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Sample records for conservative difference schemes

  1. Two Conservative Difference Schemes for Rosenau-Kawahara Equation

    Directory of Open Access Journals (Sweden)

    Jinsong Hu

    2014-01-01

    Full Text Available Two conservative finite difference schemes for the numerical solution of the initialboundary value problem of Rosenau-Kawahara equation are proposed. The difference schemes simulate two conservative quantities of the problem well. The existence and uniqueness of the difference solution are proved. It is shown that the finite difference schemes are of second-order convergence and unconditionally stable. Numerical experiments verify the theoretical results.

  2. Conservative Linear Difference Scheme for Rosenau-KdV Equation

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    Jinsong Hu

    2013-01-01

    Full Text Available A conservative three-level linear finite difference scheme for the numerical solution of the initial-boundary value problem of Rosenau-KdV equation is proposed. The difference scheme simulates two conservative quantities of the problem well. The existence and uniqueness of the difference solution are proved. It is shown that the finite difference scheme is of second-order convergence and unconditionally stable. Numerical experiments verify the theoretical results.

  3. AN EXPLICIT MULTI-CONSERVATION FINITE-DIFFERENCE SCHEME FOR SHALLOW-WATER-WAVE EQUATION

    Institute of Scientific and Technical Information of China (English)

    Bin Wang

    2008-01-01

    An explicit multi-conservation finite-difference scheme for solving the spherical shallowwater-wave equation set of barotropic atmosphere has been proposed. The numerical scheme is based on a special semi-discrete form of the equations that conserves four basic physical integrals including the total energy, total mass, total potential vorticity and total enstrophy. Numerical tests show that the new scheme performs closely like but is much more time-saving than the implicit multi-conservation scheme.

  4. A High-Accuracy Linear Conservative Difference Scheme for Rosenau-RLW Equation

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    Jinsong Hu

    2013-01-01

    Full Text Available We study the initial-boundary value problem for Rosenau-RLW equation. We propose a three-level linear finite difference scheme, which has the theoretical accuracy of Oτ2+h4. The scheme simulates two conservative properties of original problem well. The existence, uniqueness of difference solution, and a priori estimates in infinite norm are obtained. Furthermore, we analyze the convergence and stability of the scheme by energy method. At last, numerical experiments demonstrate the theoretical results.

  5. High-Order Entropy Stable Finite Difference Schemes for Nonlinear Conservation Laws: Finite Domains

    Science.gov (United States)

    Fisher, Travis C.; Carpenter, Mark H.

    2013-01-01

    Developing stable and robust high-order finite difference schemes requires mathematical formalism and appropriate methods of analysis. In this work, nonlinear entropy stability is used to derive provably stable high-order finite difference methods with formal boundary closures for conservation laws. Particular emphasis is placed on the entropy stability of the compressible Navier-Stokes equations. A newly derived entropy stable weighted essentially non-oscillatory finite difference method is used to simulate problems with shocks and a conservative, entropy stable, narrow-stencil finite difference approach is used to approximate viscous terms.

  6. A new fifth order finite difference WENO scheme for solving hyperbolic conservation laws

    Science.gov (United States)

    Zhu, Jun; Qiu, Jianxian

    2016-08-01

    In this paper a new simple fifth order weighted essentially non-oscillatory (WENO) scheme is presented in the finite difference framework for solving the hyperbolic conservation laws. The new WENO scheme is a convex combination of a fourth degree polynomial with two linear polynomials in a traditional WENO fashion. This new fifth order WENO scheme uses the same five-point information as the classical fifth order WENO scheme [14,20], could get less absolute truncation errors in L1 and L∞ norms, and obtain the same accuracy order in smooth region containing complicated numerical solution structures simultaneously escaping nonphysical oscillations adjacent strong shocks or contact discontinuities. The associated linear weights are artificially set to be any random positive numbers with the only requirement that their sum equals one. New nonlinear weights are proposed for the purpose of sustaining the optimal fifth order accuracy. The new WENO scheme has advantages over the classical WENO scheme [14,20] in its simplicity and easy extension to higher dimensions. Some benchmark numerical tests are performed to illustrate the capability of this new fifth order WENO scheme.

  7. The Harmonious Dissipative Operators and the Completely Square Conservative Difference Scheme in an Explicit Way

    Institute of Scientific and Technical Information of China (English)

    王斌; 季仲贞

    1994-01-01

    In this paper, a new definition on harmonious dissipative operators is given and some important properties of theirs are shown. Especially, the relationship between a harmonious dissipative operator and the completely square conservative difference scheme in an explicit way is revealed. Kinds of 2-order, 3-order and 4-order harmonious dissipative operators are constructed by using the traditional Runge-Kutta method and a species of general m-order harmonious dissipative operators is established in the linear case. In addition, an efficiency parameter to appraise the time benefits of a harmonious dissipative operator is defined in this paper. It is testified in numerical tests that the harmonious dissipative operators are indeed able to improve the time-efficiency and computational effect of the completely square conservative difference scheme in an explicit way.

  8. Cost-effectiveness of conservation payment schemes for species with different range sizes.

    Science.gov (United States)

    Drechsler, Martin; Smith, Henrik G; Sturm, Astrid; Wätzold, Frank

    2016-08-01

    Payments to compensate landowners for carrying out costly land-use measures that benefit endangered biodiversity have become an important policy instrument. When designing such payments, it is important to take into account that spatially connected habitats are more valuable for many species than isolated ones. One way to incentivize provision of connected habitats is to offer landowners an agglomeration bonus, that is, a bonus on top of payments they are receiving to conserve land if the land is spatially connected. Researchers have compared the cost-effectiveness of the agglomeration bonus with 2 alternatives: an all-or-nothing, agglomeration payment, where landowners receive a payment only if the conserved land parcels have a certain level of spatial connectivity, and a spatially homogeneous payment, where landowners receive a payment for conserved land parcels irrespective of their location. Their results show the agglomeration bonus is rarely the most cost-effective option, and when it is, it is only slightly better than one of the alternatives. This suggests that the agglomeration bonus should not be given priority as a policy design option. However, this finding is based on consideration of only 1 species. We examined whether the same applied to 2 species, one for which the homogeneous payment is best and the other for which the agglomeration payment is most cost-effective. We modified a published conceptual model so that we were able to assess the cost-effectiveness of payment schemes for 2 species and applied it to a grassland bird and a grassland butterfly in Germany that require the same habitat but have different spatial-connectivity needs. When conserving both species, the agglomeration bonus was more cost-effective than the agglomeration and the homogeneous payment; thus, we showed that as a policy the agglomeration bonus is a useful conservation-payment option. © 2016 Society for Conservation Biology.

  9. On a consistent high-order finite difference scheme with kinetic energy conservation for simulating turbulent reacting flows

    Science.gov (United States)

    Trisjono, Philipp; Kang, Seongwon; Pitsch, Heinz

    2016-12-01

    The main objective of this study is to present an accurate and consistent numerical framework for turbulent reacting flows based on a high-order finite difference (HOFD) scheme. It was shown previously by Desjardins et al. (2008) [4] that a centered finite difference scheme discretely conserving the kinetic energy and an upwind-biased scheme for the scalar transport can be combined into a useful scheme for turbulent reacting flows. With a high-order spatial accuracy, however, an inconsistency among discretization schemes for different conservation laws is identified, which can disturb a scalar field spuriously under non-uniform density distribution. Various theoretical and numerical analyses are performed on the sources of the unphysical error. From this, the derivative of the mass-conserving velocity and the local Péclet number are identified as the primary factors affecting the error. As a solution, an HOFD stencil for the mass conservation is reformulated into a flux-based form that can be used consistently with an upwind-biased scheme for the scalar transport. The effectiveness of the proposed formulation is verified using two-dimensional laminar flows such as a scalar transport problem and a laminar premixed flame, where unphysical oscillations in the scalar fields are removed. The applicability of the proposed scheme is demonstrated in an LES of a turbulent stratified premixed flame.

  10. Convergence of finite differences schemes for viscous and inviscid conservation laws with rough coefficients

    Energy Technology Data Exchange (ETDEWEB)

    Karlsen, Kenneth Hvistendal; Risebro, Nils Henrik

    2000-09-01

    We consider the initial value problem for degenerate viscous and inviscid scalar conservation laws where the flux function depends on the spatial location through a ''rough'' coefficient function k(x). we show that the Engquist-Osher (and hence all monotone) finite difference approximations converge to the unique entropy solution of the governing equation if, among other demands, k' is in BV, thereby providing alternative (new) existence proofs for entropy solutions of degenerate convection-diffusion equations as well as new convergence results for their finite difference approximations. In the inviscid case, we also provide a rate of convergence. Our convergence proofs are based on deriving a series of a priori estimates and using a general L{sup p} compactness criterion. (author)

  11. The Using of Conservation Laws in Symmetry-Preserving Difference Scheme

    Institute of Scientific and Technical Information of China (English)

    XIN Xiang-Peng; CHEN Yong

    2013-01-01

    In this paper,by means of the potential systems of the giyen nonlinear evolution equations,a procedure of symmetry preserving discretization of differential equations is presented.The specific process will be given detailed in sec0tion 2.This extended method is effective for discreting the high-order (high-dimensional) nonlinear evolution equations.As examples,the invariant difference models of the mKdV equation and the Boussinesq equation are constructed.

  12. Assessment of some high-order finite difference schemes on the scalar conservation law with periodical conditions

    Directory of Open Access Journals (Sweden)

    Alina BOGOI

    2016-12-01

    Full Text Available Supersonic/hypersonic flows with strong shocks need special treatment in Computational Fluid Dynamics (CFD in order to accurately capture the discontinuity location and his magnitude. To avoid numerical instabilities in the presence of discontinuities, the numerical schemes must generate low dissipation and low dispersion error. Consequently, the algorithms used to calculate the time and space-derivatives, should exhibit a low amplitude and phase error. This paper focuses on the comparison of the numerical results obtained by simulations with some high resolution numerical schemes applied on linear and non-linear one-dimensional conservation low. The analytical solutions are provided for all benchmark tests considering smooth periodical conditions. All the schemes converge to the proper weak solution for linear flux and smooth initial conditions. However, when the flux is non-linear, the discontinuities may develop from smooth initial conditions and the shock must be correctly captured. All the schemes accurately identify the shock position, with the price of the numerical oscillation in the vicinity of the sudden variation. We believe that the identification of this pure numerical behavior, without physical relevance, in 1D case is extremely useful to avoid problems related to the stability and convergence of the solution in the general 3D case.

  13. Mixed ultrasoft/norm-conserved pseudopotential scheme

    DEFF Research Database (Denmark)

    Stokbro, Kurt

    1996-01-01

    A variant of the Vanderbilt ultrasoft pseudopotential scheme, where the norm conservation is released for only one or a few angular channels, is presented. Within this scheme some difficulties of the truly ultrasoft pseudopotentials are overcome without sacrificing the pseudopotential softness. (...

  14. Local ensemble assimilation scheme with global constraints and conservation

    Science.gov (United States)

    Barth, Alexander; Yan, Yajing; Alvera-Azcárate, Aida; Beckers, Jean-Marie

    2016-12-01

    Ensemble assimilation schemes applied in their original, global formulation respect linear conservation properties if the ensemble perturbations are set up accordingly. For realistic ocean systems, only a relatively small number of ensemble members can be calculated. A localization of the ensemble increment is therefore necessary to filter out spurious long-range correlations. The conservation of the global properties will be lost if the assimilation is performed locally, since the conservation requires a coupling between all model grid points which is removed by the localization. The distribution of ocean observations is often highly inhomogeneous. Systematic errors of the observed parts of the ocean state can lead to spurious adjustment of the non-observed parts via data assimilation and thus to a spurious increase or decrease in long-term simulations of global properties which should be conserved. In this paper, we propose a local assimilation scheme (with different variants and assumptions) which can satisfy global conservation properties. The proposed scheme can also be used for non-local observation operators. Different variants of the proposed scheme are tested in an idealized model and compared to the traditional covariance localization with an ad-hoc step enforcing conservation. It is shown that the inclusion of the conservation property reduces the total RMS error and that the presented stochastic and deterministic schemes avoiding error space rotation provide better results than the traditional covariance localization.

  15. Difference Schemes and Applications

    Science.gov (United States)

    2015-02-06

    of the shallow water equations that is well suited for complex geometries and moving boundaries. Another (similar) regularization of...the solid wall extrapolation followed by the interpolation in the phase space (by solving the Riemann problem between the internal cell averages and...scheme. This Godunov-type scheme enjoys all major advantages of Riemann -problem-solver-free, non-oscillatory central schemes and, at the same time, have

  16. New Conservative Schemes for Regularized Long Wave Equation

    Institute of Scientific and Technical Information of China (English)

    Tingchun Wang; Luming Zhang

    2006-01-01

    In this paper, two finite difference schemes are presented for initial-boundary value problems of Regularized Long-Wave(RLW) equation. They all have the advantages that there are discrete energies which are conserved. Convergence and stability of difference solutions with order O(h2 +τ2) are proved in the energy norm. Numerical experiment results demonstrate the effectiveness of the proposed schemes.

  17. Composite centered schemes for multidimensional conservation laws

    Energy Technology Data Exchange (ETDEWEB)

    Liska, R. [Czech Technical Univ., Prague (Czech Republic). Faculty of Nuclear Sciences and Physical Engineering; Wendroff, B. [Los Alamos National Lab., NM (United States)

    1998-05-08

    The oscillations of a centered second order finite difference scheme and the excessive diffusion of a first order centered scheme can be overcome by global composition of the two, that is by performing cycles consisting of several time steps of the second order method followed by one step of the diffusive method. The authors show the effectiveness of this approach on some test problems in two and three dimensions.

  18. Efficient Conservative Reformulation Schemes for Lithium Intercalation

    Energy Technology Data Exchange (ETDEWEB)

    Urisanga, PC; Rife, D; De, S; Subramanian, VR

    2015-02-18

    Porous electrode theory coupled with transport and reaction mechanisms is a widely used technique to model Li-ion batteries employing an appropriate discretization or approximation for solid phase diffusion with electrode particles. One of the major difficulties in simulating Li-ion battery models is the need to account for solid phase diffusion in a second radial dimension r, which increases the computation time/cost to a great extent. Various methods that reduce the computational cost have been introduced to treat this phenomenon, but most of them do not guarantee mass conservation. The aim of this paper is to introduce an inherently mass conserving yet computationally efficient method for solid phase diffusion based on Lobatto III A quadrature. This paper also presents coupling of the new solid phase reformulation scheme with a macro-homogeneous porous electrode theory based pseudo 20 model for Li-ion battery. (C) The Author(s) 2015. Published by ECS. All rights reserved.

  19. A new semi-Lagrangian difference scheme

    Institute of Scientific and Technical Information of China (English)

    季仲贞; 陈嘉滨

    2001-01-01

    A new completely energy-conserving semi-Lagrangian scheme is constructed. The numerical solution of shallow water equation shows that this conservative scheme preserves the total energy in twelve significant digits, while the traditional scheme does only in five significant digits.

  20. A conservative numerical scheme for solving an autonomous Hamiltonian system

    Science.gov (United States)

    Petrov, A. G.; Uvarov, A. V.

    2016-09-01

    A new numerical scheme is proposed for solving Hamilton's equations that possesses the properties of symplecticity. Just as in all symplectic schemes known to date, in this scheme the conservation laws of momentum and angular momentum are satisfied exactly. A property that distinguishes this scheme from known schemes is proved: in the new scheme, the energy conservation law is satisfied for a system of linear oscillators. The new numerical scheme is implicit and has the third order of accuracy with respect to the integration step. An algorithm is presented by which the accuracy of the scheme can be increased up to the fifth and higher orders. Exact and numerical solutions to the two-body problem, calculated by known schemes and by the scheme proposed here, are compared.

  1. The relationship between short-range motion of atmosphere and ocean and conservative and nonconservative scheme

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Taking one-dimensional shallow water wave equation as an example, a comparative analysis on the computational stability related to the short-range motion of atmosphere and ocean is carried out for the conservative and nonconservative scheme, and it is pointed out that the computational stability of conservative scheme is absolutely different from that of the nonconservative scheme. The relationship between the short-range motion of atmosphere and ocean and the conservative and nonconservative scheme is further discussed. The constructed conservative scheme is proved to be stable by the numerical experiment for the short-range motion of atmosphere and ocean while the CTCS scheme is unstable. So that the conservative scheme for the solution of this kind of problem has more advantages.

  2. ON THE CENTRAL RELAXING SCHEMES I:SINGLE CONSERVATION LAWS

    Institute of Scientific and Technical Information of China (English)

    Hua-zhong Tang

    2000-01-01

    In this first paper we present a central relaxing scheme for scalar conservation laws, based on using the local relaxation approximation. Our scheme is obtained without using linear or nonlinear Riemann solvers. A cell entropy inequality is studied for the semidiscrete central relaxing scheme, and a second order MUSCL scheme is shown to be TVD in the zero relaxation limit. The next paper will extend the central relaxing scheme to multi-dimensional systems of conservation laws in curvilinear coordinates, including numerical experiments for 1D and 2D problems.

  3. Accurate numerical schemes for approximating initial-boundary value problems for systems of conservation laws

    CERN Document Server

    Mishra, Siddhartha

    2011-01-01

    Solutions of initial-boundary value problems for systems of conservation laws depend on the underlying viscous mechanism, namely different viscosity operators lead to different limit solutions. Standard numerical schemes for approximating conservation laws do not take into account this fact and converge to solutions that are not necessarily physically relevant. We design numerical schemes that incorporate explicit information about the underlying viscosity mechanism and approximate the physically relevant solution. Numerical experiments illustrating the robust performance of these schemes are presented.

  4. CRKSPH - A Conservative Reproducing Kernel Smoothed Particle Hydrodynamics Scheme

    Science.gov (United States)

    Frontiere, Nicholas; Raskin, Cody D.; Owen, J. Michael

    2017-03-01

    We present a formulation of smoothed particle hydrodynamics (SPH) that utilizes a first-order consistent reproducing kernel, a smoothing function that exactly interpolates linear fields with particle tracers. Previous formulations using reproducing kernel (RK) interpolation have had difficulties maintaining conservation of momentum due to the fact the RK kernels are not, in general, spatially symmetric. Here, we utilize a reformulation of the fluid equations such that mass, linear momentum, and energy are all rigorously conserved without any assumption about kernel symmetries, while additionally maintaining approximate angular momentum conservation. Our approach starts from a rigorously consistent interpolation theory, where we derive the evolution equations to enforce the appropriate conservation properties, at the sacrifice of full consistency in the momentum equation. Additionally, by exploiting the increased accuracy of the RK method's gradient, we formulate a simple limiter for the artificial viscosity that reduces the excess diffusion normally incurred by the ordinary SPH artificial viscosity. Collectively, we call our suite of modifications to the traditional SPH scheme Conservative Reproducing Kernel SPH, or CRKSPH. CRKSPH retains many benefits of traditional SPH methods (such as preserving Galilean invariance and manifest conservation of mass, momentum, and energy) while improving on many of the shortcomings of SPH, particularly the overly aggressive artificial viscosity and zeroth-order inaccuracy. We compare CRKSPH to two different modern SPH formulations (pressure based SPH and compatibly differenced SPH), demonstrating the advantages of our new formulation when modeling fluid mixing, strong shock, and adiabatic phenomena.

  5. An energy and potential enstrophy conserving scheme for the shallow water equations. [orography effects on atmospheric circulation

    Science.gov (United States)

    Arakawa, A.; Lamb, V. R.

    1979-01-01

    A three-dimensional finite difference scheme for the solution of the shallow water momentum equations which accounts for the conservation of potential enstrophy in the flow of a homogeneous incompressible shallow atmosphere over steep topography as well as for total energy conservation is presented. The scheme is derived to be consistent with a reasonable scheme for potential vorticity advection in a long-term integration for a general flow with divergent mass flux. Numerical comparisons of the characteristics of the present potential enstrophy-conserving scheme with those of a scheme that conserves potential enstrophy only for purely horizontal nondivergent flow are presented which demonstrate the reduction of computational noise in the wind field with the enstrophy-conserving scheme and its convergence even in relatively coarse grids.

  6. CRKSPH - A Conservative Reproducing Kernel Smoothed Particle Hydrodynamics Scheme

    CERN Document Server

    Frontiere, Nicholas; Owen, J Michael

    2016-01-01

    We present a formulation of smoothed particle hydrodynamics (SPH) that employs a first-order consistent reproducing kernel function, exactly interpolating linear fields with particle tracers. Previous formulations using reproducing kernel (RK) interpolation have had difficulties maintaining conservation of momentum due to the fact the RK kernels are not, in general, spatially symmetric. Here, we utilize a reformulation of the fluid equations such that mass, momentum, and energy are all manifestly conserved without any assumption about kernel symmetries. Additionally, by exploiting the increased accuracy of the RK method's gradient, we formulate a simple limiter for the artificial viscosity that reduces the excess diffusion normally incurred by the ordinary SPH artificial viscosity. Collectively, we call our suite of modifications to the traditional SPH scheme Conservative Reproducing Kernel SPH, or CRKSPH. CRKSPH retains the benefits of traditional SPH methods (such as preserving Galilean invariance and manif...

  7. A systematic method to enforce conservativity on semi-Lagrangian schemes

    CERN Document Server

    Cameron, Alexandre

    2016-01-01

    Semi-Lagrangian schemes have proven to be very efficient to model advection problems. However most semi-Lagrangian schemes are not conservative. Here, a systematic method is introduced in order to enforce the conservative property on a semi-Lagrangian advection scheme. This method is shown to generate conservative schemes with the same linear stability range and the same order of accuracy as the initial advection scheme from which they are derived. We used a criterion based on the column-balance property of the schemes to assess their conservativity property. We show that this approach can be used with large CFL numbers and third order schemes.

  8. Nonstandard finite difference schemes for differential equations

    Directory of Open Access Journals (Sweden)

    Mohammad Mehdizadeh Khalsaraei

    2014-12-01

    Full Text Available In this paper, the reorganization of the denominator of the discrete derivative and nonlocal approximation of nonlinear terms are used in the design of nonstandard finite difference schemes (NSFDs. Numerical examples confirming then efficiency of schemes, for some differential equations are provided. In order to illustrate the accuracy of the new NSFDs, the numerical results are compared with standard methods.

  9. Error Analysis of Explicit Partitioned Runge–Kutta Schemes for Conservation Laws

    KAUST Repository

    Hundsdorfer, Willem

    2014-08-27

    An error analysis is presented for explicit partitioned Runge–Kutta methods and multirate methods applied to conservation laws. The interfaces, across which different methods or time steps are used, lead to order reduction of the schemes. Along with cell-based decompositions, also flux-based decompositions are studied. In the latter case mass conservation is guaranteed, but it will be seen that the accuracy may deteriorate.

  10. Accuracy property of certain hyperbolic difference schemes

    Energy Technology Data Exchange (ETDEWEB)

    Hicks, D.L.; Madsen, M.M.

    1976-12-01

    An accuracy property called the CFL1 property is shared by several successful difference schemes. It appears to be a property at least as important as the property of higher-order accuracy for hyperbolic difference schemes when weak solutions (e.g., shocks) are sought. Investigation of this property leads to suggestions of ways to improve the accuracy in such wavecodes as WONDY, CHARTD, and THREEDY. 10 figures.

  11. Stable schemes for dissipative particle dynamics with conserved energy

    Energy Technology Data Exchange (ETDEWEB)

    Stoltz, Gabriel, E-mail: stoltz@cermics.enpc.fr

    2017-07-01

    This article presents a new numerical scheme for the discretization of dissipative particle dynamics with conserved energy. The key idea is to reduce elementary pairwise stochastic dynamics (either fluctuation/dissipation or thermal conduction) to effective single-variable dynamics, and to approximate the solution of these dynamics with one step of a Metropolis–Hastings algorithm. This ensures by construction that no negative internal energies are encountered during the simulation, and hence allows to increase the admissible timesteps to integrate the dynamics, even for systems with small heat capacities. Stability is only limited by the Hamiltonian part of the dynamics, which suggests resorting to multiple timestep strategies where the stochastic part is integrated less frequently than the Hamiltonian one.

  12. grim: A Flexible, Conservative Scheme for Relativistic Fluid Theories

    Science.gov (United States)

    Chandra, Mani; Foucart, Francois; Gammie, Charles F.

    2017-03-01

    Hot, diffuse, relativistic plasmas such as sub-Eddington black-hole accretion flows are expected to be collisionless, yet are commonly modeled as a fluid using ideal general relativistic magnetohydrodynamics (GRMHD). Dissipative effects such as heat conduction and viscosity can be important in a collisionless plasma and will potentially alter the dynamics and radiative properties of the flow from that in ideal fluid models; we refer to models that include these processes as Extended GRMHD. Here we describe a new conservative code, grim, that enables all of the above and additional physics to be efficiently incorporated. grim combines time evolution and primitive variable inversion needed for conservative schemes into a single step using an algorithm that only requires the residuals of the governing equations as inputs. This algorithm enables the code to be physics agnostic as well as flexibility regarding time-stepping schemes. grim runs on CPUs, as well as on GPUs, using the same code. We formulate a performance model and use it to show that our implementation runs optimally on both architectures. grim correctly captures classical GRMHD test problems as well as a new suite of linear and nonlinear test problems with anisotropic conduction and viscosity in special and general relativity. As tests and example applications, we resolve the shock substructure due to the presence of dissipation, and report on relativistic versions of the magneto-thermal instability and heat flux driven buoyancy instability, which arise due to anisotropic heat conduction, and of the firehose instability, which occurs due to anisotropic pressure (i.e., viscosity). Finally, we show an example integration of an accretion flow around a Kerr black hole, using Extended GRMHD.

  13. Speeding up Monte Carlo molecular simulation by a non-conservative early rejection scheme

    KAUST Repository

    Kadoura, Ahmad Salim

    2015-04-23

    Monte Carlo (MC) molecular simulation describes fluid systems with rich information, and it is capable of predicting many fluid properties of engineering interest. In general, it is more accurate and representative than equations of state. On the other hand, it requires much more computational effort and simulation time. For that purpose, several techniques have been developed in order to speed up MC molecular simulations while preserving their precision. In particular, early rejection schemes are capable of reducing computational cost by reaching the rejection decision for the undesired MC trials at an earlier stage in comparison to the conventional scheme. In a recent work, we have introduced a ‘conservative’ early rejection scheme as a method to accelerate MC simulations while producing exactly the same results as the conventional algorithm. In this paper, we introduce a ‘non-conservative’ early rejection scheme, which is much faster than the conservative scheme, yet it preserves the precision of the method. The proposed scheme is tested for systems of structureless Lennard-Jones particles in both canonical and NVT-Gibbs ensembles. Numerical experiments were conducted at several thermodynamic conditions for different number of particles. Results show that at certain thermodynamic conditions, the non-conservative method is capable of doubling the speed of the MC molecular simulations in both canonical and NVT-Gibbs ensembles. © 2015 Taylor & Francis

  14. A Hybrid Advection Scheme for Conserving Angular Momentum on a Refined Cartesian Mesh

    CERN Document Server

    Byerly, Zachary D; Tohline, Joel E; Marcello, Dominic C

    2014-01-01

    We test a new "hybrid" scheme for simulating dynamical fluid flows in which cylindrical components of the momentum are advected across a rotating Cartesian coordinate mesh. This hybrid scheme allows us to conserve angular momentum to machine precision while capitalizing on the advantages offered by a Cartesian mesh, such as a straightforward implementation of mesh refinement. Our test focuses on measuring the real and imaginary parts of the eigenfrequency of unstable axisymmetric modes that naturally arise in massless polytropic tori having a range of different aspect ratios, and quantifying the uncertainty in these measurements. Our measured eigenfrequencies show good agreement with the results obtained from the linear stability analysis of Kojima (1986) and from nonlinear hydrodynamic simulations performed on a cylindrical coordinate mesh by Woodward et al. (1994). When compared against results conducted with a traditional Cartesian advection scheme, the hybrid scheme achieves qualitative convergence at the...

  15. CONSERVATION OF THREE-POINT COMPACT SCHEMES ON SINGLE AND MULTIBLOCK PATCHED GRIDS FOR HYPERBOLIC PROBLEMS

    Institute of Scientific and Technical Information of China (English)

    Zi-niu Wu

    2003-01-01

    For nonlinear hyperbolic problems, conservation of the numerical scheme is importantfor convergence to the correct weak solutions. In this paper the conservation of the well-known compact scheme up to fourth order of accuracy on a single and uniform grid isstudied, and a conservative interface treatment is derived for compact schemes on patchedgrids. For a pure initial value problem, the compact scheme is shown to be equivalent toa scheme in the usual conservative form. For the case of a mixed initial boundary valueproblem, the compact scheme is conservative only if the rounding errors are small enough.For a patched grid interface, a conservative interface condition useful for mesh refinementand for parallel computation is derived and its order of local accuracy is analyzed.

  16. Energy conserving schemes for the simulation of musical instrument contact dynamics

    CERN Document Server

    Chatziioannou, Vasileios

    2015-01-01

    Collisions are an innate part of the function of many musical instruments. Due to the nonlinear nature of contact forces, special care has to be taken in the construction of numerical schemes for simulation and sound synthesis. Finite difference schemes and other time-stepping algorithms used for musical instrument modelling purposes are normally arrived at by discretising a Newtonian description of the system. However because impact forces are non-analytic functions of the phase space variables, algorithm stability can rarely be established this way. This paper presents a systematic approach to deriving energy conserving schemes for frictionless impact modelling. The proposed numerical formulations follow from discretising Hamilton's equations of motion, generally leading to an implicit system of nonlinear equations that can be solved with Newton's method. The approach is first outlined for point mass collisions and then extended to distributed settings, such as vibrating strings and beams colliding with rig...

  17. Traditional and Truncation schemes for Different Multiplier

    Directory of Open Access Journals (Sweden)

    Yogesh M. Motey

    2013-03-01

    Full Text Available A rapid and proficient in power requirement multiplier is always vital in electronics industry like DSP, image processing and ALU in microprocessors. Multiplier is such an imperative block w ith respect to power consumption and area occupied in the system. In order to meet the demand for high speed, various parallel array multiplication algorithms have been proposed by a number of authors. The array multipliers use a large amount of hardware, consequently consuming a large amount of power. One of the methods for multiplication is based on Indian Vedic mathematics. The total Vedic mathematics is based on sixteen sutras (word formulae and manifests a merged structure of mathematics. The parallel multipliers for example radix 2 and radix 4 booth multiplier does the computations using less number of adders and less number of iterative steps that results in, they occupy less space to that of serial multiplier. Truncated multipliers offer noteworthy enhancements in area, delay, and power. Truncated multiplication provides different method for reducing the power dissipation and area of rounded parallel multipliers in DSP systems. Since in a truncated multiplier the x less significant bits of the full-width product are discarded thus partial products are removed and replaced by a suit- able compensation equations, match the accuracy with hardware cost. A pseudo-carry compensation truncation (PCT scheme, it is for the multiplexer based array multiplier, which yields less average error among existing truncation methods.After studying many research papers it’s found that some of the schemes for multiplier are suitable because their own uniqueness of multiplication. Such schemes are listed in this paper for example the different truncation schemes like constant-correction truncation (CCT, variable -correction truncation (VCT, pseudo-carry compensation truncation (PCT are most suitable for truncated multiplier.

  18. DIFFERENCE SCHEMES BASING ON COEFFICIENT APPROXIMATION

    Institute of Scientific and Technical Information of China (English)

    MOU Zong-ze; LONG Yong-xing; QU Wen-xiao

    2005-01-01

    In respect of variable coefficient differential equations, the equations of coefficient function approximation were more accurate than the coefficient to be frozen as a constant in every discrete subinterval. Usually, the difference schemes constructed based on Taylor expansion approximation of the solution do not suit the solution with sharp function.Introducing into local bases to be combined with coefficient function approximation, the difference can well depict more complex physical phenomena, for example, boundary layer as well as high oscillatory, with sharp behavior. The numerical test shows the method is more effective than the traditional one.

  19. A Difference Scheme for the Coupled KdV Equation 14

    Institute of Scientific and Technical Information of China (English)

    ShaohongZHU

    1999-01-01

    In this paper,a difference scheme for the periodic initial-boundary problem of the coupled KdV equation is given.The scheme keeps the first two conserved quantities which the differential equation possesses.The catch-ran iterative method is used to solve the difference equations.The numerical simulation exhibits the existence of two-soliton solutions.

  20. A note on semi-discrete conservation laws and conservation of wave action by multisymplectic Runge-Kutta box schemes

    NARCIS (Netherlands)

    Frank, J.E.

    2006-01-01

    In this note we show that multisymplectic Runge-Kutta box schemes, of which the Gauss-Legendre methods are the most important, preserve a discrete conservation law of wave action. The result follows by loop integration over an ensemble of flow realizations, and the local energy-momentum conservation

  1. A database of schemes that prioritize sites and species based on their conservation value: focusing business on biodiversity.

    Science.gov (United States)

    Blundell, Arthur G; Burkey, Tormod V

    2007-09-27

    Biodiversity offsets are conservation projects used mainly by business to counterbalance the environmental impacts of their operations, with the aim of achieving a net neutral or even beneficial outcome for biodiversity. Companies considering offsets need to know: (1) if there are areas of such biological importance that no impact is acceptable, and outside of these no-go areas, (2) the relative importance of biodiversity in the impacted site versus the site(s) proposed for protection, to ensure that the offset is of equal or greater status than that lost through the company's operations. We compiled a database of 40 schemes that use various methods to assess conservation priorities, and we examined if the schemes would allow companies to answer the above questions. Overall, schemes tend to be designed to guide conservation organizations in their own priority setting or they categorize species based on conservation status. Generally, the schemes do not provide all the necessary information for offsets because they operate at a broad spatial scale or with low spatial resolution, which make it difficult to assess sites at the project level. Furthermore, most schemes do not explicitly incorporate threat, which we consider key to assessing whether offsets protect habitats or species that would otherwise be lost (i.e., provide additionality). The schemes are useful, however, for identifying the major conservation issues in different ecosystems around the globe. Companies can proceed by first avoiding, reducing, and mitigating impacts, and then using existing schemes to identify i) no-go areas and ii) appropriate offsets to compensate for any unavoidable loss in biodiversity. If existing schemes are inadequate, then companies should use integrated conservation planning techniques to define offset options within the region of their operations.

  2. Conserving GW scheme for nonequilibrium quantum transport in molecular contacts

    DEFF Research Database (Denmark)

    Thygesen, Kristian Sommer; Rubio, Angel

    2008-01-01

    We give a detailed presentation of our recent scheme to include correlation effects in molecular transport calculations using the nonequilibrium Keldysh formalism. The scheme is general and can be used with any quasiparticle self-energy, but for practical reasons, we mainly specialize to the so-c...

  3. Modeling and Analysis of Energy Conservation Scheme Based on Duty Cycling in Wireless Ad Hoc Sensor Network

    Directory of Open Access Journals (Sweden)

    Yun Won Chung

    2010-06-01

    Full Text Available In sensor network, energy conservation is one of the most critical issues since sensor nodes should perform a sensing task for a long time (e.g., lasting a few years but the battery of them cannot be replaced in most practical situations. For this purpose, numerous energy conservation schemes have been proposed and duty cycling scheme is considered the most suitable power conservation technique, where sensor nodes alternate between states having different levels of power consumption. In order to analyze the energy consumption of energy conservation scheme based on duty cycling, it is essential to obtain the probability of each state. In this paper, we analytically derive steady state probability of sensor node states, i.e., sleep, listen, and active states, based on traffic characteristics and timer values, i.e., sleep timer, listen timer, and active timer. The effect of traffic characteristics and timer values on the steady state probability and energy consumption is analyzed in detail. Our work can provide sensor network operators guideline for selecting appropriate timer values for efficient energy conservation. The analytical methodology developed in this paper can be extended to other energy conservation schemes based on duty cycling with different sensor node states, without much difficulty.

  4. Modeling and analysis of energy conservation scheme based on duty cycling in wireless ad hoc sensor network.

    Science.gov (United States)

    Chung, Yun Won; Hwang, Ho Young

    2010-01-01

    In sensor network, energy conservation is one of the most critical issues since sensor nodes should perform a sensing task for a long time (e.g., lasting a few years) but the battery of them cannot be replaced in most practical situations. For this purpose, numerous energy conservation schemes have been proposed and duty cycling scheme is considered the most suitable power conservation technique, where sensor nodes alternate between states having different levels of power consumption. In order to analyze the energy consumption of energy conservation scheme based on duty cycling, it is essential to obtain the probability of each state. In this paper, we analytically derive steady state probability of sensor node states, i.e., sleep, listen, and active states, based on traffic characteristics and timer values, i.e., sleep timer, listen timer, and active timer. The effect of traffic characteristics and timer values on the steady state probability and energy consumption is analyzed in detail. Our work can provide sensor network operators guideline for selecting appropriate timer values for efficient energy conservation. The analytical methodology developed in this paper can be extended to other energy conservation schemes based on duty cycling with different sensor node states, without much difficulty.

  5. Accuracy of spectral and finite difference schemes in 2D advection problems

    DEFF Research Database (Denmark)

    Naulin, V.; Nielsen, A.H.

    2003-01-01

    In this paper we investigate the accuracy of two numerical procedures commonly used to solve 2D advection problems: spectral and finite difference (FD) schemes. These schemes are widely used, simulating, e.g., neutral and plasma flows. FD schemes have long been considered fast, relatively easy...... that the accuracy of FD schemes can be significantly improved if one is careful in choosing an appropriate FD scheme that reflects conservation properties of the nonlinear terms and in setting up the grid in accordance with the problem....

  6. Finite-difference schemes for anisotropic diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Es, Bram van, E-mail: es@cwi.nl [Centrum Wiskunde and Informatica, P.O. Box 94079, 1090GB Amsterdam (Netherlands); FOM Institute DIFFER, Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM (Netherlands); Koren, Barry [Eindhoven University of Technology (Netherlands); Blank, Hugo J. de [FOM Institute DIFFER, Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM (Netherlands)

    2014-09-01

    In fusion plasmas diffusion tensors are extremely anisotropic due to the high temperature and large magnetic field strength. This causes diffusion, heat conduction, and viscous momentum loss, to effectively be aligned with the magnetic field lines. This alignment leads to different values for the respective diffusive coefficients in the magnetic field direction and in the perpendicular direction, to the extent that heat diffusion coefficients can be up to 10{sup 12} times larger in the parallel direction than in the perpendicular direction. This anisotropy puts stringent requirements on the numerical methods used to approximate the MHD-equations since any misalignment of the grid may cause the perpendicular diffusion to be polluted by the numerical error in approximating the parallel diffusion. Currently the common approach is to apply magnetic field-aligned coordinates, an approach that automatically takes care of the directionality of the diffusive coefficients. This approach runs into problems at x-points and at points where there is magnetic re-connection, since this causes local non-alignment. It is therefore useful to consider numerical schemes that are tolerant to the misalignment of the grid with the magnetic field lines, both to improve existing methods and to help open the possibility of applying regular non-aligned grids. To investigate this, in this paper several discretization schemes are developed and applied to the anisotropic heat diffusion equation on a non-aligned grid.

  7. Interference Phenomenon for Different Chiral Bosonization Schemes

    CERN Document Server

    Abreu, Everton M C; Abreu, Everton M C; Wotzasek, Clovis

    1998-01-01

    We study the relationship between different chiral bosonization schemes (CBS) in the context of the soldering formalism\\cite{MS}, that considers the phenomenon of interference in the quantum field theory\\cite{ABW}. This analysis is done in the framework put forward by Siegel\\cite{WS} and by Floreanini and Jackiw\\cite{FJ} (FJ). We propose a field redefinition that discloses the presence of a noton, a non dynamical field, in Siegel's formulation for chiral bosons. The presence of a noton in the Siegel CBS is a new and surprising result, that separates dynamics from symmetry by diagonalising the Siegel action into the FJ and the noton action. While the first describes the chiral dynamics, the noton carries the symmetry contents, acquiring dynamics upon quantization and is fully responsible for the Siegel anomaly. The diagonal representation proposed here is used to study the effect of quantum interference between gauged rightons and leftons.

  8. Scale-selective dissipation in energy-conserving finite element schemes for two-dimensional turbulence

    CERN Document Server

    Natale, Andrea

    2016-01-01

    We analyse the multiscale properties of energy-conserving upwind-stabilised finite element discretisations of the two-dimensional incompressible Euler equations. We focus our attention on two particular methods: the Lie derivative discretisation introduced in Natale and Cotter (2016a) and the SUPG discretisation of the vorticity advection equation. Such discretisations provide control on enstrophy by modelling different types of scale interactions. We quantify the performance of the schemes in reproducing the non-local energy backscatter that characterises two-dimensional turbulent flows.

  9. Explicit and implicit finite difference schemes for fractional Cattaneo equation

    Science.gov (United States)

    Ghazizadeh, H. R.; Maerefat, M.; Azimi, A.

    2010-09-01

    In this paper, the numerical solution of fractional (non-integer)-order Cattaneo equation for describing anomalous diffusion has been investigated. Two finite difference schemes namely an explicit predictor-corrector and totally implicit schemes have been developed. In developing each scheme, a separate formulation approach for the governing equations has been considered. The explicit predictor-corrector scheme is the fractional generalization of well-known MacCormack scheme and has been called Generalized MacCormack scheme. This scheme solves two coupled low-order equations and simultaneously computes the flux term with the main variable. Fully implicit scheme however solves a single high-order undecomposed equation. For Generalized MacCormack scheme, stability analysis has been studied through Fourier method. Through a numerical test, the experimental order of convergency of both schemes has been found. Then, the domain of applicability and some numerical properties of each scheme have been discussed.

  10. SIGNCRYPTION BASED ON DIFFERENT DIGITAL SIGNATURE SCHEMES

    OpenAIRE

    Adrian Atanasiu; Laura Savu

    2012-01-01

    This article presents two new signcryption schemes. The first one is based on Schnorr digital signature algorithm and the second one is using Proxy Signature scheme introduced by Mambo. Schnorr Signcryption has been implemented in a program and here are provided the steps of the algorithm, the results and some examples. The Mambo’s Proxy Signature is adapted for Shortened Digital Signature Standard, being part of a new Proxy Signcryption scheme.

  11. Different options for noble gas categorization schemes

    Science.gov (United States)

    Kalinowski, Martin

    2010-05-01

    For noble gas monitoring it is crucial to support the decision makers who need to decide whether a decection may indicate a potential nuclear test. Several parameters are available that may help to distinguish a legitimate civilian source from a nuclear explosion. The most promising parameters are: (a) Anomaly observations with respect to the history of concentrations found at that site. (b) Isotopic activity ratios can be used to separate a nuclear reactor domain from the parameter space that is specific for nuclear explosions. (c) Correlation with source-receptor-sensitivities related to known civilian sources as determined by atmospheric transport simulations. A combination of these can be used to categorize an observation. So far, several initial ideas have been presented but the issue of noble gas categorisation has been postponed with the argument that further scientific studies and additional experience have to be awaited. This paper presents the principles of different options for noble gas categorisation and considers how they would meet the interests of different classes of member states. It discusses under different points of view what might be the best approach for the noble gas categorisation scheme.

  12. Single-cone real-space finite difference schemes for the Dirac von Neumann equation

    CERN Document Server

    Schreilechner, Magdalena

    2015-01-01

    Two finite difference schemes for the numerical treatment of the von Neumann equation for the (2+1)D Dirac Hamiltonian are presented. Both utilize a single-cone staggered space-time grid which ensures a single-cone energy dispersion to formulate a numerical treatment of the mixed-state dynamics within the von Neumann equation. The first scheme executes the time-derivative according to the product rule for "bra" and "ket" indices of the density operator. It therefore directly inherits all the favorable properties of the difference scheme for the pure-state Dirac equation and conserves positivity. The second scheme proposed here performs the time-derivative in one sweep. This direct scheme is investigated regarding stability and convergence. Both schemes are tested numerically for elementary simulations using parameters which pertain to topological insulator surface states. Application of the schemes to a Dirac Lindblad equation and real-space-time Green's function formulations are discussed.

  13. PERTURBATIONAL FINITE DIFFERENCE SCHEME OF CONVECTION-DIFFUSION EQUATION

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The Perturbational Finite Difference (PFD) method is a kind of high-order-accurate compact difference method, But its idea is different from the normal compact method and the multi-nodes method. This method can get a Perturbational Exact Numerical Solution (PENS) scheme for locally linearlized Convection-Diffusion (CD) equation. The PENS scheme is similar to the Finite Analytical (FA) scheme and Exact Difference Solution (EDS) scheme, which are all exponential schemes, but PENS scheme is simpler and uses only 3, 5 and 7 nodes for 1-, 2- and 3-dimensional problems, respectively. The various approximate schemes of PENS scheme are also called Perturbational-High-order-accurate Difference (PHD) scheme. The PHD schemes can be got by expanding the exponential terms in the PENS scheme into power series of grid Renold number, and they are all upwind schemes and remain the concise structure form of first-order upwind scheme. For 1-dimensional (1-D) CD equation and 2-D incompressible Navier-Stokes equation, their PENS and PHD schemes were constituted in this paper, they all gave highly accurate results for the numerical examples of three 1-D CD equations and an incompressible 2-D flow in a square cavity.

  14. A mass-conserving advection scheme for offline simulation of scalar transport in coastal ocean models

    Science.gov (United States)

    Gillibrand, P. A.; Herzfeld, M.

    2016-05-01

    We present a flux-form semi-Lagrangian (FFSL) advection scheme designed for offline scalar transport simulation with coastal ocean models using curvilinear horizontal coordinates. The scheme conserves mass, overcoming problems of mass conservation typically experienced with offline transport models, and permits long time steps (relative to the Courant number) to be used by the offline model. These attributes make the method attractive for offline simulation of tracers in biogeochemical or sediment transport models using archived flow fields from hydrodynamic models. We describe the FFSL scheme, and test it on two idealised domains and one real domain, the Great Barrier Reef in Australia. For comparison, we also include simulations using a traditional semi-Lagrangian advection scheme for the offline simulations. We compare tracer distributions predicted by the offline FFSL transport scheme with those predicted by the original hydrodynamic model, assess the conservation of mass in all cases and contrast the computational efficiency of the schemes. We find that the FFSL scheme produced very good agreement with the distributions of tracer predicted by the hydrodynamic model, and conserved mass with an error of a fraction of one percent. In terms of computational speed, the FFSL scheme was comparable with the semi-Lagrangian method and an order of magnitude faster than the full hydrodynamic model, even when the latter ran in parallel on multiple cores. The FFSL scheme presented here therefore offers a viable mass-conserving and computationally-efficient alternative to traditional semi-Lagrangian schemes for offline scalar transport simulation in coastal models.

  15. Managing inbreeding in selection and genetic conservation schemes of livestock

    NARCIS (Netherlands)

    Sonesson, A.K.

    2002-01-01

    This thesis deals with the definition of selection and mating criteria for animal breeding populations under selection and for genetic conservation populations, especially emphasizing on populations with small effective sizes that have known pedigrees.Managing inbreeding in selection and genetic conservation schemes of livestock

    NARCIS (Netherlands)

    Sonesson, A.K.

    2002-01-01

    This thesis deals with the definition of selection and mating criteria for animal breeding populations under selection and for genetic conservation populations, especially emphasizing on populations with small effective sizes that have known pedigrees.

    &

  16. Raptor Sanctuary: a Collaboration Scheme for Raptor Conservation in Indonesia

    Directory of Open Access Journals (Sweden)

    Gunawan Gunawan

    2015-12-01

    Full Text Available To support efforts on raptors conservation, it is necessary to activate multi-approach programs. Some approaches can be developed to raise public awareness. Raptor rehabilitation and release programs, environmental education and ecotourism are also important in this way. The establishment of Raptor Sanctuary (Suaka Elang was the result of the collaboration between governmental organizations, NGOs, and companies. The Raptor Sanctuary is expected to contribute actively in the raptor conservation strategies and efforts inIndonesia, particularly onJavaIsland. Since its establishment in November 2008, the Raptor Sanctuary focused on activities and programs such as rescue and rehabilitation for the release of confiscated raptors, developing conservation-based environmental education, and enhancing public and stakeholders’ capacities through participation in training courses and seminars. The Raptor Sanctuary had unique effective approaches to implement its activities to be handled directly by the Raptor Sanctuary or each partner. It is suggested that the Raptor Sanctuary can be introduced as an example of how to implement the effective strategy for raptor conservation.

  17. An Average Linear Difference Scheme for the Generalized Rosenau-KdV Equation

    Directory of Open Access Journals (Sweden)

    Maobo Zheng

    2014-01-01

    Full Text Available An average linear finite difference scheme for the numerical solution of the initial-boundary value problem of Generalized Rosenau-KdV equation is proposed. The existence, uniqueness, and conservation for energy of the difference solution are proved by the discrete energy norm method. It is shown that the finite difference scheme is 2nd-order convergent and unconditionally stable. Numerical experiments verify that the theoretical results are right and the numerical method is efficient and reliable.

  18. Sensitivity of modified Patankar-type schemes for systems of conservative production-destruction equations

    Science.gov (United States)

    Meister, Andreas; Butcher, John C.

    2017-07-01

    The modelling of a wide variety of real life scenarios leads to systems of production-destruction equations. These systems of ordinary differential equations are usually conservative and due to physical, biological or chemical constraints the constituents within these systems are often required to remain positive for all times. Hence, numerical methods applied to such kind of equations have to maintain positivity as well as conservativity in a discrete sense. Modified Patankar-type schemes originally introduced in [1] are known to be unconditionally positive and conservative. In the present paper, we investigate the sensitivity of this class of methods by combining the explicit Euler scheme with the associated modified Patankar method.

  19. A Conserved Minimal Adjustment Scheme for Stabilization of Hydrographic Profiles

    Science.gov (United States)

    2010-01-01

    change heat transport and in turn affect the overturning thermohaline circulation . 3. Stabilization The stabilization process is divided into three...adjustment made without taking heat conservation into account may lead to errors in estimat- ing the ocean’s impact on global climate change . In this...1989: The Southern Ocean thermohaline circulation : A numerical study. J. Phys. Oceanogr., 19, 713–726. Sun, L. C., 1999: Data inter-operability driven

  1. Raptor Sanctuary: a Collaboration Scheme for Raptor Conservation in Indonesia

    OpenAIRE

    Gunawan Gunawan; Bambang Supriyanto; Willy Ekariyono; Sri Mulyati

    2015-01-01

    To support efforts on raptors conservation, it is necessary to activate multi-approach programs. Some approaches can be developed to raise public awareness. Raptor rehabilitation and release programs, environmental education and ecotourism are also important in this way. The establishment of Raptor Sanctuary (Suaka Elang) was the result of the collaboration between governmental organizations, NGOs, and companies. The Raptor Sanctuary is expected to contribute actively in the raptor conservati...

  2. Raptor Sanctuary: a Collaboration Scheme for Raptor Conservation in Indonesia

    OpenAIRE

    Gunawan Gunawan; Bambang Supriyanto; Willy Ekariyono; Sri Mulyati

    2015-01-01

    To support efforts on raptors conservation, it is necessary to activate multi-approach programs. Some approaches can be developed to raise public awareness. Raptor rehabilitation and release programs, environmental education and ecotourism are also important in this way. The establishment of Raptor Sanctuary (Suaka Elang) was the result of the collaboration between governmental organizations, NGOs, and companies. The Raptor Sanctuary is expected to contribute actively in the raptor conservati...

  3. On the monotonicity of multidimensional finite difference schemes

    Science.gov (United States)

    Kovyrkina, O.; Ostapenko, V.

    2016-10-01

    The classical concept of monotonicity, introduced by Godunov for linear one-dimensional difference schemes, is extended to multidimensional case. Necessary and sufficient conditions of monotonicity are obtained for linear multidimensional difference schemes of first order. The constraints on the numerical viscosity are given that ensure the monotonicity of a difference scheme in the multidimensional case. It is proposed a modification of the second order multidimensional CABARET scheme that preserves the monotonicity of one-dimensional discrete solutions and, as a result, ensures higher smoothness in the computation of multidimensional discontinuous solutions. The results of two-dimensional test computations illustrating the advantages of the modified CABARET scheme are presented.

  4. Efficient conservative ADER schemes based on WENO reconstruction and space-time predictor in primitive variables

    CERN Document Server

    Zanotti, Olindo

    2015-01-01

    We present a new version of conservative ADER-WENO finite volume schemes, in which both the high order spatial reconstruction as well as the time evolution of the reconstruction polynomials in the local space-time predictor stage are performed in primitive variables, rather than in conserved ones. Since the underlying finite volume scheme is still written in terms of cell averages of the conserved quantities, our new approach performs the spatial WENO reconstruction twice: the first WENO reconstruction is carried out on the known cell averages of the conservative variables. The WENO polynomials are then used at the cell centers to compute point values of the conserved variables, which are converted into point values of the primitive variables. A second WENO reconstruction is performed on the point values of the primitive variables to obtain piecewise high order reconstruction polynomials of the primitive variables. The reconstruction polynomials are subsequently evolved in time with a novel space-time finite ...

