fault interfaces. This coupling is two-way, required the simultaneous simulation of both processes. The use of laboratory-measured friction parameters requires near-fault resolution that is 4-5 orders of magnitude higher than that needed to resolve the frequencies of interest in the volume. This, along with earlier simulations using a low-order, finite volume based adaptive mesh refinement framework, suggest that adaptive mesh refinement is ideally suited for this problem. The use of high-order methods is motivated by the high level of resolution required off the fault in earlier the low-order finite volume simulations; we believe this need for resolution is a result of the excessive numerical dissipation of low-order methods. In bfam spatial adaptivity is handled using the p4est library and temporal adaptivity will be accomplished through local time stepping. In this presentation we will present the guiding principles behind the library as well as verification of code against the Southern California Earthquake Center dynamic rupture code validation test problems.

Modulational instability and dynamics of implicit higher-order rogue wave solutions for the Kundu equation

NASA Astrophysics Data System (ADS)

Wen, Xiao-Yong; Zhang, Guoqiang

2018-01-01

Under investigation in this paper is the Kundu equation, which may be used to describe the propagation process of ultrashort optical pulses in nonlinear optics. The modulational instability of the plane-wave for the possible reason of the formation of the rogue wave (RW) is studied for the system. Based on our proposed generalized perturbation (n,N - n)-fold Darboux transformation (DT), some new higher-order implicit RW solutions in terms of determinants are obtained by means of the generalized perturbation (1,N - 1)-fold DT, when choosing different special parameters, these results will reduce to the RW solutions of the Kaup-Newell (KN) equation, Chen-Lee-Liu (CLL) equation and Gerjikov-Ivanov (GI) equation, respectively. The relevant wave structures are shown graphically, which display abundant interesting wave structures. The dynamical behaviors and propagation stability of the first-order and second-order RW solutions are discussed by using numerical simulations, the higher-order nonlinear terms for the Kundu equation have an impact on the propagation instability of the RW. The method can also be extended to find the higher-order RW or rational solutions of other integrable nonlinear equations.

Numerical method based on the lattice Boltzmann model for the Fisher equation.

PubMed

Yan, Guangwu; Zhang, Jianying; Dong, Yinfeng

2008-06-01

In this paper, a lattice Boltzmann model for the Fisher equation is proposed. First, the Chapman-Enskog expansion and the multiscale time expansion are used to describe higher-order moment of equilibrium distribution functions and a series of partial differential equations in different time scales. Second, the modified partial differential equation of the Fisher equation with the higher-order truncation error is obtained. Third, comparison between numerical results of the lattice Boltzmann models and exact solution is given. The numerical results agree well with the classical ones.

A simplified parsimonious higher order multivariate Markov chain model

NASA Astrophysics Data System (ADS)

Wang, Chao; Yang, Chuan-sheng

2017-09-01

In this paper, a simplified parsimonious higher-order multivariate Markov chain model (SPHOMMCM) is presented. Moreover, parameter estimation method of TPHOMMCM is give. Numerical experiments shows the effectiveness of TPHOMMCM.

A tridiagonal parsimonious higher order multivariate Markov chain model

NASA Astrophysics Data System (ADS)

Wang, Chao; Yang, Chuan-sheng

2017-09-01

In this paper, we present a tridiagonal parsimonious higher-order multivariate Markov chain model (TPHOMMCM). Moreover, estimation method of the parameters in TPHOMMCM is give. Numerical experiments illustrate the effectiveness of TPHOMMCM.

Nonlinear breakup of liquid sheets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jazayeri, S.A.; Li, X.

1997-07-01

Sprays formed from the disintegration of liquid sheets have extensive practical applications, ranging from chemical and pharmaceutical processes to power generation and propulsion systems. A knowledge of the liquid sheet breakup process is essential to the understanding of fundamental mechanism of liquid atomization and spray formation processes. The breakup of liquid sheets has been investigated in terms of hydrodynamic stability via linear analysis by Squire, Hagerty and Shea, Li, etc. nonlinear effect has been studied by Clark and Dombrowski up to the second order, and by Rangel and Sirignano through numerical simulation employing vortex discretization method. As shown by Taubmore » for the breakup of circular liquid jets, the closer to the breakup region, the higher the order of nonlinear analysis has to be for adequate description of the breakup behavior. As pointed out by Bogy, a nonlinear analysis up to the third order is generally sufficient to account for the inherent nonlinear nature of the breakup process. Therefore, a third-order nonlinear analysis has been carried out in this study to investigate the process of liquid sheet disruption preceding the spray formation.« less

Development of a Higher Order Laminate Theory for Modeling Composites with Induced Strain Actuators

NASA Technical Reports Server (NTRS)

Chattopadhyay, Aditi; Seeley, Charles E.

1996-01-01

A refined higher order plate theory is developed to investigate the actuation mechanism of piezoelectric materials surface bonded or embedded in composite laminates. The current analysis uses a displacement field which accurately accounts for transverse shear stresses. Some higher order terms are identified by using the conditions that shear stresses vanish at all free surfaces. Therefore, all boundary conditions for displacements and stresses are satisfied in the present theory. The analysis is implemented using the finite element method which provides a convenient means to construct a numerical solution due to the discrete nature of the actuators. The higher order theory is computationally less expensive than a full three dimensional analysis. The theory is also shown to agree well with published experimental results. Numerical examples are presented for composite plates with thicknesses ranging from thin to very thick.

Modeling of single film bubble and numerical study of the plateau structure in foam system

NASA Astrophysics Data System (ADS)

Sun, Zhong-guo; Ni, Ni; Sun, Yi-jie; Xi, Guang

2018-02-01

The single-film bubble has a special geometry with a certain amount of gas shrouded by a thin layer of liquid film under the surface tension force both on the inside and outside surfaces of the bubble. Based on the mesh-less moving particle semi-implicit (MPS) method, a single-film double-gas-liquid-interface surface tension (SDST) model is established for the single-film bubble, which characteristically has totally two gas-liquid interfaces on both sides of the film. Within this framework, the conventional surface free energy surface tension model is improved by using a higher order potential energy equation between particles, and the modification results in higher accuracy and better symmetry properties. The complex interface movement in the oscillation process of the single-film bubble is numerically captured, as well as typical flow phenomena and deformation characteristics of the liquid film. In addition, the basic behaviors of the coalescence and connection process between two and even three single-film bubbles are studied, and the cases with bubbles of different sizes are also included. Furthermore, the classic plateau structure in the foam system is reproduced and numerically proved to be in the steady state for multi-bubble connections.

Numerical modeling of materials processing applications of a pulsed cold cathode electron gun

NASA Astrophysics Data System (ADS)

Etcheverry, J. I.; Martínez, O. E.; Mingolo, N.

1998-04-01

A numerical study of the application of a pulsed cold cathode electron gun to materials processing is performed. A simple semiempirical model of the discharge is used, together with backscattering and energy deposition profiles obtained by a Monte Carlo technique, in order to evaluate the energy source term inside the material. The numerical computation of the heat equation with the calculated source term is performed in order to obtain useful information on melting and vaporization thresholds, melted radius and depth, and on the dependence of these variables on processing parameters such as operating pressure, initial voltage of the discharge and cathode-sample distance. Numerical results for stainless steel are presented, which demonstrate the need for several modifications of the experimental design in order to achieve a better efficiency.

High order volume-preserving algorithms for relativistic charged particles in general electromagnetic fields

NASA Astrophysics Data System (ADS)

He, Yang; Sun, Yajuan; Zhang, Ruili; Wang, Yulei; Liu, Jian; Qin, Hong

2016-09-01

We construct high order symmetric volume-preserving methods for the relativistic dynamics of a charged particle by the splitting technique with processing. By expanding the phase space to include the time t, we give a more general construction of volume-preserving methods that can be applied to systems with time-dependent electromagnetic fields. The newly derived methods provide numerical solutions with good accuracy and conservative properties over long time of simulation. Furthermore, because of the use of an accuracy-enhancing processing technique, the explicit methods obtain high-order accuracy and are more efficient than the methods derived from standard compositions. The results are verified by the numerical experiments. Linear stability analysis of the methods shows that the high order processed method allows larger time step size in numerical integrations.

Are Arabic and Verbal Numbers Processed in Different Ways?

ERIC Educational Resources Information Center

Kadosh, Roi Cohen; Henik, Avishai; Rubinsten, Orly

2008-01-01

Four experiments were conducted in order to examine effects of notation--Arabic and verbal numbers--on relevant and irrelevant numerical processing. In Experiment 1, notation interacted with the numerical distance effect, and irrelevant physical size affected numerical processing (i.e., size congruity effect) for both notations but to a lesser…

A fourth-order box method for solving the boundary layer equations

NASA Technical Reports Server (NTRS)

Wornom, S. F.

1977-01-01

A fourth order box method for calculating high accuracy numerical solutions to parabolic, partial differential equations in two variables or ordinary differential equations is presented. The method is the natural extension of the second order Keller Box scheme to fourth order and is demonstrated with application to the incompressible, laminar and turbulent boundary layer equations. Numerical results for high accuracy test cases show the method to be significantly faster than other higher order and second order methods.

Differences in Arithmetic Performance between Chinese and German Children Are Accompanied by Differences in Processing of Symbolic Numerical Magnitude

PubMed Central

Lonnemann, Jan; Linkersdörfer, Janosch; Hasselhorn, Marcus; Lindberg, Sven

2016-01-01

Symbolic numerical magnitude processing skills are assumed to be fundamental to arithmetic learning. It is, however, still an open question whether better arithmetic skills are reflected in symbolic numerical magnitude processing skills. To address this issue, Chinese and German third graders were compared regarding their performance in arithmetic tasks and in a symbolic numerical magnitude comparison task. Chinese children performed better in the arithmetic tasks and were faster in deciding which one of two Arabic numbers was numerically larger. The group difference in symbolic numerical magnitude processing was fully mediated by the performance in arithmetic tasks. We assume that a higher degree of familiarity with arithmetic in Chinese compared to German children leads to a higher speed of retrieving symbolic numerical magnitude knowledge. PMID:27630606

A study on the behaviour of high-order flux reconstruction method with different low-dissipation numerical fluxes for large eddy simulation

NASA Astrophysics Data System (ADS)

Boxi, Lin; Chao, Yan; Shusheng, Chen

2017-10-01

This work focuses on the numerical dissipation features of high-order flux reconstruction (FR) method combined with different numerical fluxes in turbulence flows. The famous Roe and AUSM+ numerical fluxes together with their corresponding low-dissipation enhanced versions (LMRoe, SLAU2) and higher resolution variants (HR-LMRoe, HR-SLAU2) are incorporated into FR framework, and the dissipation interplay of these combinations is investigated in implicit large eddy simulation. The numerical dissipation stemming from these convective numerical fluxes is quantified by simulating the inviscid Gresho vortex, the transitional Taylor-Green vortex and the homogenous decaying isotropic turbulence. The results suggest that low-dissipation enhanced versions are preferential both in high-order and low-order cases to their original forms, while the use of HR-SLAU2 has marginal improvements and the HR-LMRoe leads to degenerated solution with high-order. In high-order the effects of numerical fluxes are reduced, and their viscosity may not be dissipative enough to provide physically consistent turbulence when under-resolved.

Numerical discretization-based estimation methods for ordinary differential equation models via penalized spline smoothing with applications in biomedical research.

PubMed

Wu, Hulin; Xue, Hongqi; Kumar, Arun

2012-06-01

Differential equations are extensively used for modeling dynamics of physical processes in many scientific fields such as engineering, physics, and biomedical sciences. Parameter estimation of differential equation models is a challenging problem because of high computational cost and high-dimensional parameter space. In this article, we propose a novel class of methods for estimating parameters in ordinary differential equation (ODE) models, which is motivated by HIV dynamics modeling. The new methods exploit the form of numerical discretization algorithms for an ODE solver to formulate estimating equations. First, a penalized-spline approach is employed to estimate the state variables and the estimated state variables are then plugged in a discretization formula of an ODE solver to obtain the ODE parameter estimates via a regression approach. We consider three different order of discretization methods, Euler's method, trapezoidal rule, and Runge-Kutta method. A higher-order numerical algorithm reduces numerical error in the approximation of the derivative, which produces a more accurate estimate, but its computational cost is higher. To balance the computational cost and estimation accuracy, we demonstrate, via simulation studies, that the trapezoidal discretization-based estimate is the best and is recommended for practical use. The asymptotic properties for the proposed numerical discretization-based estimators are established. Comparisons between the proposed methods and existing methods show a clear benefit of the proposed methods in regards to the trade-off between computational cost and estimation accuracy. We apply the proposed methods t an HIV study to further illustrate the usefulness of the proposed approaches. © 2012, The International Biometric Society.

Resonant radiation from oscillating higher order solitons

DOE PAGES

Driben, R.; Yulin, A. V.; Efimov, A.

2015-07-15

We present radiation mechanism exhibited by a higher order soliton. In a course of its evolution the higher-order soliton emits polychromatic radiation resulting in formation of multipeak frequency comb-like spectral band. Moreover, the shape and spectral position of this band can be effectively controlled by the relative strength of the third order dispersion. An analytical description is corroborated by numerical simulations. It is also shown that for longer pulses the described effect persists also under the action of higher order perturbations such as Raman and self-steepening.

Modeling Pulse Transmission in the Monterey Bay Using Parabolic Equation Methods

DTIC Science & Technology

1991-12-01

Collins 9-13 was chosen for this purpose due its energy conservation scheme , and its ability to efficiently incorporate higher order terms in its...pressure field generated by the PE model into normal modes. Additionally, this process provides increased physical understanding of mode coupling and...separation of variables (i.e. normal modes or fast field), as well as pure numerical schemes such as the parabolic equation methods, can be used. However, as

Formal Solutions for Polarized Radiative Transfer. II. High-order Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Janett, Gioele; Steiner, Oskar; Belluzzi, Luca, E-mail: gioele.janett@irsol.ch

When integrating the radiative transfer equation for polarized light, the necessity of high-order numerical methods is well known. In fact, well-performing high-order formal solvers enable higher accuracy and the use of coarser spatial grids. Aiming to provide a clear comparison between formal solvers, this work presents different high-order numerical schemes and applies the systematic analysis proposed by Janett et al., emphasizing their advantages and drawbacks in terms of order of accuracy, stability, and computational cost.

Higher order derivatives of R-Jacobi polynomials

NASA Astrophysics Data System (ADS)

Das, Sourav; Swaminathan, A.

2016-06-01

In this work, the R-Jacobi polynomials defined on the nonnegative real axis related to F-distribution are considered. Using their Sturm-Liouville system higher order derivatives are constructed. Orthogonality property of these higher ordered R-Jacobi polynomials are obtained besides their normal form, self-adjoint form and hypergeometric representation. Interesting results on the Interpolation formula and Gaussian quadrature formulae are obtained with numerical examples.

Influence of coatings on the thermal and mechanical processes at insulating glass units

NASA Astrophysics Data System (ADS)

Penkova, Nina; Krumov, Kalin; Surleva, Andriana; Geshkova, Zlatka

2017-09-01

Different coatings on structural glass are used in the advances transparent facades and window systems in order to increase the thermal performance of the glass units and to regulate their optical properties. Coated glass has a higher absorptance in the solar spectrum which leads to correspondent higher temperature in the presence of solar load compared to the uncoated one. That process results in higher climatic loads at the insulating glass units (IGU) and in thermal stresses in the coated glass elements. Temperature fields and gradients in glass panes and climatic loads at IGU in window systems are estimated at different coating of glazed system. The study is implemented by numerical simulation of conjugate heat transfer in the window systems at summer time and presence of solar irradiation, as well as during winter night time.

Non-robust numerical simulations of analogue extension experiments

NASA Astrophysics Data System (ADS)

Naliboff, John; Buiter, Susanne

2016-04-01

Numerical and analogue models of lithospheric deformation provide significant insight into the tectonic processes that lead to specific structural and geophysical observations. As these two types of models contain distinct assumptions and tradeoffs, investigations drawing conclusions from both can reveal robust links between first-order processes and observations. Recent studies have focused on detailed comparisons between numerical and analogue experiments in both compressional and extensional tectonics, sometimes involving multiple lithospheric deformation codes and analogue setups. While such comparisons often show good agreement on first-order deformation styles, results frequently diverge on second-order structures, such as shear zone dip angles or spacing, and in certain cases even on first-order structures. Here, we present finite-element experiments that are designed to directly reproduce analogue "sandbox" extension experiments at the cm-scale. We use material properties and boundary conditions that are directly taken from analogue experiments and use a Drucker-Prager failure model to simulate shear zone formation in sand. We find that our numerical experiments are highly sensitive to numerous numerical parameters. For example, changes to the numerical resolution, velocity convergence parameters and elemental viscosity averaging commonly produce significant changes in first- and second-order structures accommodating deformation. The sensitivity of the numerical simulations to small parameter changes likely reflects a number of factors, including, but not limited to, high angles of internal friction assigned to sand, complex, unknown interactions between the brittle sand (used as an upper crust equivalent) and viscous silicone (lower crust), highly non-linear strain weakening processes and poor constraints on the cohesion of sand. Our numerical-analogue comparison is hampered by (a) an incomplete knowledge of the fine details of sand failure and sand properties, and (b) likely limitations to the use of a continuum Drucker-Prager model for representing shear zone formation in sand. In some cases our numerical experiments provide reasonable fits to first-order structures observed in the analogue experiments, but the numerical sensitivity to small parameter variations leads us to conclude that the numerical experiments are not robust.

A third-order computational method for numerical fluxes to guarantee nonnegative difference coefficients for advection-diffusion equations in a semi-conservative form

NASA Astrophysics Data System (ADS)

Sakai, K.; Watabe, D.; Minamidani, T.; Zhang, G. S.

2012-10-01

According to Godunov theorem for numerical calculations of advection equations, there exist no higher-order schemes with constant positive difference coefficients in a family of polynomial schemes with an accuracy exceeding the first-order. We propose a third-order computational scheme for numerical fluxes to guarantee the non-negative difference coefficients of resulting finite difference equations for advection-diffusion equations in a semi-conservative form, in which there exist two kinds of numerical fluxes at a cell surface and these two fluxes are not always coincident in non-uniform velocity fields. The present scheme is optimized so as to minimize truncation errors for the numerical fluxes while fulfilling the positivity condition of the difference coefficients which are variable depending on the local Courant number and diffusion number. The feature of the present optimized scheme consists in keeping the third-order accuracy anywhere without any numerical flux limiter. We extend the present method into multi-dimensional equations. Numerical experiments for advection-diffusion equations showed nonoscillatory solutions.

Computation of rapidly varied unsteady, free-surface flow

USGS Publications Warehouse

Basco, D.R.

1987-01-01

Many unsteady flows in hydraulics occur with relatively large gradients in free surface profiles. The assumption of hydrostatic pressure distribution with depth is no longer valid. These are rapidly-varied unsteady flows (RVF) of classical hydraulics and also encompass short wave propagation of coastal hydraulics. The purpose of this report is to present an introductory review of the Boussinnesq-type differential equations that describe these flows and to discuss methods for their numerical integration. On variable slopes and for large scale (finite-amplitude) disturbances, three independent derivational methods all gave differences in the motion equation for higher order terms. The importance of these higher-order terms for riverine applications must be determined by numerical experiments. Care must be taken in selection of the appropriate finite-difference scheme to minimize truncation error effects and the possibility of diverging (double mode) numerical solutions. It is recommended that practical hydraulics cases be established and tested numerically to demonstrate the order of differences in solution with those obtained from the long wave equations of St. Venant. (USGS)

Time-Accurate Local Time Stepping and High-Order Time CESE Methods for Multi-Dimensional Flows Using Unstructured Meshes

NASA Technical Reports Server (NTRS)

Chang, Chau-Lyan; Venkatachari, Balaji Shankar; Cheng, Gary

2013-01-01

With the wide availability of affordable multiple-core parallel supercomputers, next generation numerical simulations of flow physics are being focused on unsteady computations for problems involving multiple time scales and multiple physics. These simulations require higher solution accuracy than most algorithms and computational fluid dynamics codes currently available. This paper focuses on the developmental effort for high-fidelity multi-dimensional, unstructured-mesh flow solvers using the space-time conservation element, solution element (CESE) framework. Two approaches have been investigated in this research in order to provide high-accuracy, cross-cutting numerical simulations for a variety of flow regimes: 1) time-accurate local time stepping and 2) highorder CESE method. The first approach utilizes consistent numerical formulations in the space-time flux integration to preserve temporal conservation across the cells with different marching time steps. Such approach relieves the stringent time step constraint associated with the smallest time step in the computational domain while preserving temporal accuracy for all the cells. For flows involving multiple scales, both numerical accuracy and efficiency can be significantly enhanced. The second approach extends the current CESE solver to higher-order accuracy. Unlike other existing explicit high-order methods for unstructured meshes, the CESE framework maintains a CFL condition of one for arbitrarily high-order formulations while retaining the same compact stencil as its second-order counterpart. For large-scale unsteady computations, this feature substantially enhances numerical efficiency. Numerical formulations and validations using benchmark problems are discussed in this paper along with realistic examples.

The application of the mesh-free method in the numerical simulations of the higher-order continuum structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yuzhou, E-mail: yuzhousun@126.com; Chen, Gensheng; Li, Dongxia

2016-06-08

This paper attempts to study the application of mesh-free method in the numerical simulations of the higher-order continuum structures. A high-order bending beam considers the effect of the third-order derivative of deflections, and can be viewed as a one-dimensional higher-order continuum structure. The moving least-squares method is used to construct the shape function with the high-order continuum property, the curvature and the third-order derivative of deflections are directly interpolated with nodal variables and the second- and third-order derivative of the shape function, and the mesh-free computational scheme is establish for beams. The coupled stress theory is introduced to describe themore » special constitutive response of the layered rock mass in which the bending effect of thin layer is considered. The strain and the curvature are directly interpolated with the nodal variables, and the mesh-free method is established for the layered rock mass. The good computational efficiency is achieved based on the developed mesh-free method, and some key issues are discussed.« less

Numerical Order Processing in Children: From Reversing the Distance-Effect to Predicting Arithmetic

ERIC Educational Resources Information Center

Lyons, Ian M.; Ansari, Daniel

2015-01-01

Recent work has demonstrated that how we process the relative order--ordinality--of numbers may be key to understanding how we represent numbers symbolically, and has proven to be a robust predictor of more sophisticated math skills in both children and adults. However, it remains unclear whether numerical ordinality is primarily a by-product of…

A simplified parsimonious higher order multivariate Markov chain model with new convergence condition

NASA Astrophysics Data System (ADS)

Wang, Chao; Yang, Chuan-sheng

2017-09-01

In this paper, we present a simplified parsimonious higher-order multivariate Markov chain model with new convergence condition. (TPHOMMCM-NCC). Moreover, estimation method of the parameters in TPHOMMCM-NCC is give. Numerical experiments illustrate the effectiveness of TPHOMMCM-NCC.

NUMERICAL SIMULATIONS OF CORONAL HEATING THROUGH FOOTPOINT BRAIDING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansteen, V.; Pontieu, B. De; Carlsson, M.

2015-10-01

Advanced three-dimensional (3D) radiative MHD simulations now reproduce many properties of the outer solar atmosphere. When including a domain from the convection zone into the corona, a hot chromosphere and corona are self-consistently maintained. Here we study two realistic models, with different simulated areas, magnetic field strength and topology, and numerical resolution. These are compared in order to characterize the heating in the 3D-MHD simulations which self-consistently maintains the structure of the atmosphere. We analyze the heating at both large and small scales and find that heating is episodic and highly structured in space, but occurs along loop-shaped structures, andmore » moves along with the magnetic field. On large scales we find that the heating per particle is maximal near the transition region and that widely distributed opposite-polarity field in the photosphere leads to a greater heating scale height in the corona. On smaller scales, heating is concentrated in current sheets, the thicknesses of which are set by the numerical resolution. Some current sheets fragment in time, this process occurring more readily in the higher-resolution model leading to spatially highly intermittent heating. The large-scale heating structures are found to fade in less than about five minutes, while the smaller, local, heating shows timescales of the order of two minutes in one model and one minutes in the other, higher-resolution, model.« less

The analysis of harmonic generation coefficients in the ablative Rayleigh-Taylor instability

NASA Astrophysics Data System (ADS)

Lu, Yan; Fan, Zhengfeng; Lu, Xinpei; Ye, Wenhua; Zou, Changlin; Zhang, Ziyun; Zhang, Wen

2017-10-01

In this research, we use the numerical simulation method to investigate the generation coefficients of the first three harmonics and the zeroth harmonic in the Ablative Rayleigh-Taylor Instability. It is shown that the interface shifts to the low temperature side during the ablation process. In consideration of the third-order perturbation theory, the first three harmonic amplitudes of the weakly nonlinear regime are calculated and then the harmonic generation coefficients are obtained by curve fitting. The simulation results show that the harmonic generation coefficients changed with time and wavelength. Using the higher-order perturbation theory, we find that more and more harmonics are generated in the later weakly nonlinear stage, which is caused by the negative feedback of the later higher harmonics. Furthermore, extending the third-order theory to the fifth-order theory, we find that the second and the third harmonics coefficients linearly depend on the wavelength, while the feedback coefficients are almost constant. Further analysis also shows that when the fifth-order theory is considered, the normalized effective amplitudes of second and third harmonics can reach about 25%-40%, which are only 15%-25% in the frame of the previous third-order theory. Therefore, the third order perturbation theory is needed to be modified by the higher-order theory when ηL reaches about 20% of the perturbation wavelength.

Numerical modeling of higher order magnetic moments in UXO discrimination

USGS Publications Warehouse

Sanchez, V.; Yaoguo, L.; Nabighian, M.N.; Wright, D.L.

2008-01-01

The surface magnetic anomaly observed in unexploded ordnance (UXO) clearance is mainly dipolar, and consequently, the dipole is the only magnetic moment regularly recovered in UXO discrimination. The dipole moment contains information about the intensity of magnetization but lacks information about the shape of the target. In contrast, higher order moments, such as quadrupole and octupole, encode asymmetry properties of the magnetization distribution within the buried targets. In order to improve our understanding of magnetization distribution within UXO and non-UXO objects and to show its potential utility in UXO clearance, we present a numerical modeling study of UXO and related metallic objects. The tool for the modeling is a nonlinear integral equation describing magnetization within isolated compact objects of high susceptibility. A solution for magnetization distribution then allows us to compute the magnetic multipole moments of the object, analyze their relationships, and provide a depiction of the anomaly produced by different moments within the object. Our modeling results show the presence of significant higher order moments for more asymmetric objects, and the fields of these higher order moments are well above the noise level of magnetic gradient data. The contribution from higher order moments may provide a practical tool for improved UXO discrimination. ?? 2008 IEEE.

DNS of Flows over Periodic Hills using a Discontinuous-Galerkin Spectral-Element Method

NASA Technical Reports Server (NTRS)

Diosady, Laslo T.; Murman, Scott M.

2014-01-01

Direct numerical simulation (DNS) of turbulent compressible flows is performed using a higher-order space-time discontinuous-Galerkin finite-element method. The numerical scheme is validated by performing DNS of the evolution of the Taylor-Green vortex and turbulent flow in a channel. The higher-order method is shown to provide increased accuracy relative to low-order methods at a given number of degrees of freedom. The turbulent flow over a periodic array of hills in a channel is simulated at Reynolds number 10,595 using an 8th-order scheme in space and a 4th-order scheme in time. These results are validated against previous large eddy simulation (LES) results. A preliminary analysis provides insight into how these detailed simulations can be used to improve Reynoldsaveraged Navier-Stokes (RANS) modeling

Modelling and simulation of “Free Cooling” process applied to building construction

NASA Astrophysics Data System (ADS)

Ousegui, A.; Asbik, M.

2018-05-01

Thermal energy storage systems (TES), using phase change material (PCM) in building walls, consists a hot topic within the research community currently. In the present work, a numerical model is developed to simulate free cooling of air-PCM heat exchanger in both charging and discharging steps. The studied case is taken from experimental work. The domain consists in two parallel plates made of Paraffin as PCM, separate by a gap where air circulates. The flow and temperature can be adjusted. The goal is to calculate the temperature of the air at the outlet, in order to analyse the performance of the device. A good agreement was founded between experimental and numerical results. The analysis of the influence of the flow rate on the efficiency of the process confirms a previous works, that the heating flow rate should be higher than cooling one.

Numerical solution of transport equation for applications in environmental hydraulics and hydrology

NASA Astrophysics Data System (ADS)

Rashidul Islam, M.; Hanif Chaudhry, M.

1997-04-01

The advective term in the one-dimensional transport equation, when numerically discretized, produces artificial diffusion. To minimize such artificial diffusion, which vanishes only for Courant number equal to unity, transport owing to advection has been modeled separately. The numerical solution of the advection equation for a Gaussian initial distribution is well established; however, large oscillations are observed when applied to an initial distribution with sleep gradients, such as trapezoidal distribution of a constituent or propagation of mass from a continuous input. In this study, the application of seven finite-difference schemes and one polynomial interpolation scheme is investigated to solve the transport equation for both Gaussian and non-Gaussian (trapezoidal) initial distributions. The results obtained from the numerical schemes are compared with the exact solutions. A constant advective velocity is assumed throughout the transport process. For a Gaussian distribution initial condition, all eight schemes give excellent results, except the Lax scheme which is diffusive. In application to the trapezoidal initial distribution, explicit finite-difference schemes prove to be superior to implicit finite-difference schemes because the latter produce large numerical oscillations near the steep gradients. The Warming-Kutler-Lomax (WKL) explicit scheme is found to be better among this group. The Hermite polynomial interpolation scheme yields the best result for a trapezoidal distribution among all eight schemes investigated. The second-order accurate schemes are sufficiently accurate for most practical problems, but the solution of unusual problems (concentration with steep gradient) requires the application of higher-order (e.g. third- and fourth-order) accurate schemes.

Higher-Order Compact Schemes for Numerical Simulation of Incompressible Flows

NASA Technical Reports Server (NTRS)

Wilson, Robert V.; Demuren, Ayodeji O.; Carpenter, Mark

1998-01-01

A higher order accurate numerical procedure has been developed for solving incompressible Navier-Stokes equations for 2D or 3D fluid flow problems. It is based on low-storage Runge-Kutta schemes for temporal discretization and fourth and sixth order compact finite-difference schemes for spatial discretization. The particular difficulty of satisfying the divergence-free velocity field required in incompressible fluid flow is resolved by solving a Poisson equation for pressure. It is demonstrated that for consistent global accuracy, it is necessary to employ the same order of accuracy in the discretization of the Poisson equation. Special care is also required to achieve the formal temporal accuracy of the Runge-Kutta schemes. The accuracy of the present procedure is demonstrated by application to several pertinent benchmark problems.

Lumley's PODT definition of large eddies and a trio of numerical procedures. [Proper Orthogonal Decomposition Theorem

NASA Technical Reports Server (NTRS)

Payne, Fred R.

1992-01-01

Lumley's 1967 Moscow paper provided, for the first time, a completely rational definition of the physically-useful term 'large eddy', popular for a half-century. The numerical procedures based upon his results are: (1) PODT (Proper Orthogonal Decomposition Theorem), which extracts the Large Eddy structure of stochastic processes from physical or computer simulation two-point covariances, and 2) LEIM (Large-Eddy Interaction Model), a predictive scheme for the dynamical large eddies based upon higher order turbulence modeling. Earlier Lumley's work (1964) forms the basis for the final member of the triad of numerical procedures: this predicts the global neutral modes of turbulence which have surprising agreement with both structural eigenmodes and those obtained from the dynamical equations. The ultimate goal of improved engineering design tools for turbulence may be near at hand, partly due to the power and storage of 'supermicrocomputer' workstations finally becoming adequate for the demanding numerics of these procedures.

Polyhedral meshing in numerical analysis of conjugate heat transfer

NASA Astrophysics Data System (ADS)

Sosnowski, Marcin; Krzywanski, Jaroslaw; Grabowska, Karolina; Gnatowska, Renata

2018-06-01

Computational methods have been widely applied in conjugate heat transfer analysis. The very first and crucial step in such research is the meshing process which consists in dividing the analysed geometry into numerous small control volumes (cells). In Computational Fluid Dynamics (CFD) applications it is desirable to use the hexahedral cells as the resulting mesh is characterized by low numerical diffusion. Unfortunately generating such mesh can be a very time-consuming task and in case of complicated geometry - it may not be possible to generate cells of good quality. Therefore tetrahedral cells have been implemented into commercial pre-processors. Their advantage is the ease of its generation even in case of very complex geometry. On the other hand tetrahedrons cannot be stretched excessively without decreasing the mesh quality factor, so significantly larger number of cells has to be used in comparison to hexahedral mesh in order to achieve a reasonable accuracy. Moreover the numerical diffusion of tetrahedral elements is significantly higher. Therefore the polyhedral cells are proposed within the paper in order to combine the advantages of hexahedrons (low numerical diffusion resulting in accurate solution) and tetrahedrons (rapid semi-automatic generation) as well as to overcome the disadvantages of both the above mentioned mesh types. The major benefit of polyhedral mesh is that each individual cell has many neighbours, so gradients can be well approximated. Polyhedrons are also less sensitive to stretching than tetrahedrons which results in better mesh quality leading to improved numerical stability of the model. In addition, numerical diffusion is reduced due to mass exchange over numerous faces. This leads to a more accurate solution achieved with a lower cell count. Therefore detailed comparison of numerical modelling results concerning conjugate heat transfer using tetrahedral and polyhedral meshes is presented in the paper.

A fast isogeometric BEM for the three dimensional Laplace- and Helmholtz problems

NASA Astrophysics Data System (ADS)

Dölz, Jürgen; Harbrecht, Helmut; Kurz, Stefan; Schöps, Sebastian; Wolf, Felix

2018-03-01

We present an indirect higher order boundary element method utilising NURBS mappings for exact geometry representation and an interpolation-based fast multipole method for compression and reduction of computational complexity, to counteract the problems arising due to the dense matrices produced by boundary element methods. By solving Laplace and Helmholtz problems via a single layer approach we show, through a series of numerical examples suitable for easy comparison with other numerical schemes, that one can indeed achieve extremely high rates of convergence of the pointwise potential through the utilisation of higher order B-spline-based ansatz functions.

A higher-order split-step Fourier parabolic-equation sound propagation solution scheme.

PubMed

Lin, Ying-Tsong; Duda, Timothy F

2012-08-01

A three-dimensional Cartesian parabolic-equation model with a higher-order approximation to the square-root Helmholtz operator is presented for simulating underwater sound propagation in ocean waveguides. The higher-order approximation includes cross terms with the free-space square-root Helmholtz operator and the medium phase speed anomaly. It can be implemented with a split-step Fourier algorithm to solve for sound pressure in the model. Two idealized ocean waveguide examples are presented to demonstrate the performance of this numerical technique.

Efficient Low Dissipative High Order Schemes for Multiscale MHD Flows

NASA Technical Reports Server (NTRS)

Sjoegreen, Bjoern; Yee, Helen C.; Mansour, Nagi (Technical Monitor)

2002-01-01

Accurate numerical simulations of complex multiscale compressible viscous flows, especially high speed turbulence combustion and acoustics, demand high order schemes with adaptive numerical dissipation controls. Standard high resolution shock-capturing methods are too dissipative to capture the small scales and/or long-time wave propagations without extreme grid refinements and small time steps. An integrated approach for the control of numerical dissipation in high order schemes for the compressible Euler and Navier-Stokes equations has been developed and verified by the authors and collaborators. These schemes are suitable for the problems in question. Basically, the scheme consists of sixth-order or higher non-dissipative spatial difference operators as the base scheme. To control the amount of numerical dissipation, multiresolution wavelets are used as sensors to adaptively limit the amount and to aid the selection and/or blending of the appropriate types of numerical dissipation to be used. Magnetohydrodynamics (MHD) waves play a key role in drag reduction in highly maneuverable high speed combat aircraft, in space weather forecasting, and in the understanding of the dynamics of the evolution of our solar system and the main sequence stars. Although there exist a few well-studied second and third-order high-resolution shock-capturing schemes for the MHD in the literature, these schemes are too diffusive and not practical for turbulence/combustion MHD flows. On the other hand, extension of higher than third-order high-resolution schemes to the MHD system of equations is not straightforward. Unlike the hydrodynamic equations, the inviscid MHD system is non-strictly hyperbolic with non-convex fluxes. The wave structures and shock types are different from their hydrodynamic counterparts. Many of the non-traditional hydrodynamic shocks are not fully understood. Consequently, reliable and highly accurate numerical schemes for multiscale MHD equations pose a great challenge to algorithm development. In addition, controlling the numerical error of the divergence free condition of the magnetic fields for high order methods has been a stumbling block. Lower order methods are not practical for the astrophysical problems in question. We propose to extend our hydrodynamics schemes to the MHD equations with several desired properties over commonly used MHD schemes.

Double pendulum model for a tennis stroke including a collision process

NASA Astrophysics Data System (ADS)

Youn, Sun-Hyun

2015-10-01

By means of adding a collision process between the ball and racket in the double pendulum model, we analyzed the tennis stroke. The ball and the racket system may be accelerated during the collision time; thus, the speed of the rebound ball does not simply depend on the angular velocity of the racket. A higher angular velocity sometimes gives a lower rebound ball speed. We numerically showed that the proper time-lagged racket rotation increased the speed of the rebound ball by 20%. We also showed that the elbow should move in the proper direction in order to add the angular velocity of the racket.

Implications of Sea Level Rise on Coastal Flood Hazards

NASA Astrophysics Data System (ADS)

Roeber, V.; Li, N.; Cheung, K.; Lane, P.; Evans, R. L.; Donnelly, J. P.; Ashton, A. D.

2012-12-01

Recent global and local projections suggest the sea level will be on the order of 1 m or higher than the current level by the end of the century. Coastal communities and ecosystems in low-lying areas are vulnerable to impacts resulting from hurricane or large swell events in combination with sea-level rise. This study presents the implementation and results of an integrated numerical modeling package to delineate coastal inundation due to storm landfalls at future sea levels. The modeling package utilizes a suite of numerical models to capture both large-scale phenomena in the open ocean and small-scale processes in coastal areas. It contains four components to simulate (1) meteorological conditions, (2) astronomical tides and surge, (3) wave generation, propagation, and nearshore transformation, and (4) surf-zone processes and inundation onto dry land associated with a storm event. Important aspects of this package are the two-way coupling of a spectral wave model and a storm surge model as well as a detailed representation of surf and swash zone dynamics by a higher-order Boussinesq-type wave model. The package was validated with field data from Hurricane Ivan of 2005 on the US Gulf coast and applied to tropical and extratropical storm scenarios respectively at Eglin, Florida and Camp Lejeune, North Carolina. The results show a nonlinear increase of storm surge level and nearshore wave energy with a rising sea level. The exacerbated flood hazard can have major consequences for coastal communities with respect to erosion and damage to infrastructure.

Scientific knowledge and modern prospecting

USGS Publications Warehouse

Neuerburg, G.J.

1985-01-01

Modern prospecting is the systematic search for specified and generally ill-exposed components of the Earth's crust known as ore. This prospecting depends entirely on reliable, or scientific knowledge for guidance and for recognition of the search objects. Improvement in prospecting results from additions and refinements to scientific knowledge. Scientific knowledge is an ordered distillation of observations too numerous and too complex in themselves for easy understanding and for effective management. The ordering of these observations is accomplished by an evolutionary hierarchy of abstractions. These abstractions employ simplified descriptions consisting of characterization by selected properties, sampling to represent much larger parts of a phenomenon, generalized mappings of patterns of geometrical and numerical relations among properties, and explanation (theory) of these patterns as functional relations among the selected properties. Each abstraction is predicated on the mode of abstraction anticipated for the next higher level, so that research is a deductive process in which the highest level, theory, is indispensible for the growth and refinement of scientific knowledge, and therefore of prospecting methodology. ?? 1985 Springer-Verlag.

Insuring wind energy production

NASA Astrophysics Data System (ADS)

D'Amico, Guglielmo; Petroni, Filippo; Prattico, Flavio

2017-02-01

This paper presents an insurance contract that the supplier of wind energy may subscribe in order to immunize the production of electricity against the volatility of the wind speed process. The other party of the contract may be any dispatchable energy producer, like gas turbine or hydroelectric generator, which can supply the required energy in case of little or no wind. The adoption of a stochastic wind speed model allows the computation of the fair premium that the wind power supplier has to pay in order to hedge the risk of inadequate output of electricity at any time. Recursive type equations are obtained for the prospective mathematical reserves of the insurance contract and for their higher order moments. The model and the validity of the results are illustrated through a numerical example.

Electrophysiological Correlates of Non-Symbolic Numerical Magnitude Processing in Children: Joining the Dots

ERIC Educational Resources Information Center

Heine, Angela; Tamm, Sascha; Wissmann, Jacqueline; Jacobs, Arthur M.

2011-01-01

Whether and in what way enumeration processes differ for small and large sets of objects is still a matter of debate. In order to shed light on this issue, EEG data were obtained from 60 normally developing elementary school children. Adopting a standard non-symbolic numerical comparison paradigm allowed us to manipulate numerical distance between…

Thermally and electrically controllable multiple high harmonics generation by harmonically driven quasi-two-dimensional electron gas

NASA Astrophysics Data System (ADS)

Maglevanny, I. I.; Smolar, V. A.; Karyakina, T. I.

2018-06-01

In this paper, we consider the activation processes in nonlinear meta-stable system based on a lateral (quasi-two-dimensional) superlattice and study the dynamics of such a system externally driven by a harmonic force. The internal control parameters are the longitudinal applied electric field and the sample temperature. The spontaneous transverse electric field is considered as an order parameter. The forced violations of order parameter are considered as a response of a system to periodic driving. We investigate the cooperative effects of self-organization and high harmonic forcing from the viewpoint of catastrophe theory and show the possibility of generation of third and higher odd harmonics in output signal that lead to distortion of its wave front. A higher harmonics detection strategy is further proposed and explained in detail by exploring the influences of system parameters on the response output of the system that are discussed through numerical simulations.

High order parallel numerical schemes for solving incompressible flows

NASA Technical Reports Server (NTRS)

Lin, Avi; Milner, Edward J.; Liou, May-Fun; Belch, Richard A.

1992-01-01

The use of parallel computers for numerically solving flow fields has gained much importance in recent years. This paper introduces a new high order numerical scheme for computational fluid dynamics (CFD) specifically designed for parallel computational environments. A distributed MIMD system gives the flexibility of treating different elements of the governing equations with totally different numerical schemes in different regions of the flow field. The parallel decomposition of the governing operator to be solved is the primary parallel split. The primary parallel split was studied using a hypercube like architecture having clusters of shared memory processors at each node. The approach is demonstrated using examples of simple steady state incompressible flows. Future studies should investigate the secondary split because, depending on the numerical scheme that each of the processors applies and the nature of the flow in the specific subdomain, it may be possible for a processor to seek better, or higher order, schemes for its particular subcase.

Exploiting Superconvergence in Discontinuous Galerkin Methods for Improved Time-Stepping and Visualization

DTIC Science & Technology

2016-09-08

Accuracy Conserving (SIAC) filter when applied to nonuniform meshes; 2) Theoretically and numerical demonstration of the 2k+1 order accuracy of the SIAC...Establishing a more theoretical and numerical understanding of a computationally efficient scaling for the SIAC filter for nonuniform meshes [7]; 2...Li, “SIAC Filtering of DG Methods – Boundary and Nonuniform Mesh”, International Conference on Spectral and Higher Order Methods (ICOSAHOM

Improving the seismic small-scale modelling by comparison with numerical methods

NASA Astrophysics Data System (ADS)

Pageot, Damien; Leparoux, Donatienne; Le Feuvre, Mathieu; Durand, Olivier; Côte, Philippe; Capdeville, Yann

2017-10-01

The potential of experimental seismic modelling at reduced scale provides an intermediate step between numerical tests and geophysical campaigns on field sites. Recent technologies such as laser interferometers offer the opportunity to get data without any coupling effects. This kind of device is used in the Mesures Ultrasonores Sans Contact (MUSC) measurement bench for which an automated support system makes possible to generate multisource and multireceivers seismic data at laboratory scale. Experimental seismic modelling would become a great tool providing a value-added stage in the imaging process validation if (1) the experimental measurement chain is perfectly mastered, and thus if the experimental data are perfectly reproducible with a numerical tool, as well as if (2) the effective source is reproducible along the measurement setup. These aspects for a quantitative validation concerning devices with piezoelectrical sources and a laser interferometer have not been yet quantitatively studied in published studies. Thus, as a new stage for the experimental modelling approach, these two key issues are tackled in the proposed paper in order to precisely define the quality of the experimental small-scale data provided by the bench MUSC, which are available in the scientific community. These two steps of quantitative validation are dealt apart any imaging techniques in order to offer the opportunity to geophysicists who want to use such data (delivered as free data) of precisely knowing their quality before testing any imaging technique. First, in order to overcome the 2-D-3-D correction usually done in seismic processing when comparing 2-D numerical data with 3-D experimental measurement, we quantitatively refined the comparison between numerical and experimental data by generating accurate experimental line sources, avoiding the necessity of geometrical spreading correction for 3-D point-source data. The comparison with 2-D and 3-D numerical modelling is based on the Spectral Element Method. The approach shows the relevance of building a line source by sampling several source points, except the boundaries effects on later arrival times. Indeed, the experimental results highlight the amplitude feature and the delay equal to π/4 provided by a line source in the same manner than numerical data. In opposite, the 2-D corrections applied on 3-D data showed discrepancies which are higher on experimental data than on numerical ones due to the source wavelet shape and interferences between different arrivals. The experimental results from the approach proposed here show that discrepancies are avoided, especially for the reflected echoes. Concerning the second point aiming to assess the experimental reproducibility of the source, correlation coefficients of recording from a repeated source impact on a homogeneous model are calculated. The quality of the results, that is, higher than 0.98, allow to calculate a mean source wavelet by inversion of a mean data set. Results obtained on a more realistic model simulating clays on limestones, confirmed the reproducibility of the source impact.

Large eddy simulation of turbine wakes using higher-order methods

NASA Astrophysics Data System (ADS)

Deskos, Georgios; Laizet, Sylvain; Piggott, Matthew D.; Sherwin, Spencer

2017-11-01

Large eddy simulations (LES) of a horizontal-axis turbine wake are presented using the well-known actuator line (AL) model. The fluid flow is resolved by employing higher-order numerical schemes on a 3D Cartesian mesh combined with a 2D Domain Decomposition strategy for an efficient use of supercomputers. In order to simulate flows at relatively high Reynolds numbers for a reasonable computational cost, a novel strategy is used to introduce controlled numerical dissipation to a selected range of small scales. The idea is to mimic the contribution of the unresolved small-scales by imposing a targeted numerical dissipation at small scales when evaluating the viscous term of the Navier-Stokes equations. The numerical technique is shown to behave similarly to the traditional eddy viscosity sub-filter scale models such as the classic or the dynamic Smagorinsky models. The results from the simulations are compared to experimental data for a Reynolds number scaled by the diameter equal to ReD =1,000,000 and both the time-averaged stream wise velocity and turbulent kinetic energy (TKE) are showing a good overall agreement. At the end, suggestions for the amount of numerical dissipation required by our approach are made for the particular case of horizontal-axis turbine wakes.

Tensor-product preconditioners for higher-order space-time discontinuous Galerkin methods

NASA Astrophysics Data System (ADS)

Diosady, Laslo T.; Murman, Scott M.

2017-02-01

A space-time discontinuous-Galerkin spectral-element discretization is presented for direct numerical simulation of the compressible Navier-Stokes equations. An efficient solution technique based on a matrix-free Newton-Krylov method is developed in order to overcome the stiffness associated with high solution order. The use of tensor-product basis functions is key to maintaining efficiency at high-order. Efficient preconditioning methods are presented which can take advantage of the tensor-product formulation. A diagonalized Alternating-Direction-Implicit (ADI) scheme is extended to the space-time discontinuous Galerkin discretization. A new preconditioner for the compressible Euler/Navier-Stokes equations based on the fast-diagonalization method is also presented. Numerical results demonstrate the effectiveness of these preconditioners for the direct numerical simulation of subsonic turbulent flows.

Tensor-Product Preconditioners for Higher-Order Space-Time Discontinuous Galerkin Methods

NASA Technical Reports Server (NTRS)

Diosady, Laslo T.; Murman, Scott M.

2016-01-01

space-time discontinuous-Galerkin spectral-element discretization is presented for direct numerical simulation of the compressible Navier-Stokes equat ions. An efficient solution technique based on a matrix-free Newton-Krylov method is developed in order to overcome the stiffness associated with high solution order. The use of tensor-product basis functions is key to maintaining efficiency at high order. Efficient preconditioning methods are presented which can take advantage of the tensor-product formulation. A diagonalized Alternating-Direction-Implicit (ADI) scheme is extended to the space-time discontinuous Galerkin discretization. A new preconditioner for the compressible Euler/Navier-Stokes equations based on the fast-diagonalization method is also presented. Numerical results demonstrate the effectiveness of these preconditioners for the direct numerical simulation of subsonic turbulent flows.

Separating Item and Order Information through Process Dissociation

ERIC Educational Resources Information Center

Nairne, James S.; Kelley, Matthew R.

2004-01-01

In the present paper, we develop and apply a technique, based on the logic of process dissociation, for obtaining numerical estimates of item and order information. Certain variables, such as phonological similarity, are widely believed to produce dissociative effects on item and order retention. However, such beliefs rest on the questionable…

Higher-order automatic differentiation of mathematical functions

NASA Astrophysics Data System (ADS)

Charpentier, Isabelle; Dal Cappello, Claude

2015-04-01

Functions of mathematical physics such as the Bessel functions, the Chebyshev polynomials, the Gauss hypergeometric function and so forth, have practical applications in many scientific domains. On the one hand, differentiation formulas provided in reference books apply to real or complex variables. These do not account for the chain rule. On the other hand, based on the chain rule, the automatic differentiation has become a natural tool in numerical modeling. Nevertheless automatic differentiation tools do not deal with the numerous mathematical functions. This paper describes formulas and provides codes for the higher-order automatic differentiation of mathematical functions. The first method is based on Faà di Bruno's formula that generalizes the chain rule. The second one makes use of the second order differential equation they satisfy. Both methods are exemplified with the aforementioned functions.

FLUX-CORRECTED TRANSPORT TECHNIQUE FOR OPEN CHANNEL FLOW. (R825200)

EPA Science Inventory

In modeling flow in open channels, the traditional finite difference/finite volume schemes become inefficient and warrant special numerical treatment in the presence of shocks and discontinuities. The numerical oscillations that arise by making use of a second- and higher-order s...

Filtering higher-order laser modes using leaky plasma channels

NASA Astrophysics Data System (ADS)

Djordjević, B. Z.; Benedetti, C.; Schroeder, C. B.; Esarey, E.; Leemans, W. P.

2018-01-01

Plasma structures based on leaky channels are proposed to filter higher-order laser mode content. The evolution and propagation of non-Gaussian laser pulses in leaky channels are studied, and it is shown that, for appropriate laser-plasma parameters, the higher-order laser mode content of the pulse may be removed while the fundamental mode remains well-guided. The behavior of multi-mode laser pulses is described analytically and numerically using envelope equations, including the derivation of the leakage coefficients, and compared to particle-in-cell simulations. Laser pulse propagation, with reduced higher-order mode content, improves guiding in parabolic plasma channels, enabling extended interaction lengths for laser-plasma accelerator applications.

Modeling and analysis of multiple scattering of acoustic waves in complex media: application to the trabecular bone.

PubMed

Wojcik, J; Litniewski, J; Nowicki, A

2011-10-01

The integral equations that describe scattering in the media with step-rise changing parameters have been numerically solved for the trabecular bone model. The model consists of several hundred discrete randomly distributed elements. The spectral distribution of scattering coefficients in subsequent orders of scattering has been presented. Calculations were carried on for the ultrasonic frequency ranging from 0.5 to 3 MHz. Evaluation of the contribution of the first, second, and higher scattering orders to total scattering of the ultrasounds in trabecular bone was done. Contrary to the approaches that use the μCT images of trabecular structure to modeling of the ultrasonic wave propagation condition, the 3D numerical model consisting of cylindrical elements mimicking the spatial matrix of trabeculae, was applied. The scattering, due to interconnections between thick trabeculae, usually neglected in trabecular bone models, has been included in calculations when the structure backscatter was evaluated. Influence of the absorption in subsequent orders of scattering is also addressed. Results show that up to 1.5 MHz, the influence of higher scattering orders on the total scattered field characteristic can be neglected while for the higher frequencies, the relatively high amplitude interference peaks in higher scattering orders clearly occur. © 2011 Acoustical Society of America

Ordinality and the nature of symbolic numbers.

PubMed

Lyons, Ian M; Beilock, Sian L

2013-10-23

The view that representations of symbolic and nonsymbolic numbers are closely tied to one another is widespread. However, the link between symbolic and nonsymbolic numbers is almost always inferred from cardinal processing tasks. In the current work, we show that considering ordinality instead points to striking differences between symbolic and nonsymbolic numbers. Human behavioral and neural data show that ordinal processing of symbolic numbers (Are three Indo-Arabic numerals in numerical order?) is distinct from symbolic cardinal processing (Which of two numerals represents the greater quantity?) and nonsymbolic number processing (ordinal and cardinal judgments of dot-arrays). Behaviorally, distance-effects were reversed when assessing ordinality in symbolic numbers, but canonical distance-effects were observed for cardinal judgments of symbolic numbers and all nonsymbolic judgments. At the neural level, symbolic number-ordering was the only numerical task that did not show number-specific activity (greater than control) in the intraparietal sulcus. Only activity in left premotor cortex was specifically associated with symbolic number-ordering. For nonsymbolic numbers, activation in cognitive-control areas during ordinal processing and a high degree of overlap between ordinal and cardinal processing networks indicate that nonsymbolic ordinality is assessed via iterative cardinality judgments. This contrasts with a striking lack of neural overlap between ordinal and cardinal judgments anywhere in the brain for symbolic numbers, suggesting that symbolic number processing varies substantially with computational context. Ordinal processing sheds light on key differences between symbolic and nonsymbolic number processing both behaviorally and in the brain. Ordinality may prove important for understanding the power of representing numbers symbolically.

Low Dissipative High Order Shock-Capturing Methods Using Characteristic-Based Filters

NASA Technical Reports Server (NTRS)

Yee, H. C.; Sandham, N. D.; Djomehri, M. J.

1998-01-01

An approach which closely maintains the non-dissipative nature of classical fourth or higher- order spatial differencing away from shock waves and steep gradient regions while being capable of accurately capturing discontinuities, steep gradient and fine scale turbulent structures in a stable and efficient manner is described. The approach is a generalization of the method of Gustafsson and Oisson and the artificial compression method (ACM) of Harten. Spatially non-dissipative fourth or higher-order compact and non-compact spatial differencings are used as the base schemes. Instead of applying a scalar filter as in Gustafsson and Olsson, an ACM like term is used to signal the appropriate amount of second or third-order TVD or ENO types of characteristic based numerical dissipation. This term acts as a characteristic filter to minimize numerical dissipation for the overall scheme. For time-accurate computations, time discretizations with low dissipation are used. Numerical experiments on 2-D vortical flows, vortex-shock interactions and compressible spatially and temporally evolving mixing layers showed that the proposed schemes have the desired property with only a 10% increase in operations count over standard second-order TVD schemes. Aside from the ability to accurately capture shock-turbulence interaction flows, this approach is also capable of accurately preserving vortex convection. Higher accuracy is achieved with fewer grid points when compared to that of standard second-order TVD or ENO schemes. To demonstrate the applicability of these schemes in sustaining turbulence where shock waves are absent, a simulation of 3-D compressible turbulent channel flow in a small domain is conducted.

Low Dissipative High Order Shock-Capturing Methods using Characteristic-Based Filters

NASA Technical Reports Server (NTRS)

Yee, H. C.; Sandham, N. D.; Djomehri, M. J.

1998-01-01

An approach which closely maintains the non-dissipative nature of classical fourth or higher- order spatial differencing away from shock waves and steep gradient regions while being capable of accurately capturing discontinuities, steep gradient and fine scale turbulent structures in a stable and efficient manner is described. The approach is a generalization of the method of Gustafsson and Olsson and the artificial compression method (ACM) of Harten. Spatially non-dissipative fourth or higher-order compact and non-compact spatial differencings are used as the base schemes. Instead of applying a scalar filter as in Gustafsson and Olsson, an ACM like term is used to signal the appropriate amount of second or third-order TVD or ENO types of characteristic based numerical dissipation. This term acts as a characteristic filter to minimize numerical dissipation for the overall scheme. For time-accurate computations, time discretizations with low dissipation are used. Numerical experiments on 2-D vortical flows, vortex-shock interactions and compressible spatially and temporally evolving mixing layers showed that the proposed schemes have the desired property with only a 10% increase in operations count over standard second-order TVD schemes. Aside from the ability to accurately capture shock-turbulence interaction flows, this approach is also capable of accurately preserving vortex convection. Higher accuracy is achieved with fewer grid points when compared to that of standard second-order TVD or ENO schemes. To demonstrate the applicability of these schemes in sustaining turbulence where shock waves are absent, a simulation of 3-D compressible turbulent channel flow in a small domain is conducted.

Patterns of linguistic and numerical performance in aphasia.

PubMed

Rath, Dajana; Domahs, Frank; Dressel, Katharina; Claros-Salinas, Dolores; Klein, Elise; Willmes, Klaus; Krinzinger, Helga

2015-02-04

Empirical research on the relationship between linguistic and numerical processing revealed inconsistent results for different levels of cognitive processing (e.g., lexical, semantic) as well as different stimulus materials (e.g., Arabic digits, number words, letters, non-number words). Information of dissociation patterns in aphasic patients was used in order to investigate the dissociability of linguistic and numerical processes. The aim of the present prospective study was a comprehensive, specific, and systematic investigation of relationships between linguistic and numerical processing, considering the impact of asemantic vs. semantic processing and the type of material employed (numbers compared to letters vs. words). A sample of aphasic patients (n = 60) was assessed with a battery of linguistic and numerical tasks directly comparable for their cognitive processing levels (e.g., perceptual, morpho-lexical, semantic). Mean performance differences and frequencies of (complementary) dissociations in individual patients revealed the most prominent numerical advantage for asemantic tasks when comparing the processing of numbers vs. letters, whereas the least numerical advantage was found for semantic tasks when comparing the processing of numbers vs. words. Different patient subgroups showing differential dissociation patterns were further analysed and discussed. A comprehensive model of linguistic and numerical processing should take these findings into account.

Dictionary-based image reconstruction for superresolution in integrated circuit imaging.

PubMed

Cilingiroglu, T Berkin; Uyar, Aydan; Tuysuzoglu, Ahmet; Karl, W Clem; Konrad, Janusz; Goldberg, Bennett B; Ünlü, M Selim

2015-06-01

Resolution improvement through signal processing techniques for integrated circuit imaging is becoming more crucial as the rapid decrease in integrated circuit dimensions continues. Although there is a significant effort to push the limits of optical resolution for backside fault analysis through the use of solid immersion lenses, higher order laser beams, and beam apodization, signal processing techniques are required for additional improvement. In this work, we propose a sparse image reconstruction framework which couples overcomplete dictionary-based representation with a physics-based forward model to improve resolution and localization accuracy in high numerical aperture confocal microscopy systems for backside optical integrated circuit analysis. The effectiveness of the framework is demonstrated on experimental data.

Supercritical Nitrogen Processing for the Purification of Reactive Porous Materials

PubMed Central

Stadie, Nicholas P.; Callini, Elsa; Mauron, Philippe; Borgschulte, Andreas; Züttel, Andreas

2015-01-01

Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. Herein, nitrogen is presented as a novel supercritical drying fluid for specialized applications such as in the processing of reactive porous materials, where carbon dioxide and other fluids are not appropriate due to their higher chemical reactivity. Nitrogen exhibits similar physical properties in the near-critical region of its phase diagram as compared to carbon dioxide: a widely tunable density up to ~1 g ml-1, modest critical pressure (3.4 MPa), and small molecular diameter of ~3.6 Å. The key to achieving a high solvation power of nitrogen is to apply a processing temperature in the range of 80-150 K, where the density of nitrogen is an order of magnitude higher than at similar pressures near ambient temperature. The detailed solvation properties of nitrogen, and especially its selectivity, across a wide range of common target species of extraction still require further investigation. Herein we describe a protocol for the supercritical nitrogen processing of porous magnesium borohydride. PMID:26066492

Fractional order PIλ controller synthesis for steam turbine speed governing systems.

PubMed

Chen, Kai; Tang, Rongnian; Li, Chuang; Lu, Junguo

2018-06-01

The current state of the art of fractional order stability theory is hardly to build connection between the time domain analysis and frequency domain synthesis. The existing tuning methodologies for fractional order PI λ D μ are not always satisfy the given gain crossover frequency and phase margin simultaneously. To overcome the drawbacks in the existing synthesis of fractional order controller, the synthesis of optimal fractional order PI λ controller for higher-order process is proposed. According to the specified phase margin, the corresponding upper boundary of gain crossover frequency and stability surface in parameter space are obtained. Sweeping the order parameter over λ∈(0,2), the complete set of stabilizing controller which guarantees both pre-specifying phase frequency characteristic can be collected. Whereafter, the optimal fractional order PI λ controller is applied to the speed governing systems of steam turbine generation units. The numerical simulation and hardware-in-the-loop simulation demonstrate the effectiveness and satisfactory closed-loop performance of obtained fractional order PI λ controller. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

Adaptive angular-velocity Vold-Kalman filter order tracking - Theoretical basis, numerical implementation and parameter investigation

NASA Astrophysics Data System (ADS)

Pan, M.-Ch.; Chu, W.-Ch.; Le, Duc-Do

2016-12-01

The paper presents an alternative Vold-Kalman filter order tracking (VKF_OT) method, i.e. adaptive angular-velocity VKF_OT technique, to extract and characterize order components in an adaptive manner for the condition monitoring and fault diagnosis of rotary machinery. The order/spectral waveforms to be tracked can be recursively solved by using Kalman filter based on the one-step state prediction. The paper comprises theoretical derivation of computation scheme, numerical implementation, and parameter investigation. Comparisons of the adaptive VKF_OT scheme with two other ones are performed through processing synthetic signals of designated order components. Processing parameters such as the weighting factor and the correlation matrix of process noise, and data conditions like the sampling frequency, which influence tracking behavior, are explored. The merits such as adaptive processing nature and computation efficiency brought by the proposed scheme are addressed although the computation was performed in off-line conditions. The proposed scheme can simultaneously extract multiple spectral components, and effectively decouple close and crossing orders associated with multi-axial reference rotating speeds.

Wilson loop's phase transition probed by non-local observable

NASA Astrophysics Data System (ADS)

Li, Hui-Ling; Feng, Zhong-Wen; Yang, Shu-Zheng; Zu, Xiao-Tao

2018-04-01

In order to give further insights into the holographic Van der Waals phase transition, it would be of great interest to investigate the behavior of Wilson loop across the holographic phase transition for a higher dimensional hairy black hole. We offer a possibility to proceed with a numerical calculation in order to discussion on the hairy black hole's phase transition, and show that Wilson loop can serve as a probe to detect a phase structure of the black hole. Furthermore, for a first order phase transition, we calculate numerically the Maxwell's equal area construction; and for a second order phase transition, we also study the critical exponent in order to characterize the Wilson loop's phase transition.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alam, Aftab; Khan, Suffian N.; Smirnov, A. V.

Korringa-Kohn-Rostoker (KKR) Green's function, multiple-scattering theory is an ecient sitecentered, electronic-structure technique for addressing an assembly of N scatterers. Wave-functions are expanded in a spherical-wave basis on each scattering center and indexed up to a maximum orbital and azimuthal number L max = (l,m) max, while scattering matrices, which determine spectral properties, are truncated at L tr = (l,m) tr where phase shifts δl>l tr are negligible. Historically, L max is set equal to L tr, which is correct for large enough L max but not computationally expedient; a better procedure retains higher-order (free-electron and single-site) contributions for L maxmore » > L tr with δl>l tr set to zero [Zhang and Butler, Phys. Rev. B 46, 7433]. We present a numerically ecient and accurate augmented-KKR Green's function formalism that solves the KKR equations by exact matrix inversion [R 3 process with rank N(l tr + 1) 2] and includes higher-L contributions via linear algebra [R 2 process with rank N(l max +1) 2]. Augmented-KKR approach yields properly normalized wave-functions, numerically cheaper basis-set convergence, and a total charge density and electron count that agrees with Lloyd's formula. We apply our formalism to fcc Cu, bcc Fe and L1 0 CoPt, and present the numerical results for accuracy and for the convergence of the total energies, Fermi energies, and magnetic moments versus L max for a given L tr.« less

Regression rate behaviors of HTPB-based propellant combinations for hybrid rocket motor

NASA Astrophysics Data System (ADS)

Sun, Xingliang; Tian, Hui; Li, Yuelong; Yu, Nanjia; Cai, Guobiao

2016-02-01

The purpose of this paper is to characterize the regression rate behavior of hybrid rocket motor propellant combinations, using hydrogen peroxide (HP), gaseous oxygen (GOX), nitrous oxide (N2O) as the oxidizer and hydroxyl-terminated poly-butadiene (HTPB) as the based fuel. In order to complete this research by experiment and simulation, a hybrid rocket motor test system and a numerical simulation model are established. Series of hybrid rocket motor firing tests are conducted burning different propellant combinations, and several of those are used as references for numerical simulations. The numerical simulation model is developed by combining the Navies-Stokes equations with the turbulence model, one-step global reaction model, and solid-gas coupling model. The distribution of regression rate along the axis is determined by applying simulation mode to predict the combustion process and heat transfer inside the hybrid rocket motor. The time-space averaged regression rate has a good agreement between the numerical value and experimental data. The results indicate that the N2O/HTPB and GOX/HTPB propellant combinations have a higher regression rate, since the enhancement effect of latter is significant due to its higher flame temperature. Furthermore, the containing of aluminum (Al) and/or ammonium perchlorate(AP) in the grain does enhance the regression rate, mainly due to the more energy released inside the chamber and heat feedback to the grain surface by the aluminum combustion.

Autism, Context/Noncontext Information Processing, and Atypical Development

PubMed Central

Skoyles, John R.

2011-01-01

Autism has been attributed to a deficit in contextual information processing. Attempts to understand autism in terms of such a defect, however, do not include more recent computational work upon context. This work has identified that context information processing depends upon the extraction and use of the information hidden in higher-order (or indirect) associations. Higher-order associations underlie the cognition of context rather than that of situations. This paper starts by examining the differences between higher-order and first-order (or direct) associations. Higher-order associations link entities not directly (as with first-order ones) but indirectly through all the connections they have via other entities. Extracting this information requires the processing of past episodes as a totality. As a result, this extraction depends upon specialised extraction processes separate from cognition. This information is then consolidated. Due to this difference, the extraction/consolidation of higher-order information can be impaired whilst cognition remains intact. Although not directly impaired, cognition will be indirectly impaired by knock on effects such as cognition compensating for absent higher-order information with information extracted from first-order associations. This paper discusses the implications of this for the inflexible, literal/immediate, and inappropriate information processing of autistic individuals. PMID:22937255

Efficient simulation of press hardening process through integrated structural and CFD analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palaniswamy, Hariharasudhan; Mondalek, Pamela; Wronski, Maciek

Press hardened steel parts are being increasingly used in automotive structures for their higher strength to meet safety standards while reducing vehicle weight to improve fuel consumption. However, manufacturing of sheet metal parts by press hardening process to achieve desired properties is extremely challenging as it involves complex interaction of plastic deformation, metallurgical change, thermal distribution, and fluid flow. Numerical simulation is critical for successful design of the process and to understand the interaction among the numerous process parameters to control the press hardening process in order to consistently achieve desired part properties. Until now there has been no integratedmore » commercial software solution that can efficiently model the complete process from forming of the blank, heat transfer between the blank and tool, microstructure evolution in the blank, heat loss from tool to the fluid that flows through water channels in the tools. In this study, a numerical solution based on Altair HyperWorks® product suite involving RADIOSS®, a non-linear finite element based structural analysis solver and AcuSolve®, an incompressible fluid flow solver based on Galerkin Least Square Finite Element Method have been utilized to develop an efficient solution for complete press hardening process design and analysis. RADIOSS is used to handle the plastic deformation, heat transfer between the blank and tool, and microstructure evolution in the blank during cooling. While AcuSolve is used to efficiently model heat loss from tool to the fluid that flows through water channels in the tools. The approach is demonstrated through some case studies.« less

Numerical tools to predict the environmental loads for offshore structures under extreme weather conditions

NASA Astrophysics Data System (ADS)

Wu, Yanling

2018-05-01

In this paper, the extreme waves were generated using the open source computational fluid dynamic (CFD) tools — OpenFOAM and Waves2FOAM — using linear and nonlinear NewWave input. They were used to conduct the numerical simulation of the wave impact process. Numerical tools based on first-order (with and without stretching) and second-order NewWave are investigated. The simulation to predict force loading for the offshore platform under the extreme weather condition is implemented and compared.

The fifth-order partial differential equation for the description of the α + β Fermi-Pasta-Ulam model

NASA Astrophysics Data System (ADS)

Kudryashov, Nikolay A.; Volkov, Alexandr K.

2017-01-01

We study a new nonlinear partial differential equation of the fifth order for the description of perturbations in the Fermi-Pasta-Ulam mass chain. This fifth-order equation is an expansion of the Gardner equation for the description of the Fermi-Pasta-Ulam model. We use the potential of interaction between neighbouring masses with both quadratic and cubic terms. The equation is derived using the continuous limit. Unlike the previous works, we take into account higher order terms in the Taylor series expansions. We investigate the equation using the Painlevé approach. We show that the equation does not pass the Painlevé test and can not be integrated by the inverse scattering transform. We use the logistic function method and the Laurent expansion method to find travelling wave solutions of the fifth-order equation. We use the pseudospectral method for the numerical simulation of wave processes, described by the equation.

Intentional and automatic processing of numerical information in mathematical anxiety: testing the influence of emotional priming.

PubMed

Ashkenazi, Sarit

2018-02-05

Current theoretical approaches suggest that mathematical anxiety (MA) manifests itself as a weakness in quantity manipulations. This study is the first to examine automatic versus intentional processing of numerical information using the numerical Stroop paradigm in participants with high MA. To manipulate anxiety levels, we combined the numerical Stroop task with an affective priming paradigm. We took a group of college students with high MA and compared their performance to a group of participants with low MA. Under low anxiety conditions (neutral priming), participants with high MA showed relatively intact number processing abilities. However, under high anxiety conditions (mathematical priming), participants with high MA showed (1) higher processing of the non-numerical irrelevant information, which aligns with the theoretical view regarding deficits in selective attention in anxiety and (2) an abnormal numerical distance effect. These results demonstrate that abnormal, basic numerical processing in MA is context related.

Numerical Flexural Strength Analysis of Thermally Stressed Delaminated Composite Structure under Sinusoidal Loading

NASA Astrophysics Data System (ADS)

Hirwani, C. K.; Biswash, S.; Mehar, K.; Panda, S. K.

2018-03-01

In this article, we investigate the thermomechanical deflection characteristics of the debonded composite plate structure using an isoparametric type of higher-order finite element model. The current formulation is derived using higher-order kinematic theory and the displacement variables described as constant along the thickness direction whereas varying nonlinearly for the in-plane directions. The present mid-plane kinematic model mainly obsoletes the use of shear correction factor as in the other lower-order theories. The separation between the adjacent layers is modeled via the sub-laminate technique and the intermittent continuity conditions imposed to avoid the mathematical ill conditions. The governing equation of equilibrium of the damaged plate structure under the combined state of loading are obtained using the variational principle and solved numerically to compute the deflection values. Further, the convergence test has been performed by refining the numbers of elements and validated through comparing the present results with available published values. The usefulness of the proposed formulation has been discussed by solving the different kind of numerical examples including the size, location and position of delamination.

An almost symmetric Strang splitting scheme for nonlinear evolution equations.

PubMed

Einkemmer, Lukas; Ostermann, Alexander

2014-07-01

In this paper we consider splitting methods for the time integration of parabolic and certain classes of hyperbolic partial differential equations, where one partial flow cannot be computed exactly. Instead, we use a numerical approximation based on the linearization of the vector field. This is of interest in applications as it allows us to apply splitting methods to a wider class of problems from the sciences. However, in the situation described, the classic Strang splitting scheme, while still being a method of second order, is not longer symmetric. This, in turn, implies that the construction of higher order methods by composition is limited to order three only. To remedy this situation, based on previous work in the context of ordinary differential equations, we construct a class of Strang splitting schemes that are symmetric up to a desired order. We show rigorously that, under suitable assumptions on the nonlinearity, these methods are of second order and can then be used to construct higher order methods by composition. In addition, we illustrate the theoretical results by conducting numerical experiments for the Brusselator system and the KdV equation.

An almost symmetric Strang splitting scheme for nonlinear evolution equations☆

PubMed Central

Einkemmer, Lukas; Ostermann, Alexander

2014-01-01

In this paper we consider splitting methods for the time integration of parabolic and certain classes of hyperbolic partial differential equations, where one partial flow cannot be computed exactly. Instead, we use a numerical approximation based on the linearization of the vector field. This is of interest in applications as it allows us to apply splitting methods to a wider class of problems from the sciences. However, in the situation described, the classic Strang splitting scheme, while still being a method of second order, is not longer symmetric. This, in turn, implies that the construction of higher order methods by composition is limited to order three only. To remedy this situation, based on previous work in the context of ordinary differential equations, we construct a class of Strang splitting schemes that are symmetric up to a desired order. We show rigorously that, under suitable assumptions on the nonlinearity, these methods are of second order and can then be used to construct higher order methods by composition. In addition, we illustrate the theoretical results by conducting numerical experiments for the Brusselator system and the KdV equation. PMID:25844017

International Conference on Numerical Ship Hydrodynamics (5th) Held in Hiroshima, Japan on 24-28 September 1989

DTIC Science & Technology

1989-09-28

Introduction source. The near field part N has an integrand which is in terms of the higher order derived exponential integral func- For a number of...Methods for potential produced improved results near the flow calculations including first and stern, but none of them could accura- higher order theories ...method Naghdi method applied to the nonlinear free- in laminar boundary layer theory . I think the surface flow problems. higher theory Green-Naghdi

Numerical investigation and thermodynamic analysis of the effect of electrolyte flow rate on performance of all vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

Khazaeli, Ali; Vatani, Ali; Tahouni, Nassim; Panjeshahi, Mohammad Hassan

2015-10-01

In flow batteries, electrolyte flow rate plays a crucial role on the minimizing mass transfer polarization which is at the compensation of higher pressure drop. In this work, a two-dimensional numerical method is applied to investigate the effect of electrolyte flow rate on cell voltage, maximum depth of discharge and pressure drop a six-cell stack of VRFB. The results show that during the discharge process, increasing electrolyte flow rate can raise the voltage of each cell up to 50 mV on average. Moreover, the maximum depth of discharge dramatically increases with electrolyte flow rate. On the other hand, the pressure drop also positively correlates with electrolyte flow rate. In order to investigate all these effects simultaneously, average energy and exergy efficiencies are introduced in this study for the transient process of VRFB. These efficiencies give insight into choosing an appropriate strategy for the electrolyte flow rate. Finally, the energy efficiency of electricity storage using VRFB is investigated and compared with other energy storage systems. The results illustrate that this kind of battery has at least 61% storage efficiency based on the second law of thermodynamics, which is considerably higher than that of their counterparts.

Numerical simulation of immiscible viscous fingering using adaptive unstructured meshes

NASA Astrophysics Data System (ADS)

Adam, A.; Salinas, P.; Percival, J. R.; Pavlidis, D.; Pain, C.; Muggeridge, A. H.; Jackson, M.

2015-12-01

Displacement of one fluid by another in porous media occurs in various settings including hydrocarbon recovery, CO2 storage and water purification. When the invading fluid is of lower viscosity than the resident fluid, the displacement front is subject to a Saffman-Taylor instability and is unstable to transverse perturbations. These instabilities can grow, leading to fingering of the invading fluid. Numerical simulation of viscous fingering is challenging. The physics is controlled by a complex interplay of viscous and diffusive forces and it is necessary to ensure physical diffusion dominates numerical diffusion to obtain converged solutions. This typically requires the use of high mesh resolution and high order numerical methods. This is computationally expensive. We demonstrate here the use of a novel control volume - finite element (CVFE) method along with dynamic unstructured mesh adaptivity to simulate viscous fingering with higher accuracy and lower computational cost than conventional methods. Our CVFE method employs a discontinuous representation for both pressure and velocity, allowing the use of smaller control volumes (CVs). This yields higher resolution of the saturation field which is represented CV-wise. Moreover, dynamic mesh adaptivity allows high mesh resolution to be employed where it is required to resolve the fingers and lower resolution elsewhere. We use our results to re-examine the existing criteria that have been proposed to govern the onset of instability.Mesh adaptivity requires the mapping of data from one mesh to another. Conventional methods such as consistent interpolation do not readily generalise to discontinuous fields and are non-conservative. We further contribute a general framework for interpolation of CV fields by Galerkin projection. The method is conservative, higher order and yields improved results, particularly with higher order or discontinuous elements where existing approaches are often excessively diffusive.

Electrophysiological evidence for differential processing of numerical quantity and order in humans.

PubMed

Turconi, Eva; Jemel, Boutheina; Rossion, Bruno; Seron, Xavier

2004-09-01

It is yet unclear whether the processing of number magnitude and order rely on common or different functional processes and neural substrates. On the one hand, recent neuroimaging studies show that quantity and order coding activate the same areas in the parietal and prefrontal cortices. On the other hand, evidence from developmental and neuropsychological studies suggest dissociated mechanisms for processing quantity and order information. To clarify this issue, the present study investigated the spatio-temporal course of quantity and order coding operations using event-related potentials (ERPs). Twenty-four subjects performed a quantity task (classifying numbers as smaller or larger than 15) and an order task on the same material (classifying numbers as coming before or after 15), as well as a control order task on letters (classifying letters as coming before or after M). Behavioral results showed a classical distance effect (decreasing reaction times [RTs] with increasing distance from the standard) for all tasks. In agreement with previous electrophysiological evidence, this effect was significant on a P2 parietal component for numerical material. However, the difference between processing numbers close or far from the target appeared earlier and was larger on the left hemisphere for quantity processing, while it was delayed and bilateral for order processing. There was also a significant distance effect in all tasks on parietal sites for the following P3 component elicited by numbers, but this effect was larger on prefrontal areas for the order judgment. In conclusion, both quantity and order show similar behavioral effects, but they are associated with different spatio-temporal courses in parietal and prefrontal cortices.

Extremely low order time-fractional differential equation and application in combustion process

NASA Astrophysics Data System (ADS)

Xu, Qinwu; Xu, Yufeng

2018-11-01

Fractional blow-up model, especially which is of very low order of fractional derivative, plays a significant role in combustion process. The order of time-fractional derivative in diffusion model essentially distinguishes the super-diffusion and sub-diffusion processes when it is relatively high or low accordingly. In this paper, the blow-up phenomenon and condition of its appearance are theoretically proved. The blow-up moment is estimated by using differential inequalities. To numerically study the behavior around blow-up point, a mixed numerical method based on adaptive finite difference on temporal direction and highly effective discontinuous Galerkin method on spatial direction is proposed. The time of blow-up is calculated accurately. In simulation, we analyze the dynamics of fractional blow-up model under different orders of fractional derivative. It is found that the lower the order, the earlier the blow-up comes, by fixing the other parameters in the model. Our results confirm the physical truth that a combustor for explosion cannot be too small.

Cylindrical optical resonators: fundamental properties and bio-sensing characteristics

NASA Astrophysics Data System (ADS)

Khozeymeh, Foroogh; Razaghi, Mohammad

2018-04-01

In this paper, detailed theoretical analysis of cylindrical resonators is demonstrated. As illustrated, these kinds of resonators can be used as optical bio-sensing devices. The proposed structure is analyzed using an analytical method based on Lam's approximation. This method is systematic and has simplified the tedious process of whispering-gallery mode (WGM) wavelength analysis in optical cylindrical biosensors. By this method, analysis of higher radial orders of high angular momentum WGMs has been possible. Using closed-form analytical equations, resonance wavelengths of higher radial and angular order WGMs of TE and TM polarization waves are calculated. It is shown that high angular momentum WGMs are more appropriate for bio-sensing applications. Some of the calculations are done using a numerical non-linear Newton method. A perfect match of 99.84% between the analytical and the numerical methods has been achieved. In order to verify the validity of the calculations, Meep simulations based on the finite difference time domain (FDTD) method are performed. In this case, a match of 96.70% between the analytical and FDTD results has been obtained. The analytical predictions are in good agreement with other experimental work (99.99% match). These results validate the proposed analytical modelling for the fast design of optical cylindrical biosensors. It is shown that by extending the proposed two-layer resonator structure analyzing scheme, it is possible to study a three-layer cylindrical resonator structure as well. Moreover, by this method, fast sensitivity optimization in cylindrical resonator-based biosensors has been possible. Sensitivity of the WGM resonances is analyzed as a function of the structural parameters of the cylindrical resonators. Based on the results, fourth radial order WGMs, with a resonator radius of 50 μm, display the most bulk refractive index sensitivity of 41.50 (nm/RIU).

Numerical simulation on chain-die forming of an AHSS top-hat section

NASA Astrophysics Data System (ADS)

Majji, Raju; Xiang, Yang; Ding, Scott; Yang, Chunhui

2018-05-01

The applications of Advanced High-Strength Steels (AHSS) in the automotive industry are rapidly increasing due to a demand for a lightweight material that significantly reduces fuel consumption without compromising passenger safety. Automotive industries and material suppliers are expected by consumers to deliver reliable and affordable products, thus stimulating these manufacturers to research solutions to meet these customer requirements. The primary advantage of AHSS is its extremely high strength to weight ratio, an ideal material for the automotive industry. However, its low ductility is a major disadvantage, in particular, when using traditional cold forming processes such as roll forming and deep drawing process to form profiles. Consequently, AHSS parts frequently fail to form. Thereby, in order to improve quality and reliability on manufacturing AHSS products, a recently-developed incremental cold sheet metal forming technology called Chain-die Forming (CDF) is recognised as a potential solution to the forming process of AHSS. The typical CDF process is a combination of bending and roll forming processes which is equivalent to a roll with a large deforming radius, and incrementally forms the desired shape with split die and segments. This study focuses on manufacturing an AHSS top-hat section with minimum passes without geometrical or surface defects by using finite element modelling and simulations. The developed numerical simulation is employed to investigate the influences on the main control parameter of the CDF process while forming AHSS products and further develop new die-punch sets of compensation design via a numerical optimal process. In addition, the study focuses on the tool design to compensate spring-back and reduce friction between tooling and sheet-metal. This reduces the number of passes, thereby improving productivity and reducing energy consumption and material waste. This numerical study reveals that CDF forms AHSS products of complex profiles with much less residual stress, low spring back, low strain and of higher geometrical accuracy compared to other traditional manufacturing processes.

Young children's non-numerical ordering ability at the start of formal education longitudinally predicts their symbolic number skills and academic achievement in maths.

PubMed

O'Connor, Patrick A; Morsanyi, Kinga; McCormack, Teresa

2018-01-25

Ordinality is a fundamental feature of numbers and recent studies have highlighted the role that number ordering abilities play in mathematical development (e.g., Lyons et al., ), as well as mature mathematical performance (e.g., Lyons & Beilock, ). The current study tested the novel hypothesis that non-numerical ordering ability, as measured by the ordering of familiar sequences of events, also plays an important role in maths development. Ninety children were tested in their first school year and 87 were followed up at the end of their second school year, to test the hypothesis that ordinal processing, including the ordering of non-numerical materials, would be related to their maths skills both cross-sectionally and longitudinally. The results confirmed this hypothesis. Ordinal processing measures were significantly related to maths both cross-sectionally and longitudinally, and children's non-numerical ordering ability in their first year of school (as measured by order judgements for everyday events and the parents' report of their child's everyday ordering ability) was the strongest longitudinal predictor of maths one year later, when compared to several measures that are traditionally considered to be important predictors of early maths development. Children's everyday ordering ability, as reported by parents, also significantly predicted growth in formal maths ability between Year 1 and Year 2, although this was not the case for the event ordering task. The present study provides strong evidence that domain-general ordering abilities play an important role in the development of children's maths skills at the beginning of formal education. © 2018 John Wiley & Sons Ltd.

Optimization of the Bridgman crystal growth process

NASA Astrophysics Data System (ADS)

Margulies, M.; Witomski, P.; Duffar, T.

2004-05-01

A numerical optimization method of the vertical Bridgman growth configuration is presented and developed. It permits to optimize the furnace temperature field and the pulling rate versus time in order to decrease the radial thermal gradients in the sample. Some constraints are also included in order to insure physically realistic results. The model includes the two classical non-linearities associated to crystal growth processes, the radiative thermal exchange and the release of latent heat at the solid-liquid interface. The mathematical analysis and development of the problem is shortly described. On some examples, it is shown that the method works in a satisfactory way; however the results are dependent on the numerical parameters. Improvements of the optimization model, on the physical and numerical point of view, are suggested.

Numerical investigations on the lateral angular co-extrusion of aluminium and steel

NASA Astrophysics Data System (ADS)

Behrens, B.-A.; Klose, C.; Chugreev, A.; Thürer, S. E.; Uhe, J.

2018-05-01

In order to save weight and costs, different materials can be combined within one component. In the novel process chain being developed within the Collaborative Research Centre (CRC) 1153, joined semi-finished workpieces are used to produce hybrid solid components with locally adapted properties. Different materials are joined in an initial step before the forming process takes place. Hereby, the quality of the joining zone is improved by means of the thermo-mechanical treatment during the forming and machining processes. The lateral angular co-extrusion (LACE) approach is used to produce semi-finished workpieces because it allows for the production of coaxial semi-finished products consisting of aluminium and steel. In the further process chain, these semi-finished products are processed into hybrid bearing bushings with locally adapted properties by die forging. In the scope of this work, numerical investigations of the co-extrusion of aluminium-steel compounds were carried out using finite element (FE) simulation in order to examine the influence of the process parameters on the co-extrusion process. For this purpose, the relevant material properties of the aluminium alloy EN AW-6082 were determined experimentally and subsequently implemented in the numerical model. The obtained numerical model was used to study the impact of different ram speeds, press ratios and billet temperatures on the resulting extrusion forces and the material flow. The numerical results have been validated using force-time curves obtained from experimental extrusion tests carried out on a 2.5 MN laboratory extrusion press.

Grayness-dependent emission of dispersive waves from dark solitons in optical fibers.

PubMed

Marest, T; Arabí, C Mas; Conforti, M; Mussot, A; Milián, C; Skryabin, D V; Kudlinski, A

2018-04-01

We report the experimental observation of dispersive wave emission from gray solitons propagating in the normal dispersion region of an optical fiber. Besides observing for the first time, to the best of our knowledge, the emission of a dispersive wave from an isolated dark soliton, we show that the dispersive wave frequency and amplitude strongly depend on soliton grayness. This process can be explained by the higher-order dispersion contribution into the phase-matching condition and the grayness of the soliton. Numerical simulations and theoretical predictions are in good agreement with the experiments.

Numerical Ordering Ability Mediates the Relation between Number-Sense and Arithmetic Competence

ERIC Educational Resources Information Center

Lyons, Ian M.; Beilock, Sian L.

2011-01-01

What predicts human mathematical competence? While detailed models of number representation in the brain have been developed, it remains to be seen exactly how basic number representations link to higher math abilities. We propose that representation of ordinal associations between numerical symbols is one important factor that underpins this…

The educational effectiveness of computer-based instruction

NASA Astrophysics Data System (ADS)

Renshaw, Carl E.; Taylor, Holly A.

2000-07-01

Although numerous studies have shown that computer-based education is effective for enhancing rote memorization, the impact of these tools on higher-order cognitive skills, such as critical thinking, is less clear. Existing methods for evaluating educational effectiveness, such as surveys, quizzes and pre- or post-interviews, may not be effective for evaluating impact on critical thinking skills because students are not always aware of the effects the software has on their thought processes. We review an alternative evaluation strategy whereby the student's mastery of a specific cognitive skill is directly assessed both before and after participating in a computer-based exercise. Methodologies for assessing cognitive skill are based on recent advances in the fields of cognitive science. Results from two studies show that computer-based exercises can positively impact the higher-order cognitive skills of some students. However, a given exercise will not impact all students equally. This suggests that further work is needed to understand how and why CAI software is more or less effective within a given population.

Application of the fuzzy topsis multi-attribute decision making method to determine scholarship recipients

NASA Astrophysics Data System (ADS)

Irvanizam, I.

2018-03-01

Some scholarships have been routinely offered by Ministry of Research, Technology and Higher Education of the Republic of Indonesia for students at Syiah Kuala University. In reality, the scholarship selection process is becoming subjective and highly complex problem. Multi-Attribute Decision Making (MADM) techniques can be a solution in order to solve scholarship selection problem. In this study, we demonstrated the application of a fuzzy TOPSIS as an MADM technique by using a numerical example in order to calculate a triangular fuzzy number for the fuzzy data onto a normalized weight. We then use this normalized value to construct the normalized fuzzy decision matrix. We finally use the fuzzy TOPSIS to rank alternatives in descending order based on the relative closeness to the ideal solution. The result in terms of final ranking shows slightly different from the previous work.

A space-time discretization procedure for wave propagation problems

NASA Technical Reports Server (NTRS)

Davis, Sanford

1989-01-01

Higher order compact algorithms are developed for the numerical simulation of wave propagation by using the concept of a discrete dispersion relation. The dispersion relation is the imprint of any linear operator in space-time. The discrete dispersion relation is derived from the continuous dispersion relation by examining the process by which locally plane waves propagate through a chosen grid. The exponential structure of the discrete dispersion relation suggests an efficient splitting of convective and diffusive terms for dissipative waves. Fourth- and eighth-order convection schemes are examined that involve only three or five spatial grid points. These algorithms are subject to the same restrictions that govern the use of dispersion relations in the constructions of asymptotic expansions to nonlinear evolution equations. A new eighth-order scheme is developed that is exact for Courant numbers of 1, 2, 3, and 4. Examples are given of a pulse and step wave with a small amount of physical diffusion.

Solution of the hydrodynamic device model using high-order non-oscillatory shock capturing algorithms

NASA Technical Reports Server (NTRS)

Fatemi, Emad; Jerome, Joseph; Osher, Stanley

1989-01-01

A micron n+ - n - n+ silicon diode is simulated via the hydrodynamic model for carrier transport. The numerical algorithms employed are for the non-steady case, and a limiting process is used to reach steady state. The simulation employs shock capturing algorithms, and indeed shocks, or very rapid transition regimes, are observed in the transient case for the coupled system, consisting of the potential equation and the conservation equations describing charge, momentum, and energy transfer for the electron carriers. These algorithms, termed essentially non-oscillatory, were successfully applied in other contexts to model the flow in gas dynamics, magnetohydrodynamics, and other physical situations involving the conservation laws in fluid mechanics. The method here is first order in time, but the use of small time steps allows for good accuracy. Runge-Kutta methods allow one to achieve higher accuracy in time if desired. The spatial accuracy is of high order in regions of smoothness.

Pole-placement Predictive Functional Control for under-damped systems with real numbers algebra.

PubMed

Zabet, K; Rossiter, J A; Haber, R; Abdullah, M

2017-11-01

This paper presents the new algorithm of PP-PFC (Pole-placement Predictive Functional Control) for stable, linear under-damped higher-order processes. It is shown that while conventional PFC aims to get first-order exponential behavior, this is not always straightforward with significant under-damped modes and hence a pole-placement PFC algorithm is proposed which can be tuned more precisely to achieve the desired dynamics, but exploits complex number algebra and linear combinations in order to deliver guarantees of stability and performance. Nevertheless, practical implementation is easier by avoiding complex number algebra and hence a modified formulation of the PP-PFC algorithm is also presented which utilises just real numbers while retaining the key attributes of simple algebra, coding and tuning. The potential advantages are demonstrated with numerical examples and real-time control of a laboratory plant. Copyright © 2017 ISA. All rights reserved.

Continuous and Discrete Structured Population Models with Applications to Epidemiology and Marine Mammals

NASA Astrophysics Data System (ADS)

Tang, Tingting

In this dissertation, we develop structured population models to examine how changes in the environmental affect population processes. In Chapter 2, we develop a general continuous time size structured model describing a susceptible-infected (SI) population coupled with the environment. This model applies to problems arising in ecology, epidemiology, and cell biology. The model consists of a system of quasilinear hyperbolic partial differential equations coupled with a system of nonlinear ordinary differential equations that represent the environment. We develop a second-order high resolution finite difference scheme to numerically solve the model. Convergence of this scheme to a weak solution with bounded total variation is proved. We numerically compare the second order high resolution scheme with a first order finite difference scheme. Higher order of convergence and high resolution property are observed in the second order finite difference scheme. In addition, we apply our model to a multi-host wildlife disease problem, questions regarding the impact of the initial population structure and transition rate within each host are numerically explored. In Chapter 3, we use a stage structured matrix model for wildlife population to study the recovery process of the population given an environmental disturbance. We focus on the time it takes for the population to recover to its pre-event level and develop general formulas to calculate the sensitivity or elasticity of the recovery time to changes in the initial population distribution, vital rates and event severity. Our results suggest that the recovery time is independent of the initial population size, but is sensitive to the initial population structure. Moreover, it is more sensitive to the reduction proportion to the vital rates of the population caused by the catastrophe event relative to the duration of impact of the event. We present the potential application of our model to the amphibian population dynamic and the recovery of a certain plant population. In addition, we explore, in details, the application of the model to the sperm whale population in Gulf of Mexico after the Deepwater Horizon oil spill. In Chapter 4, we summarize the results from Chapter 2 and Chapter 3 and explore some further avenues of our research.

The cubic-quintic-septic complex Ginzburg-Landau equation formulation of optical pulse propagation in 3D doped Kerr media with higher-order dispersions

NASA Astrophysics Data System (ADS)

Djoko, Martin; Kofane, T. C.

2018-06-01

We investigate the propagation characteristics and stabilization of generalized-Gaussian pulse in highly nonlinear homogeneous media with higher-order dispersion terms. The optical pulse propagation has been modeled by the higher-order (3+1)-dimensional cubic-quintic-septic complex Ginzburg-Landau [(3+1)D CQS-CGL] equation. We have used the variational method to find a set of differential equations characterizing the variation of the pulse parameters in fiber optic-links. The variational equations we obtained have been integrated numerically by the means of the fourth-order Runge-Kutta (RK4) method, which also allows us to investigate the evolution of the generalized-Gaussian beam and the pulse evolution along an optical doped fiber. Then, we have solved the original nonlinear (3+1)D CQS-CGL equation with the split-step Fourier method (SSFM), and compare the results with those obtained, using the variational approach. A good agreement between analytical and numerical methods is observed. The evolution of the generalized-Gaussian beam has shown oscillatory propagation, and bell-shaped dissipative optical bullets have been obtained under certain parameter values in both anomalous and normal chromatic dispersion regimes. Using the natural control parameter of the solution as it evolves, named the total energy Q, our numerical simulations reveal the existence of 3D stable vortex dissipative light bullets, 3D stable spatiotemporal optical soliton, stationary and pulsating optical bullets, depending on the used initial input condition (symmetric or elliptic).

SHARP: A Spatially Higher-order, Relativistic Particle-in-cell Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shalaby, Mohamad; Broderick, Avery E.; Chang, Philip

Numerical heating in particle-in-cell (PIC) codes currently precludes the accurate simulation of cold, relativistic plasma over long periods, severely limiting their applications in astrophysical environments. We present a spatially higher-order accurate relativistic PIC algorithm in one spatial dimension, which conserves charge and momentum exactly. We utilize the smoothness implied by the usage of higher-order interpolation functions to achieve a spatially higher-order accurate algorithm (up to the fifth order). We validate our algorithm against several test problems—thermal stability of stationary plasma, stability of linear plasma waves, and two-stream instability in the relativistic and non-relativistic regimes. Comparing our simulations to exact solutionsmore » of the dispersion relations, we demonstrate that SHARP can quantitatively reproduce important kinetic features of the linear regime. Our simulations have a superior ability to control energy non-conservation and avoid numerical heating in comparison to common second-order schemes. We provide a natural definition for convergence of a general PIC algorithm: the complement of physical modes captured by the simulation, i.e., those that lie above the Poisson noise, must grow commensurately with the resolution. This implies that it is necessary to simultaneously increase the number of particles per cell and decrease the cell size. We demonstrate that traditional ways for testing for convergence fail, leading to plateauing of the energy error. This new PIC code enables us to faithfully study the long-term evolution of plasma problems that require absolute control of the energy and momentum conservation.« less

A DG approach to the numerical solution of the Stein-Stein stochastic volatility option pricing model

NASA Astrophysics Data System (ADS)

Hozman, J.; Tichý, T.

2017-12-01

Stochastic volatility models enable to capture the real world features of the options better than the classical Black-Scholes treatment. Here we focus on pricing of European-style options under the Stein-Stein stochastic volatility model when the option value depends on the time, on the price of the underlying asset and on the volatility as a function of a mean reverting Orstein-Uhlenbeck process. A standard mathematical approach to this model leads to the non-stationary second-order degenerate partial differential equation of two spatial variables completed by the system of boundary and terminal conditions. In order to improve the numerical valuation process for a such pricing equation, we propose a numerical technique based on the discontinuous Galerkin method and the Crank-Nicolson scheme. Finally, reference numerical experiments on real market data illustrate comprehensive empirical findings on options with stochastic volatility.

Improved diffusion Monte Carlo propagators for bosonic systems using Itô calculus

NASA Astrophysics Data System (ADS)

Hâkansson, P.; Mella, M.; Bressanini, Dario; Morosi, Gabriele; Patrone, Marta

2006-11-01

The construction of importance sampled diffusion Monte Carlo (DMC) schemes accurate to second order in the time step is discussed. A central aspect in obtaining efficient second order schemes is the numerical solution of the stochastic differential equation (SDE) associated with the Fokker-Plank equation responsible for the importance sampling procedure. In this work, stochastic predictor-corrector schemes solving the SDE and consistent with Itô calculus are used in DMC simulations of helium clusters. These schemes are numerically compared with alternative algorithms obtained by splitting the Fokker-Plank operator, an approach that we analyze using the analytical tools provided by Itô calculus. The numerical results show that predictor-corrector methods are indeed accurate to second order in the time step and that they present a smaller time step bias and a better efficiency than second order split-operator derived schemes when computing ensemble averages for bosonic systems. The possible extension of the predictor-corrector methods to higher orders is also discussed.

Precision in ground-based solar polarimetry: simulating the role of adaptive optics.

PubMed

Krishnappa, Nagaraju; Feller, Alex

2012-11-20

Accurate measurement of polarization in spectral lines is important for the reliable inference of magnetic fields on the Sun. For ground-based observations, polarimetric precision is severely limited by the presence of Earth's atmosphere. Atmospheric turbulence (seeing) produces signal fluctuations, which combined with the nonsimultaneous nature of the measurement process cause intermixing of the Stokes parameters known as seeing-induced polarization cross talk. Previous analysis of this effect [Appl. Opt. 43, 3817 (2004)] suggests that cross talk is reduced not only with increase in modulation frequency but also by compensating the seeing-induced image aberrations by an adaptive optics (AO) system. However, in those studies the effect of higher-order image aberrations than those corrected by the AO system was not taken into account. We present in this paper an analysis of seeing-induced cross talk in the presence of higher-order image aberrations through numerical simulation. In this analysis we find that the amount of cross talk among Stokes parameters is practically independent of the degree of image aberration corrected by an AO system. However, higher-order AO corrections increase the signal-to-noise ratio by reducing the seeing caused image smearing. Further we find, in agreement with the earlier results, that cross talk is reduced considerably by increasing the modulation frequency.

Filtering of higher-order laser modes using plasma structures

NASA Astrophysics Data System (ADS)

Djordjevic, Blagoje; Benedetti, Carlo; Schroeder, Carl; Esarey, Eric; Leemans, Wim

2017-10-01

Plasma structures based on leaky channels are proposed to filter higher-order laser mode content. The evolution and propagation of non-Gaussian laser pulses in leaky channels is studied, and it is shown that, for appropriate laser-plasma parameters, the higher-order laser mode content may be removed while the fundamental mode remains well-guided. The behavior of the multi-mode laser pulse is described analytically, including the derivation of the leakage coefficients, and compared to numerical calculations. Gaussian laser pulse propagation, without higher-order mode content, improves guiding in parabolic plasma channels, enabling extended interaction lengths for laser-plasma accelerator applications. This work was supported by the Director, Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Arbitrary-order corrections for finite-time drift and diffusion coefficients

NASA Astrophysics Data System (ADS)

Anteneodo, C.; Riera, R.

2009-09-01

We address a standard class of diffusion processes with linear drift and quadratic diffusion coefficients. These contributions to dynamic equations can be directly drawn from data time series. However, real data are constrained to finite sampling rates and therefore it is crucial to establish a suitable mathematical description of the required finite-time corrections. Based on Itô-Taylor expansions, we present the exact corrections to the finite-time drift and diffusion coefficients. These results allow to reconstruct the real hidden coefficients from the empirical estimates. We also derive higher-order finite-time expressions for the third and fourth conditional moments that furnish extra theoretical checks for this class of diffusion models. The analytical predictions are compared with the numerical outcomes of representative artificial time series.

The refractive index in electron microscopy and the errors of its approximations.

PubMed

Lentzen, M

2017-05-01

In numerical calculations for electron diffraction often a simplified form of the electron-optical refractive index, linear in the electric potential, is used. In recent years improved calculation schemes have been proposed, aiming at higher accuracy by including higher-order terms of the electric potential. These schemes start from the relativistically corrected Schrödinger equation, and use a second simplified form, now for the refractive index squared, being linear in the electric potential. The second and higher-order corrections thus determined have, however, a large error, compared to those derived from the relativistically correct refractive index. The impact of the two simplifications on electron diffraction calculations is assessed through numerical comparison of the refractive index at high-angle Coulomb scattering and of cross-sections for a wide range of scattering angles, kinetic energies, and atomic numbers. Copyright © 2016 Elsevier B.V. All rights reserved.

Experimental analysis and modeling of ultrasound assisted freezing of potato spheres.

PubMed

Kiani, Hossein; Zhang, Zhihang; Sun, Da-Wen

2015-09-01

In recent years, innovative methods such as ultrasound assisted freezing have been developed in order to improve the freezing process. During freezing of foods, accurate prediction of the temperature distribution, phase ratios, and process time is very important. In the present study, ultrasound assisted immersion freezing process (in 1:1 ethylene glycol-water solution at 253.15K) of potato spheres (0.02 m diameter) was evaluated using experimental, numerical and analytical approaches. Ultrasound (25 kHz, 890 W m(-2)) was irradiated for different duty cycles (DCs=0-100%). A finite volume based enthalpy method was used in the numerical model, based on which temperature and liquid fraction profiles were simulated by a program developed using OpenFOAM® CFD software. An analytical technique was also employed to calculate freezing times. The results showed that ultrasound irradiation could decrease the characteristic freezing time of potatoes. Since ultrasound irradiation increased the heat transfer coefficient but simultaneously generated heat at the surface of the samples, an optimum DC was needed for the shortest freezing time which occurred in the range of 30-70% DC. DCs higher than 70% increased the freezing time. DCs lower than 30% did not provide significant effects on the freezing time compared to the control sample. The numerical model predicted the characteristic freezing time in accordance with the experimental results. In addition, analytical calculation of characteristic freezing time exhibited qualitative agreement with the experimental results. As the numerical simulations provided profiles of temperature and water fraction within potatoes frozen with or without ultrasound, the models can be used to study and control different operation situations, and to improve the understanding of the freezing process. Copyright © 2015 Elsevier B.V. All rights reserved.

Low-bending loss and single-mode operation in few-mode optical fiber

NASA Astrophysics Data System (ADS)

Yin, Ping; Wang, Hua; Chen, Ming-Yang; Wei, Jin; Cai, Zhi-Min; Li, Lu-Ming; Yang, Ji-Hai; Zhu, Yuan-Feng

2016-10-01

The technique of eliminating the higher-order modes in a few-mode optical fiber is proposed. The fiber is designed with a group of defect modes in the cladding. The higher-order modes in the fiber can be eliminated by bending the fiber to induce strong coupling between the defect modes and the higher-order modes. Numerical simulation shows the bending losses of the LP01 mode are lower than 1.5×10-4 dB/turn for the wavelength shorter than 1.625 μm. The proposed fiber can be bent multiple turns at small bending radius which are preferable for FTTH related applications.

Green's function multiple-scattering theory with a truncated basis set: An augmented-KKR formalism

NASA Astrophysics Data System (ADS)

Alam, Aftab; Khan, Suffian N.; Smirnov, A. V.; Nicholson, D. M.; Johnson, Duane D.

2014-11-01

The Korringa-Kohn-Rostoker (KKR) Green's function, multiple-scattering theory is an efficient site-centered, electronic-structure technique for addressing an assembly of N scatterers. Wave functions are expanded in a spherical-wave basis on each scattering center and indexed up to a maximum orbital and azimuthal number Lmax=(l,mmax), while scattering matrices, which determine spectral properties, are truncated at Lt r=(l,mt r) where phase shifts δl >ltr are negligible. Historically, Lmax is set equal to Lt r, which is correct for large enough Lmax but not computationally expedient; a better procedure retains higher-order (free-electron and single-site) contributions for Lmax>Lt r with δl >ltr set to zero [X.-G. Zhang and W. H. Butler, Phys. Rev. B 46, 7433 (1992), 10.1103/PhysRevB.46.7433]. We present a numerically efficient and accurate augmented-KKR Green's function formalism that solves the KKR equations by exact matrix inversion [R3 process with rank N (ltr+1 ) 2 ] and includes higher-L contributions via linear algebra [R2 process with rank N (lmax+1) 2 ]. The augmented-KKR approach yields properly normalized wave functions, numerically cheaper basis-set convergence, and a total charge density and electron count that agrees with Lloyd's formula. We apply our formalism to fcc Cu, bcc Fe, and L 1 0 CoPt and present the numerical results for accuracy and for the convergence of the total energies, Fermi energies, and magnetic moments versus Lmax for a given Lt r.

In search of discernible infrasound emitted by numerically simulated tornadoes

NASA Astrophysics Data System (ADS)

Schecter, David A.

2012-09-01

The comprehensive observational study of Bedard (2005) provisionally found that the infrasound of a tornado is discernible from the infrasound of generic cloud processes in a convective storm. This paper discusses an attempt to corroborate the reported observations of distinct tornado infrasound with numerical simulations. Specifically, this paper investigates the infrasound of an ordinary tornado in a numerical experiment with the Regional Atmospheric Modeling System, customized to simulate acoustic phenomena. The simulation has no explicit parameterization of microphysical cloud processes, but creates an unsteady tornado of moderate strength by constant thermal forcing in a rotational environment. Despite strong fluctuations in the lower corner flow and upper outflow regions, a surprisingly low level of infrasound is radiated by the vortex. Infrasonic pressure waves in the 0.1 Hz frequency regime are less intense than those which could be generated by core-scale vortex Rossby (VR) waves of modest amplitude in similar vortices. Higher frequency infrasound is at least an order of magnitude weaker than expected based on infrasonic observations of tornadic thunderstorms. Suppression of VR waves (and their infrasound) is explained by the gradual decay of axial vorticity with increasing radius from the center of the vortex core. Such non-Rankine wind-structure is known to enable the rapid damping of VR waves by inviscid mechanisms, including resonant wave-mean flow interaction and "spiral wind-up" of vorticity. Insignificant levels of higher frequency infrasound may be due to oversimplifications in the computational setup, such as the neglect of thermal fluctuations caused by phase transitions of moisture in vigorous cloud turbulence.

Green's function multiple-scattering theory with a truncated basis set: An augmented-KKR formalism

DOE PAGES

Alam, Aftab; Khan, Suffian N.; Smirnov, A. V.; ...

2014-11-04

Korringa-Kohn-Rostoker (KKR) Green's function, multiple-scattering theory is an ecient sitecentered, electronic-structure technique for addressing an assembly of N scatterers. Wave-functions are expanded in a spherical-wave basis on each scattering center and indexed up to a maximum orbital and azimuthal number L max = (l,m) max, while scattering matrices, which determine spectral properties, are truncated at L tr = (l,m) tr where phase shifts δl>l tr are negligible. Historically, L max is set equal to L tr, which is correct for large enough L max but not computationally expedient; a better procedure retains higher-order (free-electron and single-site) contributions for L maxmore » > L tr with δl>l tr set to zero [Zhang and Butler, Phys. Rev. B 46, 7433]. We present a numerically ecient and accurate augmented-KKR Green's function formalism that solves the KKR equations by exact matrix inversion [R 3 process with rank N(l tr + 1) 2] and includes higher-L contributions via linear algebra [R 2 process with rank N(l max +1) 2]. Augmented-KKR approach yields properly normalized wave-functions, numerically cheaper basis-set convergence, and a total charge density and electron count that agrees with Lloyd's formula. We apply our formalism to fcc Cu, bcc Fe and L1 0 CoPt, and present the numerical results for accuracy and for the convergence of the total energies, Fermi energies, and magnetic moments versus L max for a given L tr.« less

Lattice Boltzmann approach for complex nonequilibrium flows.

PubMed

Montessori, A; Prestininzi, P; La Rocca, M; Succi, S

2015-10-01

We present a lattice Boltzmann realization of Grad's extended hydrodynamic approach to nonequilibrium flows. This is achieved by using higher-order isotropic lattices coupled with a higher-order regularization procedure. The method is assessed for flow across parallel plates and three-dimensional flows in porous media, showing excellent agreement of the mass flow with analytical and numerical solutions of the Boltzmann equation across the full range of Knudsen numbers, from the hydrodynamic regime to ballistic motion.

Efficient High-Fidelity, Geometrically Exact, Multiphysics Structural Models

DTIC Science & Technology

2011-10-14

fuctionally graded core. International Journal for Numerical Methods in Engineering, 68:940– 966, 2006. 7F. Shang, Z. Wang, and Z. Li. Analysis of...normal deformable plate theory and MLPG method with radial basis fuctions . Composite Structures, 80:539– 552, 2007. 17W. Zhen and W. Chen. A higher-order...functionally graded plates by using higher-order shear and normal deformable plate theory and MLPG method with radial basis fuctions . Composite Structures, 80

Higher order Stark effect and transition probabilities on hyperfine structure components of hydrogen like atoms

NASA Astrophysics Data System (ADS)

Pal'Chikov, V. G.

2000-08-01

A quantum-electrodynamical (QED) perturbation theory is developed for hydrogen and hydrogen-like atomic systems with interaction between bound electrons and radiative field being treated as the perturbation. The dependence of the perturbed energy of levels on hyperfine structure (hfs) effects and on the higher-order Stark effect is investigated. Numerical results have been obtained for the transition probability between the hfs components of hydrogen-like bismuth.

Correlated bursts and the role of memory range

NASA Astrophysics Data System (ADS)

Jo, Hang-Hyun; Perotti, Juan I.; Kaski, Kimmo; Kertész, János

2015-08-01

Inhomogeneous temporal processes in natural and social phenomena have been described by bursts that are rapidly occurring events within short time periods alternating with long periods of low activity. In addition to the analysis of heavy-tailed interevent time distributions, higher-order correlations between interevent times, called correlated bursts, have been studied only recently. As the underlying mechanism behind such correlated bursts is far from being fully understood, we devise a simple model for correlated bursts using a self-exciting point process with a variable range of memory. Whether a new event occurs is stochastically determined by a memory function that is the sum of decaying memories of past events. In order to incorporate the noise and/or limited memory capacity of systems, we apply two memory loss mechanisms: a fixed number or a variable number of memories. By analysis and numerical simulations, we find that too much memory effect may lead to a Poissonian process, implying that there exists an intermediate range of memory effect to generate correlated bursts comparable to empirical findings. Our conclusions provide a deeper understanding of how long-range memory affects correlated bursts.

Design study of beam position monitors for measuring second-order moments of charged particle beams

NASA Astrophysics Data System (ADS)

Yanagida, Kenichi; Suzuki, Shinsuke; Hanaki, Hirofumi

2012-01-01

This paper presents a theoretical investigation on the multipole moments of charged particle beams in two-dimensional polar coordinates. The theoretical description of multipole moments is based on a single-particle system that is expanded to a multiparticle system by superposition, i.e., summing over all single-particle results. This paper also presents an analysis and design method for a beam position monitor (BPM) that detects higher-order (multipole) moments of a charged particle beam. To calculate the electric fields, a numerical analysis based on the finite difference method was created and carried out. Validity of the numerical analysis was proven by comparing the numerical with the analytical results for a BPM with circular cross section. Six-electrode BPMs with circular and elliptical cross sections were designed for the SPring-8 linac. The results of the numerical calculations show that the second-order moment can be detected for beam sizes ≧420μm (circular) and ≧550μm (elliptical).

Electrophysiological Markers of Newly Acquired Symbolic Numerical Representations: The Role of Magnitude and Ordinal Information

ERIC Educational Resources Information Center

Merkley, Rebecca; Shimi, Andria; Scerif, Gaia

2016-01-01

It is not yet understood how children acquire the meaning of numerical symbols and most existing research has focused on the role of approximate non-symbolic representations of number in this process (see Piazza, ("Trends in Cognitive" 14(12):542-551, 2010). However, numerical symbols necessitate an understanding of both order and…

Structured Overlapping Grid Simulations of Contra-rotating Open Rotor Noise

NASA Technical Reports Server (NTRS)

Housman, Jeffrey A.; Kiris, Cetin C.

2015-01-01

Computational simulations using structured overlapping grids with the Launch Ascent and Vehicle Aerodynamics (LAVA) solver framework are presented for predicting tonal noise generated by a contra-rotating open rotor (CROR) propulsion system. A coupled Computational Fluid Dynamics (CFD) and Computational AeroAcoustics (CAA) numerical approach is applied. Three-dimensional time-accurate hybrid Reynolds Averaged Navier-Stokes/Large Eddy Simulation (RANS/LES) CFD simulations are performed in the inertial frame, including dynamic moving grids, using a higher-order accurate finite difference discretization on structured overlapping grids. A higher-order accurate free-stream preserving metric discretization with discrete enforcement of the Geometric Conservation Law (GCL) on moving curvilinear grids is used to create an accurate, efficient, and stable numerical scheme. The aeroacoustic analysis is based on a permeable surface Ffowcs Williams-Hawkings (FW-H) approach, evaluated in the frequency domain. A time-step sensitivity study was performed using only the forward row of blades to determine an adequate time-step. The numerical approach is validated against existing wind tunnel measurements.

Local numerical modelling of ultrasonic guided waves in linear and nonlinear media

NASA Astrophysics Data System (ADS)

Packo, Pawel; Radecki, Rafal; Kijanka, Piotr; Staszewski, Wieslaw J.; Uhl, Tadeusz; Leamy, Michael J.

2017-04-01

Nonlinear ultrasonic techniques provide improved damage sensitivity compared to linear approaches. The combination of attractive properties of guided waves, such as Lamb waves, with unique features of higher harmonic generation provides great potential for characterization of incipient damage, particularly in plate-like structures. Nonlinear ultrasonic structural health monitoring techniques use interrogation signals at frequencies other than the excitation frequency to detect changes in structural integrity. Signal processing techniques used in non-destructive evaluation are frequently supported by modeling and numerical simulations in order to facilitate problem solution. This paper discusses known and newly-developed local computational strategies for simulating elastic waves, and attempts characterization of their numerical properties in the context of linear and nonlinear media. A hybrid numerical approach combining advantages of the Local Interaction Simulation Approach (LISA) and Cellular Automata for Elastodynamics (CAFE) is proposed for unique treatment of arbitrary strain-stress relations. The iteration equations of the method are derived directly from physical principles employing stress and displacement continuity, leading to an accurate description of the propagation in arbitrarily complex media. Numerical analysis of guided wave propagation, based on the newly developed hybrid approach, is presented and discussed in the paper for linear and nonlinear media. Comparisons to Finite Elements (FE) are also discussed.

High-order finite-volume solutions of the steady-state advection-diffusion equation with nonlinear Robin boundary conditions

NASA Astrophysics Data System (ADS)

Lin, Zhi; Zhang, Qinghai

2017-09-01

We propose high-order finite-volume schemes for numerically solving the steady-state advection-diffusion equation with nonlinear Robin boundary conditions. Although the original motivation comes from a mathematical model of blood clotting, the nonlinear boundary conditions may also apply to other scientific problems. The main contribution of this work is a generic algorithm for generating third-order, fourth-order, and even higher-order explicit ghost-filling formulas to enforce nonlinear Robin boundary conditions in multiple dimensions. Under the framework of finite volume methods, this appears to be the first algorithm of its kind. Numerical experiments on boundary value problems show that the proposed fourth-order formula can be much more accurate and efficient than a simple second-order formula. Furthermore, the proposed ghost-filling formulas may also be useful for solving other partial differential equations.

Non-verbal numerical cognition: from reals to integers.

PubMed

Gallistel; Gelman

2000-02-01

Data on numerical processing by verbal (human) and non-verbal (animal and human) subjects are integrated by the hypothesis that a non-verbal counting process represents discrete (countable) quantities by means of magnitudes with scalar variability. These appear to be identical to the magnitudes that represent continuous (uncountable) quantities such as duration. The magnitudes representing countable quantity are generated by a discrete incrementing process, which defines next magnitudes and yields a discrete ordering. In the case of continuous quantities, the continuous accumulation process does not define next magnitudes, so the ordering is also continuous ('dense'). The magnitudes representing both countable and uncountable quantity are arithmetically combined in, for example, the computation of the income to be expected from a foraging patch. Thus, on the hypothesis presented here, the primitive machinery for arithmetic processing works with real numbers (magnitudes).

Numerical Simulation of Cast Distortion in Gas Turbine Engine Components

NASA Astrophysics Data System (ADS)

Inozemtsev, A. A.; Dubrovskaya, A. S.; Dongauser, K. A.; Trufanov, N. A.

2015-06-01

In this paper the process of multiple airfoilvanes manufacturing through investment casting is considered. The mathematical model of the full contact problem is built to determine stress strain state in a cast during the process of solidification. Studies are carried out in viscoelastoplastic statement. Numerical simulation of the explored process is implemented with ProCASTsoftware package. The results of simulation are compared with the real production process. By means of computer analysis the optimization of technical process parameters is done in order to eliminate the defect of cast walls thickness variation.

Higher-order awareness, misrepresentation and function

PubMed Central

Rosenthal, David

2012-01-01

Conscious mental states are states we are in some way aware of. I compare higher-order theories of consciousness, which explain consciousness by appeal to such higher-order awareness (HOA), and first-order theories, which do not, and I argue that higher-order theories have substantial explanatory advantages. The higher-order nature of our awareness of our conscious states suggests an analogy with the metacognition that figures in the regulation of psychological processes and behaviour. I argue that, although both consciousness and metacognition involve higher-order psychological states, they have little more in common. One thing they do share is the possibility of misrepresentation; just as metacognitive processing can misrepresent one's cognitive states and abilities, so the HOA in virtue of which one's mental states are conscious can, and sometimes does, misdescribe those states. A striking difference between the two, however, has to do with utility for psychological processing. Metacognition has considerable benefit for psychological processing; in contrast, it is unlikely that there is much, if any, utility to mental states' being conscious over and above the utility those states have when they are not conscious. PMID:22492758

Assessment of natural attenuation of aromatic hydrocarbons in groundwater near a former manufactured-gas plant, South Carolina, USA

USGS Publications Warehouse

Landmeyer, J.E.; Chapelle, F.H.; Petkewich, M.D.; Bradley, P.M.

1998-01-01

Shallow, anaerobic groundwater near a former manufactured-gas plant (MGP) in Charleston, South Carolina, USA, contains mono- and polycyclic aromatic hydrocarbons (MAHs and PAHs, respectively). Between 1994 and 1997, a combination of field, laboratory, and numerical-flow and transport-model investigations were made to assess natural attenuation processes affecting MAH and PAH distributions. This assessment included determination of adsorption coefficients (K(ad)) and first-order biodegradation rate constants (K(bio)) using aquifer material from the MGP site and adjacent properties. Naphthalene adsorption (K(ad) = 1.35 x 10-7 m3/mg) to aquifer sediments was higher than toluene adsorption (K(ad) = 9.34 x 10-10 m3/mg), suggesting preferential toluene transport relative to naphthalene. However, toluene and benzene distributions measured in January 1994 were smaller than the naphthalene distribution. This scenario can be explained, in part, by the differences between biodegradation rates of the compounds. Aerobic first-order rate constants of 14C-toluene, 14C-benzene, and 14C-naphthalene degradation were similar (-0.84, -0.03, and 0.88 day-1, respectively), but anaerobic rate constants were higher for toluene and benzene (-0.002 and -0.00014 day-1, respectively) than for naphthalene (-0.000046 day-1). Both areal and cross-sectional numerical simulations were used to test the hypothesis suggested by these rate differences that MAH compounds will be contained relative to PAHs. Predictive simulations indicated that the distributions of toluene and benzene reach steady-state conditions before groundwater flow lines discharge to an adjacent surface-water body, but do discharge low concentrations of naphthalene. Numerical predictions were 'audited' by measuring concentrations of naphthalene, toluene, and benzene at the site in early 1997. Measured naphthalene and toluene concentrations were substantially reduced and the areal extent of contamination smaller than was both observed in January 1994 and predicted for 1997. Measured 1997 benzene concentrations and distribution were shown to be relatively unchanged from those measured in 1994, and similar to predictions for 1997.The natural attenuation processes affecting mono- and polycyclic aromatic hydrocarbons (MAHs and PAHs, respectively) distributions in groundwater near a former manufactured-gas plant in South Carolina, USA was evaluated. This assessment included determination of adsorption coefficients and first-order biodegradation rate constants. Detailed results obtained in the study are presented.

[The functional independence of lexical numeric knowledge and the representation of magnitude: evidence from one case].

PubMed

Salguero-Alcañiz, M P; Lorca-Marín, J A; Alameda-Bailén, J R

The ultimate purpose of cognitive neuropsychology is to find out how normal cognitive processes work. To this end, it studies subjects who have suffered brain damage but who, until their accident, were competent in the skills that are later to become the object of study. It is therefore necessary to study patients who have difficulty in processing numbers and in calculating in order to further our knowledge of these processes in the normal population. Our aim was to analyse the relationships between the different cognitive processes involved in numeric knowledge. We studied the case of a female patient who suffered an ischemic infarct in the perisylvian region, on both a superficial and deep level. She presented predominantly expressive mixed aphasia and predominantly brachial hemiparesis. Numeric processing and calculation were evaluated. The patient still had her lexical numeric knowledge but her quantitative numeric knowledge was impaired. These alterations in the quantitative numeric knowledge are evidenced by the difficulties the patient had in numeric comprehension tasks, as well as the severe impairments displayed in calculation. These findings allow us to conclude that quantitative numeric knowledge is functionally independent of lexical or non-quantitative numeric knowledge. From this functional autonomy, a possible structural independence can be inferred.

From h to p efficiently: optimal implementation strategies for explicit time-dependent problems using the spectral/hp element method

PubMed Central

Bolis, A; Cantwell, C D; Kirby, R M; Sherwin, S J

2014-01-01

We investigate the relative performance of a second-order Adams–Bashforth scheme and second-order and fourth-order Runge–Kutta schemes when time stepping a 2D linear advection problem discretised using a spectral/hp element technique for a range of different mesh sizes and polynomial orders. Numerical experiments explore the effects of short (two wavelengths) and long (32 wavelengths) time integration for sets of uniform and non-uniform meshes. The choice of time-integration scheme and discretisation together fixes a CFL limit that imposes a restriction on the maximum time step, which can be taken to ensure numerical stability. The number of steps, together with the order of the scheme, affects not only the runtime but also the accuracy of the solution. Through numerical experiments, we systematically highlight the relative effects of spatial resolution and choice of time integration on performance and provide general guidelines on how best to achieve the minimal execution time in order to obtain a prescribed solution accuracy. The significant role played by higher polynomial orders in reducing CPU time while preserving accuracy becomes more evident, especially for uniform meshes, compared with what has been typically considered when studying this type of problem.© 2014. The Authors. International Journal for Numerical Methods in Fluids published by John Wiley & Sons, Ltd. PMID:25892840

Processing ordinality and quantity: the case of developmental dyscalculia.

PubMed

Rubinsten, Orly; Sury, Dana

2011-01-01

In contrast to quantity processing, up to date, the nature of ordinality has received little attention from researchers despite the fact that both quantity and ordinality are embodied in numerical information. Here we ask if there are two separate core systems that lie at the foundations of numerical cognition: (1) the traditionally and well accepted numerical magnitude system but also (2) core system for representing ordinal information. We report two novel experiments of ordinal processing that explored the relation between ordinal and numerical information processing in typically developing adults and adults with developmental dyscalculia (DD). Participants made "ordered" or "non-ordered" judgments about 3 groups of dots (non-symbolic numerical stimuli; in Experiment 1) and 3 numbers (symbolic task: Experiment 2). In contrast to previous findings and arguments about quantity deficit in DD participants, when quantity and ordinality are dissociated (as in the current tasks), DD participants exhibited a normal ratio effect in the non-symbolic ordinal task. They did not show, however, the ordinality effect. Ordinality effect in DD appeared only when area and density were randomized, but only in the descending direction. In the symbolic task, the ordinality effect was modulated by ratio and direction in both groups. These findings suggest that there might be two separate cognitive representations of ordinal and quantity information and that linguistic knowledge may facilitate estimation of ordinal information.