  5. Efficient positive, conservative, Maxwellian preserving and implicit difference schemes for the 1-D isotropic Fokker-Planck-Landau equation; Schemas positifs, implicites, conservant l'energie et les etats d'equilibre pour l'equation de Fokker-Planck-Landau isotrope

    Energy Technology Data Exchange (ETDEWEB)

    Buet, Ch. [CEA Bruyeres-le-Chatel, Dept. Sciences de la Simulation et de l' Information, Service Numerique Environnement et Constantes, 91 (France); Le Thanh, K.C. [CEA Bruyeres-le-Chatel, Service Physique des Plasmas et Electromagnetisme, 91 (France). Dept. de Physique Theorique et Appliquee

    2008-07-01

    The aim of this paper is to describe the discretization of the Fokker-Planck-Landau (FPL) collision term in the isotropic case, which models the self-collision for the electrons when they are totally isotropized by heavy particles background such as ions. The discussion focuses on schemes, which could preserve positivity, mass, energy and Maxwellian equilibrium. The Chang and Cooper method is widely used by plasma's physicists for the FPL equation (and for Fokker-Planck type equations). We present a new variant that is both positive and conservative contrary to the existing one's. We propose also a non Chang and Cooper 'type scheme on non-uniform grid, which is also both positive, conservative and equilibrium state preserving contrary to existing one's. The case of Coulombian potential is emphasized. We address also the problem of the time discretization. In particular we show how to recast some implicit methods to get band diagonal system and to solve it by direct method with a linear cost. (authors)

  6. On the Convergence of Space-Time Discontinuous Galerkin Schemes for Scalar Conservation Laws

    CERN Document Server

    May, Georg

    2016-01-01

    We prove convergence of a class of space-time discontinuous Galerkin schemes for scalar hyperbolic conservation laws. Convergence to the unique entropy solution is shown for all orders of polynomial approximation, provided strictly monotone flux functions and a suitable shock-capturing operator are used. The main improvement, compared to previously published results of similar scope, is that no streamline-diffusion stabilization is used. This is the way discontinuous Galerkin schemes were originally proposed, and are most often used in practice.

  7. Nonoscillatory Central Schemes for Hyperbolic Systems of Conservation Laws in Three-Space Dimensions

    Directory of Open Access Journals (Sweden)

    Andrew N. Guarendi

    2013-01-01

    Full Text Available We extend a family of high-resolution, semidiscrete central schemes for hyperbolic systems of conservation laws to three-space dimensions. Details of the schemes, their implementation, and properties are presented together with results from several prototypical applications of hyperbolic conservation laws including a nonlinear scalar equation, the Euler equations of gas dynamics, and the ideal magnetohydrodynamic equations. Parallel scaling analysis and grid-independent results including contours and isosurfaces of density and velocity and magnetic field vectors are shown in this study, confirming the ability of these types of solvers to approximate the solutions of hyperbolic equations efficiently and accurately.

  8. High-order Lagrangian cell-centered conservative scheme on unstructured meshes

    Institute of Scientific and Technical Information of China (English)

    葛全文

    2014-01-01

    A high-order Lagrangian cell-centered conservative gas dynamics scheme is presented on unstructured meshes. A high-order piecewise pressure of the cell is intro-duced. With the high-order piecewise pressure of the cell, the high-order spatial discretiza-tion fluxes are constructed. The time discretization of the spatial fluxes is performed by means of the Taylor expansions of the spatial discretization fluxes. The vertex velocities are evaluated in a consistent manner due to an original solver located at the nodes by means of momentum conservation. Many numerical tests are presented to demonstrate the robustness and the accuracy of the scheme.

  9. High-order conservative reconstruction schemes for finite volume methods in cylindrical and spherical coordinates

    CERN Document Server

    Mignone, A

    2014-01-01

    High-order reconstruction schemes for the solution of hyperbolic conservation laws in orthogonal curvilinear coordinates are revised in the finite volume approach. The formulation employs a piecewise polynomial approximation to the zone-average values to reconstruct left and right interface states from within a computational zone to arbitrary order of accuracy by inverting a Vandermonde-like linear system of equations with spatially varying coefficients. The approach is general and can be used on uniform and non-uniform meshes although explicit expressions are derived for polynomials from second to fifth degree in cylindrical and spherical geometries with uniform grid spacing. It is shown that, in regions of large curvature, the resulting expressions differ considerably from their Cartesian counterparts and that the lack of such corrections can severely degrade the accuracy of the solution close to the coordinate origin. Limiting techniques and monotonicity constraints are revised for conventional reconstruct...

  10. New parallelizable schemes for integrating the Dissipative Particle Dynamics with Energy Conservation

    CERN Document Server

    Homman, A -A; Roussel, J; Stoltz, G

    2015-01-01

    This work presents new parallelizable numerical schemes for the integration of Dissipative Particle Dynamics with Energy conservation (DPDE). So far, no numerical scheme presented in the literature is able to correctly preserve the energy over long times and give rise to small error on average properties for moderately small timesteps, while being straightforwardly parallelizable. We present in this article three new methods, all of them straightforwardly parallelizable, and allowing to correctly preserve the total energy of the system. We illustrate the accuracy and performance of these new schemes both on equilibrium and nonequilibrium parallel simulations.

  11. Additive Difference Schemes for Filtration Problems in Multilayer Systems

    CERN Document Server

    Ayrjan, E A; Pavlush, M; Fedorov, A V

    2000-01-01

    In the present paper difference schemes for solution of the plane filtration problem in multilayer systems are analyzed within the framework of difference schemes general theory. Attention is paid to splitting the schemes on physical processes of filtration along water-carring layers and vertical motion between layers. Some absolutely stable additive difference schemes are obtained the realization of which needs no software modification. Parallel algorithm connected with the solving of the filtration problem in every water-carring layer on a single processor is constructed. Program realization on the multi-processor system SPP2000 at JINR is discussed.

  12. A Stable Adaptive Numerical Scheme for Hyperbolic Conservation Laws.

    Science.gov (United States)

    1983-05-01

    expansion waves following shocks. These comparisons lead us to believe that our method is superior to fixed mesh mono- tone methods when the...generated niuch superior code for index calculations. Function calls were slightly cheaper because the FORTRAN program, not being block structured, did...Nazionale di Alta Matematica "Francesco Severi." Roma, 1980. 8. J. Douglas Jr. & M. F. Wheeler, "Implicit, time-dependent variable grid finite difference

  13. EXPLICIT SQUARE CONSERVING SCHEMES OF LANDAU-LIFSHITZ EQUATION WITH GILBERT COMPONENT

    Institute of Scientific and Technical Information of China (English)

    孙建强; 马中骐; 秦孟兆

    2005-01-01

    A kind of explicit square-conserving scheme is proposed for the Landau-Lifshitz equation with Gilbert component. The basic idea was to semidiscrete the Landau-Lifshitz equation into the ordinary differential equations. Then the Lie group method and the RungeKutta (RK) method were applied to the ordinary differential equations. The square conserving property and the accuracy of the two methods were compared. Numerical experiment results show the Lie group method has the good accuracy and the square conserving property than the RK method.

  14. ON A CELL ENTROPY INEQUALITY OF THE RELAXING SCHEMES FOR SCALAR CONSERVATION LAWS

    Institute of Scientific and Technical Information of China (English)

    Hua-zhong Tang; Hua-mo Wu

    2000-01-01

    In this paper we study a cell entropy inequality for a class of the local relaxation approximation -The Relaxing Schemes for scalar conservation laws presented by Jin and Xin in [1], which implies convergence for the one-dimensional scalar case.

  15. Unconditional convergence of two conservative compact difference schemes for non-linear Schr(o)dinger equation in one dimension%一维非线性Schr(o)dinger方程的两个无条件收敛的守恒紧致差分格式

    Institute of Scientific and Technical Information of China (English)

    王廷春; 郭柏灵

    2011-01-01

    Two compact difference schemes for one-dimensional cubic nonlinear Schrodinger equation are proposed. Both of the schemes are proved to conserve the discrete mass and energy. Unconditional convergence in maximum norm of the difference solutions with forth order in space and second order in time is also proved by utilizing the discrete energy method and two techniques. For computing the nonlinear algebraical system generated by the nonlinear compact scheme, an iterative algorithm is constructed and proved to be convergent. As a byproduct of the iterative algorithm, a linearized compact difference scheme with high accuracy is obtained. Numerical examples are given to support the theoretical analysis, and two Richardson extrapolations are introduced to achieve higher order numerical accuracy.%本文对一维非线性Schr(o)dinger方程给出两个紧致差分格式,运用能量方法和两个新的分析技巧证明格式关于离散质量和离散能量守恒,而且在最大模意义下无条件收敛.对非线性紧格式构造了一个新的迭代算法,证明了算法的收敛性,并在此基础上给出一个新的线性化紧格式.数值算例验证了理论分析的正确性,并通过外推进一步提高了数值解的精度.

  16. NUMERICAL SIMULATIONS OF SEA ICE WITH DIFFERENT ADVECTION SCHEMES

    Institute of Scientific and Technical Information of China (English)

    LIU Xi-ying

    2011-01-01

    Numerical simulations are carried out for sea ice with four different advection schemes to study their effects on the simulation results.The sea ice model employed here is the Sea Ice Simulator (SIS) of the Geophysical Fluid Dynamics Laboratory (GFDL) Modular Ocean Model version 4b (MOM4b) and the four advection schemes are, the upwind scheme originally used in the SIS, the Multi-Dimensional Positive Advection (MDPA) scheme, the Incremental Remapping Scheme (IRS) and the Two Step Shape Preserving (TSSP) scheme.The latter three schemes are newly introduced.To consider the interactions between sea ice and ocean, a mixed layer ocean model is introduced and coupled to the SIS.The coupled model uses a tri-polar coordinate with 120×65 grids,covering the whole earth globe, in the horizontal plane.Simulation results in the northern high latitudes are analyzed.In all simulations, the model reproduces the seasonal variation of sea ice in the northern high latitudes well.Compared with the results from the observation, the sea ice model produces some extra sea ice coverage in the Greenland Sea and Barents Sea in winter due to the exclusion of ocean current effects and the smaller simulated sea ice thickness in the Arctic basin.There are similar features among the results obtained with the introduced three advection schemes.The simulated sea ice thickness with the three newly introduced schemes are all smaller than that of the upwind scheme and the simulated sea ice velocities of movement are all smaller than that of the upwind scheme.There are more similarities shared in the results obtained with the MPDA and TSSP schemes.

  17. Malware Detection with Different Voting Schemes

    Directory of Open Access Journals (Sweden)

    Ms. Jyoti Landage

    2014-01-01

    Full Text Available A common way of launching the attack in computer system is Malware. It has malicious intent of performing any kind of malicious action to computer system as a result entire system crashes. It comes in different forms like virus, Trojan , Spyware, Scareware, Adware etc. Traditional malware detection techniques viz. signature-based, Heuristic-based and Specification-based detection technique are unable to detect some form of malware and each technique has its own advantages and disadvantages. A new methodology is proposed for malware detection that is based on data mining and machine learning techniques to detect known as well as unknown instances of malware. The new methodology uses disassemble process and three pre -processing techniques as part of feature extraction process to produce three different data sets with different configurations; feature selection technique is used to achieve consistent, reduced feature dataset. Three classification algorithms are used to gener ate and train the classifiers named as Ripper, C4.5 and IBk. The ensemble learning algorithm voting is used to improve the accuracy of result. Here majority voting and veto voting is used, the predicted output is decided on the basis of majority vo ting and veto voting. In veto voting the decision strategy of veto is improved by introducing the trust-based veto voting that definitely helps to improve the detection accuracy.

  18. Malware Detection with Different Voting Schemes

    Directory of Open Access Journals (Sweden)

    Jyoti Landage

    2015-10-01

    Full Text Available A common way of launching the attack in computer system is Malware. It has malicious intent of performing any kind of malicious action to computer system as a result entire system crashes. It comes in different forms like virus, Trojan , Spyware, Scareware, Adware etc. Traditional malware detection techniques viz. signature-based, Heuristic-based and Specification-based detection technique are unable to detect some form of malware and each technique has its own advantages and disadvantages. A new methodology is proposed for malware detection that is based on data mining and machine learning techniques to detect known as well as unknown instances of malware. The new methodology uses disassemble process and three pre -processing techniques as part of feature ext raction process to produce three different data sets with different configurations; feature selection technique is used to achieve consistent, reduced feature dataset. Three classification algorithms are used to gener ate and train the classifiers named as Ripper, C4.5 and IBk. The ensemble learning algorithm voting is used to improve the accuracy of result. Here majority voting and veto voting is used, the predicted output is decided on the basis of majority vo ting and veto voting. In veto voting the decision strategy of veto is improved by introducing the trust -based veto voting that definitely helps to improve the detection accuracy.

  19. Higher order finite difference schemes for the magnetic induction equations

    CERN Document Server

    Koley, Ujjwal; Risebro, Nils Henrik; Svärd, Magnus

    2011-01-01

    We describe high order accurate and stable finite difference schemes for the initial-boundary value problem associated with the magnetic induction equations. These equations model the evolution of a magnetic field due to a given velocity field. The finite difference schemes are based on Summation by Parts (SBP) operators for spatial derivatives and a Simultaneous Approximation Term (SAT) technique for imposing boundary conditions. We present various numerical experiments that demonstrate both the stability as well as high order of accuracy of the schemes.

  20. Explicit Runge-Kutta schemes for incompressible flow with improved energy-conservation properties

    Science.gov (United States)

    Capuano, F.; Coppola, G.; Rández, L.; de Luca, L.

    2017-01-01

    The application of pseudo-symplectic Runge-Kutta methods to the incompressible Navier-Stokes equations is discussed in this work. In contrast to fully energy-conserving, implicit methods, these are explicit schemes of order p that preserve kinetic energy to order q, with q > p. Use of explicit methods with improved energy-conservation properties is appealing for convection-dominated problems, especially in case of direct and large-eddy simulation of turbulent flows. A number of pseudo-symplectic methods are constructed for application to the incompressible Navier-Stokes equations and compared in terms of accuracy and efficiency by means of numerical simulations.

  1. On the application of ENO scheme with subcell resolution to conservation laws with stiff source terms

    Science.gov (United States)

    Chang, Shih-Hung

    1991-01-01

    Two approaches are used to extend the essentially non-oscillatory (ENO) schemes to treat conservation laws with stiff source terms. One approach is the application of the Strang time-splitting method. Here the basic ENO scheme and the Harten modification using subcell resolution (SR), ENO/SR scheme, are extended this way. The other approach is a direct method and a modification of the ENO/SR. Here the technique of ENO reconstruction with subcell resolution is used to locate the discontinuity within a cell and the time evolution is then accomplished by solving the differential equation along characteristics locally and advancing in the characteristic direction. This scheme is denoted ENO/SRCD (subcell resolution - characteristic direction). All the schemes are tested on the equation of LeVeque and Yee (NASA-TM-100075, 1988) modeling reacting flow problems. Numerical results show that these schemes handle this intriguing model problem very well, especially with ENO/SRCD which produces perfect resolution at the discontinuity.

  2. A study on scheme of soil and water conservation regionalization in China

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yan; WANG Zhiguo; SUN Baoping; ZHANG Chao; JI Qiang; FENG Lei; SHI Mingchang

    2013-01-01

    Regionalization of soil and water conservation is a base for the planning of soil and water conservation in China.It can provide scientific basis for constructing healthy eco-environment and regional management and development.It makes a brief review of related regionalization of study and makes clear the concept of regionalization of soil and water conservation.In this paper,based on synthetical analysis of the characteristics of eco-environments of China,the principles,indices and nomenclature of the regionalization of soil and water conservation are proposed.Through the construction of the regionalization of soil and water conservation collaboration platform and data reporting system,combined with existing soil and water conservation research,this paper uses the top-down and bottom-up and the combination of qualitative and quantitative methods to build soil and water conservation regionalization preliminary scheme,with 8 regions,41 sub-regions and 117 sections divided in China.

  3. Optimized difference schemes for multidimensional hyperbolic partial differential equations

    Directory of Open Access Journals (Sweden)

    Adrian Sescu

    2009-04-01

    Full Text Available In numerical solutions to hyperbolic partial differential equations in multidimensions, in addition to dispersion and dissipation errors, there is a grid-related error (referred to as isotropy error or numerical anisotropy that affects the directional dependence of the wave propagation. Difference schemes are mostly analyzed and optimized in one dimension, wherein the anisotropy correction may not be effective enough. In this work, optimized multidimensional difference schemes with arbitrary order of accuracy are designed to have improved isotropy compared to conventional schemes. The derivation is performed based on Taylor series expansion and Fourier analysis. The schemes are restricted to equally-spaced Cartesian grids, so the generalized curvilinear transformation method and Cartesian grid methods are good candidates.

  4. A discontinuous Galerkin conservative level set scheme for interface capturing in multiphase flows

    Energy Technology Data Exchange (ETDEWEB)

    Owkes, Mark, E-mail: mfc86@cornell.edu; Desjardins, Olivier

    2013-09-15

    The accurate conservative level set (ACLS) method of Desjardins et al. [O. Desjardins, V. Moureau, H. Pitsch, An accurate conservative level set/ghost fluid method for simulating turbulent atomization, J. Comput. Phys. 227 (18) (2008) 8395–8416] is extended by using a discontinuous Galerkin (DG) discretization. DG allows for the scheme to have an arbitrarily high order of accuracy with the smallest possible computational stencil resulting in an accurate method with good parallel scaling. This work includes a DG implementation of the level set transport equation, which moves the level set with the flow field velocity, and a DG implementation of the reinitialization equation, which is used to maintain the shape of the level set profile to promote good mass conservation. A near second order converging interface curvature is obtained by following a height function methodology (common amongst volume of fluid schemes) in the context of the conservative level set. Various numerical experiments are conducted to test the properties of the method and show excellent results, even on coarse meshes. The tests include Zalesak’s disk, two-dimensional deformation of a circle, time evolution of a standing wave, and a study of the Kelvin–Helmholtz instability. Finally, this novel methodology is employed to simulate the break-up of a turbulent liquid jet.

  5. An admissibility and asymptotic-preserving scheme for systems of conservation laws with source term on 2D unstructured meshes

    Science.gov (United States)

    Blachère, F.; Turpault, R.

    2016-06-01

    The objective of this work is to design explicit finite volumes schemes for specific systems of conservations laws with stiff source terms, which degenerate into diffusion equations. We propose a general framework to design an asymptotic preserving scheme, that is stable and consistent under a classical hyperbolic CFL condition in both hyperbolic and diffusive regime, for any two-dimensional unstructured mesh. Moreover, the scheme developed also preserves the set of admissible states, which is mandatory to keep physical solutions in stiff configurations. This construction is achieved by using a non-linear scheme as a target scheme for the diffusive equation, which gives the form of the global scheme for the complete system of conservation laws. Numerical results are provided to validate the scheme in both regimes.

  6. A conservative and a hybrid early rejection schemes for accelerating Monte Carlo molecular simulation

    KAUST Repository

    Kadoura, Ahmad Salim

    2014-03-17

    Molecular simulation could provide detailed description of fluid systems when compared to experimental techniques. They can also replace equations of state; however, molecular simulation usually costs considerable computational efforts. Several techniques have been developed to overcome such high computational costs. In this paper, two early rejection schemes, a conservative and a hybrid one, are introduced. In these two methods, undesired configurations generated by the Monte Carlo trials are rejected earlier than it would when using conventional algorithms. The methods are tested for structureless single-component Lennard-Jones particles in both canonical and NVT-Gibbs ensembles. The computational time reduction for both ensembles is observed at a wide range of thermodynamic conditions. Results show that computational time savings are directly proportional to the rejection rate of Monte Carlo trials. The proposed conservative scheme has shown to be successful in saving up to 40% of the computational time in the canonical ensemble and up to 30% in the NVT-Gibbs ensemble when compared to standard algorithms. In addition, it preserves the exact Markov chains produced by the Metropolis scheme. Further enhancement for NVT-Gibbs ensemble is achieved by combining this technique with the bond formation early rejection one. The hybrid method achieves more than 50% saving of the central processing unit (CPU) time.

  7. The standard upwind compact difference schemes for incompressible flow simulations

    Science.gov (United States)

    Fan, Ping

    2016-10-01

    Compact difference schemes have been used extensively for solving the incompressible Navier-Stokes equations. However, the earlier formulations of the schemes are of central type (called central compact schemes, CCS), which are dispersive and susceptible to numerical instability. To enhance stability of CCS, the optimal upwind compact schemes (OUCS) are developed recently by adding high order dissipative terms to CCS. In this paper, it is found that OUCS are essentially not of the upwind type because they do not use upwind-biased but central type of stencils. Furthermore, OUCS are not the most optimal since orders of accuracy of OUCS are at least one order lower than the maximum achievable orders. New upwind compact schemes (called standard upwind compact schemes, SUCS) are developed in this paper. In contrast to OUCS, SUCS are constructed based completely on upwind-biased stencils and hence can gain adequate numerical dissipation with no need for introducing optimization calculations. Furthermore, SUCS can achieve the maximum achievable orders of accuracy and hence be more compact than OUCS. More importantly, SUCS have prominent advantages on combining the stable and high resolution properties which are demonstrated from the global spectral analyses and typical numerical experiments.

  8. Contaminant flow and transport simulation in cracked porous media using locally conservative schemes

    KAUST Repository

    Song, Pu

    2012-10-25

    The purpose of this paper is to analyze some features of contaminant flow passing through cracked porous medium, such as the influence of fracture network on the advection and diffusion of contaminant species, the impact of adsorption on the overall transport of contaminant wastes. In order to precisely describe the whole process, we firstly build the mathematical model to simulate this problem numerically. Taking into consideration of the characteristics of contaminant flow, we employ two partial differential equations to formulate the whole problem. One is flow equation; the other is reactive transport equation. The first equation is used to describe the total flow of contaminant wastes, which is based on Darcy law. The second one will characterize the adsorption, diffusion and convection behavior of contaminant species, which describes most features of contaminant flow we are interested in. After the construction of numerical model, we apply locally conservative and compatible algorithms to solve this mathematical model. Specifically, we apply Mixed Finite Element (MFE) method to the flow equation and Discontinuous Galerkin (DG) method for the transport equation. MFE has a good convergence rate and numerical accuracy for Darcy velocity. DG is more flexible and can be used to deal with irregular meshes, as well as little numerical diffusion. With these two numerical means, we investigate the sensitivity analysis of different features of contaminant flow in our model, such as diffusion, permeability and fracture density. In particular, we study K d values which represent the distribution of contaminant wastes between the solid and liquid phases. We also make omparisons of two different schemes and discuss the advantages of both methods. © 2012 Global Science Press.

  9. Dimensionally Split Higher Order Semi-discrete Central Scheme for Multi-dimensional Conservation Laws

    CERN Document Server

    Verma, Prabal Singh

    2015-01-01

    The dimensionally split reconstruction method as described by Kurganov et al.\\cite{kurganov-2000} is revisited for better understanding and a simple fourth order scheme is introduced to solve 3D hyperbolic conservation laws following dimension by dimension approach. Fourth order central weighted essentially non-oscillatory (CWENO) reconstruction methods have already been proposed to study multidimensional problems \\cite{lpr4,cs12}. In this paper, it is demonstrated that a simple 1D fourth order CWENO reconstruction method by Levy et al.\\cite{lpr7} provides fourth order accuracy for 3D hyperbolic nonlinear problems when combined with the semi-discrete scheme by Kurganov et al.\\cite{kurganov-2000} and fourth order Runge-Kutta method for time integration.

  10. The Space-Time Conservative Schemes for Large-Scale, Time-Accurate Flow Simulations with Tetrahedral Meshes

    Science.gov (United States)

    Venkatachari, Balaji Shankar; Streett, Craig L.; Chang, Chau-Lyan; Friedlander, David J.; Wang, Xiao-Yen; Chang, Sin-Chung

    2016-01-01

    Despite decades of development of unstructured mesh methods, high-fidelity time-accurate simulations are still predominantly carried out on structured, or unstructured hexahedral meshes by using high-order finite-difference, weighted essentially non-oscillatory (WENO), or hybrid schemes formed by their combinations. In this work, the space-time conservation element solution element (CESE) method is used to simulate several flow problems including supersonic jet/shock interaction and its impact on launch vehicle acoustics, and direct numerical simulations of turbulent flows using tetrahedral meshes. This paper provides a status report for the continuing development of the space-time conservation element solution element (CESE) numerical and software framework under the Revolutionary Computational Aerosciences (RCA) project. Solution accuracy and large-scale parallel performance of the numerical framework is assessed with the goal of providing a viable paradigm for future high-fidelity flow physics simulations.

  11. An assessment of semi-discrete central schemes for hyperbolic conservation laws.

    Energy Technology Data Exchange (ETDEWEB)

    Christon, Mark Allen; Robinson, Allen Conrad; Ketcheson, David Isaac

    2003-09-01

    High-resolution finite volume methods for solving systems of conservation laws have been widely embraced in research areas ranging from astrophysics to geophysics and aero-thermodynamics. These methods are typically at least second-order accurate in space and time, deliver non-oscillatory solutions in the presence of near discontinuities, e.g., shocks, and introduce minimal dispersive and diffusive effects. High-resolution methods promise to provide greatly enhanced solution methods for Sandia's mainstream shock hydrodynamics and compressible flow applications, and they admit the possibility of a generalized framework for treating multi-physics problems such as the coupled hydrodynamics, electro-magnetics and radiative transport found in Z pinch physics. In this work, we describe initial efforts to develop a generalized 'black-box' conservation law framework based on modern high-resolution methods and implemented in an object-oriented software framework. The framework is based on the solution of systems of general non-linear hyperbolic conservation laws using Godunov-type central schemes. In our initial efforts, we have focused on central or central-upwind schemes that can be implemented with only a knowledge of the physical flux function and the minimal/maximal eigenvalues of the Jacobian of the flux functions, i.e., they do not rely on extensive Riemann decompositions. Initial experimentation with high-resolution central schemes suggests that contact discontinuities with the concomitant linearly degenerate eigenvalues of the flux Jacobian do not pose algorithmic difficulties. However, central schemes can produce significant smearing of contact discontinuities and excessive dissipation for rotational flows. Comparisons between 'black-box' central schemes and the piecewise parabolic method (PPM), which relies heavily on a Riemann decomposition, shows that roughly equivalent accuracy can be achieved for the same computational cost with both

  12. Gröbner Bases and Generation of Difference Schemes for Partial Differential Equations

    Directory of Open Access Journals (Sweden)

    Vladimir P. Gerdt

    2006-05-01

    Full Text Available In this paper we present an algorithmic approach to the generation of fully conservative difference schemes for linear partial differential equations. The approach is based on enlargement of the equations in their integral conservation law form by extra integral relations between unknown functions and their derivatives, and on discretization of the obtained system. The structure of the discrete system depends on numerical approximation methods for the integrals occurring in the enlarged system. As a result of the discretization, a system of linear polynomial difference equations is derived for the unknown functions and their partial derivatives. A difference scheme is constructed by elimination of all the partial derivatives. The elimination can be achieved by selecting a proper elimination ranking and by computing a Gröbner basis of the linear difference ideal generated by the polynomials in the discrete system. For these purposes we use the difference form of Janet-like Gröbner bases and their implementation in Maple. As illustration of the described methods and algorithms, we construct a number of difference schemes for Burgers and Falkowich-Karman equations and discuss their numerical properties.

  13. Tetrahedral-Mesh Simulation of Turbulent Flows with the Space-Time Conservative Schemes

    Science.gov (United States)

    Chang, Chau-Lyan; Venkatachari, Balaji; Cheng, Gary C.

    2015-01-01

    Direct numerical simulations of turbulent flows are predominantly carried out using structured, hexahedral meshes despite decades of development in unstructured mesh methods. Tetrahedral meshes offer ease of mesh generation around complex geometries and the potential of an orientation free grid that would provide un-biased small-scale dissipation and more accurate intermediate scale solutions. However, due to the lack of consistent multi-dimensional numerical formulations in conventional schemes for triangular and tetrahedral meshes at the cell interfaces, numerical issues exist when flow discontinuities or stagnation regions are present. The space-time conservative conservation element solution element (CESE) method - due to its Riemann-solver-free shock capturing capabilities, non-dissipative baseline schemes, and flux conservation in time as well as space - has the potential to more accurately simulate turbulent flows using unstructured tetrahedral meshes. To pave the way towards accurate simulation of shock/turbulent boundary-layer interaction, a series of wave and shock interaction benchmark problems that increase in complexity, are computed in this paper with triangular/tetrahedral meshes. Preliminary computations for the normal shock/turbulence interactions are carried out with a relatively coarse mesh, by direct numerical simulations standards, in order to assess other effects such as boundary conditions and the necessity of a buffer domain. The results indicate that qualitative agreement with previous studies can be obtained for flows where, strong shocks co-exist along with unsteady waves that display a broad range of scales, with a relatively compact computational domain and less stringent requirements for grid clustering near the shock. With the space-time conservation properties, stable solutions without any spurious wave reflections can be obtained without a need for buffer domains near the outflow/farfield boundaries. Computational results for the

  14. Maximum-principle-satisfying space-time conservation element and solution element scheme applied to compressible multifluids

    KAUST Repository

    Shen, Hua

    2016-10-19

    A maximum-principle-satisfying space-time conservation element and solution element (CE/SE) scheme is constructed to solve a reduced five-equation model coupled with the stiffened equation of state for compressible multifluids. We first derive a sufficient condition for CE/SE schemes to satisfy maximum-principle when solving a general conservation law. And then we introduce a slope limiter to ensure the sufficient condition which is applicative for both central and upwind CE/SE schemes. Finally, we implement the upwind maximum-principle-satisfying CE/SE scheme to solve the volume-fraction-based five-equation model for compressible multifluids. Several numerical examples are carried out to carefully examine the accuracy, efficiency, conservativeness and maximum-principle-satisfying property of the proposed approach.

  15. Test of some numerical limiters for the conservative PSM scheme for 4D Drift-Kinetic simulations

    CERN Document Server

    Guterl, Jerome; Crouseilles, Nicolas; Grandgirard, Virginie; Latu, Guillaume; Mehrenberger, Michel; Sonnendrücker, Eric

    2010-01-01

    The purpose of this work is simulation of magnetised plasmas in the ITER project framework. In this context, Vlasov-Poisson like models are used to simulate core turbulence in the tokamak in a toroidal geometry. This leads to heavy simulation because a 6D dimensional problem has to be solved, 3D in space and 3D in velocity. The model is reduced to a 5D gyrokinetic model, taking advantage of the particular motion of particles due to the presence of a strong magnetic field. However, accurate schemes, parallel algorithms need to be designed to bear these simulations. This paper describes a Hermite formulation of the conservative PSM scheme which is very generic and allows to implement different semi-Lagrangian schemes. We also test and propose numerical limiters which should improve the robustness of the simulations by diminishing spurious oscillations. We only consider here the 4D drift-kinetic model which is the backbone of the 5D gyrokinetic models and relevant to build a robust and accurate numerical method.

  16. A conservative orbital advection scheme for simulations of magnetized shear flows with the PLUTO code

    Science.gov (United States)

    Mignone, A.; Flock, M.; Stute, M.; Kolb, S. M.; Muscianisi, G.

    2012-09-01

    Context. Explicit numerical computations of hypersonic or super-fast differentially rotating disks are subject to the time-step constraint imposed by the Courant condition, according to which waves cannot travel more than a fraction of a cell during a single time-step update. When the bulk orbital velocity largely exceeds any other wave speed (e.g., sound or Alfvén), as computed in the rest frame, the time step is considerably reduced and an unusually large number of steps may be necessary to complete the computation. Aims: We present a robust numerical scheme to overcome the Courant limitation by improving and extending the algorithm previously known as FARGO (fast advection in rotating gaseous objects) to the equations of magnetohydrodynamics (MHD) using a more general formalism. The proposed scheme conserves total angular momentum and energy to machine precision and works in cartesian, cylindrical, or spherical coordinates. The algorithm has been implemented in the next release of the PLUTO code for astrophysical gasdynamics and is suitable for local or global simulations of accretion or proto-planetary disk models. Methods: By decomposing the total velocity into an average azimuthal contribution and a residual term, the algorithm approaches the solution of the MHD equations through two separate steps corresponding to a linear transport operator in the direction of orbital motion and a standard nonlinear solver applied to the MHD equations written in terms of the residual velocity. Since the former step is not subject to any stability restriction, the Courant condition is computed only in terms of the residual velocity, leading to substantially larger time steps. The magnetic field is advanced in time using the constrained transport method in order to fulfill the divergence-free condition. Furthermore, conservation of total energy and angular momentum is enforced at the discrete level by properly expressing the source terms in terms of upwind Godunov fluxes

  17. General difference schemes with intrinsic parallelism for nonlinear parabolic systems

    Institute of Scientific and Technical Information of China (English)

    周毓麟; 袁光伟

    1997-01-01

    The boundary value problem for nonlinear parabolic system is solved by the finite difference method with intrinsic parallelism. The existence of the discrete vector solution for the general finite difference schemes with intrinsic parallelism is proved by the fixed-point technique in finite-dimensional Euclidean space. The convergence and stability theorems of the discrete vector solutions of the nonlinear difference system with intrinsic parallelism are proved. The limitation vector function is just the unique generalized solution of the original problem for the parabolic system.

  18. Finite Difference Weighted Essentially Non-Oscillatory Schemes with Constrained Transport for Ideal Magnetohydrodynamics

    CERN Document Server

    Christlieb, Andrew J; Tang, Qi

    2013-01-01

    In this work we develop a class of high-order finite difference weighted essentially non-oscillatory (FD-WENO) schemes for solving the ideal magnetohydrodynamic (MHD) equations in 2D and 3D. The philosophy of this work is to use efficient high-order WENO spatial discretizations with high-order strong stability-preserving Runge-Kutta (SSP-RK) time-stepping schemes. Numerical results have shown that with such methods we are able to resolve solution structures that are only visible at much higher grid resolutions with lower-order schemes. The key challenge in applying such methods to ideal MHD is to control divergence errors in the magnetic field. We achieve this by augmenting the base scheme with a novel high-order constrained transport approach that updates the magnetic vector potential. The predicted magnetic field from the base scheme is replaced by a divergence-free magnetic field that is obtained from the curl of this magnetic potential. The non-conservative weakly hyperbolic system that the magnetic vecto...

  19. Transporter taxonomy - a comparison of different transport protein classification schemes.

    Science.gov (United States)

    Viereck, Michael; Gaulton, Anna; Digles, Daniela; Ecker, Gerhard F

    2014-06-01

    Currently, there are more than 800 well characterized human membrane transport proteins (including channels and transporters) and there are estimates that about 10% (approx. 2000) of all human genes are related to transport. Membrane transport proteins are of interest as potential drug targets, for drug delivery, and as a cause of side effects and drug–drug interactions. In light of the development of Open PHACTS, which provides an open pharmacological space, we analyzed selected membrane transport protein classification schemes (Transporter Classification Database, ChEMBL, IUPHAR/BPS Guide to Pharmacology, and Gene Ontology) for their ability to serve as a basis for pharmacology driven protein classification. A comparison of these membrane transport protein classification schemes by using a set of clinically relevant transporters as use-case reveals the strengths and weaknesses of the different taxonomy approaches.

  20. Altimeter data assimilation in the tropical Indian Ocean using water property conserving scheme

    Indian Academy of Sciences (India)

    Bhasha M Mankad; Rashmi Sharma; Sujit Basu; P K Pal

    2012-02-01

    Altimeter data have been assimilated in an ocean general circulation model using the water property conserving scheme. Two runs of the model have been conducted for the year 2004. In one of the runs, altimeter data have been assimilated sequentially, while in another run, assimilation has been suppressed. Assimilation has been restricted to the tropical Indian Ocean. An assessment of the strength of the scheme has been carried out by comparing the sea surface temperature (SST), simulated in the two runs, with in situ derived as well as remotely sensed observations of the same quantity. It has been found that the assimilation exhibits a significant positive impact on the simulation of SST. The subsurface effect of the assimilation could be judged by comparing the model simulated depth of the 20°C isotherm (hereafter referred to as D20), as a proxy of the thermocline depth, with the same quantity estimated from ARGO observations. In this case also, the impact is noteworthy. Effect on the dynamics has been judged by comparison of simulated surface current with observed current at a moored buoy location, and finally the impact on model sea level forecast in a free run after assimilation has been quantified in a representative example.

  1. A Conservation Voltage Reduction Scheme for a Distribution Systems with Intermittent Distributed Generators

    Directory of Open Access Journals (Sweden)

    Pyeong-Ik Hwang

    2016-08-01

    Full Text Available In this paper, a conservation voltage reduction (CVR scheme is proposed for a distribution system with intermittent distributed generators (DGs, such as photovoltaics and wind turbines. The CVR is a scheme designed to reduce energy consumption by lowering the voltages supplied to customers. Therefore, an unexpected under-voltage violation can occur due to the variation of active power output from the intermittent DGs. In order to prevent the under-voltage violation and improve the CVR effect, a new reactive power controller which complies with the IEEE Std. 1547TM, and a parameter determination method for the controller are proposed. In addition, an optimal power flow (OPF problem to determine references for the resources of CVR is formulated with consideration of the intermittent DGs. The proposed method is validated using a modified IEEE 123-node test feeder. With the proposed method, the voltages of the test system are maintained to be greater than the lower bound, even though the active power outputs of the DGs are varied. Moreover, the CVR effect is improved compared to that used with the conventional reactive power control methods.

  2. A FINITE DIFFERENCE SCHEME FOR THE GENERALIZED NONLINEAR SCHRODINGER EQUATION WITH VARIABLE COEFFICIENTS

    Institute of Scientific and Technical Information of China (English)

    Wei-zhong Dai; Raja Nassar

    2000-01-01

    A finite difference scheme for the generalized nonlinear Schrodinger equation with variable coefficients is developed. The scheme is shown to satisfy two conser vation laws. Numerical results show that the scheme is accurate and efficient.

  3. Some fundamental problems for an energy conserving adaptive resolution molecular dynamics scheme

    OpenAIRE

    Site, L. Delle

    2007-01-01

    Adaptive resolution molecular dynamics (MD) schemes allow for changing the number of degrees of freedom on the fly and preserve the free exchange of particles between regions of different resolution. There are two main alternatives on how to design the algorithm to switch resolution using auxiliary ''switching'' functions; force based and potential energy based approach. In this work we show that, in the framework of classical MD, the latter presents fundamental conceptual problems which make...

  4. Different acceptance functions for Multiple Try Metropolis schemes

    CERN Document Server

    Martino, Luca

    2012-01-01

    The Multiple Try Metropolis method is an extension of the classical Metropolis algorithm in which the next state of the chain is chosen among a set of samples, according to normalized weights. In literature, a generalization of this technique has been proposed in Pandolfi et al. (2010) where the weight functions are not analytically specified. In this work, we propose different Multiple Try Metropolis schemes where the analytic form of weight functions can be chosen arbitrarily. The resulting algorithms fulfill the detailed balance condition.

  5. The a(3) Scheme--A Fourth-Order Space-Time Flux-Conserving and Neutrally Stable CESE Solver

    Science.gov (United States)

    Chang, Sin-Chung

    2008-01-01

    The CESE development is driven by a belief that a solver should (i) enforce conservation laws in both space and time, and (ii) be built from a non-dissipative (i.e., neutrally stable) core scheme so that the numerical dissipation can be controlled effectively. To initiate a systematic CESE development of high order schemes, in this paper we provide a thorough discussion on the structure, consistency, stability, phase error, and accuracy of a new 4th-order space-time flux-conserving and neutrally stable CESE solver of an 1D scalar advection equation. The space-time stencil of this two-level explicit scheme is formed by one point at the upper time level and three points at the lower time level. Because it is associated with three independent mesh variables (the numerical analogues of the dependent variable and its 1st-order and 2ndorder spatial derivatives, respectively) and three equations per mesh point, the new scheme is referred to as the a(3) scheme. Through the von Neumann analysis, it is shown that the a(3) scheme is stable if and only if the Courant number is less than 0.5. Moreover, it is established numerically that the a(3) scheme is 4th-order accurate.

  6. Crab biodiversity under different management schemes of mangrove ecosystems

    Directory of Open Access Journals (Sweden)

    M. Bandibas

    2016-01-01

    Full Text Available Reforestation is one of the Philippines’ government efforts to restore and rehabilitate degraded mangrove ecosystems. Although there is recovery of the ecosystem in terms of vegetation, the recovery of closely-linked faunal species in terms of community structure is still understudied. This research investigates the community structure of mangrove crabs under two different management schemes: protected mangroves and reforested mangroves. The transect-plot method was employed in each management scheme to quantify the vegetation, crab assemblages and environmental variables. Community composition of crabs and mangrove trees were compared between protected and reforested mangroves using non-metric multi-dimensional scaling and analysis of similarity in PRIMER 6. Chi-squared was used to test the variance of sex ration of the crabs. Canonical Correspondence Analysis was used to determine the relationship between crabs and environmental parameters. A total of twelve species of crabs belonging to six families were identified in protected mangroves while only four species were documented in reforested mangroves. Perisesarma indiarum and Baptozius vinosus were the most dominant species in protected and reforested mangrove, respectively.  Univariate analysis of variance of crab assemblage data revealed significant differences in crab composition and abundance between protected mangroves and from reforested mangroves (P

  7. Implicit predictor-corrector central finite difference scheme for the equations of magnetohydrodynamic simulations

    Science.gov (United States)

    Tsai, T. C.; Yu, H.-S.; Hsieh, M.-S.; Lai, S. H.; Yang, Y.-H.

    2015-11-01

    Nowadays most of supercomputers are based on the frame of PC cluster; therefore, the efficiency of parallel computing is of importance especially with the increasing computing scale. This paper proposes a high-order implicit predictor-corrector central finite difference (iPCCFD) scheme and demonstrates its high efficiency in parallel computing. Of special interests are the large scale numerical studies such as the magnetohydrodynamic (MHD) simulations in the planetary magnetosphere. An iPCCFD scheme is developed based on fifth-order central finite difference method and fourth-order implicit predictor-corrector method in combination with elimination-of-the-round-off-errors (ERE) technique. We examine several numerical studies such as one-dimensional Brio-Wu shock tube problem, two-dimensional Orszag-Tang vortex system, vortex type K-H instability, kink type K-H instability, field loop advection, and blast wave. All the simulation results are consistent with many literatures. iPCCFD can minimize the numerical instabilities and noises along with the additional diffusion terms. All of our studies present relatively small numerical errors without employing any divergence-free reconstruction. In particular, we obtain fairly stable results in the two-dimensional Brio-Wu shock tube problem which well conserves ∇ ṡ B = 0 throughout the simulation. The ERE technique removes the accumulation of roundoff errors in the uniform or non-disturbed system. We have also shown that iPCCFD is characterized by the high order of accuracy and the low numerical dissipation in the circularly polarized Alfvén wave tests. The proposed iPCCFD scheme is a parallel-efficient and high precision numerical scheme for solving the MHD equations in hyperbolic conservation systems.

  8. CONVERGENCE OF THE LAX-FRIEDRICHS SCHEME AND STABILITY FOR CONSERVATION LAWS WITH A DISCONTINUOUS SPACE-TIME DEPENDENT FLUX

    Institute of Scientific and Technical Information of China (English)

    K. H. KARLSEN; J. D. TOWERS

    2004-01-01

    The authors give the first convergence proof for the Lax-Friedrichs finite difference scheme for non-convex genuinely nonlinear scalar conservation laws of the form ut+ f(k(x, t), u)x = 0,where the coefficient k(x, t) is allowed to be discontinuous along curves in the (x, t)plane. In contrast to most of the existing literature on problems with discontinuous coefficients, here the convergence proof is not based on the singular mapping approach,but rather on the div-curl lemma (but not the Young measure) and a Lax type entropy estimate that is robust with respect to the regularity of k(x, t). Following [14],the authors propose a definition of entropy solution that extends the classical Kruzkov definition to the situation where k(x, t) is piecewise Lipschitz continuous in the (x, t)plane, and prove the stability (uniqueness) of such entropy solutions, provided that the flux function satisfies a so-called crossing condition, and that strong traces of the solution exist along the curves where k(x, t) is discontinuous. It is shown that a convergent subsequence of approximations produced by the Lax-Friedrichs scheme converges to such an entropy solution, implying that the entire computed sequence converges.

  9. An Explicit Modulus Square Conserving Scheme for Kdv Equation%求解Kdv方程的一种显式模平方守恒格式

    Institute of Scientific and Technical Information of China (English)

    胡勋锋; 孙建强; 李昊辰

    2011-01-01

    利用Magnus方法求解Kdv方程.Kdv方程具有模平方守恒特性,首先用适当差分格式对其进行模平方守恒空间离散,转化成模平方守恒的常微分方程,再用Magnus方法求解.数值结果表明,Magnus方法能保Kdv方程模平方守恒特性.%In our report, the magnus method was used to solve Kdv equation, which has the modulus square conserving property. The proper difference scheme was used to discretizate it along the modulus square conservation special direction, and which is transformed into the modulus square conserving ordinary differential equation. The magnus method was used to solve the ordinary differential equations. The numerical results indicated that the Magnus method preserve the modulus square conserving property of the Kdv equation.

  10. Performance Evaluation of Different Data Value Prediction Schemes

    Institute of Scientific and Technical Information of China (English)

    Yong Xiao; Xing-Ming Zhou

    2005-01-01

    Data value prediction has been widely accepted as an effective mechanism to break data hazards for high performance processor design. Several works have reported promising performance potential. However, there is hardly enough information that is presented in a clear way about performance comparison of these prediction mechanisms. This paper investigates the performance impact of four previously proposed value predictors, namely last value predictor, stride value predictor, two-level value predictor and hybrid (stride+two-level) predictor. The impact of misprediction penalty,which has been frequently ignored, is discussed in detail. Several other implementation issues, including instruction window size, issue width and branch predictor are also addressed and simulated. Simulation results indicate that data value predictors act differently under different configurations. In some cases, simpler schemes may be more beneficial than complicated ones.In some particular cases, value prediction may have negative impact on performance.

  11. HIGH RESOLUTION SCHEMES FOR CONSERVATION LAWS AND CONVECTION-DIFFUSION EQUATIONS WITH VARYING TIME AND SPACE GRIDS

    Institute of Scientific and Technical Information of China (English)

    Hua-zhong Tang; Gerald Warnecke

    2006-01-01

    This paper presents a class of high resolution local time step schemes for nonlinear hyperbolic conservation laws and the closely related convection-diffusion equations, by projecting the solution increments of the underlying partial differential equations (PDE)at each local time step. The main advantages are that they are of good consistency, and it is convenient to implement them. The schemes are L∞ stable, satisfy a cell entropy inequality, and may be extended to the initial boundary value problem of general unsteady PDEs with higher-order spatial derivatives. The high resolution schemes are given by combining the reconstruction technique with a second order TVD Runge-Kutta scheme or a Lax-Wendroff type method, respectively.The schemes are used to solve a linear convection-diffusion equation, the nonlinear inviscid Burgers' equation, the one- and two-dimensional compressible Euler equations, and the two-dimensional incompressible Navier-Stokes equations. The numerical results show that the schemes are of higher-order accuracy, and efficient in saving computational cost,especially, for the case of combining the present schemes with the adaptive mesh method [15]. The correct locations of the slow moving or stronger discontinuities are also obtained,although the schemes are slightly nonconservative.

  12. Semi-implicit scheme for treating radiation under M1 closure in general relativistic conservative fluid dynamics codes

    CERN Document Server

    Sdowski, Aleksander; Tchekhovskoy, Alexander; Zhu, Yucong

    2012-01-01

    A numerical scheme is described for including radiation in multi-dimensional general-relativistic conservative fluid dynamics codes. In this method, a covariant form of the M1 closure scheme is used to close the radiation moments, and the radiative source terms are treated semi-implicitly in order to handle both optically thin and optically thick regimes. The scheme has been implemented in a conservative general relativistic radiation hydrodynamics code KORAL. The robustness of the code is demonstrated on a number of test problems, including radiative relativistic shock tubes, static radiation pressure supported atmosphere, shadows, beams of light in curved spacetime, and radiative Bondi accretion. The advantages of M1 closure relative to other approaches such as Eddington closure and flux-limited diffusion are discussed, and its limitations are also highlighted.

  13. The role of agri-environment schemes in conservation and environmental management

    Science.gov (United States)

    Batáry, Péter; Dicks, Lynn V; Kleijn, David; Sutherland, William J

    2015-01-01

    Over half of the European landscape is under agricultural management and has been for millennia. Many species and ecosystems of conservation concern in Europe depend on agricultural management and are showing ongoing declines. Agri-environment schemes (AES) are designed partly to address this. They are a major source of nature conservation funding within the European Union (EU) and the highest conservation expenditure in Europe. We reviewed the structure of current AES across Europe. Since a 2003 review questioned the overall effectiveness of AES for biodiversity, there has been a plethora of case studies and meta-analyses examining their effectiveness. Most syntheses demonstrate general increases in farmland biodiversity in response to AES, with the size of the effect depending on the structure and management of the surrounding landscape. This is important in the light of successive EU enlargement and ongoing reforms of AES. We examined the change in effect size over time by merging the data sets of 3 recent meta-analyses and found that schemes implemented after revision of the EU's agri-environmental programs in 2007 were not more effective than schemes implemented before revision. Furthermore, schemes aimed at areas out of production (such as field margins and hedgerows) are more effective at enhancing species richness than those aimed at productive areas (such as arable crops or grasslands). Outstanding research questions include whether AES enhance ecosystem services, whether they are more effective in agriculturally marginal areas than in intensively farmed areas, whether they are more or less cost-effective for farmland biodiversity than protected areas, and how much their effectiveness is influenced by farmer training and advice? The general lesson from the European experience is that AES can be effective for conserving wildlife on farmland, but they are expensive and need to be carefully designed and targeted. El Papel de los Esquemas Agro-Ambientales en

  14. Synchronization of Boolean Networks with Different Update Schemes.

    Science.gov (United States)

    Zhang, Hao; Wang, Xingyuan; Lin, Xiaohui

    2014-01-01

    In this paper, the synchronizations of Boolean networks with different update schemes (synchronized Boolean networks and asynchronous Boolean networks) are investigated. All nodes in Boolean network are represented in terms of semi-tensor product. First, we give the concept of inner synchronization and observe that all nodes in a Boolean network are synchronized with each other. Second, we investigate the outer synchronization between a driving Boolean network and a corresponding response Boolean network. We provide not only the concept of traditional complete synchronization, but also the anti-synchronization and get the anti-synchronization in simulation. Third, we extend the outer synchronization to asynchronous Boolean network and get the complete synchronization between an asynchronous Boolean network and a response Boolean network. Consequently, theorems for synchronization of Boolean networks and asynchronous Boolean networks are derived. Examples are provided to show the correctness of our theorems.

  15. A Study on an Energy Conservation and Interconnection Scheme between WSN and Internet Based on the 6LoWPAN

    Directory of Open Access Journals (Sweden)

    Runtong Zhang

    2015-01-01

    Full Text Available Wireless sensor network (WSN, which has broad application prospects, consists of small nodes with sensing, computation, and communications capabilities. IPv6 is used over low power WPAN (wireless personal area network which is run by 6LoWPAN technology on the LoWPAN devices. In order to establish seamless connection of two heterogeneous networks, that is, WSN and IPv6 network, this paper proposes an improved energy conservation and interconnection scheme (ECIS based on the analysis of the current schemes. Detailed design of each functional component in the new scheme is proposed, and an expansion of the SSCS module in NS2 802.15.4 simulator is examined. Comprehensive experiments on the simulation platform show that the newly proposed scheme is advantageous over existing results.

  16. Finite difference weighted essentially non-oscillatory schemes with constrained transport for ideal magnetohydrodynamics

    Science.gov (United States)

    Christlieb, Andrew J.; Rossmanith, James A.; Tang, Qi

    2014-07-01

    In this work we develop a class of high-order finite difference weighted essentially non-oscillatory (FD-WENO) schemes for solving the ideal magnetohydrodynamic (MHD) equations in 2D and 3D. The philosophy of this work is to use efficient high-order WENO spatial discretizations with high-order strong stability-preserving Runge-Kutta (SSP-RK) time-stepping schemes. Numerical results have shown that with such methods we are able to resolve solution structures that are only visible at much higher grid resolutions with lower-order schemes. The key challenge in applying such methods to ideal MHD is to control divergence errors in the magnetic field. We achieve this by augmenting the base scheme with a novel high-order constrained transport approach that updates the magnetic vector potential. The predicted magnetic field from the base scheme is replaced by a divergence-free magnetic field that is obtained from the curl of this magnetic potential. The non-conservative weakly hyperbolic system that the magnetic vector potential satisfies is solved using a version of FD-WENO developed for Hamilton-Jacobi equations. The resulting numerical method is endowed with several important properties: (1) all quantities, including all components of the magnetic field and magnetic potential, are treated as point values on the same mesh (i.e., there is no mesh staggering); (2) both the spatial and temporal orders of accuracy are fourth-order; (3) no spatial integration or multidimensional reconstructions are needed in any step; and (4) special limiters in the magnetic vector potential update are used to control unphysical oscillations in the magnetic field. Several 2D and 3D numerical examples are presented to verify the order of accuracy on smooth test problems and to show high-resolution on test problems that involve shocks.