Conceiving processes in atmospheric models-General equations, subscale parameterizations, and 'superparameterizations'

NASA Astrophysics Data System (ADS)

Gramelsberger, Gabriele

The scientific understanding of atmospheric processes has been rooted in the mechanical and physical view of nature ever since dynamic meteorology gained ground in the late 19th century. Conceiving the atmosphere as a giant 'air mass circulation engine' entails applying hydro- and thermodynamical theory to the subject in order to describe the atmosphere's behaviour on small scales. But when it comes to forecasting, it turns out that this view is far too complex to be computed. The limitation of analytical methods precludes an exact solution, forcing scientists to make use of numerical simulation. However, simulation introduces two prerequisites to meteorology: First, the partitioning of the theoretical view into two parts-the large-scale behaviour of the atmosphere, and the effects of smaller-scale processes on this large-scale behaviour, so-called parametrizations; and second, the dependency on computational power in order to achieve a higher resolution. The history of today's atmospheric circulation modelling can be reconstructed as the attempt to improve the handling of these basic constraints. It can be further seen as the old schism between theory and application under new circumstances, which triggers a new discussion about the question of how processes may be conceived in atmospheric modelling.

Explosive percolation on directed networks due to monotonic flow of activity

NASA Astrophysics Data System (ADS)

Waagen, Alex; D'Souza, Raissa M.; Lu, Tsai-Ching

2017-07-01

An important class of real-world networks has directed edges, and in addition, some rank ordering on the nodes, for instance the popularity of users in online social networks. Yet, nearly all research related to explosive percolation has been restricted to undirected networks. Furthermore, information on such rank-ordered networks typically flows from higher-ranked to lower-ranked individuals, such as follower relations, replies, and retweets on Twitter. Here we introduce a simple percolation process on an ordered, directed network where edges are added monotonically with respect to the rank ordering. We show with a numerical approach that the emergence of a dominant strongly connected component appears to be discontinuous. Large-scale connectivity occurs at very high density compared with most percolation processes, and this holds not just for the strongly connected component structure but for the weakly connected component structure as well. We present analysis with branching processes, which explains this unusual behavior and gives basic intuition for the underlying mechanisms. We also show that before the emergence of a dominant strongly connected component, multiple giant strongly connected components may exist simultaneously. By adding a competitive percolation rule with a small bias to link uses of similar rank, we show this leads to formation of two distinct components, one of high-ranked users, and one of low-ranked users, with little flow between the two components.

Study of Nonlinear Propagation of Ultrashort Laser Pulses and Its Application to Harmonic Generation

NASA Astrophysics Data System (ADS)

Weerawarne, Darshana L.

Laser filamentation, which is one of the exotic nonlinear optical phenomena, is self-guidance of high-power laser beams due to the dynamic balance between the optical Kerr effect (self-focusing) and other nonlinear effects such as plasma defocusing. It has many applications including supercontinuum generation (SCG), high-order harmonic generation (HHG), lightning guiding, stand-off sensing, and rain making. The main focus of this work is on studying odd-order harmonic generation (HG) (i.e., 3o, 5o, 7o, etc., where o is the angular frequency) in centrosymmetric media while a high-power, ultrashort harmonic-driving pulse undergoes nonlinear propagation such as laser filamentation. The investigation of highly-controversial nonlinear indices of refraction by measuring low-order HG in air is carried out. Furthermore, time-resolved (i.e., pump-probe) experiments and significant harmonic enhancements are presented and a novel HG mechanism based on higher-order nonlinearities is proposed to explain the experimental results. C/C++ numerical simulations are used to solve the nonlinear Schrodinger equation (NLSE) which supports the experimental findings. Another project which I have performed is selective sintering using lasers. Short-pulse lasers provide a fascinating tool for material processing, especially when the conventional oven-based techniques fail to process flexible materials for smart energy/electronics applications. I present experimental and theoretical studies on laser processing of nanoparticle-coated flexible materials, aiming to fabricate flexible electronic devices.

Approximate optimal guidance for the advanced launch system

NASA Technical Reports Server (NTRS)

Feeley, T. S.; Speyer, J. L.

1993-01-01

A real-time guidance scheme for the problem of maximizing the payload into orbit subject to the equations of motion for a rocket over a spherical, non-rotating earth is presented. An approximate optimal launch guidance law is developed based upon an asymptotic expansion of the Hamilton - Jacobi - Bellman or dynamic programming equation. The expansion is performed in terms of a small parameter, which is used to separate the dynamics of the problem into primary and perturbation dynamics. For the zeroth-order problem the small parameter is set to zero and a closed-form solution to the zeroth-order expansion term of Hamilton - Jacobi - Bellman equation is obtained. Higher-order terms of the expansion include the effects of the neglected perturbation dynamics. These higher-order terms are determined from the solution of first-order linear partial differential equations requiring only the evaluation of quadratures. This technique is preferred as a real-time, on-line guidance scheme to alternative numerical iterative optimization schemes because of the unreliable convergence properties of these iterative guidance schemes and because the quadratures needed for the approximate optimal guidance law can be performed rapidly and by parallel processing. Even if the approximate solution is not nearly optimal, when using this technique the zeroth-order solution always provides a path which satisfies the terminal constraints. Results for two-degree-of-freedom simulations are presented for the simplified problem of flight in the equatorial plane and compared to the guidance scheme generated by the shooting method which is an iterative second-order technique.

Numerical Simulation of Pulse Detonation Rocket-Induced MHD Ejector (PDRIME) Concepts for Advanced Propulsion Systems

DTIC Science & Technology

2012-02-28

Coupling in Detonation Waves: 1D Dynamics”, Paper 89, 23rd International Colloquium on the Dynamics of Explosions and Reactive ...and temperature, and can be modeled as a constant volume reaction , which is more efficient than a constant pressure reaction . After the detonation ... kinetics , and flow processes using high order numerical methods. A fifth-order WENO (weighted essentially non -oscillatory12,13) scheme was used

Golay Complementary Waveforms in Reed–Müller Sequences for Radar Detection of Nonzero Doppler Targets

PubMed Central

Wang, Xuezhi; Huang, Xiaotao; Suvorova, Sofia; Moran, Bill

2018-01-01

Golay complementary waveforms can, in theory, yield radar returns of high range resolution with essentially zero sidelobes. In practice, when deployed conventionally, while high signal-to-noise ratios can be achieved for static target detection, significant range sidelobes are generated by target returns of nonzero Doppler causing unreliable detection. We consider signal processing techniques using Golay complementary waveforms to improve radar detection performance in scenarios involving multiple nonzero Doppler targets. A signal processing procedure based on an existing, so called, Binomial Design algorithm that alters the transmission order of Golay complementary waveforms and weights the returns is proposed in an attempt to achieve an enhanced illumination performance. The procedure applies one of three proposed waveform transmission ordering algorithms, followed by a pointwise nonlinear processor combining the outputs of the Binomial Design algorithm and one of the ordering algorithms. The computational complexity of the Binomial Design algorithm and the three ordering algorithms are compared, and a statistical analysis of the performance of the pointwise nonlinear processing is given. Estimation of the areas in the Delay–Doppler map occupied by significant range sidelobes for given targets are also discussed. Numerical simulations for the comparison of the performances of the Binomial Design algorithm and the three ordering algorithms are presented for both fixed and randomized target locations. The simulation results demonstrate that the proposed signal processing procedure has a better detection performance in terms of lower sidelobes and higher Doppler resolution in the presence of multiple nonzero Doppler targets compared to existing methods. PMID:29324708

Higher and lowest order mixed finite element approximation of subsurface flow problems with solutions of low regularity

NASA Astrophysics Data System (ADS)

Bause, Markus

2008-02-01

In this work we study mixed finite element approximations of Richards' equation for simulating variably saturated subsurface flow and simultaneous reactive solute transport. Whereas higher order schemes have proved their ability to approximate reliably reactive solute transport (cf., e.g. [Bause M, Knabner P. Numerical simulation of contaminant biodegradation by higher order methods and adaptive time stepping. Comput Visual Sci 7;2004:61-78]), the Raviart- Thomas mixed finite element method ( RT0) with a first order accurate flux approximation is popular for computing the underlying water flow field (cf. [Bause M, Knabner P. Computation of variably saturated subsurface flow by adaptive mixed hybrid finite element methods. Adv Water Resour 27;2004:565-581, Farthing MW, Kees CE, Miller CT. Mixed finite element methods and higher order temporal approximations for variably saturated groundwater flow. Adv Water Resour 26;2003:373-394, Starke G. Least-squares mixed finite element solution of variably saturated subsurface flow problems. SIAM J Sci Comput 21;2000:1869-1885, Younes A, Mosé R, Ackerer P, Chavent G. A new formulation of the mixed finite element method for solving elliptic and parabolic PDE with triangular elements. J Comp Phys 149;1999:148-167, Woodward CS, Dawson CN. Analysis of expanded mixed finite element methods for a nonlinear parabolic equation modeling flow into variably saturated porous media. SIAM J Numer Anal 37;2000:701-724]). This combination might be non-optimal. Higher order techniques could increase the accuracy of the flow field calculation and thereby improve the prediction of the solute transport. Here, we analyse the application of the Brezzi- Douglas- Marini element ( BDM1) with a second order accurate flux approximation to elliptic, parabolic and degenerate problems whose solutions lack the regularity that is assumed in optimal order error analyses. For the flow field calculation a superiority of the BDM1 approach to the RT0 one is observed, which however is less significant for the accompanying solute transport.

Properties of quantum systems via diagonalization of transition amplitudes. II. Systematic improvements of short-time propagation

NASA Astrophysics Data System (ADS)

Vidanović, Ivana; Bogojević, Aleksandar; Balaž, Antun; Belić, Aleksandar

2009-12-01

In this paper, building on a previous analysis [I. Vidanović, A. Bogojević, and A. Belić, preceding paper, Phys. Rev. E 80, 066705 (2009)] of exact diagonalization of the space-discretized evolution operator for the study of properties of nonrelativistic quantum systems, we present a substantial improvement to this method. We apply recently introduced effective action approach for obtaining short-time expansion of the propagator up to very high orders to calculate matrix elements of space-discretized evolution operator. This improves by many orders of magnitude previously used approximations for discretized matrix elements and allows us to numerically obtain large numbers of accurate energy eigenvalues and eigenstates using numerical diagonalization. We illustrate this approach on several one- and two-dimensional models. The quality of numerically calculated higher-order eigenstates is assessed by comparison with semiclassical cumulative density of states.

Numerical orbit generators of artificial earth satellites

NASA Astrophysics Data System (ADS)

Kugar, H. K.; Dasilva, W. C. C.

1984-04-01

A numerical orbit integrator containing updatings and improvements relative to the previous ones that are being utilized by the Departmento de Mecanica Espacial e Controle (DMC), of INPE, besides incorporating newer modellings resulting from the skill acquired along the time is presented. Flexibility and modularity were taken into account in order to allow future extensions and modifications. Characteristics of numerical accuracy, processing quickness, memory saving as well as utilization aspects were also considered. User's handbook, whole program listing and qualitative analysis of accuracy, processing time and orbit perturbation effects were included as well.

Plasma-driven self-organization of Ni nanodot arrays on Si(100)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levchenko, I.; Ostrikov, K.; Diwan, K.

The results of the combined experimental and numerical study suggest that nonequilibrium plasma-driven self-organization leads to better size and positional uniformity of nickel nanodot arrays on a Si(100) surface compared with neutral gas-based processes under similar conditions. This phenomenon is explained by introducing the absorption zone patterns, whose areas relative to the small nanodot sizes become larger when the surface is charged. Our results suggest that strongly nonequilibrium and higher-complexity plasma systems can be used to improve ordering and size uniformity in nanodot arrays of various materials, a common and seemingly irresolvable problem in self-organized systems of small nanoparticles.

Application of high-order numerical schemes and Newton-Krylov method to two-phase drift-flux model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zou, Ling; Zhao, Haihua; Zhang, Hongbin

This study concerns the application and solver robustness of the Newton-Krylov method in solving two-phase flow drift-flux model problems using high-order numerical schemes. In our previous studies, the Newton-Krylov method has been proven as a promising solver for two-phase flow drift-flux model problems. However, these studies were limited to use first-order numerical schemes only. Moreover, the previous approach to treating the drift-flux closure correlations was later revealed to cause deteriorated solver convergence performance, when the mesh was highly refined, and also when higher-order numerical schemes were employed. In this study, a second-order spatial discretization scheme that has been tested withmore » two-fluid two-phase flow model was extended to solve drift-flux model problems. In order to improve solver robustness, and therefore efficiency, a new approach was proposed to treating the mean drift velocity of the gas phase as a primary nonlinear variable to the equation system. With this new approach, significant improvement in solver robustness was achieved. With highly refined mesh, the proposed treatment along with the Newton-Krylov solver were extensively tested with two-phase flow problems that cover a wide range of thermal-hydraulics conditions. Satisfactory convergence performances were observed for all test cases. Numerical verification was then performed in the form of mesh convergence studies, from which expected orders of accuracy were obtained for both the first-order and the second-order spatial discretization schemes. Finally, the drift-flux model, along with numerical methods presented, were validated with three sets of flow boiling experiments that cover different flow channel geometries (round tube, rectangular tube, and rod bundle), and a wide range of test conditions (pressure, mass flux, wall heat flux, inlet subcooling and outlet void fraction).« less

Application of high-order numerical schemes and Newton-Krylov method to two-phase drift-flux model

DOE PAGES

Zou, Ling; Zhao, Haihua; Zhang, Hongbin

2017-08-07

This study concerns the application and solver robustness of the Newton-Krylov method in solving two-phase flow drift-flux model problems using high-order numerical schemes. In our previous studies, the Newton-Krylov method has been proven as a promising solver for two-phase flow drift-flux model problems. However, these studies were limited to use first-order numerical schemes only. Moreover, the previous approach to treating the drift-flux closure correlations was later revealed to cause deteriorated solver convergence performance, when the mesh was highly refined, and also when higher-order numerical schemes were employed. In this study, a second-order spatial discretization scheme that has been tested withmore » two-fluid two-phase flow model was extended to solve drift-flux model problems. In order to improve solver robustness, and therefore efficiency, a new approach was proposed to treating the mean drift velocity of the gas phase as a primary nonlinear variable to the equation system. With this new approach, significant improvement in solver robustness was achieved. With highly refined mesh, the proposed treatment along with the Newton-Krylov solver were extensively tested with two-phase flow problems that cover a wide range of thermal-hydraulics conditions. Satisfactory convergence performances were observed for all test cases. Numerical verification was then performed in the form of mesh convergence studies, from which expected orders of accuracy were obtained for both the first-order and the second-order spatial discretization schemes. Finally, the drift-flux model, along with numerical methods presented, were validated with three sets of flow boiling experiments that cover different flow channel geometries (round tube, rectangular tube, and rod bundle), and a wide range of test conditions (pressure, mass flux, wall heat flux, inlet subcooling and outlet void fraction).« less

An efficient and accurate two-stage fourth-order gas-kinetic scheme for the Euler and Navier-Stokes equations

NASA Astrophysics Data System (ADS)

Pan, Liang; Xu, Kun; Li, Qibing; Li, Jiequan

2016-12-01

For computational fluid dynamics (CFD), the generalized Riemann problem (GRP) solver and the second-order gas-kinetic scheme (GKS) provide a time-accurate flux function starting from a discontinuous piecewise linear flow distributions around a cell interface. With the adoption of time derivative of the flux function, a two-stage Lax-Wendroff-type (L-W for short) time stepping method has been recently proposed in the design of a fourth-order time accurate method for inviscid flow [21]. In this paper, based on the same time-stepping method and the second-order GKS flux function [42], a fourth-order gas-kinetic scheme is constructed for the Euler and Navier-Stokes (NS) equations. In comparison with the formal one-stage time-stepping third-order gas-kinetic solver [24], the current fourth-order method not only reduces the complexity of the flux function, but also improves the accuracy of the scheme. In terms of the computational cost, a two-dimensional third-order GKS flux function takes about six times of the computational time of a second-order GKS flux function. However, a fifth-order WENO reconstruction may take more than ten times of the computational cost of a second-order GKS flux function. Therefore, it is fully legitimate to develop a two-stage fourth order time accurate method (two reconstruction) instead of standard four stage fourth-order Runge-Kutta method (four reconstruction). Most importantly, the robustness of the fourth-order GKS is as good as the second-order one. In the current computational fluid dynamics (CFD) research, it is still a difficult problem to extend the higher-order Euler solver to the NS one due to the change of governing equations from hyperbolic to parabolic type and the initial interface discontinuity. This problem remains distinctively for the hypersonic viscous and heat conducting flow. The GKS is based on the kinetic equation with the hyperbolic transport and the relaxation source term. The time-dependent GKS flux function provides a dynamic process of evolution from the kinetic scale particle free transport to the hydrodynamic scale wave propagation, which provides the physics for the non-equilibrium numerical shock structure construction to the near equilibrium NS solution. As a result, with the implementation of the fifth-order WENO initial reconstruction, in the smooth region the current two-stage GKS provides an accuracy of O ((Δx) 5 ,(Δt) 4) for the Euler equations, and O ((Δx) 5 ,τ2 Δt) for the NS equations, where τ is the time between particle collisions. Many numerical tests, including difficult ones for the Navier-Stokes solvers, have been used to validate the current method. Perfect numerical solutions can be obtained from the high Reynolds number boundary layer to the hypersonic viscous heat conducting flow. Following the two-stage time-stepping framework, the third-order GKS flux function can be used as well to construct a fifth-order method with the usage of both first-order and second-order time derivatives of the flux function. The use of time-accurate flux function may have great advantages on the development of higher-order CFD methods.

Numerical simulation of disperse particle flows on a graphics processing unit

NASA Astrophysics Data System (ADS)

Sierakowski, Adam J.

In both nature and technology, we commonly encounter solid particles being carried within fluid flows, from dust storms to sediment erosion and from food processing to energy generation. The motion of uncountably many particles in highly dynamic flow environments characterizes the tremendous complexity of such phenomena. While methods exist for the full-scale numerical simulation of such systems, current computational capabilities require the simplification of the numerical task with significant approximation using closure models widely recognized as insufficient. There is therefore a fundamental need for the investigation of the underlying physical processes governing these disperse particle flows. In the present work, we develop a new tool based on the Physalis method for the first-principles numerical simulation of thousands of particles (a small fraction of an entire disperse particle flow system) in order to assist in the search for new reduced-order closure models. We discuss numerous enhancements to the efficiency and stability of the Physalis method, which introduces the influence of spherical particles to a fixed-grid incompressible Navier-Stokes flow solver using a local analytic solution to the flow equations. Our first-principles investigation demands the modeling of unresolved length and time scales associated with particle collisions. We introduce a collision model alongside Physalis, incorporating lubrication effects and proposing a new nonlinearly damped Hertzian contact model. By reproducing experimental studies from the literature, we document extensive validation of the methods. We discuss the implementation of our methods for massively parallel computation using a graphics processing unit (GPU). We combine Eulerian grid-based algorithms with Lagrangian particle-based algorithms to achieve computational throughput up to 90 times faster than the legacy implementation of Physalis for a single central processing unit. By avoiding all data communication between the GPU and the host system during the simulation, we utilize with great efficacy the GPU hardware with which many high performance computing systems are currently equipped. We conclude by looking forward to the future of Physalis with multi-GPU parallelization in order to perform resolved disperse flow simulations of more than 100,000 particles and further advance the development of reduced-order closure models.

Differences in arithmetic performance between Chinese and German adults are accompanied by differences in processing of non-symbolic numerical magnitude

PubMed Central

Lonnemann, Jan; Li, Su; Zhao, Pei; Li, Peng; Linkersdörfer, Janosch; Lindberg, Sven; Hasselhorn, Marcus; Yan, Song

2017-01-01

Human beings are assumed to possess an approximate number system (ANS) dedicated to extracting and representing approximate numerical magnitude information. The ANS is assumed to be fundamental to arithmetic learning and has been shown to be associated with arithmetic performance. It is, however, still a matter of debate whether better arithmetic skills are reflected in the ANS. To address this issue, Chinese and German adults were compared regarding their performance in simple arithmetic tasks and in a non-symbolic numerical magnitude comparison task. Chinese participants showed a better performance in solving simple arithmetic tasks and faster reaction times in the non-symbolic numerical magnitude comparison task without making more errors than their German peers. These differences in performance could not be ascribed to differences in general cognitive abilities. Better arithmetic skills were thus found to be accompanied by a higher speed of retrieving non-symbolic numerical magnitude knowledge but not by a higher precision of non-symbolic numerical magnitude representations. The group difference in the speed of retrieving non-symbolic numerical magnitude knowledge was fully mediated by the performance in arithmetic tasks, suggesting that arithmetic skills shape non-symbolic numerical magnitude processing skills. PMID:28384191

Fast large scale structure perturbation theory using one-dimensional fast Fourier transforms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmittfull, Marcel; Vlah, Zvonimir; McDonald, Patrick

The usual fluid equations describing the large-scale evolution of mass density in the universe can be written as local in the density, velocity divergence, and velocity potential fields. As a result, the perturbative expansion in small density fluctuations, usually written in terms of convolutions in Fourier space, can be written as a series of products of these fields evaluated at the same location in configuration space. Based on this, we establish a new method to numerically evaluate the 1-loop power spectrum (i.e., Fourier transform of the 2-point correlation function) with one-dimensional fast Fourier transforms. This is exact and a fewmore » orders of magnitude faster than previously used numerical approaches. Numerical results of the new method are in excellent agreement with the standard quadrature integration method. This fast model evaluation can in principle be extended to higher loop order where existing codes become painfully slow. Our approach follows by writing higher order corrections to the 2-point correlation function as, e.g., the correlation between two second-order fields or the correlation between a linear and a third-order field. These are then decomposed into products of correlations of linear fields and derivatives of linear fields. In conclusion, the method can also be viewed as evaluating three-dimensional Fourier space convolutions using products in configuration space, which may also be useful in other contexts where similar integrals appear.« less

Fast large scale structure perturbation theory using one-dimensional fast Fourier transforms

DOE PAGES

Schmittfull, Marcel; Vlah, Zvonimir; McDonald, Patrick

2016-05-01

The usual fluid equations describing the large-scale evolution of mass density in the universe can be written as local in the density, velocity divergence, and velocity potential fields. As a result, the perturbative expansion in small density fluctuations, usually written in terms of convolutions in Fourier space, can be written as a series of products of these fields evaluated at the same location in configuration space. Based on this, we establish a new method to numerically evaluate the 1-loop power spectrum (i.e., Fourier transform of the 2-point correlation function) with one-dimensional fast Fourier transforms. This is exact and a fewmore » orders of magnitude faster than previously used numerical approaches. Numerical results of the new method are in excellent agreement with the standard quadrature integration method. This fast model evaluation can in principle be extended to higher loop order where existing codes become painfully slow. Our approach follows by writing higher order corrections to the 2-point correlation function as, e.g., the correlation between two second-order fields or the correlation between a linear and a third-order field. These are then decomposed into products of correlations of linear fields and derivatives of linear fields. In conclusion, the method can also be viewed as evaluating three-dimensional Fourier space convolutions using products in configuration space, which may also be useful in other contexts where similar integrals appear.« less

Two-dimensional atmospheric transport and chemistry model - Numerical experiments with a new advection algorithm

NASA Technical Reports Server (NTRS)

Shia, Run-Lie; Ha, Yuk Lung; Wen, Jun-Shan; Yung, Yuk L.

1990-01-01

Extensive testing of the advective scheme proposed by Prather (1986) has been carried out in support of the California Institute of Technology-Jet Propulsion Laboratory two-dimensional model of the middle atmosphere. The original scheme is generalized to include higher-order moments. In addition, it is shown how well the scheme works in the presence of chemistry as well as eddy diffusion. Six types of numerical experiments including simple clock motion and pure advection in two dimensions have been investigated in detail. By comparison with analytic solutions, it is shown that the new algorithm can faithfully preserve concentration profiles, has essentially no numerical diffusion, and is superior to a typical fourth-order finite difference scheme.

The effect of mathematics anxiety on the processing of numerical magnitude.

PubMed

Maloney, Erin A; Ansari, Daniel; Fugelsang, Jonathan A

2011-01-01

In an effort to understand the origins of mathematics anxiety, we investigated the processing of symbolic magnitude by high mathematics-anxious (HMA) and low mathematics-anxious (LMA) individuals by examining their performance on two variants of the symbolic numerical comparison task. In two experiments, a numerical distance by mathematics anxiety (MA) interaction was obtained, demonstrating that the effect of numerical distance on response times was larger for HMA than for LMA individuals. These data support the claim that HMA individuals have less precise representations of numerical magnitude than their LMA peers, suggesting that MA is associated with low-level numerical deficits that compromise the development of higher level mathematical skills.

A technique for increasing the accuracy of the numerical inversion of the Laplace transform with applications

NASA Technical Reports Server (NTRS)

Berger, B. S.; Duangudom, S.

1973-01-01

A technique is introduced which extends the range of useful approximation of numerical inversion techniques to many cycles of an oscillatory function without requiring either the evaluation of the image function for many values of s or the computation of higher-order terms. The technique consists in reducing a given initial value problem defined over some interval into a sequence of initial value problems defined over a set of subintervals. Several numerical examples demonstrate the utility of the method.

MATLAB-based algorithm to estimate depths of isolated thin dike-like sources using higher-order horizontal derivatives of magnetic anomalies.

PubMed

Ekinci, Yunus Levent

2016-01-01

This paper presents an easy-to-use open source computer algorithm (code) for estimating the depths of isolated single thin dike-like source bodies by using numerical second-, third-, and fourth-order horizontal derivatives computed from observed magnetic anomalies. The approach does not require a priori information and uses some filters of successive graticule spacings. The computed higher-order horizontal derivative datasets are used to solve nonlinear equations for depth determination. The solutions are independent from the magnetization and ambient field directions. The practical usability of the developed code, designed in MATLAB R2012b (MathWorks Inc.), was successfully examined using some synthetic simulations with and without noise. The algorithm was then used to estimate the depths of some ore bodies buried in different regions (USA, Sweden, and Canada). Real data tests clearly indicated that the obtained depths are in good agreement with those of previous studies and drilling information. Additionally, a state-of-the-art inversion scheme based on particle swarm optimization produced comparable results to those of the higher-order horizontal derivative analyses in both synthetic and real anomaly cases. Accordingly, the proposed code is verified to be useful in interpreting isolated single thin dike-like magnetized bodies and may be an alternative processing technique. The open source code can be easily modified and adapted to suit the benefits of other researchers.

Explicit filtering in large eddy simulation using a discontinuous Galerkin method

NASA Astrophysics Data System (ADS)

Brazell, Matthew J.

The discontinuous Galerkin (DG) method is a formulation of the finite element method (FEM). DG provides the ability for a high order of accuracy in complex geometries, and allows for highly efficient parallelization algorithms. These attributes make the DG method attractive for solving the Navier-Stokes equations for large eddy simulation (LES). The main goal of this work is to investigate the feasibility of adopting an explicit filter in the numerical solution of the Navier-Stokes equations with DG. Explicit filtering has been shown to increase the numerical stability of under-resolved simulations and is needed for LES with dynamic sub-grid scale (SGS) models. The explicit filter takes advantage of DG's framework where the solution is approximated using a polyno- mial basis where the higher modes of the solution correspond to a higher order polynomial basis. By removing high order modes, the filtered solution contains low order frequency content much like an explicit low pass filter. The explicit filter implementation is tested on a simple 1-D solver with an initial condi- tion that has some similarity to turbulent flows. The explicit filter does restrict the resolution as well as remove accumulated energy in the higher modes from aliasing. However, the ex- plicit filter is unable to remove numerical errors causing numerical dissipation. A second test case solves the 3-D Navier-Stokes equations of the Taylor-Green vortex flow (TGV). The TGV is useful for SGS model testing because it is initially laminar and transitions into a fully turbulent flow. The SGS models investigated include the constant coefficient Smagorinsky model, dynamic Smagorinsky model, and dynamic Heinz model. The constant coefficient Smagorinsky model is over dissipative, this is generally not desirable however it does add stability. The dynamic Smagorinsky model generally performs better, especially during the laminar-turbulent transition region as expected. The dynamic Heinz model which is based on an improved model, handles the laminar-turbulent transition region well while also showing additional robustness.

Numerical modeling of magnetic moments for UXO applications

USGS Publications Warehouse

Sanchez, V.; Li, Y.; Nabighian, M.; Wright, D.

2006-01-01

The surface magnetic anomaly observed in UXO clearance is mainly dipolar and, consequently, the dipole is the only magnetic moment regularly recovered in UXO applications. The dipole moment contains information about intensity of magnetization but lacks information about shape. In contrast, higher-order moments, such as quadrupole and octupole, encode asymmetry properties of the magnetization distribution within the buried targets. In order to improve our understanding of magnetization distribution within UXO and non-UXO objects and its potential utility in UXO clearance, we present a 3D numerical modeling study for highly susceptible metallic objects. The basis for the modeling is the solution of a nonlinear integral equation describing magnetization within isolated objects. A solution for magnetization distribution then allows us to compute magnetic moments of the object, analyze their relationships, and provide a depiction of the surface anomaly produced by different moments within the object. Our modeling results show significant high-order moments for more asymmetric objects situated at depths typical of UXO burial, and suggest that the increased relative contribution to magnetic gradient data from these higher-order moments may provide a practical tool for improved UXO discrimination.

PDF turbulence modeling and DNS

NASA Technical Reports Server (NTRS)

Hsu, A. T.

1992-01-01

The problem of time discontinuity (or jump condition) in the coalescence/dispersion (C/D) mixing model is addressed in probability density function (pdf). A C/D mixing model continuous in time is introduced. With the continuous mixing model, the process of chemical reaction can be fully coupled with mixing. In the case of homogeneous turbulence decay, the new model predicts a pdf very close to a Gaussian distribution, with finite higher moments also close to that of a Gaussian distribution. Results from the continuous mixing model are compared with both experimental data and numerical results from conventional C/D models. The effect of Coriolis forces on compressible homogeneous turbulence is studied using direct numerical simulation (DNS). The numerical method used in this study is an eight order compact difference scheme. Contrary to the conclusions reached by previous DNS studies on incompressible isotropic turbulence, the present results show that the Coriolis force increases the dissipation rate of turbulent kinetic energy, and that anisotropy develops as the Coriolis force increases. The Taylor-Proudman theory does apply since the derivatives in the direction of the rotation axis vanishes rapidly. A closer analysis reveals that the dissipation rate of the incompressible component of the turbulent kinetic energy indeed decreases with a higher rotation rate, consistent with incompressible flow simulations (Bardina), while the dissipation rate of the compressible part increases; the net gain is positive. Inertial waves are observed in the simulation results.

Neoclassical transport including collisional nonlinearity.

PubMed

Candy, J; Belli, E A

2011-06-10

In the standard δf theory of neoclassical transport, the zeroth-order (Maxwellian) solution is obtained analytically via the solution of a nonlinear equation. The first-order correction δf is subsequently computed as the solution of a linear, inhomogeneous equation that includes the linearized Fokker-Planck collision operator. This equation admits analytic solutions only in extreme asymptotic limits (banana, plateau, Pfirsch-Schlüter), and so must be solved numerically for realistic plasma parameters. Recently, numerical codes have appeared which attempt to compute the total distribution f more accurately than in the standard ordering by retaining some nonlinear terms related to finite-orbit width, while simultaneously reusing some form of the linearized collision operator. In this work we show that higher-order corrections to the distribution function may be unphysical if collisional nonlinearities are ignored.

Energy-momentum conserving higher-order time integration of nonlinear dynamics of finite elastic fiber-reinforced continua

NASA Astrophysics Data System (ADS)

Erler, Norbert; Groß, Michael

2015-05-01

Since many years the relevance of fibre-reinforced polymers is steadily increasing in fields of engineering, especially in aircraft and automotive industry. Due to the high strength in fibre direction, but the possibility of lightweight construction, these composites replace more and more traditional materials as metals. Fibre-reinforced polymers are often manufactured from glass or carbon fibres as attachment parts or from steel or nylon cord as force transmission parts. Attachment parts are mostly subjected to small strains, but force transmission parts usually suffer large deformations in at least one direction. Here, a geometrically nonlinear formulation is necessary. Typical examples are helicopter rotor blades, where the fibres have the function to stabilize the structure in order to counteract large centrifugal forces. For long-run analyses of rotor blade deformations, we have to apply numerically stable time integrators for anisotropic materials. This paper presents higher-order accurate and numerically stable time stepping schemes for nonlinear elastic fibre-reinforced continua with anisotropic stress behaviour.

Performance of Low Dissipative High Order Shock-Capturing Schemes for Shock-Turbulence Interactions

NASA Technical Reports Server (NTRS)

Sandham, N. D.; Yee, H. C.

1998-01-01

Accurate and efficient direct numerical simulation of turbulence in the presence of shock waves represents a significant challenge for numerical methods. The objective of this paper is to evaluate the performance of high order compact and non-compact central spatial differencing employing total variation diminishing (TVD) shock-capturing dissipations as characteristic based filters for two model problems combining shock wave and shear layer phenomena. A vortex pairing model evaluates the ability of the schemes to cope with shear layer instability and eddy shock waves, while a shock wave impingement on a spatially-evolving mixing layer model studies the accuracy of computation of vortices passing through a sequence of shock and expansion waves. A drastic increase in accuracy is observed if a suitable artificial compression formulation is applied to the TVD dissipations. With this modification to the filter step the fourth-order non-compact scheme shows improved results in comparison to second-order methods, while retaining the good shock resolution of the basic TVD scheme. For this characteristic based filter approach, however, the benefits of compact schemes or schemes with higher than fourth order are not sufficient to justify the higher complexity near the boundary and/or the additional computational cost.

Holographic Van der Waals phase transition of the higher-dimensional electrically charged hairy black hole

NASA Astrophysics Data System (ADS)

Li, Hui-Ling; Feng, Zhong-Wen; Zu, Xiao-Tao

2018-01-01

With motivation by holography, employing black hole entropy, two-point connection function and entanglement entropy, we show that, for the higher-dimensional Anti-de Sitter charged hairy black hole in the fixed charged ensemble, a Van der Waals-like phase transition can be observed. Furthermore, based on the Maxwell equal-area construction, we check numerically the equal-area law for a first order phase transition in order to further characterize the Van der Waals-like phase transition.

Extremely Fast Numerical Integration of Ocean Surface Wave Dynamics: Building Blocks for a Higher Order Method

DTIC Science & Technology

2006-09-30

equation known as the Kadomtsev - Petviashvili (KP) equation ): (ηt + coηx +αηηx + βη )x +γηyy = 0 (4) where γ = co / 2 . The KdV equation ...using the spectral formulation of the Kadomtsev - Petviashvili equation , a standard equation for nonlinear, shallow water wave dynamics that is a... Petviashvili and nonlinear Schroedinger equations and higher order corrections have been developed as prerequisites to coding the Boussinesq and Euler

On Illicit Economic Relations in the Sphere of Higher Education

ERIC Educational Resources Information Center

Shevchenko, I. O.; Gavrilov, A. A.

2007-01-01

These days, processes of corruption in colleges and universities are vividly reflected in the mass consciousness. In spite of numerous reports about these processes in the mass media, however, there are no exact data about the prevalence of bribery in higher education. Just what phenomena of bribery exist in higher education, and to what extent?…

Advanced control of dissolved oxygen concentration in fed batch cultures during recombinant protein production.

PubMed

Kuprijanov, A; Gnoth, S; Simutis, R; Lübbert, A

2009-02-01

Design and experimental validation of advanced pO(2) controllers for fermentation processes operated in the fed-batch mode are described. In most situations, the presented controllers are able to keep the pO(2) in fermentations for recombinant protein productions exactly on the desired value. The controllers are based on the gain-scheduling approach to parameter-adaptive proportional-integral controllers. In order to cope with the most often appearing distortions, the basic gain-scheduling feedback controller was complemented with a feedforward control component. This feedforward/feedback controller significantly improved pO(2) control. By means of numerical simulations, the controller behavior was tested and its parameters were determined. Validation runs were performed with three Escherichia coli strains producing different recombinant proteins. It is finally shown that the new controller leads to significant improvements in the signal-to-noise ratio of other key process variables and, thus, to a higher process quality.

Testing of New Materials and Computer Aided Optimization of Process Parameters and Clamping Device During Predevelopment of Laser Welding Processes

NASA Astrophysics Data System (ADS)

Weidinger, Peter; Günther, Kay; Fitzel, Martin; Logvinov, Ruslan; Ilin, Alexander; Ploshikhin, Vasily; Hugger, Florian; Mann, Vincent; Roth, Stephan; Schmidt, Michael

The necessity for weight reduction in motor vehicles in order to save fuel consumption pushes automotive suppliers to use materials of higher strength. Due to their excellent crash behavior high strength steels are increasingly applied in various structures. In this paper some predevelopment steps for a material change from a micro alloyed to dual phase and complex phase steels of a T-joint assembly are displayed. Initially the general weldability of the materials regarding pore formation, hardening in the heat affected zone and hot cracking susceptibility is discussed. After this basic investigation, the computer aided design optimization of a clamping device is shown, in which influences of the clamping jaw, the welding position and the clamping forces upon weld quality are presented. Finally experimental results of the welding process are displayed, which validate the numerical simulation.

Modelling river bank erosion processes and mass failure mechanisms using 2-D depth averaged numerical model

NASA Astrophysics Data System (ADS)

Die Moran, Andres; El kadi Abderrezzak, Kamal; Tassi, Pablo; Herouvet, Jean-Michel

2014-05-01

Bank erosion is a key process that may cause a large number of economic and environmental problems (e.g. land loss, damage to structures and aquatic habitat). Stream bank erosion (toe erosion and mass failure) represents an important form of channel morphology changes and a significant source of sediment. With the advances made in computational techniques, two-dimensional (2-D) numerical models have become valuable tools for investigating flow and sediment transport in open channels at large temporal and spatial scales. However, the implementation of mass failure process in 2D numerical models is still a challenging task. In this paper, a simple, innovative algorithm is implemented in the Telemac-Mascaret modeling platform to handle bank failure: failure occurs whether the actual slope of one given bed element is higher than the internal friction angle. The unstable bed elements are rotated around an appropriate axis, ensuring mass conservation. Mass failure of a bank due to slope instability is applied at the end of each sediment transport evolution iteration, once the bed evolution due to bed load (and/or suspended load) has been computed, but before the global sediment mass balance is verified. This bank failure algorithm is successfully tested using two laboratory experimental cases. Then, bank failure in a 1:40 scale physical model of the Rhine River composed of non-uniform material is simulated. The main features of the bank erosion and failure are correctly reproduced in the numerical simulations, namely the mass wasting at the bank toe, followed by failure at the bank head, and subsequent transport of the mobilised material in an aggradation front. Volumes of eroded material obtained are of the same order of magnitude as the volumes measured during the laboratory tests.

Active vibration control of functionally graded beams with piezoelectric layers based on higher order shear deformation theory

NASA Astrophysics Data System (ADS)

Bendine, K.; Boukhoulda, F. B.; Nouari, M.; Satla, Z.

2016-12-01

This paper reports on a study of active vibration control of functionally graded beams with upper and lower surface-bonded piezoelectric layers. The model is based on higher-order shear deformation theory and implemented using the finite element method (FEM). The proprieties of the functionally graded beam (FGB) are graded along the thickness direction. The piezoelectric actuator provides a damping effect on the FGB by means of a velocity feedback control algorithm. A Matlab program has been developed for the FGB model and compared with ANSYS APDL. Using Newmark's method numerical solutions are obtained for the dynamic equations of FGB with piezoelectric layers. Numerical results show the effects of the constituent volume fraction and the influence the feedback control gain on the frequency and dynamic response of FGBs.

Holographic conductivity of holographic superconductors with higher-order corrections

NASA Astrophysics Data System (ADS)

Sheykhi, Ahmad; Ghazanfari, Afsoon; Dehyadegari, Amin

2018-02-01

We analytically and numerically disclose the effects of the higher-order correction terms in the gravity and in the gauge field on the properties of s-wave holographic superconductors. On the gravity side, we consider the higher curvature Gauss-Bonnet corrections and on the gauge field side, we add a quadratic correction term to the Maxwell Lagrangian. We show that, for this system, one can still obtain an analytical relation between the critical temperature and the charge density. We also calculate the critical exponent and the condensation value both analytically and numerically. We use a variational method, based on the Sturm-Liouville eigenvalue problem for our analytical study, as well as a numerical shooting method in order to compare with our analytical results. For a fixed value of the Gauss-Bonnet parameter, we observe that the critical temperature decreases with increasing the nonlinearity of the gauge field. This implies that the nonlinear correction term to the Maxwell electrodynamics makes the condensation harder. We also study the holographic conductivity of the system and disclose the effects of the Gauss-Bonnet and nonlinear parameters α and b on the superconducting gap. We observe that, for various values of α and b, the real part of the conductivity is proportional to the frequency per temperature, ω /T, as the frequency is large enough. Besides, the conductivity has a minimum in the imaginary part which is shifted toward greater frequency with decreasing temperature.

Scalar conservation and boundedness in simulations of compressible flow

NASA Astrophysics Data System (ADS)

Subbareddy, Pramod K.; Kartha, Anand; Candler, Graham V.

2017-11-01

With the proper combination of high-order, low-dissipation numerical methods, physics-based subgrid-scale models, and boundary conditions it is becoming possible to simulate many combustion flows at relevant conditions. However, non-premixed flows are a particular challenge because the thickness of the fuel/oxidizer interface scales inversely with Reynolds number. Sharp interfaces can also be present in the initial or boundary conditions. When higher-order numerical methods are used, there are often aphysical undershoots and overshoots in the scalar variables (e.g. passive scalars, species mass fractions or progress variable). These numerical issues are especially prominent when low-dissipation methods are used, since sharp jumps in flow variables are not always coincident with regions of strong variation in the scalar fields: consequently, special detection mechanisms and dissipative fluxes are needed. Most numerical methods diffuse the interface, resulting in artificial mixing and spurious reactions. In this paper, we propose a numerical method that mitigates this issue. We present methods for passive and active scalars, and demonstrate their effectiveness with several examples.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Subbareddy, Pramod K.; Kartha, Anand; Candler, Graham V.

With the proper combination of high-order, low-dissipation numerical methods, physics-based subgrid-scale models, and boundary conditions it is becoming possible to simulate many combustion flows at relevant conditions. However, non-premixed flows are a particular challenge because the thickness of the fuel/oxidizer interface scales inversely with Reynolds number. Sharp interfaces can also be present in the initial or boundary conditions. When higher-order numerical methods are used, there are often aphysical undershoots and overshoots in the scalar variables (e.g.passive scalars, species mass fractions or progress variable). These numerical issues are especially prominent when low-dissipation methods are used, since sharp jumps in flow variablesmore » are not always coincident with regions of strong variation in the scalar fields: consequently, special detection mechanisms and dissipative fluxes are needed. Most numerical methods diffuse the interface, resulting in artificial mixing and spurious reactions. In this paper, we propose a numerical method that mitigates this issue. As a result, we present methods for passive and active scalars, and demonstrate their effectiveness with several examples.« less

Separating higher-order nonlinearities in transient absorption microscopy

NASA Astrophysics Data System (ADS)

Wilson, Jesse W.; Anderson, Miguel; Park, Jong Kang; Fischer, Martin C.; Warren, Warren S.

2015-08-01

The transient absorption response of melanin is a promising optically-accessible biomarker for distinguishing malignant melanoma from benign pigmented lesions, as demonstrated by earlier experiments on thin sections from biopsied tissue. The technique has also been demonstrated in vivo, but the higher optical intensity required for detecting these signals from backscattered light introduces higher-order nonlinearities in the transient response of melanin. These components that are higher than linear with respect to the pump or the probe introduce intensity-dependent changes to the overall response that complicate data analysis. However, our data also suggest these nonlinearities might be advantageous to in vivo imaging, in that different types of melanins have different nonlinear responses. Therefore, methods to separate linear from nonlinear components in transient absorption measurements might provide additional information to aid in the diagnosis of melanoma. We will discuss numerical methods for analyzing the various nonlinear contributions to pump-probe signals, with the ultimate objective of real time analysis using digital signal processing techniques. To that end, we have replaced the lock-in amplifier in our pump-probe microscope with a high-speed data acquisition board, and reprogrammed the coprocessor field-programmable gate array (FPGA) to perform lock-in detection. The FPGA lock-in offers better performance than the commercial instrument, in terms of both signal to noise ratio and speed. In addition, the flexibility of the digital signal processing approach enables demodulation of more complicated waveforms, such as spread-spectrum sequences, which has the potential to accelerate microscopy methods that rely on slow relaxation phenomena, such as photo-thermal and phosphorescence lifetime imaging.

A New Look to a Classic Issue: Reasoning and Academic Achievement at Secondary School

PubMed Central

Gómez-Veiga, Isabel; Vila Chaves, José O.; Duque, Gonzalo; García Madruga, Juan A.

2018-01-01

Higher-order thinking abilities such as abstract reasoning and meaningful school learning occur sequentially. The fulfillment of these tasks demands that people activate and use all of their working memory resources in a controlled and supervised way. The aims of this work were: (a) to study the interplay between two new reasoning measures, one mathematical (Cognitive Reflection Test) and the other verbal (Deductive Reasoning Test), and a third classical visuo-spatial reasoning measure (Raven Progressive Matrices Test); and (b) to investigate the relationship between these measures and academic achievement. Fifty-one 4th grade secondary school students participated in the experiment and completed the three reasoning tests. Academic achievement measures were the final numerical scores in seven basic subjects. The results demonstrated that cognitive reflection, visual, and verbal reasoning are intimately related and predicts academic achievement. This work confirms that abstract reasoning constitutes the most important higher-order cognitive ability that underlies academic achievement. It also reveals the importance of dual processes, verbal deduction and metacognition in ordinary teaching and learning at school. PMID:29643823

Sensitivity of an Antarctic Ice Sheet Model to Sub-Ice-Shelf Melting

NASA Astrophysics Data System (ADS)

Lipscomb, W. H.; Leguy, G.; Urban, N. M.; Berdahl, M.

2017-12-01

Theory and observations suggest that marine-based sectors of the Antarctic ice sheet could retreat rapidly under ocean warming and increased melting beneath ice shelves. Numerical models of marine ice sheets vary widely in sensitivity, depending on grid resolution and the parameterization of key processes (e.g., calving and hydrofracture). Here we study the sensitivity of the Antarctic ice sheet to ocean warming and sub-shelf melting in standalone simulations of the Community Ice Sheet Model (CISM). Melt rates either are prescribed based on observations and high-resolution ocean model output, or are derived from a plume model forced by idealized ocean temperature profiles. In CISM, we vary the model resolution (between 1 and 8 km), Stokes approximation (shallow-shelf, depth-integrated higher-order, or 3D higher-order) and calving scheme to create an ensemble of plausible responses to sub-shelf melting. This work supports a broader goal of building statistical and reduced models that can translate large-scale Earth-system model projections to changes in Antarctic ocean temperatures and ice sheet discharge, thus better quantifying uncertainty in Antarctic-sourced sea-level rise.

A New Look to a Classic Issue: Reasoning and Academic Achievement at Secondary School.

PubMed

Gómez-Veiga, Isabel; Vila Chaves, José O; Duque, Gonzalo; García Madruga, Juan A

2018-01-01

Higher-order thinking abilities such as abstract reasoning and meaningful school learning occur sequentially. The fulfillment of these tasks demands that people activate and use all of their working memory resources in a controlled and supervised way. The aims of this work were: (a) to study the interplay between two new reasoning measures, one mathematical (Cognitive Reflection Test) and the other verbal (Deductive Reasoning Test), and a third classical visuo-spatial reasoning measure (Raven Progressive Matrices Test); and (b) to investigate the relationship between these measures and academic achievement. Fifty-one 4th grade secondary school students participated in the experiment and completed the three reasoning tests. Academic achievement measures were the final numerical scores in seven basic subjects. The results demonstrated that cognitive reflection, visual, and verbal reasoning are intimately related and predicts academic achievement. This work confirms that abstract reasoning constitutes the most important higher-order cognitive ability that underlies academic achievement. It also reveals the importance of dual processes, verbal deduction and metacognition in ordinary teaching and learning at school.

Numerical analysis on a passive chaotic micromixer with helical microchannel.

PubMed

Wang, Ruijin; Lin, Jianzhong

2006-01-01

In order to improve the mixing efficiency, the diffusion and mixing of species in the helical micro-mixer are simulated numerically. The results show that the mixing efficiency in the helical micromixer is much higher than that in the straight micro-channel and obviously higher than that in the serpentine micro-channel when Reynolds number is low. At high Reynolds number, even though the mixing efficiency in the helical micro-mixer is still much higher than that in the straight micro-channel, no obvious difference of mixing efficiency in the helical micro-mixer and serpentine micro-channel is found. The conclusions are helpful to optimize the structure of the micro-mixer.

Multi-instantons and exact results III: Unification of even and odd anharmonic oscillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jentschura, Ulrich D.; Surzhykov, Andrey; GSI Helmholtzzentrum fuer Schwerionenforschung, 64291 Darmstadt

2010-05-15

This is the third article in a series of three papers on the resonance energy levels of anharmonic oscillators. Whereas the first two papers mainly dealt with double-well potentials and modifications thereof [see J. Zinn-Justin, U.D. Jentschura, Ann. Phys. (N.Y.) 313 (2004) 197 and 269], we here focus on simple even and odd anharmonic oscillators for arbitrary magnitude and complex phase of the coupling parameter. A unification is achieved by the use of PT-symmetry inspired dispersion relations and generalized quantization conditions that include instanton configurations. Higher-order formulas are provided for the oscillators of degrees 3 to 8, which lead tomore » subleading corrections to the leading factorial growth of the perturbative coefficients describing the resonance energies. Numerical results are provided, and higher-order terms are found to be numerically significant. The resonances are described by generalized expansions involving intertwined nonanalytic exponentials, logarithmic terms and power series. Finally, we summarize spectral properties and dispersion relations of anharmonic oscillators, and their interconnections. The purpose is to look at one of the classic problems of quantum theory from a new perspective, through which we gain systematic access to the phenomenologically significant higher-order terms.« less

Graph cuts for curvature based image denoising.

PubMed

Bae, Egil; Shi, Juan; Tai, Xue-Cheng

2011-05-01

Minimization of total variation (TV) is a well-known method for image denoising. Recently, the relationship between TV minimization problems and binary MRF models has been much explored. This has resulted in some very efficient combinatorial optimization algorithms for the TV minimization problem in the discrete setting via graph cuts. To overcome limitations, such as staircasing effects, of the relatively simple TV model, variational models based upon higher order derivatives have been proposed. The Euler's elastica model is one such higher order model of central importance, which minimizes the curvature of all level lines in the image. Traditional numerical methods for minimizing the energy in such higher order models are complicated and computationally complex. In this paper, we will present an efficient minimization algorithm based upon graph cuts for minimizing the energy in the Euler's elastica model, by simplifying the problem to that of solving a sequence of easy graph representable problems. This sequence has connections to the gradient flow of the energy function, and converges to a minimum point. The numerical experiments show that our new approach is more effective in maintaining smooth visual results while preserving sharp features better than TV models.

Effects of high-order correlations on personalized recommendations for bipartite networks

NASA Astrophysics Data System (ADS)

Liu, Jian-Guo; Zhou, Tao; Che, Hong-An; Wang, Bing-Hong; Zhang, Yi-Cheng

2010-02-01

In this paper, we introduce a modified collaborative filtering (MCF) algorithm, which has remarkably higher accuracy than the standard collaborative filtering. In the MCF, instead of the cosine similarity index, the user-user correlations are obtained by a diffusion process. Furthermore, by considering the second-order correlations, we design an effective algorithm that depresses the influence of mainstream preferences. Simulation results show that the algorithmic accuracy, measured by the average ranking score, is further improved by 20.45% and 33.25% in the optimal cases of MovieLens and Netflix data. More importantly, the optimal value λ depends approximately monotonously on the sparsity of the training set. Given a real system, we could estimate the optimal parameter according to the data sparsity, which makes this algorithm easy to be applied. In addition, two significant criteria of algorithmic performance, diversity and popularity, are also taken into account. Numerical results show that as the sparsity increases, the algorithm considering the second-order correlation can outperform the MCF simultaneously in all three criteria.

Solution of the hydrodynamic device model using high-order non-oscillatory shock capturing algorithms. [for junction diodes simulation

NASA Technical Reports Server (NTRS)

Fatemi, Emad; Osher, Stanley; Jerome, Joseph

1991-01-01

A micron n+ - n - n+ silicon diode is simulated via the hydrodynamic model for carrier transport. The numerical algorithms employed are for the non-steady case, and a limiting process is used to reach steady state. The simulation employs shock capturing algorithms, and indeed shocks, or very rapid transition regimes, are observed in the transient case for the coupled system, consisting of the potential equation and the conservation equations describing charge, momentum, and energy transfer for the electron carriers. These algorithms, termed essentially nonoscillatory, were successfully applied in other contexts to model the flow in gas dynamics, magnetohydrodynamics, and other physical situations involving the conservation laws in fluid mechanics. The method here is first order in time, but the use of small time steps allows for good accuracy. Runge-Kutta methods allow one to achieve higher accuracy in time if desired. The spatial accuracy is of high order in regions of smoothness.

Parametric Study of Decay of Homogeneous Isotropic Turbulence Using Large Eddy Simulation

NASA Technical Reports Server (NTRS)

Swanson, R. C.; Rumsey, Christopher L.; Rubinstein, Robert; Balakumar, Ponnampalam; Zang, Thomas A.

2012-01-01

Numerical simulations of decaying homogeneous isotropic turbulence are performed with both low-order and high-order spatial discretization schemes. The turbulent Mach and Reynolds numbers for the simulations are 0.2 and 250, respectively. For the low-order schemes we use either second-order central or third-order upwind biased differencing. For higher order approximations we apply weighted essentially non-oscillatory (WENO) schemes, both with linear and nonlinear weights. There are two objectives in this preliminary effort to investigate possible schemes for large eddy simulation (LES). One is to explore the capability of a widely used low-order computational fluid dynamics (CFD) code to perform LES computations. The other is to determine the effect of higher order accuracy (fifth, seventh, and ninth order) achieved with high-order upwind biased WENO-based schemes. Turbulence statistics, such as kinetic energy, dissipation, and skewness, along with the energy spectra from simulations of the decaying turbulence problem are used to assess and compare the various numerical schemes. In addition, results from the best performing schemes are compared with those from a spectral scheme. The effects of grid density, ranging from 32 cubed to 192 cubed, on the computations are also examined. The fifth-order WENO-based scheme is found to be too dissipative, especially on the coarser grids. However, with the seventh-order and ninth-order WENO-based schemes we observe a significant improvement in accuracy relative to the lower order LES schemes, as revealed by the computed peak in the energy dissipation and by the energy spectrum.

Progress in the Development of a Class of Efficient Low Dissipative High Order Shock-capturing Methods

NASA Technical Reports Server (NTRS)

Yee, H. C.; Sjogreen, B.; Sandham, N. D.; Hadjadj, A.; Kwak, Dochan (Technical Monitor)

2000-01-01

In a series of papers, Olsson (1994, 1995), Olsson & Oliger (1994), Strand (1994), Gerritsen Olsson (1996), Yee et al. (1999a,b, 2000) and Sandham & Yee (2000), the issue of nonlinear stability of the compressible Euler and Navier-Stokes Equations, including physical boundaries, and the corresponding development of the discrete analogue of nonlinear stable high order schemes, including boundary schemes, were developed, extended and evaluated for various fluid flows. High order here refers to spatial schemes that are essentially fourth-order or higher away from shock and shear regions. The objective of this paper is to give an overview of the progress of the low dissipative high order shock-capturing schemes proposed by Yee et al. (1999a,b, 2000). This class of schemes consists of simple non-dissipative high order compact or non-compact central spatial differencings and adaptive nonlinear numerical dissipation operators to minimize the use of numerical dissipation. The amount of numerical dissipation is further minimized by applying the scheme to the entropy splitting form of the inviscid flux derivatives, and by rewriting the viscous terms to minimize odd-even decoupling before the application of the central scheme (Sandham & Yee). The efficiency and accuracy of these scheme are compared with spectral, TVD and fifth- order WENO schemes. A new approach of Sjogreen & Yee (2000) utilizing non-orthogonal multi-resolution wavelet basis functions as sensors to dynamically determine the appropriate amount of numerical dissipation to be added to the non-dissipative high order spatial scheme at each grid point will be discussed. Numerical experiments of long time integration of smooth flows, shock-turbulence interactions, direct numerical simulations of a 3-D compressible turbulent plane channel flow, and various mixing layer problems indicate that these schemes are especially suitable for practical complex problems in nonlinear aeroacoustics, rotorcraft dynamics, direct numerical simulation or large eddy simulation of compressible turbulent flows at various speeds including high-speed shock-turbulence interactions, and general long time wave propagation problems. These schemes, including entropy splitting, have also been extended to freestream preserving schemes on curvilinear moving grids for a thermally perfect gas (Vinokur & Yee 2000).

Residents' numeric inputting error in computerized physician order entry prescription.

PubMed

Wu, Xue; Wu, Changxu; Zhang, Kan; Wei, Dong

2016-04-01

Computerized physician order entry (CPOE) system with embedded clinical decision support (CDS) can significantly reduce certain types of prescription error. However, prescription errors still occur. Various factors such as the numeric inputting methods in human computer interaction (HCI) produce different error rates and types, but has received relatively little attention. This study aimed to examine the effects of numeric inputting methods and urgency levels on numeric inputting errors of prescription, as well as categorize the types of errors. Thirty residents participated in four prescribing tasks in which two factors were manipulated: numeric inputting methods (numeric row in the main keyboard vs. numeric keypad) and urgency levels (urgent situation vs. non-urgent situation). Multiple aspects of participants' prescribing behavior were measured in sober prescribing situations. The results revealed that in urgent situations, participants were prone to make mistakes when using the numeric row in the main keyboard. With control of performance in the sober prescribing situation, the effects of the input methods disappeared, and urgency was found to play a significant role in the generalized linear model. Most errors were either omission or substitution types, but the proportion of transposition and intrusion error types were significantly higher than that of the previous research. Among numbers 3, 8, and 9, which were the less common digits used in prescription, the error rate was higher, which was a great risk to patient safety. Urgency played a more important role in CPOE numeric typing error-making than typing skills and typing habits. It was recommended that inputting with the numeric keypad had lower error rates in urgent situation. An alternative design could consider increasing the sensitivity of the keys with lower frequency of occurrence and decimals. To improve the usability of CPOE, numeric keyboard design and error detection could benefit from spatial incidence of errors found in this study. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Numerical simulation of unmanned aerial vehicle under centrifugal load and optimization of milling and planing

NASA Astrophysics Data System (ADS)

Chen, Yunsheng; Lu, Xinghua

2018-05-01

The mechanical parts of the fuselage surface of the UAV are easily fractured by the action of the centrifugal load. In order to improve the compressive strength of UAV and guide the milling and planing of mechanical parts, a numerical simulation method of UAV fuselage compression under centrifugal load based on discrete element analysis method is proposed. The three-dimensional discrete element method is used to establish the splitting tensile force analysis model of the UAV fuselage under centrifugal loading. The micro-contact connection parameters of the UAV fuselage are calculated, and the yield tensile model of the mechanical components is established. The dynamic and static mechanical model of the aircraft fuselage milling is analyzed by the axial amplitude vibration frequency combined method. The correlation parameters of the cutting depth on the tool wear are obtained. The centrifugal load stress spectrum of the surface of the UAV is calculated. The meshing and finite element simulation of the rotor blade of the unmanned aerial vehicle is carried out to optimize the milling process. The test results show that the accuracy of the anti - compression numerical test of the UAV is higher by adopting the method, and the anti - fatigue damage capability of the unmanned aerial vehicle body is improved through the milling and processing optimization, and the mechanical strength of the unmanned aerial vehicle can be effectively improved.

Electron acceleration by a tightly focused Hermite-Gaussian beam: higher-order corrections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao Zhiguo; Institute of Laser Physics and Chemistry, Sichuan University, Chengdu 610064; Yang Dangxiao

2008-03-15

Taking the TEM{sub 1,0}-mode Hermite-Gaussian (H-G) beam as a numerical calculation example, and based on the method of the perturbation series expansion, the higher-order field corrections of H-G beams are derived and used to study the electron acceleration by a tightly focused H-G beam in vacuum. For the case of the off-axis injection the field corrections to the terms of order f{sup 3} (f=1/kw{sub 0}, k and w{sub 0} being the wavenumber and waist width, respectively) are considered, and for the case of the on-axis injection the contributions of the terms of higher orders are negligible. By a suitable optimizationmore » of injection parameters the energy gain in the giga-electron-volt regime can be achieved.« less

Path integrals with higher order actions: Application to realistic chemical systems

NASA Astrophysics Data System (ADS)

Lindoy, Lachlan P.; Huang, Gavin S.; Jordan, Meredith J. T.

2018-02-01

Quantum thermodynamic parameters can be determined using path integral Monte Carlo (PIMC) simulations. These simulations, however, become computationally demanding as the quantum nature of the system increases, although their efficiency can be improved by using higher order approximations to the thermal density matrix, specifically the action. Here we compare the standard, primitive approximation to the action (PA) and three higher order approximations, the Takahashi-Imada action (TIA), the Suzuki-Chin action (SCA) and the Chin action (CA). The resulting PIMC methods are applied to two realistic potential energy surfaces, for H2O and HCN-HNC, both of which are spectroscopically accurate and contain three-body interactions. We further numerically optimise, for each potential, the SCA parameter and the two free parameters in the CA, obtaining more significant improvements in efficiency than seen previously in the literature. For both H2O and HCN-HNC, accounting for all required potential and force evaluations, the optimised CA formalism is approximately twice as efficient as the TIA formalism and approximately an order of magnitude more efficient than the PA. The optimised SCA formalism shows similar efficiency gains to the CA for HCN-HNC but has similar efficiency to the TIA for H2O at low temperature. In H2O and HCN-HNC systems, the optimal value of the a1 CA parameter is approximately 1/3 , corresponding to an equal weighting of all force terms in the thermal density matrix, and similar to previous studies, the optimal α parameter in the SCA was ˜0.31. Importantly, poor choice of parameter significantly degrades the performance of the SCA and CA methods. In particular, for the CA, setting a1 = 0 is not efficient: the reduction in convergence efficiency is not offset by the lower number of force evaluations. We also find that the harmonic approximation to the CA parameters, whilst providing a fourth order approximation to the action, is not optimal for these realistic potentials: numerical optimisation leads to better approximate cancellation of the fifth order terms, with deviation between the harmonic and numerically optimised parameters more marked in the more quantum H2O system. This suggests that numerically optimising the CA or SCA parameters, which can be done at high temperature, will be important in fully realising the efficiency gains of these formalisms for realistic potentials.