  17. A SECOND ORDER DIFFERENCE SCHEME WITH NONUNIFORM MESHES FOR NONLINEAR PARABOLIC SYSTEM

    Institute of Scientific and Technical Information of China (English)

    WAN Zhengsu; CHEN Guangnan

    2003-01-01

    In this paper, a difference scheme with nonuniform meshes is established for the initial-boundary problem of the nonlinear parabolic system. It is proved that the difference scheme is second order convergent in spacestep and timestep.

  18. Conservative high-order-accurate finite-difference methods for curvilinear grids

    Science.gov (United States)

    Rai, Man M.; Chakrvarthy, Sukumar

    1993-01-01

    Two fourth-order-accurate finite-difference methods for numerically solving hyperbolic systems of conservation equations on smooth curvilinear grids are presented. The first method uses the differential form of the conservation equations; the second method uses the integral form of the conservation equations. Modifications to these schemes, which are required near boundaries to maintain overall high-order accuracy, are discussed. An analysis that demonstrates the stability of the modified schemes is also provided. Modifications to one of the schemes to make it total variation diminishing (TVD) are also discussed. Results that demonstrate the high-order accuracy of both schemes are included in the paper. In particular, a Ringleb-flow computation demonstrates the high-order accuracy and the stability of the boundary and near-boundary procedures. A second computation of supersonic flow over a cylinder demonstrates the shock-capturing capability of the TVD methodology. An important contribution of this paper is the dear demonstration that higher order accuracy leads to increased computational efficiency.

  19. An energy and potential enstrophy conserving numerical scheme for the multi-layer shallow water equations with complete Coriolis force

    Science.gov (United States)

    Stewart, Andrew L.; Dellar, Paul J.

    2016-05-01

    We present an energy- and potential enstrophy-conserving scheme for the non-traditional shallow water equations that include the complete Coriolis force and topography. These integral conservation properties follow from material conservation of potential vorticity in the continuous shallow water equations. The latter property cannot be preserved by a discretisation on a fixed Eulerian grid, but exact conservation of a discrete energy and a discrete potential enstrophy seems to be an effective substitute that prevents any distortion of the forward and inverse cascades in quasi-two dimensional turbulence through spurious sources and sinks of energy and potential enstrophy, and also increases the robustness of the scheme against nonlinear instabilities. We exploit the existing Arakawa-Lamb scheme for the traditional shallow water equations, reformulated by Salmon as a discretisation of the Hamiltonian and Poisson bracket for this system. The non-rotating, traditional, and our non-traditional shallow water equations all share the same continuous Hamiltonian structure and Poisson bracket, provided one distinguishes between the particle velocity and the canonical momentum per unit mass. We have determined a suitable discretisation of the non-traditional canonical momentum, which includes additional coupling between the layer thickness and velocity fields, and modified the discrete kinetic energy to suppress an internal symmetric computational instability that otherwise arises for multiple layers. The resulting scheme exhibits the expected second-order convergence under spatial grid refinement. We also show that the drifts in the discrete total energy and potential enstrophy due to temporal truncation error may be reduced to machine precision under suitable refinement of the timestep using the third-order Adams-Bashforth or fourth-order Runge-Kutta integration schemes.

  20. Generalized Subtraction Schemes for the Difference Formulation in Radiation Transport

    Energy Technology Data Exchange (ETDEWEB)

    Luu, T; Brooks, E; Szoke, A

    2008-07-25

    In the difference formulation for the transport of thermally emitted photons, the photon intensity is defined relative to a reference field, the black body at the local material temperature. This choice of reference field removes the cancellation between thermal emission and absorption that is responsible for noise in the Monte Carlo solution of thick systems, but introduces time and space derivative source terms that can not be determined until the end of the time step. It can also lead to noise induced crashes under certain conditions where the real physical photon intensity differs strongly from a black body at the local material temperature. In this report, we consider a difference formulation relative to the material temperature at the beginning of the time step, and in the situations where the radiation intensity more closely follows a temperature other than the local material temperature, that temperature. The result is a method where iterative solution of the material energy equation is efficient and noise induced crashes are avoided. To support our contention that the resulting generalized subtraction scheme is robust, and therefore suitable for practical use, we perform a stability analysis in the thick limit where instabilities usually occur.

  1. A Modified Equation Approach to Selecting a Nonstandard Finite Difference Scheme Applied to the Regularized Long Wave Equation

    Directory of Open Access Journals (Sweden)

    E. Momoniat

    2014-01-01

    Full Text Available Two nonstandard finite difference schemes are derived to solve the regularized long wave equation. The criteria for choosing the “best” nonstandard approximation to the nonlinear term in the regularized long wave equation come from considering the modified equation. The two “best” nonstandard numerical schemes are shown to preserve conserved quantities when compared to an implicit scheme in which the nonlinear term is approximated in the usual way. Comparisons to the single solitary wave solution show significantly better results, measured in the L2 and L∞ norms, when compared to results obtained using a Petrov-Galerkin finite element method and a splitted quadratic B-spline collocation method. The growth in the error when simulating the single solitary wave solution using the two “best” nonstandard numerical schemes is shown to be linear implying the nonstandard finite difference schemes are conservative. The formation of an undular bore for both steep and shallow initial profiles is captured without the formation of numerical instabilities.

  2. Noether conserved quantities and Lie point symmetries of difference Lagrange-Maxwell equations and lattices

    Institute of Scientific and Technical Information of China (English)

    Fu Jing-Li; Nie Ning-Ming; Huang Jian-Fei; Jiménez Salvador; Tang Yi-Fa; Vázquez Luis; Zhao Wei-Jia

    2009-01-01

    This paper presents a method to find Noether-type conserved quantities and Lie point symmetries for discrete mechanico-electrical dynamical systems, which leave invariant the set of solutions of the corresponding difference scheme.This approach makes it possible to devise techniques for solving the Lagrange-Maxwell equations in differences which correspond to mechanico-electrical systems, by adapting existing differential equations. In particular, it obtains a new systematic method to determine both the one-parameter Lie groups and the discrete Noether conserved quantities of Lie point symmetries for mechanico-electrical systems. As an application, it obtains the Lie point symmetries and the conserved quantities for the difference equation of a model that represents a capacitor microphone.

  3. CABARET scheme with conservation-flux asynchronous time-stepping for nonlinear aeroacoustics problems

    Science.gov (United States)

    Semiletov, V. A.; Karabasov, S. A.

    2013-11-01

    Explicit time stepping renders many high-resolution computational schemes to become less efficient when dealing with non-uniform grids typical of many aeroacoustic applications. Asynchronous time stepping, i.e., updating the solution in different cell sizes according to their local rates, is known to be a promising way to improve the efficiency of explicit time-stepping methods without compromise in accuracy. In the present paper, a new asynchronous time-stepping algorithm is developed for the Compact Accurately Boundary-Adjusting high-REsolution Technique (CABARET) Euler method. This allows to significantly speedup the original single-step CABARET method with non-uniform grids and improves its accuracy at the same time. Numerical examples are provided and issues associated with the method performance on various grid resolutions are discussed.

  4. Comparing Sediment Yield Predictions from Different Hydrologic Modeling Schemes

    Science.gov (United States)

    Dahl, T. A.; Kendall, A. D.; Hyndman, D. W.

    2015-12-01

    Sediment yield, or the delivery of sediment from the landscape to a river, is a difficult process to accurately model. It is primarily a function of hydrology and climate, but influenced by landcover and the underlying soils. These additional factors make it much more difficult to accurately model than water flow alone. It is not intuitive what impact different hydrologic modeling schemes may have on the prediction of sediment yield. Here, two implementations of the Modified Universal Soil Loss Equation (MUSLE) are compared to examine the effects of hydrologic model choice. Both the Soil and Water Assessment Tool (SWAT) and the Landscape Hydrology Model (LHM) utilize the MUSLE for calculating sediment yield. SWAT is a lumped parameter hydrologic model developed by the USDA, which is commonly used for predicting sediment yield. LHM is a fully distributed hydrologic model developed primarily for integrated surface and groundwater studies at the watershed to regional scale. SWAT and LHM models were developed and tested for two large, adjacent watersheds in the Great Lakes region; the Maumee River and the St. Joseph River. The models were run using a variety of single model and ensemble downscaled climate change scenarios from the Coupled Model Intercomparison Project 5 (CMIP5). The initial results of this comparison are discussed here.

  5. Mapping of the Universe of Knowledge in Different Classification Schemes

    Directory of Open Access Journals (Sweden)

    M. P. Satija

    2017-06-01

    Full Text Available Given the variety of approaches to mapping the universe of knowledge that have been presented and discussed in the literature, the purpose of this paper is to systematize their main principles and their applications in the major general modern library classification schemes. We conducted an analysis of the literature on classification and the main classification systems, namely Dewey/Universal Decimal Classification, Cutter’s Expansive Classification, Subject Classification of J.D. Brown, Colon Classification, Library of Congress Classification, Bibliographic Classification, Rider’s International Classification, Bibliothecal Bibliographic Klassification (BBK, and Broad System of Ordering (BSO. We conclude that the arrangement of the main classes can be done following four principles that are not mutually exclusive: ideological principle, social purpose principle, scientific order, and division by discipline. The paper provides examples and analysis of each system. We also conclude that as knowledge is ever-changing, classifications also change and present a different structure of knowledge depending upon the society and time of their design.

  6. An energy conserving finite-difference model of Maxwell's equations for soliton propagation

    CERN Document Server

    Bachiri, H; Vázquez, L

    1997-01-01

    We present an energy conserving leap-frog finite-difference scheme for the nonlinear Maxwell's equations investigated by Hile and Kath [C.V.Hile and W.L.Kath, J.Opt.Soc.Am.B13, 1135 (96)]. The model describes one-dimensional scalar optical soliton propagation in polarization preserving nonlinear dispersive media. The existence of a discrete analog of the underlying continuous energy conservation law plays a central role in the global accuracy of the scheme and a proof of its generalized nonlinear stability using energy methods is given. Numerical simulations of initial fundamental, second and third-order hyperbolic secant soliton pulses of fixed spatial full width at half peak intensity containing as few as 4 and 8 optical carrier wavelengths, confirm the stability, accuracy and efficiency of the algorithm. The effect of a retarded nonlinear response time of the media modeling Raman scattering is under current investigation in this context.

  7. A TVD-WAF-based hybrid finite volume and finite difference scheme for nonlinearly dispersive wave equations

    Directory of Open Access Journals (Sweden)

    Jing Yin

    2015-07-01

    Full Text Available A total variation diminishing-weighted average flux (TVD-WAF-based hybrid numerical scheme for the enhanced version of nonlinearly dispersive Boussinesq-type equations was developed. The one-dimensional governing equations were rewritten in the conservative form and then discretized on a uniform grid. The finite volume method was used to discretize the flux term while the remaining terms were approximated with the finite difference method. The second-order TVD-WAF method was employed in conjunction with the Harten-Lax-van Leer (HLL Riemann solver to calculate the numerical flux, and the variables at the cell interface for the local Riemann problem were reconstructed via the fourth-order monotone upstream-centered scheme for conservation laws (MUSCL. The time marching scheme based on the third-order TVD Runge-Kutta method was used to obtain numerical solutions. The model was validated through a series of numerical tests, in which wave breaking and a moving shoreline were treated. The good agreement between the computed results, documented analytical solutions, and experimental data demonstrates the correct discretization of the governing equations and high accuracy of the proposed scheme, and also conforms the advantages of the proposed shock-capturing scheme for the enhanced version of the Boussinesq model, including the convenience in the treatment of wave breaking and moving shorelines and without the need for a numerical filter.

  8. How effective are European agri-environment schemes in conserving and promoting biodiversity?

    NARCIS (Netherlands)

    Kleijn, D.; Sutherland, W.J.

    2003-01-01

    1. Increasing concern over the environmental impact of agriculture in Europe has led to the introduction of agri-environment schemes. These schemes compensate farmers financially for any loss of income associated with measures that aim to benefit the environment or biodiversity. There are currently

  9. High order sub-cell finite volume schemes for solving hyperbolic conservation laws I: basic formulation and one-dimensional analysis

    Science.gov (United States)

    Pan, JianHua; Ren, YuXin

    2017-08-01

    In this paper, a family of sub-cell finite volume schemes for solving the hyperbolic conservation laws is proposed and analyzed in one-dimensional cases. The basic idea of this method is to subdivide a control volume (main cell) into several sub-cells and the finite volume discretization is applied to each of the sub-cells. The averaged values on the sub-cells of current and face neighboring main cells are used to reconstruct the polynomial distributions of the dependent variables. This method can achieve arbitrarily high order of accuracy using a compact stencil. It is similar to the spectral volume method incorporating with PNPM technique but with fundamental differences. An elaborate utilization of these differences overcomes some shortcomings of the spectral volume method and results in a family of accurate and robust schemes for solving the hyperbolic conservation laws. In this paper, the basic formulation of the proposed method is presented. The Fourier analysis is performed to study the properties of the one-dimensional schemes. A WENO limiter based on the secondary reconstruction is constructed.

  10. Stability-Controllable Second-Order Difference Scheme for Convection Term

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    A new finite difference scheme-SCSD scheme has been propsed based on CD( Central Difference) scheme and SUD(Second-order Upwind Difference)scheme.Its basic feature is controllable convective stability and always second-order accuracy(Stability-Controllable Second-order Difference),It has been proven that this Scheme is convective-Stable if the grid Peclet number|PΔ|≤2/β(0≤β≤1).The advantage of this new scheme has been discussed based on the modified wavenumber analysis by using Fourier transform.This scheme has been applied to the 2-D incompressible convective-diffusive equation and 2-D compressible Euler equation,and corresponding finite difference equations have been derived.Numerical examples of 1-D Burgers equation and 2-D transport equation have been presented to show its good accuracy and controllable convective stability.

  11. Overlapping Domain Decomp osition Finite Difference Algorithm for Compact Difference Scheme of the Heat Conduction Equation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hong-mei

    2015-01-01

    In this paper, a modified additive Schwarz finite difference algorithm is applied in the heat conduction equation of the compact difference scheme. The algorithm is on the basis of domain decomposition and the subspace correction. The basic train of thought is the introduction of the units function decomposition and reasonable distribution of the overlap of correction. The residual correction is conducted on each subspace while the computation is completely parallel. The theoretical analysis shows that this method is completely characterized by parallel.

  12. A smart nonstandard finite difference scheme for second order nonlinear boundary value problems

    NARCIS (Netherlands)

    Erdogan, Utku; Ozis, Turgut

    2011-01-01

    A new kind of finite difference scheme is presented for special second order nonlinear two point boundary value problems. An artificial parameter is introduced in the scheme. Symbolic computation is proposed for the construction of the scheme. Local truncation error of the method is discussed. Numer

  13. A smart nonstandard finite difference scheme for second order nonlinear boundary value problems

    NARCIS (Netherlands)

    Erdogan, Utku; Ozis, Turgut

    2011-01-01

    A new kind of finite difference scheme is presented for special second order nonlinear two point boundary value problems. An artificial parameter is introduced in the scheme. Symbolic computation is proposed for the construction of the scheme. Local truncation error of the method is discussed.

  14. Algorithm composition scheme for problems in composite domains based on the difference potential method

    Science.gov (United States)

    Ryaben'kii, V. S.; Turchaninov, V. I.; Epshteyn, Ye. Yu.

    2006-10-01

    An algorithm composition scheme for the numerical solution of boundary value problems in composite domains is proposed and illustrated using an example. The scheme requires neither difference approximations of the boundary conditions nor matching conditions on the boundary between the subdomains. The scheme is suited for multiprocessor computers.

  15. Crank-Nicholson difference scheme for a stochastic parabolic equation with a dependent operator coefficient

    Science.gov (United States)

    Ashyralyev, Allaberen; Okur, Ulker

    2016-08-01

    In the present paper, the Crank-Nicolson difference scheme for the numerical solution of the stochastic parabolic equation with the dependent operator coefficient is considered. Theorem on convergence estimates for the solution of this difference scheme is established. In applications, convergence estimates for the solution of difference schemes for the numerical solution of three mixed problems for parabolic equations are obtained. The numerical results are given.

  16. Solving moving interface problems using a higher order accurate finite difference scheme

    Science.gov (United States)

    Mittal, H. V. R.; Ray, Rajendra K.

    2017-07-01

    A new finite difference scheme is applied to solve partial differential equations in domains with discontinuities due to the presence of time dependent moving or deforming interfaces. This scheme is an extension of the finite difference idea developed for solving incompressible, steady stokes equations in discontinuous domains with fixed interfaces [1]. This new idea is applied at the irregular points at each time step in conjunction with the Crank-Nicolson (CN) implicit scheme and a recently developed Higher Order Compact (HOC) scheme at regular points. For validation, Stefan's problem is considered with a moving interface in one dimension. In two dimensions, heat equation is considered on a square domain with a circular interface whose radius is continuously changing with time. HOC scheme is found to produce better results and the order of accuracy is slightly better than that of the CN scheme. However, both the schemes show around second order accuracy and good agreement with the analytical solution.

  17. Comparison Experiments of Different Model Error Schemes in Ensemble Kalman Filter Soil Moisture Assimilation

    Science.gov (United States)

    Nie, Suping; Zhu, Jiang; Luo, Yong

    2010-05-01

    The purpose of this study is to explore the performances of different model error scheme in soil moisture data assimilation. Based on the ensemble Kalman filter (EnKF) and the atmosphere-vegetation interaction model (AVIM), point-scale analysis results for three schemes, 1) covariance inflation (CI), 2) direct random disturbance (DRD), and 3) error source random disturbance (ESRD), are combined under conditions of different observational error estimations, different observation layers, and different observation intervals using a series of idealized experiments. The results shows that all these schemes obtain good assimilation results when the assumed observational error is an accurate statistical representation of the actual error used to perturb the original truth value, and the ESRD scheme has the least root mean square error (RMSE). Overestimation or underestimation of the observational errors can affect the assimilation results of CI and DRD schemes sensitively. The performances of these two schemes deteriorate obviously while the ESRD scheme keeps its capability well. When the observation layers or observation interval increase, the performances of both CI and DRD schemes decline evidently. But for the ESRD scheme, as it can assimilate multi-layer observations coordinately, the increased observations improve the assimilation results further. Moreover, as the ESRD scheme contains a certain amount of model error estimation functions in its assimilation process, it also has a good performance in assimilating sparse-time observations.

  18. A Comparison of Boundary-Layer Characteristics Simulated Using Different Parametrization Schemes

    Science.gov (United States)

    Wang, Weiguo; Shen, Xinyong; Huang, Wenyan

    2016-06-01

    We compare daytime planetary boundary-layer (PBL) characteristics under fair-weather conditions simulated using a single column version of the Weather Research and Forecasting model with different PBL parametrization schemes. The model is driven only by prescribed surface heat fluxes and horizontal pressure gradient forcing. Parametrizations for all physical processes except for turbulence and transport in the PBL are turned off in the simulations to ensure the discrepancies in the simulated PBL flow are due only to differences in the PBL schemes. A large-eddy simulation (LES) of the evolution of a daytime PBL is performed as a benchmark to examine how well a PBL parametrization scheme reproduces the LES results, and performance statistics are compared to rank those schemes. In general, hybrid local and non-local schemes such as the Yonsei University and Asymmetrical Convective Model (version 2) schemes perform better in reproducing the LES results, particularly well-mixed features, than do local schemes. Among local schemes, the University of Washington scheme produces the results closest to the LES. Local schemes, such as those of Mellor-Yamada-Janjic and Mellor-Yamada-Nakanishi-Niino, simulate too low an entrainment flux, while PBL heights diagnosed from the simulations using local schemes are lower than those from the LES results. Hybrid local and non-local schemes are more sensitive to vertical grid resolution than local schemes. With a higher vertical resolution in the PBL, the schemes using the eddy-diffusivity and mass-flux methods perform better. Differences in the values of eddy diffusivity, length scale, and turbulence kinetic energy and their vertical distributions are large.

  19. A Comparison of Boundary-Layer Characteristics Simulated Using Different Parametrization Schemes

    Science.gov (United States)

    Wang, Weiguo; Shen, Xinyong; Huang, Wenyan

    2016-11-01

    We compare daytime planetary boundary-layer (PBL) characteristics under fair-weather conditions simulated using a single column version of the Weather Research and Forecasting model with different PBL parametrization schemes. The model is driven only by prescribed surface heat fluxes and horizontal pressure gradient forcing. Parametrizations for all physical processes except for turbulence and transport in the PBL are turned off in the simulations to ensure the discrepancies in the simulated PBL flow are due only to differences in the PBL schemes. A large-eddy simulation (LES) of the evolution of a daytime PBL is performed as a benchmark to examine how well a PBL parametrization scheme reproduces the LES results, and performance statistics are compared to rank those schemes. In general, hybrid local and non-local schemes such as the Yonsei University and Asymmetrical Convective Model (version 2) schemes perform better in reproducing the LES results, particularly well-mixed features, than do local schemes. Among local schemes, the University of Washington scheme produces the results closest to the LES. Local schemes, such as those of Mellor-Yamada-Janjic and Mellor-Yamada-Nakanishi-Niino, simulate too low an entrainment flux, while PBL heights diagnosed from the simulations using local schemes are lower than those from the LES results. Hybrid local and non-local schemes are more sensitive to vertical grid resolution than local schemes. With a higher vertical resolution in the PBL, the schemes using the eddy-diffusivity and mass-flux methods perform better. Differences in the values of eddy diffusivity, length scale, and turbulence kinetic energy and their vertical distributions are large.

  20. Comparison of different incremental analysis update schemes in a realistic assimilation system with Ensemble Kalman Filter

    Science.gov (United States)

    Yan, Y.; Barth, A.; Beckers, J. M.; Brankart, J. M.; Brasseur, P.; Candille, G.

    2017-07-01

    In this paper, three incremental analysis update schemes (IAU 0, IAU 50 and IAU 100) are compared in the same assimilation experiments with a realistic eddy permitting primitive equation model of the North Atlantic Ocean using the Ensemble Kalman Filter. The difference between the three IAU schemes lies on the position of the increment update window. The relevance of each IAU scheme is evaluated through analyses on both thermohaline and dynamical variables. The validation of the assimilation results is performed according to both deterministic and probabilistic metrics against different sources of observations. For deterministic validation, the ensemble mean and the ensemble spread are compared to the observations. For probabilistic validation, the continuous ranked probability score (CRPS) is used to evaluate the ensemble forecast system according to reliability and resolution. The reliability is further decomposed into bias and dispersion by the reduced centred random variable (RCRV) score. The obtained results show that 1) the IAU 50 scheme has the same performance as the IAU 100 scheme 2) the IAU 50/100 schemes outperform the IAU 0 scheme in error covariance propagation for thermohaline variables in relatively stable region, while the IAU 0 scheme outperforms the IAU 50/100 schemes in dynamical variables estimation in dynamically active region 3) in case with sufficient number of observations and good error specification, the impact of IAU schemes is negligible. The differences between the IAU 0 scheme and the IAU 50/100 schemes are mainly due to different model integration time and different instability (density inversion, large vertical velocity, etc.) induced by the increment update. The longer model integration time with the IAU 50/100 schemes, especially the free model integration, on one hand, allows for better re-establishment of the equilibrium model state, on the other hand, smooths the strong gradients in dynamically active region.

  1. A sixth order hybrid finite difference scheme based on the minimized dispersion and controllable dissipation technique

    Science.gov (United States)

    Sun, Zhen-sheng; Luo, Lei; Ren, Yu-xin; Zhang, Shi-ying

    2014-08-01

    The dispersion and dissipation properties of a scheme are of great importance for the simulation of flow fields which involve a broad range of length scales. In order to improve the spectral properties of the finite difference scheme, the authors have previously proposed the idea of optimizing the dispersion and dissipation properties separately and a fourth order scheme based on the minimized dispersion and controllable dissipation (MDCD) technique is thus constructed [29]. In the present paper, we further investigate this technique and extend it to a sixth order finite difference scheme to solve the Euler and Navier-Stokes equations. The dispersion properties of the scheme is firstly optimized by minimizing an elaborately designed integrated error function. Then the dispersion-dissipation condition which is newly derived by Hu and Adams [30] is introduced to supply sufficient dissipation to damp the unresolved wavenumbers. Furthermore, the optimized scheme is blended with an optimized Weighted Essentially Non-Oscillation (WENO) scheme to make it possible for the discontinuity-capturing. In this process, the approximation-dispersion-relation (ADR) approach is employed to optimize the spectral properties of the nonlinear scheme to yield the true wave propagation behavior of the finite difference scheme. Several benchmark test problems, which include broadband fluctuations and strong shock waves, are solved to validate the high-resolution, the good discontinuity-capturing capability and the high-efficiency of the proposed scheme.

  2. Valuing investments in sustainable land management using an integrated modelling framework to support a watershed conservation scheme in the Upper Tana River, Kenya

    Science.gov (United States)

    Hunink, Johannes E.; Bryant, Benjamin P.; Vogl, Adrian; Droogers, Peter

    2015-04-01

    We analyse the multiple impacts of investments in sustainable land use practices on ecosystem services in the Upper Tana basin (Kenya) to support a watershed conservation scheme (a "water fund"). We apply an integrated modelling framework, building on previous field-based and modelling studies in the basin, and link biophysical outputs to economic benefits for the main actors in the basin. The first step in the modelling workflow is the use of a high-resolution spatial prioritization tool (Resource Investment Optimization System -- RIOS) to allocate the type and location of conservation investments in the different subbasins, subject to budget constraints and stakeholder concerns. We then run the Soil and Water Assessment Tool (SWAT) using the RIOS-identified investment scenarios to produce spatially explicit scenarios that simulate changes in water yield and suspended sediment. Finally, in close collaboration with downstream water users (urban water supply and hydropower) we link those biophysical outputs to monetary metrics, including: reduced water treatment costs, increased hydropower production, and crop yield benefits for upstream farmers in the conservation area. We explore how different budgets and different spatial targeting scenarios influence the return of the investments and the effectiveness of the water fund scheme. This study is novel in that it presents an integrated analysis targeting interventions in a decision context that takes into account local environmental and socio-economic conditions, and then relies on detailed, process-based, biophysical models to demonstrate the economic return on those investments. We conclude that the approach allows for an analysis on different spatial and temporal scales, providing conclusive evidence to stakeholders and decision makers on the contribution and benefits of the land-based investments in this basin. This is serving as foundational work to support the implementation of the Upper Tana-Nairobi Water Fund

  3. On Third Order Stable Difference Scheme for Hyperbolic Multipoint Nonlocal Boundary Value Problem

    Directory of Open Access Journals (Sweden)

    Ozgur Yildirim

    2015-01-01

    Full Text Available This paper presents a third order of accuracy stable difference scheme for the approximate solution of multipoint nonlocal boundary value problem of the hyperbolic type in a Hilbert space with self-adjoint positive definite operator. Stability estimates for solution of the difference scheme are obtained. Some results of numerical experiments that support theoretical statements are presented.

  4. Stability of Difference Schemes for Fractional Parabolic PDE with the Dirichlet-Neumann Conditions

    Directory of Open Access Journals (Sweden)

    Zafer Cakir

    2012-01-01

    boundary conditions are presented. Stability estimates and almost coercive stability estimates with ln (1/(+|ℎ| for the solution of these difference schemes are obtained. A procedure of modified Gauss elimination method is used for solving these difference schemes of one-dimensional fractional parabolic partial differential equations.

  5. THE UNCONDITIONAL STABILITY OF PARALLEL DIFFERENCE SCHEMES WITH SECOND ORDER CONVERGENCE FOR NONLINEAR PARABOLIC SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Yuan Guangwei; Sheng Zhiqiang; Hang Xudeng

    2007-01-01

    For solving nonlinear parabolic equation on massive parallel computers,the construction of parallel difference schemes with simple design, high parallelism and unconditional stability and second order global accuracy in space, has long been desired.In the present work, a new kind of general parallel difference schemes for the nonlinear parabolic system is proposed. The general parallel difference schemes include, among others, two new parallel schemes. In one of them, to obtain the interface values on the interface of sub-domains an explicit scheme of Jacobian type is employed, and then the fully implicit scheme is used in the sub-domains. Here, in the explicit scheme of Jacobian type, the values at the points being adjacent to the interface points are taken as the linear combination of values of previous two time layers at the adjoining points of the inner interface. For the construction of another new parallel difference scheme,the main procedure is as follows. Firstly the linear combination of values of previous two time layers at the interface points among the sub-domains is used as the (Dirichlet)boundary condition for solving the sub-domain problems. Then the values in the subdomains are calculated by the fully implicit scheme. Finally the interface values are computed by the fully implicit scheme, and in fact these calculations of the last step are explicit since the values adjacent to the interface points have been obtained in the previous step. The existence, uniqueness, unconditional stability and the second order accuracy of the discrete vector solutions for the parallel difference schemes are proved.Numerical results are presented to examine the stability, accuracy and parallelism of the parallel schemes.

  6. Assessment on Different Schemes of Industrial Structure Adjustment Based on DEA

    Institute of Scientific and Technical Information of China (English)

    FU Li-fang; MENG Jun

    2004-01-01

    DEA is a new research field in operations research. It has unique virtues in dealing with assessment problem with multi-inputs especially multi-outputs, In this paper, DEA model of Dεc2R has been applied to evaluate the relative efficiency of several different schemes of industrial structure adjustment of agriculture and finally select the optimal scheme. Furthermore, the inferior scheme has been improved according to some useful insights got from DEA model.

  7. Optimal error estimates and energy conservation identities of the ADI-FDTD scheme on staggered grids for 3D Maxwell's equations

    CERN Document Server

    Gao, Liping

    2011-01-01

    This paper is concerned with the optimal error estimates and energy conservation properties of the alternating direction implicit finite-difference time-domain (ADI-FDTD) method which is a popular scheme for solving the 3D Maxwell equations. Precisely, for the case with a perfectly electric conducting (PEC) boundary condition we establish the optimal second-order error estimates in both space and time in the discrete $H^1$-norm for the ADI-FDTD scheme and prove the approximate divergence preserving property that if the divergence of the initial electric and magnetic fields are zero then the discrete $L^2$-norm of the discrete divergence of the ADI-FDTD solution is approximately zero with the second-order accuracy in both space and time. A key ingredient is two new discrete energy norms which are second-order in time perturbations of two new energy conservation laws for the Maxwell equations introduced in this paper. Furthermore, we prove that, in addition to two known discrete energy identities which are seco...

  8. A Survey on Different Approaches for Energy Conservation in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Rumpa Mukherjee,Arindom Mukherjee

    2013-03-01

    Full Text Available In the recent years the applications of wirelesssensor networksin the fields such as scientific,militaryandhealthcarehave developed. So it hasgained more attention inresearch area. A sensornode is basically a battery powered device and theuse of battery has become a constraints.The mainmotive is to reducetheenergy consumption ofsensor node to increase the network lifetime. In thispaper,wehavediscussedaboutthe energyconsumption of a particular sensor node ofWSNs.Thenwehaverepresentedvarious systematic andcomprehensive schemes of energy conservation,which are subsequently discussed in depth. Specialattention has been giventothe literature survey anddevotion of promising solutions faced in eachtechnique.Wehave provided some solutions thatare being faced in each technique. In the final partwe will look into the different directions forresearch about energy conservation of wirelesssensor networks

  9. Optimized explicit Runge-Kutta schemes for the spectral difference method applied to wave propagation problems

    CERN Document Server

    Parsani, M; Deconinck, W

    2012-01-01

    Explicit Runge-Kutta schemes with large stable step sizes are developed for integration of high order spectral difference spatial discretization on quadrilateral grids. The new schemes permit an effective time step that is substantially larger than the maximum admissible time step of standard explicit Runge-Kutta schemes available in literature. Furthermore, they have a small principal error norm and admit a low-storage implementation. The advantages of the new schemes are demonstrated through application to the Euler equations and the linearized Euler equations.

  10. Optimized Explicit Runge--Kutta Schemes for the Spectral Difference Method Applied to Wave Propagation Problems

    KAUST Repository

    Parsani, Matteo

    2013-04-10

    Explicit Runge--Kutta schemes with large stable step sizes are developed for integration of high-order spectral difference spatial discretizations on quadrilateral grids. The new schemes permit an effective time step that is substantially larger than the maximum admissible time step of standard explicit Runge--Kutta schemes available in the literature. Furthermore, they have a small principal error norm and admit a low-storage implementation. The advantages of the new schemes are demonstrated through application to the Euler equations and the linearized Euler equations.

  11. On stability of difference schemes for hyperbolic multipoint NBVP with Neumann conditions

    Science.gov (United States)

    Yildirim, Ozgur; Uzun, Meltem

    2016-08-01

    In this work, a multipoint nonlocal boundary value problem (NBVP) for hyperbolic equations with Neumann conditions is considered. Third and fourth order of accuracy stable difference schemes for solving this problem are presented. Efficiency of these schemes are tested via MATLAB implementation.

  12. Optimal convergence rate of the explicit finite difference scheme for American option valuation

    Science.gov (United States)

    Hu, Bei; Liang, Jin; Jiang, Lishang

    2009-08-01

    An optimal convergence rate O([Delta]x) for an explicit finite difference scheme for a variational inequality problem is obtained under the stability condition using completely PDE methods. As a corollary, a binomial tree scheme of an American put option (where ) is convergent unconditionally with the rate O(([Delta]t)1/2).

  13. [Farmacoeconomical estimation of efficiency of different schemes of eradication therapy of Helicobacter pylori infection in children].

    Science.gov (United States)

    Kashnikova, S N; Shcherbakov, P L; Kashnikov, V V; Tatarinov, P A; Shcherbakova, M Iu

    2008-01-01

    In this article farmakoekonomical analysis of efficiency of various, the most common in Russia schemes of eradication therapy disoders, associated with H. pylori infection is given to by authors basis on their private experience. All-round studying of the different economical factors influencing on a cost of used schemes is realized, and result of spent complex efficiency eradication therapy is estimated.

  14. SHALLOW WATER EQUATION SOLUTION IN 2D USING FINITE DIFFERENCE METHOD WITH EXPLICIT SCHEME

    Directory of Open Access Journals (Sweden)

    Nuraini Nuraini

    2017-09-01

    Full Text Available Abstract. Modeling the dynamics of seawater typically uses a shallow water model. The shallow water model is derived from the mass conservation equation and the momentum set into shallow water equations. A two-dimensional shallow water equation alongside the model that is integrated with depth is described in numerical form. This equation can be solved by finite different methods either explicitly or implicitly. In this modeling, the two dimensional shallow water equations are described in discrete form using explicit schemes. Keyword: shallow water equation, finite difference and schema explisit. REFERENSI  1. Bunya, S., Westerink, J. J. dan Yoshimura. 2005. Discontinuous Boundary Implementation for the Shallow Water Equations. Int. J. Numer. Meth. Fluids. 47: 1451-1468. 2. Kampf Jochen. 2009. Ocean Modelling For Beginners. Springer Heidelberg Dordrecht. London New York. 3. Rezolla, L 2011. Numerical Methods for the Solution of Partial Diferential Equations. Trieste. International Schoolfor Advanced Studies. 4. Natakussumah, K. D., Kusuma, S. B. M., Darmawan, H., Adityawan, B. M. Dan  Farid, M. 2007. Pemodelan Hubungan Hujan dan Aliran Permukaan pada Suatu DAS  dengan Metode Beda Hingga. ITB Sain dan Tek. 39: 97-123. 5. Casulli, V. dan Walters, A. R. 2000. An unstructured grid, three-dimensional model based on the shallow water equations. Int. J. Numer. Meth. Fluids. 32: 331-348. 6. Triatmodjo, B. 2002. Metode Numerik  Beta Offset. Yogyakarta.

  15. Conservation laws and evolution schemes in geodesic, hydrodynamic, and magnetohydrodynamic flows

    Science.gov (United States)

    Markakis, Charalampos; Uryū, Kōji; Gourgoulhon, Eric; Nicolas, Jean-Philippe; Andersson, Nils; Pouri, Athina; Witzany, Vojtěch

    2017-09-01

    Carter and Lichnerowicz have established that barotropic fluid flows are conformally geodesic and obey Hamilton's principle. This variational approach can accommodate neutral, or charged and poorly conducting, fluids. We show that, unlike what has been previously thought, this approach can also accommodate perfectly conducting magnetofluids, via the Bekenstein-Oron description of ideal magnetohydrodynamics. When Noether symmetries associated with Killing vectors or tensors are present in geodesic flows, they lead to constants of motion polynomial in the momenta. We generalize these concepts to hydrodynamic flows. Moreover, the Hamiltonian descriptions of ideal magnetohydrodynamics allow one to cast the evolution equations into a hyperbolic form useful for evolving rotating or binary compact objects with magnetic fields in numerical general relativity. In this framework, Ertel's potential vorticity theorem for baroclinic fluids arises as a special case of a conservation law valid for any Hamiltonian system. Moreover, conserved circulation laws, such as those of Kelvin, Alfvén and Bekenstein-Oron, emerge simply as special cases of the Poincaré-Cartan integral invariant of Hamiltonian systems. We use this approach to obtain an extension of Kelvin's theorem to baroclinic (nonisentropic) fluids, based on a temperature-dependent time parameter. We further extend this result to perfectly or poorly conducting baroclinic magnetoflows. Finally, in the barotropic case, such magnetoflows are shown to also be geodesic, albeit in a Finsler (rather than Riemann) space.

  16. Extending geometric conservation law to cell-centered finite difference methods on moving and deforming grids

    Science.gov (United States)

    Liao, Fei; Ye, Zhengyin

    2015-12-01

    Despite significant progress in recent computational techniques, the accurate numerical simulations, such as direct-numerical simulation and large-eddy simulation, are still challenging. For accurate calculations, the high-order finite difference method (FDM) is usually adopted with coordinate transformation from body-fitted grid to Cartesian grid. But this transformation might lead to failure in freestream preservation with the geometric conservation law (GCL) violated, particularly in high-order computations. GCL identities, including surface conservation law (SCL) and volume conservation law (VCL), are very important in discretization of high-order FDM. To satisfy GCL, various efforts have been made. An early and successful approach was developed by Thomas and Lombard [6] who used the conservative form of metrics to cancel out metric terms to further satisfy SCL. Visbal and Gaitonde [7] adopted this conservative form of metrics for SCL identities and satisfied VCL identity through invoking VCL equation to acquire the derivative of Jacobian in computation on moving and deforming grids with central compact schemes derived by Lele [5]. Later, using the metric technique from Visbal and Gaitonde [7], Nonomura et al. [8] investigated the freestream and vortex preservation properties of high-order WENO and WCNS on stationary curvilinear grids. A conservative metric method (CMM) was further developed by Deng et al. [9] with stationary grids, and detailed discussion about the innermost difference operator of CMM was shown with proof and corresponding numerical test cases. Noticing that metrics of CMM is asymmetrical without coordinate-invariant property, Deng et al. proposed a symmetrical CMM (SCMM) [12] by using the symmetric forms of metrics derived by Vinokur and Yee [10] to further eliminate asymmetric metric errors with stationary grids considered only. The research from Abe et al. [11] presented new asymmetric and symmetric conservative forms of time metrics and

  17. Conservation performance of different conservation governance regimes in the Peruvian Amazon.

    Science.gov (United States)

    Schleicher, Judith; Peres, Carlos A; Amano, Tatsuya; Llactayo, William; Leader-Williams, Nigel

    2017-09-12

    State-controlled protected areas (PAs) have dominated conservation strategies globally, yet their performance relative to other governance regimes is rarely assessed comprehensively. Furthermore, performance indicators of forest PAs are typically restricted to deforestation, although the extent of forest degradation is greater. We address these shortfalls through an empirical impact evaluation of state PAs, Indigenous Territories (ITs), and civil society and private Conservation Concessions (CCs) on deforestation and degradation throughout the Peruvian Amazon. We integrated remote-sensing data with environmental and socio-economic datasets, and used propensity-score matching to assess: (i) how deforestation and degradation varied across governance regimes between 2006-2011; (ii) their proximate drivers; and (iii) whether state PAs, CCs and ITs avoided deforestation and degradation compared with logging and mining concessions, and the unprotected landscape. CCs, state PAs, and ITs all avoided deforestation and degradation compared to analogous areas in the unprotected landscape. CCs and ITs were on average more effective in this respect than state PAs, showing that local governance can be equally or more effective than centralized state regimes. However, there were no consistent differences between conservation governance regimes when matched to logging and mining concessions. Future impact assessments would therefore benefit from further disentangling governance regimes across unprotected land.

  18. Features and implications of different LHC crossing schemes

    CERN Document Server

    Herr, Werner

    2003-01-01

    To avoid unwanted beam-beam interactions, the two LHC beams cross at an angle in all experimental interaction points. The choice of the crossing plane in the different areas has fundamental consequences on the effects of the long range beam-beam interaction. Recent changes to the hardware, i.e. introduction of a beam screen into the triplet quadrupoles, may limit this choice or reduce the flexibility. The consequences of different crossing scenarios are presented in this report. Other implications such as limitations to the correction possibilities and the flexibility of the crossing geometry are addressed.

  19. Well-posedness of the difference schemes of the high order of accuracy for elliptic equations

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available It is well known the differential equation − u ″ ( t +Au( t =f( t ( −∞difference schemes generated by an exact difference scheme or by Taylor's decomposition on three points for the approximate solutions of this differential equation. The well-posedness of these difference schemes in the difference analogy of the smooth functions is obtained. The exact almost coercive inequality for solutions in C( τ,E of these difference schemes is established.

  20. Parallel difference schemes with interface extrapolation terms for quasi-linear parabolic systems

    Institute of Scientific and Technical Information of China (English)

    Guang-wei YUAN; Xu-deng HANG; Zhi-qiang SHENG

    2007-01-01

    In this paper some new parallel difference schemes with interface extrapolation terms for a quasi-linear parabolic system of equations are constructed. Two types of time extrapolations are proposed to give the interface values on the interface of sub-domains or the values adjacent to the interface points, so that the unconditional stable parallel schemes with the second accuracy are formed.Without assuming heuristically that the original boundary value problem has the unique smooth vector solution, the existence and uniqueness of the discrete vector solutions of the parallel difference schemes constructed are proved. Moreover the unconditional stability of the parallel difference schemes is justified in the sense of the continuous dependence of the discrete vector solution of the schemes on the discrete known data of the original problems in the discrete W2(2,1) (Q△) norms. Finally the convergence of the discrete vector solutions of the parallel difference schemes with interface extrapolation terms to the unique generalized solution of the original quasi-linear parabolic problem is proved. Numerical results are presented to show the good performance of the parallel schemes, including the unconditional stability, the second accuracy and the high parallelism.

  1. Cost-benefit analysis of the energy conservation scheme of a regional public utility; Kosten-Nutzen-Analyse des Energiespar-Programms eines regionalen Energieversorgers

    Energy Technology Data Exchange (ETDEWEB)

    Engel, H. [Energie-Versorgung Schwaben AG, Stuttgart (Germany). Abt. Sondervertragskunden; Karel, A. [Heag Versorgungs-AG, Darmstadt (Germany). Abt. Anwendungsberatung; Setzer, M. [Technische Hochschule Darmstadt (Germany). Inst. fuer Volkswirtschaftslehre

    1996-04-22

    Public utilities increasingly advocate energy conservation, not additional power consumption. With this regard, Heag AG, in its ``energy conservation scheme 2000``, offers a broad range of possibilities. It includes incentives for energy conservation and renewable energy use. As an instrument of analysis for this scheme, cost-benefit analysis was chosen. The authors describe the scheme and test the applicability of cost-benefit analysis. (orig.) [Deutsch] Die EVU setzen sich zunehmend fuer das Energieeinsparen ein, statt fuer zusaetzlichen Stromabsatz. Die Heag Versorgungs-AG bietet dazu ein breit angelegtes Foerderprogramm: `Energiespar-Aktion 2000`. Im Rahmen dieser Aktion werden Massnahmen zur Energieeinsparung und Nutzung regenerativer Energie finanziell gefoerdert. Als Analyseinstrument fuer die Energiespar-Aktion wurde die Kosten-Nutzen-Analyse gewaehlt. Die Verfasser erlaeutern die Energiespar-Aktion und pruefen auch die Anwendbarkeit der Kosten-Nutzen-Analyse. (orig.)

  2. Comparison between different encoding schemes for synthetic aperture imaging

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Jensen, Jørgen Arendt

    2002-01-01

    have solved the first problem by building a scanner capable of acquiring data using STAU in real-time. The SNR is increased by using encoded signals, which make it possible to send more energy in the body, while reserving the spatial and contrast resolution. The performance of temporal, spatial...... and spatio-temporal encoding was investigated. Experiments on wire phantom in water were carried out to quantify the gain from the different encodings. The gain in SNR using an FM modulated pulse is 12 dB. The penetration depth of the images was studied using tissue mimicking phantom with frequency dependent...... influence the performance of the STAU....

  3. Artificial Bee Colony with Different Mutation Schemes: A comparative study

    Directory of Open Access Journals (Sweden)

    Iyad Abu Doush

    2014-03-01

    Full Text Available Artificial Bee Colony (ABC is a swarm-based metaheuristic for continuous optimization. Recent work hybridized this algorithm with other metaheuristics in order to improve performance. The work in this paper, experimentally evaluates the use of different mutation operators with the ABC algorithm. The introduced operator is activated according to a determined probability called mutation rate (MR. The results on standard benchmark function suggest that the use of this operator improves performance in terms of convergence speed and quality of final obtained solution. It shows that Power and Polynomial mutations give best results. The fastest convergence was for the mutation rate value (MR=0.2.

  4. Finite-difference scheme for the numerical solution of the Schroedinger equation

    Science.gov (United States)

    Mickens, Ronald E.; Ramadhani, Issa

    1992-01-01

    A finite-difference scheme for numerical integration of the Schroedinger equation is constructed. Asymptotically (r goes to infinity), the method gives the exact solution correct to terms of order r exp -2.

  5. DIFFERENCE SCHEME AND NUMERICAL SIMULATION BASED ON MIXED FINITE ELEMENT METHOD FOR NATURAL CONVECTION PROBLEM

    Institute of Scientific and Technical Information of China (English)

    罗振东; 朱江; 谢正辉; 张桂芳

    2003-01-01

    The non-stationary natural convection problem is studied. A lowest order finite difference scheme based on mixed finite element method for non-stationary natural convection problem, by the spatial variations discreted with finite element method and time with finite difference scheme was derived, where the numerical solution of velocity, pressure, and temperature can be found together, and a numerical example to simulate the close square cavity is given, which is of practical importance.

  6. A Difference Scheme for Solving the Timoshenko Beam Equations with Tip Body

    Institute of Scientific and Technical Information of China (English)

    Fu-le Li; Zi-ku Wu; Kai-mei Huang

    2008-01-01

    In this article, a Timoehenko beam with tip body and boundary damping is considered. A linearized three-level difference scheme of the Timoshenko beam equations on uniform meshes is derived by the method of reduction of order. The unique solvability, unconditional stability and convergence of the difference scheme are proved. The convergence order in maximum norm is of order two in both space and time. A numerical example is presented to demonstrate the theoretical results.

  7. Energy- and enstrophy-conserving schemes for the shallow-water equations, based on mimetic finite elements

    CERN Document Server

    McRae, Andrew T T

    2013-01-01

    This paper presents a family of spatial discretisations of the nonlinear rotating shallow-water equations that conserve both energy and potential enstrophy. These are based on two-dimensional mixed finite element methods, and hence, unlike some finite difference methods, do not require an orthogonal grid. Numerical verification of the aforementioned properties is also provided.

  8. Intercomparison of Martian Lower Atmosphere Simulated Using Different Planetary Boundary Layer Parameterization Schemes

    Science.gov (United States)

    Natarajan, Murali; Fairlie, T. Duncan; Dwyer Cianciolo, Alicia; Smith, Michael D.

    2015-01-01

    We use the mesoscale modeling capability of Mars Weather Research and Forecasting (MarsWRF) model to study the sensitivity of the simulated Martian lower atmosphere to differences in the parameterization of the planetary boundary layer (PBL). Characterization of the Martian atmosphere and realistic representation of processes such as mixing of tracers like dust depend on how well the model reproduces the evolution of the PBL structure. MarsWRF is based on the NCAR WRF model and it retains some of the PBL schemes available in the earth version. Published studies have examined the performance of different PBL schemes in NCAR WRF with the help of observations. Currently such assessments are not feasible for Martian atmospheric models due to lack of observations. It is of interest though to study the sensitivity of the model to PBL parameterization. Typically, for standard Martian atmospheric simulations, we have used the Medium Range Forecast (MRF) PBL scheme, which considers a correction term to the vertical gradients to incorporate nonlocal effects. For this study, we have also used two other parameterizations, a non-local closure scheme called Yonsei University (YSU) PBL scheme and a turbulent kinetic energy closure scheme called Mellor- Yamada-Janjic (MYJ) PBL scheme. We will present intercomparisons of the near surface temperature profiles, boundary layer heights, and wind obtained from the different simulations. We plan to use available temperature observations from Mini TES instrument onboard the rovers Spirit and Opportunity in evaluating the model results.

  9. Optimized low-order explicit Runge-Kutta schemes for high- order spectral difference method

    KAUST Repository

    Parsani, Matteo

    2012-01-01

    Optimal explicit Runge-Kutta (ERK) schemes with large stable step sizes are developed for method-of-lines discretizations based on the spectral difference (SD) spatial discretization on quadrilateral grids. These methods involve many stages and provide the optimal linearly stable time step for a prescribed SD spectrum and the minimum leading truncation error coefficient, while admitting a low-storage implementation. Using a large number of stages, the new ERK schemes lead to efficiency improvements larger than 60% over standard ERK schemes for 4th- and 5th-order spatial discretization.

  10. Computer difference scheme for a singularly perturbed convection-diffusion equation

    Science.gov (United States)

    Shishkin, G. I.

    2014-08-01

    The Dirichlet problem for a singularly perturbed ordinary differential convection-diffusion equation with a perturbation parameter ɛ (that takes arbitrary values from the half-open interval (0, 1]) is considered. For this problem, an approach to the construction of a numerical method based on a standard difference scheme on uniform meshes is developed in the case when the data of the grid problem include perturbations and additional perturbations are introduced in the course of the computations on a computer. In the absence of perturbations, the standard difference scheme converges at an (δ st ) rate, where δ st = (ɛ + N -1)-1 N -1 and N + 1 is the number of grid nodes; the scheme is not ɛ-uniformly well conditioned or stable to perturbations of the data. Even if the convergence of the standard scheme is theoretically proved, the actual accuracy of the computed solution in the presence of perturbations degrades with decreasing ɛ down to its complete loss for small ɛ (namely, for ɛ = (δ-2max i, j |δ a {/i j }| + δ-1 max i, j |δ b {/i j }|), where δ = δ st and δ a {/i j }, δ b {/i j } are the perturbations in the coefficients multiplying the second and first derivatives). For the boundary value problem, we construct a computer difference scheme, i.e., a computing system that consists of a standard scheme on a uniform mesh in the presence of controlled perturbations in the grid problem data and a hypothetical computer with controlled computer perturbations. The conditions on admissible perturbations in the grid problem data and on admissible computer perturbations are obtained under which the computer difference scheme converges in the maximum norm for ɛ ∈ (0, 1] at the same rate as the standard scheme in the absence of perturbations.

  11. Differences in evolutionary pressure acting within highly conserved ortholog groups

    Directory of Open Access Journals (Sweden)

    Aravind L

    2008-07-01

    Full Text Available Abstract Background In highly conserved widely distributed ortholog groups, the main evolutionary force is assumed to be purifying selection that enforces sequence conservation, with most divergence occurring by accumulation of neutral substitutions. Using a set of ortholog groups from prokaryotes, with a single representative in each studied organism, we asked the question if this evolutionary pressure is acting similarly on different subgroups of orthologs defined as major lineages (e.g. Proteobacteria or Firmicutes. Results Using correlations in entropy measures as a proxy for evolutionary pressure, we observed two distinct behaviors within our ortholog collection. The first subset of ortholog groups, called here informational, consisted mostly of proteins associated with information processing (i.e. translation, transcription, DNA replication and the second, the non-informational ortholog groups, mostly comprised of proteins involved in metabolic pathways. The evolutionary pressure acting on non-informational proteins is more uniform relative to their informational counterparts. The non-informational proteins show higher level of correlation between entropy profiles and more uniformity across subgroups. Conclusion The low correlation of entropy profiles in the informational ortholog groups suggest that the evolutionary pressure acting on the informational ortholog groups is not uniform across different clades considered this study. This might suggest "fine-tuning" of informational proteins in each lineage leading to lineage-specific differences in selection. This, in turn, could make these proteins less exchangeable between lineages. In contrast, the uniformity of the selective pressure acting on the non-informational groups might allow the exchange of the genetic material via lateral gene transfer.

  12. Novel UEP LT Coding Scheme with Feedback Based on Different Degree Distributions

    Directory of Open Access Journals (Sweden)

    Li Ya-Fang

    2016-01-01

    Full Text Available Traditional unequal error protection (UEP schemes have some limitations and problems, such as the poor UEP performance of high priority data and the seriously sacrifice of low priority data in decoding property. Based on the reasonable applications of different degree distributions in LT codes, this paper puts forward a novel UEP LT coding scheme with a simple feedback to compile these data packets separately. Simulation results show that the proposed scheme can effectively protect high priority data, and improve the transmission efficiency of low priority data from 2.9% to 22.3%. Furthermore, it is fairly suitable to apply this novel scheme to multicast and broadcast environments since only a simple feedback introduced.

  13. Compact difference scheme for the fractional sub-diffusion equation with Neumann boundary conditions

    Science.gov (United States)

    Ren, Jincheng; Sun, Zhi-zhong; Zhao, Xuan

    2013-01-01

    An effective finite difference scheme is considered for solving the time fractional sub-diffusion equation with Neumann boundary conditions. A difference scheme combining the compact difference approach the spatial discretization and L1 approximation for the Caputo fractional derivative is proposed and analyzed. Although the spatial approximation order at the Neumann boundary is one order lower than that for interior mesh points, the unconditional stability and the global convergence order O(τ+h4) in discrete L2 norm of the compact difference scheme are proved rigorously, where τ is the temporal grid size and h is the spatial grid size. Numerical experiments are included to support the theoretical results, and comparison with the related works are presented to show the effectiveness of our method.

  14. From Paper to Forest: Local Motives for Participation in Different Conservation Initiatives. Case Studies in Southeastern Mexico

    Science.gov (United States)

    Méndez-López, María Elena; García-Frapolli, Eduardo; Ruiz-Mallén, Isabel; Porter-Bolland, Luciana; Reyes-Garcia, Victoria

    2015-09-01

    Under the assumption that local participation can contribute toward conservation, various policies have sought to increase the participation of local communities in conservation, but not always with success. Despite this failure, the drivers that explain local participation remain unclear and few studies have attempted to understand the motivations behind involvement (or lack of it) in different conservation initiatives and adopting the perspective of the local stakeholder. In this study, we analyze the motives behind the participation (or lack thereof) of local populations in three conservation schemes: Protected Areas, Areas Voluntary Devoted to Conservation, and areas under Payment for Environmental Services. The study, conducted in 6 communities of southeastern Mexico, comprises an ethnographic stage and the application of a survey exploring the motives for participation. Our results show similarities among the motives for participation in these three initiatives, predominantly the obligation to comply with acquired commitments and a desire to "care for the land". Results also show that 77 % of the people interviewed did not participate in any conservation initiatives, often due to the lack of mechanisms by which to participate. We conclude by questioning the feasibility of achieving local participation in conservation as currently proposed and for the aims that are outlined.

  15. Effect of different lateral occlusion schemes on peri-implant strain: A laboratory study

    Science.gov (United States)

    Lo, Jennifer; Palamara, Joseph

    2017-01-01

    PURPOSE This study aims to investigate the effects of four different lateral occlusion schemes and different excursions on peri-implant strains of a maxillary canine implant. MATERIALS AND METHODS Four metal crowns with different occlusion schemes were attached to an implant in the maxillary canine region of a resin model. The included schemes were canine-guided (CG) occlusion, group function (GF) occlusion, long centric (LC) occlusion, and implant-protected (IP) occlusion. Each crown was loaded in three sites that correspond to maximal intercuspation (MI), 1 mm excursion, and 2 mm excursion. A load of 140 N was applied on each site and was repeated 10 times. The peri-implant strain was recorded by a rosette strain gauge that was attached on the resin model buccal to the implant. For each loading condition, the maximum shear strain value was calculated. RESULTS The different schemes and excursive positions had impact on the peri-implant strains. At MI and 1 mm positions, the GF had the least strains, followed by IP, CG, and LC. At 2 mm, the least strains were associated with GF, followed by CG, LC, and IP. However, regardless of the occlusion scheme, as the excursion increases, a linear increase of peri-implant strains was detected. CONCLUSION The peri-implant strain is susceptible to occlusal factors. The eccentric location appears to be more influential on peri-implant strains than the occlusion scheme. Therefore, adopting an occlusion scheme that can reduce the occurrence of occlusal contacts laterally may be beneficial in reducing peri-implant strains. PMID:28243391

  16. Numerical Simulation of Chennai Heavy Rainfall Using MM5 Mesoscale Model with Different Cumulus Parameterization Schemes

    Science.gov (United States)

    Litta, A. J.; Chakrapani, B.; Mohankumar, K.

    2007-07-01

    Heavy rainfall events become significant in human affairs when they are combined with hydrological elements. The problem of forecasting heavy precipitation is especially difficult since it involves making a quantitative precipitation forecast, a problem well recognized as challenging. Chennai (13.04°N and 80.17°E) faced incessant and heavy rain about 27 cm in 24 hours up to 8.30 a.m on 27th October 2005 completely threw life out of gear. This torrential rain caused by deep depression which lay 150km east of Chennai city in Bay of Bengal intensified and moved west north-west direction and crossed north Tamil Nadu and south Andhra Pradesh coast on 28th morning. In the present study, we investigate the predictability of the MM5 mesoscale model using different cumulus parameterization schemes for the heavy rainfall event over Chennai. MM5 Version 3.7 (PSU/NCAR) is run with two-way triply nested grids using Lambert Conformal Coordinates (LCC) with a nest ratio of 3:1 and 23 vertical layers. Grid sizes of 45, 15 and 5 km are used for domains 1, 2 and 3 respectively. The cumulus parameterization schemes used in this study are Anthes-Kuo scheme (AK), the Betts-Miller scheme (BM), the Grell scheme (GR) and the Kain-Fritsch scheme (KF). The present study shows that the prediction of heavy rainfall is sensitive to cumulus parameterization schemes. In the time series of rainfall, Grell scheme is in good agreement with observation. The ideal combination of the nesting domains, horizontal resolution and cloud parameterization is able to simulate the heavy rainfall event both qualitatively and quantitatively.

  17. Recovery schemes for different distributed connection management in generalized multi-protocol label switching networks

    Institute of Scientific and Technical Information of China (English)

    Can Wang; Yuefeng Ji

    2007-01-01

    As the wavelength division multiplexing (WDM) technology matures and the demands for bandwidth increase, survivability becomes more and more important in generalized multi-protocol label switching (GMPLS) controlled intelligent optical networks (IONs). There are great interests to study the performance of restorability under one certain connection management strategy. And studies in the problem of providing recovery from link failures under two different resource reservation schemes, forward reservation protocols (FRPs) and backward reservation protocols (BRPs), are presented. They are examined from the point of view of connection blocking probability, restorability and average recovery time. The two different connection management schemes and the survey of different recovery schemes are first presented. The performance of these recovery strategies is analyzed and compared both through theoretical analysis and simulation results. The main stressed idea is that using BRPs gives the best performance in terms of restorability and blocking probability in restorable GMPLS networks.

  18. A Finite Difference Scheme for Solving the Undamped Timoshenko Beam Equations with Both Ends Free

    Institute of Scientific and Technical Information of China (English)

    Fu-le LI; Zong-hu XIU

    2012-01-01

    In this paper,a boundary feedback system of a class of non-uniform undamped Timoshenko beam with both ends free is considered.A linearized three-level difference scheme for the Timoshenko beam equations is derived by the method of reduction of order on uniform meshes.The unique solvability,unconditional stability and convergence of the difference scheme are proved by the discrete energy method.The convergence order in maximum norm is of order two in both space and time. The validity of this theoretical analysis is verified experimentally.

  19. Central serotonin depletion affects rat brain areas differently: a qualitative and quantitative comparison between different treatment schemes

    DEFF Research Database (Denmark)

    Kornum, Birgitte Rahbek; Licht, Cecilie Löe; Weikop, Pia

    2006-01-01

    , no studies have systematically examined and compared different approaches. The present work combines quantitative and qualitative measurements and compares six different treatment schemes for 5-HT depletion. Treatment outcome was evaluated by HPLC measurements of 5-HT and 5-HIAA concentrations, and by 5-HT...

  20. Conservation planning with insects at three different spatial scales

    NARCIS (Netherlands)

    Cabeza, M.; Arponen, A.; Jäätelä, L.; Kujala, H.; Teeffelen, van A.J.A.; Hanski, I.

    2010-01-01

    Deciding which areas to protect, and where to manage and how, are no easy tasks. Many protected areas were established opportunistically under strong political and economic constraints, which may have resulted in inefficient and ineffective conservation. Systematic conservation planning has helped u

  1. High Order Finite Difference Schemes for the Elastic Wave Equation in Discontinuous Media

    CERN Document Server

    Virta, Kristoffer

    2013-01-01

    Finite difference schemes for the simulation of elastic waves in materi- als with jump discontinuities are presented. The key feature is the highly accurate treatment of interfaces where media discontinuities arise. The schemes are constructed using finite difference operators satisfying a sum- mation - by - parts property together with a penalty technique to impose interface conditions at the material discontinuity. Two types of opera- tors are used, termed fully compatible or compatible. Stability is proved for the first case by bounding the numerical solution by initial data in a suitably constructed semi - norm. Numerical experiments indicate that the schemes using compatible operators are also stable. However, the nu- merical studies suggests that fully compatible operators give identical or better convergence and accuracy properties. The numerical experiments are also constructed to illustrate the usefulness of the proposed method to simulations involving typical interface phenomena in elastic materials...

  2. High-Order Finite Difference GLM-MHD Schemes for Cell-Centered MHD

    CERN Document Server

    Mignone, A; Bodo, G

    2010-01-01

    We present and compare third- as well as fifth-order accurate finite difference schemes for the numerical solution of the compressible ideal MHD equations in multiple spatial dimensions. The selected methods lean on four different reconstruction techniques based on recently improved versions of the weighted essentially non-oscillatory (WENO) schemes, monotonicity preserving (MP) schemes as well as slope-limited polynomial reconstruction. The proposed numerical methods are highly accurate in smooth regions of the flow, avoid loss of accuracy in proximity of smooth extrema and provide sharp non-oscillatory transitions at discontinuities. We suggest a numerical formulation based on a cell-centered approach where all of the primary flow variables are discretized at the zone center. The divergence-free condition is enforced by augmenting the MHD equations with a generalized Lagrange multiplier yielding a mixed hyperbolic/parabolic correction, as in Dedner et al. (J. Comput. Phys. 175 (2002) 645-673). The resulting...

  3. COMPACT FOURTH-ORDER FINITE DIFFERENCE SCHEMES FOR HELMHOLTZ EQUATION WITH HIGH WAVE NUMBERS

    Institute of Scientific and Technical Information of China (English)

    Yiping Fu

    2008-01-01

    In this paper,two fourth-order accurate compact difference schemes are presented for solving the Helmholtz equation in two space dimensions when the corresponding wave numbers are large.The main idea is to derive and to study a fourth-order accurate compact difference scheme whose leading truncation term,namely,the O(h4) term,is independent of the wave number and the sohrtion of the Helmholtz equation.The convergence property of the compact schemes are analyzed and the implementation of solving the resulting linear algebraic system based on a FFT approach is considered.Numerical results are presented,which support our theoretical predictions.Mathematics subject classification:65M06,65N12.

  4. Influence of Different PBL Schemes on Secondary Eyewall Formation and Eyewall Replacement Cycle in Simulated Typhoon Sinlaku (2008)

    Science.gov (United States)

    Zhang, Yutao

    2017-04-01

    The effects of the different planetary boundary layer (PBL) processes on the secondary eyewall formation (SEF) and eyewall replacement cycle (ERC) in Typhoon Sinlaku (2008) are investigated by using the Weather Research and Forecasting Model (WRF) with six different PBL schemes. The SEF and ERC have been successfully simulated with all the six PBL schemes and the mechanism of the SEF and ERC proposed in our previous study has been reconfirmed: It is demonstrated that both the intensification of the storm and the inward-moving outer spiral rainband contribute to the SEF. After the SEF, the associated diabatic heating enhances the secondary eyewall further and transfer of the moist air from outer region to the primary eyewall is cut off by the secondary eyewall. In such a way the primary eyewall dies and an ERC completes. It is found that some simulated features of the SEF and ERC, such as the time and location of the SEF and duration of the ERC, do vary from one simulation to another. In order to describe the feature of the SEF and ERC quantitatively, a concentric eyewall index (CEI) is defined and a threshold of the CEI is suggested to determine the onset of the secondary eyewall. The differences of the simulated SEF and ERC are discussed and some possible causes are suggested. In addition, based on the threshold of the CEI and the conservation law of the angular momentum a formula to predict the location of the SEF is also suggested and applied to all the six simulations. The success and failure of the formula are also discussed. Key words: eye-wall replacement cycle, secondary eye-wall formation, PBL scheme, CEI

  5. Renewable energy investments under different support schemes: A real options approach

    DEFF Research Database (Denmark)

    Boomsma, Trine Krogh; Meade, Nigel; Fleten, Stein-Erik

    2012-01-01

    This paper adopts a real options approach to analyze investment timing and capacity choice for renewable energy projects under different support schemes. The main purpose is to examine investment behavior under the most extensively employed support schemes, namely, feed-in tariffs and renewable......-in tariff encourages earlier investment. Nevertheless, as investment has been undertaken, renewable energy certificate trading creates incentives for larger projects. In our baseline scenario and taking the fixed feed-in tariff as a base, the revenue required to trigger investments is 61% higher...... with renewable certificates. At the same time, investment capacity is 61% higher....

  6. Performance comparison of different graylevel image fusion schemes through a universal image quality index

    NARCIS (Netherlands)

    Toet, A.; Hogervorst, M.A.

    2003-01-01

    We applied a recently introduced universal image quality index Q that quantifies the distortion of a processed image relative to its original version, to assess the performance of different graylevel image fusion schemes. The method is as follows. First, we adopt an original test image as the refere

  7. Stability of finite difference schemes for generalized von Foerster equations with renewal

    Directory of Open Access Journals (Sweden)

    Henryk Leszczyński

    2014-01-01

    Full Text Available We consider a von Foerster-type equation describing the dynamics of a population with the production of offsprings given by the renewal condition. We construct a finite difference scheme for this problem and give sufficient conditions for its stability with respect to \\(l^1\\ and \\(l^\\infty\\ norms.

  8. HIGH-ORDER I-STABLE CENTERED DIFFERENCE SCHEMES FOR VISCOUS COMPRESSIBLE FLOWS

    Institute of Scientific and Technical Information of China (English)

    Weizhu Bao; Shi Jin

    2003-01-01

    In this paper we present high-order I-stable centered difference schemes for the numer-ical simulation of viscous compressible flows. Here I-stability refers to time discretizationswhose linear stability regions contain part of the imaginary axis. This class of schemeshas a numerical stability independent of the cell-Reynolds number Rc, thus allows one tosimulate high Reynolds number flows with relatively larger Rc, or coarser grids for a fixedRc. On the other hand, Rc cannot be arbitrarily large if one tries to obtain adequatenumerical resolution of the viscous behavior. We investigate the behavior of high-orderI-stable schemes for Burgers' equation and the compressible Navier-Stokes equations. Wedemonstrate that, for the second order scheme, Rc ≤ 3 is an appropriate constraint for nu-merical resolution of the viscous profile, while for the fourth-order schemes the constraintcan be relaxed to Rc ≤ 6. Our study indicates that the fourth order scheme is preferable:better accuracy, higher resolution, and larger cell-Reynolds numbers.

  9. Change in Farm Production Structure Within Different CAP Schemes – an LP Modelling Approach

    Directory of Open Access Journals (Sweden)

    Jaka ŽGAJNAR

    2008-01-01

    Full Text Available After accession to European Union in 2004 direct payments became veryimportant income source also for farmers in Slovenia. But agricultural policy inplace at accession changed significantly in year 2007 as result of CAP reformimplementation. The objective of this study was to evaluate decision makingimpacts of direct payments scheme implemented with the reform: regional or morelikely hybrid scheme. The change in farm production structure was simulated withmodel, applying gross margin maximisation, based on static linear programmingapproach. The model has been developed in a spreadsheet framework in MS Excelplatform. A hypothetical farm has been chosen to analyse different scenarios andspecializations. Focus of the analysis was on cattle sector, since it is expected thatdecoupling is going to have significant influence on its optimal productionstructure. The reason is high level of direct payments that could in pre-reformscheme rise up to 70 % of total gross margin. Model results confirm that the reformshould have unfavourable impacts on cattle farms with intensive productionpractice. The results show that hybrid scheme has minor negative impacts in allcattle specializations, while regional scheme would be better option for sheepspecialized farm. Analysis has also shown growing importance of CAP pillar IIpayments, among them particularly agri-environmental measures. In all threeschemes budgetary payments enable farmers to improve financial results and inboth reform schemes they alleviate economic impacts of the CAP reform.

  10. Computational fluid dynamics modelling of biomass fast pyrolysis in fluidised bed reactors, focusing different kinetic schemes.

    Science.gov (United States)

    Ranganathan, Panneerselvam; Gu, Sai

    2016-08-01

    The present work concerns with CFD modelling of biomass fast pyrolysis in a fluidised bed reactor. Initially, a study was conducted to understand the hydrodynamics of the fluidised bed reactor by investigating the particle density and size, and gas velocity effect. With the basic understanding of hydrodynamics, the study was further extended to investigate the different kinetic schemes for biomass fast pyrolysis process. The Eulerian-Eulerian approach was used to model the complex multiphase flows in the reactor. The yield of the products from the simulation was compared with the experimental data. A good comparison was obtained between the literature results and CFD simulation. It is also found that CFD prediction with the advanced kinetic scheme is better when compared to other schemes. With the confidence obtained from the CFD models, a parametric study was carried out to study the effect of biomass particle type and size and temperature on the yield of the products.

  11. ON THE CONSTRUCTION OF PARTIAL DIFFERENCE SCHEMES II: DISCRETE VARIABLES AND SCHWARZIAN LATTICES

    Directory of Open Access Journals (Sweden)

    Decio Levi

    2016-06-01

    Full Text Available In the process of constructing invariant difference schemes which approximate partial differential equations we write down a procedure for discretizing a partial differential equation on an arbitrary lattice. An open problem is the meaning of a lattice which does not satisfy the Clairaut–Schwarz–Young theorem. To analyze it we apply the procedure on a simple example, the potential Burgers equation with two different lattices, an orthogonal lattice which is invariant under the symmetries of the equation and satisfies the commutativity of the partial difference operators and an exponential lattice which is not invariant and does not satisfy the Clairaut–Schwarz–Young theorem. A discussion on the numerical results is presented showing the different behavior of both schemes for two different exact solutions and their numerical approximations.

  12. On a difference scheme for nonlocal heat transfer boundary-value problem

    Science.gov (United States)

    Akhymbek, Meiram E.; Sadybekov, Makhmud A.

    2016-08-01

    In this paper, we propose a new method of solving nonlocal problems for the heat equation with finite difference method. The main important feature of these problems is their non-self-adjointness. This non-self-adjointness causes major difficulties in their analytical and numerical solving. The problems, which boundary conditions do not possess strong regularity, are less studied. The scope of study of the paper justifies possibility of building a stable difference scheme with weights for abovementioned type of problems.

  13. Semi-discrete finite difference multiscale scheme for a concrete corrosion model: approximation estimates and convergence

    CERN Document Server

    Chalupecký, Vladimír

    2011-01-01

    We propose a semi-discrete finite difference multiscale scheme for a concrete corrosion model consisting of a system of two-scale reaction-diffusion equations coupled with an ode. We prove energy and regularity estimates and use them to get the necessary compactness of the approximation estimates. Finally, we illustrate numerically the behavior of the two-scale finite difference approximation of the weak solution.

  14. Evaluating the Performance of the Goddard Multi-Scale Modeling Framework with Different Cloud Microphysical Schemes

    Science.gov (United States)

    Chern, J.; Tao, W.; Lang, S. E.; Matsui, T.

    2012-12-01

    The accurate representation of clouds and cloud processes in atmospheric general circulation models (GCMs) with relatively coarse resolution (~100 km) has been a long-standing challenge. With the rapid advancement in computational technology, new breed of GCMs that are capable of explicitly resolving clouds have been developed. Though still computationally very expensive, global cloud-resolving models (GCRMs) with horizontal resolutions of 3.5 to 14 km are already being run in an exploratory manner. Another less computationally demanding approach is the multi-scale modeling framework (MMF) that replaces conventional cloud parameterizations with a cloud-resolving model (CRM) in each grid column of a GCM. The Goddard MMF is based on the coupling of the Goddard Cumulus Ensemble (GCE), a CRM model, and the GEOS global model. In recent years a few new and improved microphysical schemes are developed and implemented to the GCE based on observations from field campaigns. It is important to evaluating these microphysical schemes for global applications such as the MMFs and GCRMs. Two-year (2007-2008) MMF sensitivity experiments have been carried out with different cloud microphysical schemes. The model simulated mean and variability of surface precipitation, cloud types, cloud properties such as cloud amount, hydrometeors vertical profiles, and cloud water contents, etc. in different geographic locations and climate regimes are evaluated against TRMM, CloudSat and CALIPSO satellite observations. The Goddard MMF has also been coupled with the Goddard Satellite Data Simulation Unit (G-SDSU), a system with multi-satellite, multi-sensor, and multi-spectrum satellite simulators. The statistics of MMF simulated radiances and backscattering can be directly compared with satellite observations to evaluate the performance of different cloud microphysical schemes. We will assess the strengths and/or deficiencies in of these microphysics schemes and provide guidance on how to improve

  15. Comparative study of numerical schemes of TVD3, UNO3-ACM and optimized compact scheme

    Science.gov (United States)

    Lee, Duck-Joo; Hwang, Chang-Jeon; Ko, Duck-Kon; Kim, Jae-Wook

    1995-01-01

    Three different schemes are employed to solve the benchmark problem. The first one is a conventional TVD-MUSCL (Monotone Upwind Schemes for Conservation Laws) scheme. The second scheme is a UNO3-ACM (Uniformly Non-Oscillatory Artificial Compression Method) scheme. The third scheme is an optimized compact finite difference scheme modified by us: the 4th order Runge Kutta time stepping, the 4th order pentadiagonal compact spatial discretization with the maximum resolution characteristics. The problems of category 1 are solved by using the second (UNO3-ACM) and third (Optimized Compact) schemes. The problems of category 2 are solved by using the first (TVD3) and second (UNO3-ACM) schemes. The problem of category 5 is solved by using the first (TVD3) scheme. It can be concluded from the present calculations that the Optimized Compact scheme and the UN03-ACM show good resolutions for category 1 and category 2 respectively.

  16. Performance Analysis of DWDM System for Different Modulation Schemes Using Variations in Channel Spacing

    Science.gov (United States)

    Sharma, Divya; Prajapati, Y. K.

    2016-12-01

    This paper reflects the analytical study of dense wavelength division multiplexed optical network with different number of channels at various channel spacing in order to achieve higher data rates by means of few advanced modulation schemes. Bit error rate and quality factor are being analyzed with the variation in number of channels, channel spacing and transmission length of fiber. Advanced modulation schemes being compared here are carrier suppressed return to zero (CSRZ), duobinary return to zero (DRZ), modified duobinary return to zero (MDRZ), 33 % differential phase shift keying (33 % DPSK), 66 % DPSK and differential quaternary phase shift keying (DQPSK). It is keenly observed that CSRZ scheme with 100 GHz channel spacing serves best performance in terms of max. Q factor, min. BER and maximum transmission coverage upto 4,000 km for 16 and 32 channels DWDM system since CSRZ is high tolerant to nonlinear effects. On the other hand, MDRZ scheme with 75 GHz channel spacing exhibits transmission coverage upto 4,000 km and 4,500 km for 16 and 32 channels respectively, but with degraded signal due to effect of inter symbol interference (ISI).

  17. Lie group invariant finite difference schemes for the neutron diffusion equation

    Energy Technology Data Exchange (ETDEWEB)

    Jaegers, P.J.

    1994-06-01

    Finite difference techniques are used to solve a variety of differential equations. For the neutron diffusion equation, the typical local truncation error for standard finite difference approximation is on the order of the mesh spacing squared. To improve the accuracy of the finite difference approximation of the diffusion equation, the invariance properties of the original differential equation have been incorporated into the finite difference equations. Using the concept of an invariant difference operator, the invariant difference approximations of the multi-group neutron diffusion equation were determined in one-dimensional slab and two-dimensional Cartesian coordinates, for multiple region problems. These invariant difference equations were defined to lie upon a cell edged mesh as opposed to the standard difference equations, which lie upon a cell centered mesh. Results for a variety of source approximations showed that the invariant difference equations were able to determine the eigenvalue with greater accuracy, for a given mesh spacing, than the standard difference approximation. The local truncation errors for these invariant difference schemes were found to be highly dependent upon the source approximation used, and the type of source distribution played a greater role in determining the accuracy of the invariant difference scheme than the local truncation error.

  18. Baroclinic pressure gradient difference schemes of subtracting the local averaged density stratification in sigma coordinates models

    Institute of Scientific and Technical Information of China (English)

    ZHU Shouxian; ZHANG Wenjing

    2008-01-01

    Much has been written of the error in computing the baroclinic pressure gradient (BPG) with sigma coordinates in ocean or atmos- pheric numerical models. The usual way to reduce the error is to subtract area-averaged density stratification of the whole computa- tion region. But if there is great difference between the area-averaged and the local averaged density stratification, the error will be obvious. An example is given to show that the error from this method may be larger than that from no correction sometimes. The definition of local area is put forward. Then, four improved BPG difference schemes of subtracting the local averaged density strat- ification are designed to reduce the error. Two of them are for diagnostic calculation (density field is fixed), and the others are for prognostic calculation (density field is not fixed). The results show that the errors from these schemes all significantly decrease.

  19. A nonstandard finite difference scheme for a basic model of cellular immune response to viral infection

    Science.gov (United States)

    Korpusik, Adam

    2017-02-01

    We present a nonstandard finite difference scheme for a basic model of cellular immune response to viral infection. The main advantage of this approach is that it preserves the essential qualitative features of the original continuous model (non-negativity and boundedness of the solution, equilibria and their stability conditions), while being easy to implement. All of the qualitative features are preserved independently of the chosen step-size. Numerical simulations of our approach and comparison with other conventional simulation methods are presented.

  20. Fault Characteristics and Protection Scheme of the MMC-UPFC under Different Grounding Design

    Science.gov (United States)

    Zheng, Tao; Wang, Ketan; Wu, Dan; Qi, Huanhuan

    2017-07-01

    The Unified Power Flow Controller (UPFC) based on Modular Multilevel Converter (MMC) is more suitable for high-voltage and large-capacity transmission fields. According to the actual needs of demonstration project, 3 grounding proposals were brought out and the effect of different grounding proposals to the fault characteristics and protection schemes is analyzed in detail. The conclusion that only parallel valve side star connected large resistance grounding is more advantageous in MMC-UPFC was derived.

  1. LONG TIME ASYMPTOTIC BEHAVIOR OF SOLUTION OF IMPLICIT DIFFERENCE SCHEME FOR A SEMI-LINEAR PARABOLIC EQUATION

    Institute of Scientific and Technical Information of China (English)

    Zhi-zhong Sun; Long-Jun Shen

    2003-01-01

    In this paper, the solution of back-Euler implicit difference scheme for a semi-linearparabolic equation is proved to converge to the solution of difference scheme for the corre-sponding semi-linear elliptic equation as t tends to infinity. The long asymptotic behaviorof its discrete solution is obtained which is analogous to that of its continuous solution. Atlast, a few results are also presented for Crank-Nicolson scheme.

  2. The costs and benefits of a migratory species under different management schemes.

    Science.gov (United States)

    Skonhoft, Anders

    2005-07-01

    This paper analyses how different management schemes influence the exploitation and economics of a wildlife population--the moose (Alces alces)--that is both a value (harvesting income) and a pest (forestry damage). Two regimes are explored; the unified management scheme where the wildlife manager aims to find harvesting quotas that maximise the overall benefit of the moose population, and the market solution where the landowners follow their narrow self-interests and maximise their private profit. Because the moose is partly a migratory species, these regimes will differ both with respect to harvesting income and browsing damage, and the landowners will experience different profit. The unified scheme is very similar to the actual Scandinavian management, while the market solution is closer to the management policy one finds in North America. In the first part of the paper it is shown how the harvesting quotas and browsing damage under these two regimes are influenced by dispersal as well as other ecological and economic factors. In the last part of the paper it is demonstrated that under the unified management regime the present practice of neglecting migration may lead to sub-optimally sized populations of migrating moose and an overall economic loss. It is also shown that neglecting migration leads to a substantial profit transfer among the landowners. The model is supported by a real life numerical example.

  3. A comparison of temperature and precipitation responses to different Earth radiation management geoengineering schemes

    Science.gov (United States)

    Crook, J. A.; Jackson, L. S.; Osprey, S. M.; Forster, P. M.

    2015-09-01

    Earth radiation management has been suggested as a way to rapidly counteract global warming in the face of a lack of mitigation efforts, buying time and avoiding potentially catastrophic warming. We compare six different radiation management schemes that use surface, troposphere, and stratosphere interventions in a single climate model in which we projected future climate from 2020 to 2099 based on RCP4.5. We analyze the surface air temperature responses to determine how effective the schemes are at returning temperature to its 1986-2005 climatology and analyze precipitation responses to compare side effects. We find crop albedo enhancement is largely ineffective at returning temperature to its 1986-2005 climatology. Desert albedo enhancement causes excessive cooling in the deserts and severe shifts in tropical precipitation. Ocean albedo enhancement, sea-spray geoengineering, cirrus cloud thinning, and stratospheric SO2 injection have the potential to cool more uniformly, but cirrus cloud thinning may not be able to cool by much more than 1 K globally. We find that of the schemes potentially able to return surface air temperature to 1986-2005 climatology under future greenhouse gas warming, none has significantly less severe precipitation side effects than other schemes. Despite different forcing patterns, ocean albedo enhancement, sea-spray geoengineering, cirrus cloud thinning, and stratospheric SO2 injection all result in large scale tropical precipitation responses caused by Hadley cell changes and land precipitation changes largely driven by thermodynamic changes. Widespread regional scale changes in precipitation over land are significantly different from the 1986-2005 climatology and would likely necessitate significant adaptation despite geoengineering.

  4. A 3D staggered-grid finite difference scheme for poroelastic wave equation

    Science.gov (United States)

    Zhang, Yijie; Gao, Jinghuai

    2014-10-01

    Three dimensional numerical modeling has been a viable tool for understanding wave propagation in real media. The poroelastic media can better describe the phenomena of hydrocarbon reservoirs than acoustic and elastic media. However, the numerical modeling in 3D poroelastic media demands significantly more computational capacity, including both computational time and memory. In this paper, we present a 3D poroelastic staggered-grid finite difference (SFD) scheme. During the procedure, parallel computing is implemented to reduce the computational time. Parallelization is based on domain decomposition, and communication between processors is performed using message passing interface (MPI). Parallel analysis shows that the parallelized SFD scheme significantly improves the simulation efficiency and 3D decomposition in domain is the most efficient. We also analyze the numerical dispersion and stability condition of the 3D poroelastic SFD method. Numerical results show that the 3D numerical simulation can provide a real description of wave propagation.

  5. Linking renewable energy CDM projects and TGC schemes: An analysis of different options

    Energy Technology Data Exchange (ETDEWEB)

    Del Rio, Pablo [Department of Economics and Business, Facultad de Ciencias Juridicas y Sociales, Universidad de Castilla-La Mancha, C/ Cobertizo de S. Pedro Martir s/n., Toledo-45071 (Spain)]. E-mail: pablo.rio@uclm.es

    2006-11-15

    Renewable energy CDM (RE-CDM) projects encourage cost-effective GHG mitigation and enhanced sustainable development opportunities for the host countries. CERs from CDM projects include the value of the former benefits (i.e., 'climate change benefits'), whereas the second can be given value through the issuing and trading of tradable green certificates (TGCs). Countries could agree to trade these TGCs, leading to additional revenues for the investors in renewable energy projects and, therefore, further encouraging the deployment of CDM projects, currently facing significant barriers. However, the design of a combination of CDM projects and TGC schemes raises several conflicting issues and leads to trade-offs. This paper analyses these issues, identifies the alternatives that may exist to link TGC schemes with RE-CDM projects and analyses the impacts of those options on different variables and actors.

  6. A Crank-Nicolson Difference Scheme for Solving a Type of Variable Coefficient Delay Partial Differential Equations

    Directory of Open Access Journals (Sweden)

    Wei Gu

    2014-01-01

    Full Text Available A linearized Crank-Nicolson difference scheme is constructed to solve a type of variable coefficient delay partial differential equations. The difference scheme is proved to be unconditionally stable and convergent, where the convergence order is two in both space and time. A numerical test is provided to illustrate the theoretical results.

  7. Simulation of black carbon aerosol distribution over India: A sensitivity study to different convective schemes

    Science.gov (United States)

    Ghosh, Sudipta; Dey, Sagnik; Das, Sushant; Venkataraman, Chandra; Patil, Nitin U.

    2017-04-01

    Black carbon (BC) aerosols absorb solar radiation, thereby causing a warming at the top-of-the-atmosphere (TOA) in contrast to most of the other aerosol species that scatter radiation causing a cooling at TOA. BC is considered to be an important contributor of global warming, second only to CO2 with a net radiative forcing of 1.1 w/m2. They have important regional climate effects, because of their spatially non-uniform heating and cooling. So it is very important to understand the spatio-temporal distribution of BC over India. In this study, we have used a regional climate model RegCM4.5 to simulate BC distribution over India with a focus on the BC estimation. The importance of incorporation of regional emission inventory has been shown and the sensitivity of BC distribution to various convective schemes in the model has been explored. The model output has been validated with in-situ observations. It is quite evident that regional inventory is capturing larger columnar burden of BC and OC than the global inventory. The difference in BC burden is clear at many places with the largest difference (in the order from 2 x 10-11 kg m-2 sec-1 in global inventory to 4 x 10-11 kg m-2 sec-1 in regional inventory) being observed over the Indo-Gangetic Basin. This difference is mainly attributed to the local sources like kerosene lamp burning, residential cooking on solid biomass fuel and agricultural residue burning etc., that are not considered in the global inventory. The difference is also noticeable for OC. Thus BC burden has increased with incorporation of regional emission inventory in the model, suggesting the importance of regional inventory in improved simulation and estimation of aerosols in this region. BC distribution is also sensitive to choice of scheme with Emanuel scheme capturing a comparatively smaller BC burden during the monsoon than Tiedtke scheme. Further long-term simulation with customized model is required to examine impact of BC. Keywords: Black

  8. A Staggered Fourth-Order Accurate Explicit Finite Difference Scheme for the Time-Domain Maxwell's Equations

    Science.gov (United States)

    Yefet, Amir; Petropoulos, Peter G.

    2001-04-01

    We consider a model explicit fourth-order staggered finite-difference method for the hyperbolic Maxwell's equations. Appropriate fourth-order accurate extrapolation and one-sided difference operators are derived in order to complete the scheme near metal boundaries and dielectric interfaces. An eigenvalue analysis of the overall scheme provides a necessary, but not sufficient, stability condition and indicates long-time stability. Numerical results verify both the stability analysis, and the scheme's fourth-order convergence rate over complex domains that include dielectric interfaces and perfectly conducting surfaces. For a fixed error level, we find the fourth-order scheme is computationally cheaper in comparison to the Yee scheme by more than an order of magnitude. Some open problems encountered in the application of such high-order schemes are also discussed.

  9. [Numerical evaluation of soil quality under different conservation tillage patterns].

    Science.gov (United States)

    Wu, Yu-Hong; Tian, Xiao-Hong; Chi, Wen-Bo; Nan, Xiong-Xiong; Yan, Xiao-Li; Zhu, Rui-Xiang; Tong, Yan-An

    2010-06-01

    A 9-year field experiment was conducted on the Guanzhong Plain of Shaanxi Province to study the effects of subsoiling, rotary tillage, straw return, no-till seeding, and traditional tillage on the soil physical and chemical properties and the grain yield in a winter wheat-summer maize rotation system, and a comprehensive evaluation was made on the soil quality under these tillage patterns by the method of principal components analysis (PCA). Comparing with traditional tillage, all the conservation tillage patterns improved soil fertility quality and soil physical properties. Under conservative tillage, the activities of soil urease and alkaline phosphatase increased significantly, soil quality index increased by 19.8%-44.0%, and the grain yield of winter wheat and summer maize (expect that under no till seeding with straw covering) increased by 13%-28% and 3%-12%, respectively. Subsoiling every other year, straw-chopping combined with rotary tillage, and straw-mulching combined with subsoiling not only increased crop yield, but also improved soil quality. Based on the economic and ecological benefits, the practices of subsoiling and straw return should be promoted.

  10. A multiscale scheme for the simulation of conformational and solution properties of different dendrimer molecules.

    Science.gov (United States)

    Del Río Echenique, Gustavo; Rodríguez Schmidt, Ricardo; Freire, Juan J; Hernández Cifre, José G; García de la Torre, José

    2009-06-24

    We propose a multiscale protocol for the simulation of conformation and dynamics of dendrimer molecules in dilute solution. Conformational properties (radius of gyration, mass distribution, and scattering intensities) and overall hydrodynamic properties (translational diffusion and intrinsic viscosity) are predicted by means of a very simple coarse-grained bead-and-spring model, whose parameters are not adjusted against experimental properties, but rather they are obtained from previous, atomic-level simulations which are also quite simple, performed with small fragments and Langevin dynamics simulation. The scheme is described and applied systematically to four different dendrimer molecules with up to seven generations. The predictive capability of this scheme is tested by comparison with experimental data. It is found that the predicted geometric and hydrodynamic radii of the dendrimer molecules are in agreement (typical error is about 4%) with a large set experimental values of the four dendrimers with various numbers of generations. Agreement with some X-ray scattering experimental intensities also confirms the good prediction of the internal structure. This scheme is easily extendable to study more complex molecules (e.g., functionalized dendrimers) and to simulate internal dynamics.

  11. An Efficient Explicit Finite-Difference Scheme for Simulating Coupled Biomass Growth on Nutritive Substrates

    Directory of Open Access Journals (Sweden)

    G. F. Sun

    2015-01-01

    Full Text Available A novel explicit finite-difference (FD method is presented to simulate the positive and bounded development process of a microbial colony subjected to a substrate of nutrients, which is governed by a nonlinear parabolic partial differential equations (PDE system. Our explicit FD scheme is uniquely designed in such a way that it transfers the nonlinear terms in the original PDE into discrete sets of linear ones in the algebraic equation system that can be solved very efficiently, while ensuring the stability and the boundedness of the solution. This is achieved through (1 a proper design of intertwined FD approximations for the diffusion function term in both time and spatial variations and (2 the control of the time-step through establishing theoretical stability criteria. A detailed theoretical stability analysis is conducted to reveal that our FD method is indeed stable. Our examples verified the fact that the numerical solution can be ensured nonnegative and bounded to simulate the actual physics. Numerical examples have also been presented to demonstrate the efficiency of the proposed scheme. The present scheme is applicable for solving similar systems of PDEs in the investigation of the dynamics of biological films.

  12. Nonstandard finite difference scheme for SIRS epidemic model with disease-related death

    Science.gov (United States)

    Fitriah, Z.; Suryanto, A.

    2016-04-01

    It is well known that SIRS epidemic with disease-related death can be described by a system of nonlinear ordinary differential equations (NL ODEs). This model has two equilibrium points where their existence and stability properties are determined by the basic reproduction number [1]. Besides the qualitative properties, it is also often needed to solve the system of NL ODEs. Euler method and 4th order Runge-Kutta (RK4) method are often used to solve the system of NL ODEs. However, both methods may produce inconsistent qualitative properties of the NL ODEs such as converging to wrong equilibrium point, etc. In this paper we apply non-standard finite difference (NSFD) scheme (see [2,3]) to approximate the solution of SIRS epidemic model with disease-related death. It is shown that the discrete system obtained by NSFD scheme is dynamically consistent with the continuous model. By our numerical simulations, we find that the solutions of NSFD scheme are always positive, bounded and convergent to the correct equilibrium point for any step size of integration (h), while those of Euler or RK4 method have the same properties only for relatively small h.

  13. Sensitivity of simulated terrestrial carbon assimilation and canopy transpiration to different stomatal conductance and carbon assimilation schemes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Haishan [Nanjing University of Information Science and Technology, Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing (China); Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA (United States); Dickinson, Robert E. [Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA (United States); The University of Texas at Austin, Department of Geological Sciences, Austin, TX (United States); Dai, Yongjiu [Beijing Normal University, State Key Laboratory of Earth Surface Processes and Resource Ecology, School of Global Change and Earth System Science, Beijing (China); Zhou, Liming [Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA (United States)

    2011-03-15

    Accurate simulations of terrestrial carbon assimilation and canopy transpiration are needed for both climate modeling and vegetation dynamics. Coupled stomatal conductance and carbon assimilation (A - g{sub s}) models have been widely used as part of land surface parameterizations in climate models to describe the biogeophysical and biogeochemical roles of terrestrial vegetation. Differences in various A - g{sub s} schemes produce substantial differences in the estimation of carbon assimilation and canopy transpiration, as well as in other land-atmosphere fluxes. The terrestrial carbon assimilation and canopy transpiration simulated by two different representative A - g{sub s} schemes, a simple A-g{sub s} scheme adopted from the treatments of the NCAR model (Scheme I) and a two-big-leaf A - g{sub s} scheme newly developed by Dai et al. (J Clim 17:2281-2299, 2004) (Scheme II), are compared via some sensitivity experiments to investigate impacts of different A - g{sub s} schemes on the simulations. Major differences are found in the estimate of canopy carbon assimilation rate, canopy conductance and canopy transpiration between the two schemes, primarily due to differences in (a) functional forms used to estimate parameters for carbon assimilation sub-models, (b) co-limitation methods used to estimate carbon assimilation rate from the three limiting rates, and (c) leaf-to-canopy scaling schemes. On the whole, the differences in the scaling approach are the largest contributor to the simulation discrepancies, but the different methods of co-limitation of assimilation rate also impact the results. Except for a few biomes, the residual effects caused by the different parameter estimations in assimilation sub-models are relatively small. It is also noted that the two-leaf temperature scheme produces distinctly different sunlit and shaded leaf temperatures but has negligible impacts on the simulation of the carbon assimilation. (orig.)

  14. The fragment spin difference scheme for triplet-triplet energy transfer coupling.

    Science.gov (United States)

    You, Zhi-Qiang; Hsu, Chao-Ping

    2010-08-21

    To calculate the electronic couplings in both inter- and intramolecular triplet energy transfer (TET), we have developed the "fragment spin difference" (FSD) scheme. The FSD was a generalization from the "fragment charge difference" (FCD) method of Voityuk et al. [J. Chem. Phys. 117, 5607 (2002)] for electron transfer (ET) coupling. In FSD, the spin population difference was used in place of the charge difference in FCD. FSD is derived from the eigenstate energies and populations, and therefore the FSD couplings contain all contributions in the Hamiltonian as well as the potential overlap effect. In the present work, two series of molecules, all-trans-polyene oligomers and polycyclic aromatic hydrocarbons, were tested for intermolecular TET study. The TET coupling results are largely similar to those from the previously developed direct coupling scheme, with FSD being easier and more flexible in use. On the other hand, the Dexter's exchange integral value, a quantity that is often used as an approximate for the TET coupling, varies in a large range as compared to the corresponding TET coupling. To test the FSD for intramolecular TET, we have calculated the TET couplings between zinc(II)-porphyrin and free-base porphyrin separated by different numbers of p-phenyleneethynylene bridge units. Our estimated rate constants are consistent with experimentally measured TET rates. The FSD method can be used for both intermolecular and intramolecular TET, regardless of their symmetry. This general applicability is an improvement over most existing methodologies.

  15. The fragment spin difference scheme for triplet-triplet energy transfer coupling

    Science.gov (United States)

    You, Zhi-Qiang; Hsu, Chao-Ping

    2010-08-01

    To calculate the electronic couplings in both inter- and intramolecular triplet energy transfer (TET), we have developed the "fragment spin difference" (FSD) scheme. The FSD was a generalization from the "fragment charge difference" (FCD) method of Voityuk et al. [J. Chem. Phys. 117, 5607 (2002)] for electron transfer (ET) coupling. In FSD, the spin population difference was used in place of the charge difference in FCD. FSD is derived from the eigenstate energies and populations, and therefore the FSD couplings contain all contributions in the Hamiltonian as well as the potential overlap effect. In the present work, two series of molecules, all-trans-polyene oligomers and polycyclic aromatic hydrocarbons, were tested for intermolecular TET study. The TET coupling results are largely similar to those from the previously developed direct coupling scheme, with FSD being easier and more flexible in use. On the other hand, the Dexter's exchange integral value, a quantity that is often used as an approximate for the TET coupling, varies in a large range as compared to the corresponding TET coupling. To test the FSD for intramolecular TET, we have calculated the TET couplings between zinc(II)-porphyrin and free-base porphyrin separated by different numbers of p-phenyleneethynylene bridge units. Our estimated rate constants are consistent with experimentally measured TET rates. The FSD method can be used for both intermolecular and intramolecular TET, regardless of their symmetry. This general applicability is an improvement over most existing methodologies.

  16. Asymptotically and exactly energy balanced augmented flux-ADER schemes with application to hyperbolic conservation laws with geometric source terms

    Science.gov (United States)

    Navas-Montilla, A.; Murillo, J.

    2016-07-01

    In this work, an arbitrary order HLL-type numerical scheme is constructed using the flux-ADER methodology. The proposed scheme is based on an augmented Derivative Riemann solver that was used for the first time in Navas-Montilla and Murillo (2015) [1]. Such solver, hereafter referred to as Flux-Source (FS) solver, was conceived as a high order extension of the augmented Roe solver and led to the generation of a novel numerical scheme called AR-ADER scheme. Here, we provide a general definition of the FS solver independently of the Riemann solver used in it. Moreover, a simplified version of the solver, referred to as Linearized-Flux-Source (LFS) solver, is presented. This novel version of the FS solver allows to compute the solution without requiring reconstruction of derivatives of the fluxes, nevertheless some drawbacks are evidenced. In contrast to other previously defined Derivative Riemann solvers, the proposed FS and LFS solvers take into account the presence of the source term in the resolution of the Derivative Riemann Problem (DRP), which is of particular interest when dealing with geometric source terms. When applied to the shallow water equations, the proposed HLLS-ADER and AR-ADER schemes can be constructed to fulfill the exactly well-balanced property, showing that an arbitrary quadrature of the integral of the source inside the cell does not ensure energy balanced solutions. As a result of this work, energy balanced flux-ADER schemes that provide the exact solution for steady cases and that converge to the exact solution with arbitrary order for transient cases are constructed.

  17. Stability analysis of finite difference schemes for quantum mechanical equations of motion

    Science.gov (United States)

    Chattaraj, P. K.; Deb, B. M.; Koneru, S. Rao

    1987-10-01

    For a pdf involving both space and time variables, stability criteria are presently shown to change drastically when the equation contains i, as in the quantum-mechanical equations of motion. It is further noted that the stability of finite difference schemes for quantum-mechanical equations of motion depends on both spatial and temporal zoning. It is possible to compare a free particle Green's function to the solution of a simple diffusion equation, and the quantum-mechanical motion of a free particle to Fresnel diffraction in optics.

  18. On the convergence of certain finite-difference schemes by an inverse-matrix method

    Science.gov (United States)

    Steger, J. L.; Warming, R. F.

    1975-01-01

    The inverse-matrix method of analyzing the convergence of the solution of a given system of finite-difference equations to the solution of the corresponding system of partial-differential equations is discussed and generalized. The convergence properties of a time- and space-centered differencing of the diffusion equation are analyzed as well as a staggered grid differencing of the Cauchy-Riemann equations. These two schemes are significant since they serve as simplified model algorithms for two recently developed methods used to calculate nonlinear aerodynamic flows.

  19. WEIGHTED COMPACT SCHEME FOR SHOCK CAPTURING

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new class of finite difference schemes--the weighted compact schemes are proposed. According to the idea of the WENO schemes, the weighted compact scheme is constructed by a combination of the approximations of derivatives on candidate stencils with properly assigned weights so that the non-oscillatory property is achieved when discontinuities appear. The primitive function reconstruction method of ENO schemes is applied to obtain the conservative form of the weighted compact scheme. This new scheme not only preserves the characteristic of standard compact schemes and achieves high order accuracy and high resolution using a compact stencil,but also can accurately capture shock waves and discontinuities without oscillation, Numerical examples show that the new scheme is very promising and successful.``

  20. On first- and second-order difference schemes for differential-algebraic equations of index at most two

    Science.gov (United States)

    Bulatov, M. V.; Ming-Gong, Lee; Solovarova, L. S.

    2010-11-01

    Difference schemes of the Euler and trapezoidal types for the numerical solution of the initial-value problem for linear differential-algebraic equations are examined. These schemes are analyzed for model examples, and their superiority over the familiar first- and second-order implicit methods is shown. Conditions for the convergence of the proposed algorithms are formulated.

  1. r-modified Crank-Nicholson difference schemes for one dimensional nonlinear viscous Burgers' equation for an incompressible flow

    Science.gov (United States)

    Ashyralyev, Allaberen; Gambo, Yusuf Ya'u.

    2016-08-01

    The nonlocal boundary value problem for viscous Burgers' equation is considered. Solutions to the 1-D equation are presented numerically by Rothe, Crank-Nicholson and r-modified Crank-Nicholson difference schemes. Matlab codes for all the three schemes are designed based on the idea of fixed-point iteration procedure and modified Gauss elimination method. The numerical results are compared.

  2. The effectiveness of integrated farm management, organic farming and agri-environment schemes for conserving biodiversity in temperate Europe - A systematic map

    Directory of Open Access Journals (Sweden)

    Randall Nicola P

    2012-05-01

    Full Text Available Abstract Background Agriculture is the dominant land use throughout much of Europe. Changes to farming practices have led to concerns about negative impacts on biodiversity, and current agricultural policy has an emphasis towards conservation. The objective of this study was to investigate and describe the nature and coverage of research pertaining to the effectiveness of integrated farm management, organic farming and agri-environment schemes as interventions for conserving biodiversity in temperate Europe. Systematic mapping methodology was adapted from social sciences, and used to create a searchable database of relevant research. Methods Searches were made of 10 electronic databases containing peer reviewed journals, PhD theses, conference proceedings and organisational reports. Web searches for relevant research were also made. The title and abstracts of results were examined for relevance. Studies were included when published in English, when an intervention was applied to increase biodiversity or species diversity on farmland, and where there was a measured effect on study organism(s. Correlative and manipulative studies from temperate Europe were included. The research was incorporated into a searchable database (systematic map and key wording used to describe, categorise and code studies. Results The searches identified 83,590 records. Following removal of duplicates and the application of inclusion criteria, 743 references were coded for the final systematic map database. Most of the studies reported were from Western Europe, particularly from the UK. Invertebrates were the most commonly studied organism followed by plants and birds, and field margins were the most commonly studied biotope. Conclusions The systematic map describes the scope of research on the topic. It can be used to inform future primary research, or research synthesis and evaluation methods such as systematic review. Areas for which there appear to be evidence gaps

  3. Finite-Difference Lattice Boltzmann Scheme for High-Speed Compressible Flow: Two-Dimensional Case

    Science.gov (United States)

    Gan, Yan-Biao; Xu, Ai-Guo; Zhang, Guang-Cai; Zhang, Ping; Zhang, Lei; Li, Ying-Jun

    2008-07-01

    Lattice Boltzmann (LB) modeling of high-speed compressible flows has long been attempted by various authors. One common weakness of most of previous models is the instability problem when the Mach number of the flow is large. In this paper we present a finite-difference LB model, which works for flows with flexible ratios of specific heats and a wide range of Mach number, from 0 to 30 or higher. Besides the discrete-velocity-model by Watari [Physica A 382 (2007) 502], a modified Lax Wendroff finite difference scheme and an artificial viscosity are introduced. The combination of the finite-difference scheme and the adding of artificial viscosity must find a balance of numerical stability versus accuracy. The proposed model is validated by recovering results of some well-known benchmark tests: shock tubes and shock reflections. The new model may be used to track shock waves and/or to study the non-equilibrium procedure in the transition between the regular and Mach reflections of shock waves, etc.

  4. Performance Analysis Of Active Queue Management AQM In VOIP Using Different Voice Encoder Scheme

    Directory of Open Access Journals (Sweden)

    Samir Eid Mohammed

    2015-08-01

    Full Text Available Abstract Voice over Internet Protocol VoIP is a rapidly growing technology that enables transport of voice over data networks such as Ethernet Wide area networks WANs due to this important different codec scheme is developed to meet the QoS requirements. This thesis presents a comprehensive study about the impact of active queue management AQM on Voice over Internet Protocol VoIP quality of service using different codec scheme such as G711 G723 G729 and GSM using simulations tools. The evaluation is done using the OPNET Modeler which provides a convenient and easy-to-use platform for simulating large scale networks and this also give a power to go through different levels of designing a network even with the ability to program the mechanism you want which is used here to implement two types of AQM mechanism which is not included by default in the OPNET and these two mechanisms are ARED and GRED. The performance metrics used in the study are jitter throughput and delay. The study shows that G.711 and G729 codecs in a simulation gives a significant result for the performance of VoIP that codec G711 and G.729A has acceptable throughput and less deviation of received to transmit packet as compared to GSM and G.723 also average delay like end to end delay and Voice jitter is lesser in codec G711 and G.729 as compared to the other two referenced codecs.