Detailed and reduced chemical-kinetic descriptions for hydrocarbon combustion

NASA Astrophysics Data System (ADS)

Petrova, Maria V.

Numerical and theoretical studies of autoignition processes of fuels such as propane are in need of realistic simplified chemical-kinetic descriptions that retain the essential features of the detailed descriptions. These descriptions should be computationally feasible and cost-effective. Such descriptions are useful for investigating ignition processes that occur, for example, in homogeneous-charge compression-ignition engines, for studying the structures and dynamics of detonations and in fields such as multi-dimensional Computational Fluid Dynamics (CFD). Reduced chemistry has previously been developed successfully for a number of other hydrocarbon fuels, however, propane has not been considered in this manner. This work focuses on the fuels of propane, as well propene, allene and propyne, for several reasons. The ignition properties of propane resemble those of other higher hydrocarbons but are different from those of the lower hydrocarbons (e.g. ethylene and acetylene). Propane, therefore, may be the smallest hydrocarbon that is representative of higher hydrocarbons in ignition and detonation processes. Since the overall activation energy and ignition times for propane are similar to those of other higher hydrocarbons, including liquid fuels that are suitable for many applications, propane has been used as a model fuel for several numerical and experimental studies. The reason for studying elementary chemistry of propene and C3H4 (allene or propyne) is that during the combustion process, propane breaks down to propene and C3H4 before proceeding to products. Similarly, propene combustion includes C3H4 chemistry. In studying propane combustion, it is therefore necessary to understand the underlying combustion chemistry of propene as well as C3H 4. The first part of this thesis focuses on obtaining and testing a detailed chemical-kinetic description for autoignition of propane, propene and C 3H4, by comparing predictions obtained with this detailed mechanism against numerous experimental data available from shock-tube studies and flame-speed measurements. To keep the detailed mechanism small, attention is restricted to pressures below about 100 atm, temperatures above about 1000 K and equivalence ratios less than about 3. Based on this detailed chemistry description, short (or skeletal) mechanisms are then obtained for each of the three fuels by eliminating reactions that are unimportant for the autoignition process under conditions presented above. This was achieved by utilizing tools such as sensitivity and reaction pathway analyses. Two distinct methodologies were then used in order to obtain a reduced mechanism for autoignition from the short mechanisms. A Systematic Reduction approach is first taken that involves introducing steady-state approximations to as many species as analytically possible. To avoid resorting to numerical methods, the analysis for obtaining ignition times for heptane, presented by Peters and co-workers is followed in order to obtain a rough estimate for an expression of propane ignition time. The results from this expression are then compared to the ignition times obtained computationally with the detailed mechanism. The second method is an Empirical Approach in which chemistry is not derived formally, but rather postulated empirically on the basis of experimental, computational and theoretical observations. As a result, generalized reduced mechanisms are proposed for autoignition of propane, propene and C3H 4. Expressions for ignition times obtained via this empirical approach are compared to the computational results obtained from the detailed mechanism.

Power-law scaling of extreme dynamics near higher-order exceptional points

NASA Astrophysics Data System (ADS)

Zhong, Q.; Christodoulides, D. N.; Khajavikhan, M.; Makris, K. G.; El-Ganainy, R.

2018-02-01

We investigate the extreme dynamics of non-Hermitian systems near higher-order exceptional points in photonic networks constructed using the bosonic algebra method. We show that strong power oscillations for certain initial conditions can occur as a result of the peculiar eigenspace geometry and its dimensionality collapse near these singularities. By using complementary numerical and analytical approaches, we show that, in the parity-time (PT ) phase near exceptional points, the logarithm of the maximum optical power amplification scales linearly with the order of the exceptional point. We focus in our discussion on photonic systems, but we note that our results apply to other physical systems as well.

A new scheme for the parameterization of the turbulent planetary boundary layer in the GLAS fourth order GCM

NASA Technical Reports Server (NTRS)

Helfand, H. M.

1985-01-01

Methods being used to increase the horizontal and vertical resolution and to implement more sophisticated parameterization schemes for general circulation models (GCM) run on newer, more powerful computers are described. Attention is focused on the NASA-Goddard Laboratory for Atmospherics fourth order GCM. A new planetary boundary layer (PBL) model has been developed which features explicit resolution of two or more layers. Numerical models are presented for parameterizing the turbulent vertical heat, momentum and moisture fluxes at the earth's surface and between the layers in the PBL model. An extended Monin-Obhukov similarity scheme is applied to express the relationships between the lowest levels of the GCM and the surface fluxes. On-line weather prediction experiments are to be run to test the effects of the higher resolution thereby obtained for dynamic atmospheric processes.

Long-Range Correlation in alpha-Wave Predominant EEG in Human

NASA Astrophysics Data System (ADS)

Sharif, Asif; Chyan Lin, Der; Kwan, Hon; Borette, D. S.

2004-03-01

The background noise in the alpha-predominant EEG taken from eyes-open and eyes-closed neurophysiological states is studied. Scale-free characteristic is found in both cases using the wavelet approach developed by Simonsen and Nes [1]. The numerical results further show the scaling exponent during eyes-closed is consistently lower than eyes-open. We conjecture the origin of this difference is related to the temporal reconfiguration of the neural network in the brain. To further investigate the scaling structure of the EEG background noise, we extended the second order statistics to higher order moments using the EEG increment process. We found that the background fluctuation in the alpha-predominant EEG is predominantly monofractal. Preliminary results are given to support this finding and its implication in brain functioning is discussed. [1] A.H. Simonsen and O.M. Nes, Physical Review E, 58, 2779¡V2748 (1998).

Simulation of Planetary Formation using Python

NASA Astrophysics Data System (ADS)

Bufkin, James; Bixler, David

2015-03-01

A program to simulate planetary formation was developed in the Python programming language. The program consists of randomly placed and massed bodies surrounding a central massive object in order to approximate a protoplanetary disk. The orbits of these bodies are time-stepped, with accelerations, velocities and new positions calculated in each step. Bodies are allowed to merge if their disks intersect. Numerous parameters (orbital distance, masses, number of particles, etc.) were varied in order to optimize the program. The program uses an iterative difference equation approach to solve the equations of motion using a kinematic model. Conservation of energy and angular momentum are not specifically forced, but conservation of momentum is forced during the merging of bodies. The initial program was created in Visual Python (VPython) but the current intention is to allow for higher particle count and faster processing by utilizing PyOpenCl and PyOpenGl. Current results and progress will be reported.

Final Report for Contract N00014-89-J-1967 for the Time Period from 1 May 1989 to 31 December 1990 (Texas Univ. at Austin. Applied Research Labs.)

DTIC Science & Technology

1991-04-23

in this section. In our investigation of higher order processing methods for remote acoustic sensing we sought to understand the principles of laser...magnitude less than those presently detected in laboratory measurements. An initial study of several potential higher order processing techniques was...incoherent. The use of higher order processing methods to provide some level of discrimination against noise thus appears tractable. Finally, the effects

Application of a symmetric total variation diminishing scheme to aerodynamics of rotors

NASA Astrophysics Data System (ADS)

Usta, Ebru

2002-09-01

The aerodynamics characteristics of rotors in hover have been studied on stretched non-orthogonal grids using spatially high order symmetric total variation diminishing (STVD) schemes. Several companion numerical viscosity terms have been tested. The effects of higher order metrics, higher order load integrations and turbulence effects on the rotor performance have been studied. Where possible, calculations for 1-D and 2-D benchmark problems have been done on uniform grids, and comparisons with exact solutions have been made to understand the dispersion and dissipation characteristics of these algorithms. A baseline finite volume methodology termed TURNS (Transonic Unsteady Rotor Navier-Stokes) is the starting point for this effort. The original TURNS solver solves the 3-D compressible Navier-Stokes equations in an integral form using a third order upwind scheme. It is first or second order accurate in time. In the modified solver, the inviscid flux at a cell face is decomposed into two parts. The first part of the flux is symmetric in space, while the second part consists of an upwind-biased numerical viscosity term. The symmetric part of the flux at the cell face is computed to fourth-, sixth- or eighth order accuracy in space. The numerical viscosity portion of the flux is computed using either a third order accurate MUSCL scheme or a fifth order WENO scheme. A number of results are presented for the two-bladed Caradonna-Tung rotor and for a four-bladed UH-60A rotor in hover. Comparisons with the original TURNS code, and experiments are given. Results are also presented on the effects of metrics calculations, load integration algorithms, and turbulence models on the solution accuracy. A total of 64 combinations were studied in this thesis work. For brevity, only a small subset of results highlighting the most important conclusions are presented. It should be noted that use of higher order formulations did not affect the temporal stability of the algorithm and did not require any reduction in the time step. The calculations show that the solution accuracy increases when the 3 rd order upwind scheme in the baseline algorithm is replaced with 4th and 6th order accurate symmetric flux calculations. A point of diminishing returns is reached as increasingly larger stencils are used on highly stretched grids. The numerical viscosity term, when computed with the third order MUSCL scheme, is very dissipative, and does not resolve the tip vortex well. The WENO5 scheme, on the other hand significantly improves the tip vortex capturing. The STVD6+WENO5 scheme, in particular gave the best combinations of solution accuracy and efficiency on stretched grids. Spatially fourth order accurate metric calculations were found to be beneficial, but should be used in conjunction with a limiter that drops the metric calculation to a second order accuracy in the vicinity of grid discontinuities. High order integration of loads was found to have a beneficial, but small effect on the computed loads. Replacing the Baldwin-Lomax turbulence model with a one equation Spalart-Allmaras model resulted in higher than expected profile power contributions. Nevertheless the one-equation model is recommended for its robustness, its ability to model separated flows at high thrust settings, and the natural manner in which turbulence in the rotor wake may be treated.

A flowgraph model for bladder carcinoma

PubMed Central

2014-01-01

Background Superficial bladder cancer has been the subject of numerous studies for many years, but the evolution of the disease still remains not well understood. After the tumor has been surgically removed, it may reappear at a similar level of malignancy or progress to a higher level. The process may be reasonably modeled by means of a Markov process. However, in order to more completely model the evolution of the disease, this approach is insufficient. The semi-Markov framework allows a more realistic approach, but calculations become frequently intractable. In this context, flowgraph models provide an efficient approach to successfully manage the evolution of superficial bladder carcinoma. Our aim is to test this methodology in this particular case. Results We have built a successful model for a simple but representative case. Conclusion The flowgraph approach is suitable for modeling of superficial bladder cancer. PMID:25080066

Super-rogue waves in simulations based on weakly nonlinear and fully nonlinear hydrodynamic equations.

PubMed

Slunyaev, A; Pelinovsky, E; Sergeeva, A; Chabchoub, A; Hoffmann, N; Onorato, M; Akhmediev, N

2013-07-01

The rogue wave solutions (rational multibreathers) of the nonlinear Schrödinger equation (NLS) are tested in numerical simulations of weakly nonlinear and fully nonlinear hydrodynamic equations. Only the lowest order solutions from 1 to 5 are considered. A higher accuracy of wave propagation in space is reached using the modified NLS equation, also known as the Dysthe equation. This numerical modeling allowed us to directly compare simulations with recent results of laboratory measurements in Chabchoub et al. [Phys. Rev. E 86, 056601 (2012)]. In order to achieve even higher physical accuracy, we employed fully nonlinear simulations of potential Euler equations. These simulations provided us with basic characteristics of long time evolution of rational solutions of the NLS equation in the case of near-breaking conditions. The analytic NLS solutions are found to describe the actual wave dynamics of steep waves reasonably well.

Takahasi Nearest-Neighbour Gas Revisited II: Morse Gases

NASA Astrophysics Data System (ADS)

Matsumoto, Akira

2011-12-01

Some thermodynamic quantities for the Morse potential are analytically evaluated at an isobaric process. The parameters of Morse gases for 21 substances are obtained by the second virial coefficient data and the spectroscopic data of diatomic molecules. Also some thermodynamic quantities for water are calculated numerically and drawn graphically. The inflexion point of the length L which depends on temperature T and pressure P corresponds physically to a boiling point. L indicates the liquid phase from lower temperature to the inflexion point and the gaseous phase from the inflexion point to higher temperature. The boiling temperatures indicate reasonable values compared with experimental data. The behaviour of L suggests a chance of a first-order phase transition in one dimension.

Conversion of Component-Based Point Definition to VSP Model and Higher Order Meshing

NASA Technical Reports Server (NTRS)

Ordaz, Irian

2011-01-01

Vehicle Sketch Pad (VSP) has become a powerful conceptual and parametric geometry tool with numerous export capabilities for third-party analysis codes as well as robust surface meshing capabilities for computational fluid dynamics (CFD) analysis. However, a capability gap currently exists for reconstructing a fully parametric VSP model of a geometry generated by third-party software. A computer code called GEO2VSP has been developed to close this gap and to allow the integration of VSP into a closed-loop geometry design process with other third-party design tools. Furthermore, the automated CFD surface meshing capability of VSP are demonstrated for component-based point definition geometries in a conceptual analysis and design framework.

The formation and fragmentation of disks around primordial protostars.

PubMed

Clark, Paul C; Glover, Simon C O; Smith, Rowan J; Greif, Thomas H; Klessen, Ralf S; Bromm, Volker

2011-02-25

The very first stars to form in the universe heralded an end to the cosmic dark ages and introduced new physical processes that shaped early cosmic evolution. Until now, it was thought that these stars lived short, solitary lives, with only one extremely massive star, or possibly a very wide binary system, forming in each dark-matter minihalo. Here we describe numerical simulations that show that these stars were, to the contrary, often members of tight multiple systems. Our results show that the disks that formed around the first young stars were unstable to gravitational fragmentation, possibly producing small binary and higher-order systems that had separations as small as the distance between Earth and the Sun.

Nagy-Soper Subtraction: a Review

NASA Astrophysics Data System (ADS)

Robens, Tania

2013-07-01

In this review, we present a review on an alternative NLO subtraction scheme, based on the splitting kernels of an improved parton shower that promises to facilitate the inclusion of higher-order corrections into Monte Carlo event generators. We give expressions for the scheme for massless emitters, and point to work on the extension for massive cases. As an example, we show results for the C parameter of the process e+e-→3 jets at NLO which have recently been published as a verification of this scheme. We equally provide analytic expressions for integrated counterterms that have not been presented in previous work, and comment on the possibility of analytic approximations for the remaining numerical integrals.

Numerically stable, scalable formulas for parallel and online computation of higher-order multivariate central moments with arbitrary weights

DOE PAGES

Pebay, Philippe; Terriberry, Timothy B.; Kolla, Hemanth; ...

2016-03-29

Formulas for incremental or parallel computation of second order central moments have long been known, and recent extensions of these formulas to univariate and multivariate moments of arbitrary order have been developed. Such formulas are of key importance in scenarios where incremental results are required and in parallel and distributed systems where communication costs are high. We survey these recent results, and improve them with arbitrary-order, numerically stable one-pass formulas which we further extend with weighted and compound variants. We also develop a generalized correction factor for standard two-pass algorithms that enables the maintenance of accuracy over nearly the fullmore » representable range of the input, avoiding the need for extended-precision arithmetic. We then empirically examine algorithm correctness for pairwise update formulas up to order four as well as condition number and relative error bounds for eight different central moment formulas, each up to degree six, to address the trade-offs between numerical accuracy and speed of the various algorithms. Finally, we demonstrate the use of the most elaborate among the above mentioned formulas, with the utilization of the compound moments for a practical large-scale scientific application.« less

Higher-order triangular spectral element method with optimized cubature points for seismic wavefield modeling

NASA Astrophysics Data System (ADS)

Liu, Youshan; Teng, Jiwen; Xu, Tao; Badal, José

2017-05-01

The mass-lumped method avoids the cost of inverting the mass matrix and simultaneously maintains spatial accuracy by adopting additional interior integration points, known as cubature points. To date, such points are only known analytically in tensor domains, such as quadrilateral or hexahedral elements. Thus, the diagonal-mass-matrix spectral element method (SEM) in non-tensor domains always relies on numerically computed interpolation points or quadrature points. However, only the cubature points for degrees 1 to 6 are known, which is the reason that we have developed a p-norm-based optimization algorithm to obtain higher-order cubature points. In this way, we obtain and tabulate new cubature points with all positive integration weights for degrees 7 to 9. The dispersion analysis illustrates that the dispersion relation determined from the new optimized cubature points is comparable to that of the mass and stiffness matrices obtained by exact integration. Simultaneously, the Lebesgue constant for the new optimized cubature points indicates its surprisingly good interpolation properties. As a result, such points provide both good interpolation properties and integration accuracy. The Courant-Friedrichs-Lewy (CFL) numbers are tabulated for the conventional Fekete-based triangular spectral element (TSEM), the TSEM with exact integration, and the optimized cubature-based TSEM (OTSEM). A complementary study demonstrates the spectral convergence of the OTSEM. A numerical example conducted on a half-space model demonstrates that the OTSEM improves the accuracy by approximately one order of magnitude compared to the conventional Fekete-based TSEM. In particular, the accuracy of the 7th-order OTSEM is even higher than that of the 14th-order Fekete-based TSEM. Furthermore, the OTSEM produces a result that can compete in accuracy with the quadrilateral SEM (QSEM). The high accuracy of the OTSEM is also tested with a non-flat topography model. In terms of computational efficiency, the OTSEM is more efficient than the Fekete-based TSEM, although it is slightly costlier than the QSEM when a comparable numerical accuracy is required.

Adaptive Numerical Dissipative Control in High Order Schemes for Multi-D Non-Ideal MHD

NASA Technical Reports Server (NTRS)

Yee, H. C.; Sjoegreen, B.

2004-01-01

The goal is to extend our adaptive numerical dissipation control in high order filter schemes and our new divergence-free methods for ideal MHD to non-ideal MHD that include viscosity and resistivity. The key idea consists of automatic detection of different flow features as distinct sensors to signal the appropriate type and amount of numerical dissipation/filter where needed and leave the rest of the region free of numerical dissipation contamination. These scheme-independent detectors are capable of distinguishing shocks/shears, flame sheets, turbulent fluctuations and spurious high-frequency oscillations. The detection algorithm is based on an artificial compression method (ACM) (for shocks/shears), and redundant multi-resolution wavelets (WAV) (for the above types of flow feature). These filter approaches also provide a natural and efficient way for the minimization of Div(B) numerical error. The filter scheme consists of spatially sixth order or higher non-dissipative spatial difference operators as the base scheme for the inviscid flux derivatives. If necessary, a small amount of high order linear dissipation is used to remove spurious high frequency oscillations. For example, an eighth-order centered linear dissipation (AD8) might be included in conjunction with a spatially sixth-order base scheme. The inviscid difference operator is applied twice for the viscous flux derivatives. After the completion of a full time step of the base scheme step, the solution is adaptively filtered by the product of a 'flow detector' and the 'nonlinear dissipative portion' of a high-resolution shock-capturing scheme. In addition, the scheme independent wavelet flow detector can be used in conjunction with spatially compact, spectral or spectral element type of base schemes. The ACM and wavelet filter schemes using the dissipative portion of a second-order shock-capturing scheme with sixth-order spatial central base scheme for both the inviscid and viscous MHD flux derivatives and a fourth-order Runge-Kutta method are denoted.

Slat Noise Predictions Using Higher-Order Finite-Difference Methods on Overset Grids

NASA Technical Reports Server (NTRS)

Housman, Jeffrey A.; Kiris, Cetin

2016-01-01

Computational aeroacoustic simulations using the structured overset grid approach and higher-order finite difference methods within the Launch Ascent and Vehicle Aerodynamics (LAVA) solver framework are presented for slat noise predictions. The simulations are part of a collaborative study comparing noise generation mechanisms between a conventional slat and a Krueger leading edge flap. Simulation results are compared with experimental data acquired during an aeroacoustic test in the NASA Langley Quiet Flow Facility. Details of the structured overset grid, numerical discretization, and turbulence model are provided.

Effects of Scale, Question Location, Order of Response Alternatives, and Season on Self-Reported Noise Annoyance Using ICBEN Scales: A Field Experiment.

PubMed

Brink, Mark; Schreckenberg, Dirk; Vienneau, Danielle; Cajochen, Christian; Wunderli, Jean-Marc; Probst-Hensch, Nicole; Röösli, Martin

2016-11-23

The type of noise annoyance scale and aspects of its presentation such as response format or location within a questionnaire and other contextual factors may affect self-reported noise annoyance. By means of a balanced experimental design, the effect of type of annoyance question and corresponding scale (5-point verbal vs. 11-point numerical ICBEN (International Commission on Biological Effects of Noise) scale), presentation order of scale points (ascending vs. descending), question location (early vs. late within the questionnaire), and survey season (autumn vs. spring) on reported road traffic noise annoyance was investigated in a postal survey with a stratified random sample of 2386 Swiss residents. Our results showed that early appearance of annoyance questions was significantly associated with higher annoyance scores. Questionnaires filled out in autumn were associated with a significantly higher annoyance rating than in the springtime. No effect was found for the order of response alternatives. Standardized average annoyance scores were slightly higher using the 11-point numerical scale whereas the percentage of highly annoyed respondents was higher based on the 5-point scale, using common cutoff points. In conclusion, placement and presentation of annoyance questions within a questionnaire, as well as the time of the year a survey is carried out, have small but demonstrable effects on the degree of self-reported noise annoyance.

Effects of Scale, Question Location, Order of Response Alternatives, and Season on Self-Reported Noise Annoyance Using ICBEN Scales: A Field Experiment

PubMed Central

Brink, Mark; Schreckenberg, Dirk; Vienneau, Danielle; Cajochen, Christian; Wunderli, Jean-Marc; Probst-Hensch, Nicole; Röösli, Martin

2016-01-01

The type of noise annoyance scale and aspects of its presentation such as response format or location within a questionnaire and other contextual factors may affect self-reported noise annoyance. By means of a balanced experimental design, the effect of type of annoyance question and corresponding scale (5-point verbal vs. 11-point numerical ICBEN (International Commission on Biological Effects of Noise) scale), presentation order of scale points (ascending vs. descending), question location (early vs. late within the questionnaire), and survey season (autumn vs. spring) on reported road traffic noise annoyance was investigated in a postal survey with a stratified random sample of 2386 Swiss residents. Our results showed that early appearance of annoyance questions was significantly associated with higher annoyance scores. Questionnaires filled out in autumn were associated with a significantly higher annoyance rating than in the springtime. No effect was found for the order of response alternatives. Standardized average annoyance scores were slightly higher using the 11-point numerical scale whereas the percentage of highly annoyed respondents was higher based on the 5-point scale, using common cutoff points. In conclusion, placement and presentation of annoyance questions within a questionnaire, as well as the time of the year a survey is carried out, have small but demonstrable effects on the degree of self-reported noise annoyance. PMID:27886110

The Complex-Step-Finite-Difference method

NASA Astrophysics Data System (ADS)

Abreu, Rafael; Stich, Daniel; Morales, Jose

2015-07-01

We introduce the Complex-Step-Finite-Difference method (CSFDM) as a generalization of the well-known Finite-Difference method (FDM) for solving the acoustic and elastic wave equations. We have found a direct relationship between modelling the second-order wave equation by the FDM and the first-order wave equation by the CSFDM in 1-D, 2-D and 3-D acoustic media. We present the numerical methodology in order to apply the introduced CSFDM and show an example for wave propagation in simple homogeneous and heterogeneous models. The CSFDM may be implemented as an extension into pre-existing numerical techniques in order to obtain fourth- or sixth-order accurate results with compact three time-level stencils. We compare advantages of imposing various types of initial motion conditions of the CSFDM and demonstrate its higher-order accuracy under the same computational cost and dispersion-dissipation properties. The introduced method can be naturally extended to solve different partial differential equations arising in other fields of science and engineering.

Experimental and numerical analysis of interlocking rib formation at sheet metal blanking

NASA Astrophysics Data System (ADS)

Bolka, Špela; Bratuš, Vitoslav; Starman, Bojan; Mole, Nikolaj

2018-05-01

Cores for electrical motors are typically produced by blanking of laminations and then stacking them together, with, for instance, interlocking ribs or welding. Strict geometrical tolerances, both on the lamination and on the stack, combined with complex part geometry and harder steel strip material, call for use of predictive methods to optimize the process before actual blanking to reduce the costs and speed up the process. One of the major influences on the final stack geometry is the quality of the interlocking ribs. A rib is formed in one step and joined with the rib of the preceding lamination in the next. The quality of the joint determines the firmness of the stack and also influences its. The geometrical and positional accuracy is thus crucial in rib formation process. In this study, a complex experimental and numerical analysis of interlocking rib formation has been performed. The aim of the analysis is to numerically predict the shape of the rib in order to perform a numerical simulation of the stack formation in the next step of the process. A detailed experimental research has been performed in order to characterize influential parameters on the rib formation and the geometry of the ribs itself, using classical and 3D laser microscopy. The formation of the interlocking rib is then simulated using Abaqus Explicit. The Hilll 48 constitutive material model is based on extensive and novel material characterization process, combining data from in-plane and out-of-plane material tests to perform a 3D analysis of both, rib formation and rib joining. The study shows good correlation between the experimental and numerical results.

Numerical investigation of CAI Combustion in the Opposed- Piston Engine with Direct and Indirect Water Injection

NASA Astrophysics Data System (ADS)

Pyszczek, R.; Mazuro, P.; Teodorczyk, A.

2016-09-01

This paper is focused on the CAI combustion control in a turbocharged 2-stroke Opposed-Piston (OP) engine. The barrel type OP engine arrangement is of particular interest for the authors because of its robust design, high mechanical efficiency and relatively easy incorporation of a Variable Compression Ratio (VCR). The other advantage of such design is that combustion chamber is formed between two moving pistons - there is no additional cylinder head to be cooled which directly results in an increased thermal efficiency. Furthermore, engine operation in a Controlled Auto-Ignition (CAI) mode at high compression ratios (CR) raises a possibility of reaching even higher efficiencies and very low emissions. In order to control CAI combustion such measures as VCR and water injection were considered for indirect ignition timing control. Numerical simulations of the scavenging and combustion processes were performed with the 3D CFD multipurpose AVL Fire solver. Numerous cases were calculated with different engine compression ratios and different amounts of directly and indirectly injected water. The influence of the VCR and water injection on the ignition timing and engine performance was determined and their application in the real engine was discussed.

Reflections on Measuring Thinking, while Listening to Mozart's "Jupiter" Symphony.

ERIC Educational Resources Information Center

Wasserman, Selma

1989-01-01

Reflects on educators' current preoccupation with assessment of higher order thinking skills. Easy-to-mark, forced-choice, pencil-and-paper tests with single numerical scores may trivialize the wonderful complexity of human capabilities. Includes 17 references. (MLH)

Collapse for the higher-order nonlinear Schrödinger equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Achilleos, V.; Diamantidis, S.; Frantzeskakis, D. J.

We examine conditions for finite-time collapse of the solutions of the higher-order nonlinear Schr odinger (NLS) equation incorporating third-order dispersion, self-steepening, linear and nonlinear gain and loss, and Raman scattering; this is a system that appears in many physical contexts as a more realistic generalization of the integrable NLS. By using energy arguments, it is found that the collapse dynamics is chiefly controlled by the linear/nonlinear gain/loss strengths. We identify a critical value of the linear gain, separating the possible decay of solutions to the trivial zero-state, from collapse. The numerical simulations, performed for a wide class of initial data,more » are found to be in very good agreement with the analytical results, and reveal long-time stability properties of localized solutions. The role of the higher-order effects to the transient dynamics is also revealed in these simulations.« less

Collapse for the higher-order nonlinear Schrödinger equation

DOE PAGES

Achilleos, V.; Diamantidis, S.; Frantzeskakis, D. J.; ...

2016-02-01

We examine conditions for finite-time collapse of the solutions of the higher-order nonlinear Schr odinger (NLS) equation incorporating third-order dispersion, self-steepening, linear and nonlinear gain and loss, and Raman scattering; this is a system that appears in many physical contexts as a more realistic generalization of the integrable NLS. By using energy arguments, it is found that the collapse dynamics is chiefly controlled by the linear/nonlinear gain/loss strengths. We identify a critical value of the linear gain, separating the possible decay of solutions to the trivial zero-state, from collapse. The numerical simulations, performed for a wide class of initial data,more » are found to be in very good agreement with the analytical results, and reveal long-time stability properties of localized solutions. The role of the higher-order effects to the transient dynamics is also revealed in these simulations.« less

a Recursive Approach to Compute Normal Forms

NASA Astrophysics Data System (ADS)

HSU, L.; MIN, L. J.; FAVRETTO, L.

2001-06-01

Normal forms are instrumental in the analysis of dynamical systems described by ordinary differential equations, particularly when singularities close to a bifurcation are to be characterized. However, the computation of a normal form up to an arbitrary order is numerically hard. This paper focuses on the computer programming of some recursive formulas developed earlier to compute higher order normal forms. A computer program to reduce the system to its normal form on a center manifold is developed using the Maple symbolic language. However, it should be stressed that the program relies essentially on recursive numerical computations, while symbolic calculations are used only for minor tasks. Some strategies are proposed to save computation time. Examples are presented to illustrate the application of the program to obtain high order normalization or to handle systems with large dimension.

Process economics of renewable biorefineries: butanol and ethanol production in integrated bioprocesses from lignocellulosics and other industrial by-products

USDA-ARS?s Scientific Manuscript database

This chapter provides process economic details on production of butanol from lignocellulosic biomass and glycerol in integrated bioreactors where numerous unit operations are combined. In order to compare various processes, economic evaluations were performed using SuperPro Designer Software (versio...

Vibration of initially stressed carbon nanotubes under magneto-thermal environment for nanoparticle delivery via higher-order nonlocal strain gradient theory

NASA Astrophysics Data System (ADS)

Farajpour, M. R.; Shahidi, A. R.; Tabataba'i-Nasab, F.; Farajpour, A.

2018-06-01

In this paper, the forced vibration of a single-walled carbon nanotube (SWCNT) under a moving nanoparticle is investigated based on the higher-order nonlocal strain gradient theory. The SWCNT is subjected to thermo-mechanical stresses and an external longitudinal magnetic field. The influences of higher-order stress gradients in conjunction with the strain gradient nonlocality are taken into account. Using Hamilton's principle and Maxwell's equations, the higher-order differential equations of motion are derived. An analytical solution is obtained for the dynamic deflection of SWCNTs using the Galerkin method. Furthermore, the governing differential equation is solved numerically using the precise integration method. The results of the two solution procedures are compared and an excellent agreement is found between them. Finally, the influences of various scale parameters, the velocity of the moving nanoparticle, the initial axial stress, the temperature change and longitudinal magnetic field on the dynamic response of SWCNTs are investigated.

Pushing Critical Thinking Skills With Multiple-Choice Questions: Does Bloom's Taxonomy Work?

PubMed

Zaidi, Nikki L Bibler; Grob, Karri L; Monrad, Seetha M; Kurtz, Joshua B; Tai, Andrew; Ahmed, Asra Z; Gruppen, Larry D; Santen, Sally A

2018-06-01

Medical school assessments should foster the development of higher-order thinking skills to support clinical reasoning and a solid foundation of knowledge. Multiple-choice questions (MCQs) are commonly used to assess student learning, and well-written MCQs can support learner engagement in higher levels of cognitive reasoning such as application or synthesis of knowledge. Bloom's taxonomy has been used to identify MCQs that assess students' critical thinking skills, with evidence suggesting that higher-order MCQs support a deeper conceptual understanding of scientific process skills. Similarly, clinical practice also requires learners to develop higher-order thinking skills that include all of Bloom's levels. Faculty question writers and examinees may approach the same material differently based on varying levels of knowledge and expertise, and these differences can influence the cognitive levels being measured by MCQs. Consequently, faculty question writers may perceive that certain MCQs require higher-order thinking skills to process the question, whereas examinees may only need to employ lower-order thinking skills to render a correct response. Likewise, seemingly lower-order questions may actually require higher-order thinking skills to respond correctly. In this Perspective, the authors describe some of the cognitive processes examinees use to respond to MCQs. The authors propose that various factors affect both the question writer and examinee's interaction with test material and subsequent cognitive processes necessary to answer a question.

Digital image analysis techniques for fiber and soil mixtures.

DOT National Transportation Integrated Search

1999-05-01

The objective of image processing is to visually enhance, quantify, and/or statistically evaluate some aspect of an image not readily apparent in its original form. Processed digital image data can be analyzed in numerous ways. In order to summarize ...

Scalar conservation and boundedness in simulations of compressible flow

DOE PAGES

Subbareddy, Pramod K.; Kartha, Anand; Candler, Graham V.

2017-08-07

With the proper combination of high-order, low-dissipation numerical methods, physics-based subgrid-scale models, and boundary conditions it is becoming possible to simulate many combustion flows at relevant conditions. However, non-premixed flows are a particular challenge because the thickness of the fuel/oxidizer interface scales inversely with Reynolds number. Sharp interfaces can also be present in the initial or boundary conditions. When higher-order numerical methods are used, there are often aphysical undershoots and overshoots in the scalar variables (e.g.passive scalars, species mass fractions or progress variable). These numerical issues are especially prominent when low-dissipation methods are used, since sharp jumps in flow variablesmore » are not always coincident with regions of strong variation in the scalar fields: consequently, special detection mechanisms and dissipative fluxes are needed. Most numerical methods diffuse the interface, resulting in artificial mixing and spurious reactions. In this paper, we propose a numerical method that mitigates this issue. As a result, we present methods for passive and active scalars, and demonstrate their effectiveness with several examples.« less

Integrating Geochemical Reactions with a Particle-Tracking Approach to Simulate Nitrogen Transport and Transformation in Aquifers

NASA Astrophysics Data System (ADS)

Cui, Z.; Welty, C.; Maxwell, R. M.

2011-12-01

Lagrangian, particle-tracking models are commonly used to simulate solute advection and dispersion in aquifers. They are computationally efficient and suffer from much less numerical dispersion than grid-based techniques, especially in heterogeneous and advectively-dominated systems. Although particle-tracking models are capable of simulating geochemical reactions, these reactions are often simplified to first-order decay and/or linear, first-order kinetics. Nitrogen transport and transformation in aquifers involves both biodegradation and higher-order geochemical reactions. In order to take advantage of the particle-tracking approach, we have enhanced an existing particle-tracking code SLIM-FAST, to simulate nitrogen transport and transformation in aquifers. The approach we are taking is a hybrid one: the reactive multispecies transport process is operator split into two steps: (1) the physical movement of the particles including the attachment/detachment to solid surfaces, which is modeled by a Lagrangian random-walk algorithm; and (2) multispecies reactions including biodegradation are modeled by coupling multiple Monod equations with other geochemical reactions. The coupled reaction system is solved by an ordinary differential equation solver. In order to solve the coupled system of equations, after step 1, the particles are converted to grid-based concentrations based on the mass and position of the particles, and after step 2 the newly calculated concentration values are mapped back to particles. The enhanced particle-tracking code is capable of simulating subsurface nitrogen transport and transformation in a three-dimensional domain with variably saturated conditions. Potential application of the enhanced code is to simulate subsurface nitrogen loading to the Chesapeake Bay and its tributaries. Implementation details, verification results of the enhanced code with one-dimensional analytical solutions and other existing numerical models will be presented in addition to a discussion of implementation challenges.

Optical aberrations induced by subclinical decentrations of the ablation pattern

NASA Astrophysics Data System (ADS)

Mrochen, Michael; Kaemmerer, Maik; Riedel, Peter; Mierdel, Peter; Krinke, Hans-Eberhard; Seiler, Theo

2000-06-01

Purpose: The aim of this work was to study the effect of currently used ablation profiles along with eccentric ablations on the increase of higher order aberrations observed after PRK. Material and Methods: The optical aberrations of 10 eyes were tested before and after PRK. Refractive surgery was performed using a ArF-excimer laser system. In all cases, the ablation zone was 6 mm or larger. The spherical equivalent of the correction was ranging from -2.5 D to -6.0 D. The measured wavefront error was compared to numerical simulations done with the reduced eye model and currently used ablation profiles as well as compared with experimental results obtained from ablation on PMMA balls. Results: The aberration measurements result in a considerable change of the spherical- and coma-like wavefront errors. This result was in good correlation with the numerical simulations and the experimental results. Furthermore, it has been derived that the major contribution on the induced higher order aberrations are a result of the small decentration (less than 1.0 mm) of the ablation zone. Conclusions: Higher order spherical- and coma-like aberrations after PRK are mainly determined by the decentration of the ablation zone during laser refractive surgery. However, future laser systems should use efficient eye-tracking systems and aspherical ablation profiles to overcome this problem.

Comparison of NACA 0012 Laminar Flow Solutions: Structured and Unstructured Grid Methods

NASA Technical Reports Server (NTRS)

Swanson, R. C.; Langer, S.

2016-01-01

In this paper we consider the solution of the compressible Navier-Stokes equations for a class of laminar airfoil flows. The principal objective of this paper is to demonstrate that members of this class of laminar flows have steady-state solutions. These laminar airfoil flow cases are often used to evaluate accuracy, stability and convergence of numerical solution algorithms for the Navier-Stokes equations. In recent years, such flows have also been used as test cases for high-order numerical schemes. While generally consistent steady-state solutions have been obtained for these flows using higher order schemes, a number of results have been published with various solutions, including unsteady ones. We demonstrate with two different numerical methods and a range of meshes with a maximum density that exceeds 8 × 106 grid points that steady-state solutions are obtained. Furthermore, numerical evidence is presented that even when solving the equations with an unsteady algorithm, one obtains steady-state solutions.

Cognitive Science and Instructional Technology: Improvements in Higher Order Thinking Strategies.

ERIC Educational Resources Information Center

Tennyson, Robert D.

This paper examines the cognitive processes associated with higher-order thinking strategies--i.e., cognitive processes directly associated with the employment of knowledge in the service of problem solving and creativity--in order to more clearly define a prescribed instructional method to improve problem-solving skills. The first section of the…

Missing in Action: Writing Process-Based Instructional Practices and Measures of Higher-Order Literacy Achievement in Predominantly Urban Elementary Schools

ERIC Educational Resources Information Center

Briddell, Andrew

2013-01-01

This study of 1,974 fifth grade students investigated potential relationships between writing process-based instruction practices and higher-order thinking measured by a standardized literacy assessment. Writing process is defined as a highly complex, socio-cognitive process that includes: planning, text production, review, metacognition, writing…

Study of stability of the difference scheme for the model problem of the gaslift process

NASA Astrophysics Data System (ADS)

Temirbekov, Nurlan; Turarov, Amankeldy

2017-09-01

The paper studies a model of the gaslift process where the motion in a gas-lift well is described by partial differential equations. The system describing the studied process consists of equations of motion, continuity, equations of thermodynamic state, and hydraulic resistance. A two-layer finite-difference Lax-Vendroff scheme is constructed for the numerical solution of the problem. The stability of the difference scheme for the model problem is investigated using the method of a priori estimates, the order of approximation is investigated, the algorithm for numerical implementation of the gaslift process model is given, and the graphs are presented. The development and investigation of difference schemes for the numerical solution of systems of equations of gas dynamics makes it possible to obtain simultaneously exact and monotonic solutions.

Use of a variational moment method in calculating propagation constants for waveguides with an arbitrary index profile.

PubMed

Hardy, A; Itzkowitz, M; Griffel, G

1989-05-15

A variational moment method is used to calculate propagation constants of 1-D optical waveguides with an arbitrary index profile. The method is applicable to 2-D waveguides as well, and the index profiles need not be symmetric. Examples are given for the lowest-order and the next higher-order modes and are compared with exact numerical solutions.

Plateau inflation from random non-minimal coupling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Broy, Benedict J.; Coone, Dries; Theoretische Natuurkunde,Vrije Universiteit Brussel and The International Solvay Institutes,Pleinlaan 2, B-1050 Brussels

A generic non-minimal coupling can push any higher-order terms of the scalar potential sufficiently far out in field space to yield observationally viable plateau inflation. We provide analytic and numerical evidence that this generically happens for a non-minimal coupling strength ξ of the order N{sub e}{sup 2}. In this regime, the non-minimally coupled field is sub-Planckian during inflation and is thus protected from most higher-order terms. For larger values of ξ, the inflationary predictions converge towards the sweet spot of PLANCK. The latter includes ξ≃10{sup 4} obtained from CMB normalization arguments, thus providing a natural explanation for the inflationary observablesmore » measured.« less

New Models for Velocity/Pressure-Gradient Correlations in Turbulent Boundary Layers

NASA Astrophysics Data System (ADS)

Poroseva, Svetlana; Murman, Scott

2014-11-01

To improve the performance of Reynolds-Averaged Navier-Stokes (RANS) turbulence models, one has to improve the accuracy of models for three physical processes: turbulent diffusion, interaction of turbulent pressure and velocity fluctuation fields, and dissipative processes. The accuracy of modeling the turbulent diffusion depends on the order of a statistical closure chosen as a basis for a RANS model. When the Gram-Charlier series expansions for the velocity correlations are used to close the set of RANS equations, no assumption on Gaussian turbulence is invoked and no unknown model coefficients are introduced into the modeled equations. In such a way, this closure procedure reduces the modeling uncertainty of fourth-order RANS (FORANS) closures. Experimental and direct numerical simulation data confirmed the validity of using the Gram-Charlier series expansions in various flows including boundary layers. We will address modeling the velocity/pressure-gradient correlations. New linear models will be introduced for the second- and higher-order correlations applicable to two-dimensional incompressible wall-bounded flows. Results of models' validation with DNS data in a channel flow and in a zero-pressure gradient boundary layer over a flat plate will be demonstrated. A part of the material is based upon work supported by NASA under award NNX12AJ61A.

Astigmatism transfer phenomena in the optical parametric amplification process

NASA Astrophysics Data System (ADS)

Li, Wenkai; Chen, Yun; Li, Yanyan; Xu, Yi; Guo, Xiaoyang; Lu, Jun; Leng, Yuxin

2017-01-01

We numerically and experimentally investigate the astigmatism transfer phenomena in femtosecond optical parametric amplification (OPA). We model the OPA process based on the coupled second-order three-wave nonlinear propagation equations. The numerical and experimental results support that the input pump pulse astigmatism can be transferred into the idler pulse but not the signal pulse, and the idler pulse astigmatism originating from spatial walk-off is less than the idler pulse astigmatism received from the pump. Thus, we can provide a clear understanding of astigmatism transfer mechanisms in the OPA process, and make better use of broadband tunable OPA sources.

Self-ordering of small-diameter metal nanoparticles by dewetting on hexagonal mesh templates.

PubMed

Meshot, Eric R; Zhao, Zhouzhou; Lu, Wei; Hart, A John

2014-09-07

Arrays of small-diameter nanoparticles with high spatial order are useful for chemical and biological sensors, data storage, synthesis of nanowires and nanotubes, and many other applications. We show that self-ordered metal nanoparticle arrays can be formed by dewetting of thin films on hexagonal mesh substrates made of anodic aluminum oxide (AAO). Upon heating, the metal (Fe) film dewets onto the interstitial sites (i.e., the node points) between pores on the top surface of the AAO. We investigated the particle morphology and dynamics of dewetting using a combination of atomic force microscopy (AFM), grazing-incidence small-angle X-ray scattering (GISAXS), and numerical simulations. Templated metal particles are more monodisperse and have higher local order than those formed by the same dewetting process on flat, nonporous alumina. The degree of order depends on the initial film thickness, and for the optimal thickness tested (nominally 2 nm), we achieved uniform coverage and high order of the particles, comparable to that of the AAO template itself. Computational modeling of dewetting on templates with various pore order and size shows that the order of AAO pores is primarily influential in determining particle position and spacing, while the variance in pore size is less impactful. Potential uses of these ordered nanoparticle arrays on porous materials include plasmonic sensors and spatially controlled catalysts.

Higher order balance control: Distinct effects between cognitive task and manual steadiness constraint on automatic postural responses.

PubMed

Coelho, Daniel Boari; Bourlinova, Catarina; Teixeira, Luis Augusto

2016-12-01

In the present experiment, we aimed to evaluate the interactive effect of performing a cognitive task simultaneously with a manual task requiring either high or low steadiness on APRs. Young volunteers performed the task of recovering upright balance following a mechanical perturbation provoked by unanticipatedly releasing a load pulling the participant's body backwards. The postural task was performed while holding a cylinder steadily on a tray. One group performed that task under high (cylinder' round side down) and another one under low (cylinder' flat side down) manual steadiness constraint. Those tasks were evaluated in the conditions of performing concurrently a cognitive numeric subtraction task and under no cognitive task. Analysis showed that performance of the cognitive task led to increased body and tray displacement, associated with higher displacement at the hip and upper trunk, and lower magnitude of activation of the GM muscle in response to the perturbation. Conversely, high manual steadiness constraint led to reduced tray velocity in association with lower values of trunk displacement, and decreased rotation amplitude at the ankle and hip joints. We found no interactions between the effects of the cognitive and manual tasks on APRs, suggesting that they were processed in parallel in the generation of responses for balance recovery. Modulation of postural responses from the manual and cognitive tasks indicates participation of higher order neural structures in the generation of APRs, with postural responses being affected by multiple mental processes occurring in parallel. Copyright © 2016 Elsevier B.V. All rights reserved.

Numerical simulation of complex part manufactured by selective laser melting process

NASA Astrophysics Data System (ADS)

Van Belle, Laurent

2017-10-01

Selective Laser Melting (SLM) process belonging to the family of the Additive Manufacturing (AM) technologies, enable to build parts layer by layer, from metallic powder and a CAD model. Physical phenomena that occur in the process have the same issues as conventional welding. Thermal gradients generate significant residual stresses and distortions in the parts. Moreover, the large and complex parts to manufacturing, accentuate the undesirable effects. Therefore, it is essential for manufacturers to offer a better understanding of the process and to ensure production reliability of parts with high added value. This paper focuses on the simulation of manufacturing turbine by SLM process in order to calculate residual stresses and distortions. Numerical results will be presented.

Characterization of the Ionospheric Scintillations at High Latitude using GPS Signal

NASA Astrophysics Data System (ADS)

Mezaoui, H.; Hamza, A. M.; Jayachandran, P. T.

2013-12-01

Transionospheric radio signals experience both amplitude and phase variations as a result of propagation through a turbulent ionosphere; this phenomenon is known as ionospheric scintillations. As a result of these fluctuations, Global Positioning System (GPS) receivers lose track of signals and consequently induce position and navigational errors. Therefore, there is a need to study these scintillations and their causes in order to not only resolve the navigational problem but in addition develop analytical and numerical radio propagation models. In order to quantify and qualify these scintillations, we analyze the probability distribution functions (PDFs) of L1 GPS signals at 50 Hz sampling rate using the Canadian High arctic Ionospheric Network (CHAIN) measurements. The raw GPS signal is detrended using a wavelet-based technique and the detrended amplitude and phase of the signal are used to construct probability distribution functions (PDFs) of the scintillating signal. The resulting PDFs are non-Gaussian. From the PDF functional fits, the moments are estimated. The results reveal a general non-trivial parabolic relationship between the normalized fourth and third moments for both the phase and amplitude of the signal. The calculated higher-order moments of the amplitude and phase distribution functions will help quantify some of the scintillation characteristics and in the process provide a base for forecasting, i.e. develop a scintillation climatology model. This statistical analysis, including power spectra, along with a numerical simulation will constitute the backbone of a high latitude scintillation model.

Second-order relational face processing is applied to faces of different race and photographic contrast.

PubMed

Matheson, H E; Bilsbury, T G; McMullen, P A

2012-03-01

A large body of research suggests that faces are processed by a specialized mechanism within the human visual system. This specialized mechanism is made up of subprocesses (Maurer, LeGrand, & Mondloch, 2002). One subprocess, called second- order relational processing, analyzes the metric distances between face parts. Importantly, it is well established that other-race faces and contrast-reversed faces are associated with impaired performance on numerous face processing tasks. Here, we investigated the specificity of second-order relational processing by testing how this process is applied to faces of different race and photographic contrast. Participants completed a feature displacement discrimination task, directly measuring the sensitivity to second-order relations between face parts. Across three experiments we show that, despite absolute differences in sensitivity in some conditions, inversion impaired performance in all conditions. The presence of robust inversion effects for all faces suggests that second-order relational processing can be applied to faces of different race and photographic contrast.

Higher-derivative operators and effective field theory for general scalar-tensor theories

NASA Astrophysics Data System (ADS)

Solomon, Adam R.; Trodden, Mark

2018-02-01

We discuss the extent to which it is necessary to include higher-derivative operators in the effective field theory of general scalar-tensor theories. We explore the circumstances under which it is correct to restrict to second-order operators only, and demonstrate this using several different techniques, such as reduction of order and explicit field redefinitions. These methods are applied, in particular, to the much-studied Horndeski theories. The goal is to clarify the application of effective field theory techniques in the context of popular cosmological models, and to explicitly demonstrate how and when higher-derivative operators can be cast into lower-derivative forms suitable for numerical solution techniques.

ULTRA-SHARP solution of the Smith-Hutton problem

NASA Technical Reports Server (NTRS)

Leonard, B. P.; Mokhtari, Simin

1992-01-01

Highly convective scalar transport involving near-discontinuities and strong streamline curvature was addressed in a paper by Smith and Hutton in 1982, comparing several different convection schemes applied to a specially devised test problem. First order methods showed significant artificial diffusion, whereas higher order methods gave less smearing but had a tendency to overshoot and oscillate. Perhaps because unphysical oscillations are more obvious than unphysical smearing, the intervening period has seen a rise in popularity of low order artificially diffusive schemes, especially in the numerical heat transfer industry. The present paper describes an alternate strategy of using non-artificially diffusive high order methods, while maintaining strictly monotonic transitions through the use of simple flux limited constraints. Limited third order upwinding is usually found to be the most cost effective basic convection scheme. Tighter resolution of discontinuities can be obtained at little additional cost by using automatic adaptive stencil expansion to higher order in local regions, as needed.

Ice-sheet modelling accelerated by graphics cards

NASA Astrophysics Data System (ADS)

Brædstrup, Christian Fredborg; Damsgaard, Anders; Egholm, David Lundbek

2014-11-01

Studies of glaciers and ice sheets have increased the demand for high performance numerical ice flow models over the past decades. When exploring the highly non-linear dynamics of fast flowing glaciers and ice streams, or when coupling multiple flow processes for ice, water, and sediment, researchers are often forced to use super-computing clusters. As an alternative to conventional high-performance computing hardware, the Graphical Processing Unit (GPU) is capable of massively parallel computing while retaining a compact design and low cost. In this study, we present a strategy for accelerating a higher-order ice flow model using a GPU. By applying the newest GPU hardware, we achieve up to 180× speedup compared to a similar but serial CPU implementation. Our results suggest that GPU acceleration is a competitive option for ice-flow modelling when compared to CPU-optimised algorithms parallelised by the OpenMP or Message Passing Interface (MPI) protocols.

Terabit bandwidth-adaptive transmission using low-complexity format-transparent digital signal processing.

PubMed

Zhuge, Qunbi; Morsy-Osman, Mohamed; Chagnon, Mathieu; Xu, Xian; Qiu, Meng; Plant, David V

2014-02-10

In this paper, we propose a low-complexity format-transparent digital signal processing (DSP) scheme for next generation flexible and energy-efficient transceiver. It employs QPSK symbols as the training and pilot symbols for the initialization and tracking stage of the receiver-side DSP, respectively, for various modulation formats. The performance is numerically and experimentally evaluated in a dual polarization (DP) 11 Gbaud 64QAM system. Employing the proposed DSP scheme, we conduct a system-level study of Tb/s bandwidth-adaptive superchannel transmissions with flexible modulation formats including QPSK, 8QAM and 16QAM. The spectrum bandwidth allocation is realized in the digital domain instead of turning on/off sub-channels, which improves the performance of higher order QAM. Various transmission distances ranging from 240 km to 6240 km are demonstrated with a colorless detection for hardware complexity reduction.

Transitions of stationary to pulsating solutions in the complex cubic-quintic Ginzburg-Landau equation under the influence of nonlinear gain and higher-order effects

NASA Astrophysics Data System (ADS)

Uzunov, Ivan M.; Georgiev, Zhivko D.; Arabadzhiev, Todor N.

2018-05-01

In this paper we study the transitions of stationary to pulsating solutions in the complex cubic-quintic Ginzburg-Landau equation (CCQGLE) under the influence of nonlinear gain, its saturation, and higher-order effects: self-steepening, third-order of dispersion, and intrapulse Raman scattering in the anomalous dispersion region. The variation method and the method of moments are applied in order to obtain the dynamic models with finite degrees of freedom for the description of stationary and pulsating solutions. Having applied the first model and its bifurcation analysis we have discovered the existence of families of subcritical Poincaré-Andronov-Hopf bifurcations due to the intrapulse Raman scattering, as well as some small nonlinear gain and the saturation of the nonlinear gain. A phenomenon of nonlinear stability has been studied and it has been shown that long living pulsating solutions with relatively small fluctuations of amplitude and frequencies exist at the bifurcation point. The numerical analysis of the second model has revealed the existence of Poincaré-Andronov-Hopf bifurcations of Raman dissipative soliton under the influence of the self-steepening effect and large nonlinear gain. All our theoretical predictions have been confirmed by the direct numerical solution of the full perturbed CCQGLE. The detailed comparison between the results obtained by both dynamic models and the direct numerical solution of the perturbed CCQGLE has proved the applicability of the proposed models in the investigation of the solutions of the perturbed CCQGLE.

Using Reflection to Develop Higher Order Processes

ERIC Educational Resources Information Center

Lerch, Carol; Bilics, Andrea; Colley, Binta

2006-01-01

The main purpose of this study was to look at how we used specific writing assignments in our courses to encourage metacognitive reflection in order to increase the learning that takes place. The study also aimed to aid in the development of higher order processing skills through the development of student reflection. The students involved in the…

Higher-Order Squeezing of Quantum Field and the Generalized Uncertainty Relations in Non-Degenerate Four-Wave Mixing

NASA Technical Reports Server (NTRS)

Li, Xi-Zeng; Su, Bao-Xia

1996-01-01

It is found that the field of the combined mode of the probe wave and the phase-conjugate wave in the process of non-degenerate four-wave mixing exhibits higher-order squeezing to all even orders. And the generalized uncertainty relations in this process are also presented.

Towards a More Precise Conceptualization of Empathy: An Integrative Review of Literature on Definitions, Associated Functions, and Developmental Trajectories

ERIC Educational Resources Information Center

Zurek, Peter Paul; Scheithauer, Herbert

2017-01-01

Empathy entails basic cognitive processes such as the recognition of facial expressions and basic emotional processes such as emotional contagion, but also higher-order cognitive processes such as abstract reasoning about the other person's emotional states and higher-order emotional processes such as empathic concern. Thus, empathy must be…

Few-cycle optical rogue waves: complex modified Korteweg-de Vries equation.

PubMed

He, Jingsong; Wang, Lihong; Li, Linjing; Porsezian, K; Erdélyi, R

2014-06-01

In this paper, we consider the complex modified Korteweg-de Vries (mKdV) equation as a model of few-cycle optical pulses. Using the Lax pair, we construct a generalized Darboux transformation and systematically generate the first-, second-, and third-order rogue wave solutions and analyze the nature of evolution of higher-order rogue waves in detail. Based on detailed numerical and analytical investigations, we classify the higher-order rogue waves with respect to their intrinsic structure, namely, fundamental pattern, triangular pattern, and ring pattern. We also present several new patterns of the rogue wave according to the standard and nonstandard decomposition. The results of this paper explain the generalization of higher-order rogue waves in terms of rational solutions. We apply the contour line method to obtain the analytical formulas of the length and width of the first-order rogue wave of the complex mKdV and the nonlinear Schrödinger equations. In nonlinear optics, the higher-order rogue wave solutions found here will be very useful to generate high-power few-cycle optical pulses which will be applicable in the area of ultrashort pulse technology.

Higher order solution of the Euler equations on unstructured grids using quadratic reconstruction

NASA Technical Reports Server (NTRS)

Barth, Timothy J.; Frederickson, Paul O.

1990-01-01

High order accurate finite-volume schemes for solving the Euler equations of gasdynamics are developed. Central to the development of these methods are the construction of a k-exact reconstruction operator given cell-averaged quantities and the use of high order flux quadrature formulas. General polygonal control volumes (with curved boundary edges) are considered. The formulations presented make no explicit assumption as to complexity or convexity of control volumes. Numerical examples are presented for Ringleb flow to validate the methodology.

Potential predictability and forecast skill in ensemble climate forecast: the skill-persistence rule

NASA Astrophysics Data System (ADS)

Jin, Y.; Rong, X.; Liu, Z.

2017-12-01

This study investigates the factors that impact the forecast skill for the real world (actual skill) and perfect model (perfect skill) in ensemble climate model forecast with a series of fully coupled general circulation model forecast experiments. It is found that the actual skill of sea surface temperature (SST) in seasonal forecast is substantially higher than the perfect skill on a large part of the tropical oceans, especially the tropical Indian Ocean and the central-eastern Pacific Ocean. The higher actual skill is found to be related to the higher observational SST persistence, suggesting a skill-persistence rule: a higher SST persistence in the real world than in the model could overwhelm the model bias to produce a higher forecast skill for the real world than for the perfect model. The relation between forecast skill and persistence is further examined using a first-order autoregressive model (AR1) analytically for theoretical solutions and numerically for analogue experiments. The AR1 model study shows that the skill-persistence rule is strictly valid in the case of infinite ensemble size, but can be distorted by the sampling error and non-AR1 processes.

Higher-order triangular spectral element method with optimized cubature points for seismic wavefield modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Youshan, E-mail: ysliu@mail.iggcas.ac.cn; Teng, Jiwen, E-mail: jwteng@mail.iggcas.ac.cn; Xu, Tao, E-mail: xutao@mail.iggcas.ac.cn

2017-05-01

The mass-lumped method avoids the cost of inverting the mass matrix and simultaneously maintains spatial accuracy by adopting additional interior integration points, known as cubature points. To date, such points are only known analytically in tensor domains, such as quadrilateral or hexahedral elements. Thus, the diagonal-mass-matrix spectral element method (SEM) in non-tensor domains always relies on numerically computed interpolation points or quadrature points. However, only the cubature points for degrees 1 to 6 are known, which is the reason that we have developed a p-norm-based optimization algorithm to obtain higher-order cubature points. In this way, we obtain and tabulate newmore » cubature points with all positive integration weights for degrees 7 to 9. The dispersion analysis illustrates that the dispersion relation determined from the new optimized cubature points is comparable to that of the mass and stiffness matrices obtained by exact integration. Simultaneously, the Lebesgue constant for the new optimized cubature points indicates its surprisingly good interpolation properties. As a result, such points provide both good interpolation properties and integration accuracy. The Courant–Friedrichs–Lewy (CFL) numbers are tabulated for the conventional Fekete-based triangular spectral element (TSEM), the TSEM with exact integration, and the optimized cubature-based TSEM (OTSEM). A complementary study demonstrates the spectral convergence of the OTSEM. A numerical example conducted on a half-space model demonstrates that the OTSEM improves the accuracy by approximately one order of magnitude compared to the conventional Fekete-based TSEM. In particular, the accuracy of the 7th-order OTSEM is even higher than that of the 14th-order Fekete-based TSEM. Furthermore, the OTSEM produces a result that can compete in accuracy with the quadrilateral SEM (QSEM). The high accuracy of the OTSEM is also tested with a non-flat topography model. In terms of computational efficiency, the OTSEM is more efficient than the Fekete-based TSEM, although it is slightly costlier than the QSEM when a comparable numerical accuracy is required. - Highlights: • Higher-order cubature points for degrees 7 to 9 are developed. • The effects of quadrature rule on the mass and stiffness matrices has been conducted. • The cubature points have always positive integration weights. • Freeing from the inversion of a wide bandwidth mass matrix. • The accuracy of the TSEM has been improved in about one order of magnitude.« less

Effects of Extreme Prematurity on Numerical Skills and Executive Function in Kindergarten Children: An Application of Partially Ordered Classification Modeling

PubMed Central

Tatsuoka, Curtis; McGowan, Bridget; Yamada, Tomoko; Espy, Kimberly Andrews; Minich, Nori; Taylor, H. Gerry

2016-01-01

Although mathematics disabilities (MD) are common in extremely preterm/extremely low birth weight (EPT/ELBW) children, little is known about the nature of these problems. In this study partially ordered set (POSET) models were applied to classify 140 EPT/ELBW kindergarten children (gestational age <28 weeks and/or birth weight <1000 g) and 110 normal birth weight (NBW) controls into profiles of numerical and cognitive skills. Models based on five numerical skills and five executive function and processing speed skills provided a good fit to performance data. The EPT/ELBW group had poorer skills in all areas than NBW controls but the models also revealed substantial individual variability in skill profiles. Weaknesses in executive function were associated with poorer mastery of numerical skills. The findings illustrate the applicability of POSET models to research on MD and suggest distinct types of early numerical deficits in EPT/ELBW children that are related to their impairments in executive function. PMID:27818602

Effects of Extreme Prematurity on Numerical Skills and Executive Function in Kindergarten Children: An Application of Partially Ordered Classification Modeling.

PubMed

Tatsuoka, Curtis; McGowan, Bridget; Yamada, Tomoko; Espy, Kimberly Andrews; Minich, Nori; Taylor, H Gerry

2016-07-01

Although mathematics disabilities (MD) are common in extremely preterm/extremely low birth weight (EPT/ELBW) children, little is known about the nature of these problems. In this study partially ordered set (POSET) models were applied to classify 140 EPT/ELBW kindergarten children (gestational age <28 weeks and/or birth weight <1000 g) and 110 normal birth weight (NBW) controls into profiles of numerical and cognitive skills. Models based on five numerical skills and five executive function and processing speed skills provided a good fit to performance data. The EPT/ELBW group had poorer skills in all areas than NBW controls but the models also revealed substantial individual variability in skill profiles. Weaknesses in executive function were associated with poorer mastery of numerical skills. The findings illustrate the applicability of POSET models to research on MD and suggest distinct types of early numerical deficits in EPT/ELBW children that are related to their impairments in executive function.