  5. The Moral Stereotypes of Liberals and Conservatives: Exaggeration of Differences across the Political Spectrum

    Science.gov (United States)

    Graham, Jesse; Nosek, Brian A.; Haidt, Jonathan

    2012-01-01

    We investigated the moral stereotypes political liberals and conservatives have of themselves and each other. In reality, liberals endorse the individual-focused moral concerns of compassion and fairness more than conservatives do, and conservatives endorse the group-focused moral concerns of ingroup loyalty, respect for authorities and traditions, and physical/spiritual purity more than liberals do. 2,212 U.S. participants filled out the Moral Foundations Questionnaire with their own answers, or as a typical liberal or conservative would answer. Across the political spectrum, moral stereotypes about “typical” liberals and conservatives correctly reflected the direction of actual differences in foundation endorsement but exaggerated the magnitude of these differences. Contrary to common theories of stereotyping, the moral stereotypes were not simple underestimations of the political outgroup's morality. Both liberals and conservatives exaggerated the ideological extremity of moral concerns for the ingroup as well as the outgroup. Liberals were least accurate about both groups. PMID:23251357

  6. The moral stereotypes of liberals and conservatives: exaggeration of differences across the political spectrum.

    Directory of Open Access Journals (Sweden)

    Jesse Graham

    Full Text Available We investigated the moral stereotypes political liberals and conservatives have of themselves and each other. In reality, liberals endorse the individual-focused moral concerns of compassion and fairness more than conservatives do, and conservatives endorse the group-focused moral concerns of ingroup loyalty, respect for authorities and traditions, and physical/spiritual purity more than liberals do. 2,212 U.S. participants filled out the Moral Foundations Questionnaire with their own answers, or as a typical liberal or conservative would answer. Across the political spectrum, moral stereotypes about "typical" liberals and conservatives correctly reflected the direction of actual differences in foundation endorsement but exaggerated the magnitude of these differences. Contrary to common theories of stereotyping, the moral stereotypes were not simple underestimations of the political outgroup's morality. Both liberals and conservatives exaggerated the ideological extremity of moral concerns for the ingroup as well as the outgroup. Liberals were least accurate about both groups.

  7. Properties of finite difference models of non-linear conservative oscillators

    Science.gov (United States)

    Mickens, R. E.

    1988-01-01

    Finite-difference (FD) approaches to the numerical solution of the differential equations describing the motion of a nonlinear conservative oscillator are investigated analytically. A generalized formulation of the Duffing and modified Duffing equations is derived and analyzed using several FD techniques, and it is concluded that, although it is always possible to contstruct FD models of conservative oscillators which are themselves conservative, caution is required to avoid numerical solutions which do not accurately reflect the properties of the original equation.

  8. Efficiency of High-Order Accurate Difference Schemes for the Korteweg-de Vries Equation

    Directory of Open Access Journals (Sweden)

    Kanyuta Poochinapan

    2014-01-01

    Full Text Available Two numerical models to obtain the solution of the KdV equation are proposed. Numerical tools, compact fourth-order and standard fourth-order finite difference techniques, are applied to the KdV equation. The fundamental conservative properties of the equation are preserved by the finite difference methods. Linear stability analysis of two methods is presented by the Von Neumann analysis. The new methods give second- and fourth-order accuracy in time and space, respectively. The numerical experiments show that the proposed methods improve the accuracy of the solution significantly.

  9. Comparison and Analysis of the Control Power Between Two Different Perfect Controlled Teleportation Schemes Using Four-particle Cluster State

    Science.gov (United States)

    Jiang, Yu-ting; Mo, Zhi-wen

    2017-07-01

    Control power is used to discuss about the controller's measurable authority. It's a new index to describe the controlled teleportation schemes from the point of view of the controller. In this paper, we introduce two perfect controlled teleportation schemes and calculate the control power under different control particles. In scheme 1, the controller just controls one particle, which is particle 2. And in scheme 2, the controller controls the particles 2 and 3. They both use the cluster state |ψ \\rangle _{1234}={1/2}(|0000\\rangle +|0011\\rangle +|1100\\rangle -|1111\\rangle )_{1234} as communication channel. By calculating the control power between two schemes, the control power of scheme 1 is 1/3, which is the minimal value of control power. On the contrary, the control power of scheme 2 is maximal, 1/2. Scheme 2 which controls two particles successfully promotes the control power comparing with scheme 1. It's evidently that controlling particle 2 is a necessary condition. And controlling particle 3 can gain the control power but the controller cannot control it solely.

  10. Difference schemes for fully nonlinear pseudo-parabolic systems with two space dimensions

    Institute of Scientific and Technical Information of China (English)

    周毓麟; 袁光伟

    1996-01-01

    The first boundary value problem for the fully nonlinear pseudoparabolic systems of partial differential equations with two space dimensions by the finite difference method is studied. The existence and uniqueness of the discrete vector solutions for the difference systems are established by the fixed point technique. The stability and convergence of the discrete vector solutions of the difference schemes to the vector solutions of the original boundary problem of the fully nonlinear pseudo-parabolic system are obtained by way of a priori estimation. Here the unique smooth vector solution of the original problems for the fully nonlinear pseudo-parabolic system is assumed. Moreover, by the method used here, it can be proved that analogous results hold for fully nonlinear pseudo-parabolic system with three space dimensions, and improve the known results in the case of one space dimension.

  11. Integrating different understandings of landscape stewardship into the design of agri-environmental schemes

    DEFF Research Database (Denmark)

    Raymond, Christopher Mark; Reed, Mark; Bieling, Claudia

    2016-01-01

    While multiple studies have identified land managers’ preferences for agri-environmental schemes (AES), few approaches exist for integrating different understandings of landscape stewardship into the design of these measures. We compared and contrasted rural land managers’ attitudes toward AES...... in preferences for AES design beyond 2020. We adapted a collaborative and coordinated approach for designing AES to account for the differing interests of land managers based on their understanding of landscape stewardship. We discuss the implications of this approach for environmental policy design...... and their preferences for AES design beyond 2020 across different understandings of landscape stewardship. Forty semi-structured interviews were conducted with similar proportions of small holders, medium holders and large holders in southwest Devon, UK. Overall, respondents most frequently cited concerns related...

  12. Partially implicit finite difference scheme for calculating dynamic pressure in a terrain-following coordinate non-hydrostatic ocean model

    Science.gov (United States)

    Liu, Zhe; Lin, Lei; Xie, Lian; Gao, Huiwang

    2016-10-01

    To improve the efficiency of the terrain-following σ-coordinate non-hydrostatic ocean model, a partially implicit finite difference (PIFD) scheme is proposed. By using explicit terms instead of implicit terms to discretize the parts of the vertical dynamic pressure gradient derived from the σ-coordinate transformation, the coefficient matrix of the discrete Poisson equation that the dynamic pressure satisfies can be simplified from 15 diagonals to 7 diagonals. The PIFD scheme is shown to run stably when it is applied to simulate five benchmark cases, namely, a standing wave in a basin, a surface solitary wave, a lock-exchange problem, a periodic wave over a bar and a tidally induced internal wave. Compared with the conventional fully implicit finite difference (FIFD) scheme, the PIFD scheme produces simulation results of equivalent accuracy at only 40-60% of the computational cost. The PIFD scheme demonstrates strong applicability and can be easily implemented in σ-coordinate ocean models.

  13. Three-point explicit compact difference scheme with arbitrary order of accuracy and its application in CFD

    Institute of Scientific and Technical Information of China (English)

    LIN Jian-guo; XIE Zhi-hua; ZHOU Jun-tao

    2007-01-01

    Based on the successive iteration in the Taylor series expansion method, a three-point explicit compact difference scheme with arbitrary order of accuracy is derived in this paper. Numerical characteristics of the scheme are studied by the Fourier analysis.Unlike the conventional compact difference schemes which need to solve the equation to obtain the unknown derivatives in each node, the proposed scheme is explicit and can achieve arbitrary order of accuracy in space. Application examples for the convectiondiffusion problem with a sharp front gradient and the typical lid-driven cavity flow are given. It is found that the proposed compact scheme is not only simple to implement and economical to use, but also is effective to simulate the convection-dominated problem and obtain high-order accurate solution in coarse grid systems.

  14. DNS of Sheared Particulate Flows with a 3D Explicit Finite-Difference Scheme

    Science.gov (United States)

    Perrin, Andrew; Hu, Howard

    2007-11-01

    A 3D explicit finite-difference code for direct simulation of the motion of solid particulates in fluids has been developed, and a periodic boundary condition implemented to study the effective viscosity of suspensions in shear. The code enforces the no-slip condition on the surface of spherical particles in a uniform Cartesian grid with a special particle boundary condition based on matching the Stokes flow solutions next to the particle surface with a numerical solution away from it. The method proceeds by approximating the flow next to the particle surface as a Stokes flow in the particle's local coordinates, which is then matched to the finite difference update in the bulk fluid on a ``cage'' of grid points near the particle surface. (The boundary condition is related to the PHYSALIS method (2003), but modified for explicit schemes and with an iterative process removed.) Advantages of the method include superior accuracy of the scheme on a relatively coarse grid for intermediate particle Reynolds numbers, ease of implementation, and the elimination of the need to track the particle surface. For the sheared suspension, the effects of fluid and solid inertia and solid volume fraction on effective viscosity at moderate particle Reynolds numbers and concentrated suspensions will be discussed.

  15. Games on graphs: A minor modification of payoff scheme makes a big difference

    CERN Document Server

    Zhang, Qiang; Di, Zengru; Wu, Jinshan

    2013-01-01

    Various social dilemma games that follow different strategy updating rules have been studied on many networks.The reported results span the entire spectrum, from significantly boosting,to marginally affecting,to seriously decreasing the level of cooperation.Experimental results that are qualitatively different from theoretical prediction have also been reported.It is widely believed that the results are largely determined by three elements,including payoff matrices of the underlying 2*2 games,the way that the strategic states of the players are updated and the structure of the networks.Here we discuss the impact of a seemly non-essential mechanism -- what we refer to as a "payoff scheme". Specifically, in each round after the states of all of the players are determined,the payoff scheme is how each player's payoff is calculated.In addition to the two conventions in which either the accumulated or the averaged payoff is calculated from playing with all of the neighboring players,we here study the effects of ca...

  16. The performance of different cumulus parameterization schemes in simulating the 2006/2007 southern peninsular Malaysia heavy rainfall episodes

    Indian Academy of Sciences (India)

    Wan Ahmad Ardie; Khai Shen Sow; Fredolin T Tangang; Abdul Ghapor Hussin; Mastura Mahmud; Liew Juneng

    2012-04-01

    The performance of four different cumulus parameterization schemes (CPS) in the Weather Research and Forecasting (WRF) model for simulating three heavy rainfall episodes over the southern peninsular Malaysia during the winter monsoon of 2006/2007 were examined. The modelled rainfall was compared with the 3-hourly satellite observation and objectively scored using a verification technique called the acuity–fidelity. The technique is based on minimization of a cost function that is calculated from four parameters taking into account errors in distance, time, intensity, and missed events. All simulations were made for 72 hours for the three episodes starting at 1200 UTC 17 December 2006, 1200 UTC 24 December 2006 and 1200 UTC 11 January 2007, respectively. The four different CPSs used are the new Kain–Fritsch scheme (KF2), the Betts–Miller–Janjic scheme (BMJ), the Grell–Devenyi ensemble scheme (GD) and the older Kain–Fritsch scheme (KF1). While the BMJ scheme shows some success in the second and third episodes, it shows high location errors in the first episode, leading to high acuity errors. The GD, KF2 and KF1 schemes performed poorly, although both the BMJ and GD schemes simulated the observed drastic increase of rainfall at 2100 UTC 18 December 2006 during the first episode. Overall, the KF1 and KF2 schemes produced positive biases in terms of coverage, while the GD scheme showed persistent location bias, producing a scattered line of precipitation over the eastern coastline of peninsular Malaysia. Although the BMJ scheme has better results, its poor performance for the first episode suggests that suitability of CPS may be case dependent.

  17. Market-based mechanisms for biodiversity conservation: a review of existing schemes and an outline for a global mechanism

    NARCIS (Netherlands)

    Alvarado Quesada, I.; Hein, L.G.; Weikard, H.P.

    2014-01-01

    Continuous decline of biodiversity over the past decades suggests that efforts to decrease biodiversity loss have been insufficient. One option to deal with this problem is the use of market-based mechanisms for biodiversity conservation. Several studies have analysed such mechanisms individually,

  18. Piagetian Conservation Tasks in Ghanaian Children: the Role of Geographical Location, Gender and Age Differences

    Directory of Open Access Journals (Sweden)

    Evelyn AmaAssan

    2015-06-01

    Full Text Available The study investigated the influence of geographical location, gender and age on the performance of Piagetian Conservation tasks. Four conservation tasks; conservation of liquid, length, substance amount and number respectively were administered to children [4-6 years] from rural and urban Ghana and their performance on each task were recorded. Results indicated that there were no significant relationships among the performance of Piagetian conservation tasks and geographical location. Similar trends were noted in the performance of gender and age differences on Piagetian conservation tasks. Nonetheless, older children performed better on the conservation of liquid in a glass than younger children. Based on the results, both quantities and perceptual comparisons can be applied in future studies to examine some possible variations in children’s cognitive development.

  19. Finite difference schemes for the singularly perturbed reaction-diffusion equation in the case of spherical symmetry

    Science.gov (United States)

    Shishkin, G. I.; Shishkina, L. P.

    2009-05-01

    The boundary value problem for the singularly perturbed reaction-diffusion parabolic equation in a ball in the case of spherical symmetry is considered. The derivatives with respect to the radial variable appearing in the equation are written in divergent form. The third kind boundary condition, which admits the Dirichlet and Neumann conditions, is specified on the boundary of the domain. The Laplace operator in the differential equation involves a perturbation parameter ɛ2, where ɛ takes arbitrary values in the half-open interval (0, 1]. When ɛ → 0, the solution of such a problem has a parabolic boundary layer in a neighborhood of the boundary. Using the integro-interpolational method and the condensing grid technique, conservative finite difference schemes on flux grids are constructed that converge ɛ-uniformly at a rate of O( N -2ln2 N + N {0/-1}), where N + 1 and N 0 + 1 are the numbers of the mesh points in the radial and time variables, respectively.

  20. Understanding the effects of different social data on selecting priority conservation areas.

    Science.gov (United States)

    Karimi, Azadeh; Tulloch, Ayesha I T; Brown, Greg; Hockings, Marc

    2017-04-20

    Conservation success is contingent on assessing social and environmental factors so that cost-effective implementation of strategies and actions can be placed in a broad social-ecological context. Until now, the focus has been on how to include spatially explicit social data in conservation planning, whereas the value of different kinds of social data has received limited attention. In a regional systematic conservation planning case study in Australia, we examined the spatial concurrence of a range of spatially explicit social values and land-use preferences collected using a public participation geographic information system and biological data. We used Zonation to integrate the social data with the biological data in a series of spatial-prioritization scenarios to determine the effect of the different types of social data on spatial prioritization compared with biological data alone. The type of social data (i.e., conservation opportunities or constraints) significantly affected spatial prioritization outcomes. The integration of social values and land-use preferences under different scenarios was highly variable and generated spatial prioritizations 1.2-51% different from those based on biological data alone. The inclusion of conservation-compatible values and preferences added relatively few new areas to conservation priorities, whereas including noncompatible economic values and development preferences as costs significantly changed conservation priority areas (48.2% and 47.4%, respectively). Based on our results, a multifaceted conservation prioritization approach that combines spatially explicit social data with biological data can help conservation planners identify the type of social data to collect for more effective and feasible conservation actions. © 2017 Society for Conservation Biology.

  1. Dynamic Change of Genetic Diversity in Conserved Populations with Different Initial Genetic Architectures

    Institute of Scientific and Technical Information of China (English)

    LU Yun-feng; LI Hong-wei; WU Ke-liang; WU Chang-xin

    2013-01-01

    in a closed conserved population. Our study suggested that current managements of conserved populations should emphasize on initial genetic architecture in order to make an effective and feasible conservation scheme.

  2. High-Dose-Rate Brachytherapy Boost for Prostate Cancer: Comparison of Two Different Fractionation Schemes

    Energy Technology Data Exchange (ETDEWEB)

    Kaprealian, Tania [Department of Radiation Oncology, University of California, San Francisco Helen Diller Family Comprehensive Cancer Center, San Francisco, California (United States); Weinberg, Vivian [Biostatistics and Computational Biology Core, University of California, San Francisco Helen Diller Family Comprehensive Cancer Center, San Francisco, California (United States); Speight, Joycelyn L. [Department of Radiation Oncology, University of California, San Francisco Helen Diller Family Comprehensive Cancer Center, San Francisco, California (United States); Department of Urology, University of California, San Francisco Helen Diller Family Comprehensive Cancer Center, San Francisco, California (United States); Gottschalk, Alexander R. [Department of Radiation Oncology, University of California, San Francisco Helen Diller Family Comprehensive Cancer Center, San Francisco, California (United States); Roach, Mack [Department of Radiation Oncology, University of California, San Francisco Helen Diller Family Comprehensive Cancer Center, San Francisco, California (United States); Department of Urology, University of California, San Francisco Helen Diller Family Comprehensive Cancer Center, San Francisco, California (United States); Shinohara, Katsuto [Department of Urology, University of California, San Francisco Helen Diller Family Comprehensive Cancer Center, San Francisco, California (United States); Hsu, I.-Chow, E-mail: IHsu@radonc.ucsf.edu [Department of Radiation Oncology, University of California, San Francisco Helen Diller Family Comprehensive Cancer Center, San Francisco, California (United States)

    2012-01-01

    Purpose: This is a retrospective study comparing our experience with high-dose-rate (HDR) brachytherapy boost for prostate cancer, using two different fractionation schemes, 600 cGy Multiplication-Sign 3 fractions (patient group 1) and 950 cGy Multiplication-Sign 2 fractions (patient group 2). Methods and Materials: A total of 165 patients were treated for prostate cancer using external beam radiation therapy up to a dose of 45 Gy, followed by an HDR brachytherapy prostate radiation boost. Between July 1997 and Nov 1999, 64 patients were treated with an HDR boost of 600 cGy Multiplication-Sign 3 fractions; and between June 2000 and Nov 2005, 101 patients were treated with an HDR boost of 950 cGy Multiplication-Sign 2 fractions. All but 9 patients had at least one of the following risk features: pretreatment prostate-specific antigen (PSA) level >10, a Gleason score {>=}7, and/or clinical stage T3 disease. Results: Median follow-up was 105 months for group 1 and 43 months for group 2. Patients in group 2 had a greater number of high-risk features than group 1 (p = 0.02). Adjusted for comparable follow-up, there was no difference in biochemical no-evidence-of-disease (bNED) rate between the two fractionation scheme approaches, with 5-year Kaplan-Meier estimates of 93.5% in group 1 and 87.3% in group 2 (p = 0.19). The 5-year estimates of progression-free survival were 86% for group 1 and 83% for group 2 (p = 0.53). Among high-risk patients, there were no differences in bNED or PFS rate due to fractionation. Conclusions: Results were excellent for both groups. Adjusted for comparable follow-up, no differences were found between groups.

  3. Soil quality under two different management schemes in coffee plantations of southern Colombia.

    Directory of Open Access Journals (Sweden)

    Oscar Eduardo Valbuena-Calderón

    2016-12-01

    Full Text Available The aim of this work was to develop an additive soil quality index (ASQI in agrofostery managements of coffee (Coffea arabica L.. The study took place under two intense and traditional management schemes, in nine farms (32 lots in the south of Colombia, during 2013. A separation of means analysis was held through the LSD Fisher test (P<0,05 to each of the physical and chemical variables of the soil. The variables that showed differences between the schemes were submitted to a main components analysis to select the minimum data set (MDS of the components that explained the most variability and the redundancy was veri ed within the indicators, based on the correlation. The ASQI was obtained from the total sum of soil quality index (SQI of all the indicators, taking into account that the higher the score of the ASQI, the higher the quality of the soil within the study system. The selected physical variables were the content of sand and clay; while the chemical variables were: organic carbon (OC, P, CA, Mg, total bases (TB and Ca/Mg. The best ASQI was obtained from traditional management, because the value of the selected variables matched in a bigger proportion with the quality objective identi ed for the ASQI quanti cation; in this case the crop yield, based on limit values for coffee plantations.

  4. A preliminary study of 3D difference scheme with energy dynamic equilibrium

    Institute of Scientific and Technical Information of China (English)

    Chiping Wu; Yongxing Zhang; Zhongzhen Ji; Wenxing Sun; Zede Guo; Weiping Jin

    2005-01-01

    In this paper, a difference scheme with energy dynamic equilibrium (DS-EDE) is presented, which can be used for the simulation of long-term atmosphere and sea motion.Based on three dimensional nonlinear evolution equations for atmosphere and sea motion, a three dimensional compact upwind scheme (CUWS) is constructed, as the basis of the DS-EDE. The DS-EDE satisfies the following condition of energy dynamic equilibrium (EDE): the total work of exter nal forces on the region boundary is equal to the sum of the total effective variation of the kinetic energy and the energy dissipation in the average flow motion and the effective variation of the potential energy per unit time within the region of interest. It really reflects the basic mechanism of the action of external forces and dissipation in atmosphere and sea movement. Therefore, the DS-EDE developed in this paper is a suitable model for simulating long-term atmosphere and sea movement with forcing and dissipation.

  5. A new compact difference scheme for second derivative in non-uniform grid expressed in self-adjoint form

    Science.gov (United States)

    Sengupta, T. K.; Bhaumik, S.; Shameem, U.

    2011-03-01

    A single-parameter family of self-adjoint compact difference (SACD) schemes is developed for discretizing the Laplacian operator in self-adjoint form. Developed implicit scheme is formally second-order accurate (with respect to truncation error) with a free parameter, α which helps control the numerical properties in the spectral plane. The SACD scheme is analyzed in the spectral plane for its resolution properties for both periodic and non-periodic problems using the matrix spectral analysis [T.K. Sengupta, G. Ganeriwal, S. De, Analysis of central and upwind schemes, J. Comput. Phys. 192 (2) (2003) 677-694]. The major objective here is to identify the advantages of the new scheme over the traditional explicit second order CD2 scheme, in discretizing the Laplacian operator in self-adjoint form. This appears in Navier-Stokes equation and in other transport equations and boundary value problems (bvp) expressed in orthogonal co-ordinate systems, either in physical or in transformed plane. We also compare the developed method with the higher order compact schemes for non-uniform grids. To demonstrate the accuracy of SACD scheme we have tested it for: (i) bi-directional wave propagation problem, given by the second order wave equation and (ii) an elliptic bvp, as in the Stommel ocean model for the stream function. These examples help infer the properties of SACD scheme when solving different types of partial differential equations. Most importantly the effects of grid-stretching and choice of value of the free parameter ( α) are investigated here. We also compare the present implicit compact method with explicit compact method known as the higher order compact (HOC) method. Also, the practical applications of the SACD scheme are explored by solving the Navier-Stokes equation for the cases of: (a) a flow inside a lid-driven cavity and (b) the receptivity and instability of an external adverse pressure gradient flow over a flat plate. In the former, unsteadiness of the

  6. Regional Differences in China's Energy Efficiency and Conservation Potentials

    Institute of Scientific and Technical Information of China (English)

    Shi Dan

    2007-01-01

    This paper investigates the maximum energy efficiency level and the energy saving potentials in each region in China that can be practically attained at current economic and technological development levels. Most of the nation's energy efficient provinces are found along the coast of southeast China, while most of its least energy efficient provinces are in the hinterland that is rich in coal resources, and which depends heavily on coal consumption. China's low efficiency in energy resource allocation stems from its secondary industry, which is handicapped by the lowest energy efficiency and the most striking regional differentials. 4comparison of the factors affecting the energy efficiency shows that the provinces being compared in this study differ tremendously in energy consumption structure, technological level of the secondary industry, and abundance of energy resources, and that the other factors are only adequate, rather than necessary, conditions. It is imperative to rectify the behaviors of provinces in balancing local energy allocation, to channel energy resources to energy efficient provinces, and to improve the national energy efficiency as a whole. When taking energy-saving steps, provinces must take into full consideration both the national and local factors that affect energy efficiency. Furthermore, it is unrealistic for China to set a unified energy saving goal for different provinces.

  7. A novel frequency control scheme for comb-referenced sensitive difference-frequency-generation spectroscopy.

    Science.gov (United States)

    Iwakuni, Kana; Okubo, Sho; Sasada, Hiroyuki

    2013-06-17

    We present a novel scheme of frequency scan and wavelength modulation of a difference-frequency-generation source for comb-referenced sensitive spectroscopy. While the pump and signal frequencies are phase-locked to an optical frequency comb (OFC), the offset frequency between the signal wave and the nearest comb tooth is modulated to apply a wavelength-modulation technique, and the idler wave frequency is repeatedly swept for signal accumulation by changing the repetition frequency of the OFC. The spectrometer is applied to absolute frequency measurement of weak hyperfine-resolved rovibration transitions of the ν(1) band of CH(3)I, and the uncertainty in frequency determination is reduced by one order of magnitude in compared with that of the previous work published in Optics Express 20, 9178-9186 (2012).

  8. Finite Difference Approach for Estimating the Thermal Conductivity by 6-point Crank-Nicolson Scheme

    Institute of Scientific and Technical Information of China (English)

    SU Ya-xin; YANG Xiang-xiang

    2005-01-01

    Based on inverse heat conduction theory, a theoretical model using 6-point Crank-Nicolson finite difference scheme was used to calculate the thermal conductivity from temperature distribution, which can be measured experimentally. The method is a direct approach of second-order and the key advantage of the present method is that it is not required a priori knowledge of the functional form of the unknown thermal conductivity in the calculation and the thermal parameters are estimated only according to the known temperature distribution. Two cases were numerically calculated and the influence of experimental deviation on the precision of this method was discussed. The comparison of numerical and analytical results showed good agreement.

  9. A New Steganography Technique Based on Difference Scheme of RGB Channels and Text Using Histogram Analysis

    Directory of Open Access Journals (Sweden)

    Manoj Kumar Sharma,

    2014-05-01

    Full Text Available Steganography is the art of hiding the fact that communication is taking place, by hiding information in other information. The motivation for this work includes provision of protection of information during transmission without any detection of information. We also propose a new technique namely „A New Steganography Technique Based on Difference Scheme of RGB Channels and Text Using Histogram Analysis‟. The proposed technique can encode any colored image files in order to protect confidential text data from unauthorized access. It can be applied to a very small images (24 × 24 as well as large images (1024 × 1024. We use Image quality parameters Peak Signal to Noise Ratio and Mean Square Error. The proposed method has higher PSNR value and lower MSE values. The PSNR value is greater than 50 and MSE value is in fractions.

  10. Several teleportation schemes of an arbitrary unknown multi-particle state via different quantum channels

    Institute of Scientific and Technical Information of China (English)

    Peng Jia-Yin; Mo Zhi-Wen

    2013-01-01

    We first provide four new schemes for two-party quantum teleportation of an arbitrary unknown multi-particle state by using three-,four-,and five-particle states as the quantum channel,respectively.The successful probability and fidelity of the four schemes reach 1.In the first two schemes,the receiver can only apply one of the unitary transformations to reconstruct the original state,making it easier for these two schemes to be directly realized.In the third and fourth schemes,the sender can preform Bell-state measurements instead of multipartite entanglement measurements of the existing similar schemes,which makes real experiments more suitable.It is found that the last three schemes may become tripartite controlled teleportation schemes of teleporting an arbitrary multi-particle state after a simple modification.Finally,we present a new scheme for three-party sharing an arbitrary unknown multi-particle state.In this scheme,the sender first shares three three-particle GHZ states with two agents.After setting up the secure quantum channel,an arbitrary unknown multi-particle state can be perfectly teleported if the sender performs three Bell-state measurements,and either of two receivers operates an appropriate unitary transformation to obtain the original state with the help of other receiver's three single-particle measurements.The successful probability and fidelity of this scheme also reach 1.It is demonstrated that this scheme can be generalized easily to the case of sharing an arbitrary unknown multi-particle state among several agents.

  11. Evolutions of microbial degradation pathways for parent xenobiotic and for its metabolites follow different schemes.

    Science.gov (United States)

    Chong, Nyuk-Min; Chang, Chun-Shuo; Tsai, Shiu-Ching

    2012-09-01

    The pathways used by microorganisms for the metabolism of every xenobiotic substrate are specific. The catabolism of a xenobiotic goes through a series of intermediate steps and lower intermediates (metabolites) appear in sequence. The structure of the metabolites can be similar to the parents due to kinship. The purposes of this study were to examine if the degradation pathways that were developed for a parent xenobiotic are effective to degrade the parent's lower metabolites, and if the reverse is true. The xenobiotic substrates, 2,4-dichlorophenoxyacetic acid (2,4-D, the parent xenobiotic) and its metabolite 2,4-dichlorophenol (2,4-DCP), were independently subjected to acclimation and degradation tests by the biomasses of mixed-culture activated sludge and a pure culture of Arthrobacter sp. Activated sludge and Arthrobacter sp. that were acclimated to 2,4-D effectively degraded 2,4-D and the lower metabolites of 2,4-D, typically 2,4-DCP. During the degradation of 2,4-D, accumulations of the lower metabolites of 2,4-D were not found. The degradation pathways acquired from acclimation to 2,4-D are effective for all the metabolites of 2,4-D. However, pathways acquired from acclimation to 2,4-DCP are not effective in the degradation of the parent 2,4-D. Microorganisms acclimated to 2,4-D evolve their degradation pathways by a scheme that is different from the scheme the microorganisms employ when they are acclimated to the metabolites of 2,4-D.

  12. Adequacy of genetic evaluation of dairy cows for milk yield using different testing schemes

    Directory of Open Access Journals (Sweden)

    Giovanni Bittante

    2010-01-01

    Full Text Available Alternative milk recording schemes, as alternate a.m.-p.m. (AT procedures, have been proposed in order to reducerecording costs per cow thereby increasing the number of cows and young bulls that can be tested. The objective of thispaper is to compare predicted breeding values using alternative recording schemes for estimating lactation yields, specificallyfor dams of sires. Over 4 million test day records for milk yield of 306,148 Italian Friesian cows collected in 649herds in the province of Milan (Italy between 1990 and 1997 were used. The simulation of alternative testing schemeswas carried out using A4 single milking data. The alternative schemes to estimate daily milk yield from AM and PM data,were: a alternate scheme using a doubling; b alternate scheme using a correction for milking interval applying (MIdirect or inverse factors; c non-alternate scheme using a correction for MI applying inverse factors; d random schemeusing a correction for MI applying inverse factors. A mixed model procedure to estimate breeding values was used. Therank correlation between EBV with A4 method and other testing schemes resulted around 99% at the population leveland around 89% with regard to the top 1% of cows. About 10% of cows ranked with A4 method were excluded from thelist of the top 1% when alternative testing schemes were applied. A negligible effect on the reduction of selection intensityfor the dams of sires path was found.

  13. The ecological effectiveness of agri-environment schemes in different agricultural landscapes in The Netherlands

    NARCIS (Netherlands)

    Kleijn, D.; Berendse, F.; Smit, R.; Gilissen, N.; Smit, J.; Brak, B.; Groeneveld, R.A.

    2004-01-01

    Agri-environment schemes are an instrument used by western European countries to counteract the negative effects of contemporary agriculture on biodiversity, but not much is known about their effectiveness. We investigated the ecological effects of Dutch agri-environment schemes aimed at promoting b

  14. The ecological effectiveness of agri-environment schemes in different agricultural landscapes in The Netherlands

    NARCIS (Netherlands)

    Kleijn, D.; Berendse, F.; Smit, R.; Gilissen, N.; Smit, J.; Brak, B.; Groeneveld, R.A.

    2004-01-01

    Agri-environment schemes are an instrument used by western European countries to counteract the negative effects of contemporary agriculture on biodiversity, but not much is known about their effectiveness. We investigated the ecological effects of Dutch agri-environment schemes aimed at promoting

  15. The Use of Ecological Indicators as a Basis for Operationalizing a PES Scheme on Forest Conservation in Northern Argentina

    Science.gov (United States)

    Gobbi, José; Deguillon, Marie

    2017-04-01

    Payments for ecosystem services (PES) aim to improve the supply of ecosystem services (ES) by making payments to service providers, which are conditional on the provision of those services. Payments cannot be conditional unless the service can be effectively monitored. Direct monitoring of ES to assess conditionality could be methodologically complex and operatively expensive. To overcome such constraints, the pilot "GEF-PES Project" of Northern Argentina has developed a set of five indicators on forest conservation status (CS) as a basis for estimating the amount of ES provided -considering a positive correlation between the CS of a forest and its level of provision of ecosystem services -and for operationalizing the PES. Field data indicate that selected indicators: (i) exhibit strong correlation with the amount of carbon and biodiversity provided by forests according to their CS, ii) are cost-effective to monitor ES conditionality and (iii) allow easy application of payment levels.

  16. Daily Evaporative Fraction Parameterization Scheme Driven by Day–Night Differences in Surface Parameters: Improvement and Validation

    Directory of Open Access Journals (Sweden)

    Jing Lu

    2014-05-01

    Full Text Available In a previous study, a daily evaporative fraction (EF parameterization scheme was derived based on day–night differences in surface temperature, air temperature, and net radiation. Considering the advantage that incoming solar radiation can be readily retrieved from remotely sensed data in comparison with surface net radiation, this study simplified the daily EF parameterization scheme using incoming solar radiation as an input. Daily EF estimates from the simplified scheme were nearly equivalent to the results from the original scheme. In situ measurements from six Ameriflux sites with different land covers were used to validate the new simplified EF parameterization scheme. Results showed that daily EF estimates for clear skies were consistent with the in situ EF corrected by the residual energy method, showing a coefficient of determination of 0.586 and a root mean square error of 0.152. Similar results were also obtained for partly clear sky conditions. The non-closure of the measured energy and heat fluxes and the uncertainty in determining fractional vegetation cover were likely to cause discrepancies in estimated daily EF and measured counterparts. The daily EF estimates of different land covers indicate that the constant coefficients in the simplified EF parameterization scheme are not strongly site-specific.

  17. A remark on the GNSS single difference model with common clock scheme for attitude determination

    Science.gov (United States)

    Chen, Wantong

    2016-09-01

    GNSS-based attitude determination technique is an important field of study, in which two schemes can be used to construct the actual system: the common clock scheme and the non-common clock scheme. Compared with the non-common clock scheme, the common clock scheme can strongly improve both the reliability and the accuracy. However, in order to gain these advantages, specific care must be taken in the implementation. The cares are thus discussed, based on the generating technique of carrier phase measurement in GNSS receivers. A qualitative assessment of potential phase bias contributes is also carried out. Possible technical difficulties are pointed out for the development of single-board multi-antenna GNSS attitude systems with a common clock.

  18. Conservation presence, not socioeconomics, leads to differences in pastoralist perceived threats to argali

    Directory of Open Access Journals (Sweden)

    Wesley M. Sarmento

    2016-09-01

    Full Text Available Community-based conservation approaches that keep people on landscapes increasingly complement preservationist models of reserves without people. Evaluations of community conservation have shown that economic incentives and socioeconomics primarily drive people’s attitudes and perceptions. Work at Mongolia’s Ikh Nart Nature Reserve demonstrates how to achieve successful conservation by integrating local people into the overall program. Using a short questionnaire, we interviewed pastoralist families across two soums (similar to a U.S. county in Ikh Nart. We examined (1 pastoralists’ perceived threats to argali sheep (Ovis ammon, (2 socioeconomic differences among pastoralists, and (3 differences between pastoralists from different soums. We found that 15 years of conservation activities—education, research, and modest ecotourism—that occurred in the northern soum led to influences on people’s perceptions toward argali conservation. Compared with pastoralists from southern Ikh Nart, pastoralists from the northern part of the reserve more likely knew that argali are protected and understood primary threats to the species. Socioeconomic factors, such as age, sex, and wealth, did not significantly influence responses. The negligible economic incentives in Ikh Nart did not lead to response differences. Our results demonstrate that conservation can influence people across socioeconomic classes without providing large economic incentives.

  19. A High Order Finite Difference Scheme with Sharp Shock Resolution for the Euler Equations

    Science.gov (United States)

    Gerritsen, Margot; Olsson, Pelle

    1996-01-01

    We derive a high-order finite difference scheme for the Euler equations that satisfies a semi-discrete energy estimate, and present an efficient strategy for the treatment of discontinuities that leads to sharp shock resolution. The formulation of the semi-discrete energy estimate is based on a symmetrization of the Euler equations that preserves the homogeneity of the flux vector, a canonical splitting of the flux derivative vector, and the use of difference operators that satisfy a discrete analogue to the integration by parts procedure used in the continuous energy estimate. Around discontinuities or sharp gradients, refined grids are created on which the discrete equations are solved after adding a newly constructed artificial viscosity. The positioning of the sub-grids and computation of the viscosity are aided by a detection algorithm which is based on a multi-scale wavelet analysis of the pressure grid function. The wavelet theory provides easy to implement mathematical criteria to detect discontinuities, sharp gradients and spurious oscillations quickly and efficiently.

  20. ANALYSIS OF FINITE-DIFFERENCE SCHEMES BASED ON EXACT AND APPROXIMATE SOLUTION OF RIEMANN PROBLEM

    Directory of Open Access Journals (Sweden)

    P. V. Bulat

    2015-01-01

    Full Text Available The Riemann problem of one-dimensional arbitrary discontinuity breakdown for parameters of unsteady gas flow is considered as applied to the design of Godunov-type numerical methods. The problem is solved in exact and approximate statements (Osher-Solomon difference scheme used in shock capturing numerical methods: the intensities (the ratio of static pressures and flow velocities on the sides of the resulting breakdowns and waves are determined, and then the other parameters are calculated in all regions of the flow. Comparison of calculation results for model flows by exact and approximate solutions is performed. The concept of velocity function is introduced. The dependence of the velocity function on the breakdown intensity is investigated. A special intensity at which isentropic wave creates the same flow rate as the shock wave is discovered. In the vicinity of this singular intensity approximate methods provide the highest accuracy. The domain of applicability for the approximate Osher-Solomon solution is defined by performing test calculations. The results are presented in a form suitable for usage in the numerical methods. The results obtained can be used in the high-resolution numerical methods.

  1. Optimal fourth-order staggered-grid finite-difference scheme for 3D frequency-domain viscoelastic wave modeling

    Science.gov (United States)

    Li, Y.; Han, B.; Métivier, L.; Brossier, R.

    2016-09-01

    We investigate an optimal fourth-order staggered-grid finite-difference scheme for 3D frequency-domain viscoelastic wave modeling. An anti-lumped mass strategy is incorporated to minimize the numerical dispersion. The optimal finite-difference coefficients and the mass weighting coefficients are obtained by minimizing the misfit between the normalized phase velocities and the unity. An iterative damped least-squares method, the Levenberg-Marquardt algorithm, is utilized for the optimization. Dispersion analysis shows that the optimal fourth-order scheme presents less grid dispersion and anisotropy than the conventional fourth-order scheme with respect to different Poisson's ratios. Moreover, only 3.7 grid-points per minimum shear wavelength are required to keep the error of the group velocities below 1%. The memory cost is then greatly reduced due to a coarser sampling. A parallel iterative method named CARP-CG is used to solve the large ill-conditioned linear system for the frequency-domain modeling. Validations are conducted with respect to both the analytic viscoacoustic and viscoelastic solutions. Compared with the conventional fourth-order scheme, the optimal scheme generates wavefields having smaller error under the same discretization setups. Profiles of the wavefields are presented to confirm better agreement between the optimal results and the analytic solutions.

  2. Three-dimensional ultrasonic imaging of concrete elements using different SAFT data acquisition and processing schemes

    Science.gov (United States)

    Schickert, Martin

    2015-03-01

    Ultrasonic testing systems using transducer arrays and the SAFT (Synthetic Aperture Focusing Technique) reconstruction allow for imaging the internal structure of concrete elements. At one-sided access, three-dimensional representations of the concrete volume can be reconstructed in relatively great detail, permitting to detect and localize objects such as construction elements, built-in components, and flaws. Different SAFT data acquisition and processing schemes can be utilized which differ in terms of the measuring and computational effort and the reconstruction result. In this contribution, two methods are compared with respect to their principle of operation and their imaging characteristics. The first method is the conventional single-channel SAFT algorithm which is implemented using a virtual transducer that is moved within a transducer array by electronic switching. The second method is the Combinational SAFT algorithm (C-SAFT), also named Sampling Phased Array (SPA) or Full Matrix Capture/Total Focusing Method (TFM/FMC), which is realized using a combination of virtual transducers within a transducer array. Five variants of these two methods are compared by means of measurements obtained at test specimens containing objects typical of concrete elements. The automated SAFT imaging system FLEXUS is used for the measurements which includes a three-axis scanner with a 1.0 m × 0.8 m scan range and an electronically switched ultrasonic array consisting of 48 transducers in 16 groups. On the basis of two-dimensional and three-dimensional reconstructed images, qualitative and some quantitative results of the parameters image resolution, signal-to-noise ratio, measurement time, and computational effort are discussed in view of application characteristics of the SAFT variants.

  3. Evaluation of Polar WRF for different Planetary Boundary Layer schemes over Svalbard

    Science.gov (United States)

    Czernecki, Bartosz; Kryza, Maciej; Migała, Krzysztof; Kolendowicz, Leszek

    2016-04-01

    High frequency of stable atmospheric conditions in Polar regions makes it a very challenging region to accurately downscale local meteorological phenomena. Keeping that in mind authors decided to evaluate the robustness of dynamical downscaling techniques with the use of the Polar Weather Research and Forecasting (Polar WRF) model version 3.7.1 for the area of Svalbard. The Weather Research and Forecasting (WRF) model is often used as a tool for dynamical downscaling. However, its application for relatively complex topography in polar regions like over the area of investigation are sparse. This study introduces some preliminary results of the research project, funded by the Polish National Science Centre, focused on application of the Polar WRF model for the Svalbard area at high spatial and temporal resolution. We show the sensitivity of the surface wind speed, air temperature and sea level pressure calculated by the Polar WRF model for three different parameterizations of the planetary boundary layer. Two-way nested domains were applied with the finest horizontal resolution of 3 km for the smallest domain. June 2008 and January 2009 are selected for tests of the WRF model with the GFS FNL data used as initial and boundary conditions. The results of simulations are compared with in-situ meteorological data measured at synoptic stations running in the nested model domains. Three independent simulations let to evaluate the sensitivity of downscaling results in each of nested domains and assess the role of chosen PBL schemes for model's accuracy. The results allow to quantify the role of different Polar WRF's PBL settings, which may be useful for long-term climatological mesoscale simulations as a tool for recognition of local aspects of Svalbard's climate. The long-term climatological simulations are the further aims of this project.

  4. Three-dimensional ultrasonic imaging of concrete elements using different SAFT data acquisition and processing schemes

    Energy Technology Data Exchange (ETDEWEB)

    Schickert, Martin, E-mail: martin.schickert@mfpa.de [Materialforschungs- und -prüfanstalt an der Bauhaus-Universität Weimar, Coudraystr. 9, 99425 Weimar (Germany)

    2015-03-31

    Ultrasonic testing systems using transducer arrays and the SAFT (Synthetic Aperture Focusing Technique) reconstruction allow for imaging the internal structure of concrete elements. At one-sided access, three-dimensional representations of the concrete volume can be reconstructed in relatively great detail, permitting to detect and localize objects such as construction elements, built-in components, and flaws. Different SAFT data acquisition and processing schemes can be utilized which differ in terms of the measuring and computational effort and the reconstruction result. In this contribution, two methods are compared with respect to their principle of operation and their imaging characteristics. The first method is the conventional single-channel SAFT algorithm which is implemented using a virtual transducer that is moved within a transducer array by electronic switching. The second method is the Combinational SAFT algorithm (C-SAFT), also named Sampling Phased Array (SPA) or Full Matrix Capture/Total Focusing Method (TFM/FMC), which is realized using a combination of virtual transducers within a transducer array. Five variants of these two methods are compared by means of measurements obtained at test specimens containing objects typical of concrete elements. The automated SAFT imaging system FLEXUS is used for the measurements which includes a three-axis scanner with a 1.0 m × 0.8 m scan range and an electronically switched ultrasonic array consisting of 48 transducers in 16 groups. On the basis of two-dimensional and three-dimensional reconstructed images, qualitative and some quantitative results of the parameters image resolution, signal-to-noise ratio, measurement time, and computational effort are discussed in view of application characteristics of the SAFT variants.

  5. Conservation laws for two (2 + 1)-dimensional differential-difference systems

    Energy Technology Data Exchange (ETDEWEB)

    Yu Guofu [Institute of Computational Mathematics and Scientific Engineering Computing, AMSS, Chinese Academy of Sciences, P.O. Box 2719, Beijing 100080 (China) and Graduate School of the Chinese Academy of Sciences, Beijing (China)]. E-mail: gfyu@lsec.cc.ac.cn; Tam, H.-W. [Department of Computer Science, Hong Kong Baptist University, Kowloon Tong, Hong Kong (China)]. E-mail: tam@comp.hkbu.edu.hk

    2006-10-15

    Two integrable differential-difference equations are considered. One is derived from the discrete BKP equation and the other is a symmetric (2 + 1)-dimensional Lotka-Volterra equation. An infinite number of conservation laws for the two differential-difference equations are deduced.

  6. Lax pairs and conservation laws for two differential-difference systems

    Energy Technology Data Exchange (ETDEWEB)

    Li Chunxia E-mail: lichx@lsec.cc.ac.cn

    2003-11-01

    A coupled extended Lotka-Volterra lattice and a special Toda lattice are derived from the existing bilinear equations. Starting from the corresponding bilinear Baecklund transformation, Lax pairs for these two differential-difference systems are obtained. Furthermore, an infinite number of conservation laws for the differential-difference equations are deduced from the Lax pairs in a systematic way.

  7. The effect of the chiral chemical potential on the chiral phase transition in the NJL model with different regularization schemes

    CERN Document Server

    Yu, Lang; Huang, Mei

    2015-01-01

    We study the chiral phase transition in the presence of the chiral chemical potential $\\mu_5$ using the two-flavor Nambu--Jona-Lasinio model. In particular, we analyze the reason why one can obtain two opposite behaviors of the chiral critical temperature as a function of $\\mu_5$ in the framework of different regularization schemes. We compare the modifications of the chiral condensate and the critical temperature due to $\\mu_5$ in different regularization schemes, analytically and numerically. Finally, we find that, for the conventional hard-cutoff regularization scheme, the increasing dependence of the critical temperature on the chiral chemical potential is an artifact, which is caused by the fact that it does not include complete contribution from the thermal fluctuations. When the thermal contribution is fully taken into account, the chiral critical temperature should decrease with $\\mu_5$.

  8. Modeling and Analysis of Resonance in LCL-Type Grid-Connected Inverters under Different Control Schemes

    Directory of Open Access Journals (Sweden)

    Yanxue Yu

    2017-01-01

    Full Text Available As a basic building block in power systems, the three-phase voltage-source inverter (VSI connects the distributed energy to the grid. For the inductor-capacitor-inductor (LCL-filter three-phase VSI, according to different current sampling position and different reference frame, there mainly exist four control schemes. Different control schemes present different impedance characteristics in their corresponding determined frequency range. To analyze the existing resonance phenomena due to the variation of grid impedances, the sequence impedance models of LCL-type grid-connected three-phase inverters under different control schemes are presented using the harmonic linearization method. The impedance-based stability analysis approach is then applied to compare the relative stability issues due to the impedance differences at some frequencies and to choose the best control scheme and the better controller parameters regulating method for the LCL-type three-phase VSI. The simulation and experiments both validate the resonance analysis results.

  9. Global patterns of conservation research importance in different countries of the world

    Science.gov (United States)

    Takahara, Teruhiko

    2016-01-01

    Conservation research is essential to help inform the science-based management of environments that support threatened and endangered wildlife; however, research effort is not necessarily uniform across countries globally. Here, we assessed how the research importance of conservation is distributed globally across different countries and what drives this variation. Specifically, we compared the number of conservation/ecological articles versus all scientific articles published for each country in relation to the number of endangered species, the protection status and number of ecosystems, and the economic status of each country (gross domestic product (GDP) per capita). We observed a significant and positive relationship between the proportion of conservation and ecology articles to all scientific articles with respect to the number of endangered species and the proportion of endangered species that are protected in a country, as well as GDP per capita. In conclusion, knowledge about the conservation and economic status of countries should be accounted for when predicting the research importance of conservation and ecology. PMID:27441117

  10. Global patterns of conservation research importance in different countries of the world.

    Science.gov (United States)

    Doi, Hideyuki; Takahara, Teruhiko

    2016-01-01

    Conservation research is essential to help inform the science-based management of environments that support threatened and endangered wildlife; however, research effort is not necessarily uniform across countries globally. Here, we assessed how the research importance of conservation is distributed globally across different countries and what drives this variation. Specifically, we compared the number of conservation/ecological articles versus all scientific articles published for each country in relation to the number of endangered species, the protection status and number of ecosystems, and the economic status of each country (gross domestic product (GDP) per capita). We observed a significant and positive relationship between the proportion of conservation and ecology articles to all scientific articles with respect to the number of endangered species and the proportion of endangered species that are protected in a country, as well as GDP per capita. In conclusion, knowledge about the conservation and economic status of countries should be accounted for when predicting the research importance of conservation and ecology.

  11. Global patterns of conservation research importance in different countries of the world

    Directory of Open Access Journals (Sweden)

    Hideyuki Doi

    2016-07-01

    Full Text Available Conservation research is essential to help inform the science-based management of environments that support threatened and endangered wildlife; however, research effort is not necessarily uniform across countries globally. Here, we assessed how the research importance of conservation is distributed globally across different countries and what drives this variation. Specifically, we compared the number of conservation/ecological articles versus all scientific articles published for each country in relation to the number of endangered species, the protection status and number of ecosystems, and the economic status of each country (gross domestic product (GDP per capita. We observed a significant and positive relationship between the proportion of conservation and ecology articles to all scientific articles with respect to the number of endangered species and the proportion of endangered species that are protected in a country, as well as GDP per capita. In conclusion, knowledge about the conservation and economic status of countries should be accounted for when predicting the research importance of conservation and ecology.

  12. Sensitivity analysis of different parameterization schemes using RegCM4.3 for the Carpathian region

    Science.gov (United States)

    Pieczka, Ildikó; Pongrácz, Rita; Szabóné André, Karolina; Kelemen, Fanni Dóra; Bartholy, Judit

    2016-10-01

    In order to quantify the impact of the use of different parameterization schemes on regional climate model outputs, hindcast experiments have been completed applying the Regional Climate Model version 4.3 (RegCM4.3) for the Carpathian region and its surroundings at 10-km horizontal resolution with three different cumulus convection schemes. Besides, the sensitivity of outputs for subgrid-scale processes is also studied by activating the subgrid Biosphere-Atmosphere Transfer Scheme (BATS) model within other RegCM experiments. Among the analyzed factors, RegCM is most sensitive to the applied convection scheme. The impact of closure assumption related to the used convective parameterization is secondary, while the use of subgridding has less influence on the outputs. RegCM4.3 results show improved performance over our previous model simulations but still have larger amplitude for annual precipitation cycle than the measurement-based reference data. Our validation results for temperature and precipitation suggest that for the selected region, the overall best performance is achieved when using the mixed Grell-Emanuel scheme together with Fritsch and Chappell closure.

  13. Use of different sampling schemes in machine learning-based prediction of hydrological models' uncertainty

    Science.gov (United States)

    Kayastha, Nagendra; Solomatine, Dimitri; Lal Shrestha, Durga; van Griensven, Ann

    2013-04-01

    In recent years, a lot of attention in the hydrologic literature is given to model parameter uncertainty analysis. The robustness estimation of uncertainty depends on the efficiency of sampling method used to generate the best fit responses (outputs) and on ease of use. This paper aims to investigate: (1) how sampling strategies effect the uncertainty estimations of hydrological models, (2) how to use this information in machine learning predictors of models uncertainty. Sampling of parameters may employ various algorithms. We compared seven different algorithms namely, Monte Carlo (MC) simulation, generalized likelihood uncertainty estimation (GLUE), Markov chain Monte Carlo (MCMC), shuffled complex evolution metropolis algorithm (SCEMUA), differential evolution adaptive metropolis (DREAM), partical swarm optimization (PSO) and adaptive cluster covering (ACCO) [1]. These methods were applied to estimate uncertainty of streamflow simulation using conceptual model HBV and Semi-distributed hydrological model SWAT. Nzoia catchment in West Kenya is considered as the case study. The results are compared and analysed based on the shape of the posterior distribution of parameters, uncertainty results on model outputs. The MLUE method [2] uses results of Monte Carlo sampling (or any other sampling shceme) to build a machine learning (regression) model U able to predict uncertainty (quantiles of pdf) of a hydrological model H outputs. Inputs to these models are specially identified representative variables (past events precipitation and flows). The trained machine learning models are then employed to predict the model output uncertainty which is specific for the new input data. The problem here is that different sampling algorithms result in different data sets used to train such a model U, which leads to several models (and there is no clear evidence which model is the best since there is no basis for comparison). A solution could be to form a committee of all models U and

  14. Stability of finite difference numerical simulations of acoustic logging-while-drilling with different perfectly matched layer schemes

    Institute of Scientific and Technical Information of China (English)

    Wang Hua; Tao Guo; Shang Xue-Feng; Fang Xin-Ding; Daniel R. Burns

    2013-01-01

    In acoustic logging-while-drilling (ALWD) finite difference in time domain (FDTD) simulations, large drill collar occupies, most of the fluid-filled borehole and divides the borehole fluid into two thin fluid columns (radius~27 mm). Fine grids and large computational models are required to model the thin fluid region between the tool and the formation. As a result, small time step and more iterations are needed, which increases the cumulative numerical error. Furthermore, due to high impedance contrast between the drill collar and fluid in the borehole (the difference is>30 times), the stability and efficiency of the perfectly matched layer (PML) scheme is critical to simulate complicated wave modes accurately. In this paper, we compared four different PML implementations in a staggered grid finite difference in time domain (FDTD) in the ALWD simulation, including field-splitting PML (SPML), multiaxial PML(M-PML), non-splitting PML (NPML), and complex frequency-shifted PML (CFS-PML). The comparison indicated that NPML and CFS-PML can absorb the guided wave reflection from the computational boundaries more efficiently than SPML and M-PML. For large simulation time, SPML, M-PML, and NPML are numerically unstable. However, the stability of M-PML can be improved further to some extent. Based on the analysis, we proposed that the CFS-PML method is used in FDTD to eliminate the numerical instability and to improve the efficiency of absorption in the PML layers for LWD modeling. The optimal values of CFS-PML parameters in the LWD simulation were investigated based on thousands of 3D simulations. For typical LWD cases, the best maximum value of the quadratic damping profile was obtained using one d0. The optimal parameter space for the maximum value of the linear frequency-shifted factor (α0) and the scaling factor (β0) depended on the thickness of the PML layer. For typical formations, if the PML thickness is 10 grid points, the global error can be reduced to<1%using

  15. Event-Triggered Schemes on Leader-Following Consensus of General Linear Multiagent Systems Under Different Topologies.

    Science.gov (United States)

    Xu, Wenying; Ho, Daniel W C; Li, Lulu; Cao, Jinde

    2017-01-01

    This paper investigates the leader-following consensus for multiagent systems with general linear dynamics by means of event-triggered scheme (ETS). We propose three types of schemes, namely, distributed ETS (distributed-ETS), centralized ETS (centralized-ETS), and clustered ETS (clustered-ETS) for different network topologies. All these schemes guarantee that all followers can track the leader eventually. It should be emphasized that all event-triggered protocols in this paper depend on local information and their executions are distributed. Moreover, it is shown that such event-triggered mechanism can significantly reduce the frequency of control's update. Further, positive inner-event time intervals are assured for those cases of distributed-ETS, centralized-ETS, and clustered-ETS. In addition, two methods are proposed to avoid continuous communication between agents for event detection. Finally, numerical examples are provided to illustrate the effectiveness of the ETSs.

  16. Classroom Games: The Allocation of Renewable Resources under Different Property Rights and Regulation Schemes.

    Science.gov (United States)

    Giraud, Kelly L.; Herrmann, Mark

    2002-01-01

    Describes a renewable resource allocation game designed to stimulate student interest in and understanding of market failure associated with open-access types of resource use. Employs the game to discuss advantages and disadvantages of property rights and regulation schemes. States the game benefits noneconomics majors in natural resource…

  17. A no-cost improved velocity-stress staggered-grid finite-difference scheme for modelling seismic wave propagation

    Science.gov (United States)

    Etemadsaeed, Leila; Moczo, Peter; Kristek, Jozef; Ansari, Anooshiravan; Kristekova, Miriam

    2016-10-01

    We investigate the problem of finite-difference approximations of the velocity-stress formulation of the equation of motion and constitutive law on the staggered grid (SG) and collocated grid (CG). For approximating the first spatial and temporal derivatives, we use three approaches: Taylor expansion (TE), dispersion-relation preserving (DRP), and combined TE-DRP. The TE and DRP approaches represent two fundamental extremes. We derive useful formulae for DRP and TE-DRP approximations. We compare accuracy of the numerical wavenumbers and numerical frequencies of the basic TE, DRP and TE-DRP approximations. Based on the developed approximations, we construct and numerically investigate 14 basic TE, DRP and TE-DRP finite-difference schemes on SG and CG. We find that (1) the TE second-order in time, TE fourth-order in space, 2-point in time, 4-point in space SG scheme (that is the standard (2,4) VS SG scheme, say TE-2-4-2-4-SG) is the best scheme (of the 14 investigated) for large fractions of the maximum possible time step, or, in other words, in a homogeneous medium; (2) the TE second-order in time, combined TE-DRP second-order in space, 2-point in time, 4-point in space SG scheme (say TE-DRP-2-2-2-4-SG) is the best scheme for small fractions of the maximum possible time step, or, in other words, in models with large velocity contrasts if uniform spatial grid spacing and time step are used. The practical conclusion is that in computer codes based on standard TE-2-4-2-4-SG, it is enough to redefine the values of the approximation coefficients by those of TE-DRP-2-2-2-4-SG for increasing accuracy of modelling in models with large velocity contrast between rock and sediments.

  18. Disparity in reimbursement for tuberculosis care among different health insurance schemes: evidence from three counties in central China

    Institute of Scientific and Technical Information of China (English)

    Yao Pan; Shanquan Chen; Manli Chen; Pei Zhang; Qian Long; Li Xiang; Henry Lucas

    2016-01-01

    Background:Health inequity is an important issue all around the world.The Chinese basic medical security system comprises three major insurance schemes,namely the Urban Employee Basic Medical Insurance (UEBMI),the Urban Resident Basic Medical Insurance (URBMI),and the New Cooperative Medical Scheme (NCMS).Little research has been conducted to look into the disparity in payments among the health insurance schemes in China.In this study,we aimed to evaluate the disparity in reimbursements for tuberculosis (TB) care among the abovementioned health insurance schemes.Methods:This study uses a World Health Organization (WHO) framework to analyze the disparities and equity relating to the three dimensions of health insurance:population coverage,the range of services covered,and the extent to which costs are covered.Each of the health insurance scheme's policies were categorized and analyzed.An analysis of the claims database of all hospitalizations reimbursed from 2010 to 2012 in three counties of Yichang city (YC),which included 1506 discharges,was conducted to identify the differences in reimbursement rates and out-of-pocket (OOP) expenses among the health insurance schemes.Results:Tuberculosis patients had various inpatient expenses depending on which scheme they were covered by (TB patients covered by the NCMS have less inpatient expenses than those who were covered by the URBMI,who have less inpatient expenses than those covered by the UEBMI).We found a significant horizontal inequity of healthcare utilization among the lower socioeconomic groups.In terms of financial inequity,TB patients who earned less paid more.The NCMS provides modest financial protection,based on income.Overall,TB patients from lower socioeconomic groups were the most vulnerable.Conclusion:There are large disparities in reimbursement for TB care among the three health insurance schemes and this,in turn,hampers TB control.Reducing the gap in health outcomes between the three health insurance

  19. 交错网格下MHD相容守恒格式的发展%Development of a consistent and conservative scheme on a staggered grid for liquid metal MHD flows

    Institute of Scientific and Technical Information of China (English)

    李俊峰; 倪明玖

    2011-01-01

    在低磁场雷诺数条件下,基于电势泊松方程,发展了交错网格下可以精确计算电流和洛伦兹力(电磁力)的相容守恒格式.采用压力为变量的原始变量法求解不可压缩Navier-Stokes方程,所计算的电流满足电荷守恒定律,所计算的电磁力满足动量守恒定律.对金属流体在Hartmann数50~5000范围内验证了格式的精确性.交错网格下相容守恒格式的发展为后续MHD稳定性分析、湍流的大涡模拟及直接数值模拟提供很好的选择.%A consistent and conservative scheme has been extended and developed on a staggered grid system for liquid metal MHD flow at a low magnetic Reynolds number by solving electrical potential Poisson equation based on the Ohm's law and the charge conservation law. The consistent scheme is used to ensure the calculated current density conserves the charge, and the divergence formula of the Lorentz force is used to ensure the momentum conservation. Simulation of liquid metal flows in a three-dimensional straight channel is conducted and compared with the analytical solutions from Shercliff's and Hunt's. The numerical results are in good agreement with analytical solutions for the Hartmann numbers from 50 to 5000. A fully conservative scheme on a staggered grid, which can conserve mass, momentum and kinetic energy and charge, is then developed with the central-symmetrical scheme for the convective term and the pressure term and with the consistent and conservative scheme for the calculation of the current density and the Lorentz force. A fully conservative scheme can be a good tool for numerical analysis of MHD flow instability, large eddy simulation (LES) and direct-numerical simulation (DNS) of MHD turbulence.

  20. THE FULLY IMPLICIT DIFFERENCE METHODS FOR A STIFF SYSTEM OF CONSERVATION LAWS%一个刚性守恒律方程组的全隐式差分方法

    Institute of Scientific and Technical Information of China (English)

    汤华中

    2001-01-01

    This paper is interested in a system of conservation laws with astiff relaxation term arised in viscoelasticity. The properties of a class of fully implicit finite dif ference methods approximating this system are analyzed, which include maximum principles, bounds on the total variation, L1-bounds, and L1-continuity estimates in term of some conserved physical quantity and the characteristic variables gener ated by difference schemes with proper initial data. These estimates are necessary for the existence of a bounded-total variation (BV) solution. Furthermore, we show that numerical entropy inequalities for some convex entropy pairs of the fully system hold.Keywords:Finite difference scheme, hyperbolic conservation laws,entropy inequality

  1. Sound classification of dwellings in the Nordic countries – Differences and similarities between the five national schemes

    DEFF Research Database (Denmark)

    Rasmussen, Birgit

    2012-01-01

    In all five Nordic countries, sound classification schemes for dwellings have been published in national standards being implemented and revised gradually since the late 1990s. The national classification criteria for dwellings originate from a common Nordic INSTA-B proposal from the 1990s, thus...... having several similarities. In 2012, status is that number and denotations of classes for dwellings are identical in the Nordic countries, but the structures of the standards and several details are quite different. Also the issues dealt with are different. Examples of differences are sound insulation...... for classification of such buildings. This paper presents and compares the main class criteria for sound insulation of dwellings and summarizes differences and similarities in criteria and in structures of standards. Classification schemes for dwellings also exist in several other countries in Europe...

  2. Assessment of the WRF-ARW model during fog conditions in a coastal arid region using different PBL schemes

    Science.gov (United States)

    Temimi, Marouane; Chaouch, Naira; Weston, Michael; Ghedira, Hosni

    2017-04-01

    This study covers five fog events reported in 2014 at Abu Dhabi International Airport in the United Arab Emirates (UAE). We assess the performance of WRF-ARW model during fog conditions and we intercompare seven different PBL schemes and assess their impact on the performance of the simulations. Seven PBL schemes, namely, Yonsei University (YSU), Mellor-Yamada-Janjic (MYJ), Moller-Yamada Nakanishi and Niino (MYNN) level 2.5, Quasi-Normal Scale Elimination (QNSE-EDMF), Asymmetric Convective Model (ACM2), Grenier-Bretherton-McCaa (GBM) and MYNN level 3 were tested. Radiosonde data from the Abu Dhabi International Airport and surface measurements of relative humidity (RH), dew point temperature, wind speed, and temperature profiles were used to assess the performance of the model. All PBL schemes showed comparable skills with relatively higher performance with the QNSE scheme. The average RH Root Mean Square Error (RMSE) and BIAS for all PBLs were 15.75 % and -9.07 %, respectively, whereas the obtained RMSE and BIAS when QNSE was used were 14.65 % and -6.3 % respectively. Comparable skills were obtained for the rest of the variables. Local PBL schemes showed better performance than non-local schemes. Discrepancies between simulated and observed values were higher at the surface level compared to high altitude values. The sensitivity to lead time showed that best simulation performances were obtained when the lead time varies between 12 and 18 hours. In addition, the results of the simulations show that better performance is obtained when the starting condition is dry.

  3. A simulation based approach to quantify the difference between event-based and routine water quality monitoring schemes

    Directory of Open Access Journals (Sweden)

    J.S. Lessels

    2015-09-01

    New hydrological insights for the region: The inclusion of event-based sampling improved annual load estimates of all sites with a maximum RMSE difference of 16.11 tonnes between event-based and routine sampling. Based on the accuracy of annual loads, event-based sampling was found to be more important in catchments with a large relief and high annual rainfall in this region. Using this approach, different sampling schemes can be compared based on limited historical data.

  4. An optimized staggered variable-grid finite-difference scheme and its application in cross-well acoustic survey

    Institute of Scientific and Technical Information of China (English)

    ZHAO HaiBo; WANG XiuMing

    2008-01-01

    In this paper, an optimized staggered variable-grid finite-difference (FD) method is developed in veloc-ity-stress elastic wave equations. On the basis of the dispersion-relation-preserving (DRP), a fourth-order finite-difference operator on non-uniform grids is constructed. The proposed algorithm is a continuous variable-grid method. It does not need interpolations for the field variables between re-gions with the fine spacing and the coarse one. The accuracy of the optimized scheme has been veri-fied with an analytical solution and a regular staggered-grid FD method for the eighth order accuracy in space. The comparisons of the proposed scheme with the variable-grid FD method based on Taylor series expansion are made. It is demonstrated that this optimized scheme has less dispersion errors than that with Taylor's series expansion. Thus, the proposed scheme uses coarser grids in numerical simulations than that constructed by the Taylor's series expansion. Finally, the capability of the opti-mized FD is demonstrated for a complex cross-well acoustic simulation. The numerical experiment shows that this method greatly saves storage requirements and computational time, and is stable.

  5. Computational Aero-Acoustic Using High-order Finite-Difference Schemes

    DEFF Research Database (Denmark)

    Zhu, Wei Jun; Shen, Wen Zhong; Sørensen, Jens Nørkær

    2007-01-01

    In this paper, a high-order technique to accurately predict flow-generated noise is introduced. The technique consists of solving the viscous incompressible flow equations and inviscid acoustic equations using a incompressible/compressible splitting technique. The incompressible flow equations ar...... discretizations of the acoustic equations. The classical fourth-order Runge-Kutta time scheme is applied to the acoustic equations for time discretization....

  6. Speech reception with different bilateral directional processing schemes: Influence of binaural hearing, audiometric asymmetry, and acoustic scenario.

    Science.gov (United States)

    Neher, Tobias; Wagener, Kirsten C; Latzel, Matthias

    2017-09-01

    Hearing aid (HA) users can differ markedly in their benefit from directional processing (or beamforming) algorithms. The current study therefore investigated candidacy for different bilateral directional processing schemes. Groups of elderly listeners with symmetric (N = 20) or asymmetric (N = 19) hearing thresholds for frequencies below 2 kHz, a large spread in the binaural intelligibility level difference (BILD), and no difference in age, overall degree of hearing loss, or performance on a measure of selective attention took part. Aided speech reception was measured using virtual acoustics together with a simulation of a linked pair of completely occluding behind-the-ear HAs. Five processing schemes and three acoustic scenarios were used. The processing schemes differed in the tradeoff between signal-to-noise ratio (SNR) improvement and binaural cue preservation. The acoustic scenarios consisted of a frontal target talker presented against two speech maskers from ±60° azimuth or spatially diffuse cafeteria noise. For both groups, a significant interaction between BILD, processing scheme, and acoustic scenario was found. This interaction implied that, in situations with lateral speech maskers, HA users with BILDs larger than about 2 dB profited more from preserved low-frequency binaural cues than from greater SNR improvement, whereas for smaller BILDs the opposite was true. Audiometric asymmetry reduced the influence of binaural hearing. In spatially diffuse noise, the maximal SNR improvement was generally beneficial. N0Sπ detection performance at 500 Hz predicted the benefit from low-frequency binaural cues. Together, these findings provide a basis for adapting bilateral directional processing to individual and situational influences. Further research is needed to investigate their generalizability to more realistic HA conditions (e.g., with low-frequency vent-transmitted sound). Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Optimization of Dengue Epidemics: A Test Case with Different Discretization Schemes

    Science.gov (United States)

    Rodrigues, Helena Sofia; Monteiro, M. Teresa T.; Torres, Delfim F. M.

    2009-09-01

    The incidence of Dengue epidemiologic disease has grown in recent decades. In this paper an application of optimal control in Dengue epidemics is presented. The mathematical model includes the dynamic of Dengue mosquito, the affected persons, the people's motivation to combat the mosquito and the inherent social cost of the disease, such as cost with ill individuals, educations and sanitary campaigns. The dynamic model presents a set of nonlinear ordinary differential equations. The problem was discretized through Euler and Runge Kutta schemes, and solved using nonlinear optimization packages. The computational results as well as the main conclusions are shown.

  8. Hosting Capacity of Solar Photovoltaics in Distribution Grids under Different Pricing Schemes

    DEFF Research Database (Denmark)

    Carollo, Riccardo; Chaudhary, Sanjay Kumar; Pillai, Jayakrishnan Radhakrishna

    2015-01-01

    and distributed battery storages, and locally absorb excess PV generation. This work analyzes the use of EV charging to increase the PV hosting capacity in LV networks, considering the electricity tariffs schemes like time-of-use (TOU) , net metering and Distribution Locational Marginal Pricing (DLMP) tariffs....... The results show that with the present TOU tariffs the EV integration in LV networks does not ease the grid bottlenecks for large PV penetration. Under the Net metering and DLMP the EV integration in LV grids tend to increase the PV hosting capacity....

  9. A real options approach to analyse wind energy investments under different support schemes

    DEFF Research Database (Denmark)

    Kitzing, Lena; Juul, Nina; Drud, Michael Stolbjerg Leni

    2016-01-01

    under feed-in tariffs, feed-in premiums and tradable green certificates. Investors can under certificate schemes require up to 3% higher profit margins than under tariffs due to higher variance in profits. Feed-in tariffs may lead to 15% smaller project sizes. This trade-off between faster deployment...... of smaller projects and slower deployment of larger projects is neglected using traditional net present value approaches. In the analysis of such trade-off, previous real options studies did not consider a capacity constraint, which is here shown to decrease the significance of the effect. The impact...

  10. Optimization of Dengue Epidemics: a test case with different discretization schemes

    CERN Document Server

    Rodrigues, Helena Sofia; Torres, Delfim F M; 10.1063/1.3241345

    2010-01-01

    The incidence of Dengue epidemiologic disease has grown in recent decades. In this paper an application of optimal control in Dengue epidemics is presented. The mathematical model includes the dynamic of Dengue mosquito, the affected persons, the people's motivation to combat the mosquito and the inherent social cost of the disease, such as cost with ill individuals, educations and sanitary campaigns. The dynamic model presents a set of nonlinear ordinary differential equations. The problem was discretized through Euler and Runge Kutta schemes, and solved using nonlinear optimization packages. The computational results as well as the main conclusions are shown.

  11. Hybrid Spectral Difference/Embedded Finite Volume Method for Conservation Laws

    CERN Document Server

    Choi, Jung J

    2014-01-01

    A novel hybrid spectral difference/embedded finite volume method is introduced in order to apply a discontinuous high-order method for large scale engineering applications involving discontinuities in flows with complex geometries. In the proposed hybrid approach, structured finite volume (FV) cells are embedded in hexahedral SD elements containing discontinuities, and FV based high-order shock-capturing scheme is employed to overcome Gibbs phenomenon. Thus, discontinuities are captured at the resolution of embedded FV cells within an SD element. In smooth flow regions, the SD method is chosen for its low numerical dissipation and computational efficiency preserving spectral-like solutions. The coupling between the SD elements and the elements with embedded FV cells are achieved by the mortar method. In this paper, the 5th-order WENO scheme with characteristic decomposition is employed as the shock-capturing scheme in the embedded FV cells, and the 5th-order SD method is used in the smooth flow field. The ord...

  12. A second-order high resolution finite difference scheme for a structured erythropoiesis model subject to malaria infection.

    Science.gov (United States)

    Ackleh, Azmy S; Ma, Baoling; Thibodeaux, Jeremy J

    2013-09-01

    We develop a second-order high-resolution finite difference scheme to approximate the solution of a mathematical model describing the within-host dynamics of malaria infection. The model consists of two nonlinear partial differential equations coupled with three nonlinear ordinary differential equations. Convergence of the numerical method to the unique weak solution with bounded total variation is proved. Numerical simulations demonstrating the achievement of the designed accuracy are presented.

  13. Explicit Finite-Difference Scheme for the Numerical Solution of the Model Equation of Nonlinear Hereditary Oscillator with Variable-Order Fractional Derivatives

    Directory of Open Access Journals (Sweden)

    Parovik Roman I.

    2016-09-01

    Full Text Available The paper deals with the model of variable-order nonlinear hereditary oscillator based on a numerical finite-difference scheme. Numerical experiments have been carried out to evaluate the stability and convergence of the difference scheme. It is argued that the approximation, stability and convergence are of the first order, while the scheme is stable and converges to the exact solution.

  14. Garden and landscape-scale correlates of moths of differing conservation status: significant effects of urbanization and habitat diversity.

    Directory of Open Access Journals (Sweden)

    Adam J Bates

    Full Text Available Moths are abundant and ubiquitous in vegetated terrestrial environments and are pollinators, important herbivores of wild plants, and food for birds, bats and rodents. In recent years, many once abundant and widespread species have shown sharp declines that have been cited by some as indicative of a widespread insect biodiversity crisis. Likely causes of these declines include agricultural intensification, light pollution, climate change, and urbanization; however, the real underlying cause(s is still open to conjecture. We used data collected from the citizen science Garden Moth Scheme (GMS to explore the spatial association between the abundance of 195 widespread British species of moth, and garden habitat and landscape features, to see if spatial habitat and landscape associations varied for species of differing conservation status. We found that associations with habitat and landscape composition were species-specific, but that there were consistent trends in species richness and total moth abundance. Gardens with more diverse and extensive microhabitats were associated with higher species richness and moth abundance; gardens near to the coast were associated with higher richness and moth abundance; and gardens in more urbanized locations were associated with lower species richness and moth abundance. The same trends were also found for species classified as increasing, declining and vulnerable under IUCN (World Conservation Union criteria. However, vulnerable species were more strongly negatively affected by urbanization than increasing species. Two hypotheses are proposed to explain this observation: (1 that the underlying factors causing declines in vulnerable species (e.g., possibilities include fragmentation, habitat deterioration, agrochemical pollution across Britain are the same in urban areas, but that these deleterious effects are more intense in urban areas; and/or (2 that urban areas can act as ecological traps for some

  15. Garden and Landscape-Scale Correlates of Moths of Differing Conservation Status: Significant Effects of Urbanization and Habitat Diversity

    Science.gov (United States)

    Bates, Adam J.; Sadler, Jon P.; Grundy, Dave; Lowe, Norman; Davis, George; Baker, David; Bridge, Malcolm; Freestone, Roger; Gardner, David; Gibson, Chris; Hemming, Robin; Howarth, Stephen; Orridge, Steve; Shaw, Mark; Tams, Tom; Young, Heather

    2014-01-01

    Moths are abundant and ubiquitous in vegetated terrestrial environments and are pollinators, important herbivores of wild plants, and food for birds, bats and rodents. In recent years, many once abundant and widespread species have shown sharp declines that have been cited by some as indicative of a widespread insect biodiversity crisis. Likely causes of these declines include agricultural intensification, light pollution, climate change, and urbanization; however, the real underlying cause(s) is still open to conjecture. We used data collected from the citizen science Garden Moth Scheme (GMS) to explore the spatial association between the abundance of 195 widespread British species of moth, and garden habitat and landscape features, to see if spatial habitat and landscape associations varied for species of differing conservation status. We found that associations with habitat and landscape composition were species-specific, but that there were consistent trends in species richness and total moth abundance. Gardens with more diverse and extensive microhabitats were associated with higher species richness and moth abundance; gardens near to the coast were associated with higher richness and moth abundance; and gardens in more urbanized locations were associated with lower species richness and moth abundance. The same trends were also found for species classified as increasing, declining and vulnerable under IUCN (World Conservation Union) criteria. However, vulnerable species were more strongly negatively affected by urbanization than increasing species. Two hypotheses are proposed to explain this observation: (1) that the underlying factors causing declines in vulnerable species (e.g., possibilities include fragmentation, habitat deterioration, agrochemical pollution) across Britain are the same in urban areas, but that these deleterious effects are more intense in urban areas; and/or (2) that urban areas can act as ecological traps for some vulnerable species of

  16. Square conservation systems and Hamiltonian systems

    Institute of Scientific and Technical Information of China (English)

    王斌; 曾庆存; 季仲贞

    1995-01-01

    The internal and external relationships between the square conservation scheme and the symplectic scheme are revealed by a careful study on the interrelation between the square conservation system and the Hamiltonian system in the linear situation, thus laying a theoretical basis for the application and extension of symplectic schemes to square conservations systems, and of those schemes with quadratic conservation properties to Hamiltonian systems.

  17. Effect of different hypoglycemic scheme ion serum inflammatory factors and blood hypercoagulability on patients with type 2 diabetes mellitus

    Institute of Scientific and Technical Information of China (English)

    Kun Zhang; Fei Feng

    2016-01-01

    Objective:To observe the effect of different hypoglycemic scheme on serum inflammatory factors and blood hypercoagulability in patients with type 2 diabetes mellitus (T2DM). Methods:A total of 186 cases patient with T2DM were randomly divided into 3 groups according to the different hypoglycemic scheme, such as: insulin group (69 cases), oral drug group (58 cases) and combination group (60 cases). Insulin group was given insulin aspart; oral drug group was given metformin and pioglitazone; combination group was given insulin aspart and metformin. For 6 mouths, to observe the different of serum inflammatory factorsα(TNF-α, hs-CRP, IL-6, MCP-1) and blood hypercoagulabilit indexes (PT, APTT, TT, FIB, PLT, TXB2) between the three groups.Results: After treatment, TNF-α, hs-CRP, IL-6, MCP-1 of the three groups were decreased with before (P0.05). After treatment, except PLT was no change, PT, APTT, TT of the three groups were increased and FIB, TXB2 were decreased with before (P0.05).Conclusions:All of the 3 hypoglycemic schemes are beneficial to reduce the inflammatory reaction and relieve the blood hypercoagulability, but the effect of insulin combined with oral drug is the best.

  18. Surgical versus conservative treatment following acute rupture of the Achilles tendon: is there a pedobarographic difference?

    Directory of Open Access Journals (Sweden)

    Karaaslan F

    2016-08-01

    Full Text Available Fatih Karaaslan,1 Musa Uğur Mermerkaya,1 Alper Çıraklı,2 Sinan Karaoğlu,3 Fuat Duygulu21Department of Orthopaedics and Traumatology, Faculty of Medicine, Bozok University, Yozgat, Turkey; 2Department of Orthopaedics and Traumatology, Kayseri Training Hospital, Kayseri, Turkey; 3Department of Orthopaedics and Traumatology, Memorial Kayseri Hospital, Kayseri, TurkeyIntroduction: Controversy remains regarding the optimal treatment method and postoperative rehabilitation of acute Achilles tendon ruptures. In this study, pedobarographic assessments of surgical and conservative treatments were compared.Material and methods: A prospective assessment was made of 16 patients (eight surgical, eight conservative and eight healthy controls using a plantar pressure measurement system. Biomechanical gait parameters were obtained using the Footscan dynamic gait analysis system. Kruskal–Wallis and Mann–Whitney U-tests were used for the evaluation of data.Results: Nineteen males and five females were assessed, with an average age of 42.0±11.9 years. Follow-up was completed in 16 patients. No statistically significant difference was determined between the two treatment groups with regard to the gait analysis, but a difference was observed with the control group (P<0.001. All patients were able to resume their prior activities after 6 months and regained normal ranges of motion, with a high rate of satisfaction. Most of the patients (75% were able to return to their pre-injury level of activities.Conclusion: Satisfactory results were obtained through conservative treatment of acute ruptures of the Achilles tendon. No significant differences or complications were observed in the group managed conservatively versus the group treated surgically. Further studies including 3D gait analyses and tendon biomechanical research are required to further investigate this issue.Keywords: Achilles tendon, acute rupture, pedobarographic analysis

  19. Comparison of different Aethalometer correction schemes and a reference multi-wavelength absorption technique for ambient aerosol data

    Science.gov (United States)

    Saturno, Jorge; Pöhlker, Christopher; Massabò, Dario; Brito, Joel; Carbone, Samara; Cheng, Yafang; Chi, Xuguang; Ditas, Florian; Hrabě de Angelis, Isabella; Morán-Zuloaga, Daniel; Pöhlker, Mira L.; Rizzo, Luciana V.; Walter, David; Wang, Qiaoqiao; Artaxo, Paulo; Prati, Paolo; Andreae, Meinrat O.

    2017-08-01

    Deriving absorption coefficients from Aethalometer attenuation data requires different corrections to compensate for artifacts related to filter-loading effects, scattering by filter fibers, and scattering by aerosol particles. In this study, two different correction schemes were applied to seven-wavelength Aethalometer data, using multi-angle absorption photometer (MAAP) data as a reference absorption measurement at 637 nm. The compensation algorithms were compared to five-wavelength offline absorption measurements obtained with a multi-wavelength absorbance analyzer (MWAA), which serves as a multiple-wavelength reference measurement. The online measurements took place in the Amazon rainforest, from the wet-to-dry transition season to the dry season (June-September 2014). The mean absorption coefficient (at 637 nm) during this period was 1.8 ± 2.1 Mm-1, with a maximum of 15.9 Mm-1. Under these conditions, the filter-loading compensation was negligible. One of the correction schemes was found to artificially increase the short-wavelength absorption coefficients. It was found that accounting for the aerosol optical properties in the scattering compensation significantly affects the absorption Ångström exponent (åABS) retrievals. Proper Aethalometer data compensation schemes are crucial to retrieve the correct åABS, which is commonly implemented in brown carbon contribution calculations. Additionally, we found that the wavelength dependence of uncompensated Aethalometer attenuation data significantly correlates with the åABS retrieved from offline MWAA measurements.

  20. A finite difference scheme for fractional sub-diffusion equations on an unbounded domain using artificial boundary conditions

    Science.gov (United States)

    Gao, Guang-hua; Sun, Zhi-zhong; Zhang, Ya-nan

    2012-04-01

    One-dimensional fractional anomalous sub-diffusion equations on an unbounded domain are considered in our work. Beginning with the derivation of the exact artificial boundary conditions, the original problem on an unbounded domain is converted into mainly solving an initial-boundary value problem on a finite computational domain. The main contribution of our work, as compared with the previous work, lies in the reduction of fractional differential equations on an unbounded domain by using artificial boundary conditions and construction of the corresponding finite difference scheme with the help of method of order reduction. The difficulty is the treatment of Neumann condition on the artificial boundary, which involves the time-fractional derivative operator. The stability and convergence of the scheme are proven using the discrete energy method. Two numerical examples clarify the effectiveness and accuracy of the proposed method.

  1. Thermal and structural finite element analysis of water cooled silicon monochromator for synchrotron radiation comparison of two different cooling schemes

    CERN Document Server

    Artemiev, A I; Busetto, E; Hrdy, J; Mrazek, D; Plesek, I; Savoia, A

    2001-01-01

    The article describes the results of Finite Element Analysis (FEA) of the first Si monochromator crystal distortions due to Synchrotron Radiation (SR) heat load and consequent analysis of the influence of the distortions on a double crystal monochromator performance. Efficiencies of two different cooling schemes are compared. A thin plate of Si crystal is lying on copper cooling support in both cases. There are microchannels inside the cooling support. In the first model the direction of the microchannels is parallel to the diffraction plane. In the second model the direction of the microchannels is perpendicular to the diffraction plane or in other words, it is a conventional cooling scheme. It is shown that the temperature field along the crystal volume is more uniform and more symmetrical in the first model than in the second (conventional) one.

  2. ONE-DIMENSIONAL GAS DYNAMICS PROBLEMS AND THEIR SOLUTION BASED ON HIGH-RESOLUTION FINITE DIFFERENCE SCHEMES

    Directory of Open Access Journals (Sweden)

    P. V. Bulat

    2015-07-01

    Full Text Available One-dimensional unsteady gas dynamics problems are revealing tests for the accuracy estimation of numerical solution with respect to simulation of supersonic flows of inviscid compressible gas. Numerical solution of Euler equations describing flows of inviscid compressible gas and conceding continuous and discontinuous solutions is considered. Discretization of Euler equations is based on finite volume method and WENO finite difference schemes. The numerical solutions computed are compared with the exact solution of Riemann problem. Monotonic correction of derivatives makes possible avoiding new extremes and ensures monotonicity of the numerical solution near the discontinuity, but it leads to the smoothness of the existing minimums and maximums and to the accuracy loss. Calculations with the use of WENO schemes give the possibility for obtaining accurate and monotonic solution with the presence of weak and strong gas dynamical discontinuities.

  3. Two finite-difference schemes that preserve the dissipation of energy in a system of modified wave equations

    CERN Document Server

    Macías-Díaz, J E; 10.1016/j.cnsns.2009.04.017

    2011-01-01

    In this work, we present two numerical methods to approximate solutions of systems of dissipative sine-Gordon equations that arise in the study of one-dimensional, semi-infinite arrays of Josephson junctions coupled through superconducting wires. Also, we present schemes for the total energy of such systems in association with the finite-difference schemes used to approximate the solutions. The proposed methods are conditionally stable techniques that yield consistent approximations not only in the domains of the solution and the total energy, but also in the approximation to the rate of change of energy with respect to time. The methods are employed in the estimation of the threshold at which nonlinear supratransmission takes place, in the presence of parameters such as internal and external damping, generalized mass, and generalized Josephson current. Our results are qualitatively in agreement with the corresponding problem in mechanical chains of coupled oscillators, under the presence of the same paramete...

  4. Identification of soil erosion risk areas for conservation planning in different states of India.

    Science.gov (United States)

    Sharda, V N; Mandal, Debashis; Ojasvi, P R

    2013-03-01

    Assessment of soil erosion risks, especially in the developing countries, is a challenging task mainly due to non-availability or insufficiency of relevant data. In this paper, the soil erosion risks have been estimated by integrating the spatial data on potential erosion rates and soil loss tolerance limits for conservation planning at state level in India. The erosion risk classes have been prioritized based upon the difference between the prevailing erosion rates and the permissible erosion limits. The analysis revealed that about 50% of total geographical area (TGA) of India, falling in five priority erosion risk classes, requires different intensity of conservation measures though about 91% area suffers from potential erosion rates varying from 40 t ha(-1) yr(-1). Statewise analysis indicated that Andhra Pradesh, Maharashtra and Rajasthan share about 75% of total area under priority Class 1 (6.4 M ha) though they account for only 19.4% of the total area (36.2 M ha) under very severe potential erosion rate category (> 40 t ha(-1)yr(-1)). It was observed that about 75% of total geographical area (TGA) in the states of Bihar, Gujarat, Haryana, Kerala and Punjab does not require any specific soil conservation measure as the potential erosion rates are well within the tolerance limits. The developed methodology can be successfully employed for prioritization of erosion risk areas at watershed, region or country level.

  5. Conservation priorities of useful plants from different techniques of collection and analysis of ethnobotanical data

    Directory of Open Access Journals (Sweden)

    Reinaldo F.P. de Lucena

    2013-03-01

    Full Text Available This study analyzes three methods of data analysis to verify which one would be more appropriate to get information aiming the conservation, selecting the use value (VU inventory in situ and conservation property index (IPC. It was developed in in Northeast Brazil, via interviewed householders (46 informants. The VU was calculated considering only the effective use of plants; the inventory in situ was made through the frequency of species occurrence in homes; and the IPC combining ethnobotanical and phytossociological data. It was observed a similar cast of the indicated species by VU and inventory in situ, being different from the IPC cast. As this study sought to analyze the best technique for species identification which were needing conservationist actions, and obtained different results among the chosen methods. It has been suggested the use of methods that unite in their analysis both ethnobotanical and ecological aspects, like in the plants list from the priority index of conservation, which demonstrated to be more efficient to identify rare species in the local vegetation. The VU and the inventory in situ are more efficient to identify the most known and used species in the communities, however without analyzing these plants in the local vegetation.

  6. A Finite Difference Scheme on a Priori Adapted Meshes for a Singularly Perturbed Parabolic Convection-Diffusion Equation

    Institute of Scientific and Technical Information of China (English)

    Grigory I. Shishkin

    2008-01-01

    A boundary value problem is considered for a singularly perturbed parabolic convection-diffusion equation; we construct a finite difference scheme on a priori (se-quentially) adapted meshes and study its convergence. The scheme on a priori adapted meshes is constructed using a majorant function for the singular component of the discrete solution, which allows us to find a priori a subdomain where the computed solution requires a further improvement. This subdomain is defined by the perturbation parameter ε, the step-size of a uniform mesh in x, and also by the required accuracy of the discrete solution and the prescribed number of refinement iterations K for im-proving the solution. To solve the discrete problems aimed at the improvement of the solution, we use uniform meshes on the subdomains. The error of the numerical so-lution depends weakly on the parameter ε. The scheme converges almost ε-uniformly, precisely, under the condition N-1 = o(ev), where N denotes the number of nodes in the spatial mesh, and the value v=v(K) can be chosen arbitrarily small for suitable K.

  7. Experimental and theoretical comparison of different optical excitation schemes for a compact coherent population trapping Rb vapor clock

    Science.gov (United States)

    Warren, Z.; Shahriar, M. S.; Tripathi, R.; Pati, G. S.

    2017-08-01

    We have investigated, theoretically as well as experimentally, the relative merits and demerits of using three different optical configurations for a compact coherent population trapping (CPT) vapor clock using 87Rb. These correspond to the following choices of polarizations for the two Raman beams: \\text{lin} \\parallel \\text{lin} , (σ,~σ ), and push-pull optical pumping (PPOP), applied on the D1 manifold. We have used a multi-level atomic model to study the dependence of the CPT spectrum on axial as well as transverse magnetic fields for these three schemes. Corresponding experimental studies have been performed using a laboratory scale CPT clock employing a two cm long, isotopically pure rubidium cell, loaded with a buffer gas. We observed a CPT contrast close to 20% with a sub-kilohertz linewidth by adopting the PPOP scheme. We discuss the strengths and weaknesses of each of the three optical excitation schemes, and present frequency-stability measurement data for the prototype clock.

  8. A stable high-order finite difference scheme for the compressible Navier Stokes equations: No-slip wall boundary conditions

    Science.gov (United States)

    Svärd, Magnus; Nordström, Jan

    2008-05-01

    A stable wall boundary procedure is derived for the discretized compressible Navier-Stokes equations. The procedure leads to an energy estimate for the linearized equations. We discretize the equations using high-order accurate finite difference summation-by-parts (SBP) operators. The boundary conditions are imposed weakly with penalty terms. We prove linear stability for the scheme including the wall boundary conditions. The penalty imposition of the boundary conditions is tested for the flow around a circular cylinder at Ma=0.1 and Re=100. We demonstrate the robustness of the SBP-SAT technique by imposing incompatible initial data and show the behavior of the boundary condition implementation. Using the errors at the wall we show that higher convergence rates are obtained for the high-order schemes. We compute the vortex shedding from a circular cylinder and obtain good agreement with previously published (computational and experimental) results for lift, drag and the Strouhal number. We use our results to compare the computational time for a given for a accuracy and show the superior efficiency of the 5th-order scheme.

  9. Comparative Study of Different SPH Schemes on Simulating Violent Water Wave Impact Flows

    Institute of Scientific and Technical Information of China (English)

    郑兴; 马庆位; 段文洋

    2014-01-01

    Free surface flows are of significant interest in Computational Fluid Dynamics (CFD). However, violent water wave impact simulation especially when free surface breaks or impacts on solid wall can be a big challenge for many CFD techniques. Smoothed Particle Hydrodynamics (SPH) has been reported as a robust and reliable method for simulating violent free surface flows. Weakly compressible SPH (WCSPH) uses an equation of state with a large sound speed, and the results of the WCSPH can induce a noisy pressure field and spurious oscillation of pressure in time history for wave impact problem simulation. As a remedy, the truly incompressible SPH (ISPH) technique was introduced, which uses a pressure Poisson equation to calculate the pressure. Although the pressure distribution in the whole field obtained by ISPH is smooth, the stability of the techniques is still an open discussion. In this paper, a new free surface identification scheme and solid boundary handling method are introduced to improve the accuracy of ISPH. This modified ISPH is used to study dam breaking flow and violent tank sloshing flows. On the comparative study of WCSPH and ISPH, the accuracy and efficiency are assessed and the results are compared with the experimental data.

  10. Comparative study of different SPH schemes on simulating violent water wave impact flows

    Science.gov (United States)

    Zheng, Xing; Ma, Qing-wei; Duan, Wen-yang

    2014-12-01

    Free surface flows are of significant interest in Computational Fluid Dynamics (CFD). However, violent water wave impact simulation especially when free surface breaks or impacts on solid wall can be a big challenge for many CFD techniques. Smoothed Particle Hydrodynamics (SPH) has been reported as a robust and reliable method for simulating violent free surface flows. Weakly compressible SPH (WCSPH) uses an equation of state with a large sound speed, and the results of the WCSPH can induce a noisy pressure field and spurious oscillation of pressure in time history for wave impact problem simulation. As a remedy, the truly incompressible SPH (ISPH) technique was introduced, which uses a pressure Poisson equation to calculate the pressure. Although the pressure distribution in the whole field obtained by ISPH is smooth, the stability of the techniques is still an open discussion. In this paper, a new free surface identification scheme and solid boundary handling method are introduced to improve the accuracy of ISPH. This modified ISPH is used to study dam breaking flow and violent tank sloshing flows. On the comparative study of WCSPH and ISPH, the accuracy and efficiency are assessed and the results are compared with the experimental data.

  11. Validation of Cross-calibration Schemes for Quantitative Bone SPECT/CT Using Different Sources under Various Geometric Conditions.

    Science.gov (United States)

    Miyaji, Noriaki; Miwa, Kenta; Motegi, Kazuki; Umeda, Takuro; Wagatsuma, Kei; Fukai, Shohei; Takiguchi, Tomohiro; Terauchi, Takashi; Koizumi, Mitsuru

    Several cross-calibration schemes have been proposed to produce quantitative values in bone SPECT imaging. Differences in the radionuclide sources and geometric conditions can decrease the accuracy of cross-calibration factor (CCF). The present study aimed to validate the effects of calibration schemes using different sources under various geometric conditions. Temporal variations as well as variations in acquisition counts and the shapes of (57)Co standard and (99m)Tc point sources and a (99m)Tc disk source were determined. The effects of the geometric conditions of the source-to-camera distance (SCD) and lateral distance on the CCF were investigated by moving the camera or source away from the origin. The system planar sensitivity of NEMA incorporated into a Symbia Intevo SPECT/CT device (Siemens®) was defined as reference values. The temporal variation in CCF using the (57)Co source was relatively stable within the range of 0.7% to 2.3%, whereas the (99m)Tc source ranged from 2.7% to 7.3%. In terms of source shape, the (57)Co standard point source was the most stable. Both SCD and lateral distance decreased as a function of distance from the origin. Errors in the geometric condition were higher for the (57)Co standard point source than the (99m)Tc disk source. Different calibration schemes influenced the reliability of quantitative values. The (57)Co standard point source was stable over a long period, and this helped to maintain the quality of quantitative SPECT/CT imaging data. The CCF accuracy of the (99m)Tc source decreased depending on the preparative method. The method of calibration for quantitative SPECT should be immediately standardized to eliminate uncertainty.

  12. A convergent 2D finite-difference scheme for the Dirac-Poisson system and the simulation of graphene

    KAUST Repository

    Brinkman, Daniel

    2014-01-01

    We present a convergent finite-difference scheme of second order in both space and time for the 2D electromagnetic Dirac equation. We apply this method in the self-consistent Dirac-Poisson system to the simulation of graphene. The model is justified for low energies, where the particles have wave vectors sufficiently close to the Dirac points. In particular, we demonstrate that our method can be used to calculate solutions of the Dirac-Poisson system where potentials act as beam splitters or Veselago lenses. © 2013 Elsevier Inc.

  13. Mixed Anti-diffusion Method for High Resolution Schemes

    Institute of Scientific and Technical Information of China (English)

    李荣华; 张威威

    2004-01-01

    In this paper we study a kied of mixed anti-diffusion method for partial differntial equations. Firstly, we use the method to construct some difference schemes for the conservation laws. The schemes are of second order accuracy and are total variation decreasing (TVD). In particular, there are only three knots involved in the schemes. Secondly, we extend the method to construct a few high accuracy difference schemes for elliptic and parabolic equations. Numerical experiments are carried out to illustrate the efficiency of the method.

  14. Comparison of different Aethalometer correction schemes and a reference multi-wavelength absorption technique for ambient aerosol data

    Directory of Open Access Journals (Sweden)

    J. Saturno

    2017-08-01

    Full Text Available Deriving absorption coefficients from Aethalometer attenuation data requires different corrections to compensate for artifacts related to filter-loading effects, scattering by filter fibers, and scattering by aerosol particles. In this study, two different correction schemes were applied to seven-wavelength Aethalometer data, using multi-angle absorption photometer (MAAP data as a reference absorption measurement at 637 nm. The compensation algorithms were compared to five-wavelength offline absorption measurements obtained with a multi-wavelength absorbance analyzer (MWAA, which serves as a multiple-wavelength reference measurement. The online measurements took place in the Amazon rainforest, from the wet-to-dry transition season to the dry season (June–September 2014. The mean absorption coefficient (at 637 nm during this period was 1.8 ± 2.1 Mm−1, with a maximum of 15.9 Mm−1. Under these conditions, the filter-loading compensation was negligible. One of the correction schemes was found to artificially increase the short-wavelength absorption coefficients. It was found that accounting for the aerosol optical properties in the scattering compensation significantly affects the absorption Ångström exponent (åABS retrievals. Proper Aethalometer data compensation schemes are crucial to retrieve the correct åABS, which is commonly implemented in brown carbon contribution calculations. Additionally, we found that the wavelength dependence of uncompensated Aethalometer attenuation data significantly correlates with the åABS retrieved from offline MWAA measurements.

  15. Difference schemes with intrinsic parallelism for quasi-linear parabolic systems

    Institute of Scientific and Technical Information of China (English)

    周毓麟

    1997-01-01

    The boundary value problem for quasi-linear parabolic system is solved by the finite difference method with intrinsic parallelism The existence and uniqueness and convergence theorems of the discrete vector solu tions of the nonlinear difference system with intrinsic parallelism are proved The limiting vector function is just the unique generalized solution of the original problem for the parabolic system

  16. Agrobiodiversity and in situ conservation in quilombola home gardens with different intensities of urbanization

    Directory of Open Access Journals (Sweden)

    Julia Vieira da Cunha Ávila

    Full Text Available ABSTRACT Among the agricultural environments of traditional communities, home gardens are frequently cited as high agrobiodiversity sites. However, the agrobiodiversity of home gardens along a rural-urban gradient demands study in order to identify possible influences of urbanization and to support mitigation of impacts. The present work investigated the role home gardens play in the in situ agrobiodiversity conservation of plants in quilombola communities with different degrees of urbanization. The study found that more urbanized communities have larger home gardens, but the average richness of plant species in these areas was not statistically different among the communities. Furthermore, the abundance of plant species was similar. Medicinal and food plants were mainly found in home gardens of the communities with high to intermediate levels of urbanization, while ornamental plants were more common in rural community home gardens. It is believed that crop exclusivity in home gardens of the more urbanized communities highly influenced the results, increasing the role home gardens play in maintaining traditional practices. The elevated and statistically equal species richness in home gardens suggests that, despite the factors generated by urbanization, all of the communities are very important for in situ conservation of native and introduced species.

  17. Determination of a control parameter of the r-modified Crank-Nicholson difference scheme for the Schrödinger equation

    Science.gov (United States)

    Ashyralyev, Allaberen; Urun, Mesut

    2016-08-01

    In the present paper, the second order of accuracy r-modified Crank-Nicholson difference schemes are presented for the numerical solution of the boundary value problem for the Schrödinger differential equation with parameter { i d/u (t ) d t +A u (t )+i u (t )=f (t )+p , 0 difference scheme is presented. The stability inequalities for the solution of difference schemes for three determination of a control parameter problems for the Schrödinger equation are given.

  18. Construction of stable explicit finite-difference schemes for Schroedinger type differential equations

    Science.gov (United States)

    Mickens, Ronald E.

    1989-01-01

    A family of conditionally stable, forward Euler finite difference equations can be constructed for the simplest equation of Schroedinger type, namely u sub t - iu sub xx. Generalization of this result to physically realistic Schroedinger type equations is presented.

  19. Dynamic Evaluation of LCL-type Grid-Connected Inverters with Different Current Feedback Control Schemes

    DEFF Research Database (Denmark)

    Han, Yang; Li, Zipeng; Guerrero, Josep M.

    2015-01-01

    Proportional-resonant (PR) compensator and LCL filter becomes a better choice in grid-connected inverter system with high performance and low costs. However, the resonance phenomenon caused by LCL filter affect the system stability significantly. In this paper, the stability problem of three...... of the controller and filter with different feedback configurations are provided. The impacts of digital delay, PR parameters and LCL parameters on different control strategies are also investigated. Finally, the theoretical analysis are validated by simulation results....

  20. Parallel adaptive mesh refinement method based on WENO finite difference scheme for the simulation of multi-dimensional detonation

    Science.gov (United States)

    Wang, Cheng; Dong, XinZhuang; Shu, Chi-Wang

    2015-10-01

    For numerical simulation of detonation, computational cost using uniform meshes is large due to the vast separation in both time and space scales. Adaptive mesh refinement (AMR) is advantageous for problems with vastly different scales. This paper aims to propose an AMR method with high order accuracy for numerical investigation of multi-dimensional detonation. A well-designed AMR method based on finite difference weighted essentially non-oscillatory (WENO) scheme, named as AMR&WENO is proposed. A new cell-based data structure is used to organize the adaptive meshes. The new data structure makes it possible for cells to communicate with each other quickly and easily. In order to develop an AMR method with high order accuracy, high order prolongations in both space and time are utilized in the data prolongation procedure. Based on the message passing interface (MPI) platform, we have developed a workload balancing parallel AMR&WENO code using the Hilbert space-filling curve algorithm. Our numerical experiments with detonation simulations indicate that the AMR&WENO is accurate and has a high resolution. Moreover, we evaluate and compare the performance of the uniform mesh WENO scheme and the parallel AMR&WENO method. The comparison results provide us further insight into the high performance of the parallel AMR&WENO method.

  1. Conservation and antigenicity of N-terminal sequences of GP185 from different Plasmodium falciparum isolates.

    Science.gov (United States)

    Howard, R F; Ardeshir, F; Reese, R T

    1986-01-01

    Complementary DNA (cDNA) clones for GP185, a major antigenically diverse glycoprotein of Plasmodium falciparum, were isolated from a cDNA library of the Honduras I/CDC (Honduras I) isolate, and 1052 bp were sequenced. The expression of cDNA fragments in Escherichia coli using the vector pCQV2 allowed verification of the reading frame. This GP185 cDNA sequence, like the cDNA sequence for a homologous gene of the K1 isolate [Hall et al., Nature 311 (1984) 379-382], codes for a polypeptide which is truncated due to multiple, in-frame stop codons. This polypeptide corresponds to the N-terminal 15% of the proposed coding region of the GP185 gene [Holder et al., Nature 317 (1985) 270-273]. Comparison of the nucleotide sequences for the GP185 gene of Honduras I and five other isolates indicated that there are two areas of conserved DNA sequence, one of 310 bp (beginning 181 bp upstream from the proposed initiation codon) and the other of greater than or equal to 360 bp (located entirely within the coding region), separated by a region encoding isolate-specific tandem amino acid repeats. Rat antiserum was raised to a fusion protein derived from the conserved regions and the intervening repeat region of this Honduras I protein. This antiserum bound GP185 on immunoblots of the homologous Honduras I isolate and the heterologous K1 isolate, which has different tandem repeats. Serum from owl monkeys and humans previously infected with P. falciparum reacted with the fusion protein on immunoblots demonstrating that determinants in the N-terminal 15% of GP185 were immunogenic in infected individuals and suggesting that some of these sites are conserved among isolates.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. Reshaping conservation

    DEFF Research Database (Denmark)

    Funder, Mikkel; Danielsen, Finn; Ngaga, Yonika

    2013-01-01

    members strengthen the monitoring practices to their advantage, and to some extent move them beyond the reach of government agencies and conservation and development practitioners. This has led to outcomes that are of greater social and strategic value to communities than the original 'planned' benefits......, although the monitoring scheme has also to some extent become dominated by local 'conservation elites' who negotiate the terrain between the state and other community members. Our findings suggest that we need to move beyond simplistic assumptions of community strategies and incentives in participatory...... conservation and allow for more adaptive and politically explicit governance spaces in protected area management....

  3. Eighth-Order Compact Finite Difference Scheme for 1D Heat Conduction Equation

    Directory of Open Access Journals (Sweden)

    Asma Yosaf

    2016-01-01

    Full Text Available The purpose of this paper is to develop a high-order compact finite difference method for solving one-dimensional (1D heat conduction equation with Dirichlet and Neumann boundary conditions, respectively. A parameter is used for the direct implementation of Dirichlet and Neumann boundary conditions. The introduced parameter adjusts the position of the neighboring nodes very next to the boundary. In the case of Dirichlet boundary condition, we developed eighth-order compact finite difference method for the entire domain and fourth-order accurate proposal is presented for the Neumann boundary conditions. In the case of Dirichlet boundary conditions, the introduced parameter behaves like a free parameter and could take any value from its defined domain but for the Neumann boundary condition we obtained a particular value of the parameter. In both proposed compact finite difference methods, the order of accuracy is the same for all nodes. The time discretization is performed by using Crank-Nicholson finite difference method. The unconditional convergence of the proposed methods is presented. Finally, a set of 1D heat conduction equations is solved to show the validity and accuracy of our proposed methods.