Multiple scattering contribution to the diffuse light of a night sky: A model which embraces all orders of scattering

NASA Astrophysics Data System (ADS)

Kocifaj, Miroslav

2018-02-01

The mechanism in which multiple scattering influences the radiance of a night sky has been poorly quantified until recently, or even completely unknown from the theoretical point of view. In this paper, the relative contribution of higher-scattering radiances to the total sky radiance is treated analytically for all orders of scattering, showing that a fast and accurate numerical solution to the problem exists. Unlike a class of ray tracing codes in which CPU requirements increase tremendously with each new scattering mode, the solution developed here requires the same processor time for each scattering mode. This allows for rapid estimation of higher-scattering radiances and residual error that is otherwise unknown if these radiances remain undetermined. Such convergence testing is necessary to guarantee accuracy and the stability of the numerical predictions. The performance of the method developed here is demonstrated in a set of numerical experiments aiming to uncover the relative importance of higher-scattering radiances at different distances from a light source. We have shown, that multiple scattering effects are generally low if distance to the light source is below 30 km. At large distances the multiple scattering can become important at the dark sky elements situated opposite to the light source. However, the brightness at this part of sky is several orders of magnitude smaller than that of a glowing dome of light over a city, so we do not expect that a partial increase or even doubling the radiance of otherwise dark sky elements can noticeably affect astronomical observations or living organisms (including humans). Single scattering is an appropriate approximation to the sky radiance of a night sky in the vast majority of cases.

Modelling polymeric deformable granular materials - from experimental data to numerical models at the grain scale

NASA Astrophysics Data System (ADS)

Teil, Maxime; Harthong, Barthélémy; Imbault, Didier; Peyroux, Robert

2017-06-01

Polymeric deformable granular materials are widely used in industry and the understanding and the modelling of their shaping process is a point of interest. This kind of materials often presents a viscoelasticplastic behaviour and the present study promotes a joint approach between numerical simulations and experiments in order to derive the behaviour law of such granular material. The experiment is conducted on a polystyrene powder on which a confining pressure of 7MPa and an axial pressure reaching 30MPa are applied. Between different steps of the in-situ test, the sample is scanned in an X-rays microtomograph in order to know the structure of the material depending on the density. From the tomographic images and by using specific algorithms to improve the images quality, grains are automatically identified, separated and a finite element mesh is generated. The long-term objective of this study is to derive a representative sample directly from the experiments in order to run numerical simulations using a viscoelactic or viscoelastic-plastic constitutive law and compare numerical and experimental results at the particle scale.

Cirrus clouds. I - A cirrus cloud model. II - Numerical experiments on the formation and maintenance of cirrus

NASA Technical Reports Server (NTRS)

Starr, D. OC.; Cox, S. K.

1985-01-01

A simplified cirrus cloud model is presented which may be used to investigate the role of various physical processes in the life cycle of a cirrus cloud. The model is a two-dimensional, time-dependent, Eulerian numerical model where the focus is on cloud-scale processes. Parametrizations are developed to account for phase changes of water, radiative processes, and the effects of microphysical structure on the vertical flux of ice water. The results of a simulation of a thin cirrostratus cloud are given. The results of numerical experiments performed with the model are described in order to demonstrate the important role of cloud-scale processes in determining the cloud properties maintained in response to larger scale forcing. The effects of microphysical composition and radiative processes are considered, as well as their interaction with thermodynamic and dynamic processes within the cloud. It is shown that cirrus clouds operate in an entirely different manner than liquid phase stratiform clouds.

Time and length scales within a fire and implications for numerical simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

TIESZEN,SHELDON R.

2000-02-02

A partial non-dimensionalization of the Navier-Stokes equations is used to obtain order of magnitude estimates of the rate-controlling transport processes in the reacting portion of a fire plume as a function of length scale. Over continuum length scales, buoyant times scales vary as the square root of the length scale; advection time scales vary as the length scale, and diffusion time scales vary as the square of the length scale. Due to the variation with length scale, each process is dominant over a given range. The relationship of buoyancy and baroclinc vorticity generation is highlighted. For numerical simulation, first principlesmore » solution for fire problems is not possible with foreseeable computational hardware in the near future. Filtered transport equations with subgrid modeling will be required as two to three decades of length scale are captured by solution of discretized conservation equations. By whatever filtering process one employs, one must have humble expectations for the accuracy obtainable by numerical simulation for practical fire problems that contain important multi-physics/multi-length-scale coupling with up to 10 orders of magnitude in length scale.« less

The Symbol Grounding Problem Revisited: A Thorough Evaluation of the ANS Mapping Account and the Proposal of an Alternative Account Based on Symbol–Symbol Associations

PubMed Central

Reynvoet, Bert; Sasanguie, Delphine

2016-01-01

Recently, a lot of studies in the domain of numerical cognition have been published demonstrating a robust association between numerical symbol processing and individual differences in mathematics achievement. Because numerical symbols are so important for mathematics achievement, many researchers want to provide an answer on the ‘symbol grounding problem,’ i.e., how does a symbol acquires its numerical meaning? The most popular account, the approximate number system (ANS) mapping account, assumes that a symbol acquires its numerical meaning by being mapped on a non-verbal and ANS. Here, we critically evaluate four arguments that are supposed to support this account, i.e., (1) there is an evolutionary system for approximate number processing, (2) non-symbolic and symbolic number processing show the same behavioral effects, (3) non-symbolic and symbolic numbers activate the same brain regions which are also involved in more advanced calculation and (4) non-symbolic comparison is related to the performance on symbolic mathematics achievement tasks. Based on this evaluation, we conclude that all of these arguments and consequently also the mapping account are questionable. Next we explored less popular alternative, where small numerical symbols are initially mapped on a precise representation and then, in combination with increasing knowledge of the counting list result in an independent and exact symbolic system based on order relations between symbols. We evaluate this account by reviewing evidence on order judgment tasks following the same four arguments. Although further research is necessary, the available evidence so far suggests that this symbol–symbol association account should be considered as a worthy alternative of how symbols acquire their meaning. PMID:27790179

A Novel Numerical Method for Fuzzy Boundary Value Problems

NASA Astrophysics Data System (ADS)

Can, E.; Bayrak, M. A.; Hicdurmaz

2016-05-01

In the present paper, a new numerical method is proposed for solving fuzzy differential equations which are utilized for the modeling problems in science and engineering. Fuzzy approach is selected due to its important applications on processing uncertainty or subjective information for mathematical models of physical problems. A second-order fuzzy linear boundary value problem is considered in particular due to its important applications in physics. Moreover, numerical experiments are presented to show the effectiveness of the proposed numerical method on specific physical problems such as heat conduction in an infinite plate and a fin.

A model of the hierarchy of behaviour, cognition, and consciousness.

PubMed

Toates, Frederick

2006-03-01

Processes comparable in important respects to those underlying human conscious and non-conscious processing can be identified in a range of species and it is argued that these reflect evolutionary precursors of the human processes. A distinction is drawn between two types of processing: (1) stimulus-based and (2) higher-order. For 'higher-order,' in humans the operations of processing are themselves associated with conscious awareness. Conscious awareness sets the context for stimulus-based processing and its end-point is accessible to conscious awareness. However, the mechanics of the translation between stimulus and response proceeds without conscious control. The paper argues that higher-order processing is an evolutionary addition to stimulus-based processing. The model's value is shown for gaining insight into a range of phenomena and their link with consciousness. These include brain damage, learning, memory, development, vision, emotion, motor control, reasoning, the voluntary versus involuntary debate, and mental disorder.

Current Research on Relationships between Selected Higher Order Processes and the Communication Skills and Problems of Deaf Persons.

ERIC Educational Resources Information Center

Metz, Dale Evan; And Others

1980-01-01

The paper presents four research projects in process in the Communication Sciences Laboratory at the National Technical Institute for the Deaf. These projects illustrate four broad areas of research on the relationships between higher order information processing systems and the communication skills and problems exhibited by deaf people. (Author)

Numerical study of Si nanoparticle formation by SiCl4 hydrogenation in RF plasma

NASA Astrophysics Data System (ADS)

Rehmet, Christophe; Cao, Tengfei; Cheng, Yi

2016-04-01

Nanocrystalline silicon (nc-Si) is a promising material for many applications related to electronics and optoelectronics. This work performs numerical simulations in order to understand a new process with high deposition rate production of nc-Si in a radio-frequency plasma reactor. Inductive plasma formation, reaction kinetics and nanoparticle formation have been considered in a sophisticated model. Results show that the plasma parameters could be adjusted in order to improve selectivity between nanoparticle and molecule formation and, thus, the deposition rate. Also, a parametric study helps to optimize the system with appropriate operating conditions.

Testing higher-order Lagrangian perturbation theory against numerical simulation. 1: Pancake models

NASA Technical Reports Server (NTRS)

Buchert, T.; Melott, A. L.; Weiss, A. G.

1993-01-01

We present results showing an improvement of the accuracy of perturbation theory as applied to cosmological structure formation for a useful range of quasi-linear scales. The Lagrangian theory of gravitational instability of an Einstein-de Sitter dust cosmogony investigated and solved up to the third order is compared with numerical simulations. In this paper we study the dynamics of pancake models as a first step. In previous work the accuracy of several analytical approximations for the modeling of large-scale structure in the mildly non-linear regime was analyzed in the same way, allowing for direct comparison of the accuracy of various approximations. In particular, the Zel'dovich approximation (hereafter ZA) as a subclass of the first-order Lagrangian perturbation solutions was found to provide an excellent approximation to the density field in the mildly non-linear regime (i.e. up to a linear r.m.s. density contrast of sigma is approximately 2). The performance of ZA in hierarchical clustering models can be greatly improved by truncating the initial power spectrum (smoothing the initial data). We here explore whether this approximation can be further improved with higher-order corrections in the displacement mapping from homogeneity. We study a single pancake model (truncated power-spectrum with power-spectrum with power-index n = -1) using cross-correlation statistics employed in previous work. We found that for all statistical methods used the higher-order corrections improve the results obtained for the first-order solution up to the stage when sigma (linear theory) is approximately 1. While this improvement can be seen for all spatial scales, later stages retain this feature only above a certain scale which is increasing with time. However, third-order is not much improvement over second-order at any stage. The total breakdown of the perturbation approach is observed at the stage, where sigma (linear theory) is approximately 2, which corresponds to the onset of hierarchical clustering. This success is found at a considerable higher non-linearity than is usual for perturbation theory. Whether a truncation of the initial power-spectrum in hierarchical models retains this improvement will be analyzed in a forthcoming work.

SU(3) Landau gauge gluon and ghost propagators using the logarithmic lattice gluon field definition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ilgenfritz, Ernst-Michael; Humboldt-Universitaet zu Berlin, Institut fuer Physik, 12489 Berlin; Menz, Christoph

2011-03-01

We study the Landau gauge gluon and ghost propagators of SU(3) gauge theory, employing the logarithmic definition for the lattice gluon fields and implementing the corresponding form of the Faddeev-Popov matrix. This is necessary in order to consistently compare lattice data for the bare propagators with that of higher-loop numerical stochastic perturbation theory. In this paper we provide such a comparison, and introduce what is needed for an efficient lattice study. When comparing our data for the logarithmic definition to that of the standard lattice Landau gauge we clearly see the propagators to be multiplicatively related. The data of themore » associated ghost-gluon coupling matches up almost completely. For the explored lattice spacings and sizes discretization artifacts, finite size, and Gribov-copy effects are small. At weak coupling and large momentum, the bare propagators and the ghost-gluon coupling are seen to be approached by those of higher-order numerical stochastic perturbation theory.« less

Unpacking symbolic number comparison and its relation with arithmetic in adults.

PubMed

Sasanguie, Delphine; Lyons, Ian M; De Smedt, Bert; Reynvoet, Bert

2017-08-01

Symbolic number - or digit - comparison has been a central tool in the domain of numerical cognition for decades. More recently, individual differences in performance on this task have been shown to robustly relate to individual differences in more complex math processing - a result that has been replicated across many different age groups. In this study, we 'unpack' the underlying components of digit comparison (i.e. digit identification, digit to number-word matching, digit ordering and general comparison) in a sample of adults. In a first experiment, we showed that digit comparison performance was most strongly related to digit ordering ability - i.e., the ability to judge whether symbolic numbers are in numerical order. Furthermore, path analyses indicated that the relation between digit comparison and arithmetic was partly mediated by digit ordering and fully mediated when non-numerical (letter) ordering was also entered into the model. In a second experiment, we examined whether a general order working memory component could account for the relation between digit comparison and arithmetic. It could not. Instead, results were more consistent with the notion that fluent access and activation of long-term stored associations between numbers explains the relation between arithmetic and both digit comparison and digit ordering tasks. Copyright © 2017 Elsevier B.V. All rights reserved.

Extremely Fast Numerical Integration of Ocean Surface Wave Dynamics

DTIC Science & Technology

2007-09-30

sub-processor must be added as shown in the blue box of Fig. 1. We first consider the Kadomtsev - Petviashvili (KP) equation ηt + coηx +αηηx + βη ...analytic integration of the so-called “soliton equations ,” I have discovered how the GFT can be used to solved higher order equations for which study...analytical study and extremely fast numerical integration of the extended nonlinear Schroedinger equation for fully three dimensional wave motion

Modulation instability, Akhmediev breathers, and rogue waves in nonlinear fiber optics

NASA Astrophysics Data System (ADS)

Dudley, John M.; Genty, Go"ry; Dias, Frederic; Kibler, Bertrand; Akhmediev, Nail

2010-02-01

The development of the supercontinuum spectrum in the quasi-CW regime is studied analytically, numerically and experimentally. An interpretation in terms of localized periodic structures known as "Akhmediev Breathers" is proposed. Theory, numerical simulation and experiment are in excellent agreement. We also briefly consider the role of breather collisions in the presence of higher order dispersion and show that they lead to the formation of very large amplitude localized structures that may be analogous to the infamous oceanic rogue waves.

Numerical study on the Welander oscillatory natural circulation problem using high-order numerical methods

DOE PAGES

Zou, Ling; Zhao, Haihua; Kim, Seung Jun

2016-11-16

In this study, the classical Welander’s oscillatory natural circulation problem is investigated using high-order numerical methods. As originally studied by Welander, the fluid motion in a differentially heated fluid loop can exhibit stable, weakly instable, and strongly instable modes. A theoretical stability map has also been originally derived from the stability analysis. Numerical results obtained in this paper show very good agreement with Welander’s theoretical derivations. For stable cases, numerical results from both the high-order and low-order numerical methods agree well with the non-dimensional flow rate analytically derived. The high-order numerical methods give much less numerical errors compared to themore » low-order methods. For stability analysis, the high-order numerical methods could perfectly predict the stability map, while the low-order numerical methods failed to do so. For all theoretically unstable cases, the low-order methods predicted them to be stable. The result obtained in this paper is a strong evidence to show the benefits of using high-order numerical methods over the low-order ones, when they are applied to simulate natural circulation phenomenon that has already gain increasing interests in many future nuclear reactor designs.« less

Role of structural inheritance on present-day deformation in intraplate domains

NASA Astrophysics Data System (ADS)

Tarayoun, A.; Mazzotti, S.; Gueydan, F.

2017-12-01

Understanding the role of structural inheritance on present day surface deformation is a key element for better characterizing the dynamism of intraplate earthquakes. Current deformation and seismicity are poorly understood phenomenon in intra-continental domains. A commonly used hypothesis, based on observations, suggests that intraplate deformation is related to the reactivation of large tectonic paleo-structures, which can act as locally weakened domains. The objective of our study is to quantify the impact of these weakened areas on present-day strain localizations and rates. We combine GPS observations and numerical modeling to analyze the role of structural inheritance on strain rates, with specific observations along the St. Lawrence Valley of eastern Canada. We processed 143 GPS stations from five different networks, in particular one dense campaign network situated along a recognized major normal faults system of the Iapetus paleo-rift, in order to accurately determine the GPS velocities and strain rates. Results of strain rates show magnitude varying from 1.5x10-10 to 6.8x10-9 yr-1 in the St Lawrence valley. Weakened area strain rates are up to one order of magnitude higher than surrounding areas. We compare strain rates inferred from GPS and the new postglacial rebound model. We found that GPS signal is one order of magnitude higher in the weakened zone, which is likely due to structural inheritance. The numerical modeling investigates the steady-state deformation of the continental lithosphere with presence of a weak area. Our new approach integrates ductile structural inheritance using a weakening coefficient that decreases the lithosphere strength at different depths. This allows studying crustal strain rates mainly as a function of rheological contrast and geometry of the weakened domains. Comparison between model predictions and observed GPS strain rates will allow us to investigate the respective role of crustal and mantle tectonic inheritance.

Conceptual Design Optimization of an Augmented Stability Aircraft Incorporating Dynamic Response and Actuator Constraints

NASA Technical Reports Server (NTRS)

Welstead, Jason; Crouse, Gilbert L., Jr.

2014-01-01

Empirical sizing guidelines such as tail volume coefficients have long been used in the early aircraft design phases for sizing stabilizers, resulting in conservatively stable aircraft. While successful, this results in increased empty weight, reduced performance, and greater procurement and operational cost relative to an aircraft with optimally sized surfaces. Including flight dynamics in the conceptual design process allows the design to move away from empirical methods while implementing modern control techniques. A challenge of flight dynamics and control is the numerous design variables, which are changing fluidly throughout the conceptual design process, required to evaluate the system response to some disturbance. This research focuses on addressing that challenge not by implementing higher order tools, such as computational fluid dynamics, but instead by linking the lower order tools typically used within the conceptual design process so each discipline feeds into the other. In thisresearch, flight dynamics and control was incorporated into the conceptual design process along with the traditional disciplines of vehicle sizing, weight estimation, aerodynamics, and performance. For the controller, a linear quadratic regulator structure with constant gains has been specified to reduce the user input. Coupling all the disciplines in the conceptual design phase allows the aircraft designer to explore larger design spaces where stabilizers are sized according to dynamic response constraints rather than historical static margin and volume coefficient guidelines.

A trust-region algorithm for the optimization of PSA processes using reduced-order modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agarwal, A.; Biegler, L.; Zitney, S.

2009-01-01

The last few decades have seen a considerable increase in the applications of adsorptive gas separation technologies, such as pressure swing adsorption (PSA); the applications range from bulk separations to trace contaminant removal. PSA processes are based on solid-gas equilibrium and operate under periodic transient conditions [1]. Bed models for these processes are therefore defined by coupled nonlinear partial differential and algebraic equations (PDAEs) distributed in space and time with periodic boundary conditions that connect the processing steps together and high nonlinearities arising from non-isothermal effects and nonlinear adsorption isotherms. As a result, the optimization of such systems for eithermore » design or operation represents a significant computational challenge to current nonlinear programming algorithms. Model reduction is a powerful methodology that permits systematic generation of cost-efficient low-order representations of large-scale systems that result from discretization of such PDAEs. In particular, low-dimensional approximations can be obtained from reduced order modeling (ROM) techniques based on proper orthogonal decomposition (POD) and can be used as surrogate models in the optimization problems. In this approach, a representative ensemble of solutions of the dynamic PDAE system is constructed by solving a higher-order discretization of the model using the method of lines, followed by the application of Karhunen-Loeve expansion to derive a small set of empirical eigenfunctions (POD modes). These modes are used as basis functions within a Galerkin's projection framework to derive a low-order DAE system that accurately describes the dominant dynamics of the PDAE system. This approach leads to a DAE system of significantly lower order, thus replacing the one obtained from spatial discretization before and making optimization problem computationally efficient [2]. The ROM methodology has been successfully applied to a 2-bed 4-step PSA process used for separating a hydrogen-methane mixture in [3]. The reduced order model developed was successfully used to optimize this process to maximize hydrogen recovery within a trust-region. We extend this approach in this work to develop a rigorous trust-region algorithm for ROM-based optimization of PSA processes. The trust-region update rules and sufficient decrease condition for the objective is used to determine the size of the trust-region. Based on the decrease in the objective function and error in the ROM, a ROM updation strategy is designed [4, 5]. The inequalities and bounds are handled in the algorithm using exact penalty formulation, and a non-smooth trust-region algorithm by Conn et al. [6] is used to handle non-differentiability. To ensure that the first order consistency condition is met and the optimum obtained from ROM-based optimization corresponds to the optimum of the original problem, a scaling function, such as one proposed by Alexandrov et al. [7], is incorporated in the objective function. Such error control mechanism is also capable of handling numerical inconsistencies such as unphysical oscillations in the state variable profiles. The proposed methodology is applied to optimize a PSA process to concentrate CO{sub 2} from a nitrogen-carbon dioxide mixture. As in [3], separate ROMs are developed for each operating step with different POD modes for each state variable. Numerical results will be presented for optimization case studies which involve maximizing CO{sub 2} recovery, feed throughput or minimizing overall power consumption.« less

Generating high-peak-power structured lights in selectively pumped passively Q-switched lasers with astigmatic mode transformations

NASA Astrophysics Data System (ADS)

Chang, C. C.; Hsieh, Y. H.; Lee, C. Y.; Sung, C. L.; Tuan, P. H.; Tung, J. C.; Liang, H. C.; Chen, Y. F.

2017-12-01

Various high-order Hermite-Gaussian (HG) modes with high repetition rates and high peak powers are systematically generated by designing the cavity configuration to satisfy the criterion of the passive Q-switching. For the HG m,0 modes with the order m  =  1-9, the pulse repetition rate can exceed 100 kHz with peak power higher than 0.3 kW. For the HG m,m modes with the order m  =  1-10, the pulse repetition rate can be up to 37 kHz with peak power higher than 0.35 kW. Furthermore, the high-order HG beams is transformed by using an astigmatic mode converter to generate various structured lights with optical vortices. Experimental patterns of the transformed high-order HG beams in the propagation are theoretically analyzed and the phase structures are numerically manifested.

Advances in numerical and applied mathematics

NASA Technical Reports Server (NTRS)

South, J. C., Jr. (Editor); Hussaini, M. Y. (Editor)

1986-01-01

This collection of papers covers some recent developments in numerical analysis and computational fluid dynamics. Some of these studies are of a fundamental nature. They address basic issues such as intermediate boundary conditions for approximate factorization schemes, existence and uniqueness of steady states for time dependent problems, and pitfalls of implicit time stepping. The other studies deal with modern numerical methods such as total variation diminishing schemes, higher order variants of vortex and particle methods, spectral multidomain techniques, and front tracking techniques. There is also a paper on adaptive grids. The fluid dynamics papers treat the classical problems of imcompressible flows in helically coiled pipes, vortex breakdown, and transonic flows.

Numerical method for solving the nonlinear four-point boundary value problems

NASA Astrophysics Data System (ADS)

Lin, Yingzhen; Lin, Jinnan

2010-12-01

In this paper, a new reproducing kernel space is constructed skillfully in order to solve a class of nonlinear four-point boundary value problems. The exact solution of the linear problem can be expressed in the form of series and the approximate solution of the nonlinear problem is given by the iterative formula. Compared with known investigations, the advantages of our method are that the representation of exact solution is obtained in a new reproducing kernel Hilbert space and accuracy of numerical computation is higher. Meanwhile we present the convergent theorem, complexity analysis and error estimation. The performance of the new method is illustrated with several numerical examples.

Combustion research for gas turbine engines

NASA Technical Reports Server (NTRS)

Mularz, E. J.; Claus, R. W.

1985-01-01

Research on combustion is being conducted at Lewis Research Center to provide improved analytical models of the complex flow and chemical reaction processes which occur in the combustor of gas turbine engines and other aeropropulsion systems. The objective of the research is to obtain a better understanding of the various physical processes that occur in the gas turbine combustor in order to develop models and numerical codes which can accurately describe these processes. Activities include in-house research projects, university grants, and industry contracts and are classified under the subject areas of advanced numerics, fuel sprays, fluid mixing, and radiation-chemistry. Results are high-lighted from several projects.

Implementation of Improved Transverse Shear Calculations and Higher Order Laminate Theory Into Strain Rate Dependent Analyses of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Zhu, Lin-Fa; Kim, Soo; Chattopadhyay, Aditi; Goldberg, Robert K.

2004-01-01

A numerical procedure has been developed to investigate the nonlinear and strain rate dependent deformation response of polymer matrix composite laminated plates under high strain rate impact loadings. A recently developed strength of materials based micromechanics model, incorporating a set of nonlinear, strain rate dependent constitutive equations for the polymer matrix, is extended to account for the transverse shear effects during impact. Four different assumptions of transverse shear deformation are investigated in order to improve the developed strain rate dependent micromechanics model. The validities of these assumptions are investigated using numerical and theoretical approaches. A method to determine through the thickness strain and transverse Poisson's ratio of the composite is developed. The revised micromechanics model is then implemented into a higher order laminated plate theory which is modified to include the effects of inelastic strains. Parametric studies are conducted to investigate the mechanical response of composite plates under high strain rate loadings. Results show the transverse shear stresses cannot be neglected in the impact problem. A significant level of strain rate dependency and material nonlinearity is found in the deformation response of representative composite specimens.

Higher-order paraxial theory of the propagation of ring rippled laser beam in plasma: Relativistic ponderomotive regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Purohit, Gunjan, E-mail: gunjan75@gmail.com; Rawat, Priyanka; Chauhan, Prashant

This article presents higher-order paraxial theory (non-paraxial theory) for the ring ripple formation on an intense Gaussian laser beam and its propagation in plasma, taking into account the relativistic-ponderomotive nonlinearity. The intensity dependent dielectric constant of the plasma has been determined for the main laser beam and ring ripple superimposed on the main laser beam. The dielectric constant of the plasma is modified due to the contribution of the electric field vector of ring ripple. Nonlinear differential equations have been formulated to examine the growth of ring ripple in plasma, self focusing of main laser beam, and ring rippled lasermore » beam in plasma using higher-order paraxial theory. These equations have been solved numerically for different laser intensities and plasma frequencies. The well established experimental laser and plasma parameters are used in numerical calculation. It is observed that the focusing of the laser beams (main and ring rippled) becomes fast in the nonparaxial region by expanding the eikonal and other relevant quantities up to the fourth power of r. The splitted profile of laser beam in the plasma is observed due to uneven focusing/defocusing of the axial and off-axial rays. The growths of ring ripple increase when the laser beam intensity increases. Furthermore, the intensity profile of ring rippled laser beam gets modified due to the contribution of growth rate.« less

Alignment of learning objectives and assessments in therapeutics courses to foster higher-order thinking.

PubMed

FitzPatrick, Beverly; Hawboldt, John; Doyle, Daniel; Genge, Terri

2015-02-17

To determine whether national educational outcomes, course objectives, and classroom assessments for 2 therapeutics courses were aligned for curricular content and cognitive processes, and if they included higher-order thinking. Document analysis and student focus groups were used. Outcomes, objectives, and assessment tasks were matched for specific therapeutics content and cognitive processes. Anderson and Krathwohl's Taxonomy was used to define higher-order thinking. Students discussed whether assessments tested objectives and described their thinking when responding to assessments. There were 7 outcomes, 31 objectives, and 412 assessment tasks. The alignment for content and cognitive processes was not satisfactory. Twelve students participated in the focus groups. Students thought more short-answer questions than multiple choice questions matched the objectives for content and required higher-order thinking. The alignment analysis provided data that could be used to reveal and strengthen the enacted curriculum and improve student learning.

The time course of symbolic number adaptation: oscillatory EEG activity and event-related potential analysis.

PubMed

Hsu, Yi-Fang; Szűcs, Dénes

2012-02-15

Several functional magnetic resonance imaging (fMRI) studies have used neural adaptation paradigms to detect anatomical locations of brain activity related to number processing. However, currently not much is known about the temporal structure of number adaptation. In the present study, we used electroencephalography (EEG) to elucidate the time course of neural events in symbolic number adaptation. The numerical distance of deviants relative to standards was manipulated. In order to avoid perceptual confounds, all levels of deviants consisted of perceptually identical stimuli. Multiple successive numerical distance effects were detected in event-related potentials (ERPs). Analysis of oscillatory activity further showed at least two distinct stages of neural processes involved in the automatic analysis of numerical magnitude, with the earlier effect emerging at around 200ms and the later effect appearing at around 400ms. The findings support for the hypothesis that numerical magnitude processing involves a succession of cognitive events. Crown Copyright © 2011. Published by Elsevier Inc. All rights reserved.

Longitudinal Brain Development of Numerical Skills in Typically Developing Children and Children with Developmental Dyscalculia.

PubMed

McCaskey, Ursina; von Aster, Michael; Maurer, Urs; Martin, Ernst; O'Gorman Tuura, Ruth; Kucian, Karin

2017-01-01

Developmental dyscalculia (DD) is a learning disability affecting the acquisition of numerical-arithmetical skills. Studies report persistent deficits in number processing and aberrant functional activation of the fronto-parietal numerical network in DD. However, the neural development of numerical abilities has been scarcely investigated. The present paper provides a first attempt to investigate behavioral and neural trajectories of numerical abilities longitudinally in typically developing (TD) and DD children. During a study period of 4 years, 28 children (8-11 years) were evaluated twice by means of neuropsychological tests and a numerical order fMRI paradigm. Over time, TD children improved in numerical abilities and showed a consistent and well-developed fronto-parietal network. In contrast, DD children revealed persistent deficits in number processing and arithmetic. Brain imaging results of the DD group showed an age-related activation increase in parietal regions (intraparietal sulcus), pointing to a delayed development of number processing areas. Besides, an activation increase in frontal areas was observed over time, indicating the use of compensatory mechanisms. In conclusion, results suggest a continuation in neural development of number representation in DD, whereas the neural network for simple ordinal number estimation seems to be stable or show only subtle changes in TD children over time.

Longitudinal Brain Development of Numerical Skills in Typically Developing Children and Children with Developmental Dyscalculia

PubMed Central

McCaskey, Ursina; von Aster, Michael; Maurer, Urs; Martin, Ernst; O'Gorman Tuura, Ruth; Kucian, Karin

2018-01-01

Developmental dyscalculia (DD) is a learning disability affecting the acquisition of numerical-arithmetical skills. Studies report persistent deficits in number processing and aberrant functional activation of the fronto-parietal numerical network in DD. However, the neural development of numerical abilities has been scarcely investigated. The present paper provides a first attempt to investigate behavioral and neural trajectories of numerical abilities longitudinally in typically developing (TD) and DD children. During a study period of 4 years, 28 children (8–11 years) were evaluated twice by means of neuropsychological tests and a numerical order fMRI paradigm. Over time, TD children improved in numerical abilities and showed a consistent and well-developed fronto-parietal network. In contrast, DD children revealed persistent deficits in number processing and arithmetic. Brain imaging results of the DD group showed an age-related activation increase in parietal regions (intraparietal sulcus), pointing to a delayed development of number processing areas. Besides, an activation increase in frontal areas was observed over time, indicating the use of compensatory mechanisms. In conclusion, results suggest a continuation in neural development of number representation in DD, whereas the neural network for simple ordinal number estimation seems to be stable or show only subtle changes in TD children over time. PMID:29354041

Free vibration analysis of single-walled boron nitride nanotubes based on a computational mechanics framework

NASA Astrophysics Data System (ADS)

Yan, J. W.; Tong, L. H.; Xiang, Ping

2017-12-01

Free vibration behaviors of single-walled boron nitride nanotubes are investigated using a computational mechanics approach. Tersoff-Brenner potential is used to reflect atomic interaction between boron and nitrogen atoms. The higher-order Cauchy-Born rule is employed to establish the constitutive relationship for single-walled boron nitride nanotubes on the basis of higher-order gradient continuum theory. It bridges the gaps between the nanoscale lattice structures with a continuum body. A mesh-free modeling framework is constructed, using the moving Kriging interpolation which automatically satisfies the higher-order continuity, to implement numerical simulation in order to match the higher-order constitutive model. In comparison with conventional atomistic simulation methods, the established atomistic-continuum multi-scale approach possesses advantages in tackling atomic structures with high-accuracy and high-efficiency. Free vibration characteristics of single-walled boron nitride nanotubes with different boundary conditions, tube chiralities, lengths and radii are examined in case studies. In this research, it is pointed out that a critical radius exists for the evaluation of fundamental vibration frequencies of boron nitride nanotubes; opposite trends can be observed prior to and beyond the critical radius. Simulation results are presented and discussed.

An Efficient Finite Element Framework to Assess Flexibility Performances of SMA Self-Expandable Carotid Artery Stents

PubMed Central

Ferraro, Mauro; Auricchio, Ferdinando; Boatti, Elisa; Scalet, Giulia; Conti, Michele; Morganti, Simone; Reali, Alessandro

2015-01-01

Computer-based simulations are nowadays widely exploited for the prediction of the mechanical behavior of different biomedical devices. In this aspect, structural finite element analyses (FEA) are currently the preferred computational tool to evaluate the stent response under bending. This work aims at developing a computational framework based on linear and higher order FEA to evaluate the flexibility of self-expandable carotid artery stents. In particular, numerical simulations involving large deformations and inelastic shape memory alloy constitutive modeling are performed, and the results suggest that the employment of higher order FEA allows accurately representing the computational domain and getting a better approximation of the solution with a widely-reduced number of degrees of freedom with respect to linear FEA. Moreover, when buckling phenomena occur, higher order FEA presents a superior capability of reproducing the nonlinear local effects related to buckling phenomena. PMID:26184329

Novel asymmetric representation method for solving the higher-order Ginzburg-Landau equation

PubMed Central

Wong, Pring; Pang, Lihui; Wu, Ye; Lei, Ming; Liu, Wenjun

2016-01-01

In ultrafast optics, optical pulses are generated to be of shorter pulse duration, which has enormous significance to industrial applications and scientific research. The ultrashort pulse evolution in fiber lasers can be described by the higher-order Ginzburg-Landau (GL) equation. However, analytic soliton solutions for this equation have not been obtained by use of existing methods. In this paper, a novel method is proposed to deal with this equation. The analytic soliton solution is obtained for the first time, and is proved to be stable against amplitude perturbations. Through the split-step Fourier method, the bright soliton solution is studied numerically. The analytic results here may extend the integrable methods, and could be used to study soliton dynamics for some equations in other disciplines. It may also provide the other way to obtain two-soliton solutions for higher-order GL equations. PMID:27086841

Double hard scattering without double counting

NASA Astrophysics Data System (ADS)

Diehl, Markus; Gaunt, Jonathan R.; Schönwald, Kay

2017-06-01

Double parton scattering in proton-proton collisions includes kinematic regions in which two partons inside a proton originate from the perturbative splitting of a single parton. This leads to a double counting problem between single and double hard scattering. We present a solution to this problem, which allows for the definition of double parton distributions as operator matrix elements in a proton, and which can be used at higher orders in perturbation theory. We show how the evaluation of double hard scattering in this framework can provide a rough estimate for the size of the higher-order contributions to single hard scattering that are affected by double counting. In a numeric study, we identify situations in which these higher-order contributions must be explicitly calculated and included if one wants to attain an accuracy at which double hard scattering becomes relevant, and other situations where such contributions may be neglected.

Pendulum Phenomena and the Assessment of Scientific Inquiry Capabilities

ERIC Educational Resources Information Center

Zachos, Paul

2004-01-01

Phenomena associated with the "pendulum" present numerous opportunities for assessing higher order human capabilities related to "scientific inquiry" and the "discovery" of natural law. This paper illustrates how systematic "assessment of scientific inquiry capabilities", using "pendulum" phenomena, can provide a useful tool for classroom teachers…

SIMULATION OF DISPERSION OF A POWER PLANT PLUME USING AN ADAPTIVE GRID ALGORITHM

EPA Science Inventory

A new dynamic adaptive grid algorithm has been developed for use in air quality modeling. This algorithm uses a higher order numerical scheme?the piecewise parabolic method (PPM)?for computing advective solution fields; a weight function capable of promoting grid node clustering ...

Hydrodynamic regime determines the feeding success of larval fish through the modulation of strike kinematics

PubMed Central

China, Victor; Levy, Liraz; Elmaliach, Tal

2017-01-01

Larval fishes experience extreme mortality rates, with 99% of a cohort perishing within days after starting to actively feed. While recent evidence suggests that hydrodynamic factors contribute to constraining larval feeding during early ontogeny, feeding is a complex process that involves numerous interacting behavioural and biomechanical components. How these components change throughout ontogeny and how they contribute to feeding remain unclear. Using 339 observations of larval feeding attempts, we quantified the effects of morphological and behavioural traits on feeding success of Sparus aurata larvae during early ontogeny. Feeding success was determined using high-speed videography, under both natural and increased water viscosity treatments. Successful strikes were characterized by Reynolds numbers that were an order of magnitude higher than those of failed strikes. The pattern of increasing strike success with increasing age was driven by the ontogeny of traits that facilitate the transition to higher Reynolds numbers. Hence, the physical growth of a larva plays an important role in its transition to a hydrodynamic regime of higher Reynolds numbers, in which suction feeding is more effective. PMID:28446697

Hydrodynamic regime determines the feeding success of larval fish through the modulation of strike kinematics.

PubMed

China, Victor; Levy, Liraz; Liberzon, Alex; Elmaliach, Tal; Holzman, Roi

2017-04-26

Larval fishes experience extreme mortality rates, with 99% of a cohort perishing within days after starting to actively feed. While recent evidence suggests that hydrodynamic factors contribute to constraining larval feeding during early ontogeny, feeding is a complex process that involves numerous interacting behavioural and biomechanical components. How these components change throughout ontogeny and how they contribute to feeding remain unclear. Using 339 observations of larval feeding attempts, we quantified the effects of morphological and behavioural traits on feeding success of Sparus aurata larvae during early ontogeny. Feeding success was determined using high-speed videography, under both natural and increased water viscosity treatments. Successful strikes were characterized by Reynolds numbers that were an order of magnitude higher than those of failed strikes. The pattern of increasing strike success with increasing age was driven by the ontogeny of traits that facilitate the transition to higher Reynolds numbers. Hence, the physical growth of a larva plays an important role in its transition to a hydrodynamic regime of higher Reynolds numbers, in which suction feeding is more effective. © 2017 The Author(s).

Extended bounds limiter for high-order finite-volume schemes on unstructured meshes

NASA Astrophysics Data System (ADS)

Tsoutsanis, Panagiotis

2018-06-01

This paper explores the impact of the definition of the bounds of the limiter proposed by Michalak and Ollivier-Gooch in [56] (2009), for higher-order Monotone-Upstream Central Scheme for Conservation Laws (MUSCL) numerical schemes on unstructured meshes in the finite-volume (FV) framework. A new modification of the limiter is proposed where the bounds are redefined by utilising all the spatial information provided by all the elements in the reconstruction stencil. Numerical results obtained on smooth and discontinuous test problems of the Euler equations on unstructured meshes, highlight that the newly proposed extended bounds limiter exhibits superior performance in terms of accuracy and mesh sensitivity compared to the cell-based or vertex-based bounds implementations.

Free-carrier-induced soliton fission unveiled by in situ measurements in nanophotonic waveguides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Husko, Chad; Wulf, Matthias; Lefrancois, Simon

Solitons are localized waves formed by a balance of focusing and defocusing effects. These nonlinear waves exist in diverse forms of matter yet exhibit similar properties including stability, periodic recurrence and particle-like trajectories. One important property is soliton fission, a process by which an energetic higher-order soliton breaks apart due to dispersive or nonlinear perturbations. Here we demonstrate through both experiment and theory that nonlinear photocarrier generation can induce soliton fission. Using near-field measurements, we directly observe the nonlinear spatial and temporal evolution of optical pulses in situ in a nanophotonic semiconductor waveguide. We develop an analytic formalism describing themore » free-carrier dispersion (FCD) perturbation and show the experiment exceeds the minimum threshold by an order of magnitude. We confirm these observations with a numerical nonlinear Schrodinger equation model. Finally, these results provide a fundamental explanation and physical scaling of optical pulse evolution in free-carrier media and could enable improved supercontinuum sources in gas based and integrated semiconductor waveguides.« less

Free-carrier-induced soliton fission unveiled by in situ measurements in nanophotonic waveguides

DOE PAGES

Husko, Chad; Wulf, Matthias; Lefrancois, Simon; ...

2016-04-15

Solitons are localized waves formed by a balance of focusing and defocusing effects. These nonlinear waves exist in diverse forms of matter yet exhibit similar properties including stability, periodic recurrence and particle-like trajectories. One important property is soliton fission, a process by which an energetic higher-order soliton breaks apart due to dispersive or nonlinear perturbations. Here we demonstrate through both experiment and theory that nonlinear photocarrier generation can induce soliton fission. Using near-field measurements, we directly observe the nonlinear spatial and temporal evolution of optical pulses in situ in a nanophotonic semiconductor waveguide. We develop an analytic formalism describing themore » free-carrier dispersion (FCD) perturbation and show the experiment exceeds the minimum threshold by an order of magnitude. We confirm these observations with a numerical nonlinear Schrodinger equation model. Finally, these results provide a fundamental explanation and physical scaling of optical pulse evolution in free-carrier media and could enable improved supercontinuum sources in gas based and integrated semiconductor waveguides.« less

Impedance Eduction in Large Ducts Containing Higher-Order Modes and Grazing Flow

NASA Technical Reports Server (NTRS)

Watson, Willie R.; Jones, Michael G.

2017-01-01

Impedance eduction test data are acquired in ducts with small and large cross-sectional areas at the NASA Langley Research Center. An improved data acquisition system in the large duct has resulted in increased control of the acoustic energy in source modes and more accurate resolution of higher-order duct modes compared to previous tests. Two impedance eduction methods that take advantage of the improved data acquisition to educe the liner impedance in grazing flow are presented. One method measures the axial propagation constant of a dominant mode in the liner test section (by implementing the Kumarsean and Tufts algorithm) and educes the impedance from an exact analytical expression. The second method solves numerically the convected Helmholtz equation and minimizes an objective function to obtain the liner impedance. The two methods are tested first on data synthesized from an exact mode solution and then on measured data. Results show that when the methods are applied to data acquired in the larger duct with a dominant higher-order mode, the same impedance spectra are educed as that obtained in the small duct where only the plane wave mode propagates. This result holds for each higher-order mode in the large duct provided that the higher-order mode is sufficiently attenuated by the liner.

Experimental and Numerical Investigations in Shallow Cut Grinding by Workpiece Integrated Infrared Thermopile Array.

PubMed

Reimers, Marcel; Lang, Walter; Dumstorff, Gerrit

2017-09-30

The purpose of our study is to investigate the heat distribution and the occurring temperatures during grinding. Therefore, we did both experimental and numerical investigations. In the first part, we present the integration of an infrared thermopile array in a steel workpiece. Experiments are done by acquiring data from the thermopile array during grinding of a groove in a workpiece made of steel. In the second part, we present numerical investigations in the grinding process to further understand the thermal characteristic during grinding. Finally, we conclude our work. Increasing the feed speed leads to two things: higher heat flux densities in the workpiece and higher temperature gradients in the material.

Experimental and Numerical Investigations in Shallow Cut Grinding by Workpiece Integrated Infrared Thermopile Array

PubMed Central

Reimers, Marcel; Lang, Walter; Dumstorff, Gerrit

2017-01-01

The purpose of our study is to investigate the heat distribution and the occurring temperatures during grinding. Therefore, we did both experimental and numerical investigations. In the first part, we present the integration of an infrared thermopile array in a steel workpiece. Experiments are done by acquiring data from the thermopile array during grinding of a groove in a workpiece made of steel. In the second part, we present numerical investigations in the grinding process to further understand the thermal characteristic during grinding. Finally, we conclude our work. Increasing the feed speed leads to two things: higher heat flux densities in the workpiece and higher temperature gradients in the material. PMID:28973978

An order insertion scheduling model of logistics service supply chain considering capacity and time factors.

PubMed

Liu, Weihua; Yang, Yi; Wang, Shuqing; Liu, Yang

2014-01-01

Order insertion often occurs in the scheduling process of logistics service supply chain (LSSC), which disturbs normal time scheduling especially in the environment of mass customization logistics service. This study analyses order similarity coefficient and order insertion operation process and then establishes an order insertion scheduling model of LSSC with service capacity and time factors considered. This model aims to minimize the average unit volume operation cost of logistics service integrator and maximize the average satisfaction degree of functional logistics service providers. In order to verify the viability and effectiveness of our model, a specific example is numerically analyzed. Some interesting conclusions are obtained. First, along with the increase of completion time delay coefficient permitted by customers, the possible inserting order volume first increases and then trends to be stable. Second, supply chain performance reaches the best when the volume of inserting order is equal to the surplus volume of the normal operation capacity in mass service process. Third, the larger the normal operation capacity in mass service process is, the bigger the possible inserting order's volume will be. Moreover, compared to increasing the completion time delay coefficient, improving the normal operation capacity of mass service process is more useful.

A {3,2}-Order Bending Theory for Laminated Composite and Sandwich Beams

NASA Technical Reports Server (NTRS)

Cook, Geoffrey M.; Tessler, Alexander

1998-01-01

A higher-order bending theory is derived for laminated composite and sandwich beams thus extending the recent {1,2}-order theory to include third-order axial effect without introducing additional kinematic variables. The present theory is of order {3,2} and includes both transverse shear and transverse normal deformations. A closed-form solution to the cylindrical bending problem is derived and compared with the corresponding exact elasticity solution. The numerical comparisons are focused on the most challenging material systems and beam aspect ratios which include moderate-to-thick unsymmetric composite and sandwich laminates. Advantages and limitations of the theory are discussed.

Numerical Study on Stress Heterogeneity Development in Two-Phase Rocks with Large Rheological Contrast and Implications in the Lower Crust

NASA Astrophysics Data System (ADS)

Xu, Junshan; Zhang, Baohua

2018-03-01

Development of stress heterogeneity in two-phase rocks was investigated via a finite element method at 1000-1200 K and 100 MPa. Two groups of rock models were considered: anorthite-diopside and anorthite-clinopyroxene, with a phase volume ratio of 1:1 in each group and different dislocation creep rates between phases ( 4-8 orders of magnitude). Our numerical results indicate that the stress inside the model can be several times higher than the differential stress applied to the model and stress will tend to concentrate in hard phase, especially near the sharp boundaries with soft phase. Moreover, large stress gradient in hard phase and nearly homogeneous stress in soft phase will lead to the initialization of localized dynamic recrystallization or fracture. These numerical observations suggest that the rheological contrast between two phases plays a crucial role in stress heterogeneity rather than other factors (such as grain size, the boundary conditions or mesh density), which may eventually accelerate development of stress heterogeneity in the lower crust. Our study provides new insights into the dynamic processes of grain size reduction in the lower crust, which may cause the transformation from dislocation creep to diffusion creep and enable the weakened shear zones.

Tuning algorithms for fractional order internal model controllers for time delay processes

NASA Astrophysics Data System (ADS)

Muresan, Cristina I.; Dutta, Abhishek; Dulf, Eva H.; Pinar, Zehra; Maxim, Anca; Ionescu, Clara M.

2016-03-01

This paper presents two tuning algorithms for fractional-order internal model control (IMC) controllers for time delay processes. The two tuning algorithms are based on two specific closed-loop control configurations: the IMC control structure and the Smith predictor structure. In the latter, the equivalency between IMC and Smith predictor control structures is used to tune a fractional-order IMC controller as the primary controller of the Smith predictor structure. Fractional-order IMC controllers are designed in both cases in order to enhance the closed-loop performance and robustness of classical integer order IMC controllers. The tuning procedures are exemplified for both single-input-single-output as well as multivariable processes, described by first-order and second-order transfer functions with time delays. Different numerical examples are provided, including a general multivariable time delay process. Integer order IMC controllers are designed in each case, as well as fractional-order IMC controllers. The simulation results show that the proposed fractional-order IMC controller ensures an increased robustness to modelling uncertainties. Experimental results are also provided, for the design of a multivariable fractional-order IMC controller in a Smith predictor structure for a quadruple-tank system.

Multiple-correction hybrid k-exact schemes for high-order compressible RANS-LES simulations on fully unstructured grids

NASA Astrophysics Data System (ADS)

Pont, Grégoire; Brenner, Pierre; Cinnella, Paola; Maugars, Bruno; Robinet, Jean-Christophe

2017-12-01

A Godunov's type unstructured finite volume method suitable for highly compressible turbulent scale-resolving simulations around complex geometries is constructed by using a successive correction technique. First, a family of k-exact Godunov schemes is developed by recursively correcting the truncation error of the piecewise polynomial representation of the primitive variables. The keystone of the proposed approach is a quasi-Green gradient operator which ensures consistency on general meshes. In addition, a high-order single-point quadrature formula, based on high-order approximations of the successive derivatives of the solution, is developed for flux integration along cell faces. The proposed family of schemes is compact in the algorithmic sense, since it only involves communications between direct neighbors of the mesh cells. The numerical properties of the schemes up to fifth-order are investigated, with focus on their resolvability in terms of number of mesh points required to resolve a given wavelength accurately. Afterwards, in the aim of achieving the best possible trade-off between accuracy, computational cost and robustness in view of industrial flow computations, we focus more specifically on the third-order accurate scheme of the family, and modify locally its numerical flux in order to reduce the amount of numerical dissipation in vortex-dominated regions. This is achieved by switching from the upwind scheme, mostly applied in highly compressible regions, to a fourth-order centered one in vortex-dominated regions. An analytical switch function based on the local grid Reynolds number is adopted in order to warrant numerical stability of the recentering process. Numerical applications demonstrate the accuracy and robustness of the proposed methodology for compressible scale-resolving computations. In particular, supersonic RANS/LES computations of the flow over a cavity are presented to show the capability of the scheme to predict flows with shocks, vortical structures and complex geometries.

Long-term dynamic modeling of tethered spacecraft using nodal position finite element method and symplectic integration

NASA Astrophysics Data System (ADS)

Li, G. Q.; Zhu, Z. H.

2015-12-01

Dynamic modeling of tethered spacecraft with the consideration of elasticity of tether is prone to the numerical instability and error accumulation over long-term numerical integration. This paper addresses the challenges by proposing a globally stable numerical approach with the nodal position finite element method (NPFEM) and the implicit, symplectic, 2-stage and 4th order Gaussian-Legendre Runge-Kutta time integration. The NPFEM eliminates the numerical error accumulation by using the position instead of displacement of tether as the state variable, while the symplectic integration enforces the energy and momentum conservation of the discretized finite element model to ensure the global stability of numerical solution. The effectiveness and robustness of the proposed approach is assessed by an elastic pendulum problem, whose dynamic response resembles that of tethered spacecraft, in comparison with the commonly used time integrators such as the classical 4th order Runge-Kutta schemes and other families of non-symplectic Runge-Kutta schemes. Numerical results show that the proposed approach is accurate and the energy of the corresponding numerical model is conservative over the long-term numerical integration. Finally, the proposed approach is applied to the dynamic modeling of deorbiting process of tethered spacecraft over a long period.

Accurate Estimate of Some Propagation Characteristics for the First Higher Order Mode in Graded Index Fiber with Simple Analytic Chebyshev Method

NASA Astrophysics Data System (ADS)

Dutta, Ivy; Chowdhury, Anirban Roy; Kumbhakar, Dharmadas

2013-03-01

Using Chebyshev power series approach, accurate description for the first higher order (LP11) mode of graded index fibers having three different profile shape functions are presented in this paper and applied to predict their propagation characteristics. These characteristics include fractional power guided through the core, excitation efficiency and Petermann I and II spot sizes with their approximate analytic formulations. We have shown that where two and three Chebyshev points in LP11 mode approximation present fairly accurate results, the values based on our calculations involving four Chebyshev points match excellently with available exact numerical results.

Higher order temporal finite element methods through mixed formalisms.

PubMed

Kim, Jinkyu

2014-01-01

The extended framework of Hamilton's principle and the mixed convolved action principle provide new rigorous weak variational formalism for a broad range of initial boundary value problems in mathematical physics and mechanics. In this paper, their potential when adopting temporally higher order approximations is investigated. The classical single-degree-of-freedom dynamical systems are primarily considered to validate and to investigate the performance of the numerical algorithms developed from both formulations. For the undamped system, all the algorithms are symplectic and unconditionally stable with respect to the time step. For the damped system, they are shown to be accurate with good convergence characteristics.

High surface plasmon resonance sensitivity enabled by optical disks.

PubMed

Dou, Xuan; Phillips, Blayne M; Chung, Pei-Yu; Jiang, Peng

2012-09-01

We report a systematic, experimental, and theoretical investigation on the surface plasmon resonance (SPR) sensing using optical disks with different track pitches, including Blu-ray disk (BD), digital versatile disk (DVD), and compact disk (CD). Optical reflection measurements indicate that CD and DVD exhibit much higher SPR sensitivity than BD. Both experiments and finite-difference time-domain simulations reveal that the SPR sensitivity is significantly affected by the diffraction order of the SPR peaks and higher diffraction order results in lower sensitivity. Numerical simulations also show that very high sensitivity (∼1600  nm per refractive index unit) is achievable by CDs.

Separating stages of arithmetic verification: An ERP study with a novel paradigm.

PubMed

Avancini, Chiara; Soltész, Fruzsina; Szűcs, Dénes

2015-08-01

In studies of arithmetic verification, participants typically encounter two operands and they carry out an operation on these (e.g. adding them). Operands are followed by a proposed answer and participants decide whether this answer is correct or incorrect. However, interpretation of results is difficult because multiple parallel, temporally overlapping numerical and non-numerical processes of the human brain may contribute to task execution. In order to overcome this problem here we used a novel paradigm specifically designed to tease apart the overlapping cognitive processes active during arithmetic verification. Specifically, we aimed to separate effects related to detection of arithmetic correctness, detection of the violation of strategic expectations, detection of physical stimulus properties mismatch and numerical magnitude comparison (numerical distance effects). Arithmetic correctness, physical stimulus properties and magnitude information were not task-relevant properties of the stimuli. We distinguished between a series of temporally highly overlapping cognitive processes which in turn elicited overlapping ERP effects with distinct scalp topographies. We suggest that arithmetic verification relies on two major temporal phases which include parallel running processes. Our paradigm offers a new method for investigating specific arithmetic verification processes in detail. Copyright © 2015 Elsevier Ltd. All rights reserved.

Algorithm for computing descriptive statistics for very large data sets and the exa-scale era

NASA Astrophysics Data System (ADS)

Beekman, Izaak

2017-11-01

An algorithm for Single-point, Parallel, Online, Converging Statistics (SPOCS) is presented. It is suited for in situ analysis that traditionally would be relegated to post-processing, and can be used to monitor the statistical convergence and estimate the error/residual in the quantity-useful for uncertainty quantification too. Today, data may be generated at an overwhelming rate by numerical simulations and proliferating sensing apparatuses in experiments and engineering applications. Monitoring descriptive statistics in real time lets costly computations and experiments be gracefully aborted if an error has occurred, and monitoring the level of statistical convergence allows them to be run for the shortest amount of time required to obtain good results. This algorithm extends work by Pébay (Sandia Report SAND2008-6212). Pébay's algorithms are recast into a converging delta formulation, with provably favorable properties. The mean, variance, covariances and arbitrary higher order statistical moments are computed in one pass. The algorithm is tested using Sillero, Jiménez, & Moser's (2013, 2014) publicly available UPM high Reynolds number turbulent boundary layer data set, demonstrating numerical robustness, efficiency and other favorable properties.

Suzuki-Trotter Formula for Real-Time Dependent LDA I: Electron Dynamics

NASA Astrophysics Data System (ADS)

Sugino, Osamu; Miyamoto, Yoshiyuki

1998-03-01

To investigate various physical and chemical processes where electron dynamics play a role (e.g. collisions or photochemical reactions), solving the real-time Schrödinger equation is essentially important. ihbar fracpartialφpartial t=H φ Trial of solving eqn. (1) from first principles has begun very recently(K. Yabana and G. F. Bertch, Phys. Rev. B54) 4484 (1996)., and it is now in the stage of establishing efficient, stable, and accurate method for numerical calculation. In this talk, we present several improvements in the method of solving eqn. (1) within the density functional theory: (A) higher order Suzuki-Trotter formula(M. Suzuki, Phys. Lett. A146) 319 (1990). to integrate eqn. (1) keeping the orthonormality of the wavefunctions, (B) special interpolation scheme for the self-consistent potential to reduce the drift in the total-energy, and (C) the preconditioning techniques to increase the time step for the simulation. We will demonstrate numerical stability and efficiency using several cluster calculations, and will address the accuracy by comparing the computed cross sections for atom-electron collisions with experiment.

Effect of Numerical Error on Gravity Field Estimation for GRACE and Future Gravity Missions

NASA Astrophysics Data System (ADS)

McCullough, Christopher; Bettadpur, Srinivas

2015-04-01

In recent decades, gravity field determination from low Earth orbiting satellites, such as the Gravity Recovery and Climate Experiment (GRACE), has become increasingly more effective due to the incorporation of high accuracy measurement devices. Since instrumentation quality will only increase in the near future and the gravity field determination process is computationally and numerically intensive, numerical error from the use of double precision arithmetic will eventually become a prominent error source. While using double-extended or quadruple precision arithmetic will reduce these errors, the numerical limitations of current orbit determination algorithms and processes must be accurately identified and quantified in order to adequately inform the science data processing techniques of future gravity missions. The most obvious numerical limitation in the orbit determination process is evident in the comparison of measured observables with computed values, derived from mathematical models relating the satellites' numerically integrated state to the observable. Significant error in the computed trajectory will corrupt this comparison and induce error in the least squares solution of the gravitational field. In addition, errors in the numerically computed trajectory propagate into the evaluation of the mathematical measurement model's partial derivatives. These errors amalgamate in turn with numerical error from the computation of the state transition matrix, computed using the variational equations of motion, in the least squares mapping matrix. Finally, the solution of the linearized least squares system, computed using a QR factorization, is also susceptible to numerical error. Certain interesting combinations of each of these numerical errors are examined in the framework of GRACE gravity field determination to analyze and quantify their effects on gravity field recovery.

Assessing Higher-Order Cognitive Constructs by Using an Information-Processing Framework

ERIC Educational Resources Information Center

Dickison, Philip; Luo, Xiao; Kim, Doyoung; Woo, Ada; Muntean, William; Bergstrom, Betty

2016-01-01

Designing a theory-based assessment with sound psychometric qualities to measure a higher-order cognitive construct is a highly desired yet challenging task for many practitioners. This paper proposes a framework for designing a theory-based assessment to measure a higher-order cognitive construct. This framework results in a modularized yet…

Geometrically nonlinear resonance of higher-order shear deformable functionally graded carbon-nanotube-reinforced composite annular sector plates excited by harmonic transverse loading

NASA Astrophysics Data System (ADS)

Gholami, Raheb; Ansari, Reza

2018-02-01

This article presents an attempt to study the nonlinear resonance of functionally graded carbon-nanotube-reinforced composite (FG-CNTRC) annular sector plates excited by a uniformly distributed harmonic transverse load. To this purpose, first, the extended rule of mixture including the efficiency parameters is employed to approximately obtain the effective material properties of FG-CNTRC annular sector plates. Then, the focus is on presenting the weak form of discretized mathematical formulation of governing equations based on the variational differential quadrature (VDQ) method and Hamilton's principle. The geometric nonlinearity and shear deformation effects are considered based on the von Kármán assumptions and Reddy's third-order shear deformation plate theory, respectively. The discretization process is performed via the generalized differential quadrature (GDQ) method together with numerical differential and integral operators. Then, an efficient multi-step numerical scheme is used to obtain the nonlinear dynamic behavior of the FG-CNTRC annular sector plates near their primary resonance as the frequency-response curve. The accuracy of the present results is first verified and then a parametric study is presented to show the impacts of CNT volume fraction, CNT distribution pattern, geometry of annular sector plate and sector angle on the nonlinear frequency-response curve of FG-CNTRC annular sector plates with different edge supports.

Development of cognitive processing and judgments of knowledge in medical students: Analysis of progress test results.

PubMed

Cecilio-Fernandes, Dario; Kerdijk, Wouter; Jaarsma, A D Debbie C; Tio, René A

2016-11-01

Beside acquiring knowledge, medical students should also develop the ability to apply and reflect on it, requiring higher-order cognitive processing. Ideally, students should have reached higher-order cognitive processing when they enter the clinical program. Whether this is the case, is unknown. We investigated students' cognitive processing, and awareness of their knowledge during medical school. Data were gathered from 347 first-year preclinical and 196 first-year clinical students concerning the 2008 and 2011 Dutch progress tests. Questions were classified based upon Bloom's taxonomy: "simple questions" requiring lower and "vignette questions" requiring higher-order cognitive processing. Subsequently, we compared students' performance and awareness of their knowledge in 2008 to that in 2011 for each question type. Students' performance on each type of question increased as students progressed. Preclinical and first-year clinical students performed better on simple questions than on vignette questions. Third-year clinical students performed better on vignette questions than on simple questions. The accuracy of students' judgment of knowledge decreased over time. The progress test is a useful tool to assess students' cognitive processing and awareness of their knowledge. At the end of medical school, students achieved higher-order cognitive processing but their awareness of their knowledge had decreased.

Multigrid direct numerical simulation of the whole process of flow transition in 3-D boundary layers

NASA Technical Reports Server (NTRS)

Liu, Chaoqun; Liu, Zhining

1993-01-01

A new technology was developed in this study which provides a successful numerical simulation of the whole process of flow transition in 3-D boundary layers, including linear growth, secondary instability, breakdown, and transition at relatively low CPU cost. Most other spatial numerical simulations require high CPU cost and blow up at the stage of flow breakdown. A fourth-order finite difference scheme on stretched and staggered grids, a fully implicit time marching technique, a semi-coarsening multigrid based on the so-called approximate line-box relaxation, and a buffer domain for the outflow boundary conditions were all used for high-order accuracy, good stability, and fast convergence. A new fine-coarse-fine grid mapping technique was developed to keep the code running after the laminar flow breaks down. The computational results are in good agreement with linear stability theory, secondary instability theory, and some experiments. The cost for a typical case with 162 x 34 x 34 grid is around 2 CRAY-YMP CPU hours for 10 T-S periods.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zou, Ling; Zhao, Haihua; Kim, Seung Jun

In this study, the classical Welander’s oscillatory natural circulation problem is investigated using high-order numerical methods. As originally studied by Welander, the fluid motion in a differentially heated fluid loop can exhibit stable, weakly instable, and strongly instable modes. A theoretical stability map has also been originally derived from the stability analysis. Numerical results obtained in this paper show very good agreement with Welander’s theoretical derivations. For stable cases, numerical results from both the high-order and low-order numerical methods agree well with the non-dimensional flow rate analytically derived. The high-order numerical methods give much less numerical errors compared to themore » low-order methods. For stability analysis, the high-order numerical methods could perfectly predict the stability map, while the low-order numerical methods failed to do so. For all theoretically unstable cases, the low-order methods predicted them to be stable. The result obtained in this paper is a strong evidence to show the benefits of using high-order numerical methods over the low-order ones, when they are applied to simulate natural circulation phenomenon that has already gain increasing interests in many future nuclear reactor designs.« less

Three-dimensional transient numerical simulation for intake process in the engine intake port-valve-cylinder system.

PubMed

Luo, Ma-Ji; Chen, Guo-Hua; Ma, Yuan-Hao

2003-01-01

This paper presents a KIVA-3 code based numerical model for three-dimensional transient intake flow in the intake port-valve-cylinder system of internal combustion engine using body-fitted technique, which can be used in numerical study on internal combustion engine with vertical and inclined valves, and has higher calculation precision. A numerical simulation (on the intake process of a two-valve engine with a semi-sphere combustion chamber and a radial intake port) is provided for analysis of the velocity field and pressure field of different plane at different crank angles. The results revealed the formation of the tumble motion, the evolution of flow field parameters and the variation of tumble ratios as important information for the design of engine intake system.

SIMULATION OF DISPERSION OF A POWER PLANT PLUME USING AN ADAPTIVE GRID ALGORITHM. (R827028)

EPA Science Inventory

A new dynamic adaptive grid algorithm has been developed for use in air quality modeling. This algorithm uses a higher order numerical scheme––the piecewise parabolic method (PPM)––for computing advective solution fields; a weight function capable o...

The Functions and Dysfunctions of College Rankings: An Analysis of Institutional Expenditure

ERIC Educational Resources Information Center

Kim, Jeongeun

2018-01-01

College rankings have become a powerful influence in higher education. While the determinants of educational quality are not clearly defined, college rankings designate an institution's standing in a numerical order based on quantifiable measurements that focus primarily on institutional resources. Previous research has identified the…

Hyperfast Numerical Integration of Ocean Surface Wave Dynamics Extensions to Higher Order

DTIC Science & Technology

2008-09-30

Osborne Dipartimento di Fisica Generale, Università di Torino Via Pietro Giuria 1 10125 Torino, Italy Phone: (+39) 11-670-7451 or (+39) 11-329...Universit?i Torino,Dipartimento di Fisica Generale,Via Pietro Giuria 1,10125 Torino, Italy, , 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING

Analysis of warping deformation modes using higher order ANCF beam element

NASA Astrophysics Data System (ADS)

Orzechowski, Grzegorz; Shabana, Ahmed A.

2016-02-01

Most classical beam theories assume that the beam cross section remains a rigid surface under an arbitrary loading condition. However, in the absolute nodal coordinate formulation (ANCF) continuum-based beams, this assumption can be relaxed allowing for capturing deformation modes that couple the cross-section deformation and beam bending, torsion, and/or elongation. The deformation modes captured by ANCF finite elements depend on the interpolating polynomials used. The most widely used spatial ANCF beam element employs linear approximation in the transverse direction, thereby restricting the cross section deformation and leading to locking problems. The objective of this investigation is to examine the behavior of a higher order ANCF beam element that includes quadratic interpolation in the transverse directions. This higher order element allows capturing warping and non-uniform stretching distribution. Furthermore, this higher order element allows for increasing the degree of continuity at the element interface. It is shown in this paper that the higher order ANCF beam element can be used effectively to capture warping and eliminate Poisson locking that characterizes lower order ANCF finite elements. It is also shown that increasing the degree of continuity requires a special attention in order to have acceptable results. Because higher order elements can be more computationally expensive than the lower order elements, the use of reduced integration for evaluating the stress forces and the use of explicit and implicit numerical integrations to solve the nonlinear dynamic equations of motion are investigated in this paper. It is shown that the use of some of these integration methods can be very effective in reducing the CPU time without adversely affecting the solution accuracy.

Vector spherical quasi-Gaussian vortex beams

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2014-02-01

Model equations for describing and efficiently computing the radiation profiles of tightly spherically focused higher-order electromagnetic beams of vortex nature are derived stemming from a vectorial analysis with the complex-source-point method. This solution, termed as a high-order quasi-Gaussian (qG) vortex beam, exactly satisfies the vector Helmholtz and Maxwell's equations. It is characterized by a nonzero integer degree and order (n,m), respectively, an arbitrary waist w0, a diffraction convergence length known as the Rayleigh range zR, and an azimuthal phase dependency in the form of a complex exponential corresponding to a vortex beam. An attractive feature of the high-order solution is the rigorous description of strongly focused (or strongly divergent) vortex wave fields without the need of either the higher-order corrections or the numerically intensive methods. Closed-form expressions and computational results illustrate the analysis and some properties of the high-order qG vortex beams based on the axial and transverse polarization schemes of the vector potentials with emphasis on the beam waist.

Algorithms for the Fractional Calculus: A Selection of Numerical Methods

NASA Technical Reports Server (NTRS)

Diethelm, K.; Ford, N. J.; Freed, A. D.; Luchko, Yu.

2003-01-01

Many recently developed models in areas like viscoelasticity, electrochemistry, diffusion processes, etc. are formulated in terms of derivatives (and integrals) of fractional (non-integer) order. In this paper we present a collection of numerical algorithms for the solution of the various problems arising in this context. We believe that this will give the engineer the necessary tools required to work with fractional models in an efficient way.

Effects of reservoir heterogeneity on scaling of effective mass transfer coefficient for solute transport

NASA Astrophysics Data System (ADS)

Leung, Juliana Y.; Srinivasan, Sanjay

2016-09-01

Modeling transport process at large scale requires proper scale-up of subsurface heterogeneity and an understanding of its interaction with the underlying transport mechanisms. A technique based on volume averaging is applied to quantitatively assess the scaling characteristics of effective mass transfer coefficient in heterogeneous reservoir models. The effective mass transfer coefficient represents the combined contribution from diffusion and dispersion to the transport of non-reactive solute particles within a fluid phase. Although treatment of transport problems with the volume averaging technique has been published in the past, application to geological systems exhibiting realistic spatial variability remains a challenge. Previously, the authors developed a new procedure where results from a fine-scale numerical flow simulation reflecting the full physics of the transport process albeit over a sub-volume of the reservoir are integrated with the volume averaging technique to provide effective description of transport properties. The procedure is extended such that spatial averaging is performed at the local-heterogeneity scale. In this paper, the transport of a passive (non-reactive) solute is simulated on multiple reservoir models exhibiting different patterns of heterogeneities, and the scaling behavior of effective mass transfer coefficient (Keff) is examined and compared. One such set of models exhibit power-law (fractal) characteristics, and the variability of dispersion and Keff with scale is in good agreement with analytical expressions described in the literature. This work offers an insight into the impacts of heterogeneity on the scaling of effective transport parameters. A key finding is that spatial heterogeneity models with similar univariate and bivariate statistics may exhibit different scaling characteristics because of the influence of higher order statistics. More mixing is observed in the channelized models with higher-order continuity. It reinforces the notion that the flow response is influenced by the higher-order statistical description of heterogeneity. An important implication is that when scaling-up transport response from lab-scale results to the field scale, it is necessary to account for the scale-up of heterogeneity. Since the characteristics of higher-order multivariate distributions and large-scale heterogeneity are typically not captured in small-scale experiments, a reservoir modeling framework that captures the uncertainty in heterogeneity description should be adopted.

Numerical modeling of Czochralski growth of Li2MoO4 crystals for heat-scintillation cryogenic bolometers

NASA Astrophysics Data System (ADS)

Stelian, Carmen; Velázquez, Matias; Veber, Philippe; Ahmine, Abdelmounaim; Sand, Jean-Baptiste; Buşe, Gabriel; Cabane, Hugues; Duffar, Thierry

2018-06-01

Lithium molybdate Li2MoO4 (LMO) crystals of mass ranging between 350 and 500 g are excellent candidates to build heat-scintillation cryogenic bolometers likely to be used for the detection of rare events in astroparticle physics. In this work, numerical modeling is applied in order to investigate the Czochralski growth of Li2MoO4 crystals in an inductive furnace. The numerical model was validated by comparing the numerical predictions of the crystal-melt interface shape to experimental visualization of the growth interface. Modeling was performed for two different Czochralski furnaces that use inductive heating. The simulation of the first furnace, which was used to grow Li2MoO4 crystals of 3-4 cm in diameter, reveals non-optimal heat transfer conditions for obtaining good quality crystals. The second furnace, which will be used to grow crystals of 5 cm in diameter, was numerically optimized in order to reduce the temperature gradients in the crystal and to avoid fast crystallization of the bath at the later stages of the growth process.

Thermal Conductivity of a Nanoscale Yttrium Iron Garnet Thin-Film Prepared by the Sol-Gel Process

PubMed Central

2017-01-01

The thermal conductivity of a nanoscale yttrium iron garnet (Y3Fe5O12, YIG) thin-film prepared by a sol-gel method was evaluated using the ultrafast pump-probe technique in the present study. The thermoreflectance change on the surface of a 250 nm thick YIG film, induced by the irradiation of femtosecond laser pulses, was measured, and curve fitting of a numerical solution for the transient heat conduction equation to the experimental data was performed using the finite difference method in order to extract the thermal property. Results show that the film’s thermal conductivity is 22–83% higher than the properties of bulk YIG materials prepared by different fabrication techniques, reflecting the microstructural characteristics and quality of the film. PMID:28858249

Averaging Principle for the Higher Order Nonlinear Schrödinger Equation with a Random Fast Oscillation

NASA Astrophysics Data System (ADS)

Gao, Peng

2018-06-01

This work concerns the problem associated with averaging principle for a higher order nonlinear Schrödinger equation perturbed by a oscillating term arising as the solution of a stochastic reaction-diffusion equation evolving with respect to the fast time. This model can be translated into a multiscale stochastic partial differential equations. Stochastic averaging principle is a powerful tool for studying qualitative analysis of stochastic dynamical systems with different time-scales. To be more precise, under suitable conditions, we prove that there is a limit process in which the fast varying process is averaged out and the limit process which takes the form of the higher order nonlinear Schrödinger equation is an average with respect to the stationary measure of the fast varying process. Finally, by using the Khasminskii technique we can obtain the rate of strong convergence for the slow component towards the solution of the averaged equation, and as a consequence, the system can be reduced to a single higher order nonlinear Schrödinger equation with a modified coefficient.

Averaging Principle for the Higher Order Nonlinear Schrödinger Equation with a Random Fast Oscillation

NASA Astrophysics Data System (ADS)

Gao, Peng

2018-04-01

This work concerns the problem associated with averaging principle for a higher order nonlinear Schrödinger equation perturbed by a oscillating term arising as the solution of a stochastic reaction-diffusion equation evolving with respect to the fast time. This model can be translated into a multiscale stochastic partial differential equations. Stochastic averaging principle is a powerful tool for studying qualitative analysis of stochastic dynamical systems with different time-scales. To be more precise, under suitable conditions, we prove that there is a limit process in which the fast varying process is averaged out and the limit process which takes the form of the higher order nonlinear Schrödinger equation is an average with respect to the stationary measure of the fast varying process. Finally, by using the Khasminskii technique we can obtain the rate of strong convergence for the slow component towards the solution of the averaged equation, and as a consequence, the system can be reduced to a single higher order nonlinear Schrödinger equation with a modified coefficient.

Buckling analysis of SMA bonded sandwich structure – using FEM

NASA Astrophysics Data System (ADS)

Katariya, Pankaj V.; Das, Arijit; Panda, Subrata K.

2018-03-01

Thermal buckling strength of smart sandwich composite structure (bonded with shape memory alloy; SMA) examined numerically via a higher-order finite element model in association with marching technique. The excess geometrical distortion of the structure under the elevated environment modeled through Green’s strain function whereas the material nonlinearity counted with the help of marching method. The system responses are computed numerically by solving the generalized eigenvalue equations via a customized MATLAB code. The comprehensive behaviour of the current finite element solutions (minimum buckling load parameter) is established by solving the adequate number of numerical examples including the given input parameter. The current numerical model is extended further to check the influence of various structural parameter of the sandwich panel on the buckling temperature including the SMA effect and reported in details.

High-Order Numerical Simulations of Wind Turbine Wakes

NASA Astrophysics Data System (ADS)

Kleusberg, E.; Mikkelsen, R. F.; Schlatter, P.; Ivanell, S.; Henningson, D. S.

2017-05-01

Previous attempts to describe the structure of wind turbine wakes and their mutual interaction were mostly limited to large-eddy and Reynolds-averaged Navier-Stokes simulations using finite-volume solvers. We employ the higher-order spectral-element code Nek5000 to study the influence of numerical aspects on the prediction of the wind turbine wake structure and the wake interaction between two turbines. The spectral-element method enables an accurate representation of the vortical structures, with lower numerical dissipation than the more commonly used finite-volume codes. The wind-turbine blades are modeled as body forces using the actuator-line method (ACL) in the incompressible Navier-Stokes equations. Both tower and nacelle are represented with appropriate body forces. An inflow boundary condition is used which emulates homogeneous isotropic turbulence of wind-tunnel flows. We validate the implementation with results from experimental campaigns undertaken at the Norwegian University of Science and Technology (NTNU Blind Tests), investigate parametric influences and compare computational aspects with existing numerical simulations. In general the results show good agreement between the experiments and the numerical simulations both for a single-turbine setup as well as a two-turbine setup where the turbines are offset in the spanwise direction. A shift in the wake center caused by the tower wake is detected similar to experiments. The additional velocity deficit caused by the tower agrees well with the experimental data. The wake is captured well by Nek5000 in comparison with experiments both for the single wind turbine and in the two-turbine setup. The blade loading however shows large discrepancies for the high-turbulence, two-turbine case. While the experiments predicted higher thrust for the downstream turbine than for the upstream turbine, the opposite case was observed in Nek5000.

Thermal stresses and deflections of cross-ply laminated plates using refined plate theories

NASA Technical Reports Server (NTRS)

Khdeir, A. A.; Reddy, J. N.

1991-01-01

Exact analytical solutions of refined plate theories are developed to study the thermal stresses and deflections of cross-ply rectangular plates. The state-space approach in conjunction with the Levy method is used to solve exactly the governing equations of the theories under various boundary conditions. Numerical results of the higher-order theory of Reddy for thermal stresses and deflections are compared with those obtained using the classical and first-order plate theories.

Sleep inertia, sleep homeostatic, and circadian influences on higher-order cognitive functions

PubMed Central

Ronda, Joseph M.; Czeisler, Charles A.; Wright, Kenneth P.

2016-01-01

Summary Sleep inertia, sleep homeostatic, and circadian processes modulate cognition, including reaction time, memory, mood, and alertness. How these processes influence higher-order cognitive functions is not well known. Six participants completed a 73-daylong study that included two 14-daylong 28h forced desynchrony protocols, to examine separate and interacting influences of sleep inertia, sleep homeostasis, and circadian phase on higher-order cognitive functions of inhibitory control and selective visual attention. Cognitive performance for most measures was impaired immediately after scheduled awakening and improved over the first ~2-4h of wakefulness (sleep inertia); worsened thereafter until scheduled bedtime (sleep homeostasis); and was worst at ~60° and best at ~240° (circadian modulation, with worst and best phases corresponding to ~9AM and ~9PM respectively, in individuals with a habitual waketime of 7AM). The relative influences of sleep inertia, sleep homeostasis, and circadian phase depended on the specific higher-order cognitive function task examined. Inhibitory control appeared to be modulated most strongly by circadian phase, whereas selective visual attention for a spatial-configuration search task was modulated most strongly by sleep inertia. These findings demonstrate that some higher-order cognitive processes are differentially sensitive to different sleep-wake regulatory processes. Differential modulation of cognitive functions by different sleep-wake regulatory processes has important implications for understanding mechanisms contributing to performance impairments during adverse circadian phases, sleep deprivation, and/or upon awakening from sleep. PMID:25773686

Impact of submerged aquatic macrophytes on 3-dim current systems and hydrodynamic transport processes in Lake Constance

NASA Astrophysics Data System (ADS)

Wolf, Thomas; Lüddeke, Frauke; Thiange, Christophe

2015-04-01

According to the assessment criteria of the European water framework directive Lake Constance is having a good water quality. Nevertheless upcoming criteria using environmental quality measures show that there are still problems with respect to micropollutants. In fact, we observe significantly enhanced concentrations of micropollutants close to river mouths and in the areas of shallow water zones within Lake Constance compared to deep water concentrations. These findings are caused by river water plumes which can flow over distances of kilometers in the lake without being diluted or mixed only weakly with the surrounding lake water body. Besides, in the area of interest exist large populations of submerged aquatic macrophytes (SAM). There is only little knowledge, how these influence the distribution and transport processes of micropollutants. In order to assess the impact and distribution of river water plumes in different areas of the lake we implemented a 3-dim hydrodynamic model using DELFT3D-FLOW on a locally refined numerical grid which enables to cover different process scales of the distribution of river water bodies ranging from a few meters up to basin wide scales in the order of a few kilometers. We used numerical tracers (conservative and non-conservative) in order to quantify the impact of different abstract substance classes which are distinguished by their decay rates. In order to asses the influence of SAM populations on current field and transport processes we used a special simulation technique - the trachytope concept. The results of our 3-dim hydrodynamic model showed significantly changed current velocities, residence times and age of water parameters within the SAM areas compared to the control simulation without SAM. By simulating the propagation of coliform bacteria using numerical tracers with spatially and temporarily variable decay rates, we found complex impact pattern of the SAM on the distribution of these potentially harmful microorganisms.

Numerical Simulations of Acoustically Driven, Burning Droplets

NASA Technical Reports Server (NTRS)

Kim, H.-C.; Karagozian, A. R.; Smith, O. I.; Urban, Dave (Technical Monitor)

1999-01-01

This computational study focuses on understanding and quantifying the effects of external acoustical perturbations on droplet combustion. A one-dimensional, axisymmetric representation of the essential diffusion and reaction processes occurring in the vicinity of the droplet stagnation point is used here in order to isolate the effects of the imposed acoustic disturbance. The simulation is performed using a third order accurate, essentially non-oscillatory (ENO) numerical scheme with a full methanol-air reaction mechanism. Consistent with recent microgravity and normal gravity combustion experiments, focus is placed on conditions where the droplet is situated at a velocity antinode in order for the droplet to experience the greatest effects of fluid mechanical straining of flame structures. The effects of imposed sound pressure level and frequency are explored here, and conditions leading to maximum burning rates are identified.

Numerical study of Wavy Blade Section for Wind Turbines

NASA Astrophysics Data System (ADS)

Kobæk, C. M.; Hansen, M. O. L.

2016-09-01

The Wavy Blade concept is inspired by the unique flipper of a humpback whale, characterized by the tubercles located at the leading edge. It has been suggested that this shape may have been a result of a natural selection process, since this flipper under some circumstances can produce higher lift than a flipper having a smooth trailing edge and thus could be potentially beneficial when catching food. A thorough literature study of the Wavy Blade concept is made and followed by CFD computations of two wavy blade geometries and a comparison with their baseline S809 airfoil at conditions more relevant for modern wind turbines. The findings in the literature from geometries similar to the hump back whale flipper indicate that the aerodynamic performance can be improved at high angles of attack, but sometimes at the expense of a lower lift slope and increased drag before stall. The numerical results for a blade section based on the S809 airfoil are, however, not as promising as some of the findings reported in the literature for the whale flipper at high angles of attack. These first CFD computations using a thicker airfoil and a higher Reynolds number than the whale flipper indicate that the results may very well depend on the actual airfoil geometry and perhaps also the Reynolds number, and future studies are necessary in order to illuminate this further.

Construction of moment-matching multinomial lattices using Vandermonde matrices and Gröbner bases

NASA Astrophysics Data System (ADS)

Lundengârd, Karl; Ogutu, Carolyne; Silvestrov, Sergei; Ni, Ying; Weke, Patrick

2017-01-01

In order to describe and analyze the quantitative behavior of stochastic processes, such as the process followed by a financial asset, various discretization methods are used. One such set of methods are lattice models where a time interval is divided into equal time steps and the rate of change for the process is restricted to a particular set of values in each time step. The well-known binomial- and trinomial models are the most commonly used in applications, although several kinds of higher order models have also been examined. Here we will examine various ways of designing higher order lattice schemes with different node placements in order to guarantee moment-matching with the process.

Block structured adaptive mesh and time refinement for hybrid, hyperbolic + N-body systems

NASA Astrophysics Data System (ADS)

Miniati, Francesco; Colella, Phillip

2007-11-01

We present a new numerical algorithm for the solution of coupled collisional and collisionless systems, based on the block structured adaptive mesh and time refinement strategy (AMR). We describe the issues associated with the discretization of the system equations and the synchronization of the numerical solution on the hierarchy of grid levels. We implement a code based on a higher order, conservative and directionally unsplit Godunov’s method for hydrodynamics; a symmetric, time centered modified symplectic scheme for collisionless component; and a multilevel, multigrid relaxation algorithm for the elliptic equation coupling the two components. Numerical results that illustrate the accuracy of the code and the relative merit of various implemented schemes are also presented.

Supercomputer modeling of flow past hypersonic flight vehicles

NASA Astrophysics Data System (ADS)

Ermakov, M. K.; Kryukov, I. A.

2017-02-01

A software platform for MPI-based parallel solution of the Navier-Stokes (Euler) equations for viscous heat-conductive compressible perfect gas on 3-D unstructured meshes is developed. The discretization and solution of the Navier-Stokes equations are constructed on generalized S.K. Godunov’s method and the second order approximation in space and time. Developed software platform allows to carry out effectively flow past hypersonic flight vehicles simulations for the Mach numbers 6 and higher, and numerical meshes with up to 1 billion numerical cells and with up to 128 processors.

Vortex sheet modeling with higher order curved panels. Ph.D Thesis Final Technical Report

NASA Technical Reports Server (NTRS)

Nagati, M. G.

1985-01-01

A numerical technique is presented for modeling the vortex sheet with a deformable surface definition, along which a continuous vortex strength distribution in the spanwise direction is applied, so that by repeatedly modifying its shape, its true configuration is approached, in the proximity of its generating wing. Design problems requiring the inclusion of a realistic configuration of the vortex sheet are numerous. Examples discussed include: control effectiveness and stability derivatives, longitudinal stability, lateral stability, canards, propellers and helicopter rotors, and trailing vortex hazards.

Numerical solution for weight reduction model due to health campaigns in Spain

NASA Astrophysics Data System (ADS)

Mohammed, Maha A.; Noor, Noor Fadiya Mohd; Siri, Zailan; Ibrahim, Adriana Irawati Nur

2015-10-01

Transition model between three subpopulations based on Body Mass Index of Valencia community in Spain is considered. No changes in population nutritional habits and public health strategies on weight reduction until 2030 are assumed. The system of ordinary differential equations is solved using Runge-Kutta method of higher order. The numerical results obtained are compared with the predicted values of subpopulation proportion based on statistical estimation in 2013, 2015 and 2030. Relative approximate error is calculated. The consistency of the Runge-Kutta method in solving the model is discussed.

Random element method for numerical modeling of diffusional processes

NASA Technical Reports Server (NTRS)

Ghoniem, A. F.; Oppenheim, A. K.

1982-01-01

The random element method is a generalization of the random vortex method that was developed for the numerical modeling of momentum transport processes as expressed in terms of the Navier-Stokes equations. The method is based on the concept that random walk, as exemplified by Brownian motion, is the stochastic manifestation of diffusional processes. The algorithm based on this method is grid-free and does not require the diffusion equation to be discritized over a mesh, it is thus devoid of numerical diffusion associated with finite difference methods. Moreover, the algorithm is self-adaptive in space and explicit in time, resulting in an improved numerical resolution of gradients as well as a simple and efficient computational procedure. The method is applied here to an assortment of problems of diffusion of momentum and energy in one-dimension as well as heat conduction in two-dimensions in order to assess its validity and accuracy. The numerical solutions obtained are found to be in good agreement with exact solution except for a statistical error introduced by using a finite number of elements, the error can be reduced by increasing the number of elements or by using ensemble averaging over a number of solutions.

IoGET: Internet of Geophysical and Environmental Things

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mudunuru, Maruti Kumar

The objective of this project is to provide novel and fast reduced-order models for onboard computation at sensor nodes for real-time analysis. The approach will require that LANL perform high-fidelity numerical simulations, construct simple reduced-order models (ROMs) using machine learning and signal processing algorithms, and use real-time data analysis for ROMs and compressive sensing at sensor nodes.

Automated Web-Based Request Mechanism for Workflow Enhancement in an Academic Customer-Focused Biorepository.

PubMed

McDonald, Sandra A; Ryan, Benjamin J; Brink, Amy; Holtschlag, Victoria L

2012-02-01

Informatics systems, particularly those that provide capabilities for data storage, specimen tracking, retrieval, and order fulfillment, are critical to the success of biorepositories and other laboratories engaged in translational medical research. A crucial item-one easily overlooked-is an efficient way to receive and process investigator-initiated requests. A successful electronic ordering system should allow request processing in a maximally efficient manner, while also allowing streamlined tracking and mining of request data such as turnaround times and numerical categorizations (user groups, funding sources, protocols, and so on). Ideally, an electronic ordering system also facilitates the initial contact between the laboratory and customers, while still allowing for downstream communications and other steps toward scientific partnerships. We describe here the recently established Web-based ordering system for the biorepository at Washington University Medical Center, along with its benefits for workflow, tracking, and customer service. Because of the system's numerous value-added impacts, we think our experience can serve as a good model for other customer-focused biorepositories, especially those currently using manual or non-Web-based request systems. Our lessons learned also apply to the informatics developers who serve such biobanks.

Simulation of substrate degradation in composting of sewage sludge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Jun; Gao Ding, E-mail: gaod@igsnrr.ac.c; Chen Tongbin

2010-10-15

To simulate the substrate degradation kinetics of the composting process, this paper develops a mathematical model with a first-order reaction assumption and heat/mass balance equations. A pilot-scale composting test with a mixture of sewage sludge and wheat straw was conducted in an insulated reactor. The BVS (biodegradable volatile solids) degradation process, matrix mass, MC (moisture content), DM (dry matter) and VS (volatile solid) were simulated numerically by the model and experimental data. The numerical simulation offered a method for simulating k (the first-order rate constant) and estimating k{sub 20} (the first-order rate constant at 20 {sup o}C). After comparison withmore » experimental values, the relative error of the simulation value of the mass of the compost at maturity was 0.22%, MC 2.9%, DM 4.9% and VS 5.2%, which mean that the simulation is a good fit. The k of sewage sludge was simulated, and k{sub 20}, k{sub 20s} (first-order rate coefficient of slow fraction of BVS at 20 {sup o}C) of the sewage sludge were estimated as 0.082 and 0.015 d{sup -1}, respectively.« less

Automated Web-Based Request Mechanism for Workflow Enhancement in an Academic Customer-Focused Biorepository

PubMed Central

Ryan, Benjamin J.; Brink, Amy; Holtschlag, Victoria L.

2012-01-01

Informatics systems, particularly those that provide capabilities for data storage, specimen tracking, retrieval, and order fulfillment, are critical to the success of biorepositories and other laboratories engaged in translational medical research. A crucial item—one easily overlooked—is an efficient way to receive and process investigator-initiated requests. A successful electronic ordering system should allow request processing in a maximally efficient manner, while also allowing streamlined tracking and mining of request data such as turnaround times and numerical categorizations (user groups, funding sources, protocols, and so on). Ideally, an electronic ordering system also facilitates the initial contact between the laboratory and customers, while still allowing for downstream communications and other steps toward scientific partnerships. We describe here the recently established Web-based ordering system for the biorepository at Washington University Medical Center, along with its benefits for workflow, tracking, and customer service. Because of the system's numerous value-added impacts, we think our experience can serve as a good model for other customer-focused biorepositories, especially those currently using manual or non-Web–based request systems. Our lessons learned also apply to the informatics developers who serve such biobanks. PMID:23386921

Modeling Laser Wakefield Accelerators in a Lorentz Boosted Frame

NASA Astrophysics Data System (ADS)

Vay, J.-L.; Geddes, C. G. R.; Benedetti, C.; Bruhwiler, D. L.; Cormier-Michel, E.; Cowan, B. M.; Cary, J. R.; Grote, D. P.

2010-11-01

Modeling of laser-plasma wakefield accelerators in an optimal frame of reference has been shown to produce up to three orders of magnitude speed-up in calculations from first principles of stages in the 100 MeV-10 GeV energy range. Maximum obtainable speedups calculated using linear theory predict that higher speedups are attainable, in the range of 4-6 orders of magnitude for stages in the energy range of 10 GeV-1 TeV respectively. Practical limitations have been reported and discussed which have prevented reaching these speedups so far, including a violent high frequency numerical instability. The limitations are briefly reviewed and discussed in this paper, as well as their mitigation. It is also reported that the high frequency numerical instability can be controlled effectively using novel numerical techniques that have been implemented in the Particle-In-Cell code Warp, and that 5 and 6 orders of magnitude speedups were demonstrated on 100 GeV and 1 TeV stages respectively, verifying the scaling of plasma accelerators to very high energies, and providing highly efficient tools for the detailed designs of experiments on new lasers such as BELLA.

A multilevel control system for the large space telescope. [numerical analysis/optimal control

NASA Technical Reports Server (NTRS)

Siljak, D. D.; Sundareshan, S. K.; Vukcevic, M. B.

1975-01-01

A multilevel scheme was proposed for control of Large Space Telescope (LST) modeled by a three-axis-six-order nonlinear equation. Local controllers were used on the subsystem level to stabilize motions corresponding to the three axes. Global controllers were applied to reduce (and sometimes nullify) the interactions among the subsystems. A multilevel optimization method was developed whereby local quadratic optimizations were performed on the subsystem level, and global control was again used to reduce (nullify) the effect of interactions. The multilevel stabilization and optimization methods are presented as general tools for design and then used in the design of the LST Control System. The methods are entirely computerized, so that they can accommodate higher order LST models with both conceptual and numerical advantages over standard straightforward design techniques.

Efficient high-order structure-preserving methods for the generalized Rosenau-type equation with power law nonlinearity

NASA Astrophysics Data System (ADS)

Cai, Jiaxiang; Liang, Hua; Zhang, Chun

2018-06-01

Based on the multi-symplectic Hamiltonian formula of the generalized Rosenau-type equation, a multi-symplectic scheme and an energy-preserving scheme are proposed. To improve the accuracy of the solution, we apply the composition technique to the obtained schemes to develop high-order schemes which are also multi-symplectic and energy-preserving respectively. Discrete fast Fourier transform makes a significant improvement to the computational efficiency of schemes. Numerical results verify that all the proposed schemes have satisfactory performance in providing accurate solution and preserving the discrete mass and energy invariants. Numerical results also show that although each basic time step is divided into several composition steps, the computational efficiency of the composition schemes is much higher than that of the non-composite schemes.

Reformulated pavement remaining service life framework.

DOT National Transportation Integrated Search

2013-11-01

"Many important decisions are necessary in order to effectively provide and manage a pavement network. At the heart : of this process is the prediction of needed future construction events. One approach to providing a single numeric on : the conditio...

Pavement remaining service interval implementation guidelines.

DOT National Transportation Integrated Search

2013-11-01

"Many important decisions are necessary in order to effectively provide and manage a pavement network. At the heart of this : process is the prediction of needed future construction events. One approach to providing a single numeric on the condition ...

Higher Education Act Reauthorization: Homeless and Foster Youth

ERIC Educational Resources Information Center

National Association for the Education of Homeless Children and Youth, 2008

2008-01-01

Youth experiencing homelessness or in foster care face numerous barriers to higher education. Inadequate college readiness, the complexity of the financial aid process, and lack of housing and support services once enrolled in college make obtaining a college degree an often insurmountable challenge. Yet a college education offers these youth the…

Prediction Of The Fracture Due To Mannesmann Effect In Tube Piercing

NASA Astrophysics Data System (ADS)

Fanini, S.; Ghiotti, A.; Bruschi, S.

2007-05-01

Mannesmann piercing process is a well-known hot rolling process used for seamless tube production. Its special feature is the so-called Mannesmann effect, that is the cavity formation in the center of the cylindrical billet and its propagation along the axis due to stress state caused by the rolls in the early stages of the process. The cavity is then expanded and sized in its internal diameter by an incoming plug. The industrial requirement is to know quite precisely the characteristics of the cavity especially in terms of its location along the billet axis in order to minimize the plug wear and the oxidation of the pierced bar. However, the scientific knowledge about the fracture mechanism leading to the Mannesmann effect is still limited, even if several theories have been proposed; this lack makes the design and optimization of the process through numerical simulations still a challenging task. The aim of this work is then to develop a suitably calibrated FE model of the piercing process in its first stage before the plug arrival, in order to investigate the Mannesmann effect using different damage criteria. Hot tensile tests, capable to reproduce the industrial conditions in terms of temperature, strain rate, and stress states, are carried out to investigate the material workability and to determine the parameters of the damage models on specimens machined from continuous-casting steel billets. The calculated parameters are implemented in the numerical model of the process and a sensitivity analysis to the different criteria is carried out, comparing numerical results with non-plug piercing tests conducted in the industrial plant.

Post-Newtonian factorized multipolar waveforms for spinning, nonprecessing black-hole binaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Yi; Buonanno, Alessandra; Racine, Etienne

2011-03-15

We generalize the factorized resummation of multipolar waveforms introduced by Damour, Iyer, and Nagar to spinning black holes. For a nonspinning test particle spiraling a Kerr black hole in the equatorial plane, we find that factorized multipolar amplitudes which replace the residual relativistic amplitude f{sub lm} with its lth root, {rho}{sub lm}=f{sub lm}{sup 1/l}, agree quite well with the numerical amplitudes up to the Kerr-spin value q{<=}0.95 for orbital velocities v{<=}0.4. The numerical amplitudes are computed solving the Teukolsky equation with a spectral code. The agreement for prograde orbits and large spin values of the Kerr black-hole can be furthermore » improved at high velocities by properly factoring out the lower-order post-Newtonian contributions in {rho}{sub lm}. The resummation procedure results in a better and systematic agreement between numerical and analytical amplitudes (and energy fluxes) than standard Taylor-expanded post-Newtonian approximants. This is particularly true for higher-order modes, such as (2,1), (3,3), (3,2), and (4,4), for which less spin post-Newtonian terms are known. We also extend the factorized resummation of multipolar amplitudes to generic mass-ratio, nonprecessing, spinning black holes. Lastly, in our study we employ new, recently computed, higher-order post-Newtonian terms in several subdominant modes and compute explicit expressions for the half and one-and-half post-Newtonian contributions to the odd-parity (current) and even-parity (odd) multipoles, respectively. Those results can be used to build more accurate templates for ground-based and space-based gravitational-wave detectors.« less

Physical uniqueness of higher-order Korteweg-de Vries theory for continuously stratified fluids without background shear

NASA Astrophysics Data System (ADS)

Shimizu, Kenji

2017-10-01

The 2nd-order Korteweg-de Vries (KdV) equation and the Gardner (or extended KdV) equation are often used to investigate internal solitary waves, commonly observed in oceans and lakes. However, application of these KdV-type equations for continuously stratified fluids to geophysical problems is hindered by nonuniqueness of the higher-order coefficients and the associated correction functions to the wave fields. This study proposes to reduce arbitrariness of the higher-order KdV theory by considering its uniqueness in the following three physical senses: (i) consistency of the nonlinear higher-order coefficients and correction functions with the corresponding phase speeds, (ii) wavenumber-independence of the vertically integrated available potential energy, and (iii) its positive definiteness. The spectral (or generalized Fourier) approach based on vertical modes in the isopycnal coordinate is shown to enable an alternative derivation of the 2nd-order KdV equation, without encountering nonuniqueness. Comparison with previous theories shows that Parseval's theorem naturally yields a unique set of special conditions for (ii) and (iii). Hydrostatic fully nonlinear solutions, derived by combining the spectral approach and simple-wave analysis, reveal that both proposed and previous 2nd-order theories satisfy (i), provided that consistent definitions are used for the wave amplitude and the nonlinear correction. This condition reduces the arbitrariness when higher-order KdV-type theories are compared with observations or numerical simulations. The coefficients and correction functions that satisfy (i)-(iii) are given by explicit formulae to 2nd order and by algebraic recurrence relationships to arbitrary order for hydrostatic fully nonlinear and linear fully nonhydrostatic effects.

On a turbulent wall model to predict hemolysis numerically in medical devices

NASA Astrophysics Data System (ADS)

Lee, Seunghun; Chang, Minwook; Kang, Seongwon; Hur, Nahmkeon; Kim, Wonjung

2017-11-01

Analyzing degradation of red blood cells is very important for medical devices with blood flows. The blood shear stress has been recognized as the most dominant factor for hemolysis in medical devices. Compared to laminar flows, turbulent flows have higher shear stress values in the regions near the wall. In case of predicting hemolysis numerically, this phenomenon can require a very fine mesh and large computational resources. In order to resolve this issue, the purpose of this study is to develop a turbulent wall model to predict the hemolysis more efficiently. In order to decrease the numerical error of hemolysis prediction in a coarse grid resolution, we divided the computational domain into two regions and applied different approaches to each region. In the near-wall region with a steep velocity gradient, an analytic approach using modeled velocity profile is applied to reduce a numerical error to allow a coarse grid resolution. We adopt the Van Driest law as a model for the mean velocity profile. In a region far from the wall, a regular numerical discretization is applied. The proposed turbulent wall model is evaluated for a few turbulent flows inside a cannula and centrifugal pumps. The results present that the proposed turbulent wall model for hemolysis improves the computational efficiency significantly for engineering applications. Corresponding author.

Research on Interventions for Adolescents with Learning Disabilities: A Meta-Analysis of Outcomes Related to Higher-Order Processing.

ERIC Educational Resources Information Center

Swanson, H. Lee

2001-01-01

Details meta-analysis of 58 intervention studies related to higher-order processing (i.e., problem solving) for adolescents with learning disabilities. Discusses factors that increased effect sizes: (1) measures of metacognition and text understanding; (2) instruction including advanced organizers, new skills, and extended practice; and (3)…

An Order Insertion Scheduling Model of Logistics Service Supply Chain Considering Capacity and Time Factors

PubMed Central

Yang, Yi; Wang, Shuqing; Liu, Yang

2014-01-01

Order insertion often occurs in the scheduling process of logistics service supply chain (LSSC), which disturbs normal time scheduling especially in the environment of mass customization logistics service. This study analyses order similarity coefficient and order insertion operation process and then establishes an order insertion scheduling model of LSSC with service capacity and time factors considered. This model aims to minimize the average unit volume operation cost of logistics service integrator and maximize the average satisfaction degree of functional logistics service providers. In order to verify the viability and effectiveness of our model, a specific example is numerically analyzed. Some interesting conclusions are obtained. First, along with the increase of completion time delay coefficient permitted by customers, the possible inserting order volume first increases and then trends to be stable. Second, supply chain performance reaches the best when the volume of inserting order is equal to the surplus volume of the normal operation capacity in mass service process. Third, the larger the normal operation capacity in mass service process is, the bigger the possible inserting order's volume will be. Moreover, compared to increasing the completion time delay coefficient, improving the normal operation capacity of mass service process is more useful. PMID:25276851

Testing higher-order Lagrangian perturbation theory against numerical simulations. 2: Hierarchical models

NASA Technical Reports Server (NTRS)

Melott, A. L.; Buchert, T.; Weib, A. G.

1995-01-01

We present results showing an improvement of the accuracy of perturbation theory as applied to cosmological structure formation for a useful range of scales. The Lagrangian theory of gravitational instability of Friedmann-Lemaitre cosmogonies is compared with numerical simulations. We study the dynamics of hierarchical models as a second step. In the first step we analyzed the performance of the Lagrangian schemes for pancake models, the difference being that in the latter models the initial power spectrum is truncated. This work probed the quasi-linear and weakly non-linear regimes. We here explore whether the results found for pancake models carry over to hierarchical models which are evolved deeply into the non-linear regime. We smooth the initial data by using a variety of filter types and filter scales in order to determine the optimal performance of the analytical models, as has been done for the 'Zel'dovich-approximation' - hereafter TZA - in previous work. We find that for spectra with negative power-index the second-order scheme performs considerably better than TZA in terms of statistics which probe the dynamics, and slightly better in terms of low-order statistics like the power-spectrum. However, in contrast to the results found for pancake models, where the higher-order schemes get worse than TZA at late non-linear stages and on small scales, we here find that the second-order model is as robust as TZA, retaining the improvement at later stages and on smaller scales. In view of these results we expect that the second-order truncated Lagrangian model is especially useful for the modelling of standard dark matter models such as Hot-, Cold-, and Mixed-Dark-Matter.

Guiding and amplification properties of rod-type photonic crystal fibers with sectioned core doping

NASA Astrophysics Data System (ADS)

Selleri, S.; Poli, F.; Passaro, D.; Cucinotta, A.; Lægsgaard, J.; Broeng, J.

2009-05-01

Rod-type photonic crystal fibers are large mode area double-cladding fibers with an outer diameter of few millimeters which can provide important advantages for high-power lasers and amplifiers. Numerical studies have recently demonstrated the guidance of higher-order modes in these fibers, which can worsen the output beam quality of lasers and amplifiers. In the present analysis a sectioned core doping has been proposed for Ybdoped rod-type photonic crystal fibers, with the aim to improve the higher-order mode suppression. A full-vector modal solver based on the finite element method has been applied to properly design the low refractive index ring in the fiber core, which can provide an increase of the differential overlap between the fundamental and the higher-order mode. Then, the gain competition among the guided modes along the Yb-doped rod-type fibers has been investigated with a spatial and spectral amplifier model. Simulation results have shown the effectiveness of the sectioned core doping in worsening the higher-order mode overlap on the doped area, thus providing an effective single-mode behavior of the Yb-doped rod-type photonic crystal fibers.

Combustion and Magnetohydrodynamic Processes in Advanced Pulse Detonation Rocket Engines

DTIC Science & Technology

2012-10-01

use of high-order numerical methods can also be a powerful tool in the analysis of such complex flows, but we need to understand the interaction of...computational physics, 43(2):357372, 1981. [47] B. Einfeldt. On godunov-type methods for gas dynamics . SIAM Journal on Numerical Analysis , pages 294...dimensional effects with complex reaction kinetics, the simple one-dimensional detonation structure provides a rich spectrum of dynamical features which are

Multiple scattering effects with cyclical terms in active remote sensing of vegetated surface using vector radiative transfer theory

USDA-ARS?s Scientific Manuscript database

The energy transport in a vegetated (corn) surface layer is examined by solving the vector radiative transfer equation using a numerical iterative approach. This approach allows a higher order that includes the multiple scattering effects. Multiple scattering effects are important when the optical t...

Strategies for Professors Who Service the University to Earn Tenure and Promotion

ERIC Educational Resources Information Center

Gentry, Ruben; Stokes, Dorothy

2015-01-01

Tenure and promotion are great aspirations for college professors. They are indicators of success in the professions. Universities stipulate in their official documents and numerous higher education publications specify what professors must achieve in order to earn tenure and promotion; which almost always cite effectiveness in teaching, research,…

Full counting statistics of conductance for disordered systems

NASA Astrophysics Data System (ADS)

Fu, Bin; Zhang, Lei; Wei, Yadong; Wang, Jian

2017-09-01

Quantum transport is a stochastic process in nature. As a result, the conductance is fully characterized by its average value and fluctuations, i.e., characterized by full counting statistics (FCS). Since disorders are inevitable in nanoelectronic devices, it is important to understand how FCS behaves in disordered systems. The traditional approach dealing with fluctuations or cumulants of conductance uses diagrammatic perturbation expansion of the Green's function within coherent potential approximation (CPA), which is extremely complicated especially for high order cumulants. In this paper, we develop a theoretical formalism based on nonequilibrium Green's function by directly taking the disorder average on the generating function of FCS of conductance within CPA. This is done by mapping the problem into higher dimensions so that the functional dependence of generating a function on the Green's function becomes linear and the diagrammatic perturbation expansion is not needed anymore. Our theory is very simple and allows us to calculate cumulants of conductance at any desired order efficiently. As an application of our theory, we calculate the cumulants of conductance up to fifth order for disordered systems in the presence of Anderson and binary disorders. Our numerical results of cumulants of conductance show remarkable agreement with that obtained by the brute force calculation.

Examining substance use and affective processes as multivariate risk factors associated with overweight body mass among treatment-seeking smokers.

PubMed

Farris, Samantha G; Zvolensky, Michael J; Robles, Zuzuky; Schmidt, Norman B

2015-01-01

Cigarette smoking and obesity are two major public health problems. However, factors related to the underlying risk for being overweight are not well established. Certain demographic, smoking, and psychological factors have been linked to overweight/obese body mass. The current study examined a multivariate risk model, stratified by gender, in order to better explicate the nature of overweight body mass among daily smokers. In a sample of treatment-seeking smokers (n = 395), among males and females, (1) older age, (2) stronger expectancies about the weight/appetite control effects of smoking, (3) greater smoking-based inflexibility/avoidance due to smoking-related sensations, and (4) less problematic alcohol use, were associated with being overweight. Additionally, among males, having a tobacco-related medical problem and higher tolerance for physical discomfort aided in the discriminant function model for classifying smokers as overweight. Together, numerous cognitive-affective vulnerabilities and smoking processes may be targetable and potentially inform weight-related prevention programs among smokers.

[Compartmentalization of the cell nucleus and spatial organization of the genome].

PubMed

Gavrilov, A A; Razin, S V

2015-01-01

The eukaryotic cell nucleus is one of the most complex cell organelles. Despite the absence of membranes, the nuclear space is divided into numerous compartments where different processes in- volved in the genome activity take place. The most important nuclear compartments include nucleoli, nuclear speckles, PML bodies, Cajal bodies, histone locus bodies, Polycomb bodies, insulator bodies, transcription and replication factories. The structural basis for the nuclear compartmentalization is provided by genomic DNA that occupies most of the nuclear volume. Nuclear compartments, in turn, guide the chromosome folding by providing a platform for the spatial interaction of individual genomic loci. In this review, we discuss fundamental principles of higher order genome organization with a focus on chromosome territories and chromosome domains, as well as consider the structure and function of the key nuclear compartments. We show that the func- tional compartmentalization of the cell nucleus and genome spatial organization are tightly interconnected, and that this form of organization is highly dynamic and is based on stochastic processes.

Numerical-analytic implementation of the higher-order canonical Van Vleck perturbation theory for the interpretation of medium-sized molecule vibrational spectra.

PubMed

Krasnoshchekov, Sergey V; Isayeva, Elena V; Stepanov, Nikolay F

2012-04-12

Anharmonic vibrational states of semirigid polyatomic molecules are often studied using the second-order vibrational perturbation theory (VPT2). For efficient higher-order analysis, an approach based on the canonical Van Vleck perturbation theory (CVPT), the Watson Hamiltonian and operators of creation and annihilation of vibrational quanta is employed. This method allows analysis of the convergence of perturbation theory and solves a number of theoretical problems of VPT2, e.g., yields anharmonic constants y(ijk), z(ijkl), and allows the reliable evaluation of vibrational IR and Raman anharmonic intensities in the presence of resonances. Darling-Dennison and higher-order resonance coupling coefficients can be reliably evaluated as well. The method is illustrated on classic molecules: water and formaldehyde. A number of theoretical conclusions results, including the necessity of using sextic force field in the fourth order (CVPT4) and the nearly vanishing CVPT4 contributions for bending and wagging modes. The coefficients of perturbative Dunham-type Hamiltonians in high-orders of CVPT are found to conform to the rules of equality at different orders as earlier proven analytically for diatomic molecules. The method can serve as a good substitution of the more traditional VPT2.

Low-Order Aberrations in Band-limited Lyot Coronagraphs

NASA Astrophysics Data System (ADS)

Sivaramakrishnan, Anand; Soummer, Rémi; Sivaramakrishnan, Allic V.; Lloyd, James P.; Oppenheimer, Ben R.; Makidon, Russell B.

2005-12-01

We study the way Lyot coronagraphs with unapodized entrance pupils respond to small, low-order phase aberrations. This study is applicable to ground-based adaptive optics coronagraphs operating at 90% and higher Strehl ratios, as well as to some space-based coronagraphs with intrinsically higher Strehl ratio imaging. We utilize a second-order expansion of the monochromatic point-spread function (written as a power spectrum of a power series in the phase aberration over clear aperture) to derive analytical expressions for the response of a ``band-limited'' Lyot coronagraph (BLC) to small, low-order, phase aberrations. The BLC possesses a focal plane mask with an occulting spot whose opacity profile is a spatially band-limited function rather than a hard-edged, opaque disk. The BLC is, to first order, insensitive to tilt and astigmatism. Undersizing the stop in the reimaged pupil plane (the Lyot plane) following the focal plane mask can alleviate second-order effects of astigmatism, at the expense of system throughput and angular resolution. The optimal degree of such undersizing depends on individual instrument designs and goals. Our analytical work engenders physical insight and complements existing numerical work on this subject. Our methods can be extended to treat the passage of higher order aberrations through band-limited Lyot coronagraphs by using our polynomial decomposition or an analogous Fourier approach.

Parameter estimation method that directly compares gravitational wave observations to numerical relativity

NASA Astrophysics Data System (ADS)

Lange, J.; O'Shaughnessy, R.; Boyle, M.; Calderón Bustillo, J.; Campanelli, M.; Chu, T.; Clark, J. A.; Demos, N.; Fong, H.; Healy, J.; Hemberger, D. A.; Hinder, I.; Jani, K.; Khamesra, B.; Kidder, L. E.; Kumar, P.; Laguna, P.; Lousto, C. O.; Lovelace, G.; Ossokine, S.; Pfeiffer, H.; Scheel, M. A.; Shoemaker, D. M.; Szilagyi, B.; Teukolsky, S.; Zlochower, Y.

2017-11-01

We present and assess a Bayesian method to interpret gravitational wave signals from binary black holes. Our method directly compares gravitational wave data to numerical relativity (NR) simulations. In this study, we present a detailed investigation of the systematic and statistical parameter estimation errors of this method. This procedure bypasses approximations used in semianalytical models for compact binary coalescence. In this work, we use the full posterior parameter distribution for only generic nonprecessing binaries, drawing inferences away from the set of NR simulations used, via interpolation of a single scalar quantity (the marginalized log likelihood, ln L ) evaluated by comparing data to nonprecessing binary black hole simulations. We also compare the data to generic simulations, and discuss the effectiveness of this procedure for generic sources. We specifically assess the impact of higher order modes, repeating our interpretation with both l ≤2 as well as l ≤3 harmonic modes. Using the l ≤3 higher modes, we gain more information from the signal and can better constrain the parameters of the gravitational wave signal. We assess and quantify several sources of systematic error that our procedure could introduce, including simulation resolution and duration; most are negligible. We show through examples that our method can recover the parameters for equal mass, zero spin, GW150914-like, and unequal mass, precessing spin sources. Our study of this new parameter estimation method demonstrates that we can quantify and understand the systematic and statistical error. This method allows us to use higher order modes from numerical relativity simulations to better constrain the black hole binary parameters.

A spectral hybridizable discontinuous Galerkin method for elastic-acoustic wave propagation

NASA Astrophysics Data System (ADS)

Terrana, S.; Vilotte, J. P.; Guillot, L.

2018-04-01

We introduce a time-domain, high-order in space, hybridizable discontinuous Galerkin (DG) spectral element method (HDG-SEM) for wave equations in coupled elastic-acoustic media. The method is based on a first-order hyperbolic velocity-strain formulation of the wave equations written in conservative form. This method follows the HDG approach by introducing a hybrid unknown, which is the approximation of the velocity on the elements boundaries, as the only globally (i.e. interelement) coupled degrees of freedom. In this paper, we first present a hybridized formulation of the exact Riemann solver at the element boundaries, taking into account elastic-elastic, acoustic-acoustic and elastic-acoustic interfaces. We then use this Riemann solver to derive an explicit construction of the HDG stabilization function τ for all the above-mentioned interfaces. We thus obtain an HDG scheme for coupled elastic-acoustic problems. This scheme is then discretized in space on quadrangular/hexahedral meshes using arbitrary high-order polynomial basis for both volumetric and hybrid fields, using an approach similar to the spectral element methods. This leads to a semi-discrete system of algebraic differential equations (ADEs), which thanks to the structure of the global conservativity condition can be reformulated easily as a classical system of first-order ordinary differential equations in time, allowing the use of classical explicit or implicit time integration schemes. When an explicit time scheme is used, the HDG method can be seen as a reformulation of a DG with upwind fluxes. The introduction of the velocity hybrid unknown leads to relatively simple computations at the element boundaries which, in turn, makes the HDG approach competitive with the DG-upwind methods. Extensive numerical results are provided to illustrate and assess the accuracy and convergence properties of this HDG-SEM. The approximate velocity is shown to converge with the optimal order of k + 1 in the L2-norm, when element polynomials of order k are used, and to exhibit the classical spectral convergence of SEM. Additional inexpensive local post-processing in both the elastic and the acoustic case allow to achieve higher convergence orders. The HDG scheme provides a natural framework for coupling classical, continuous Galerkin SEM with HDG-SEM in the same simulation, and it is shown numerically in this paper. As such, the proposed HDG-SEM can combine the efficiency of the continuous SEM with the flexibility of the HDG approaches. Finally, more complex numerical results, inspired from real geophysical applications, are presented to illustrate the capabilities of the method for wave propagation in heterogeneous elastic-acoustic media with complex geometries.

Numerical modeling and experimental validation of thermoplastic composites induction welding

NASA Astrophysics Data System (ADS)

Palmieri, Barbara; Nele, Luigi; Galise, Francesco

2018-05-01

In this work, a numerical simulation and experimental test of the induction welding of continuous fibre-reinforced thermoplastic composites (CFRTPCs) was provided. The thermoplastic Polyamide 66 (PA66) with carbon fiber fabric was used. Using a dedicated software (JMag Designer), the influence of the fundamental process parameters such as temperature, current and holding time was investigated. In order to validate the results of the simulations, and therefore the numerical model used, experimental tests were carried out, and the temperature values measured during the tests were compared with the aid of an optical pyrometer, with those provided by the numerical simulation. The mechanical properties of the welded joints were evaluated by single lap shear tests.

Thermal stresses and deflections of cross-ply laminated plates using refined plate theories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khdeir, A.A.; Reddy, J.N.

1991-12-01

Exact analytical solutions of refined plate theories are developed to study the thermal stresses and deflections of cross-ply rectangular plates. The state-space approach in conjunction with the Levy method is used to solve exactly the governing equations of the theories under various boundary conditions. Numerical results of the higher-order theory of Reddy for thermal stresses and deflections are compared with those obtained using the classical and first-order plate theories. 14 refs.

High-Order Polynomial Expansions (HOPE) for flux-vector splitting

NASA Technical Reports Server (NTRS)

Liou, Meng-Sing; Steffen, Chris J., Jr.

1991-01-01

The Van Leer flux splitting is known to produce excessive numerical dissipation for Navier-Stokes calculations. Researchers attempt to remedy this deficiency by introducing a higher order polynomial expansion (HOPE) for the mass flux. In addition to Van Leer's splitting, a term is introduced so that the mass diffusion error vanishes at M = 0. Several splittings for pressure are proposed and examined. The effectiveness of the HOPE scheme is illustrated for 1-D hypersonic conical viscous flow and 2-D supersonic shock-wave boundary layer interactions.

Novel third-order Lovelock wormhole solutions

NASA Astrophysics Data System (ADS)

Mehdizadeh, Mohammad Reza; Lobo, Francisco S. N.

2016-06-01

In this work, we consider wormhole geometries in third-order Lovelock gravity and investigate the possibility that these solutions satisfy the energy conditions. In this framework, by applying a specific equation of state, we obtain exact wormhole solutions, and by imposing suitable values for the parameters of the theory, we find that these geometries satisfy the weak energy condition in the vicinity of the throat, due to the presence of higher-order curvature terms. Finally, we trace out a numerical analysis, by assuming a specific redshift function, and find asymptotically flat solutions that satisfy the weak energy condition throughout the spacetime.

Numerical natural rubber curing simulation, obtaining a controlled gradient of the state of cure in a thick-section part

NASA Astrophysics Data System (ADS)

El Labban, A.; Mousseau, P.; Bailleul, J. L.; Deterre, R.

2007-04-01

Although numerical simulation has proved to be a useful tool to predict the rubber vulcanization process, few applications in the process control have been reported. Because the end-use rubber properties depend on the state of cure distribution in the parts thickness, the prediction of the optimal distribution remains a challenge for the rubber industry. The analysis of the vulcanization process requires the determination of the thermal behavior of the material and the cure kinetics. A nonisothermal vulcanization model with nonisothermal induction time is used in this numerical study. Numerical results are obtained for natural rubber (NR) thick-section part curing. A controlled gradient of the state of cure in the part thickness is obtained by a curing process that consists not only in mold heating phase, but also a forced convection mold cooling phase in order to stop the vulcanization process and to control the vulcanization distribution. The mold design that allows this control is described. In the heating phase, the state of cure is mainly controlled by the chemical kinetics (the induction time), but in the cooling phase, it is the heat diffusion that controls the state of cure distribution. A comparison among different cooling conditions is shown and a good state of cure gradient control is obtained.

Explanation of power law behavior of autoregressive conditional duration processes based on the random multiplicative process

NASA Astrophysics Data System (ADS)

Sato, Aki-Hiro

2004-04-01

Autoregressive conditional duration (ACD) processes, which have the potential to be applied to power law distributions of complex systems found in natural science, life science, and social science, are analyzed both numerically and theoretically. An ACD(1) process exhibits the singular second order moment, which suggests that its probability density function (PDF) has a power law tail. It is verified that the PDF of the ACD(1) has a power law tail with an arbitrary exponent depending on a model parameter. On the basis of theory of the random multiplicative process a relation between the model parameter and the power law exponent is theoretically derived. It is confirmed that the relation is valid from numerical simulations. An application of the ACD(1) to intervals between two successive transactions in a foreign currency market is shown.

Explanation of power law behavior of autoregressive conditional duration processes based on the random multiplicative process.

PubMed

Sato, Aki-Hiro

2004-04-01

Autoregressive conditional duration (ACD) processes, which have the potential to be applied to power law distributions of complex systems found in natural science, life science, and social science, are analyzed both numerically and theoretically. An ACD(1) process exhibits the singular second order moment, which suggests that its probability density function (PDF) has a power law tail. It is verified that the PDF of the ACD(1) has a power law tail with an arbitrary exponent depending on a model parameter. On the basis of theory of the random multiplicative process a relation between the model parameter and the power law exponent is theoretically derived. It is confirmed that the relation is valid from numerical simulations. An application of the ACD(1) to intervals between two successive transactions in a foreign currency market is shown.

Higher-order compositional modeling of three-phase flow in 3D fractured porous media based on cross-flow equilibrium

NASA Astrophysics Data System (ADS)

Moortgat, Joachim; Firoozabadi, Abbas

2013-10-01

Numerical simulation of multiphase compositional flow in fractured porous media, when all the species can transfer between the phases, is a real challenge. Despite the broad applications in hydrocarbon reservoir engineering and hydrology, a compositional numerical simulator for three-phase flow in fractured media has not appeared in the literature, to the best of our knowledge. In this work, we present a three-phase fully compositional simulator for fractured media, based on higher-order finite element methods. To achieve computational efficiency, we invoke the cross-flow equilibrium (CFE) concept between discrete fractures and a small neighborhood in the matrix blocks. We adopt the mixed hybrid finite element (MHFE) method to approximate convective Darcy fluxes and the pressure equation. This approach is the most natural choice for flow in fractured media. The mass balance equations are discretized by the discontinuous Galerkin (DG) method, which is perhaps the most efficient approach to capture physical discontinuities in phase properties at the matrix-fracture interfaces and at phase boundaries. In this work, we account for gravity and Fickian diffusion. The modeling of capillary effects is discussed in a separate paper. We present the mathematical framework, using the implicit-pressure-explicit-composition (IMPEC) scheme, which facilitates rigorous thermodynamic stability analyses and the computation of phase behavior effects to account for transfer of species between the phases. A deceptively simple CFL condition is implemented to improve numerical stability and accuracy. We provide six numerical examples at both small and larger scales and in two and three dimensions, to demonstrate powerful features of the formulation.

Clouds in the atmospheres of extrasolar planets. IV. On the scattering greenhouse effect of CO2 ice particles: Numerical radiative transfer studies

NASA Astrophysics Data System (ADS)

Kitzmann, D.; Patzer, A. B. C.; Rauer, H.

2013-09-01

Context. Owing to their wavelength-dependent absorption and scattering properties, clouds have a strong impact on the climate of planetary atmospheres. The potential greenhouse effect of CO2 ice clouds in the atmospheres of terrestrial extrasolar planets is of particular interest because it might influence the position and thus the extension of the outer boundary of the classic habitable zone around main sequence stars. Such a greenhouse effect, however, is a complicated function of the CO2 ice particles' optical properties. Aims: We study the radiative effects of CO2 ice particles obtained by different numerical treatments to solve the radiative transfer equation. To determine the effectiveness of the scattering greenhouse effect caused by CO2 ice clouds, the radiative transfer calculations are performed over the relevant wide range of particle sizes and optical depths, employing different numerical methods. Methods: We used Mie theory to calculate the optical properties of particle polydispersion. The radiative transfer calculations were done with a high-order discrete ordinate method (DISORT). Two-stream radiative transfer methods were used for comparison with previous studies. Results: The comparison between the results of a high-order discrete ordinate method and simpler two-stream approaches reveals large deviations in terms of a potential scattering efficiency of the greenhouse effect. The two-stream methods overestimate the transmitted and reflected radiation, thereby yielding a higher scattering greenhouse effect. For the particular case of a cool M-type dwarf, the CO2 ice particles show no strong effective scattering greenhouse effect by using the high-order discrete ordinate method, whereas a positive net greenhouse effect was found for the two-stream radiative transfer schemes. As a result, previous studies of the effects of CO2 ice clouds using two-stream approximations overrated the atmospheric warming caused by the scattering greenhouse effect. Consequently, the scattering greenhouse effect of CO2 ice particles seems to be less effective than previously estimated. In general, higher order radiative transfer methods are needed to describe the effects of CO2 ice clouds accurately as indicated by our numerical radiative transfer studies.

Theoretical and experimental study of bent fully aperiodic large-pitch fibers for enhancing the high-order modes delocalization

NASA Astrophysics Data System (ADS)

du Jeu, Rémi; Dauliat, Romain; Darwich, Dia; Auguste, Jean-Louis; Benoît, Aurélien; Leconte, Baptiste; Malleville, Marie-Alicia; Jamier, Raphaël.; Schuster, Kay; Roy, Philippe

2018-02-01

The power scaling of fiber lasers and amplifiers has triggered an extensive development of large-mode area fibers among which the most promising are the distributed mode filtering fibers and the large-pitch fibers. These structures enable for an effective higher-order modes delocalization and subsequently a singlemode emission. An interesting alternative consists in using the fully-aperiodic large-pitch fibers, into which the standard air-silica photonic crystal cladding is replaced by an aperiodic pattern made of solid low-index inclusions cladding. However, in such a structure, the core and the background cladding material surrounding it must have rigorously the same refractive index. Current synthesis processes and measurement techniques offer respectively a maximum resolution of 5×10-4 and 1×10-4 while the indexmatching must be as precise as 1×10-5 . Lately a gain material with a refractive index 1.5×10-4 higher than that of the background cladding material was fabricated, thus re-confining the first higher-order modes in the core. A numerical study is carried out on the benefit of bending such fully-aperiodic fiber to counteract this phenomenon. Optimized bending axis and radius have been determined. Experiments are done in a laser cavity operating at 1030 nm using an 88cm-long 51μm core diameter ytterbium-doped fiber. Results demonstrate an improvement of the M2 from 1.7 when the fiber is kept straight to 1.2 when it is bent with a 100 to 60 cm bend radius. These primary results are promising for future power scaling.