  4. Finite difference schemes for a nonlinear black-scholes model with transaction cost and volatility risk

    DEFF Research Database (Denmark)

    Mashayekhi, Sima; Hugger, Jens

    2015-01-01

    market. In this paper, we compare several finite difference methods for the solution of this model with respect to precision and order of convergence within a computationally feasible domain allowing at most 200 space steps and 10000 time steps. We conclude that standard explicit Euler comes out...

  5. Mean square convergent three points finite difference scheme for random partial differential equations

    Directory of Open Access Journals (Sweden)

    Magdy A. El-Tawil

    2012-10-01

    Full Text Available In this paper, the random finite difference method with three points is used in solving random partial differential equations problems mainly: random parabolic, elliptic and hyperbolic partial differential equations. The conditions of the mean square convergence of the numerical solutions are studied. The numerical solutions are computed through some numerical case studies.

  6. Function and value of water conservation in different age classes of Acacia mangium plantations

    Institute of Scientific and Technical Information of China (English)

    HE Bin; QIN Wuming; WU Qingbiao; DAI Jun; HUANG Yong; LIU Feng

    2007-01-01

    For this paper,we studied the water-holding capacity of canopy,vegetation layer under canopy and litter layer,the water-holding capacity and permeability of soil as well as their changes with growth of stands in Acacia mangium plantations of three different age classes(four-,seven-and 11-year-old).Results show that total waterholding above ground in the order of 11-year stand age(52.86 t/hm2)>seven-year stand age(41.90 t/hm2)>seven-year stand age(25.78 t/hm2),the increment tendency increased with stand age.Similar sequence also obtained on the water-holding capacity and permeation capacity of soil (0-=40cm).The total water-storage capacity both above ground and soil in four-year-old,seven-year-old and 11year-old of A.mangium plantations were 2,023.0,2,158.4 and 2,260.4 t/hm2,respectively,and the all value of water conservation were 1,372.70,1,474.42 and 1,549.91 yuan (RMB)/hm2,respectively.Therefore,A.mangium plantation had a good ability to modify soil structure and good water conservation function.

  7. A global multilevel atmospheric model using a vector semi-Lagrangian finite-difference scheme. I - Adiabatic formulation

    Science.gov (United States)

    Bates, J. R.; Moorthi, S.; Higgins, R. W.

    1993-01-01

    An adiabatic global multilevel primitive equation model using a two time-level, semi-Lagrangian semi-implicit finite-difference integration scheme is presented. A Lorenz grid is used for vertical discretization and a C grid for the horizontal discretization. The momentum equation is discretized in vector form, thus avoiding problems near the poles. The 3D model equations are reduced by a linear transformation to a set of 2D elliptic equations, whose solution is found by means of an efficient direct solver. The model (with minimal physics) is integrated for 10 days starting from an initialized state derived from real data. A resolution of 16 levels in the vertical is used, with various horizontal resolutions. The model is found to be stable and efficient, and to give realistic output fields. Integrations with time steps of 10 min, 30 min, and 1 h are compared, and the differences are found to be acceptable.

  8. Efficiency study of different photovoltaic plant connection schemes under dynamic shading

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez Reinoso, C.R.; Milone, D.H. [Centro de Investigacion y Desarrollo en Senales, Sistemas e Inteligencia Computacional (SINC), Facultad de Ing. y Ciencias Hidricas UNL-CONICET, Ciudad Universitaria (3000) Santa Fe (Argentina); Buitrago, R.H. [Instituto de Desarrollo Tecnologico para la Industria Quimica (INTEC) UNL-CONICET, Guemes 3450 (3000) Santa Fe (Argentina)

    2010-06-15

    An important growth in the power of the photovoltaic systems connected to a grid has recently been observed. In spite of the advances in module technology, the problems in the system design increased, especially regarding the surface of the earth they occupy. In this work we propose a complete model for plant simulation with different wiring diagrams and under dynamic shading. Results obtained from simulations showed that the configuration with the lowest performance was that of only one serial-parallel group, whereas the highest efficiency corresponded to a design of groups of modules in parallel connected then in series. In general, a higher efficiency was obtained diminishing the quantity of modules in series and increasing their number in parallel. The simulation model proposed allows exploring different alternatives of wiring modules and finding the most efficient configurations for photovoltaic plants of medium and high power. (author)

  9. Monitoring the effects of different conservation treatments on paper-infecting fungi

    Science.gov (United States)

    Michaelsen, Astrid; Pinzari, Flavia; Barbabietola, Nicoletta; Piñar, Guadalupe

    2013-01-01

    Fungi are among the most degradative organisms inducing biodeterioration of paper-based items of cultural heritage. Appropriate conservation measures and restoration treatments to deal with fungal infections include mechanical, chemical, and biological methods, which entail effects on the paper itself and health hazards for humans. Three different conservation treatments, namely freeze-drying, gamma rays, and ethylene oxide fumigation, were compared and monitored to assess their short- (one month, T1) and long-term (one year, T2) effectiveness to inhibit fungal growth. After the inoculation with fungi possessing cellulose hydrolysis ability — Chaetomium globosum, Trichoderma viride, and Cladosporium cladosporioides — as single strains or as a mixture, different quality paper samples were treated and screened for fungal viability by culture-dependent and -independent techniques. Results derived from both strategies were contradictory. Both gamma irradiation and EtO fumigation showed full efficacy as disinfecting agents when evaluated with cultivation techniques. However, when using molecular analyses, the application of gamma rays showed a short-term reduction in DNA recovery and DNA fragmentation; the latter phenomenon was also observed in a minor degree in samples treated with freeze-drying. When RNA was used as an indicator of long-term fungal viability, differences in the RNA recovery from samples treated with freeze-drying or gamma rays could be observed in samples inoculated with the mixed culture. Only the treatment with ethylene oxide proved negative for both DNA and RNA recovery. Therefore, DNA fragmentation after an ethylene oxide treatment can hamper future paleogenetic and archaeological molecular studies on the objects. PMID:24092956

  10. Test of the Louis scheme and COARE algorithm for friction velocity in different wind-sea/swell regimes

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The Louis scheme and the COARE algorithm (version 3.0) are tested against eddy covariance and inertial dissipation methods for friction velocity estimates in different wind-sea/swell regimes. Atmospheric forcing data, tabulated by Donelan et al. (1997.J Phys Oceanog, 27:2 087~2 099), were collected from a mast on the foredeck ofa SWATH (small water-plane area, twin hull) ship in deep sea off the State of Virginia during the surface wave dynamics experiment. These data are representative of low to moderate wind regimes.The aerodynamic roughness length is determined by using the Charnock relationship. The intercomparison shows that the Louis scheme and the COARE algorithm underestimate the friction velocity by 6% and 3% respectively under pure wind sea conditions, 15% and 13% respectively under cross swell conditions, and 21% and 17% respectively under counter swell conditions. The analysis shows that these underestimations were caused by the method chosen to determine the aerodynamic roughness length because it significantly underestimates the aerodynamic roughness length. It is especially true under the cross swell and counter swell conditions.

  11. An efficient hybrid pseudospectral/finite-difference scheme for solving the TTI pure P-wave equation

    KAUST Repository

    Zhan, Ge

    2013-02-19

    The pure P-wave equation for modelling and migration in tilted transversely isotropic (TTI) media has attracted more and more attention in imaging seismic data with anisotropy. The desirable feature is that it is absolutely free of shear-wave artefacts and the consequent alleviation of numerical instabilities generally suffered by some systems of coupled equations. However, due to several forward-backward Fourier transforms in wavefield updating at each time step, the computational cost is significant, and thereby hampers its prevalence. We propose to use a hybrid pseudospectral (PS) and finite-difference (FD) scheme to solve the pure P-wave equation. In the hybrid solution, most of the cost-consuming wavenumber terms in the equation are replaced by inexpensive FD operators, which in turn accelerates the computation and reduces the computational cost. To demonstrate the benefit in cost saving of the new scheme, 2D and 3D reverse-time migration (RTM) examples using the hybrid solution to the pure P-wave equation are carried out, and respective runtimes are listed and compared. Numerical results show that the hybrid strategy demands less computation time and is faster than using the PS method alone. Furthermore, this new TTI RTM algorithm with the hybrid method is computationally less expensive than that with the FD solution to conventional TTI coupled equations. © 2013 Sinopec Geophysical Research Institute.

  12. Computable error estimates of a finite difference scheme for option pricing in exponential Lévy models

    KAUST Repository

    Kiessling, Jonas

    2014-05-06

    Option prices in exponential Lévy models solve certain partial integro-differential equations. This work focuses on developing novel, computable error approximations for a finite difference scheme that is suitable for solving such PIDEs. The scheme was introduced in (Cont and Voltchkova, SIAM J. Numer. Anal. 43(4):1596-1626, 2005). The main results of this work are new estimates of the dominating error terms, namely the time and space discretisation errors. In addition, the leading order terms of the error estimates are determined in a form that is more amenable to computations. The payoff is only assumed to satisfy an exponential growth condition, it is not assumed to be Lipschitz continuous as in previous works. If the underlying Lévy process has infinite jump activity, then the jumps smaller than some (Formula presented.) are approximated by diffusion. The resulting diffusion approximation error is also estimated, with leading order term in computable form, as well as the dependence of the time and space discretisation errors on this approximation. Consequently, it is possible to determine how to jointly choose the space and time grid sizes and the cut off parameter (Formula presented.). © 2014 Springer Science+Business Media Dordrecht.

  13. Special funding schemes for innovative medical devices in French hospitals: the pros and cons of two different approaches.

    Science.gov (United States)

    Martelli, Nicolas; van den Brink, Hélène

    2014-07-01

    Financing innovative medical devices is an important challenge for national health policy makers, and a crucial issue for hospitals. However, when innovative medical devices are launched on the European market there is generally little clinical evidence regarding both efficacy and safety, both because of the flaws in the European system for regulating such devices, and because they are at an early stage of development. To manage the uncertainty surrounding the reimbursement of innovation, several European countries have set up temporary funding schemes to generate evidence about the effectiveness of devices. This article explores two different French approaches to funding innovative in-hospital devices and collecting supplementary data: the coverage with evidence development (CED) scheme introduced under Article L. 165-1-1 of the French Social Security Code; and national programs for hospital-based research. We discuss pros and cons of both approaches in the light of CED policies in Germany and the UK. The CED policies for devices share common limitations. Thus, transparency of CED processes should be enhanced and decisions need to be made in a timely way. Finally, we think that closer collaboration between manufacturers, health authorities and hospitals is essential to make CED policies more operational.

  14. Comparative Studies of Different Mesoscale Convection Parameterization Schemes in the Simulation of Mei-Yu Front Heavy Rain

    Institute of Scientific and Technical Information of China (English)

    PING Fan; LUO Zhe-Xian

    2010-01-01

    The mei-yu front heavy rainstorms occurred over Nanjing on 3-5 and 8-9 July 2003 and were simu-lated in this paper using the Weather Research and Fore-casting Model (WRFv3.1) with various mesoscale con-vection parameterization schemes (MCPSs). The simula-tions show that the temporal and spatial evolution and distribution of rainstorms can be modeled; however, there was incongruity between the comparative simulations of four different MCPSs and the observed data. These dis-parities were exhibited in the simulations of both the 24-hour surface rainfall total and the hourly precipitation rate. Further analysis revealed that the discrepancies of vertical velocity and the convective vorticity vector (CVV) between the four simulations were attributed to the devia-tion of rainfall values. In addition, the simulations show that the mid-scale convection, particularly the mesoscale convection system (MCS) formation, can be well simu-lated with the proper mesoscale convection parameteriza-tion schemes and may be a crucial factor of the mei-yu front heavy rainstorm. These results suggest that, in an effort to enhance simulation'and prediction of heavy rain-fall and rainstorms, subsequent studies should focus on the development and improvement of MCPS.

  15. Maastricht Ⅱ treatment scheme and efficacy of different proton pump inhibitors in eradicating Helicobacter pylori

    Institute of Scientific and Technical Information of China (English)

    Engin Altintas; Orhan Sezgin; Oguz Ulu; Ozlem Aydin; Handan Camdeviren

    2004-01-01

    AIM: The Maastricht Ⅱ criteria suggest the use of amoxicillin and clarithromycin in addition to a proton pump inhibitor over 7-10 d as a first line therapy in the eradication of Helicobacter pylori(H pylori). For each proton pump inhibitor, various rates of eradication have been reported. The present study was to compare the efficacy of different proton pump inhibitors like omeprazole, lansoprazole and pantoprazole in combination with amoxicillin and clarithromycin in the first line eradication of H pylori and to investigate the success of H pylori eradication in our district.METHODS: A total of 139 patients were included having a Helicobacter pylori(+) gastroduodenal disorders diagnosed by means of histology and urease test. Besides amoxicillin (1 000 mg twice a day) and clarithromycin (500 mg twice a day), they were randomized to take omeprazole (20 mg twice a day), or lansoprazole (30 mg twice a day), or pantoprozole (40 mg twice a day) for 14 d. Four weeks after the therapy, the eradication was assessed by means of histology and urease test. It was evaluated as eradicated if the H pylori was found negative in both. The complaints (pain in epigastrium, nocturnal pain, pyrosis and bloating)were graded in accordance with the Licert scale. The compliance of the patients was recorded.RESULTS: The eradication was found to be 40.8% in the omeprazole group, 43.5% in the lansoprazole group and 47.4% in the pantoprazole group. Sixty-three out of 139patients (45%) had eradication. No statistically significant difference was observed between the groups. Significant improvements were seen in terms of the impact on the symptom scores in each group.CONCLUSION: There was no difference between omeprazole, lansoprazole and pantoprazole in H pylori eradication, and the rate of eradication was as low as 45%.Symptoms were improved independent of the eradication in each treatment group. The iow eradication rates suggest that the antibiotic resistance or the genetic differences of

  16. Finite difference schemes for a nonlinear black-scholes model with transaction cost and volatility risk

    DEFF Research Database (Denmark)

    Mashayekhi, Sima; Hugger, Jens

    2015-01-01

    Several nonlinear Black-Scholes models have been proposed to take transaction cost, large investor performance and illiquid markets into account. One of the most comprehensive models introduced by Barles and Soner in [4] considers transaction cost in the hedging strategy and risk from an illiquid...... market. In this paper, we compare several finite difference methods for the solution of this model with respect to precision and order of convergence within a computationally feasible domain allowing at most 200 space steps and 10000 time steps. We conclude that standard explicit Euler comes out...

  17. Color deviations in phosphor converted high power light emitting diodes under different dimming schemes

    Energy Technology Data Exchange (ETDEWEB)

    Ludwiczak, Bogna, E-mail: bogna.ludwiczak@zumtobelgroup.com [Zumtobel Lighting GmbH, Schweizerstr.30, 6851 Dornbirn (Austria); Jantsch, Wolfgang [Institut für Halbleiter- und Festkörperphysik, Johannes Kepler Universität, 4040 Linz (Austria)

    2015-02-15

    We investigate experimentally the color stability of high power phosphor converted InGaN LEDs under pulse width modulation (PWM) and continuous current reduction (CCR) dimming modes and for varied operation temperatures. Our measurements reveal that the chromaticity coordinate pathways of the warm white and the cold white LED's differ for the same operation conditions. The color deviation- minimizing phenomenon of opposite peak wavelength shifts appears only for a cold white LED under CCR driving mode. This favorable effect does not occur for warm white LEDs. This type of LED exhibits the best color stability under PWM driving mode. The experimental results are consistently explained in terms of the quantum confined Stark effect and temperature induced changes of the LED emission. - Highlights: • Cold and warm white LEDs reacts colorimetrically unlike in different driving modes. • For cold white emission driving conditions are crucial. • Opposite peak wavelength shifts reduces color deviations for cold white emission. • For warm white emission rather phosphor properties determines color deviations.

  18. Design Error Performance of Space-Frequency Block Coded OFDM Systems with Different Equalizers and For Different Modulation Schemes

    Directory of Open Access Journals (Sweden)

    Rijhun Tripathi

    2012-01-01

    Full Text Available —Multiple transmit and receive antennas can be used to form multiple-input multiple-output (MIMO channels to increase the capacity (by a factor of the minimum number of transmit and receive antennas and data rate. In this paper, the combination of MIMO technology and orthogonal frequency division multiplexing (OFDM systems is considered for wideband transmission to mitigate inter symbol interference and to enhance system capacity. It owns the advantages of both MIMO and OFDM. MIMO-OFDM system exploits the space and frequency diversity simultaneously to improve the performance of system. The coding is done across OFDM subcarriers rather than OFDM symbols. In this paper, the performance of Space-Frequency (SF block coding for MIMO-OFDM along with different equalizers is investigated. Bit Error Rate (BER analysis is presented using different equalizers and then optimum equalization method is suggested.

  19. An optimal implicit staggered-grid finite-difference scheme based on the modified Taylor-series expansion with minimax approximation method for elastic modeling

    Science.gov (United States)

    Yang, Lei; Yan, Hongyong; Liu, Hong

    2017-03-01

    Implicit staggered-grid finite-difference (ISFD) scheme is competitive for its great accuracy and stability, whereas its coefficients are conventionally determined by the Taylor-series expansion (TE) method, leading to a loss in numerical precision. In this paper, we modify the TE method using the minimax approximation (MA), and propose a new optimal ISFD scheme based on the modified TE (MTE) with MA method. The new ISFD scheme takes the advantage of the TE method that guarantees great accuracy at small wavenumbers, and keeps the property of the MA method that keeps the numerical errors within a limited bound at the same time. Thus, it leads to great accuracy for numerical solution of the wave equations. We derive the optimal ISFD coefficients by applying the new method to the construction of the objective function, and using a Remez algorithm to minimize its maximum. Numerical analysis is made in comparison with the conventional TE-based ISFD scheme, indicating that the MTE-based ISFD scheme with appropriate parameters can widen the wavenumber range with high accuracy, and achieve greater precision than the conventional ISFD scheme. The numerical modeling results also demonstrate that the MTE-based ISFD scheme performs well in elastic wave simulation, and is more efficient than the conventional ISFD scheme for elastic modeling.

  20. A Pedestrian Detection Scheme Using a Coherent Phase Difference Method Based on 2D Range-Doppler FMCW Radar

    Directory of Open Access Journals (Sweden)

    Eugin Hyun

    2016-01-01

    Full Text Available For an automotive pedestrian detection radar system, fast-ramp based 2D range-Doppler Frequency Modulated Continuous Wave (FMCW radar is effective for distinguishing between moving targets and unwanted clutter. However, when a weak moving target such as a pedestrian exists together with strong clutter, the pedestrian may be masked by the side-lobe of the clutter even though they are notably separated in the Doppler dimension. To prevent this problem, one popular solution is the use of a windowing scheme with a weighting function. However, this method leads to a spread spectrum, so the pedestrian with weak signal power and slow Doppler may also be masked by the main-lobe of clutter. With a fast-ramp based FMCW radar, if the target is moving, the complex spectrum of the range- Fast Fourier Transform (FFT is changed with a constant phase difference over ramps. In contrast, the clutter exhibits constant phase irrespective of the ramps. Based on this fact, in this paper we propose a pedestrian detection for highly cluttered environments using a coherent phase difference method. By detecting the coherent phase difference from the complex spectrum of the range-FFT, we first extract the range profile of the moving pedestrians. Then, through the Doppler FFT, we obtain the 2D range-Doppler map for only the pedestrian. To test the proposed detection scheme, we have developed a real-time data logging system with a 24 GHz FMCW transceiver. In laboratory tests, we verified that the signal processing results from the proposed method were much better than those expected from the conventional 2D FFT-based detection method.

  1. A Pedestrian Detection Scheme Using a Coherent Phase Difference Method Based on 2D Range-Doppler FMCW Radar

    Science.gov (United States)

    Hyun, Eugin; Jin, Young-Seok; Lee, Jong-Hun

    2016-01-01

    For an automotive pedestrian detection radar system, fast-ramp based 2D range-Doppler Frequency Modulated Continuous Wave (FMCW) radar is effective for distinguishing between moving targets and unwanted clutter. However, when a weak moving target such as a pedestrian exists together with strong clutter, the pedestrian may be masked by the side-lobe of the clutter even though they are notably separated in the Doppler dimension. To prevent this problem, one popular solution is the use of a windowing scheme with a weighting function. However, this method leads to a spread spectrum, so the pedestrian with weak signal power and slow Doppler may also be masked by the main-lobe of clutter. With a fast-ramp based FMCW radar, if the target is moving, the complex spectrum of the range- Fast Fourier Transform (FFT) is changed with a constant phase difference over ramps. In contrast, the clutter exhibits constant phase irrespective of the ramps. Based on this fact, in this paper we propose a pedestrian detection for highly cluttered environments using a coherent phase difference method. By detecting the coherent phase difference from the complex spectrum of the range-FFT, we first extract the range profile of the moving pedestrians. Then, through the Doppler FFT, we obtain the 2D range-Doppler map for only the pedestrian. To test the proposed detection scheme, we have developed a real-time data logging system with a 24 GHz FMCW transceiver. In laboratory tests, we verified that the signal processing results from the proposed method were much better than those expected from the conventional 2D FFT-based detection method. PMID:26805835

  2. A Pedestrian Detection Scheme Using a Coherent Phase Difference Method Based on 2D Range-Doppler FMCW Radar.

    Science.gov (United States)

    Hyun, Eugin; Jin, Young-Seok; Lee, Jong-Hun

    2016-01-20

    For an automotive pedestrian detection radar system, fast-ramp based 2D range-Doppler Frequency Modulated Continuous Wave (FMCW) radar is effective for distinguishing between moving targets and unwanted clutter. However, when a weak moving target such as a pedestrian exists together with strong clutter, the pedestrian may be masked by the side-lobe of the clutter even though they are notably separated in the Doppler dimension. To prevent this problem, one popular solution is the use of a windowing scheme with a weighting function. However, this method leads to a spread spectrum, so the pedestrian with weak signal power and slow Doppler may also be masked by the main-lobe of clutter. With a fast-ramp based FMCW radar, if the target is moving, the complex spectrum of the range- Fast Fourier Transform (FFT) is changed with a constant phase difference over ramps. In contrast, the clutter exhibits constant phase irrespective of the ramps. Based on this fact, in this paper we propose a pedestrian detection for highly cluttered environments using a coherent phase difference method. By detecting the coherent phase difference from the complex spectrum of the range-FFT, we first extract the range profile of the moving pedestrians. Then, through the Doppler FFT, we obtain the 2D range-Doppler map for only the pedestrian. To test the proposed detection scheme, we have developed a real-time data logging system with a 24 GHz FMCW transceiver. In laboratory tests, we verified that the signal processing results from the proposed method were much better than those expected from the conventional 2D FFT-based detection method.

  3. Comparison of different iterative schemes for ISPH based on Rankine source solution

    Directory of Open Access Journals (Sweden)

    Xing Zheng

    2017-07-01

    Full Text Available Smoothed Particle Hydrodynamics (SPH method has a good adaptability for the simulation of free surface flow problems. There are two forms of SPH. One is weak compressible SPH and the other one is incompressible SPH (ISPH. Compared with the former one, ISPH method performs better in many cases. ISPH based on Rankine source solution can perform better than traditional ISPH, as it can use larger stepping length by avoiding the second order derivative in pressure Poisson equation. However, ISPH_R method needs to solve the sparse linear matrix for pressure Poisson equation, which is one of the most expensive parts during one time stepping calculation. Iterative methods are normally used for solving Poisson equation with large particle numbers. However, there are many iterative methods available and the question for using which one is still open. In this paper, three iterative methods, CGS, Bi-CGstab and GMRES are compared, which are suitable and typical for large unsymmetrical sparse matrix solutions. According to the numerical tests on different cases, still water test, dam breaking, violent tank sloshing, solitary wave slamming, the GMRES method is more efficient than CGS and Bi-CGstab for ISPH method.

  4. Research on Influence of Commercial Features Factor on Decision of Building Energy Conservation Scheme%商务特征指标对建筑节能方案决策的影响研究

    Institute of Scientific and Technical Information of China (English)

    薛汝才; 杨红昌; 柴保双; 邱枫

    2016-01-01

    Decision of building energy conservation scheme is a complicated and integrated process with numerous of indices,and there is no mature theoretical evaluation system or decision method so far. Based on the establishment of evaluation system covering technical and economical feature indexes,the paper introduces commercial feature indexes of policies and regulations risk,business contract risk,project operation cycle,business opportunity cost. Then,takes an electric power dispatching center as an example,builds a comprehensive optimized decision model considering "technology + economy + business" features from the feasibility schemes with CRITIC method,verifies the influence of commercial features factor on the decision of building energy saving conservation scheme,provides reference for the relevant enterprises to carry out decision from feasible investment schemes for energy saving.%建筑节能方案决策是一个复杂的多项指标综合分析过程,尚未形成成熟的决策方法或理论体系.在构建涵盖技术特征、经济特征评价指标体系的基础上,引入政策法规风险、商务合同风险、项目运作周期、商务机会成本等商务特征指标,以某项目为例,采用CRITIC客观权重赋权方法,构建"技术+经济+商务"特征的可行性方案综合优选决策模型,验证商务特征指标对建筑节能改造方案决策的影响,为相关企业进行节能改造可行性投资方案选择提供参考.

  5. Ensemble using different Planetary Boundary Layer schemes in WRF model for wind speed and direction prediction over Apulia region

    Science.gov (United States)

    Tateo, Andrea; Marcello Miglietta, Mario; Fedele, Francesca; Menegotto, Micaela; Monaco, Alfonso; Bellotti, Roberto

    2017-04-01

    The Weather Research and Forecasting mesoscale model (WRF) was used to simulate hourly 10 m wind speed and direction over the city of Taranto, Apulia region (south-eastern Italy). This area is characterized by a large industrial complex including the largest European steel plant and is subject to a Regional Air Quality Recovery Plan. This plan constrains industries in the area to reduce by 10 % the mean daily emissions by diffuse and point sources during specific meteorological conditions named wind days. According to the Recovery Plan, the Regional Environmental Agency ARPA-PUGLIA is responsible for forecasting these specific meteorological conditions with 72 h in advance and possibly issue the early warning. In particular, an accurate wind simulation is required. Unfortunately, numerical weather prediction models suffer from errors, especially for what concerns near-surface fields. These errors depend primarily on uncertainties in the initial and boundary conditions provided by global models and secondly on the model formulation, in particular the physical parametrizations used to represent processes such as turbulence, radiation exchange, cumulus and microphysics. In our work, we tried to compensate for the latter limitation by using different Planetary Boundary Layer (PBL) parameterization schemes. Five combinations of PBL and Surface Layer (SL) schemes were considered. Simulations are implemented in a real-time configuration since our intention is to analyze the same configuration implemented by ARPA-PUGLIA for operational runs; the validation is focused over a time range extending from 49 to 72 h with hourly time resolution. The assessment of the performance was computed by comparing the WRF model output with ground data measured at a weather monitoring station in Taranto, near the steel plant. After the analysis of the simulations performed with different PBL schemes, both simple (e.g. average) and more complex post-processing methods (e.g. weighted average

  6. Do Private Sustainability Standards Contribute to Income Growth and Poverty Alleviation? A Comparison of Different Coffee Certification Schemes in Ethiopia

    Directory of Open Access Journals (Sweden)

    Fikadu Mitiku

    2017-02-01

    Full Text Available Private sustainability standards are increasingly important in food trade with developing countries, but the implications for smallholder farmers are still poorly understood. We analyze the implications of different coffee certification schemes in Ethiopia using cross-sectional survey data, and regression and propensity-score-matching techniques. We find that: Rainforest Alliance (RA and double Fairtrade-Organic (FT-Org certifications are associated with higher incomes and reduced poverty, mainly because of higher prices; Fairtrade (FT certification hardly affects welfare; and Organic (Org certification reduces incomes, chiefly due to lower yields. Cooperative heterogeneity importantly shapes these results. Results imply that private standards may not always deliver what they promise to consumers.

  7. A note on the leap-frog scheme in two and three dimensions. [finite difference method for partial differential equations

    Science.gov (United States)

    Abarbanel, S.; Gottlieb, D.

    1976-01-01

    The paper considers the leap-frog finite-difference method (Kreiss and Oliger, 1973) for systems of partial differential equations of the form du/dt = dF/dx + dG/dy + dH/dz, where d denotes partial derivative, u is a q-component vector and a function of x, y, z, and t, and the vectors F, G, and H are functions of u only. The original leap-frog algorithm is shown to admit a modification that improves on the stability conditions for two and three dimensions by factors of 2 and 2.8, respectively, thereby permitting larger time steps. The scheme for three dimensions is considered optimal in the sense that it combines simple averaging and large time steps.

  8. A conserved developmental patterning network produces quantitatively different output in multiple species of Drosophila.

    Science.gov (United States)

    Fowlkes, Charless C; Eckenrode, Kelly B; Bragdon, Meghan D; Meyer, Miriah; Wunderlich, Zeba; Simirenko, Lisa; Luengo Hendriks, Cris L; Keränen, Soile V E; Henriquez, Clara; Knowles, David W; Biggin, Mark D; Eisen, Michael B; DePace, Angela H

    2011-10-01

    Differences in the level, timing, or location of gene expression can contribute to alternative phenotypes at the molecular and organismal level. Understanding the origins of expression differences is complicated by the fact that organismal morphology and gene regulatory networks could potentially vary even between closely related species. To assess the scope of such changes, we used high-resolution imaging methods to measure mRNA expression in blastoderm embryos of Drosophila yakuba and Drosophila pseudoobscura and assembled these data into cellular resolution atlases, where expression levels for 13 genes in the segmentation network are averaged into species-specific, cellular resolution morphological frameworks. We demonstrate that the blastoderm embryos of these species differ in their morphology in terms of size, shape, and number of nuclei. We present an approach to compare cellular gene expression patterns between species, while accounting for varying embryo morphology, and apply it to our data and an equivalent dataset for Drosophila melanogaster. Our analysis reveals that all individual genes differ quantitatively in their spatio-temporal expression patterns between these species, primarily in terms of their relative position and dynamics. Despite many small quantitative differences, cellular gene expression profiles for the whole set of genes examined are largely similar. This suggests that cell types at this stage of development are conserved, though they can differ in their relative position by up to 3-4 cell widths and in their relative proportion between species by as much as 5-fold. Quantitative differences in the dynamics and relative level of a subset of genes between corresponding cell types may reflect altered regulatory functions between species. Our results emphasize that transcriptional networks can diverge over short evolutionary timescales and that even small changes can lead to distinct output in terms of the placement and number of

  9. A conserved developmental patterning network produces quantitatively different output in multiple species of Drosophila.

    Directory of Open Access Journals (Sweden)

    Charless C Fowlkes

    2011-10-01

    Full Text Available Differences in the level, timing, or location of gene expression can contribute to alternative phenotypes at the molecular and organismal level. Understanding the origins of expression differences is complicated by the fact that organismal morphology and gene regulatory networks could potentially vary even between closely related species. To assess the scope of such changes, we used high-resolution imaging methods to measure mRNA expression in blastoderm embryos of Drosophila yakuba and Drosophila pseudoobscura and assembled these data into cellular resolution atlases, where expression levels for 13 genes in the segmentation network are averaged into species-specific, cellular resolution morphological frameworks. We demonstrate that the blastoderm embryos of these species differ in their morphology in terms of size, shape, and number of nuclei. We present an approach to compare cellular gene expression patterns between species, while accounting for varying embryo morphology, and apply it to our data and an equivalent dataset for Drosophila melanogaster. Our analysis reveals that all individual genes differ quantitatively in their spatio-temporal expression patterns between these species, primarily in terms of their relative position and dynamics. Despite many small quantitative differences, cellular gene expression profiles for the whole set of genes examined are largely similar. This suggests that cell types at this stage of development are conserved, though they can differ in their relative position by up to 3-4 cell widths and in their relative proportion between species by as much as 5-fold. Quantitative differences in the dynamics and relative level of a subset of genes between corresponding cell types may reflect altered regulatory functions between species. Our results emphasize that transcriptional networks can diverge over short evolutionary timescales and that even small changes can lead to distinct output in terms of the placement and

  10. Finite Boltzmann schemes

    NARCIS (Netherlands)

    Sman, van der R.G.M.

    2006-01-01

    In the special case of relaxation parameter = 1 lattice Boltzmann schemes for (convection) diffusion and fluid flow are equivalent to finite difference/volume (FD) schemes, and are thus coined finite Boltzmann (FB) schemes. We show that the equivalence is inherent to the homology of the

  11. Anti-tumor activities of peptides corresponding to conserved complementary determining regions from different immunoglobulins.

    Science.gov (United States)

    Figueiredo, Carlos R; Matsuo, Alisson L; Massaoka, Mariana H; Polonelli, Luciano; Travassos, Luiz R

    2014-09-01

    Short synthetic peptides corresponding to sequences of complementarity-determining regions (CDRs) from different immunoglobulin families have been shown to induce antimicrobial, antiviral and antitumor activities regardless of the specificity of the original monoclonal antibody (mAb). Presently, we studied the in vitro and in vivo antitumor activity of synthetic peptides derived from conserved CDR sequences of different immunoglobulins against human tumor cell lines and murine B16F10-Nex2 melanoma aiming at the discovery of candidate molecules for cancer therapy. Four light- and heavy-chain CDR peptide sequences from different antibodies (C36-L1, HA9-H2, 1-H2 and Mg16-H2) showed cytotoxic activity against murine melanoma and a panel of human tumor cell lineages in vitro. Importantly, they also exerted anti-metastatic activity using a syngeneic melanoma model in mice. Other peptides (D07-H3, MN20v1, MS2-H3) were also protective against metastatic melanoma, without showing significant cytotoxicity against tumor cells in vitro. In this case, we suggest that these peptides may act as immune adjuvants in vivo. As observed, peptides induced nitric oxide production in bone-marrow macrophages showing that innate immune cells can also be modulated by these CDR peptides. The present screening supports the search in immunoglobulins of rather frequent CDR sequences that are endowed with specific antitumor properties and may be candidates to be developed as anti-cancer drugs.

  12. Anti-ischemic effect of chronic oestrogen replacement therapy alone or in combination with medroxyprogesterone acetate in different replacement schemes.

    Science.gov (United States)

    Cerquetani, E; Leonardo, F; Pagnotta, P; Galetta, P; Onorati, D; Fini, M; Rosano, G M

    2001-09-28

    Oestrogen replacement therapy in postmenopausal women has a protective effect upon the cardiovascular system and improves exercise-induced myocardial ischemia. Although in hormone replacement schemes progestins are required to reduce the likelihood of uterine malignancies, little is known on the cardiovascular effect of progestins. The purpose of this study was to evaluate the effect of oestrogen replacement alone and two different estrogen-progestin replacement therapy schemes upon exercise induced myocardial ischemia. The study population included 18 female menopausal patients with coronary artery disease. After a baseline exercise test patients received conjugated equine estrogens (CEE) 0.625 mg alone for 30 days when they underwent a second exercise test and were randomized to receive in a cross-over design medroxyprogesterone acetate (MPA) either in continuous combined therapy (2.5 mg/daily) for 28 days or in cyclical therapy (10 mg o.d. from day 16 to day 28). After CEE alone two patients with a previously positive exercise test showed a negative exercise test. CEE increased time to 1 mm ST compared to baseline (352+/-185 vs 265+/-133 s, Pexercise test was negative after CEE the test remained negative during continuous combined MPA therapy while become positive during cyclical MPA. CEE+continuous combined MPA increased both time to 1 mm ST and exercise time compared to baseline (386+/-165 vs 265+/-133 s, Pexercise time (268+/-164 vs 265+/-133 s, P=NS and 455+/-223 vs 465+/-186 s, P=NS, respectively). Continuous combined therapy with CEE+MPA improves exercise-induced myocardial ischemia in female patients with coronary artery disease while the beneficial effect of CEE is reduced by cyclical therapy.

  13. 铁磁链Landau-Lifshitz方程的显式差分法%AN EXPLICIT FINITE DIFFERENCE SCHEME FOR THELANDAU-LIFSHITZ EQUATION OF THEFERROMAGNETIC SPIN CHAIN

    Institute of Scientific and Technical Information of China (English)

    万桂华

    2000-01-01

    In this paper, the Landau-Lifshitz equation with periodic initial boundary valued problem which is govnered by ()/(t)=-1 ( )+2( ) is discreted by using the Euler-forword finite difference method. The proposed scheme is explicit so that the parallel algorithm can be used to simulate numerically on computer. Moreove, the convergence and stability of the proposed scheme are proved by the finite extensive method of the nonlinear function. Finally, the numerical experiments are provided to check the theoritical results.

  14. Scheme Program Documentation Tools

    DEFF Research Database (Denmark)

    Nørmark, Kurt

    2004-01-01

    This paper describes and discusses two different Scheme documentation tools. The first is SchemeDoc, which is intended for documentation of the interfaces of Scheme libraries (APIs). The second is the Scheme Elucidator, which is for internal documentation of Scheme programs. Although the tools...... are separate and intended for different documentation purposes they are related to each other in several ways. Both tools are based on XML languages for tool setup and for documentation authoring. In addition, both tools rely on the LAML framework which---in a systematic way---makes an XML language available...

  15. Differences in quantitative characteristics of intracranial pressure in hydrocephalic children treated surgically or conservatively.

    Science.gov (United States)

    Eide, Per Kristian; Due-Tønnessen, Bernt; Helseth, Eirik; Lundar, Tryggve

    2002-06-01

    This study reports the results of quantitative analysis of continuous intracranial pressure (ICP) recordings in 33 hydrocephalic children. The aim of the study was to compare the exact numbers of increases in ICP during sleep or the awake state in hydrocephalic children who were treated either surgically or conservatively. At the time of ICP monitoring, the ICP curves were assessed by the calculation of mean ICP and visual inspection for the detection of plateau waves. Quantitative analysis was performed with the software Sensometrics Pressure Analyser, which presented the ICP curve as a matrix of numbers of ICP elevations of different levels (20-40 mm Hg) and durations (0.5-20 min). In each case, the numbers of ICP elevations were standardized to 10 h of recording time, providing the opportunity for comparisons of ICP curves between individuals. Compared to the surgery group, there was a rather high number of ICP elevations of 20 mm Hg of various durations in the nonsurgery group, e.g. ICP elevations of 20 mm Hg lasting 10 min occurred in 13 of 19 children (68%) in the nonsurgery group. There was no apparent relationship between ICP and age or between the size of the cerebral ventricles and ICP. In children with hydrocephalus, the presentation of the ICP data as a matrix of ICP elevations of different levels and durations may enhance the informative value of continuous ICP monitoring, as compared to the calculation of mean ICP and visual detection of plateau waves. Copyright 2002 S. Karger AG, Basel

  16. Comparison of two different sea-salt aerosol schemes as implemented in air quality models applied to the Mediterranean Basin

    Directory of Open Access Journals (Sweden)

    P. Jiménez-Guerrero

    2011-05-01

    Full Text Available A number of attempts have been made to incorporate sea-salt aerosol (SSA source functions in chemistry transport models with varying results according to the complexity of the scheme considered. This contribution compares the inclusion of two different SSA algorithms in two chemistry transport models: CMAQ and CHIMERE. The main goal is to examine the differences in average SSA mass and composition and to study the seasonality of the prediction of SSA when applied to the Mediterranean area with high resolution for a reference year. Dry and wet deposition schemes are also analyzed to better understand the differences observed between both models in the target area. The applied emission algorithm in CHIMERE uses a semi-empirical formulation which obtains the surface emission rate of SSA as a function of the particle size and the surface wind speed raised to the power 3.41. The emission parameterization included within CMAQ is somehow more sophisticated, since fluxes of SSA are corrected with relative humidity. In order to evaluate their strengths and weaknesses, the participating algorithms as implemented in the chemistry transport models were evaluated against AOD measurements from Aeronet and available surface measurements in Southern Europe and the Mediterranean area, showing biases around −0.002 and −1.2 μg m−3, respectively. The results indicate that both models represent accurately the patterns and dynamics of SSA and its non-uniform behavior in the Mediterranean basin, showing a strong seasonality. The levels of SSA strongly vary across the Western and the Eastern Mediterranean, reproducing CHIMERE higher annual levels in the Aegean Sea (12 μg m−3 and CMAQ in the Gulf of Lion (9 μg m−3. The large difference found for the ratio PM2.5/total SSA in CMAQ and CHIMERE is also investigated. The dry and wet removal rates are very similar for both models despite the different schemes

  17. Small amplitude Dynamic AFM: quantifying interactions with different tip detection and excitation schemes in presence of additional resonances

    CERN Document Server

    Costa, Luca

    2014-01-01

    Quantifying the tip-sample interaction at the nanoscale in Amplitude Modulation mode AFM is challenging, especially when measuring in liquids. Here, we derive formulas for the tip-sample conservative and dissipative interactions and investigate the effect that spurious resonances have on the measured interaction. Both direct and acoustic excitation are considered. We also highlight the differences between measuring directly the tip position or the cantilever deflection. We show that, when probing the tip-sample forces, the acoustically excited cantilever behavior is insensitive to spurious resonances as long as the measured signal corresponds to the tip position, or if the excitation force is correctly taken into account. Since the effective excitation force may depend on the presence of such spurious resonances, we consider the cases where the frequency is kept constant during the measurement so that the proportionality between excitation signal and actual excitation force is kept constant. With the present ...

  18. ASSESSMENT OF A CENTRAL DIFFERENCE FINITE VOLUME SCHEME FOR MODELING OF CAVITATING FLOWS USING PRECONDITIONED MULTIPHASE EULER EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    HEJRANFAR Kazem; FATTAH-HESARY Kasra

    2011-01-01

    A numerical treatment for the prediction of cavitating flows is presented and assessed.The algorithm uses the preconditioned multiphase Euler equations with appropriate mass transfer terms.A central difference finite volume scheme with suitable dissipation terms to account for density jumps across the cavity interface is shown to yield an effective method for solving the multiphase Euler equations.The Euler equations are utilized herein for the cavitation modeling, because some certain characteristics of cavitating flows can be obtained using the solution of this system of equations with relative low computational effort.In addition, the Euler equations are appropriate for the assessment of the numerical method used, because of the sensitivity of the solution to the numerical instabilities.For this reason, a sensitivity study is conducted to evaluate the effects of various parameters, such as numerical dissipation coefficients and grid size, on the accuracy and performance of the solution.The computations are performed for steady cavitating flows around the NACA 0012 and NACA 66 (MOD) hydrofoils and also an axisymmetric hemispherical fore-body under different conditions and the results are compared with the available numerical and experimental data.The solution procedure presented is shown to be accurate and efficient for predicting steady sheet- and super-cavitation for 2D/axisymmetric geometries.

  19. Different Seed Selection and Conservation Practices for Fresh Market and Dried Chile Farmers in Aguascalientes, Mexico.

    Science.gov (United States)

    Kraft, Kraig H; de Jesús Luna-Ruíz, José; Gepts, Paul

    2010-12-01

    Different Seed Selection and Conservation Practices for Fresh Market and Dried Chile Farmers in Aguascalientes, Mexico. The process of selecting and saving seed is the most basic and oldest of agricultural practices. In today's modern and highly capital-intensive agriculture, seeds are often treated like another chemical input. This study sought to examine seed selection and saving practices among chile farmers in Aguascalientes, Mexico, where both industrial and traditional agriculture are practiced. We observed a clear division among farmers who plant chile peppers commercially. Sixty-eight chile pepper farmers were surveyed in order to document seed selection and saving practices. Fifteen respondents (22%) planted chile peppers destined for the fresh market and all utilized purchased commercial seed of F1 hybrid varieties. Fifty-three farmers (78%) planted chiles to be dried and either saved their own or purchased seeds that others had saved and selected. Farmers who saved their own seed sought to maintain an ideotype, rather than directionally select for certain traits, much like Cleveland et al. (2000) chronicled in central Mexican maize farmers. Farmers would benefit from a participatory plant-breeding program in order to maintain productive seed stock for the continued cultivation of dried chile pepper in the state.

  20. Theoretical characterization of photoinduced electron transfer in rigidly linked donor-acceptor molecules: the fragment charge difference and the generalized Mulliken-Hush schemes

    Science.gov (United States)

    Lee, Sheng-Jui; Chen, Hung-Cheng; You, Zhi-Qiang; Liu, Kuan-Lin; Chow, Tahsin J.; Chen, I.-Chia; Hsu, Chao-Ping

    2010-10-01

    We calculate the electron transfer (ET) rates for a series of heptacyclo[6.6.0.02,6.03,13.014,11.05,9.010,14]-tetradecane (HCTD) linked donor-acceptor molecules. The electronic coupling factor was calculated by the fragment charge difference (FCD) [19] and the generalized Mulliken-Hush (GMH) schemes [20]. We found that the FCD is less prone to problems commonly seen in the GMH scheme, especially when the coupling values are small. For a 3-state case where the charge transfer (CT) state is coupled with two different locally excited (LE) states, we tested with the 3-state approach for the GMH scheme [30], and found that it works well with the FCD scheme. A simplified direct diagonalization based on Rust's 3-state scheme was also proposed and tested. This simplified scheme does not require a manual assignment of the states, and it yields coupling values that are largely similar to those from the full Rust's approach. The overall electron transfer (ET) coupling rates were also calculated.

  1. 一维非线性 Schrödinger 方程参数形式差分格式的研究%A parameter difference scheme for nonlinear Schrödinger equation in one dimension

    Institute of Scientific and Technical Information of China (English)

    李鑫

    2015-01-01

    对一维非线性 Schrdinger 方程构造参数形式的差分格式进行研究。运用能量方法证明了方程的离散守恒律,并通过先验估计验证了格式的收敛性和稳定性。数值实验结果表明,差分格式的收敛阶为 O(h 2+τ2),格式的效果明显优于先前格式。%A parameter finite difference scheme is proposed for nonlinear Schrdinger equation in one dimension. Then the discrete conservation law is proved by the energy method.The stability and convergence are demonstrated by the prior estimation.The numerical results have been carried out to confirm the convergence order is O(h 2 +τ2 ). Moreover,the new scheme shows the superiority through comparing with the scheme before.

  2. Conservation Station and Beyond: Experiences at Disney's Animal Kingdom That Make a Difference.

    Science.gov (United States)

    Ogden, Jackie; Lehnhardt, Kathy; Mellen, Jill; Dierking, Lynn; Adelman, Leslie; Burks, Kyle; Miller, Lance

    2001-01-01

    Describes a five-year plan for educational research and evaluation at the Disney Animal Kingdom. Focuses on conservation-related issues and presents some of the preliminary results from the study of visitor attitudes. (DDR)

  3. Improving the Stability Problem of the Finite Difference Scheme for Reaction-diffusion Equation%提高反应—扩散方程有限差分格式的稳定性问题

    Institute of Scientific and Technical Information of China (English)

    徐琛梅

    2008-01-01

    This paper deals with the special nonlinear reaction-diffusion equation.The finite difference scheme with incremental unknowns approximating to the differential equation (2.1) is set up by means of introducing incremental unknowns methods.Through the stability analyzing for the scheme,it was shown that the stability conditions of the finite difference schemes with the incremental unknowns are greatly improved when compared with the stability conditions of the corresponding classic difference scheme.

  4. Human perception of the conservation and biodiversity state of forest remnants under different levels of urbanization

    Directory of Open Access Journals (Sweden)

    Thallita Oliveira de Grande

    2016-07-01

    Full Text Available Human perception of local environmental biodiversity and conservation may provide another dimension to understanding the ecology of urban ecosystems. This perception can vary according to the environmental urbanization level and may contribute towards its conservation. We investigated the relationship between the human perception of the conservation and state of animal richness in urban remnants and level of landscape urbanization, and between the human perception of animal richness and the remnants’ area. In addition, we tested the effectiveness of interviews as the means for evaluating animal richness. The subjects' perception of the conservation of remnants did not correlate with the level of urbanization. Richness was reported as high and varied with the remnant’s area - indicating maintenance of a possible species-area relationship in the studied landscape - but did not correlate with the level of urbanization. Urbanization can standardize the popular knowledge about conservation. Interviews with local residents proved to bring efficient insights into urban animal richness, especially for primates, and can be supplemented by camera-trapping. Human perception, obtained through interviews, is relevant and useful for the description of ecological aspects of urban regions and supports environmental awareness, actions, research projects, and management for conservation purposes.

  5. Optimization of ITS Construction Scheme for Road Network under the Restriction of Different Transports’ Passenger Person-Kilometers

    Directory of Open Access Journals (Sweden)

    Ming-wei Li

    2017-01-01

    Full Text Available Diversified transport modes and increased personal transportation demands have increased in urban traffic problems such as traffic congestion and environmental pollution. To cope with traffic problems, advanced transportation technologies are being developed as intelligent transportation system (ITS. There is a growing trend to coordinate varying kinds of transportation modes. However, the effective construction and application of ITS in urban traffic can be affected by many factors, such as transport mode. Therefore, how to reasonably construct ITS by consideration of different transport modes’ characteristics and requirements is an important research challenge. Additionally, both costs and negative effects must be minimized and application efficiency is required to be optimal in the construction process. To address these requirements, a multiobjective optimization model and a fuzzy selecting optimum model were combined to study the construction scheme based on optimization results. The empirical analysis of Beijing, China, suggested several considerations for improvements to future road network ITS construction with controlled costs. Finally, guidelines are proposed to facilitate ITS construction, improve ITS application efficiency, and transform and innovate strategies to cope with urban traffic.

  6. Optimal staggered-grid finite-difference schemes by combining Taylor-series expansion and sampling approximation for wave equation modeling

    Science.gov (United States)

    Yan, Hongyong; Yang, Lei; Li, Xiang-Yang

    2016-12-01

    High-order staggered-grid finite-difference (SFD) schemes have been universally used to improve the accuracy of wave equation modeling. However, the high-order SFD coefficients on spatial derivatives are usually determined by the Taylor-series expansion (TE) method, which just leads to great accuracy at small wavenumbers for wave equation modeling. Some conventional optimization methods can achieve high accuracy at large wavenumbers, but they hardly guarantee the small numerical dispersion error at small wavenumbers. In this paper, we develop new optimal explicit SFD (ESFD) and implicit SFD (ISFD) schemes for wave equation modeling. We first derive the optimal ESFD and ISFD coefficients for the first-order spatial derivatives by applying the combination of the TE and the sampling approximation to the dispersion relation, and then analyze their numerical accuracy. Finally, we perform elastic wave modeling with the ESFD and ISFD schemes based on the TE method and the optimal method, respectively. When the appropriate number and interval for the sampling points are chosen, these optimal schemes have extremely high accuracy at small wavenumbers, and can also guarantee small numerical dispersion error at large wavenumbers. Numerical accuracy analyses and modeling results demonstrate the optimal ESFD and ISFD schemes can efficiently suppress the numerical dispersion and significantly improve the modeling accuracy compared to the TE-based ESFD and ISFD schemes.

  7. Using 137Cs technique to quantify soil conservation capacities of different ecosystems in Wolong Natural Reserve, southwestern China

    Institute of Scientific and Technical Information of China (English)

    GAO Jun; OUYANG ZhiYun

    2007-01-01

    Reliable information about soil conservation capacities of different natural ecosystems is an important reference for the design of targeted erosion and sediment control strategies. The objective of this paper is to quantify the soil conservation capacities of different natural ecosystems that can represent different climatic zones. The 137Cs technique has been used to estimate soil redistribution rates in different natural ecosystems over the past 40 years in Wolong Nature Reserve. The reserve, transiting from the Chengdu plain to the Qinghai-Tibet plateau, maintains rich ecosystems from subtropical to frigid.The net soil erosion rates of 5 selected ecosystems that represent a warm coniferous-broadleaf-mixed forest, a cold-resistant deciduous taiga forest, a cold-resistant shrub, an evergreen cold-resistant taiga servation capacities are reversed in order. The reference inventories for 137Cs in different ecosystems velop effective erosion and sediment strategies in areas with similar climates should consider natural ecosystem types.

  8. Primate Conservation--An Evaluation of Two Different Educational Programs in Germany

    Science.gov (United States)

    Seybold, Brigitte; Braunbeck, Thomas; Randler, Christoph

    2014-01-01

    Nearly all primate species are globally threatened. Conservation approaches need to focus on local people and users of resources from the habitats of the apes. Students worldwide should become aware of the context and relationships in school, and they should change their usage and behaviour as the ultimate goals. This study explored the…

  9. Analysing the interactions between renewable energy promotion and energy efficiency support schemes: The impact of different instruments and design elements

    Energy Technology Data Exchange (ETDEWEB)

    Rio, Pablo del, E-mail: pablo.delrio@cchs.csic.e [Instituto de Politicas y Bienes Publicos, Consejo Superior de Investigaciones Cientificas (CSIC), C/Albasanz 26-28, 28037 Madrid (Spain)

    2010-09-15

    CO{sub 2} emissions reduction, renewable energy deployment and energy efficiency are three main energy/environmental goals, particularly in Europe. Their relevance has led to the implementation of support schemes in these realms. Their coexistence may lead to overlaps, synergies and conflicts between them. The aim of this paper is to analyse the interactions between energy efficiency measures and renewable energy promotion, whereas previous analyses have focused on the interactions between emissions trading schemes (ETS) and energy efficiency measures and ETS and renewable energy promotion schemes. Furthermore, the analysis in this paper transcends the 'certificate' debate (i.e., tradable green and white certificates) and considers other instruments, particularly feed-in tariffs for renewable electricity. The goal is to identify positive and negative interactions between energy efficiency and renewable electricity promotion and to assess whether the choice of specific instruments and design elements within those instruments affects the results of the interactions.