Predictive Simulation of Process Windows for Powder Bed Fusion Additive Manufacturing: Influence of the Powder Bulk Density.

PubMed

Rausch, Alexander M; Küng, Vera E; Pobel, Christoph; Markl, Matthias; Körner, Carolin

2017-09-22

The resulting properties of parts fabricated by powder bed fusion additive manufacturing processes are determined by their porosity, local composition, and microstructure. The objective of this work is to examine the influence of the stochastic powder bed on the process window for dense parts by means of numerical simulation. The investigations demonstrate the unique capability of simulating macroscopic domains in the range of millimeters with a mesoscopic approach, which resolves the powder bed and the hydrodynamics of the melt pool. A simulated process window reveals the influence of the stochastic powder layer. The numerical results are verified with an experimental process window for selective electron beam-melted Ti-6Al-4V. Furthermore, the influence of the powder bulk density is investigated numerically. The simulations predict an increase in porosity and surface roughness for samples produced with lower powder bulk densities. Due to its higher probability for unfavorable powder arrangements, the process stability is also decreased. This shrinks the actual parameter range in a process window for producing dense parts.

Predictive Simulation of Process Windows for Powder Bed Fusion Additive Manufacturing: Influence of the Powder Bulk Density

PubMed Central

Rausch, Alexander M.; Küng, Vera E.; Pobel, Christoph; Körner, Carolin

2017-01-01

The resulting properties of parts fabricated by powder bed fusion additive manufacturing processes are determined by their porosity, local composition, and microstructure. The objective of this work is to examine the influence of the stochastic powder bed on the process window for dense parts by means of numerical simulation. The investigations demonstrate the unique capability of simulating macroscopic domains in the range of millimeters with a mesoscopic approach, which resolves the powder bed and the hydrodynamics of the melt pool. A simulated process window reveals the influence of the stochastic powder layer. The numerical results are verified with an experimental process window for selective electron beam-melted Ti-6Al-4V. Furthermore, the influence of the powder bulk density is investigated numerically. The simulations predict an increase in porosity and surface roughness for samples produced with lower powder bulk densities. Due to its higher probability for unfavorable powder arrangements, the process stability is also decreased. This shrinks the actual parameter range in a process window for producing dense parts. PMID:28937633

Evidence for different processes involved in the effects of nontemporal stimulus size and numerical digit value on duration judgments.

PubMed

Rammsayer, Thomas H; Verner, Martin

2016-05-01

Perceived duration has been shown to be positively related to task-irrelevant, nontemporal stimulus magnitude. To account for this finding, Walsh's (2003) A Theory of Magnitude (ATOM) model suggests that magnitude of time is not differentiated from magnitude of other nontemporal stimulus characteristics and collectively processed by a generalized magnitude system. In Experiment 1, we investigated the combined effects of stimulus size and numerical quantity, as two nontemporal stimulus dimensions covered by the ATOM model, on duration judgments. Participants were required to reproduce the duration of target intervals marked by Arabic digits varying in physical size and numerical value. While the effect of stimulus size was effectively moderated by target duration, the effect of numerical value appeared to require attentional resources directed to the numerical value in order to become effective. Experiment 2 was designed to further elucidate the mediating influence of attention on the effect of numerical value on duration judgments. An effect of numerical value was only observed when participants' attention was directed to digit value, but not when participants were required to pay special attention to digit parity. While the ATOM model implies a common metrics and generalized magnitude processing for time, size, and quantity, the present findings provided converging evidence for the notion of two qualitatively different mechanisms underlying the effects of nontemporal stimulus size and numerical value on duration judgments. Furthermore, our data challenge the implicit common assumption that the effect of numerical value on duration judgments represents a continuously increasing function of digit magnitude.

The terminal area simulation system. Volume 1: Theoretical formulation

NASA Technical Reports Server (NTRS)

Proctor, F. H.

1987-01-01

A three-dimensional numerical cloud model was developed for the general purpose of studying convective phenomena. The model utilizes a time splitting integration procedure in the numerical solution of the compressible nonhydrostatic primitive equations. Turbulence closure is achieved by a conventional first-order diagnostic approximation. Open lateral boundaries are incorporated which minimize wave reflection and which do not induce domain-wide mass trends. Microphysical processes are governed by prognostic equations for potential temperature water vapor, cloud droplets, ice crystals, rain, snow, and hail. Microphysical interactions are computed by numerous Orville-type parameterizations. A diagnostic surface boundary layer is parameterized assuming Monin-Obukhov similarity theory. The governing equation set is approximated on a staggered three-dimensional grid with quadratic-conservative central space differencing. Time differencing is approximated by the second-order Adams-Bashforth method. The vertical grid spacing may be either linear or stretched. The model domain may translate along with a convective cell, even at variable speeds.

Sleep inertia, sleep homeostatic and circadian influences on higher-order cognitive functions.

PubMed

Burke, Tina M; Scheer, Frank A J L; Ronda, Joseph M; Czeisler, Charles A; Wright, Kenneth P

2015-08-01

Sleep inertia, sleep homeostatic and circadian processes modulate cognition, including reaction time, memory, mood and alertness. How these processes influence higher-order cognitive functions is not well known. Six participants completed a 73-day-long study that included two 14-day-long 28-h forced desynchrony protocols to examine separate and interacting influences of sleep inertia, sleep homeostasis and circadian phase on higher-order cognitive functions of inhibitory control and selective visual attention. Cognitive performance for most measures was impaired immediately after scheduled awakening and improved during the first ~2-4 h of wakefulness (decreasing sleep inertia); worsened thereafter until scheduled bedtime (increasing sleep homeostasis); and was worst at ~60° and best at ~240° (circadian modulation, with worst and best phases corresponding to ~09:00 and ~21:00 hours, respectively, in individuals with a habitual wake time of 07:00 hours). The relative influences of sleep inertia, sleep homeostasis and circadian phase depended on the specific higher-order cognitive function task examined. Inhibitory control appeared to be modulated most strongly by circadian phase, whereas selective visual attention for a spatial-configuration search task was modulated most strongly by sleep inertia. These findings demonstrate that some higher-order cognitive processes are differentially sensitive to different sleep-wake regulatory processes. Differential modulation of cognitive functions by different sleep-wake regulatory processes has important implications for understanding mechanisms contributing to performance impairments during adverse circadian phases, sleep deprivation and/or upon awakening from sleep. © 2015 European Sleep Research Society.

Composition and structure of the Chironomidae (Insecta: Diptera) community associated with bryophytes in a first-order stream in the Atlantic forest, Brazil.

PubMed

Rosa, B F J V; Dias-Silva, M V D; Alves, R G

2013-02-01

This study describes the structure of the Chironomidae community associated with bryophytes in a first-order stream located in a biological reserve of the Atlantic Forest, during two seasons. Samples of bryophytes adhered to rocks along a 100-m stretch of the stream were removed with a metal blade, and 200-mL pots were filled with the samples. The numerical density (individuals per gram of dry weight), Shannon's diversity index, Pielou's evenness index, the dominance index (DI), and estimated richness were calculated for each collection period (dry and rainy). Linear regression analysis was employed to test the existence of a correlation between rainfall and the individual's density and richness. The high numerical density and richness of Chironomidae taxa observed are probably related to the peculiar conditions of the bryophyte habitat. The retention of larvae during periods of higher rainfall contributed to the high density and richness of Chironomidae larvae. The rarefaction analysis showed higher richness in the rainy season related to the greater retention of food particles. The data from this study show that bryophytes provide stable habitats for the colonization by and refuge of Chironomidae larvae, mainly under conductions of faster water flow and higher precipitation.

The use of WaveLight® Contoura to create a uniform cornea: the LYRA Protocol. Part 1: the effect of higher-order corneal aberrations on refractive astigmatism

PubMed Central

Motwani, Manoj

2017-01-01

Purpose To demonstrate how higher-order corneal aberrations can cancel out, modify, or induce lower-order corneal astigmatism. Patients and methods Six representative eyes are presented that show different scenarios in which higher-order aberrations interacting with corneal astigmatism can affect the manifest refraction. WaveLight® Contoura ablation maps showing the higher-order aberrations are shown, as are results of correction with full measured correction using the LYRA (Layer Yolked Reduction of Astigmatism) Protocol. Results Higher-order corneal aberrations such as trefoil, quadrafoil, and coma can create ovalization of the central cornea, which can interact with the ovalization caused by lower-order astigmatism to either induce, cancel out, or modify the manifest refraction. Contoura processing successfully determines the linkage of these interactions resulting in full astigmatism removal. Purely lenticular astigmatism appears to be rare, but a case is also demonstrated. The author theorizes that all aberrations require cerebral compensatory processing and can be removed, supported by the facts that full removal of aberrations and its linkage with lower-order astigmatism with the LYRA Protocol has not resulted in worse or unacceptable vision for any patients. Conclusion Higher-order aberrations interacting with lower-order astigmatism is the main reason for the differences between manifest refraction and Contoura measured astigmatism, and the linkage between these interactions can be successfully treated using Contoura and the LYRA Protocol. Lenticular astigmatism is relatively rare. PMID:28553069

The use of WaveLight® Contoura to create a uniform cornea: the LYRA Protocol. Part 1: the effect of higher-order corneal aberrations on refractive astigmatism.

PubMed

Motwani, Manoj

2017-01-01

To demonstrate how higher-order corneal aberrations can cancel out, modify, or induce lower-order corneal astigmatism. Six representative eyes are presented that show different scenarios in which higher-order aberrations interacting with corneal astigmatism can affect the manifest refraction. WaveLight ® Contoura ablation maps showing the higher-order aberrations are shown, as are results of correction with full measured correction using the LYRA (Layer Yolked Reduction of Astigmatism) Protocol. Higher-order corneal aberrations such as trefoil, quadrafoil, and coma can create ovalization of the central cornea, which can interact with the ovalization caused by lower-order astigmatism to either induce, cancel out, or modify the manifest refraction. Contoura processing successfully determines the linkage of these interactions resulting in full astigmatism removal. Purely lenticular astigmatism appears to be rare, but a case is also demonstrated. The author theorizes that all aberrations require cerebral compensatory processing and can be removed, supported by the facts that full removal of aberrations and its linkage with lower-order astigmatism with the LYRA Protocol has not resulted in worse or unacceptable vision for any patients. Higher-order aberrations interacting with lower-order astigmatism is the main reason for the differences between manifest refraction and Contoura measured astigmatism, and the linkage between these interactions can be successfully treated using Contoura and the LYRA Protocol. Lenticular astigmatism is relatively rare.

SCL-90-R emotional distress ratings in substance use and impulse control disorders: One-factor, oblique first-order, higher-order, and bi-factor models compared.

PubMed

Arrindell, Willem A; Urbán, Róbert; Carrozzino, Danilo; Bech, Per; Demetrovics, Zsolt; Roozen, Hendrik G

2017-09-01

To fully understand the dimensionality of an instrument in a certain population, rival bi-factor models should be routinely examined and tested against oblique first-order and higher-order structures. The present study is among the very few studies that have carried out such a comparison in relation to the Symptom Checklist-90-R. In doing so, it utilized a sample comprising 2593 patients with substance use and impulse control disorders. The study also included a test of a one-dimensional model of general psychological distress. Oblique first-order factors were based on the original a priori 9-dimensional model advanced by Derogatis (1977); and on an 8-dimensional model proposed by Arrindell and Ettema (2003)-Agoraphobia, Anxiety, Depression, Somatization, Cognitive-performance deficits, Interpersonal sensitivity and mistrust, Acting-out hostility, and Sleep difficulties. Taking individual symptoms as input, three higher-order models were tested with at the second-order levels either (1) General psychological distress; (2) 'Panic with agoraphobia', 'Depression' and 'Extra-punitive behavior'; or (3) 'Irritable-hostile depression' and 'Panic with agoraphobia'. In line with previous studies, no support was found for the one-factor model. Bi-factor models were found to fit the dataset best relative to the oblique first-order and higher-order models. However, oblique first-order and higher-order factor models also fit the data fairly well in absolute terms. Higher-order solution (2) provided support for R.F. Krueger's empirical model of psychopathology which distinguishes between fear, distress, and externalizing factors (Krueger, 1999). The higher-order model (3), which combines externalizing and distress factors (Irritable-hostile depression), fit the data numerically equally well. Overall, findings were interpreted as supporting the hypothesis that the prevalent forms of symptomatology addressed have both important common and unique features. Proposals were made to improve the Depression subscale as its scores represent more of a very common construct as is measured with the severity (total) scale than of a specific measure that purports to measure what it should assess-symptoms of depression. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

International Conference on Numerical Methods in Fluid Dynamics, 7th, Stanford University, Stanford and Moffett Field, CA, June 23-27, 1980, Proceedings

NASA Technical Reports Server (NTRS)

Reynolds, W. C. (Editor); Maccormack, R. W.

1981-01-01

Topics discussed include polygon transformations in fluid mechanics, computation of three-dimensional horseshoe vortex flow using the Navier-Stokes equations, an improved surface velocity method for transonic finite-volume solutions, transonic flow calculations with higher order finite elements, the numerical calculation of transonic axial turbomachinery flows, and the simultaneous solutions of inviscid flow and boundary layer at transonic speeds. Also considered are analytical solutions for the reflection of unsteady shock waves and relevant numerical tests, reformulation of the method of characteristics for multidimensional flows, direct numerical simulations of turbulent shear flows, the stability and separation of freely interacting boundary layers, computational models of convective motions at fluid interfaces, viscous transonic flow over airfoils, and mixed spectral/finite difference approximations for slightly viscous flows.

Investigation of Grating-Assisted Trimodal Interferometer Biosensors Based on a Polymer Platform.

PubMed

Liang, Yuxin; Zhao, Mingshan; Wu, Zhenlin; Morthier, Geert

2018-05-10

A grating-assisted trimodal interferometer biosensor is proposed and numerically analyzed. A long period grating coupler, for adjusting the power between the fundamental mode and the second higher order mode, is investigated, and is shown to act as a conventional directional coupler for adjusting the power between the two arms. The trimodal interferometer can achieve maximal fringe visibility when the powers of the two modes are adjusted to the same value by the grating coupler, which means that a better limit of detection can be expected. In addition, the second higher order mode typically has a larger evanescent tail than the first higher order mode in bimodal interferometers, resulting in a higher sensitivity of the trimodal interferometer. The influence of fabrication tolerances on the performance of the designed interferometer is also investigated. The power difference between the two modes shows inertia to the fill factor of the grating, but high sensitivity to the modulation depth. Finally, a 2050 2π/RIU (refractive index unit) sensitivity and 43 dB extinction ratio of the output power are achieved.

Dynamical analysis of continuous higher-order hopfield networks for combinatorial optimization.

PubMed

Atencia, Miguel; Joya, Gonzalo; Sandoval, Francisco

2005-08-01

In this letter, the ability of higher-order Hopfield networks to solve combinatorial optimization problems is assessed by means of a rigorous analysis of their properties. The stability of the continuous network is almost completely clarified: (1) hyperbolic interior equilibria, which are unfeasible, are unstable; (2) the state cannot escape from the unitary hypercube; and (3) a Lyapunov function exists. Numerical methods used to implement the continuous equation on a computer should be designed with the aim of preserving these favorable properties. The case of nonhyperbolic fixed points, which occur when the Hessian of the target function is the null matrix, requires further study. We prove that these nonhyperbolic interior fixed points are unstable in networks with three neurons and order two. The conjecture that interior equilibria are unstable in the general case is left open.

Computerized implementation of higher-order electron-correlation methods and their linear-scaling divide-and-conquer extensions.

PubMed

Nakano, Masahiko; Yoshikawa, Takeshi; Hirata, So; Seino, Junji; Nakai, Hiromi

2017-11-05

We have implemented a linear-scaling divide-and-conquer (DC)-based higher-order coupled-cluster (CC) and Møller-Plesset perturbation theories (MPPT) as well as their combinations automatically by means of the tensor contraction engine, which is a computerized symbolic algebra system. The DC-based energy expressions of the standard CC and MPPT methods and the CC methods augmented with a perturbation correction were proposed for up to high excitation orders [e.g., CCSDTQ, MP4, and CCSD(2) TQ ]. The numerical assessment for hydrogen halide chains, polyene chains, and first coordination sphere (C1) model of photoactive yellow protein has revealed that the DC-based correlation methods provide reliable correlation energies with significantly less computational cost than that of the conventional implementations. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Human Expert Labeling Process (HELP): Towards a Reliable Higher-Order User State Labeling Process and Tool to Assess Student Engagement

ERIC Educational Resources Information Center

Aslan, Sinem; Mete, Sinem Emine; Okur, Eda; Oktay, Ece; Alyuz, Nese; Genc, Utku Ergin; Stanhill, David; Esme, Asli Arslan

2017-01-01

In a series of longitudinal research studies, researchers at Intel Corporation in Turkey have been working towards an adaptive learning system automatically detecting student engagement as a higher-order user state in real-time. The labeled data necessary for supervised learning can be obtained through labeling conducted by human experts. Using…

A comparison of zero-order, first-order, and monod biotransformation models

USGS Publications Warehouse

Bekins, B.A.; Warren, E.; Godsy, E.M.

1998-01-01

Under some conditions, a first-order kinetic model is a poor representation of biodegradation in contaminated aquifers. Although it is well known that the assumption of first-order kinetics is valid only when substrate concentration, S, is much less than the half-saturation constant, K(s), this assumption is often made without verification of this condition. We present a formal error analysis showing that the relative error in the first-order approximation is S/K(S) and in the zero-order approximation the error is K(s)/S. We then examine the problems that arise when the first-order approximation is used outside the range for which it is valid. A series of numerical simulations comparing results of first- and zero-order rate approximations to Monod kinetics for a real data set illustrates that if concentrations observed in the field are higher than K(s), it may better to model degradation using a zero-order rate expression. Compared with Monod kinetics, extrapolation of a first-order rate to lower concentrations under-predicts the biotransformation potential, while extrapolation to higher concentrations may grossly over-predict the transformation rate. A summary of solubilities and Monod parameters for aerobic benzene, toluene, and xylene (BTX) degradation shows that the a priori assumption of first-order degradation kinetics at sites contaminated with these compounds is not valid. In particular, out of six published values of KS for toluene, only one is greater than 2 mg/L, indicating that when toluene is present in concentrations greater than about a part per million, the assumption of first-order kinetics may be invalid. Finally, we apply an existing analytical solution for steady-state one-dimensional advective transport with Monod degradation kinetics to a field data set.A formal error analysis is presented showing that the relative error in the first-order approximation is S/KS and in the zero-order approximation the error is KS/S where S is the substrate concentration and KS is the half-saturation constant. The problems that arise when the first-order approximation is used outside the range for which it is valid are examined. A series of numerical simulations comparing results of first- and zero-order rate approximations to Monod kinetics for a real data set illustrates that if concentrations observed in the field are higher than KS, it may be better to model degradation using a zero-order rate expression.

On the Stability of Jump-Linear Systems Driven by Finite-State Machines with Markovian Inputs

NASA Technical Reports Server (NTRS)

Patilkulkarni, Sudarshan; Herencia-Zapana, Heber; Gray, W. Steven; Gonzalez, Oscar R.

2004-01-01

This paper presents two mean-square stability tests for a jump-linear system driven by a finite-state machine with a first-order Markovian input process. The first test is based on conventional Markov jump-linear theory and avoids the use of any higher-order statistics. The second test is developed directly using the higher-order statistics of the machine s output process. The two approaches are illustrated with a simple model for a recoverable computer control system.

Evaluation of Fracture Initiation in the Mannesmann Piercing Process

NASA Astrophysics Data System (ADS)

Fanini, S.; Ghiotti, A.; Bruschi, S.

2007-04-01

One of the challenging objectives in studying the Mannesmann piercing process is to predict the fracture initiation, known as "Mannesmann effect", in order to design and optimize the working parameters of the piercing process. The objective of the paper is to investigate the workability of a tube steel tested in the same conditions of the Mannesman piercing process. The stress and strain states as well as temperature fields arising during the process are identified through numerical simulations. The hot tensile test is chosen for fundamental studies on fracture initiation, as a tensile state of stress in the centre of the billet in the first stages of the piercing process before the plug arrival seems to be one of the main causes of the crack initiation. The material constants of energy-based models implemented in FEM codes are calculated and numerical results are compared with non-plug piercing tests carried out on the industrial plant.

Neurobiological roots of language in primate audition: common computational properties.

PubMed

Bornkessel-Schlesewsky, Ina; Schlesewsky, Matthias; Small, Steven L; Rauschecker, Josef P

2015-03-01

Here, we present a new perspective on an old question: how does the neurobiology of human language relate to brain systems in nonhuman primates? We argue that higher-order language combinatorics, including sentence and discourse processing, can be situated in a unified, cross-species dorsal-ventral streams architecture for higher auditory processing, and that the functions of the dorsal and ventral streams in higher-order language processing can be grounded in their respective computational properties in primate audition. This view challenges an assumption, common in the cognitive sciences, that a nonhuman primate model forms an inherently inadequate basis for modeling higher-level language functions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Three Dimensional Forming Simulation of the Shielded Slot Plate for the MCFC Using a Ductile Fracture Criterion

NASA Astrophysics Data System (ADS)

Lee, C. H.; Yang, D. Y.; Lee, S. R.; Chang, I. G.; Lee, T. W.

2011-08-01

The shielded slot plate, which has a sheared corrugated trapezoidal pattern, is a component of the metallic bipolar plate for the molten carbonate fuel cell (MCFC). In order to increase the efficiency of the fuel cell, the unit cell of the shielded slot plate should have a relatively large upper area. Additionally, defects from the forming process should be minimized. In order to simulate the slitting process, whereby sheared corrugated patterns are formed, ductile fracture criteria based on the histories of stress and strain are employed. The user material subroutine VUMAT is employed for implementation of the material and ductile fracture criteria in the commercial FEM software ABAQUS. The variables of the ductile fracture criteria were determined by comparing the simulation results and the experimental results of the tension test and the shearing test. Parametric studies were conducted to determine the critical value of the ductile fracture criterion. Employing these ductile fracture criteria, the three dimensional forming process of the shielded slot plate was numerically simulated. The effects of the slitting process in the forming process of the shielded slot plate were analyzed through a FEM simulation and experimental studies. Finally, experiments involving microscopic and macroscopic observations were conducted to verify the numerical simulations of the 3-step forming process.

Propagation effects in the generation process of high-order vortex harmonics.

PubMed

Zhang, Chaojin; Wu, Erheng; Gu, Mingliang; Liu, Chengpu

2017-09-04

We numerically study the propagation of a Laguerre-Gaussian beam through polar molecular media via the exact solution of full-wave Maxwell-Bloch equations where the rotating-wave and slowly-varying-envelope approximations are not included. It is found that beyond the coexistence of odd-order and even-order vortex harmonics due to inversion asymmetry of the system, the light propagation effect results in the intensity enhancement of a high-order vortex harmonics. Moreover, the orbital momentum successfully transfers from the fundamental laser driver to the vortex harmonics which topological charger number is directly proportional to its order.

48 CFR 204.7007 - Order of application for modifications.

Code of Federal Regulations, 2012 CFR

2012-10-01

... numeric order of the modifications to a contract is not the order in which the changes to the contract... modifications will be applied in numeric order, followed by contract administration office modifications in numeric order. [77 FR 30368, May 22, 2012] ...

48 CFR 204.7007 - Order of application for modifications.

Code of Federal Regulations, 2014 CFR

2014-10-01

... numeric order of the modifications to a contract is not the order in which the changes to the contract... modifications will be applied in numeric order, followed by contract administration office modifications in numeric order. [77 FR 30368, May 22, 2012] ...

48 CFR 204.7007 - Order of application for modifications.

Code of Federal Regulations, 2013 CFR

2013-10-01

... numeric order of the modifications to a contract is not the order in which the changes to the contract... modifications will be applied in numeric order, followed by contract administration office modifications in numeric order. [77 FR 30368, May 22, 2012] ...

Numerical modelling of hydrologically-driven slope instability by means of porous media mechanics

NASA Astrophysics Data System (ADS)

Kakogiannou, Evanthia; Sanavia, Lorenzo; Lora, Marco; Schrefler, Bernhard

2015-04-01

Heavy rainfall can trigger slope failure which generally involves shallow soil deposit of different grading and origin usually in a state of partial saturation. In this case of slope instability, the behaviour of the soil slope is closely related not only to the distribution of pore-water pressure but also to the stress state during rainfall infiltration involving both mechanical and hydrological processes. In order to understand better these physical key processes, in this research work, the modelling of rainfall induced slope failure is considered as a coupled variably saturated hydro-mechanical problem. Therefore, the geometrically linear finite element code Comes-Geo for non-isothermal elasto-plastic multiphase solid porous materials is used, as developed by B.A. Schrefler and his co-workers. In this context, a detailed numerical analysis of an experimental slope stability test due to rainfall infiltration is presented. The main goals of this work are to understand the triggering mechanisms during the progressive failure, the effect of using different constitutive models of the mechanical soil behavior on the numerical results and the use of the second order work criterion on the detection of slope instability.

Material flow data for numerical simulation of powder injection molding

NASA Astrophysics Data System (ADS)

Duretek, I.; Holzer, C.

2017-01-01

The powder injection molding (PIM) process is a cost efficient and important net-shape manufacturing process that is not completely understood. For the application of simulation programs for the powder injection molding process, apart from suitable physical models, exact material data and in particular knowledge of the flow behavior are essential in order to get precise numerical results. The flow processes of highly filled polymers are complex. Occurring effects are very hard to separate, like shear flow with yield stress, wall slip, elastic effects, etc. Furthermore, the occurrence of phase separation due to the multi-phase composition of compounds is quite probable. In this work, the flow behavior of a 316L stainless steel feedstock for powder injection molding was investigated. Additionally, the influence of pre-shearing on the flow behavior of PIM-feedstocks under practical conditions was examined and evaluated by a special PIM injection molding machine rheometer. In order to have a better understanding of key factors of PIM during the injection step, 3D non-isothermal numerical simulations were conducted with a commercial injection molding simulation software using experimental feedstock properties. The simulation results were compared with the experimental results. The mold filling studies amply illustrate the effect of mold temperature on the filling behavior during the mold filling stage. Moreover, the rheological measurements showed that at low shear rates no zero shear viscosity was observed, but instead the viscosity further increased strongly. This flow behavior could be described with the Cross-WLF approach with Herschel-Bulkley extension very well.

Moderate anxiety modifies the electromyographic activity of a forearm muscle during a time-reaction task in women.

PubMed

Langlet, C; Hainaut, J P; Bolmont, B

2017-03-16

Arousal anxiety has a great impact on reaction time, physiological parameters and motor performance. Numerous studies have focused on the influence of anxiety on muscular activity during simple non ecologic task. We investigate the impact of a moderate state-anxiety (arousal stressor) on the specific component of a complex multi-joint ecologic movement during a reaction time task of auditory stimulus-response. Our objective is to know if central and peripheral voluntary motor processes were modulated in the same way by an arousal stressor. Eighteen women volunteers performed simple reaction time tasks of auditory stimulus-response. Video-recorded Stroop test with interferences was used to induced moderate state-anxiety. Electromyographic activity of the wrist extensor was recorded in order to analyse the two components of the reaction time: the premotor and motor time. In anxiogenic condition, an acceleration and an increase of muscular activity of the reaction time was obtained. This increase was due to a stronger muscle activity during the premotor time in the anxiogenic condition. Arousal anxiety has a different impact on central and peripheral voluntary motor processes. The modifications observed could be related to an increase in arousal related to a higher anxiety in order to prepare the body to act. Copyright © 2017 Elsevier B.V. All rights reserved.

Measurements of shock-induced guided and surface acoustic waves along boreholes in poroelastic materials

NASA Astrophysics Data System (ADS)

Chao, Gabriel; Smeulders, D. M. J.; van Dongen, M. E. H.

2006-05-01

Acoustic experiments on the propagation of guided waves along water-filled boreholes in water-saturated porous materials are reported. The experiments were conducted using a shock tube technique. An acoustic funnel structure was placed inside the tube just above the sample in order to enhance the excitation of the surface modes. A fast Fourier transform-Prony-spectral ratio method is implemented to transform the data from the time-space domain to the frequency-wave-number domain. Frequency-dependent phase velocities and attenuation coefficients were measured using this technique. The results for a Berea sandstone material show a clear excitation of the fundamental surface mode, the pseudo-Stoneley wave. The comparison of the experimental results with numerical predictions based on Biot's theory of poromechanics [J. Acoust. Soc. Am. 28, 168 (1956)], shows that the oscillating fluid flow at the borehole wall is the dominant loss mechanism governing the pseudo-Stoneley wave and it is properly described by the Biot's model at frequencies below 40 kHz. At higher frequencies, a systematic underestimation of the theoretical predictions is found, which can be attributed to the existence of other losses mechanisms neglected in the Biot formulation. Higher-order guided modes associated with the compressional wave in the porous formation and the cylindrical geometry of the shock tube were excited, and detailed information was obtained on the frequency-dependent phase velocity and attenuation in highly porous and permeable materials. The measured attenuation of the guided wave associated with the compressional wave reveals the presence of regular oscillatory patterns that can be attributed to radial resonances. This oscillatory behavior is also numerically predicted, although the measured attenuation values are one order of magnitude higher than the corresponding theoretical values. The phase velocities of the higher-order modes are generally well predicted by theory.

Toward a Comprehensive Understanding of Executive Cognitive Function in Implicit Racial Bias

PubMed Central

Ito, Tiffany A.; Friedman, Naomi P.; Bartholow, Bruce D.; Correll, Joshua; Loersch, Chris; Altamirano, Lee J.; Miyake, Akira

2014-01-01

Although performance on laboratory-based implicit bias tasks often is interpreted strictly in terms of the strength of automatic associations, recent evidence suggests that such tasks are influenced by higher-order cognitive control processes, so-called executive functions (EFs). However, extant work in this area has been limited by failure to account for the unity and diversity of EFs, focus on only a single measure of bias and/or EF, and relatively small sample sizes. The current study sought to comprehensively model the relation between individual differences in EFs and the expression of racial bias in three commonly used laboratory measures. Participants (N=485) completed a battery of EF tasks (session 1) and three racial bias tasks (session 2), along with numerous individual difference questionnaires. The main findings were as follows: (1) measures of implicit bias were only weakly intercorrelated; (2) EF and estimates of automatic processes both predicted implicit bias and also interacted, such that the relation between automatic processes and bias expression was reduced at higher levels of EF; (3) specific facets of EF were differentially associated with overall task performance and controlled processing estimates across different bias tasks; (4) EF did not moderate associations between implicit and explicit measures of bias; and (5) external, but not internal, motivation to control prejudice depended on EF to reduce bias expression. Findings are discussed in terms of the importance of global and specific EF abilities in determining expression of implicit racial bias. PMID:25603372

Phase ordering in disordered and inhomogeneous systems

NASA Astrophysics Data System (ADS)

Corberi, Federico; Zannetti, Marco; Lippiello, Eugenio; Burioni, Raffaella; Vezzani, Alessandro

2015-06-01

We study numerically the coarsening dynamics of the Ising model on a regular lattice with random bonds and on deterministic fractal substrates. We propose a unifying interpretation of the phase-ordering processes based on two classes of dynamical behaviors characterized by different growth laws of the ordered domain size, namely logarithmic or power law, respectively. It is conjectured that the interplay between these dynamical classes is regulated by the same topological feature that governs the presence or the absence of a finite-temperature phase transition.

Preconditioning for the Navier-Stokes equations with finite-rate chemistry

NASA Technical Reports Server (NTRS)

Godfrey, Andrew G.; Walters, Robert W.; Van Leer, Bram

1993-01-01

The preconditioning procedure for generalized finite-rate chemistry and the proper preconditioning for the one-dimensional Navier-Stokes equations are presented. Eigenvalue stiffness is resolved and convergence-rate acceleration is demonstrated over the entire Mach-number range from the incompressible to the hypersonic. Specific benefits are realized at low and transonic flow speeds. The extended preconditioning matrix accounts for thermal and chemical non-equilibrium and its implementation is explained for both explicit and implicit time marching. The effect of higher-order spatial accuracy and various flux splittings is investigated. Numerical analysis reveals the possible theoretical improvements from using proconditioning at all Mach numbers. Numerical results confirm the expectations from the numerical analysis. Representative test cases include flows with previously troublesome embedded high-condition-number regions.

Generalized Gibbs state with modified Redfield solution: Exact agreement up to second order

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thingna, Juzar; Wang, Jian-Sheng; Haenggi, Peter

A novel scheme for the steady state solution of the standard Redfield quantum master equation is developed which yields agreement with the exact result for the corresponding reduced density matrix up to second order in the system-bath coupling strength. We achieve this objective by use of an analytic continuation of the off-diagonal matrix elements of the Redfield solution towards its diagonal limit. Notably, our scheme does not require the provision of yet higher order relaxation tensors. Testing this modified method for a heat bath consisting of a collection of harmonic oscillators we assess that the system relaxes towards its correctmore » coupling-dependent, generalized quantum Gibbs state in second order. We numerically compare our formulation for a damped quantum harmonic system with the nonequilibrium Green's function formalism: we find good agreement at low temperatures for coupling strengths that are even larger than expected from the very regime of validity of the second-order Redfield quantum master equation. Yet another advantage of our method is that it markedly reduces the numerical complexity of the problem; thus, allowing to study efficiently large-sized system Hilbert spaces.« less

Strong plasmonic enhancement of biexciton emission: controlled coupling of a single quantum dot to a gold nanocone antenna

DOE PAGES

Matsuzaki, Korenobu; Vassant, Simon; Liu, Hsuan-Wei; ...

2017-02-14

Multiexcitonic transitions and emission of several photons per excitation comprise a very attractive feature of semiconductor quantum dots for optoelectronics applications. However, these higher-order radiative processes are usually quenched in colloidal quantum dots by Auger and other nonradiative decay channels. To increase the multiexcitonic quantum efficiency, several groups have explored plasmonic enhancement, so far with moderate results. By controlled positioning of individual quantum dots in the near field of gold nanocone antennas, we enhance the radiative decay rates of monoexcitons and biexcitons by 109 and 100 folds at quantum efficiencies of 60 and 70%, respectively, in very good agreement withmore » the outcome of numerical calculations. We discuss the implications of our work for future fundamental and applied research in nano-optics.« less

MLFMA-accelerated Nyström method for ultrasonic scattering - Numerical results and experimental validation

NASA Astrophysics Data System (ADS)

Gurrala, Praveen; Downs, Andrew; Chen, Kun; Song, Jiming; Roberts, Ron

2018-04-01

Full wave scattering models for ultrasonic waves are necessary for the accurate prediction of voltage signals received from complex defects/flaws in practical nondestructive evaluation (NDE) measurements. We propose the high-order Nyström method accelerated by the multilevel fast multipole algorithm (MLFMA) as an improvement to the state-of-the-art full-wave scattering models that are based on boundary integral equations. We present numerical results demonstrating improvements in simulation time and memory requirement. Particularly, we demonstrate the need for higher order geom-etry and field approximation in modeling NDE measurements. Also, we illustrate the importance of full-wave scattering models using experimental pulse-echo data from a spherical inclusion in a solid, which cannot be modeled accurately by approximation-based scattering models such as the Kirchhoff approximation.

How Math Anxiety Relates to Number-Space Associations.

PubMed

Georges, Carrie; Hoffmann, Danielle; Schiltz, Christine

2016-01-01

Given the considerable prevalence of math anxiety, it is important to identify the factors contributing to it in order to improve mathematical learning. Research on math anxiety typically focusses on the effects of more complex arithmetic skills. Recent evidence, however, suggests that deficits in basic numerical processing and spatial skills also constitute potential risk factors of math anxiety. Given these observations, we determined whether math anxiety also depends on the quality of spatial-numerical associations. Behavioral evidence for a tight link between numerical and spatial representations is given by the SNARC (spatial-numerical association of response codes) effect, characterized by faster left-/right-sided responses for small/large digits respectively in binary classification tasks. We compared the strength of the SNARC effect between high and low math anxious individuals using the classical parity judgment task in addition to evaluating their spatial skills, arithmetic performance, working memory and inhibitory control. Greater math anxiety was significantly associated with stronger spatio-numerical interactions. This finding adds to the recent evidence supporting a link between math anxiety and basic numerical abilities and strengthens the idea that certain characteristics of low-level number processing such as stronger number-space associations constitute a potential risk factor of math anxiety.

How Math Anxiety Relates to Number–Space Associations

PubMed Central

Georges, Carrie; Hoffmann, Danielle; Schiltz, Christine

2016-01-01

Given the considerable prevalence of math anxiety, it is important to identify the factors contributing to it in order to improve mathematical learning. Research on math anxiety typically focusses on the effects of more complex arithmetic skills. Recent evidence, however, suggests that deficits in basic numerical processing and spatial skills also constitute potential risk factors of math anxiety. Given these observations, we determined whether math anxiety also depends on the quality of spatial-numerical associations. Behavioral evidence for a tight link between numerical and spatial representations is given by the SNARC (spatial-numerical association of response codes) effect, characterized by faster left-/right-sided responses for small/large digits respectively in binary classification tasks. We compared the strength of the SNARC effect between high and low math anxious individuals using the classical parity judgment task in addition to evaluating their spatial skills, arithmetic performance, working memory and inhibitory control. Greater math anxiety was significantly associated with stronger spatio-numerical interactions. This finding adds to the recent evidence supporting a link between math anxiety and basic numerical abilities and strengthens the idea that certain characteristics of low-level number processing such as stronger number–space associations constitute a potential risk factor of math anxiety. PMID:27683570

Enzymatic induction of supramolecular order and bioactivity

NASA Astrophysics Data System (ADS)

Yang, Chengbiao; Ren, Xinrui; Ding, Dan; Wang, Ling; Yang, Zhimou

2016-05-01

We showed in this study that enzymatic triggering is a totally different pathway for the preparation of self-assembling nanomaterials to the heating-cooling process. Because the molecules were under lower energy levels and the molecular conformation was more ordered during the enzymatic triggeration under mild conditions, nanomaterials with higher supramolecular order could be obtained through biocatalytic control. In this study, nanoparticles were obtained by an enzymatic reaction and nanofibers were observed through the heating-cooling process. We observed a distinct trough at 318 nm from the CD spectrum of a particle sample but not a fiber sample, suggesting the long range arrangement of molecules and helicity in the nanoparticles. The nanoparticles with higher supramolecular order possessed much better potency as a protein vaccine adjuvant because it accelerated the DC maturation and elicited stronger T-cells cytokine production than the nanofibers. Our study demonstrated that biocatalytic triggering is a useful method for preparing supramolecular nanomaterials with higher supramolecular order and probably better bioactivity.We showed in this study that enzymatic triggering is a totally different pathway for the preparation of self-assembling nanomaterials to the heating-cooling process. Because the molecules were under lower energy levels and the molecular conformation was more ordered during the enzymatic triggeration under mild conditions, nanomaterials with higher supramolecular order could be obtained through biocatalytic control. In this study, nanoparticles were obtained by an enzymatic reaction and nanofibers were observed through the heating-cooling process. We observed a distinct trough at 318 nm from the CD spectrum of a particle sample but not a fiber sample, suggesting the long range arrangement of molecules and helicity in the nanoparticles. The nanoparticles with higher supramolecular order possessed much better potency as a protein vaccine adjuvant because it accelerated the DC maturation and elicited stronger T-cells cytokine production than the nanofibers. Our study demonstrated that biocatalytic triggering is a useful method for preparing supramolecular nanomaterials with higher supramolecular order and probably better bioactivity. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02330d

College Admissions Viewbooks and the Grammar of Gender, Race, and STEM

ERIC Educational Resources Information Center

Osei-Kofi, Nana; Torres, Lisette E.

2015-01-01

Numerous reports on the US economy argue that American higher education institutions must prepare a greater number of workers for employment in science, technology, engineering, and math (STEM), in order for the US to remain globally competitive. To do so, addressing the underrepresentation of women and people of color who pursue degrees in STEM…

COED Transactions, Vol. IX, No. 2, February 1977. Prism: An Educational Aide to Symbolic Differentiation and Simplification of Algebraic Expressions.

ERIC Educational Resources Information Center

Marcovitz, Alan B., Ed.

A computer program for numeric and symbolic manipulation and the methodology underlying its development are presented. Some features of the program are: an option for implied multiplication; computation of higher-order derivatives; differentiation of 26 different trigonometric, hyperbolic, inverse trigonometric, and inverse hyperbolic functions;…

On the ordinality of numbers: A review of neural and behavioral studies.

PubMed

Lyons, I M; Vogel, S E; Ansari, D

2016-01-01

The last several years have seen steady growth in research on the cognitive and neuronal mechanisms underlying how numbers are represented as part of ordered sequences. In the present review, we synthesize what is currently known about numerical ordinality from behavioral and neuroimaging research, point out major gaps in our current knowledge, and propose several hypotheses that may bear further investigation. Evidence suggests that how we process ordinality differs from how we process cardinality, but that this difference depends strongly on context-in particular, whether numbers are presented symbolically or nonsymbolically. Results also reveal many commonalities between numerical and nonnumerical ordinal processing; however, the degree to which numerical ordinality can be reduced to domain-general mechanisms remains unclear. One proposal is that numerical ordinality relies upon more general short-term memory mechanisms as well as more numerically specific long-term memory representations. It is also evident that numerical ordinality is highly multifaceted, with symbolic representations in particular allowing for a wide range of different types of ordinal relations, the complexity of which appears to increase over development. We examine the proposal that these relations may form the basis of a richer set of associations that may prove crucial to the emergence of more complex math abilities and concepts. In sum, ordinality appears to be an important and relatively understudied facet of numerical cognition that presents substantial opportunities for new and ground-breaking research. © 2016 Elsevier B.V. All rights reserved.

Low Order Modeling Tools for Preliminary Pressure Gain Combustion Benefits Analyses

NASA Technical Reports Server (NTRS)

Paxson, Daniel E.

2012-01-01

Pressure gain combustion (PGC) offers the promise of higher thermodynamic cycle efficiency and greater specific power in propulsion and power systems. This presentation describes a model, developed under a cooperative agreement between NASA and AFRL, for preliminarily assessing the performance enhancement and preliminary size requirements of PGC components either as stand-alone thrust producers or coupled with surrounding turbomachinery. The model is implemented in the Numerical Propulsion Simulation System (NPSS) environment allowing various configurations to be examined at numerous operating points. The validated model is simple, yet physics-based. It executes quickly in NPSS, yet produces realistic results.

Spacecraft Charging Calculations: NASCAP-2K and SEE Spacecraft Charging Handbook

NASA Technical Reports Server (NTRS)

Davis, V. A.; Neergaard, L. F.; Mandell, M. J.; Katz, I.; Gardner, B. M.; Hilton, J. M.; Minor, J.

2002-01-01

For fifteen years NASA and the Air Force Charging Analyzer Program for Geosynchronous Orbits (NASCAP/GEO) has been the workhorse of spacecraft charging calculations. Two new tools, the Space Environment and Effects (SEE) Spacecraft Charging Handbook (recently released), and Nascap-2K (under development), use improved numeric techniques and modern user interfaces to tackle the same problem. The SEE Spacecraft Charging Handbook provides first-order, lower-resolution solutions while Nascap-2K provides higher resolution results appropriate for detailed analysis. This paper illustrates how the improvements in the numeric techniques affect the results.

Numerical Schemes for the Hamilton-Jacobi and Level Set Equations on Triangulated Domains

NASA Technical Reports Server (NTRS)

Barth, Timothy J.; Sethian, James A.

2006-01-01

Borrowing from techniques developed for conservation law equations, we have developed both monotone and higher order accurate numerical schemes which discretize the Hamilton-Jacobi and level set equations on triangulated domains. The use of unstructured meshes containing triangles (2D) and tetrahedra (3D) easily accommodates mesh adaptation to resolve disparate level set feature scales with a minimal number of solution unknowns. The minisymposium talk will discuss these algorithmic developments and present sample calculations using our adaptive triangulation algorithm applied to various moving interface problems such as etching, deposition, and curvature flow.

Second-order shaped pulsed for solid-state quantum computation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sengupta, Pinaki

2008-01-01

We present the construction and detailed analysis of highly optimized self-refocusing pulse shapes for several rotation angles. We characterize the constructed pulses by the coefficients appearing in the Magnus expansion up to second order. This allows a semianalytical analysis of the performance of the constructed shapes in sequences and composite pulses by computing the corresponding leading-order error operators. Higher orders can be analyzed with the numerical technique suggested by us previously. We illustrate the technique by analyzing several composite pulses designed to protect against pulse amplitude errors, and on decoupling sequences for potentially long chains of qubits with on-site andmore » nearest-neighbor couplings.« less

Numerical investigation of cryogen re-gasification in a plate heat exchanger

NASA Astrophysics Data System (ADS)

Malecha, Ziemowit; Płuszka, Paweł; Brenk, Arkadiusz

2017-12-01

The efficient re-gasification of cryogen is a crucial process in many cryogenic installations. It is especially important in the case of LNG evaporators used in stationary and mobile applications (e.g. marine and land transport). Other gases, like nitrogen or argon can be obtained at highest purity after re-gasification from their liquid states. Plate heat exchangers (PHE) are characterized by a high efficiency. Application of PHE for liquid gas vaporization processes can be beneficial. PHE design and optimization can be significantly supported by numerical modelling. Such calculations are very challenging due to very high computational demands and complexity related to phase change modelling. In the present work, a simplified mathematical model of a two phase flow with phase change was introduced. To ensure fast calculations a simplified two-dimensional (2D) numerical model of a real PHE was developed. It was validated with experimental measurements and finally used for LNG re-gasification modelling. The proposed numerical model showed to be orders of magnitude faster than its full 3D original.

tran-SAS v1.0: a numerical model to compute catchment-scale hydrologic transport using StorAge Selection functions

NASA Astrophysics Data System (ADS)

Benettin, Paolo; Bertuzzo, Enrico

2018-04-01

This paper presents the tran-SAS package, which includes a set of codes to model solute transport and water residence times through a hydrological system. The model is based on a catchment-scale approach that aims at reproducing the integrated response of the system at one of its outlets. The codes are implemented in MATLAB and are meant to be easy to edit, so that users with minimal programming knowledge can adapt them to the desired application. The problem of large-scale solute transport has both theoretical and practical implications. On the one side, the ability to represent the ensemble of water flow trajectories through a heterogeneous system helps unraveling streamflow generation processes and allows us to make inferences on plant-water interactions. On the other side, transport models are a practical tool that can be used to estimate the persistence of solutes in the environment. The core of the package is based on the implementation of an age master equation (ME), which is solved using general StorAge Selection (SAS) functions. The age ME is first converted into a set of ordinary differential equations, each addressing the transport of an individual precipitation input through the catchment, and then it is discretized using an explicit numerical scheme. Results show that the implementation is efficient and allows the model to run in short times. The numerical accuracy is critically evaluated and it is shown to be satisfactory in most cases of hydrologic interest. Additionally, a higher-order implementation is provided within the package to evaluate and, if necessary, to improve the numerical accuracy of the results. The codes can be used to model streamflow age and solute concentration, but a number of additional outputs can be obtained by editing the codes to further advance the ability to understand and model catchment transport processes.

Adolescents with Developmental Dyscalculia Do Not Have a Generalized Magnitude Deficit - Processing of Discrete and Continuous Magnitudes.

PubMed

McCaskey, Ursina; von Aster, Michael; O'Gorman Tuura, Ruth; Kucian, Karin

2017-01-01

The link between number and space has been discussed in the literature for some time, resulting in the theory that number, space and time might be part of a generalized magnitude system. To date, several behavioral and neuroimaging findings support the notion of a generalized magnitude system, although contradictory results showing a partial overlap or separate magnitude systems are also found. The possible existence of a generalized magnitude processing area leads to the question how individuals with developmental dyscalculia (DD), known for deficits in numerical-arithmetical abilities, process magnitudes. By means of neuropsychological tests and functional magnetic resonance imaging (fMRI) we aimed to examine the relationship between number and space in typical and atypical development. Participants were 16 adolescents with DD (14.1 years) and 14 typically developing (TD) peers (13.8 years). In the fMRI paradigm participants had to perform discrete (arrays of dots) and continuous magnitude (angles) comparisons as well as a mental rotation task. In the neuropsychological tests, adolescents with dyscalculia performed significantly worse in numerical and complex visuo-spatial tasks. However, they showed similar results to TD peers when making discrete and continuous magnitude decisions during the neuropsychological tests and the fMRI paradigm. A conjunction analysis of the fMRI data revealed commonly activated higher order visual (inferior and middle occipital gyrus) and parietal (inferior and superior parietal lobe) magnitude areas for the discrete and continuous magnitude tasks. Moreover, no differences were found when contrasting both magnitude processing conditions, favoring the possibility of a generalized magnitude system. Group comparisons further revealed that dyscalculic subjects showed increased activation in domain general regions, whilst TD peers activate domain specific areas to a greater extent. In conclusion, our results point to the existence of a generalized magnitude system in the occipito-parietal stream in typical development. The detailed investigation of spatial and numerical magnitude abilities in DD reveals that the deficits in number processing and arithmetic cannot be explained with a general magnitude deficiency. Our results further indicate that multiple neuro-cognitive components might contribute to the explanation of DD.

Adolescents with Developmental Dyscalculia Do Not Have a Generalized Magnitude Deficit – Processing of Discrete and Continuous Magnitudes

PubMed Central

McCaskey, Ursina; von Aster, Michael; O’Gorman Tuura, Ruth; Kucian, Karin

2017-01-01

The link between number and space has been discussed in the literature for some time, resulting in the theory that number, space and time might be part of a generalized magnitude system. To date, several behavioral and neuroimaging findings support the notion of a generalized magnitude system, although contradictory results showing a partial overlap or separate magnitude systems are also found. The possible existence of a generalized magnitude processing area leads to the question how individuals with developmental dyscalculia (DD), known for deficits in numerical-arithmetical abilities, process magnitudes. By means of neuropsychological tests and functional magnetic resonance imaging (fMRI) we aimed to examine the relationship between number and space in typical and atypical development. Participants were 16 adolescents with DD (14.1 years) and 14 typically developing (TD) peers (13.8 years). In the fMRI paradigm participants had to perform discrete (arrays of dots) and continuous magnitude (angles) comparisons as well as a mental rotation task. In the neuropsychological tests, adolescents with dyscalculia performed significantly worse in numerical and complex visuo-spatial tasks. However, they showed similar results to TD peers when making discrete and continuous magnitude decisions during the neuropsychological tests and the fMRI paradigm. A conjunction analysis of the fMRI data revealed commonly activated higher order visual (inferior and middle occipital gyrus) and parietal (inferior and superior parietal lobe) magnitude areas for the discrete and continuous magnitude tasks. Moreover, no differences were found when contrasting both magnitude processing conditions, favoring the possibility of a generalized magnitude system. Group comparisons further revealed that dyscalculic subjects showed increased activation in domain general regions, whilst TD peers activate domain specific areas to a greater extent. In conclusion, our results point to the existence of a generalized magnitude system in the occipito-parietal stream in typical development. The detailed investigation of spatial and numerical magnitude abilities in DD reveals that the deficits in number processing and arithmetic cannot be explained with a general magnitude deficiency. Our results further indicate that multiple neuro-cognitive components might contribute to the explanation of DD. PMID:28373834

The link between mental rotation ability and basic numerical representations

PubMed Central

Thompson, Jacqueline M.; Nuerk, Hans-Christoph; Moeller, Korbinian; Cohen Kadosh, Roi

2013-01-01

Mental rotation and number representation have both been studied widely, but although mental rotation has been linked to higher-level mathematical skills, to date it has not been shown whether mental rotation ability is linked to the most basic mental representation and processing of numbers. To investigate the possible connection between mental rotation abilities and numerical representation, 43 participants completed four tasks: 1) a standard pen-and-paper mental rotation task; 2) a multi-digit number magnitude comparison task assessing the compatibility effect, which indicates separate processing of decade and unit digits; 3) a number-line mapping task, which measures precision of number magnitude representation; and 4) a random number generation task, which yields measures both of executive control and of spatial number representations. Results show that mental rotation ability correlated significantly with both size of the compatibility effect and with number mapping accuracy, but not with any measures from the random number generation task. Together, these results suggest that higher mental rotation abilities are linked to more developed number representation, and also provide further evidence for the connection between spatial and numerical abilities. PMID:23933002

Variable-order fractional MSD function to describe the evolution of protein lateral diffusion ability in cell membranes

NASA Astrophysics Data System (ADS)

Yin, Deshun; Qu, Pengfei

2018-02-01

Protein lateral diffusion is considered anomalous in the plasma membrane. And this diffusion is related to membrane microstructure. In order to better describe the property of protein lateral diffusion and find out the inner relationship between protein lateral diffusion and membrane microstructure, this article applies variable-order fractional mean square displacement (f-MSD) function for characterizing the anomalous diffusion. It is found that the variable order can reflect the evolution of diffusion ability. The results of numerical simulation demonstrate variable-order f-MSD function can predict the tendency of anomalous diffusion during the process of confined diffusion. It is also noted that protein lateral diffusion ability during the processes of confined and hop diffusion can be split into three parts. In addition, the comparative analyses reveal that the variable order is related to the confinement-domain size and microstructure of compartment boundary too.

A Comparison of Mother-Tongue Curricula of Successful Countries in PISA and Turkey by Higher-Order Thinking Processes

ERIC Educational Resources Information Center

Cer, Erkan

2018-01-01

Purpose: The purpose of the current study is to reveal general qualities of the objectives in the mother-tongue curricula of Hong Kong and Shanghai-China, South Korea, Singapore, and Turkey in terms of higher-order thinking processes specified by PISA tests. Research Methods: In this study, the researcher used a qualitative research design.…

Still the Main Show in Town? Assessing Political Saliency of the Bologna Process across Time and Space

ERIC Educational Resources Information Center

Vukasovic, Martina; Jungblut, Jens; Elken, Mari

2017-01-01

Numerous studies focused on the linkages between the Bologna Process and system--as well as organizational-level changes--implying significance of the process for higher education policy dynamics. However, what has been lacking is a closer examination of the political importance of Bologna for the different actors involved and whether this varies…

Nonlinear propagation analysis of few-optical-cycle pulses for subfemtosecond compression and carrier envelope phase effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mizuta, Yo; Nagasawa, Minoru; Ohtani, Morimasa

2005-12-15

A numerical approach called Fourier direct method (FDM) is applied to nonlinear propagation of optical pulses with the central wavelength 800 nm, the width 2.67-12.00 fs, and the peak power 25-6870 kW in a fused-silica fiber. Bidirectional propagation, delayed Raman response, nonlinear dispersion (self-steepening, core dispersion), as well as correct linear dispersion are incorporated into 'bidirectional propagation equations' which are derived directly from Maxwell's equations. These equations are solved for forward and backward waves, instead of the electric-field envelope as in the nonlinear Schroedinger equation (NLSE). They are integrated as multidimensional simultaneous evolution equations evolved in space. We investigate, bothmore » theoretically and numerically, the validity and the limitation of assumptions and approximations used for deriving the NLSE. Also, the accuracy and the efficiency of the FDM are compared quantitatively with those of the finite-difference time-domain numerical approach. The time-domain size 500 fs and the number of grid points in time 2048 are chosen to investigate numerically intensity spectra, spectral phases, and temporal electric-field profiles up to the propagation distance 1.0 mm. On the intensity spectrum of a few-optical-cycle pulses, the self-steepening, core dispersion, and the delayed Raman response appear as dominant, middle, and slight effects, respectively. The delayed Raman response and the core dispersion reduce the effective nonlinearity. Correct linear dispersion is important since it affects the intensity spectrum sensitively. For the compression of femtosecond optical pulses by the complete phase compensation, the shortness and the pulse quality of compressed pulses are remarkably improved by the intense initial peak power rather than by the short initial pulse width or by the propagation distance longer than 0.1 mm. They will be compressed as short as 0.3 fs below the damage threshold of fused-silica fiber 6 MW. It is demonstrated that the carrier envelope phase (CEP) causes the difference on the temporal electric-field profile and the intensity spectrum for the initial peak power of the order of megawatts. At the propagation distance longer than the coherence length for third-order harmonics, the difference grows in the spectral components around the third-order and higher-order harmonics. The CEP can be a sensitive marker to monitor the evolution of nonlinear optical process by a few-optical-cycle electric-field wave-packet source.« less

An evaluation of solution algorithms and numerical approximation methods for modeling an ion exchange process

NASA Astrophysics Data System (ADS)

Bu, Sunyoung; Huang, Jingfang; Boyer, Treavor H.; Miller, Cass T.

2010-07-01

The focus of this work is on the modeling of an ion exchange process that occurs in drinking water treatment applications. The model formulation consists of a two-scale model in which a set of microscale diffusion equations representing ion exchange resin particles that vary in size and age are coupled through a boundary condition with a macroscopic ordinary differential equation (ODE), which represents the concentration of a species in a well-mixed reactor. We introduce a new age-averaged model (AAM) that averages all ion exchange particle ages for a given size particle to avoid the expensive Monte-Carlo simulation associated with previous modeling applications. We discuss two different numerical schemes to approximate both the original Monte-Carlo algorithm and the new AAM for this two-scale problem. The first scheme is based on the finite element formulation in space coupled with an existing backward difference formula-based ODE solver in time. The second scheme uses an integral equation based Krylov deferred correction (KDC) method and a fast elliptic solver (FES) for the resulting elliptic equations. Numerical results are presented to validate the new AAM algorithm, which is also shown to be more computationally efficient than the original Monte-Carlo algorithm. We also demonstrate that the higher order KDC scheme is more efficient than the traditional finite element solution approach and this advantage becomes increasingly important as the desired accuracy of the solution increases. We also discuss issues of smoothness, which affect the efficiency of the KDC-FES approach, and outline additional algorithmic changes that would further improve the efficiency of these developing methods for a wide range of applications.

Wigner surmises and the two-dimensional homogeneous Poisson point process.

PubMed

Sakhr, Jamal; Nieminen, John M

2006-04-01

We derive a set of identities that relate the higher-order interpoint spacing statistics of the two-dimensional homogeneous Poisson point process to the Wigner surmises for the higher-order spacing distributions of eigenvalues from the three classical random matrix ensembles. We also report a remarkable identity that equates the second-nearest-neighbor spacing statistics of the points of the Poisson process and the nearest-neighbor spacing statistics of complex eigenvalues from Ginibre's ensemble of 2 x 2 complex non-Hermitian random matrices.

Numerical simulation of transport and sequential biodegradation of chlorinated aliphatic hydrocarbons using CHAIN_2D

NASA Astrophysics Data System (ADS)

Schaerlaekens, J.; Mallants, D.; Imûnek, J.; van Genuchten, M. Th.; Feyen, J.

1999-12-01

Microbiological degradation of perchloroethylene (PCE) under anaerobic conditions follows a series of chain reactions, in which, sequentially, trichloroethylene (TCE), cis-dichloroethylene (c-DCE), vinylchloride (VC) and ethene are generated. First-order degradation rate constants, partitioning coefficients and mass exchange rates for PCE, TCE, c-DCE and VC were compiled from the literature. The parameters were used in a case study of pump-and-treat remediation of a PCE-contaminated site near Tilburg, The Netherlands. Transport, non-equilibrium sorption and biodegradation chain processes at the site were simulated using the CHAIN_2D code without further calibration. The modelled PCE compared reasonably well with observed PCE concentrations in the pumped water. We also performed a scenario analysis by applying several increased reductive dechlorination rates, reflecting different degradation conditions (e.g. addition of yeast extract and citrate). The scenario analysis predicted considerably higher concentrations of the degradation products as a result of enhanced reductive dechlorination of PCE. The predicted levels of the very toxic compound VC were now an order of magnitude above the maximum permissible concentration levels.

Polynomial sequences for bond percolation critical thresholds

DOE PAGES

Scullard, Christian R.

2011-09-22

In this paper, I compute the inhomogeneous (multi-probability) bond critical surfaces for the (4, 6, 12) and (3 4, 6) using the linearity approximation described in (Scullard and Ziff, J. Stat. Mech. 03021), implemented as a branching process of lattices. I find the estimates for the bond percolation thresholds, pc(4, 6, 12) = 0.69377849... and p c(3 4, 6) = 0.43437077..., compared with Parviainen’s numerical results of p c = 0.69373383... and p c = 0.43430621... . These deviations are of the order 10 -5, as is standard for this method. Deriving thresholds in this way for a given latticemore » leads to a polynomial with integer coefficients, the root in [0, 1] of which gives the estimate for the bond threshold and I show how the method can be refined, leading to a series of higher order polynomials making predictions that likely converge to the exact answer. Finally, I discuss how this fact hints that for certain graphs, such as the kagome lattice, the exact bond threshold may not be the root of any polynomial with integer coefficients.« less

Higher Order Cumulant Studies of Ocean Surface Random Fields from Satellite Altimeter Data

NASA Technical Reports Server (NTRS)

Cheng, B.

1996-01-01

Higher order statistics, especially 2nd order statistics, have been used to study ocean processes for many years in the past, and occupy an appreciable part of the research literature on physical oceanography. They in turn form part of a much larger field of study in statistical fluid mechanics.

A lattice Boltzmann model for the Burgers-Fisher equation.

PubMed

Zhang, Jianying; Yan, Guangwu

2010-06-01

A lattice Boltzmann model is developed for the one- and two-dimensional Burgers-Fisher equation based on the method of the higher-order moment of equilibrium distribution functions and a series of partial differential equations in different time scales. In order to obtain the two-dimensional Burgers-Fisher equation, vector sigma(j) has been used. And in order to overcome the drawbacks of "error rebound," a new assumption of additional distribution is presented, where two additional terms, in first order and second order separately, are used. Comparisons with the results obtained by other methods reveal that the numerical solutions obtained by the proposed method converge to exact solutions. The model under new assumption gives better results than that with second order assumption. (c) 2010 American Institute of Physics.

Features in simulation of crystal growth using the hyperbolic PFC equation and the dependence of the numerical solution on the parameters of the computational grid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Starodumov, Ilya; Kropotin, Nikolai

2016-08-10

We investigate the three-dimensional mathematical model of crystal growth called PFC (Phase Field Crystal) in a hyperbolic modification. This model is also called the modified model PFC (originally PFC model is formulated in parabolic form) and allows to describe both slow and rapid crystallization processes on atomic length scales and on diffusive time scales. Modified PFC model is described by the differential equation in partial derivatives of the sixth order in space and second order in time. The solution of this equation is possible only by numerical methods. Previously, authors created the software package for the solution of the Phasemore » Field Crystal problem, based on the method of isogeometric analysis (IGA) and PetIGA program library. During further investigation it was found that the quality of the solution can strongly depends on the discretization parameters of a numerical method. In this report, we show the features that should be taken into account during constructing the computational grid for the numerical simulation.« less

Electromagnetic properties of metal-dielectric media and their applications

NASA Astrophysics Data System (ADS)

Animilli, Shravan Rakesh

The main objective of this dissertation is to investigate nano-structured random composite materials, which exhibit anomalous phenomena, such as the extraordinary enhancements of linear and non-linear optical processes due to excitation of collective electronic states, surface plasmons (SP). The main goal is to develop a time and memory efficient novel numerical method to study the properties of these random media in three dimensions (3D) by utilization of multi core processing and packages such as MPI for parallel execution. The developed numerical studies are then utilized to provide a comprehensive characterization and optimization of a surface plasmon enhanced solar cell (SPESC) and to serve as a test bed for enhanced bio and chemical sensing. In this context, this thesis work develops an efficient and exact numerical algorithm here referred to as Block Elimination Method (BE) which provides the unique capability of modeling extremely large scale composite materials (with up to 1 million strongly interacting metal or dielectric particles). This capability is crucial in order to study the electromagnetic response of large scale inhomogeneous (fractal) films and bulk composites at critical concentrations (percolation). The developed numerical method is used to accurately estimate parameters that describe the composite materials, including the effective conductivity and correlation length scaling exponents, as well as density of states and localization length exponents at the band center. This works reveals, for a first time, a unique de-localization mechanism that plays an important role in the excitation of charge-density waves, i.e. surface plasmons (SP), in metal-dielectric composites. It also shows that in 3D metal-dielectric percolation systems the local fields distribution function for frequencies close to the single particle plasmon resonance is log-normal which is a signature of a metal-dielectric phase transition manifested in the optical response of the composites. Based on the obtained numerical data a scaling theory for the higher order electric field moments is developed. A distinct evidence of singularities in the surface plasmon density of states and localization length is obtained, correlating with results previously obtained for two dimensional systems. This leads to the main finding of this work; i.e., the delocalization of surface plasmon states in percolating metal-dielectric composite materials is universally present regardless of the dimensionality of the problem. This dissertation also proposes a new approach toward developing highly efficient inorganic/organic solar cell, by presenting a method for enhancement in the optical absorption and overall cell efficiency. Specifically, the approach improves the operation characteristics of inorganic semiconductor (e.g. Si and a-Si) and organic (P3HT:PCBM) thin film solar cells by integrating a thin, inhomogeneous, metal-dielectric composite (MDC) electrode at the interface between the transparent electrode and active layer. Through numerical simulations, we show that under solar illumination, surface plasmons are excited within the fractal MDC electrode across an extremely broad range of optical frequencies, trapping the incoming light and ensuring an optimal absorption into the active layer of the solar cells. An analytical model is developed to study the I-V characteristics of the cells, providing a pathway toward achieving optimal efficiency and better understanding of the behavior of charge carriers. Using this model, it is shown that including gold MDC electrodes can lead to an enhancement in solar cell power conversion efficiency up to 33% higher compared to the benchmark device.

Towards Automatic Processing of Virtual City Models for Simulations

NASA Astrophysics Data System (ADS)

Piepereit, R.; Schilling, A.; Alam, N.; Wewetzer, M.; Pries, M.; Coors, V.

2016-10-01

Especially in the field of numerical simulations, such as flow and acoustic simulations, the interest in using virtual 3D models to optimize urban systems is increasing. The few instances in which simulations were already carried out in practice have been associated with an extremely high manual and therefore uneconomical effort for the processing of models. Using different ways of capturing models in Geographic Information System (GIS) and Computer Aided Engineering (CAE), increases the already very high complexity of the processing. To obtain virtual 3D models suitable for simulation, we developed a tool for automatic processing with the goal to establish ties between the world of GIS and CAE. In this paper we introduce a way to use Coons surfaces for the automatic processing of building models in LoD2, and investigate ways to simplify LoD3 models in order to reduce unnecessary information for a numerical simulation.

A 2D and 3D Code Comparison of Turbulent Mixing in Spherical Implosions

NASA Astrophysics Data System (ADS)

Flaig, Markus; Thornber, Ben; Grieves, Brian; Youngs, David; Williams, Robin; Clark, Dan; Weber, Chris

2016-10-01

Turbulent mixing due to Richtmyer-Meshkov and Rayleigh-Taylor instabilities has proven to be a major obstacle on the way to achieving ignition in inertial confinement fusion (ICF) implosions. Numerical simulations are an important tool for understanding the mixing process, however, the results of such simulations depend on the choice of grid geometry and the numerical scheme used. In order to clarify this issue, we compare the simulation codes FLASH, TURMOIL, HYDRA, MIRANDA and FLAMENCO for the problem of the growth of single- and multi-mode perturbations on the inner interface of a dense imploding shell. We consider two setups: A single-shock setup with a convergence ratio of 4, as well as a higher convergence multi-shock setup that mimics a typical NIF mixcap experiment. We employ both singlemode and ICF-like broadband perturbations. We find good agreement between all codes concerning the evolution of the mix layer width, however, the are differences in the small scale mixing. We also develop a Bell-Plesset model that is able to predict the mix layer width and find excellent agreement with the simulation results. This work was supported by resources provided by the Pawsey Supercomputing Centre with funding from the Australian Government.

Early Earth plume-lid tectonics: A high-resolution 3D numerical modelling approach

NASA Astrophysics Data System (ADS)

Fischer, R.; Gerya, T.

2016-10-01

Geological-geochemical evidence point towards higher mantle potential temperature and a different type of tectonics (global plume-lid tectonics) in the early Earth (>3.2 Ga) compared to the present day (global plate tectonics). In order to investigate tectono-magmatic processes associated with plume-lid tectonics and crustal growth under hotter mantle temperature conditions, we conduct a series of 3D high-resolution magmatic-thermomechanical models with the finite-difference code I3ELVIS. No external plate tectonic forces are applied to isolate 3D effects of various plume-lithosphere and crust-mantle interactions. Results of the numerical experiments show two distinct phases in coupled crust-mantle evolution: (1) a longer (80-100 Myr) and relatively quiet 'growth phase' which is marked by growth of crust and lithosphere, followed by (2) a short (∼20 Myr) and catastrophic 'removal phase', where unstable parts of the crust and mantle lithosphere are removed by eclogitic dripping and later delamination. This modelling suggests that the early Earth plume-lid tectonic regime followed a pattern of episodic growth and removal also called episodic overturn with a periodicity of ∼100 Myr.

High-Speed Friction-Stir Welding To Enable Aluminum Tailor-Welded Blanks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hovanski, Yuri; Upadhyay, Piyush; Carsley, John

Current joining technologies for automotive aluminum alloys are utilized in low-volume and niche applications, and have yet to be scaled for the high-volume vehicle market. This study targeted further weight reduction, part reduction, and cost savings by enabling tailor-welded blank technology for aluminum alloys at high-volumes. While friction stir welding has been traditionally applied at linear velocities less than one meter per minute, high volume production applications demand the process be extended to higher velocities more amenable to cost sensitive production environments. Unfortunately, weld parameters and performance developed and characterized at low to moderate welding velocities do not directly translatemore » to high speed linear friction stir welding. Therefore, in order to facilitate production of high volume aluminum welded components, parameters were developed with a minimum welding velocity of three meters per minute. With an emphasis on weld quality, welded blanks were evaluated for post-weld formability utilizing a combination of numerical and experimental methods. Evaluation across scales was ultimately validated by stamping full-size production door inner panels made from dissimilar thickness aluminum tailor-welded blanks, which provided validation of the numerical and experimental analysis of laboratory scale tests.« less

Reinforcement learning for resource allocation in LEO satellite networks.

PubMed

Usaha, Wipawee; Barria, Javier A

2007-06-01

In this paper, we develop and assess online decision-making algorithms for call admission and routing for low Earth orbit (LEO) satellite networks. It has been shown in a recent paper that, in a LEO satellite system, a semi-Markov decision process formulation of the call admission and routing problem can achieve better performance in terms of an average revenue function than existing routing methods. However, the conventional dynamic programming (DP) numerical solution becomes prohibited as the problem size increases. In this paper, two solution methods based on reinforcement learning (RL) are proposed in order to circumvent the computational burden of DP. The first method is based on an actor-critic method with temporal-difference (TD) learning. The second method is based on a critic-only method, called optimistic TD learning. The algorithms enhance performance in terms of requirements in storage, computational complexity and computational time, and in terms of an overall long-term average revenue function that penalizes blocked calls. Numerical studies are carried out, and the results obtained show that the RL framework can achieve up to 56% higher average revenue over existing routing methods used in LEO satellite networks with reasonable storage and computational requirements.

Enabling high speed friction stir welding of aluminum tailor welded blanks

NASA Astrophysics Data System (ADS)

Hovanski, Yuri

Current welding technologies for production of aluminum tailor-welded blanks (TWBs) are utilized in low-volume and niche applications, and have yet to be scaled for the high-volume vehicle market. This study targeted further weight reduction, part reduction, and cost savings by enabling tailor-welded blank technology for aluminum alloys at high-volumes. While friction stir welding (FSW) has traditionally been applied at linear velocities less than one meter per minute, high volume production applications demand the process be extended to higher velocities more amenable to cost sensitive production environments. Unfortunately, weld parameters and performance developed and characterized at low to moderate welding velocities do not directly translate to high speed linear friction stir welding. Therefore, in order to facilitate production of high volume aluminum FSW components, parameters were developed with a minimum welding velocity of three meters per minute. With an emphasis on weld quality, welded blanks were evaluated for post-weld formability using a combination of numerical and experimental methods. Evaluation across scales was ultimately validated by stamping full-size production door inner panels made from dissimilar thickness aluminum tailor-welded blanks, which provided validation of the numerical and experimental analysis of laboratory scale tests.

Buckling of a growing tissue and the emergence of two-dimensional patterns☆

PubMed Central

Nelson, M.R.; King, J.R.; Jensen, O.E.

2013-01-01

The process of biological growth and the associated generation of residual stress has previously been considered as a driving mechanism for tissue buckling and pattern selection in numerous areas of biology. Here, we develop a two-dimensional thin plate theory to simulate the growth of cultured intestinal epithelial cells on a deformable substrate, with the goal of elucidating how a tissue engineer might best recreate the regular array of invaginations (crypts of Lieberkühn) found in the wall of the mammalian intestine. We extend the standard von Kármán equations to incorporate inhomogeneity in the plate’s mechanical properties and surface stresses applied to the substrate by cell proliferation. We determine numerically the configurations of a homogeneous plate under uniform cell growth, and show how tethering to an underlying elastic foundation can be used to promote higher-order buckled configurations. We then examine the independent effects of localised softening of the substrate and spatial patterning of cellular growth, demonstrating that (within a two-dimensional framework, and contrary to the predictions of one-dimensional models) growth patterning constitutes a more viable mechanism for control of crypt distribution than does material inhomogeneity. PMID:24128749

Buckling of a growing tissue and the emergence of two-dimensional patterns.

PubMed

Nelson, M R; King, J R; Jensen, O E

2013-12-01

The process of biological growth and the associated generation of residual stress has previously been considered as a driving mechanism for tissue buckling and pattern selection in numerous areas of biology. Here, we develop a two-dimensional thin plate theory to simulate the growth of cultured intestinal epithelial cells on a deformable substrate, with the goal of elucidating how a tissue engineer might best recreate the regular array of invaginations (crypts of Lieberkühn) found in the wall of the mammalian intestine. We extend the standard von Kármán equations to incorporate inhomogeneity in the plate's mechanical properties and surface stresses applied to the substrate by cell proliferation. We determine numerically the configurations of a homogeneous plate under uniform cell growth, and show how tethering to an underlying elastic foundation can be used to promote higher-order buckled configurations. We then examine the independent effects of localised softening of the substrate and spatial patterning of cellular growth, demonstrating that (within a two-dimensional framework, and contrary to the predictions of one-dimensional models) growth patterning constitutes a more viable mechanism for control of crypt distribution than does material inhomogeneity. Copyright © 2013 Elsevier Inc. All rights reserved.

Method for simulating discontinuous physical systems

DOEpatents

Baty, Roy S.; Vaughn, Mark R.

2001-01-01

The mathematical foundations of conventional numerical simulation of physical systems provide no consistent description of the behavior of such systems when subjected to discontinuous physical influences. As a result, the numerical simulation of such problems requires ad hoc encoding of specific experimental results in order to address the behavior of such discontinuous physical systems. In the present invention, these foundations are replaced by a new combination of generalized function theory and nonstandard analysis. The result is a class of new approaches to the numerical simulation of physical systems which allows the accurate and well-behaved simulation of discontinuous and other difficult physical systems, as well as simpler physical systems. Applications of this new class of numerical simulation techniques to process control, robotics, and apparatus design are outlined.

Accelerated numerical processing of electronically recorded holograms with reduced speckle noise.

PubMed

Trujillo, Carlos; Garcia-Sucerquia, Jorge

2013-09-01

The numerical reconstruction of digitally recorded holograms suffers from speckle noise. An accelerated method that uses general-purpose computing in graphics processing units to reduce that noise is shown. The proposed methodology utilizes parallelized algorithms to record, reconstruct, and superimpose multiple uncorrelated holograms of a static scene. For the best tradeoff between reduction of the speckle noise and processing time, the method records, reconstructs, and superimposes six holograms of 1024 × 1024 pixels in 68 ms; for this case, the methodology reduces the speckle noise by 58% compared with that exhibited by a single hologram. The fully parallelized method running on a commodity graphics processing unit is one order of magnitude faster than the same technique implemented on a regular CPU using its multithreading capabilities. Experimental results are shown to validate the proposal.

Brush seal numerical simulation: Concepts and advances

NASA Technical Reports Server (NTRS)

Braun, M. J.; Kudriavtsev, V. V.

1994-01-01

The development of the brush seal is considered to be most promising among the advanced type seals that are presently in use in the high speed turbomachinery. The brush is usually mounted on the stationary portions of the engine and has direct contact with the rotating element, in the process of limiting the 'unwanted' leakage flows between stages, or various engine cavities. This type of sealing technology is providing high (in comparison with conventional seals) pressure drops due mainly to the high packing density (around 100 bristles/sq mm), and brush compliance with the rotor motions. In the design of modern aerospace turbomachinery leakage flows between the stages must be minimal, thus contributing to the higher efficiency of the engine. Use of the brush seal instead of the labyrinth seal reduces the leakage flow by one order of magnitude. Brush seals also have been found to enhance dynamic performance, cost less, and are lighter than labyrinth seals. Even though industrial brush seals have been successfully developed through extensive experimentation, there is no comprehensive numerical methodology for the design or prediction of their performance. The existing analytical/numerical approaches are based on bulk flow models and do not allow the investigation of the effects of brush morphology (bristle arrangement), or brushes arrangement (number of brushes, spacing between them), on the pressure drops and flow leakage. An increase in the brush seal efficiency is clearly a complex problem that is closely related to the brush geometry and arrangement, and can be solved most likely only by means of a numerically distributed model.

Numerical study on non-locally reacting behavior of nacelle liners incorporating drainage slots

NASA Astrophysics Data System (ADS)

Chen, Chao; Li, Xiaodong; Thiele, Frank

2018-06-01

For acoustic liners used in current commercial nacelles, in order to prevent any liquid accumulating in the resonators, drainage slots are incorporated on the partition walls between closely packed cavities. Recently, an experimental study conducted by Busse-Gerstengarbe et al. shown that the cell interaction introduced by drainage slots causes an additional dissipation peak which increases with the size of the slot. However, the variation of damping process due to drainage slots is still not fully understood. Therefore, a numerical study based on computational aeroacoustic methods is carried out to investigate the mechanism of the changed attenuation characteristics due to drainage slots in presence of grazing incident sound waves with low or high intensities. Different slot configurations are designed based on the generic non-locally reacting liner model adopted in the experimental investigation. Both 2-D and 3-D numerical simulations of only slit resonators are carried out. Numerical results indicate that the extra peak is a result of a resonance excited in the second cavity at specific frequency. Under high sound pressure level incoming waves, the basic characteristics of the acoustic performance remain. However, vortex shedding transpires at the resonances around both the slits and the drainage slot. Vorticity contours show that the connection of two coupled cavities decreases the strength of vortex shedding around the basic Helmholtz resonance due to a higher energy reflection. Meanwhile, the cell interaction significantly increases the vorticity magnitude near the extra resonant frequency. Finally, a semi-empirical model is derived to predict the extra attenuation peak frequency.

Numerical simulation of the laser welding process for the prediction of temperature distribution on welded aluminium aircraft components

NASA Astrophysics Data System (ADS)

Tsirkas, S. A.

2018-03-01

The present investigation is focused to the modelling of the temperature field in aluminium aircraft components welded by a CO2 laser. A three-dimensional finite element model has been developed to simulate the laser welding process and predict the temperature distribution in T-joint laser welded plates with fillet material. The simulation of the laser beam welding process was performed using a nonlinear heat transfer analysis, based on a keyhole formation model analysis. The model employs the technique of element ;birth and death; in order to simulate the weld fillet. Various phenomena associated with welding like temperature dependent material properties and heat losses through convection and radiation were accounted for in the model. The materials considered were 6056-T78 and 6013-T4 aluminium alloys, commonly used for aircraft components. The temperature distribution during laser welding process has been calculated numerically and validated by experimental measurements on different locations of the welded structure. The numerical results are in good agreement with the experimental measurements.

Phase-plane analysis to an “anisotropic” higher-order traffic flow model

NASA Astrophysics Data System (ADS)

Wu, Chun-Xiu

2018-04-01

The qualitative theory of differential equations is applied to investigate the traveling wave solution to an “anisotropic” higher-order viscous traffic flow model under the Lagrange coordinate system. The types and stabilities of the equilibrium points are discussed in the phase plane. Through the numerical simulation, the overall distribution structures of trajectories are drawn to analyze the relation between the phase diagram and the selected conservative solution variables, and the influences of the parameters on the system are studied. The limit-circle, limit circle-spiral point, saddle-spiral point and saddle-nodal point solutions are obtained. These steady-state solutions provide good explanation for the phenomena of the oscillatory and homogeneous congestions in real-world traffic.

Front and pulse solutions for the complex Ginzburg-Landau equation with higher-order terms.

PubMed

Tian, Huiping; Li, Zhonghao; Tian, Jinping; Zhou, Guosheng

2002-12-01

We investigate one-dimensional complex Ginzburg-Landau equation with higher-order terms and discuss their influences on the multiplicity of solutions. An exact analytic front solution is presented. By stability analysis for the original partial differential equation, we derive its necessary stability condition for amplitude perturbations. This condition together with the exact front solution determine the region of parameter space where the uniformly translating front solution can exist. In addition, stable pulses, chaotic pulses, and attenuation pulses appear generally if the parameters are out of the range. Finally, applying these analysis into the optical transmission system numerically we find that the stable transmission of optical pulses can be achieved if the parameters are appropriately chosen.

Excitation of Higher Order Modes of Cylindrical Dielectric Resonator Antenna using Dual-slot feed

NASA Astrophysics Data System (ADS)

Ojha, A. K.; Praveen Kumar, A. V.

2018-03-01

Excitation of the higher order modes (HOM) of a cylindrical dielectric resonator antenna(DRA) of high relative permittivity, using dual feed scheme is investigated. The feed scheme uses a pair of narrow slots and is chosen on the basis of the field distribution of the desired DRA modes. Numerical studies using ANSYS HFSS show that the dual-feed excited a combination of two HOMs, which are identified as HEM21δ and TM01δ. The mixed-up nature is further verified through studying the radiation pattern of the DRA which shows azimuthal asymmetry and low gain. It is suggested that if one of the HOM is suppressed, better antenna performance can be achieved.

Analysis and control of the dynamical response of a higher order drifting oscillator

PubMed Central

Páez Chávez, Joseph; Pavlovskaia, Ekaterina; Wiercigroch, Marian

2018-01-01

This paper studies a position feedback control strategy for controlling a higher order drifting oscillator which could be used in modelling vibro-impact drilling. Special attention is given to two control issues, eliminating bistability and suppressing chaos, which may cause inefficient and unstable drilling. Numerical continuation methods implemented via the continuation platform COCO are adopted to investigate the dynamical response of the system. Our analyses show that the proposed controller is capable of eliminating coexisting attractors and mitigating chaotic behaviour of the system, providing that its feedback control gain is chosen properly. Our investigations also reveal that, when the slider’s property modelling the drilled formation changes, the rate of penetration for the controlled drilling can be significantly improved. PMID:29507508

Analysis and control of the dynamical response of a higher order drifting oscillator

NASA Astrophysics Data System (ADS)

Liu, Yang; Páez Chávez, Joseph; Pavlovskaia, Ekaterina; Wiercigroch, Marian

2018-02-01

This paper studies a position feedback control strategy for controlling a higher order drifting oscillator which could be used in modelling vibro-impact drilling. Special attention is given to two control issues, eliminating bistability and suppressing chaos, which may cause inefficient and unstable drilling. Numerical continuation methods implemented via the continuation platform COCO are adopted to investigate the dynamical response of the system. Our analyses show that the proposed controller is capable of eliminating coexisting attractors and mitigating chaotic behaviour of the system, providing that its feedback control gain is chosen properly. Our investigations also reveal that, when the slider's property modelling the drilled formation changes, the rate of penetration for the controlled drilling can be significantly improved.

Optical frequency-domain chromatic dispersion measurement method for higher-order modes in an optical fiber.

PubMed

Ahn, Tae-Jung; Jung, Yongmin; Oh, Kyunghwan; Kim, Dug Young

2005-12-12

We propose a new chromatic dispersion measurement method for the higher-order modes of an optical fiber using optical frequency modulated continuous-wave (FMCW) interferometry. An optical fiber which supports few excited modes was prepared for our experiments. Three different guiding modes of the fiber were identified by using far-field spatial beam profile measurements and confirmed with numerical mode analysis. By using the principle of a conventional FMWC interferometry with a tunable external cavity laser, we have demonstrated that the chromatic dispersion of a few-mode optical fiber can be obtained directly and quantitatively as well as qualitatively. We have also compared our measurement results with those of conventional modulation phase-shift method.

Regression-based reduced-order models to predict transient thermal output for enhanced geothermal systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mudunuru, Maruti Kumar; Karra, Satish; Harp, Dylan Robert

Reduced-order modeling is a promising approach, as many phenomena can be described by a few parameters/mechanisms. An advantage and attractive aspect of a reduced-order model is that it is computational inexpensive to evaluate when compared to running a high-fidelity numerical simulation. A reduced-order model takes couple of seconds to run on a laptop while a high-fidelity simulation may take couple of hours to run on a high-performance computing cluster. The goal of this paper is to assess the utility of regression-based reduced-order models (ROMs) developed from high-fidelity numerical simulations for predicting transient thermal power output for an enhanced geothermal reservoirmore » while explicitly accounting for uncertainties in the subsurface system and site-specific details. Numerical simulations are performed based on equally spaced values in the specified range of model parameters. Key sensitive parameters are then identified from these simulations, which are fracture zone permeability, well/skin factor, bottom hole pressure, and injection flow rate. We found the fracture zone permeability to be the most sensitive parameter. The fracture zone permeability along with time, are used to build regression-based ROMs for the thermal power output. The ROMs are trained and validated using detailed physics-based numerical simulations. Finally, predictions from the ROMs are then compared with field data. We propose three different ROMs with different levels of model parsimony, each describing key and essential features of the power production curves. The coefficients in the proposed regression-based ROMs are developed by minimizing a non-linear least-squares misfit function using the Levenberg–Marquardt algorithm. The misfit function is based on the difference between numerical simulation data and reduced-order model. ROM-1 is constructed based on polynomials up to fourth order. ROM-1 is able to accurately reproduce the power output of numerical simulations for low values of permeabilities and certain features of the field-scale data. ROM-2 is a model with more analytical functions consisting of polynomials up to order eight, exponential functions and smooth approximations of Heaviside functions, and accurately describes the field-data. At higher permeabilities, ROM-2 reproduces numerical results better than ROM-1, however, there is a considerable deviation from numerical results at low fracture zone permeabilities. ROM-3 consists of polynomials up to order ten, and is developed by taking the best aspects of ROM-1 and ROM-2. ROM-1 is relatively parsimonious than ROM-2 and ROM-3, while ROM-2 overfits the data. ROM-3 on the other hand, provides a middle ground for model parsimony. Based on R 2-values for training, validation, and prediction data sets we found that ROM-3 is better model than ROM-2 and ROM-1. For predicting thermal drawdown in EGS applications, where high fracture zone permeabilities (typically greater than 10 –15 m 2) are desired, ROM-2 and ROM-3 outperform ROM-1. As per computational time, all the ROMs are 10 4 times faster when compared to running a high-fidelity numerical simulation. In conclusion, this makes the proposed regression-based ROMs attractive for real-time EGS applications because they are fast and provide reasonably good predictions for thermal power output.« less

Regression-based reduced-order models to predict transient thermal output for enhanced geothermal systems

DOE PAGES

Mudunuru, Maruti Kumar; Karra, Satish; Harp, Dylan Robert; ...

2017-07-10

Reduced-order modeling is a promising approach, as many phenomena can be described by a few parameters/mechanisms. An advantage and attractive aspect of a reduced-order model is that it is computational inexpensive to evaluate when compared to running a high-fidelity numerical simulation. A reduced-order model takes couple of seconds to run on a laptop while a high-fidelity simulation may take couple of hours to run on a high-performance computing cluster. The goal of this paper is to assess the utility of regression-based reduced-order models (ROMs) developed from high-fidelity numerical simulations for predicting transient thermal power output for an enhanced geothermal reservoirmore » while explicitly accounting for uncertainties in the subsurface system and site-specific details. Numerical simulations are performed based on equally spaced values in the specified range of model parameters. Key sensitive parameters are then identified from these simulations, which are fracture zone permeability, well/skin factor, bottom hole pressure, and injection flow rate. We found the fracture zone permeability to be the most sensitive parameter. The fracture zone permeability along with time, are used to build regression-based ROMs for the thermal power output. The ROMs are trained and validated using detailed physics-based numerical simulations. Finally, predictions from the ROMs are then compared with field data. We propose three different ROMs with different levels of model parsimony, each describing key and essential features of the power production curves. The coefficients in the proposed regression-based ROMs are developed by minimizing a non-linear least-squares misfit function using the Levenberg–Marquardt algorithm. The misfit function is based on the difference between numerical simulation data and reduced-order model. ROM-1 is constructed based on polynomials up to fourth order. ROM-1 is able to accurately reproduce the power output of numerical simulations for low values of permeabilities and certain features of the field-scale data. ROM-2 is a model with more analytical functions consisting of polynomials up to order eight, exponential functions and smooth approximations of Heaviside functions, and accurately describes the field-data. At higher permeabilities, ROM-2 reproduces numerical results better than ROM-1, however, there is a considerable deviation from numerical results at low fracture zone permeabilities. ROM-3 consists of polynomials up to order ten, and is developed by taking the best aspects of ROM-1 and ROM-2. ROM-1 is relatively parsimonious than ROM-2 and ROM-3, while ROM-2 overfits the data. ROM-3 on the other hand, provides a middle ground for model parsimony. Based on R 2-values for training, validation, and prediction data sets we found that ROM-3 is better model than ROM-2 and ROM-1. For predicting thermal drawdown in EGS applications, where high fracture zone permeabilities (typically greater than 10 –15 m 2) are desired, ROM-2 and ROM-3 outperform ROM-1. As per computational time, all the ROMs are 10 4 times faster when compared to running a high-fidelity numerical simulation. In conclusion, this makes the proposed regression-based ROMs attractive for real-time EGS applications because they are fast and provide reasonably good predictions for thermal power output.« less

Legal Issues and Statistical Approaches to Reverse Pay Discrimination in Higher Education

ERIC Educational Resources Information Center

Eckes, Suzanne E.; Toutkoushian, Robert K.

2006-01-01

There have been numerous lawsuits within higher education brought by females over pay inequity and many articles have been written on the topic. Although not as prevalent, there have been some recent instances where male faculty have claimed--with some degree of success--that the process used by their institutions to make salary adjustments for…

Statistical Mechanics and Dynamics of the Outer Solar System.I. The Jupiter/Saturn Zone

NASA Technical Reports Server (NTRS)

Grazier, K. R.; Newman, W. I.; Kaula, W. M.; Hyman, J. M.

1996-01-01

We report on numerical simulations designed to understand how the solar system evolved through a winnowing of planetesimals accreeted from the early solar nebula. This sorting process is driven by the energy and angular momentum and continues to the present day. We reconsider the existence and importance of stable niches in the Jupiter/Saturn Zone using greatly improved numerical techniques based on high-order optimized multi-step integration schemes coupled to roundoff error minimizing methods.

Microstructure based procedure for process parameter control in rolling of aluminum thin foils

NASA Astrophysics Data System (ADS)

Johannes, Kronsteiner; Kabliman, Evgeniya; Klimek, Philipp-Christoph

2018-05-01

In present work, a microstructure based procedure is used for a numerical prediction of strength properties for Al-Mg-Sc thin foils during a hot rolling process. For this purpose, the following techniques were developed and implemented. At first, a toolkit for a numerical analysis of experimental stress-strain curves obtained during a hot compression testing by a deformation dilatometer was developed. The implemented techniques allow for the correction of a temperature increase in samples due to adiabatic heating and for the determination of a yield strength needed for the separation of the elastic and plastic deformation regimes during numerical simulation of multi-pass hot rolling. At the next step, an asymmetric Hot Rolling Simulator (adjustable table inlet/outlet height as well as separate roll infeed) was developed in order to match the exact processing conditions of a semi-industrial rolling procedure. At each element of a finite element mesh the total strength is calculated by in-house Flow Stress Model based on evolution of mean dislocation density. The strength values obtained by numerical modelling were found in a reasonable agreement with results of tensile tests for thin Al-Mg-Sc foils. Thus, the proposed simulation procedure might allow to optimize the processing parameters with respect to the microstructure development.

Diagnostics of seeded RF plasmas: An experimental study related to the gaseous core reactor

NASA Technical Reports Server (NTRS)

Thompson, S. D.; Clement, J. D.; Williams, J. R.

1974-01-01

Measurements of the temperature profiles in an RF argon plasma were made over magnetic field intensities ranging from 20 amp turns/cm to 80 amp turns/cm. The results were compared with a one-dimensional numerical treatment of the governing equations and with an approximate closed form analytical solution that neglected radiation losses. The average measured temperatures in the plasma compared well with the numerical treatment, though the experimental profile showed less of an off center temperature peak than predicted by theory. This may be a result of the complex turbulent flow pattern present in the experimental torch and not modeled in the numerical treatment. The radiation term cannot be neglected for argon at the power levels investigated. The closed form analytical approximation that neglected radiation led to temperature predictions on the order of 1000 K to 2000 K higher than measured or predicted by the numerical treatment which considered radiation losses.

Distribution of maternal age and birth order groups in cases with unclassified multiple congenital abnormalities according to the number of component abnormalities: a national population-based case-control study.

PubMed

Csermely, Gyula; Czeizel, Andrew E; Veszprémi, Béla

2015-02-01

Multiple congenital abnormalities are caused by chromosomal aberrations, mutant major genes and teratogens. A minor proportion of these patients are identified as syndromes but the major part belonging to the group of unclassified multiple CAs (UMCAs). The main objective of this study was to evaluate the maternal age and birth order in pregnant women who had offspring affected with UMCA. The strong association between numerical chromosomal aberrations, e.g., Down syndrome and advanced maternal age is well-known and tested here. The Hungarian Case-Control Surveillance of Congenital Abnormalities, 1980 to 1996, yielded a large population-based national data set with 22,843 malformed newborns or fetuses ("informative cases") included 1349 UMCA cases with their 2407 matched controls. Case-control comparison of maternal age and birth order was made for cases with UMCA, stratified by component numbers and their controls. In addition, 834 cases with Down syndrome were compared to 1432 matched controls. The well-known advanced maternal age with the higher risk for Down syndrome was confirmed. The findings of the study suggest that the young age of mothers associates with the higher risk of UMCA, in addition birth order 4 or more associates with the higher risk for UMCA with 2 and 3 component CAs. This study was the first to analyze the possible maternal and birth order effect for cases with UMCA, and the young age and higher birth order associated with a higher risk for UMCA. © 2014 Wiley Periodicals, Inc.

Universality of the logarithmic velocity profile restored

NASA Astrophysics Data System (ADS)

Luchini, Paolo

2017-11-01

The logarithmic velocity profile of wall-bounded turbulent flow, despite its widespread adoption in research and in teaching, exhibits discrepancies with both experiments and numerical simulations that have been repeatedly observed in the literature; serious doubts ensued about its precise form and universality, leading to the formulation of alternate theories and hindering ongoing experimental efforts to measure von Kármán's constant. By comparing different geometries of pipe, plane-channel and plane-Couette flow, here we show that such discrepancies can be physically interpreted, and analytically accounted for, through an equally universal higher-order correction caused by the pressure gradient. Inclusion of this term produces a tenfold increase in the adherence of the predicted profile to existing experiments and numerical simulations in all three geometries. Universality of the logarithmic law then emerges beyond doubt and a satisfactorily simple formulation is established. Among the consequences of this formulation is a strongly increased confidence that the Reynolds number of present-day direct numerical simulations is actually high enough to uncover asymptotic behaviour, but research efforts are still needed in order to increase their accuracy.

Strong higher-order resonant contributions to x-ray line polarization in hot plasmas

NASA Astrophysics Data System (ADS)

Shah, Chintan; Amaro, Pedro; Steinbrügge, Rene; Beilmann, Christian; Bernitt, Sven; Fritzsche, Stephan; Surzhykov, Andrey; Crespo López-Urrutia, José R.; Tashenov, Stanislav

2016-06-01

We studied angular distributions of x rays emitted in resonant recombination of highly charged iron and krypton ions, resolving dielectronic, trielectronic, and quadruelectronic channels. A tunable electron beam drove these processes, inducing x rays registered by two detectors mounted along and perpendicular to the beam axis. The measured emission asymmetries comprehensively benchmarked full-order atomic calculations. We conclude that accurate polarization diagnostics of hot plasmas can only be obtained under the premise of inclusion of higher-order processes that were neglected in earlier work.

5 CFR 302.304 - Order of consideration.

Code of Federal Regulations, 2012 CFR

2012-01-01

... States Code, in the order of his/her numerical ranking. (ii) The name of each other qualified applicant in the order of his/her numerical ranking. (2) Order B. (i) The name of each qualified preference...'s reemployment list, in the order of his/her numerical ranking. (ii) The name of each qualified...

5 CFR 302.304 - Order of consideration.

Code of Federal Regulations, 2011 CFR

2011-01-01

... States Code, in the order of his/her numerical ranking. (ii) The name of each other qualified applicant in the order of his/her numerical ranking. (2) Order B. (i) The name of each qualified preference...'s reemployment list, in the order of his/her numerical ranking. (ii) The name of each qualified...

5 CFR 302.304 - Order of consideration.

Code of Federal Regulations, 2014 CFR

2014-01-01

... States Code, in the order of his/her numerical ranking. (ii) The name of each other qualified applicant in the order of his/her numerical ranking. (2) Order B. (i) The name of each qualified preference...'s reemployment list, in the order of his/her numerical ranking. (ii) The name of each qualified...

5 CFR 302.304 - Order of consideration.

Code of Federal Regulations, 2013 CFR

2013-01-01

... States Code, in the order of his/her numerical ranking. (ii) The name of each other qualified applicant in the order of his/her numerical ranking. (2) Order B. (i) The name of each qualified preference...'s reemployment list, in the order of his/her numerical ranking. (ii) The name of each qualified...

Multigrid methods for numerical simulation of laminar diffusion flames

NASA Technical Reports Server (NTRS)

Liu, C.; Liu, Z.; Mccormick, S.

1993-01-01

This paper documents the result of a computational study of multigrid methods for numerical simulation of 2D diffusion flames. The focus is on a simplified combustion model, which is assumed to be a single step, infinitely fast and irreversible chemical reaction with five species (C3H8, O2, N2, CO2 and H2O). A fully-implicit second-order hybrid scheme is developed on a staggered grid, which is stretched in the streamwise coordinate direction. A full approximation multigrid scheme (FAS) based on line distributive relaxation is developed as a fast solver for the algebraic equations arising at each time step. Convergence of the process for the simplified model problem is more than two-orders of magnitude faster than other iterative methods, and the computational results show good grid convergence, with second-order accuracy, as well as qualitatively agreement with the results of other researchers.

Higher-order derivative correlations and the alignment of small-scale structures in isotropic numerical turbulence

NASA Technical Reports Server (NTRS)

Kerr, R. A.

1983-01-01

In a three dimensional simulation higher order derivative correlations, including skewness and flatness factors, are calculated for velocity and passive scalar fields and are compared with structures in the flow. The equations are forced to maintain steady state turbulence and collect statistics. It is found that the scalar derivative flatness increases much faster with Reynolds number than the velocity derivative flatness, and the velocity and mixed derivative skewness do not increase with Reynolds number. Separate exponents are found for the various fourth order velocity derivative correlations, with the vorticity flatness exponent the largest. Three dimensional graphics show strong alignment between the vorticity, rate of strain, and scalar-gradient fields. The vorticity is concentrated in tubes with the scalar gradient and the largest principal rate of strain aligned perpendicular to the tubes. Velocity spectra, in Kolmogorov variables, collapse to a single curve and a short minus 5/3 spectral regime is observed.

Nonlinear spline wavefront reconstruction through moment-based Shack-Hartmann sensor measurements.

PubMed

Viegers, M; Brunner, E; Soloviev, O; de Visser, C C; Verhaegen, M

2017-05-15

We propose a spline-based aberration reconstruction method through moment measurements (SABRE-M). The method uses first and second moment information from the focal spots of the SH sensor to reconstruct the wavefront with bivariate simplex B-spline basis functions. The proposed method, since it provides higher order local wavefront estimates with quadratic and cubic basis functions can provide the same accuracy for SH arrays with a reduced number of subapertures and, correspondingly, larger lenses which can be beneficial for application in low light conditions. In numerical experiments the performance of SABRE-M is compared to that of the first moment method SABRE for aberrations of different spatial orders and for different sizes of the SH array. The results show that SABRE-M is superior to SABRE, in particular for the higher order aberrations and that SABRE-M can give equal performance as SABRE on a SH grid of halved sampling.

Higher Order Bases in a 2D Hybrid BEM/FEM Formulation

NASA Technical Reports Server (NTRS)

Fink, Patrick W.; Wilton, Donald R.

2002-01-01

The advantages of using higher order, interpolatory basis functions are examined in the analysis of transverse electric (TE) plane wave scattering by homogeneous, dielectric cylinders. A boundary-element/finite-element (BEM/FEM) hybrid formulation is employed in which the interior dielectric region is modeled with the vector Helmholtz equation, and a radiation boundary condition is supplied by an Electric Field Integral Equation (EFIE). An efficient method of handling the singular self-term arising in the EFIE is presented. The iterative solution of the partially dense system of equations is obtained using the Quasi-Minimal Residual (QMR) algorithm with an Incomplete LU Threshold (ILUT) preconditioner. Numerical results are shown for the case of an incident wave impinging upon a square dielectric cylinder. The convergence of the solution is shown versus the number of unknowns as a function of the completeness order of the basis functions.

Radiation Heat Transfer Between Diffuse-Gray Surfaces Using Higher Order Finite Elements

NASA Technical Reports Server (NTRS)

Gould, Dana C.

2000-01-01

This paper presents recent work on developing methods for analyzing radiation heat transfer between diffuse-gray surfaces using p-version finite elements. The work was motivated by a thermal analysis of a High Speed Civil Transport (HSCT) wing structure which showed the importance of radiation heat transfer throughout the structure. The analysis also showed that refining the finite element mesh to accurately capture the temperature distribution on the internal structure led to very large meshes with unacceptably long execution times. Traditional methods for calculating surface-to-surface radiation are based on assumptions that are not appropriate for p-version finite elements. Two methods for determining internal radiation heat transfer are developed for one and two-dimensional p-version finite elements. In the first method, higher-order elements are divided into a number of sub-elements. Traditional methods are used to determine radiation heat flux along each sub-element and then mapped back to the parent element. In the second method, the radiation heat transfer equations are numerically integrated over the higher-order element. Comparisons with analytical solutions show that the integration scheme is generally more accurate than the sub-element method. Comparison to results from traditional finite elements shows that significant reduction in the number of elements in the mesh is possible using higher-order (p-version) finite elements.

Impact of Tidal-Stream Turbines on the Generation of the Higher Tidal Harmonics

NASA Astrophysics Data System (ADS)

Potter, Daniel; Ilic, Suzana; Folkard, Andrew

2016-04-01

The higher tidal harmonics result from the interaction of the astronomic tides with both themselves and each other through non-linear processes. In shallower waters such as those near the coast these non-linear processes become more significant and thus, so too do the higher tidal harmonics become more significant. The interaction of the tide with tidal-stream turbines (TSTs), through thrust and drag processes will be non-linear and as such will contribute to the generation of higher tidal harmonics, thus changing the nature of the tide downstream of the turbines. The change to the tide may potentially impact on the downstream energy resource (Robins et al. 2015) and sediment transport processes (Pingree & Griffiths 1979). This paper will present analytical results, which suggest that TSTs will impact on the generation of all higher harmonics but with odd overtides being impacted more than even overtides, the most important examples of which are the M6 and M4 tides respectively, which are the first odd and even overtides of the M2 tide. Change in phase and amplitude of the M6 tide by TSTs will distort the tide but will not cause an asymmetry between the flood and ebb of the tide. Change in the phase and amplitude of the M4 can not only distort the tide but also cause asymmetry. Hence any change to the M4 tide by the turbines is more significant, despite the magnitude of change to the M6 being greater. In order to gain a fuller understanding of the way in which TSTs change the tide downstream and the significance of any change for transport processes or energy resource, a numerical modelling study will be carried out, which will be presented in a future paper. Robins, P.E., Neill, S.P., Lewis, M. & Ward, S.L., 2015. Characterising the spatial and temporal variability of the tidal-stream energy resource over the northwest European shelf seas. Applied Energy, 147: 510-522. Pingree, R.D. & Griffiths, D.K., 1979. Sand transport paths around the British Isles resulting from M2 and M4 tidal interactions. J. Mar. Biol. Ass. U.K., 59: 497-513

Numerical tests of local scale invariance in ageing q-state Potts models

NASA Astrophysics Data System (ADS)

Lorenz, E.; Janke, W.

2007-01-01

Much effort has been spent over the last years to achieve a coherent theoretical description of ageing as a non-linear dynamics process. Long supposed to be a consequence of the slow dynamics of glassy systems only, ageing phenomena could also be identified in the phase-ordering kinetics of simple ferromagnets. As a phenomenological approach Henkel et al. developed a group of local scale transformations under which two-time autocorrelation and response functions should transform covariantly. This work is to extend previous numerical tests of the predicted scaling functions for the Ising model by Monte Carlo simulations of two-dimensional q-state Potts models with q=3 and 8, which, in equilibrium, undergo temperature-driven phase transitions of second and first order, respectively.

The effect of low-frequency oscillations on cardio-respiratory synchronization. Observations during rest and exercise

NASA Astrophysics Data System (ADS)

Kenwright, D. A.; Bahraminasab, A.; Stefanovska, A.; McClintock, P. V. E.

2008-10-01

We show that the transitions which occur between close orders of synchronization in the cardiorespiratory system are mainly due to modulation of the cardiac and respiratory processes by low-frequency components. The experimental evidence is derived from recordings on healthy subjects at rest and during exercise. Exercise acts as a perturbation of the system that alters the mean cardiac and respiratory frequencies and changes the amount of their modulation by low-frequency oscillations. The conclusion is supported by numerical evidence based on a model of phase-coupled oscillators, with white noise and lowfrequency noise. Both the experimental and numerical approaches confirm that low-frequency oscillations play a significant role in the transitional behavior between close orders of synchronization.

A reduced-order model for compressible flows with buffeting condition using higher order dynamic mode decomposition with a mode selection criterion

NASA Astrophysics Data System (ADS)

Kou, Jiaqing; Le Clainche, Soledad; Zhang, Weiwei

2018-01-01

This study proposes an improvement in the performance of reduced-order models (ROMs) based on dynamic mode decomposition to model the flow dynamics of the attractor from a transient solution. By combining higher order dynamic mode decomposition (HODMD) with an efficient mode selection criterion, the HODMD with criterion (HODMDc) ROM is able to identify dominant flow patterns with high accuracy. This helps us to develop a more parsimonious ROM structure, allowing better predictions of the attractor dynamics. The method is tested in the solution of a NACA0012 airfoil buffeting in a transonic flow, and its good performance in both the reconstruction of the original solution and the prediction of the permanent dynamics is shown. In addition, the robustness of the method has been successfully tested using different types of parameters, indicating that the proposed ROM approach is a tool promising for using in both numerical simulations and experimental data.

Impact of Separation Distance on Multi-Vane Radiometer Configurations

NASA Astrophysics Data System (ADS)

Cornella, B. M.; Ketsdever, A. D.; Gimelshein, N. E.; Gimelshein, S. F.

2011-05-01

The radiometric force produced by a linear array of three radiometer vanes has been assessed numerically using an argon carrier gas and experimentally using air. The separation distance between the three vanes of the array was varied between 0 and 120 percent based on the height of an individual radiometer vane of 40 mm. Qualitative agreement between the numerical and experimental results is shown as a function of operating Knudsen number, vane separation distance, and surrounding chamber geometry. Both sets of results indicate an asymptotic trend in maximum force as the separation distance increases as well as a shift in the maximum force Knudsen number. Small chamber effects for both numerical and experimental results indicate an increase of the total force ranging from a factor of 2.5 to 4. Quantitatively, however, the numerical simulations yield forces approximately an order of magnitude higher than observed in the experiments due to differences in carrier gas and accommodation coefficient as well as the two dimensional nature of the numerical simulations versus the three dimensional experiment.

Active vibration and noise control of vibro-acoustic system by using PID controller

NASA Astrophysics Data System (ADS)

Li, Yunlong; Wang, Xiaojun; Huang, Ren; Qiu, Zhiping

2015-07-01

Active control simulation of the acoustic and vibration response of a vibro-acoustic cavity of an airplane based on a PID controller is presented. A full numerical vibro-acoustic model is developed by using an Eulerian model, which is a coupled model based on the finite element formulation. The reduced order model, which is used to design the closed-loop control system, is obtained by the combination of modal expansion and variable substitution. Some physical experiments are made to validate and update the full-order and the reduced-order numerical models. Optimization of the actuator placement is employed in order to get an effective closed-loop control system. For the controller design, an iterative method is used to determine the optimal parameters of the PID controller. The process is illustrated by the design of an active noise and vibration control system for a cavity structure. The numerical and experimental results show that a PID-based active control system can effectively suppress the noise inside the cavity using a sound pressure signal as the controller input. It is also possible to control the noise by suppressing the vibration of the structure using the structural displacement signal as the controller input. For an airplane cavity structure, considering the issue of space-saving, the latter is more suitable.

Variable High Order Multiblock Overlapping Grid Methods for Mixed Steady and Unsteady Multiscale Viscous Flows

NASA Technical Reports Server (NTRS)

Sjogreen, Bjoern; Yee, H. C.

2007-01-01

Flows containing steady or nearly steady strong shocks in parts of the flow field, and unsteady turbulence with shocklets on other parts of the flow field are difficult to capture accurately and efficiently employing the same numerical scheme even under the multiblock grid or adaptive grid refinement framework. On one hand, sixth-order or higher shock-capturing methods are appropriate for unsteady turbulence with shocklets. On the other hand, lower order shock-capturing methods are more effective for strong steady shocks in terms of convergence. In order to minimize the shortcomings of low order and high order shock-capturing schemes for the subject flows,a multi- block overlapping grid with different orders of accuracy on different blocks is proposed. Test cases to illustrate the performance of the new solver are included.

You can count on the motor cortex: Finger counting habits modulate motor cortex activation evoked by numbers

PubMed Central

Tschentscher, Nadja; Hauk, Olaf; Fischer, Martin H.; Pulvermüller, Friedemann

2012-01-01

The embodied cognition framework suggests that neural systems for perception and action are engaged during higher cognitive processes. In an event-related fMRI study, we tested this claim for the abstract domain of numerical symbol processing: is the human cortical motor system part of the representation of numbers, and is organization of numerical knowledge influenced by individual finger counting habits? Developmental studies suggest a link between numerals and finger counting habits due to the acquisition of numerical skills through finger counting in childhood. In the present study, digits 1 to 9 and the corresponding number words were presented visually to adults with different finger counting habits, i.e. left- and right-starters who reported that they usually start counting small numbers with their left and right hand, respectively. Despite the absence of overt hand movements, the hemisphere contralateral to the hand used for counting small numbers was activated when small numbers were presented. The correspondence between finger counting habits and hemispheric motor activation is consistent with an intrinsic functional link between finger counting and number processing. PMID:22133748

Potential predictability and forecast skill in ensemble climate forecast: a skill-persistence rule

NASA Astrophysics Data System (ADS)

Jin, Yishuai; Rong, Xinyao; Liu, Zhengyu

2017-12-01

This study investigates the factors relationship between the forecast skills for the real world (actual skill) and perfect model (perfect skill) in ensemble climate model forecast with a series of fully coupled general circulation model forecast experiments. It is found that the actual skill for sea surface temperature (SST) in seasonal forecast is substantially higher than the perfect skill on a large part of the tropical oceans, especially the tropical Indian Ocean and the central-eastern Pacific Ocean. The higher actual skill is found to be related to the higher observational SST persistence, suggesting a skill-persistence rule: a higher SST persistence in the real world than in the model could overwhelm the model bias to produce a higher forecast skill for the real world than for the perfect model. The relation between forecast skill and persistence is further proved using a first-order autoregressive model (AR1) analytically for theoretical solutions and numerically for analogue experiments. The AR1 model study shows that the skill-persistence rule is strictly valid in the case of infinite ensemble size, but could be distorted by sampling errors and non-AR1 processes. This study suggests that the so called "perfect skill" is model dependent and cannot serve as an accurate estimate of the true upper limit of real world prediction skill, unless the model can capture at least the persistence property of the observation.

Symbolic Processing Combined with Model-Based Reasoning

NASA Technical Reports Server (NTRS)

James, Mark

2009-01-01

A computer program for the detection of present and prediction of future discrete states of a complex, real-time engineering system utilizes a combination of symbolic processing and numerical model-based reasoning. One of the biggest weaknesses of a purely symbolic approach is that it enables prediction of only future discrete states while missing all unmodeled states or leading to incorrect identification of an unmodeled state as a modeled one. A purely numerical approach is based on a combination of statistical methods and mathematical models of the applicable physics and necessitates development of a complete model to the level of fidelity required for prediction. In addition, a purely numerical approach does not afford the ability to qualify its results without some form of symbolic processing. The present software implements numerical algorithms to detect unmodeled events and symbolic algorithms to predict expected behavior, correlate the expected behavior with the unmodeled events, and interpret the results in order to predict future discrete states. The approach embodied in this software differs from that of the BEAM methodology (aspects of which have been discussed in several prior NASA Tech Briefs articles), which provides for prediction of future measurements in the continuous-data domain.

Development of homotopy algorithms for fixed-order mixed H2/H(infinity) controller synthesis

NASA Technical Reports Server (NTRS)

Whorton, M.; Buschek, H.; Calise, A. J.

1994-01-01

A major difficulty associated with H-infinity and mu-synthesis methods is the order of the resulting compensator. Whereas model and/or controller reduction techniques are sometimes applied, performance and robustness properties are not preserved. By directly constraining compensator order during the optimization process, these properties are better preserved, albeit at the expense of computational complexity. This paper presents a novel homotopy algorithm to synthesize fixed-order mixed H2/H-infinity compensators. Numerical results are presented for a four-disk flexible structure to evaluate the efficiency of the algorithm.

Effect of higher order nonlinearity, directionality and finite water depth on wave statistics: Comparison of field data and numerical simulations

NASA Astrophysics Data System (ADS)

Fernández, Leandro; Monbaliu, Jaak; Onorato, Miguel; Toffoli, Alessandro

2014-05-01

This research is focused on the study of nonlinear evolution of irregular wave fields in water of arbitrary depth by comparing field measurements and numerical simulations.It is now well accepted that modulational instability, known as one of the main mechanisms for the formation of rogue waves, induces strong departures from Gaussian statistics. However, whereas non-Gaussian properties are remarkable when wave fields follow one direction of propagation over an infinite water depth, wave statistics only weakly deviate from Gaussianity when waves spread over a range of different directions. Over finite water depth, furthermore, wave instability attenuates overall and eventually vanishes for relative water depths as low as kh=1.36 (where k is the wavenumber of the dominant waves and h the water depth). Recent experimental results, nonetheless, seem to indicate that oblique perturbations are capable of triggering and sustaining modulational instability even if kh<1.36. In this regard, the aim of this research is to understand whether the combined effect of directionality and finite water depth has a significant effect on wave statistics and particularly on the occurrence of extremes. For this purpose, numerical experiments have been performed solving the Euler equation of motion with the Higher Order Spectral Method (HOSM) and compared with data of short crested wave fields for different sea states observed at the Lake George (Australia). A comparative analysis of the statistical properties (i.e. density function of the surface elevation and its statistical moments skewness and kurtosis) between simulations and in-situ data provides a confrontation between the numerical developments and real observations in field conditions.

Accurate Monotonicity - Preserving Schemes With Runge-Kutta Time Stepping

NASA Technical Reports Server (NTRS)

Suresh, A.; Huynh, H. T.

1997-01-01

A new class of high-order monotonicity-preserving schemes for the numerical solution of conservation laws is presented. The interface value in these schemes is obtained by limiting a higher-order polynominal reconstruction. The limiting is designed to preserve accuracy near extrema and to work well with Runge-Kutta time stepping. Computational efficiency is enhanced by a simple test that determines whether the limiting procedure is needed. For linear advection in one dimension, these schemes are shown as well as the Euler equations also confirm their high accuracy, good shock resolution, and computational efficiency.

Modeling the pyrolysis study of non-charring polymers under reduced pressure environments

NASA Astrophysics Data System (ADS)

Zong, Ruowen; Kang, Ruxue; Hu, Yanghui; Zhi, Youran

2018-04-01

In order to study the pyrolysis of non-charring polymers under reduced pressure environments, a series of experiments based on black acrylonitrile butadiene styrene (ABS) was conducted in a reduced pressure chamber under different external heat fluxes. The temperatures of the top surface and the bottom of the sample and the mass loss during the whole process were measured in real time. A one-dimensional numerical model was developed to predict the top surface and the bottom surface temperatures of ABS during the pyrolysis at different reduced pressures and external heat fluxes, and the model was validated by the experimental data. The results of the study indicate that the profiles of the top surface and the bottom surface temperatures are different at different pressures and heat fluxes. The temperature and the mass loss rate of the sample under a lower heat flux decreased significantly as the pressure was increased. However, under a higher heat flux, the temperature and the mass loss rate showed little sensitivity to the pressure. The simulated results fitted the experimental results better at the higher heat flux than at the lower heat flux.

Tsunami-induced boulder transport - combining physical experiments and numerical modelling

NASA Astrophysics Data System (ADS)

Oetjen, Jan; Engel, Max; May, Simon Matthias; Schüttrumpf, Holger; Brueckner, Helmut; Prasad Pudasaini, Shiva

2016-04-01

Coasts are crucial areas for living, economy, recreation, transportation, and various sectors of industry. Many of them are exposed to high-energy wave events. With regard to the ongoing population growth in low-elevation coastal areas, the urgent need for developing suitable management measures, especially for hazards like tsunamis, becomes obvious. These measures require supporting tools which allow an exact estimation of impact parameters like inundation height, inundation area, and wave energy. Focussing on tsunamis, geological archives can provide essential information on frequency and magnitude on a longer time scale in order to support coastal hazard management. While fine-grained deposits may quickly be altered after deposition, multi-ton coarse clasts (boulders) may represent an information source on past tsunami events with a much higher preservation potential. Applying numerical hydrodynamic coupled boulder transport models (BTM) is a commonly used approach to analyse characteristics (e.g. wave height, flow velocity) of the corresponding tsunami. Correct computations of tsunamis and the induced boulder transport can provide essential event-specific information, including wave heights, runup and direction. Although several valuable numerical models for tsunami-induced boulder transport exist (e. g. Goto et al., 2007; Imamura et al., 2008), some important basic aspects of both tsunami hydrodynamics and corresponding boulder transport have not yet been entirely understood. Therefore, our project aims at these questions in four crucial aspects of boulder transport by a tsunami: (i) influence of sediment load, (ii) influence of complex boulder shapes other than idealized rectangular shapes, (iii) momentum transfers between multiple boulders, and (iv) influence of non-uniform bathymetries and topographies both on tsunami and boulder. The investigation of these aspects in physical experiments and the correct implementation of an advanced model is an urgent need since they have been largely neglected. In order to tackle these gaps, we develop a novel BTM in two steps. First, scaled physical experiments are performed that determine the exact hydrodynamic processes within a tsunami during boulder transportations. Furthermore, the experiments are the basis for calibrating the numerical BTM. The BTM is based on the numerical two-phase mass flow model of Pudasaini (2012) that employs an advanced and unified high-resolution computational tool for mixtures consisting of the solid and fluid components and their interactions. This allows for the motion of the boulder while interacting with the particle-laden tsunami on the inundated coastal plane as a function of the total fluid and solid stresses. Our approach leads to fundamentally new insights in to the essential physical processes in BTM. Goto, K., Chavanich, S. A., Imamura, F., Kunthasap, P., Matsui, T., Minoura, K., Sugawara, D. and Yanagisawa, H.: Distribution, origin and transport process of boulders deposited by the 2004 Indian Ocean tsunami at Pakarang Cape, Thailand. Sediment. Geol., 202, 821-837, 2007. Imamura, F., Goto, K. and Ohkubo, S.: A numerical model of the transport of a boulder by tsunami. J. Geophys. Res. Oceans, 113, C01008, 2008. Pudasaini, S. P.: A general two-phase debris flow model. J. Geophys. Res. Earth Surf., 117, F03010, 2012.

Study on the extrusion of nickel-based spark plug electrodes by numerical simulation

NASA Astrophysics Data System (ADS)

Saby, Q.; Courbon, C.; Salvatore, F.; Fabre, D.; Romeyer, F.

2018-05-01

Interest in metal forming simulation has grown rapidly during the last decades and is now well established even in industry. It provides a flexible and relatively cheap method to perform sensitivity analyses, getting a better insight into the forming process and use it as an optimisation tool. As far as wear is concerned, numerical simulation can be seen as a relevant approach to assess the thermomechanical loadings applied to the active die surface and therefore predict their wear behaviour. In this study, a Finite-Element (FE) based model has been developed in order to investigate the cold forming process of a nickel-based sparkplug electrode. A fully thermo-mechanically coupled implicit formulation has been used in order to model the forward extrusion step with a special emphasis on the contact conditions at the workpiece-die interface. Contact pressure, relative sliding velocity and temperature profiles have been extracted versus time and qualitatively compared to the wear phenomena observed on the worn production dies.

Impact of the Test Device on the Behavior of the Acoustic Emission Signals: Contribution of the Numerical Modeling to Signal Processing

NASA Astrophysics Data System (ADS)

Issiaka Traore, Oumar; Cristini, Paul; Favretto-Cristini, Nathalie; Pantera, Laurent; Viguier-Pla, Sylvie

2018-01-01

In a context of nuclear safety experiment monitoring with the non destructive testing method of acoustic emission, we study the impact of the test device on the interpretation of the recorded physical signals by using spectral finite element modeling. The numerical results are validated by comparison with real acoustic emission data obtained from previous experiments. The results show that several parameters can have significant impacts on acoustic wave propagation and then on the interpretation of the physical signals. The potential position of the source mechanism, the positions of the receivers and the nature of the coolant fluid have to be taken into account in the definition a pre-processing strategy of the real acoustic emission signals. In order to show the relevance of such an approach, we use the results to propose an optimization of the positions of the acoustic emission sensors in order to reduce the estimation bias of the time-delay and then improve the localization of the source mechanisms.

Numerical and Experimental Investigations of Humping Phenomena in Laser Micro Welding

NASA Astrophysics Data System (ADS)

Otto, Andreas; Patschger, Andreas; Seiler, Michael

The Humping effect is a phenomenon which is observed approximately since 50 years in various welding procedures and is characterized by droplets due to a pile-up of the melt pool. It occurs within a broad range of process parameters. Particularly during micro welding, humping effect is critical due to typically high feed rates. In the past, essentially two approaches (fluid-dynamic approach of streaming melt within the molten pool and the Plateau-Rayleigh instability of a liquid jet) were discussed in order to explain the occurrence of the humping effect. But none of both can fully explain all observed effects. For this reason, experimental studies in micro welding of thin metal foils were performed in order to determine the influence of process parameters on the occurrence of humping effects. The experimental observations were compared with results from numerical multi-physical simulations (incorporating beam propagation, incoupling, heat transfer, fluid dynamics etc.) to provide a deeper understanding of the causes for hump formation.

77 FR 19044 - Self-Regulatory Organizations; the NASDAQ Stock Market LLC; Notice of Filing and Immediate...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-29

... that the quality of its process for commencing IPO trading would be enhanced by allowing market... orders being entered prior to commencement of trading, resulting in a higher level of order interaction... commencement of trading of IPO securities, resulting in a higher level of order interaction at the open. Thus...

Analysis of factors influencing the bond strength in roll bonding processes

NASA Astrophysics Data System (ADS)

Khaledi, Kavan; Wulfinghoff, Stephan; Reese, Stefanie

2018-05-01

Cold Roll Bonding (CRB) is recognized as an industrial technique in which the metal sheets are joined together in order to produce laminate metal composites. In this technique, a metallurgical bond resulting from severe plastic deformation is formed between the rolled metallic layers. The main objective of this paper is to analyse different factors which may affect the bond formation in rolling processes. To achieve this goal, first, an interface model is employed which describes both the bonding and debonding. In this model, the bond strength evolution between the metallic layers is calculated based on the film theory of bonding. On the other hand, the debonding process is modelled by means of a bilinear cohesive zone model. In the numerical section, different scenarios are taken into account to model the roll bonding process of metal sheets. The numerical simulation includes the modelling of joining during the roll bonding process followed by debonding in a Double Cantilever Beam (DCB) peeling test. In all simulations, the metallic layers are regarded as elastoplastic materials subjected to large plastic deformations. Finally, the effects of some important factors on the bond formation are numerically investigated.