  10. Analysing the interactions between renewable energy promotion and energy efficiency support schemes. The impact of different instruments and design elements

    Energy Technology Data Exchange (ETDEWEB)

    Del Rio, Pablo [Instituto de Politicas y Bienes Publicos, Consejo Superior de Investigaciones Cientificas (CSIC), C/Albasanz 26-28, 28037 Madrid (Spain)

    2010-09-15

    CO{sub 2} emissions reduction, renewable energy deployment and energy efficiency are three main energy/environmental goals, particularly in Europe. Their relevance has led to the implementation of support schemes in these realms. Their coexistence may lead to overlaps, synergies and conflicts between them. The aim of this paper is to analyse the interactions between energy efficiency measures and renewable energy promotion, whereas previous analyses have focused on the interactions between emissions trading schemes (ETS) and energy efficiency measures and ETS and renewable energy promotion schemes. Furthermore, the analysis in this paper transcends the certificate debate (i.e., tradable green and white certificates) and considers other instruments, particularly feed-in tariffs for renewable electricity. The goal is to identify positive and negative interactions between energy efficiency and renewable electricity promotion and to assess whether the choice of specific instruments and design elements within those instruments affects the results of the interactions. (author)

  11. Evaluation of different interpolation schemes for precipitation and reference evapotranspiration and the impact on simulated large-scale water balance in Slovenia

    Science.gov (United States)

    He, Qianwen; Molkenthin, Frank; Wendland, Frank; Herrmann, Frank

    2016-04-01

    Precipitation and reference evapotranspiration (ET0) are two main climate input components for hydrological models, which are often recorded or calculated based on measuring stations. Interpolation schemes are implemented to regionalize data from measuring stations for distributed hydrological models. This study had been conducted for 5 months, with the aim of: (1) evaluating three interpolation schemes for precipitation and reference evapotranspiration (ET0); (2) assessing the impact of the interpolation schemes on actual evapotranspiration and total runoff simulated by a distributed large-scale water balance model - mGROWA. The study case was the Republic of Slovenia, including a high variability in topography and climatic conditions, with daily meteorological data measured in 20 stations for a period of 44 years. ET0 were computed by both FAO Penman-Monteith equation and Hargreaves equation. The former equation is recommended as the standard equation, while the ET0 calculated by the latter one for Slovenia had a certain deviation (+150 mm/a) from it. Ordinary Kriging, Regression Kriging and Linear Regression were selected to regionalize precipitation and ET0. Reliability of the three interpolation schemes had been assessed based on the residual obtained from cross-validation. Monthly regionalized precipitation and ET0 were subsequently used as climate input for mGROWA model simulation. Evaluation of the interpolation schemes showed that the application of Regression Kriging and Linear Regression led to an acceptable interpolation result for reference evapotranspiration, especially in case the FAO Penman-Monteith equation was used. On the other hand, Regression Kriging also provided a more convincing interpolated result for precipitation. Meanwhile, mGROWA simulation results were affected by climate input data sets generated by applying difference interpolation schemes. Therefore, it is essential to select an appropriate interpolation scheme, in order to generate

  12. Studies of Inviscid Flux Schemes for Acoustics and Turbulence Problems

    Science.gov (United States)

    Morris, Chris

    2013-01-01

    Five different central difference schemes, based on a conservative differencing form of the Kennedy and Gruber skew-symmetric scheme, were compared with six different upwind schemes based on primitive variable reconstruction and the Roe flux. These eleven schemes were tested on a one-dimensional acoustic standing wave problem, the Taylor-Green vortex problem and a turbulent channel flow problem. The central schemes were generally very accurate and stable, provided the grid stretching rate was kept below 10%. As near-DNS grid resolutions, the results were comparable to reference DNS calculations. At coarser grid resolutions, the need for an LES SGS model became apparent. There was a noticeable improvement moving from CD-2 to CD-4, and higher-order schemes appear to yield clear benefits on coarser grids. The UB-7 and CU-5 upwind schemes also performed very well at near-DNS grid resolutions. The UB-5 upwind scheme does not do as well, but does appear to be suitable for well-resolved DNS. The UF-2 and UB-3 upwind schemes, which have significant dissipation over a wide spectral range, appear to be poorly suited for DNS or LES.

  13. A High Resolution Low Dissipation Hybrid Scheme for Compressible Flows

    Institute of Scientific and Technical Information of China (English)

    YU Jian; YAN Chao; JIANG Zhenhua

    2011-01-01

    In this paper,an efficient hybrid shock capturing scheme is proposed to obtain accurate results both in the smooth region and around discontinuities for compressible flows.The hybrid algorithm is based on a fifth-order weighted essentially non-oscillatory (WENO) scheme in the finite volume form to solve the smooth part of the flow field,which is coupled with a characteristic-based monotone upstream-centered scheme for conservation laws(MUSCL) to capture discontinuities.The hybrid scheme is intended to combine high resolution of MUSCL scheme and low dissipation of WENO scheme.The two ingredients in this hybrid scheme are switched with an indicator.Three typical indicators are chosen and compared.MUSCL and WENO are both shock capturing schemes making the choice of the indicator parameter less crucial.Several test cases are carried out to investigate hybrid scheme with different indicators in terms of accuracy and efficiency.Numerical results demonstrate that the hybrid scheme in the present work performs well in a broad range of problems.

  14. Using 137Cs technique to quantify soil conservation capacities of different ecosystems in Wolong Natural Reserve, southwestern China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Reliable information about soil conservation capacities of different natural ecosystems is an important reference for the design of targeted erosion and sediment control strategies. The objective of this paper is to quantify the soil conservation capacities of different natural ecosystems that can represent dif-ferent climatic zones. The 137Cs technique has been used to estimate soil redistribution rates in differ-ent natural ecosystems over the past 40 years in Wolong Nature Reserve. The reserve, transiting from the Chengdu plain to the Qinghai-Tibet plateau, maintains rich ecosystems from subtropical to frigid. The net soil erosion rates of 5 selected ecosystems that represent a warm coniferous-broadleaf-mixed forest, a cold-resistant deciduous taiga forest, a cold-resistant shrub, an evergreen cold-resistant taiga forest, and an alpine meadow are 0.17, 0.16, 0.13, 0.11 and 0.06 kg·m-2·a-1, respectively. Their soil con-servation capacities are reversed in order. The reference inventories for 137Cs in different ecosystems range from 1658 to 3707 Bq·m-2 with the altitude. Results of this study indicate that any attempt to de-velop effective erosion and sediment strategies in areas with similar climates should consider natural ecosystem types.

  15. Conservative Management of Invasive Placentation: Two Cases with Different Surgical Approaches.

    Science.gov (United States)

    Fay, Emily E; Norquist, Barbara; Jolley, Jennifer; Hardesty, Melissa

    2016-04-01

    Background When placenta accreta complicates a delivery, the typical management is to perform a cesarean hysterectomy. Other management strategies, including leaving the placenta in situ, have been attempted and supported in some cases. This may allow for an interval hysterectomy, which can potentially decrease average blood loss and/or allow a minimally invasive approach to the hysterectomy. Cases We present two cases of women with invasive placentation managed conservatively with interval hysterectomy. One woman was managed with robotic-assisted laparoscopic surgery and the other with an open surgical approach. Conclusion These cases highlight the successful use of conservative management for invasive placentation in two stable patients and showcase the novel use of a robotic-assisted laparoscopic surgery for management of invasive placentation.

  16. Convertible Proxy Signcryption Scheme

    Institute of Scientific and Technical Information of China (English)

    李继国; 李建中; 曹珍富; 张亦辰

    2004-01-01

    In 1996, Mambo et al introduced the concept of proxy signature. However, proxy signature can only provide the delegated authenticity and cannot provide confidentiality. Recently, Gamage et al and Chan and Wei proposed different proxy signcryption schemes respectively, which extended the concept of proxy signature.However, only the specified receiver can decrypt and verify the validity of proxy signcryption in their schemes.To protect the receiver' s benefit in case of a later dispute, Wu and Hsu proposed a convertible authenticated encryption scheme, which carn enable the receiver to convert signature into an ordinary one that can be verified by anyone. Based on Wu and Hsu' s scheme and improved Kim' s scheme, we propose a convertible proxy signcryption scheme. The security of the proposed scheme is based on the intractability of reversing the one-way hash function and solving the discrete logarithm problem. The proposed scheme can satisfy all properties of strong proxy signature and withstand the public key substitution attack and does not use secure channel. In addition, the proposed scheme can be extended to convertible threshold proxy signcryption scheme.

  17. Comparison of different grading schemes in InGaAs metamorphic buffers on GaAs substrate: Tilt dependence on cross-hatch irregularities

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Rahul, E-mail: rkp203@gmail.com [Advanced Technology Development Centre, Indian Institute of Technology, Kharagpur 721302 (India); Bag, Ankush [Advanced Technology Development Centre, Indian Institute of Technology, Kharagpur 721302 (India); Mukhopadhyay, Partha [Rajendra Mishra School of Engineering Entrepreneurship, Indian Institute of Technology, Kharagpur 721302 (India); Das, Subhashis [Advanced Technology Development Centre, Indian Institute of Technology, Kharagpur 721302 (India); Biswas, Dhrubes [Department of Electronics & Electrical Communication Engineering, Indian Institute of Technology, Kharagpur 721 302 (India)

    2015-12-01

    Highlights: • InGaAs graded MBs with different grading scheme has been grown by MBE on GaAs. • Continuously graded MB exhibits smoother surface morphology. • Grading scheme has been found to have little impact on lattice relaxation. • Grading schemeaffects the lattice tilt significantly. • Cross-hatch surface irregularities affect the crystallographic tilt. - Abstract: InGaAs graded metamorphic buffers (MBs) with different grading strategies have been grown by molecular beam epitaxy (MBE) on GaAs (0 0 1) substrate. A detailed comparative analysis of surface using atomic force microscopy (AFM), and bulk properties using high resolution X-ray diffraction (HRXRD) and room temperature photoluminescence (RTPL) of grown MBs have been presented to comprehend the effectiveness of different grading scheme on InGaAs MBs. Conventional, statistical and fractal analysis on measured AFM data has been performed for in-depth investigation of these surfaces. The grading scheme has been found to have little impact on residual strain while it affects the epitaxial tilt significantly. Moreover, the tilt has been found to depend on growth front irregularities. Tilt magnitude in a graded MB has been found to vary with composition while tilt azimuth has been found to be almost same in the graded layers. PL Intensity and a shift in the PL peaks have been used to study the quality of the MB and residual strain comparatively.

  18. Using 137Cs technique to quantify soil conservation capacities of different ecosystems in Wolong Natural Reserve, southwestern China.

    Science.gov (United States)

    Gao, Jun; Ouyang, ZhiYun

    2007-08-01

    Reliable information about soil conservation capacities of different natural ecosystems is an important reference for the design of targeted erosion and sediment control strategies. The objective of this paper is to quantify the soil conservation capacities of different natural ecosystems that can represent different climatic zones. The (137)Cs technique has been used to estimate soil redistribution rates in different natural ecosystems over the past 40 years in Wolong Nature Reserve. The reserve, transiting from the Chengdu plain to the Qinghai-Tibet plateau, maintains rich ecosystems from subtropical to frigid. The net soil erosion rates of 5 selected ecosystems that represent a warm coniferous-broadleaf-mixed forest, a cold-resistant deciduous taiga forest, a cold-resistant shrub, an evergreen cold-resistant taiga forest, and an alpine meadow are 0.17, 0.16, 0.13, 0.11 and 0.06 kg x m(-2) x a(-1), respectively. Their soil conservation capacities are reversed in order. The reference inventories for (137)Cs in different ecosystems range from 1658 to 3707 Bq x m(-2) with the altitude. Results of this study indicate that any attempt to develop effective erosion and sediment strategies in areas with similar climates should consider natural ecosystem types.

  19. Energy-saving PPM schemes for WSNs

    Institute of Scientific and Technical Information of China (English)

    TANG QiuLing; YANG LiuQing; QIN TuanFa; ZHANG ShuYi

    2008-01-01

    Energy conservation is a critical problem in recenlly-emerging wireless sensor networks (WSNs). Pulse position modulation (PPM), as an exploring-worthy modulation format for energy efficiency, is tailored for WSNs into two schemes, mono-mode PPM and multi-mode PPM, in this paper. Resorting to an idealized system model and a practical system model, which combine the power consump-tions in transmission and reception modules of nodes with the idealized and real-istic battery characteristics, the battery energy efficiencies of mono-mode PPM and multi-mode PPM are evaluated and compared. To minimize the battery energy consumption (BEC), these schemes are further optimized in terms of constellation size M for a link in path-loss channels. Our analytical and numerical results show that considerable energy can be saved by multi-mode PPM; and the optimization performances of these schemes are noticeable at various communication dis-tances though their optimization properties are different.

  20. Performance of RegCM-4.3 over the Caribbean region using different configurations of the Tiedtke convective parameterization scheme

    Directory of Open Access Journals (Sweden)

    Daniel Martínez-Castro

    2016-10-01

    Full Text Available A sensitivity study about the performance of the RegCM-4.3 regional climate model, driven by ERA Interim reanalysis was conducted for a domain including the Caribbean, with horizontal resolution of 50 km from year 2000 to 2001. Sixteen configurations of the model, including variations in the parameters of the Tiedtke convective scheme were tested. The performance of the model using these configurations was compared with data and with simulations using Emanuel (EM and Grell over land-Emanuel over sea (GE convective parameterization schemes. Global datasets of temperature and precipitation and quality controlled data form the weather station networks of Cuba, Jamaica and the Dominican Republic were used as reference. After an analysis of the simulated precipitation fields, some of the configurations were discarded and four of them were chosen to evaluate the representation by the model of the main climatological features of the region. The chosen configurations simulate the general wind and precipitation patterns reasonably well, and at the same time, the seasonal diurnal cycles and the Caribbean low level jet, but they showed different skill in reproducing the particular features of the regional climate. For the rainy season GE shows the best performance, while EM and the default Tiedtke scheme (TI widely overestimate precipitation in the Pacific coast of Central America, whereas for the dry season, the Tiedtke scheme underestimates precipitation, but after tuning parameters biases were reduced. TI scheme showed the best representation of the precipitation seasonal cycle, while the diurnal circle was best reproduced by the GE scheme. Temperature fields were best simulated by Tiedtke configurations, as the area with negative bias was reduced.

  1. On the Derivation of Highest-Order Compact Finite Difference Schemes for the One- and Two-Dimensional Poisson Equation with Dirichlet Boundary Conditions

    KAUST Repository

    Settle, Sean O.

    2013-01-01

    The primary aim of this paper is to answer the question, What are the highest-order five- or nine-point compact finite difference schemes? To answer this question, we present several simple derivations of finite difference schemes for the one- and two-dimensional Poisson equation on uniform, quasi-uniform, and nonuniform face-to-face hyperrectangular grids and directly prove the existence or nonexistence of their highest-order local accuracies. Our derivations are unique in that we do not make any initial assumptions on stencil symmetries or weights. For the one-dimensional problem, the derivation using the three-point stencil on both uniform and nonuniform grids yields a scheme with arbitrarily high-order local accuracy. However, for the two-dimensional problem, the derivation using the corresponding five-point stencil on uniform and quasi-uniform grids yields a scheme with at most second-order local accuracy, and on nonuniform grids yields at most first-order local accuracy. When expanding the five-point stencil to the nine-point stencil, the derivation using the nine-point stencil on uniform grids yields at most sixth-order local accuracy, but on quasi- and nonuniform grids yields at most fourth- and third-order local accuracy, respectively. © 2013 Society for Industrial and Applied Mathematics.

  2. New Positive and Negative Hierarchies of Integrable Differential-Difference Equations and Conservation Laws

    Institute of Scientific and Technical Information of China (English)

    LI Xin-Yue; ZHAO Qiu-Lan

    2009-01-01

    Two hierarchies of nonlinear integrable positive and negative lattice equations are derived from a discrete spectral problem. The two lattice hierarchies are proved to have discrete zero curvature representations associated with a discrete spectral problem, which also shows that the positive and negative hierarchies correspond to positive and negative power expansions of Lax operators with respect to the spectral parameter, respectively. Moreover, the integrable lattice models in the positive hierarchy are of polynomial type, and the integrable lattice models in the negative hierarchy are of rationed type. Further, we construct infinite conservation laws about the positive hierarchy.

  3. Modelling horizontal steam generator with ATHLET. Verification of different nodalization schemes and implementation of verified constitutive equations

    Energy Technology Data Exchange (ETDEWEB)

    Beliaev, J.; Trunov, N.; Tschekin, I. [OKB Gidropress (Russian Federation); Luther, W. [GRS Garching (Germany); Spolitak, S. [RNC-KI (Russian Federation)

    1995-12-31

    Currently the ATHLET code is widely applied for modelling of several Power Plants of WWER type with horizontal steam generators. A main drawback of all these applications is the insufficient verification of the models for the steam generator. This paper presents the nodalization schemes for the secondary side of the steam generator, the results of stationary calculations, and preliminary comparisons to experimental data. The consideration of circulation in the water inventory of the secondary side is proved to be necessary. (orig.). 3 refs.

  4. Sensitivity of Tropical-Cyclone Models to the Surface Drag Coefficient in Different Boundary-Layer Schemes

    Science.gov (United States)

    2014-04-01

    2006). The far-field temperature and humidity are based on Jordan’s Caribbean sounding for the hurricane season (Jordan, 1958). For the purpose of...in this direction. Key Words: hurricanes ; tropical cyclones; typhoons; surface drag coefficient; frictional drag; boundary layer Received 16 June 2010...using one of five available schemes were compared, not only between themselves, but where possible with recent observational analyses of hurricane

  5. Full-Length Structures of BenM and Two Variants Reveal Different Oligomerization Schemes for LysR-Type Transcriptional Regulators

    Energy Technology Data Exchange (ETDEWEB)

    Ruangprasert, Ajchareeya; Craven, Sarah H.; Neidle, Ellen L.; Momany, Cory (Georgia)

    2010-11-30

    BenM, a LysR-type transcriptional regulator (LTTR) from the bacterium Acinetobacter baylyi, responds synergistically to benzoate and cis,cis-muconate. With these effectors, BenM activates gene expression during benzoate consumption. Without effectors, BenM represses transcription. Here, X-ray crystallography was used to determine the full-length structures of BenM and two variants that activate transcription without benzoate or cis,cis-muconate: BenM(R156H) and BenM(E226K). Previous studies indicate that these regulators function as tetramers. Here, interconnections between subunits in the crystals prevented the formation of a closed oligomer and highlighted the inherent flexibility of this multidomain regulator. Nevertheless, analysis of subunit interfaces suggested the functional significance of key interactions. The structures of BenM and its variants were nearly identical, implying that transcriptional differences rely on factors beyond major conformational changes defined solely by sequence. Comparisons of BenM with other LTTRs, including unpublished structures in the Protein Data Bank, revealed extensive variation in the relative orientations of DNA-binding domains (DBDs) and effector-binding domains (EBDs). To form dimers, different LTTRs used similar interfaces between two EBDs, each containing two subdomains: EBD-I and EBD-II. Surprisingly, the dimers used three substantially different schemes to form higher-order oligomers. In one scheme used by BenM, oligomer assembly involved contacts between the EBD-II regions and the DBD regions of adjacent subunits. In another scheme, there were no contacts between the EBDs; only the DBDs were involved in tetramer formation. In the third scheme, the oligomer interface involved DBD and EBD-I/EBD-II contacts. These diverse schemes demonstrate novel variation in the oligomeric structures of individual LTTRs within this large and important family.

  6. SUPPLEMENT AND IMPROVEMENT OF HOLLY-PREISSMANN SCHEME

    Institute of Scientific and Technical Information of China (English)

    XIE Zuo-tao; ZHANG Xiao-feng; TAN Guang-ming

    2004-01-01

    Using the undetermined coefficient method, Holly-Preissmann scheme is improved effectively. The scheme with the minus velocity is added, and a new conservative scheme is also presented on the basis of original scheme. The simulations of the new scheme accord with the exact result, which enhances its applicability in the engineering.

  7. 16 Pollen Allergens Differ From Nonallergenic Pollen Proteins by Their Lower Extent of Evolutionary Conservation

    OpenAIRE

    Radauer, Christian; Guhslc, Eva; Bublin, Merima; Breiteneder, Heimo

    2012-01-01

    Background Pollen contains hundreds of different proteins. However, only a small fraction of them have been identified to be allergenic. We aimed to test the hypothesis that most pollen proteins are non-allergenic due to their high extent of sequence conservation among non-related species. Methods Data on the composition of pollen proteomes of birch (Betula pendula), pellitory (Parientaria judaica) and timothy grass (Phleum pratense) were obtained from the literature. Sequences were downloade...

  8. A cell-centered lagrangian scheme in two-dimensional cylindrical geometry

    Institute of Scientific and Technical Information of China (English)

    SHEN ZhiJun; YUAN GuangWei; YUE JingYan; LIU XueZhe

    2008-01-01

    A new Lagrangian cell-centered scheme for two-dimensional compressible flows in planar geometry is proposed by Malre et al. The main new feature of the algorithm is that the vertex velocities and the numerical fluxes through the cell interfaces are all evaluated in a coherent manner contrary to standard approaches. In this paper the method introduced by Malre et al. is extended for the equations of Lagrangian gas dynamics in cylindrical symmetry. Two different schemes are proposed, whose difference is that one uses volume weighting and the other area weighting in the discretization of the momentum equation. In the both schemes the conservation of total energy is ensured, and the nodal solver is adopted which has the same formulation as that in Cartesian coordinates. The volume weighting scheme preserves the momentum conservation and the area-weighting scheme preserves spherical symmetry. The numerical examples demonstrate our theoretical considerations and the robustness of the new method.

  9. Nitrogen conservation in simulated food waste aerobic composting process with different Mg and P salt mixtures.

    Science.gov (United States)

    Li, Yu; Su, Bensheng; Liu, Jianlin; Du, Xianyuan; Huang, Guohe

    2011-07-01

    To assess the effects of three types of Mg and P salt mixtures (potassium phosphate [K3PO4]/magnesium sulfate [MgSO4], potassium dihydrogen phosphate [K2HPO4]/MgSO4, KH2PO4/MgSO4) on the conservation of N and the biodegradation of organic materials in an aerobic food waste composting process, batch experiments were undertaken in four reactors (each with an effective volume of 30 L). The synthetic food waste was composted of potatoes, rice, carrots, leaves, meat, soybeans, and seed soil, and the ratio of C and N was 17:1. Runs R1-R3 were conducted with the addition of K3PO4/ MgSO4, K2HPO4/MgSO4, and KH2PO4/MgSO4 mixtures, respectively; run R0 was a blank performed without the addition of Mg and P salts. After composting for 25 days, the degrees of degradation of the organic materials in runs R0-R3 were 53.87, 62.58, 59.14, and 49.13%, respectively. X-ray diffraction indicated that struvite crystals were formed in runs R1-R3 but not in run R0; the gaseous ammonia nitrogen (NH3-N) losses in runs R0-R3 were 21.2, 32.8, 12.6, and 3.5% of the initial total N, respectively. Of the tested Mg/P salt mixtures, the K2HPO4/ MgSO4 system provided the best combination of conservation of N and biodegradation of organic materials in this food waste composting process.

  10. Colour schemes

    DEFF Research Database (Denmark)

    van Leeuwen, Theo

    2013-01-01

    This chapter presents a framework for analysing colour schemes based on a parametric approach that includes not only hue, value and saturation, but also purity, transparency, luminosity, luminescence, lustre, modulation and differentiation....

  11. Verification of a Higher-Order Finite Difference Scheme for the One-Dimensional Two-Fluid Model

    Directory of Open Access Journals (Sweden)

    William D. Fullmer

    2013-06-01

    Full Text Available The one-dimensional two-fluid model is widely acknowledged as the most detailed and accurate macroscopic formulation model of the thermo-fluid dynamics in nuclear reactor safety analysis. Currently the prevailing one-dimensional thermal hydraulics codes are only first-order accurate. The benefit of first-order schemes is numerical viscosity, which serves as a regularization mechanism for many otherwise ill-posed two-fluid models. However, excessive diffusion in regions of large gradients leads to poor resolution of phenomena related to void wave propagation. In this work, a higher-order shock capturing method is applied to the basic equations for incompressible and isothermal flow of the one-dimensional two-fluid model. The higher-order accuracy is gained by a strong stability preserving multi-step scheme for the time discretization and a minmod flux limiter scheme for the convection terms. Additionally the use of a staggered grid allows for several second-order centered terms, when available. The continuity equations are first tested by manipulating the two-fluid model into a pair of linear wave equations and tested for smooth and discontinuous initial data. The two-fluid model is benchmarked with the water faucet problem. With the higher-order method, the ill-posed nature of the governing equations presents severe challenges due to a growing void fraction jump in the solution. Therefore the initial and boundary conditions of the problem are modified in order to eliminate a large counter-current flow pattern that develops. With the modified water faucet problem the numerical models behave well and allow a convergence study. Using the L1 norm of the liquid fraction, it is verified that the first and higher-order numerical schemes converge to the quasi-analytical solution at a rate of O(1/2 and O(2/3, respectively. It is also shown that the growing void jump is a contact discontinuity, i.e. it is a linearly degenerate wave. The sub

  12. Numerical Research on Effects Upon Precipitation Forecast of Doppler-Radar Estimated Precipitation and Retrieved Wind Field Under Different Model Initial Schemes

    Institute of Scientific and Technical Information of China (English)

    WANG Yehong; ZHAO Yuchun; CUI Chunguang

    2007-01-01

    On the basis of the joint estimated 1-h precipitation from Changde, Jingzhou, and Yichang Doppler radars as well as Wuhan digital radar, and the retrieved wind fields from Yichang and Jingzhou Doppler radars, a series of numerical experiments with an advanced regional η-coordinate model (AREM) under different model initial schemes, i.e., Grapes-3DVAR, Barnes objective analysis, and Barnes-3DVAR, are carried out for a torrential rain process occurring along the Yangtze River in the 24-h period from 2000 BT 22 July 2002 to investigate the effects of the Doppler-radar estimated rainfall and retrieved winds on the rainfall forecast. The main results are as follows: (1) The simulations are obviously different under three initial schemes with the same data source (the radiosounding and T213L31 analysis). On the whole,Barnes-3DVAR, which combines the advantages of the Barnes objective analysis and the Grapes-3DVAR method, gives the best simulations: well-simulated rain band and clear mesoscale structures, as well as their location and intensity close to observations. (2) Both Barnes-3DVAR and Grapes-3DVAR schemes are able to assimilate the Doppler-radar estimated rainfall and retrieved winds, but differences in simulation results are very large, with Barnes-3DVAR's simulation much better than Grapes-3DVAR's. (3) Under Grapes3DVAR scheme, the simulation of 24-h rainfall is improved obviously when assimilating the Doppler-radar estimated precipitation into the model in compared with the control experiment; but it becomes a little worse when assimilating the Doppler-radar retrieved winds into the model, and it becomes worse obviously when assimilating the Doppler-radar estimated precipitation as well as retrieved winds into the model. However,the simulation is different under Barnes-3DVAR scheme. The simulation is improved to a certain degree no matter assimilating the estimated precipitation or retrieved winds, or both of them. The result is the best when assimilating both

  13. A Finite Difference Scheme for Double-Diffusive Unsteady Free Convection from a Curved Surface to a Saturated Porous Medium with a Non-Newtonian Fluid

    KAUST Repository

    El-Amin, Mohamed

    2011-05-14

    In this paper, a finite difference scheme is developed to solve the unsteady problem of combined heat and mass transfer from an isothermal curved surface to a porous medium saturated by a non-Newtonian fluid. The curved surface is kept at constant temperature and the power-law model is used to model the non-Newtonian fluid. The explicit finite difference method is used to solve simultaneously the equations of momentum, energy and concentration. The consistency of the explicit scheme is examined and the stability conditions are determined for each equation. Boundary layer and Boussinesq approximations have been incorporated. Numerical calculations are carried out for the various parameters entering into the problem. Velocity, temperature and concentration profiles are shown graphically. It is found that as time approaches infinity, the values of wall shear, heat transfer coefficient and concentration gradient at the wall, which are entered in tables, approach the steady state values.

  14. Neglected grass species of Southern Africa: Nutritive value of conserved Hyperthelia dissoluta harvested at different growth stages

    Directory of Open Access Journals (Sweden)

    Jacob Gusha

    2016-09-01

    Full Text Available Native species like Hyperthelia dissoluta have great potential in livestock production but not much has been done to improve their contribution to that sector.  This study examined 2 conservation methods (drying and ensiling and 3 different growth stages, namely: elongation stage (January, early flowering (February and late flowering stage (March of H. dissoluta in terms of nutritional composition and digestibility.  The method of conservation had a significant effect (P<0.05 on nutritive value, with silage having more P and CP than hay.  Stage of growth had an effect (P<0.05 on all nutritional properties of both hay and silage:  Phosphorus, Ca and CP concentrations and digestibility of hay and silage decreased with maturity, while NDF and ADF concentrations increased.  Silage pH value was significantly higher at elongation (5.2 and late flowering growth stages (5.7 than at early flowering (4.4.  Dry matter digestibility of the conserved material reached levels as high as 82% for silage made at the elongation stage with all values at least 60%.  We conclude that H. dissoluta can be conserved as both silage and hay to produce a good quality feed.  Harvesting at the early flowering stage would seem to provide a good compromise between quantity (not measured in this study and quality of harvested forage.  Further studies seem warranted to determine the acceptability and intake of the material by livestock, the advantages of adding fermentable carbohydrates during ensiling and DM yields in different areas and a range of seasonal conditions. Keywords: Air drying, hay, perennial native grasses, plastic bag silo, quality silage.DOI: 10.17138/TGFT(4179-184

  15. A comparison between beauty in Islamic urban textures and European historic cities: differences in urban conservation strategies

    Directory of Open Access Journals (Sweden)

    Pourya Nazemi

    2014-02-01

    Full Text Available According to the Oriental-Islamic notion of urban space, socio-economic classifications cannot be materialized on the exterior appearance of buildings. On the contrary, in a European historic city, the social status of citizens can easily be expressed on urban facades. Introverted-Islamic textures consist of buildings with courtyards in which interior private facades are more important than the exterior appearance of buildings. In this definition, the European concept of urban façade is not observed. Pursuing an analytic-comparative method, this article attempts to analyze the fundamental differences in the concept of urban beauty between the European historic center and the introverted inner city. Furthermore, the paper defines urban aesthetics with respect to the particularities of the relationship between open and closed spaces. In addition, the principles and characteristics of esoteric beauty in introverted fabrics are discussed. With integral knowledge of the basic differences in urban aesthetics in the two different contexts, the paper tries to analyze the sequent differences which possibly exist in urban conservation strategies. Likewise, the reasons for differences in urban regeneration strategies have been analytically argued. The paper concludes that the definition of urban beauty in introverted-Islamic fabrics completely differs from the perception of beauty in European historic cities. Accordingly, urban conservation strategies in introverted areas should pursue the particularities of Islamic urban beauty. However, the paper emphasizes the necessity for urban transformation in order to give such static areas a new lifestyle.

  16. A Maximum Efficiency Point Tracking Control Scheme Based on Different Cross Coupling of Dual-Receiver Inductive Power Transfer System

    Directory of Open Access Journals (Sweden)

    Ruikun Mai

    2017-02-01

    Full Text Available One of the most promising inductive power transfer applications is the wireless power supply for locomotives which may cancel the need for pantographs. In order to meet the dynamic and high power demands of wireless power supplies for locomotives, a relatively long transmitter track and multiple receivers are usually adopted. However, during the dynamic charging, the mutual inductances between the transmitter and receivers vary and the load of the locomotives also changes randomly, which dramatically affects the system efficiency. A maximum efficiency point tracking control scheme is proposed to improve the system efficiency against the variation of the load and the mutual inductances between the transmitter and receivers while considering the cross coupling between receivers. Firstly, a detailed theoretical analysis on dual receivers is carried out. Then a control scheme with three control loops is proposed to regulate the receiver currents to be the same, to regulate the output voltage and to search for the maximum efficiency point. Finally, a 2 kW prototype is established to validate the performance of the proposed method. The overall system efficiency (DC-DC efficiency reaches 90.6% at rated power and is improved by 5.8% with the proposed method under light load compared with the traditional constant output voltage control method.

  17. The Stability Research for the Finite Difference Scheme of a Nonlinear Reaction-diffusion Equation%一类非线性反应-扩散方程有限差分格式的稳定性研究

    Institute of Scientific and Technical Information of China (English)

    徐琛梅

    2008-01-01

    In the article,the fully discrete finite difference scheme for a type of nonlinear reaction-diffusion equation is established.Then the new function space is introduced and the stability problem for the finite difference scheme is discussed by means of variational approximation method in this function space.The approach used is of a simple characteristic in gaining the stability condition of the scheme.

  18. A dispersion and norm preserving finite difference scheme with transparent boundary conditions for the Dirac equation in (1+1)D

    CERN Document Server

    Hammer, René; Arnold, Anton

    2013-01-01

    A finite difference scheme is presented for the Dirac equation in (1+1)D. It can handle space- and time-dependent mass and potential terms and utilizes exact discrete transparent boundary conditions (DTBCs). Based on a space- and time-staggered leap-frog scheme it avoids fermion doubling and preserves the dispersion relation of the continuum problem for mass zero (Weyl equation) exactly. Considering boundary regions, each with a constant mass and potential term, the associated DTBCs are derived by first applying this finite difference scheme and then using the Z-transform in the discrete time variable. The resulting constant coefficient difference equation in space can be solved exactly on each of the two semi-infinite exterior domains. Admitting only solutions in $l_2$ which vanish at infinity is equivalent to imposing outgoing boundary conditions. An inverse Z-transformation leads to exact DTBCs in form of a convolution in discrete time which suppress spurious reflections at the boundaries and enforce stabi...

  19. Evidence of uneven selective pressure on different subsets of the conserved human genome; implications for the significance of intronic and intergenic DNA

    Directory of Open Access Journals (Sweden)

    MacKenzie Alasdair

    2009-12-01

    Full Text Available Abstract Background Human genetic variation produces the wide range of phenotypic differences that make us individual. However, little is known about the distribution of variation in the most conserved functional regions of the human genome. We examined whether different subsets of the conserved human genome have been subjected to similar levels of selective constraint within the human population. We used set theory and high performance computing to carry out an analysis of the density of Single Nucleotide Polymorphisms (SNPs within the evolutionary conserved human genome, at three different selective stringencies, intersected with exonic, intronic and intergenic coordinates. Results We demonstrate that SNP density across the genome is significantly reduced in conserved human sequences. Unexpectedly, we further demonstrate that, despite being conserved to the same degree, SNP density differs significantly between conserved subsets. Thus, both the conserved exonic and intronic genomes contain a significantly reduced density of SNPs compared to the conserved intergenic component. Furthermore the intronic and exonic subsets contain almost identical densities of SNPs indicating that they have been constrained to the same degree. Conclusion Our findings suggest the presence of a selective linkage between the exonic and intronic subsets and ascribes increased significance to the role of introns in human health. In addition, the identification of increased plasticity within the conserved intergenic subset suggests an important role for this subset in the adaptation and diversification of the human population.

  20. A HIGH-ORDER PAD(E) SCHEME FOR KORTEWEG-DE VRIES EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    XU Zhen-li; LIU Ru-xun

    2005-01-01

    A high-order finite difference Padé scheme also called compact scheme for solving Korteweg-de Vries (KdV) equations, which preserve energy and mass conservations, was developed in this paper.This structure-preserving algorithm has been widely applied in these years for its advantage of maintaining the inherited properties.For spatial discretization, the authors obtained an implicit compact scheme by which spatial derivative terms may be approximated through combining a few knots.By some numerical examples including propagation of single soliton and interaction of two solitons, the scheme is proved to be effective.

  1. DIFFERENT CONCENTRATIONS OF POWDERED EGG YOLK ADDED TO THE ACP-103® EXTENDER IN SWINE SEMEN CONSERVATION

    Directory of Open Access Journals (Sweden)

    Ricardo Toniolli

    2016-04-01

    Full Text Available Many attempts have been made to improve the conservation of boar semen. Egg yolk is known to have cryoprotectant properties. This study aimed to test different concentrations of egg yolk added to the coconut milk powder extender (ACP-103®, and verify which one is better to maintain sperm viability. The ejaculated (36 were diluted in ACP-103® supplemented with different concentrations of egg yolk (0%, 1%, 3%, 5% and 7%. The conservation occurred at 17 °C, and vigor and motility analysis were carried out daily. On days 1 (D0, 3 (D2 and 5 (D4 the semen was evaluated for vitality, morphology and osmotic resistance. For statistical nonparametric analysis Kruskal-Wallis and Dunn’s tests were performed, and for parametric data ANOVA and Tukey test were used. A decrease in vigor and motility was observed in all treatments. Treatments T2, T3 and T4 better maintained spermatic on D0 (2.4±0.8, 2.5±1.1, and 2.8±0.9, respectively, with no signi cant differences among them. The same was observed for motility (77±15%, 74±23%, and 81±16% on D0. Analyses of vitality, morphology and osmotic resistance did not show statistical difference among treatments. In conclusion, the concentration of egg yolk (7% added to the ACP-103® can be e ectively used as extender to maintain sperm viability.

  2. The Mode of Hedgehog Binding to Ihog Homologues is Not Conserved Across Different Phyla

    Energy Technology Data Exchange (ETDEWEB)

    McLellan, J.; Zheng, X; Hauk, G; Ghirlando, R; Beachy, P; Leahy, D

    2008-01-01

    Hedgehog (Hh) proteins specify tissue pattern in metazoan embryos by forming gradients that emanate from discrete sites of expression and elicit concentration-dependent cellular differentiation or proliferation responses1, 2. Cellular responses to Hh and the movement of Hh through tissues are both precisely regulated, and abnormal Hh signalling has been implicated in human birth defects and cancer3, 4, 5, 6, 7. Hh signalling is mediated by its amino-terminal domain (HhN), which is dually lipidated and secreted as part of a multivalent lipoprotein particle8, 9, 10. Reception of the HhN signal is modulated by several cell-surface proteins on responding cells, including Patched (Ptc), Smoothened (Smo), Ihog (known as CDO or CDON in mammals) and the vertebrate-specific proteins Hip (also known as Hhip) and Gas1 (ref. 11). Drosophila Ihog and its vertebrate homologues CDO and BOC contain multiple immunoglobulin and fibronectin type III (FNIII) repeats, and the first FNIII repeat of Ihog binds Drosophila HhN in a heparin-dependent manner12, 13. Surprisingly, pull-down experiments suggest that a mammalian Sonic hedgehog N-terminal domain (ShhN) binds a non-orthologous FNIII repeat of CDO12, 14. Here we report biochemical, biophysical and X-ray structural studies of a complex between ShhN and the third FNIII repeat of CDO. We show that the ShhN-CDO interaction is completely unlike the HhN-Ihog interaction and requires calcium, which binds at a previously undetected site on ShhN. This site is conserved in nearly all Hh proteins and is a hotspot for mediating interactions between ShhN and CDO, Ptc, Hip and Gas1. Mutations in vertebrate Hh proteins causing holoprosencephaly and brachydactyly type A1 map to this calcium-binding site and disrupt interactions with these partners.

  3. Achieving Energy Conservation in Poisson-Boltzmann Molecular Dynamics: Accuracy and Precision with Finite-Difference Algorithms

    Science.gov (United States)

    Wang, Jun; Cai, Qin; Li, Zhi-Lin; Zhao, Hong-Kai; Luo, Ray

    2009-01-01

    Violation of energy conservation in Poisson-Boltzmann molecular dynamics, due to the limited accuracy and precision of numerical methods, is a major bottleneck preventing its wide adoption in biomolecular simulations. We explored the ideas of enforcing interface conditions by the immerse interface method and of removing charge singularity to improve the finite-difference methods. Our analysis of these ideas on an analytical test system shows significant improvement in both energies and forces. Our analysis further indicates the need for more accurate force calculation, especially the boundary force calculation. PMID:20098487

  4. CpG methylation differences between neurons and glia are highly conserved from mouse to human

    Science.gov (United States)

    Understanding epigenetic differences that distinguish neurons and glia is of fundamental importance to the nascent field of neuroepigenetics. A recent study used genome-wide bisulfite sequencing to survey differences in DNA methylation between these two cell types, in both humans and mice. That stud...

  5. Conservative whole-organ scaling contrasts with highly labile suborgan scaling differences among compound eyes of closely related Formica ants.

    Science.gov (United States)

    Perl, Craig D; Rossoni, Sergio; Niven, Jeremy E

    2017-03-01

    Static allometries determine how organ size scales in relation to body mass. The extent to which these allometric relationships are free to evolve, and how they differ among closely related species, has been debated extensively and remains unclear; changes in intercept appear common, but changes in slope are far rarer. Here, we compare the scaling relationships that govern the structure of compound eyes of four closely related ant species from the genus Formica. Comparison among these species revealed changes in intercept but not slope in the allometric scaling relationships governing eye area, facet number, and mean facet diameter. Moreover, the scaling between facet diameter and number was conserved across all four species. In contrast, facet diameters from distinct regions of the compound eye differed in both intercept and slope within a single species and when comparing homologous regions among species. Thus, even when species are conservative in the scaling of whole organs, they can differ substantially in regional scaling within organs. This, at least partly, explains how species can produce organs that adhere to genus wide scaling relationships while still being able to invest differentially in particular regions of organs to produce specific features that match their ecology.

  6. Bonus schemes and trading activity

    NARCIS (Netherlands)

    Pikulina, E.S.; Renneboog, L.D.R.; ter Horst, J.R.; Tobler, P.N.

    2014-01-01

    Little is known about how different bonus schemes affect traders' propensity to trade and which bonus schemes improve traders' performance. We study the effects of linear versus threshold bonus schemes on traders' behavior. Traders buy and sell shares in an experimental stock market on the basis of

  7. Bonus Schemes and Trading Activity

    NARCIS (Netherlands)

    Pikulina, E.S.; Renneboog, L.D.R.; Ter Horst, J.R.; Tobler, P.N.

    2013-01-01

    Abstract: Little is known about how different bonus schemes affect traders’ propensity to trade and which bonus schemes improve traders’ performance. We study the effects of linear versus threshold (convex) bonus schemes on traders’ behavior. Traders purchase and sell shares in an experimental stock

  8. Bonus schemes and trading activity

    NARCIS (Netherlands)

    Pikulina, E.S.; Renneboog, L.D.R.; ter Horst, J.R.; Tobler, P.N.

    2014-01-01

    Little is known about how different bonus schemes affect traders' propensity to trade and which bonus schemes improve traders' performance. We study the effects of linear versus threshold bonus schemes on traders' behavior. Traders buy and sell shares in an experimental stock market on the basis of

  9. [Simulated responses of winter wheat yield and soil moisture to different conservation tiliage practices in Weibei Highlands, Northwest China].

    Science.gov (United States)

    Zhang, Yu-Jiao; Li, Jun; Guo, Zheng; Yue, Zhi-fang

    2015-03-01

    Based on the verified precision results by simulation, the WinEPIC (EPIC, environmental/policy integrated climate model) was employed to quantitatively simulate effects of three conservation tillage practices adopted during the period of summer fallow, i.e. sub-soiling, no-tillage and conventional tillage, on wheat yield and soil moisture in Weibei Highlands during 1980-2009. The results showed that during the study period, the yield and annual water consumption of winter wheat under the different tillage practices tended to decrease with fluctuation in the growing period. The yield and water use efficiency of winter wheat under sub-soiling were the highest, averaging 3.33 t . hm-2 and 8.50 kg . hm-2 . mm-1 over the thirty years, respectively, and that of no tillage was the lowest. The annual water consumption of winter wheat was .slightly higher under sub-soiling than under no tillage and conventional tillage. In 0-3 m soil layer, the available soil water content tended to decline in a strongly and seasonally fluctuating manner. No tillage performed best in soil moisture conservation, with the average available soil water content being 89.5 mm, and that of conventional tillage was the lowest. The soil water moisture fluctuated with the seasonal rainfalls in 0-1 m soil layer and kept stable in 1-3 m with no great difference among the tillage practices. Under long-term continuous cropping, sub-soiling showed the best effects on the yield of winter wheat and the most comprehensive effect on soil moisture, and was the best practice of conservation tillage for wheat lands on Weibei Highlands.

  10. FACTORS ASSOCIATED TO ADHERENCE TO DIFFERENT TREATMENT SCHEMES WITH MEGLUMINE ANTIMONIATE IN A CLINICAL TRIAL FOR CUTANEOUS LEISHMANIASIS

    Directory of Open Access Journals (Sweden)

    Madelon Novato Ribeiro

    2014-07-01

    Full Text Available The favorable outcome of the treatment of a disease is influenced by the adherence to therapy. Our objective was to assess factors associated with adherence to treatment of patients included in a clinical trial of equivalence between the standard and alternative treatment schemes with meglumine antimoniate (MA in the treatment of cutaneous leishmaniasis (CL, in the state of Rio de Janeiro. Between 2008 and 2011, 57 patients with CL were interviewed using a questionnaire to collect socioeconomic data. The following methods were used for adherence monitoring: counting of vial surplus, monitoring card, Morisky test and modified Morisky test (without the question regarding the schedule; we observed 82.1% (vial return, 86.0% (monitoring card, 66.7% (Morisky test and 86.0% (modified Morisky test adherence. There was a strong correlation between the method of vial counting and the monitoring card and modified Morisky test. A significant association was observed between greater adherence to treatment and low dose of MA, as well as with a lower number of people sleeping in the same room. We recommend the use of the modified Morisky test to assess adherence to treatment of CL with MA, because it is a simple method and with a good performance, when compared to other methods.

  11. APPLICATION OF WEIGHTED NON- OSCILLATORY AND NON-FREE- PARAMETER DISSIPATION DIFFERENCE SCHEME IN CALCULATING THE FLOW OF VIBRATING FLAT CASCADE

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A dual-time method is introduced to calculate the unsteady flow in a certain vibrating flat cascade. An implicit lower-upper symmetric-gauss-seidel scheme(LU-SGS) is applied for time stepping in pseudo time domains, and the convection items are discretized with the spatial three-order weighted non-oscillatory and non-free-parameter dissipation difference (WNND) scheme. The turbulence model adopts q-( low-Reynolds-number model. The frequency spectrums of lift coefficients and the unsteady pressure-difference coefficients at different spanwise heights as well as the entropy contours at blade tips on different vibrating instants, are obtained. By the analysis of frequency spectrums of lift coefficients at three spanwise heights, it is considered that there exist obvious non-linear perturbations in the flow induced by the vibrating, and the perturbation frequencies are higher than the basic frequency. The entropy contours at blade tips at different times display an intensively unsteady attribute of the flow under large amplitudes.

  12. Microbiological monitoring in two areas with different levels of conservation in the mangroves of an Ecological Station, Vitoria, ES

    Directory of Open Access Journals (Sweden)

    Juliano de Oliveira Barbirato

    2016-12-01

    Full Text Available Mangroves are classified as permanent preservation areas and regarded as natural nurseries. However, they have suffered several anthropogenic stresses, resulting in their decline. In the light of that, comes the importance of researching their environmental characteristics and revealing possible factors that have led to the degradation of this important ecosystem. The aim of this study was to evaluate the environmental quality of different areas in the mangroves of Ilha do Lameirão Ecological Station through microbiological analyzes of sediment and interstitial water along ten (10 sites, distributed in two areas with different conservation levels (Canal dos Escravos (CE and Maria Ortiz (MO between 2010 and 2012. The microbiological analyzes revealed that MO region, in all seasons of the year, achieved total coliform and thermo-tolerant coliform values above those permitted by the CONAMA Resolution 357/05, fitting the Class 2 conservation standard. The presence of high levels of total and thermo-tolerant coliforms in MO is a strong indicator of impacts originated from the human population and, consequently, the decline of the mangrove itself and the health of human communities surrounding that area.

  13. A Pilot Assessment of Ethnic Differences in Cosmetic Outcomes following Breast Conservation Therapy

    Directory of Open Access Journals (Sweden)

    Elliot M. Hirsch, MD

    2014-01-01

    Conclusions: Although generalizing the results of this study is limited by the small sample size, it seems that there is a difference in the perception of cosmetic outcomes between white and African American patients. The novel techniques of cosmetic evaluation used in this study show promise toward identifying variables that can affect cosmetic outcome following BCT.

  14. Simulation of Indian summer monsoon onset with different parameterization convection schemes of RegCM-4.3

    Science.gov (United States)

    Bhatla, R.; Ghosh, S.; Mandal, B.; Mall, R. K.; Sharma, Kuldeep

    2016-07-01

    Simulation of Indian Summer Monsoon (ISM) onset over South Asia Coordinated Regional Climate Downscaling Experiment (CORDEX) domain in pentad composite pattern is considered for this study. The latest version of the International Center for Theoretical Physics' (ICTP's) Regional Climate Model version 4.3 (RegCM-4.3) is used for the simulation of a pentad composite onset for three time period: Pre-onset, Onset and Post-onset periods of ISM. Each pentad composite is average of five consecutive days. 10 years (2001-2010) worth of pentad composites of rainfall, mean sea level pressure (MSLP), outgoing longwave radiation (OLR), wind at 850 hPa and 925 hPa levels till 7 days prior to the date of onset of monsoon and 7 days after the onset are analyzed to find out the predictive skill. Six Parameterization convection schemes (PCSs) viz. Kuo, Mix98, Mix99, Tiedtke, Emanuel and Grell are used in sensitivity experiment and estimation of their performance has been done. From the experiment, some modulation is found in the OLR field (≤ 200 Wm- 2) within the region 5°N-10°N and 70°N-75°E. Yearly analysis has shown the strength of wind at 925 hPa over the region 5°N-10°N and 70°E-80°E on pentad composite onset of ISM. Yearly analysis is conducted for finding the best fitted PCS which has provided the precursor for simulating the onset.

  15. Improved nonparametric estimation of the optimal diagnostic cut-off point associated with the Youden index under different sampling schemes.

    Science.gov (United States)

    Yin, Jingjing; Samawi, Hani; Linder, Daniel

    2016-07-01

    A diagnostic cut-off point of a biomarker measurement is needed for classifying a random subject to be either diseased or healthy. However, the cut-off point is usually unknown and needs to be estimated by some optimization criteria. One important criterion is the Youden index, which has been widely adopted in practice. The Youden index, which is defined as the maximum of (sensitivity + specificity -1), directly measures the largest total diagnostic accuracy a biomarker can achieve. Therefore, it is desirable to estimate the optimal cut-off point associated with the Youden index. Sometimes, taking the actual measurements of a biomarker is very difficult and expensive, while ranking them without the actual measurement can be relatively easy. In such cases, ranked set sampling can give more precise estimation than simple random sampling, as ranked set samples are more likely to span the full range of the population. In this study, kernel density estimation is utilized to numerically solve for an estimate of the optimal cut-off point. The asymptotic distributions of the kernel estimators based on two sampling schemes are derived analytically and we prove that the estimators based on ranked set sampling are relatively more efficient than that of simple random sampling and both estimators are asymptotically unbiased. Furthermore, the asymptotic confidence intervals are derived. Intensive simulations are carried out to compare the proposed method using ranked set sampling with simple random sampling, with the proposed method outperforming simple random sampling in all cases. A real data set is analyzed for illustrating the proposed method.

  16. Local origins impart conserved bone type-related differences in human osteoblast behaviour.

    Science.gov (United States)

    Shah, M; Gburcik, V; Reilly, P; Sankey, R A; Emery, R J; Clarkin, C E; Pitsillides, A A

    2015-03-04

    Osteogenic behaviour of osteoblasts from trabecular, cortical and subchondral bone were examined to determine any bone type-selective differences in samples from both osteoarthritic (OA) and osteoporotic (OP) patients. Cell growth, differentiation; alkaline phosphatase (TNAP) mRNA and activity, Runt-related transcription factor-2 (RUNX2), SP7-transcription factor (SP7), bone sialoprotein-II (BSP-II), osteocalcin/bone gamma-carboxyglutamate (BGLAP), osteoprotegerin (OPG, TNFRSF11B), receptor activator of nuclear factor-κβ ligand (RANKL, TNFSF11) mRNA levels and proangiogenic vascular endothelial growth factor-A (VEGF-A) mRNA and protein release were assessed in osteoblasts from paired humeral head samples from age-matched, human OA/OP (n = 5/4) patients. Initial outgrowth and increase in cell number were significantly faster (p origins in OA and trabecular origins in OP. We found virtually identical bone type-related differences, however, in TNFRSF11B:TNFSF11 in OA and OP, consistent with greater potential for paracrine effects on osteoclasts in trabecular osteoblasts. Subchondral osteoblasts (OA) exhibited highest VEGF-A mRNA levels and release. Our data indicate that human osteoblasts in trabecular, subchondral and cortical bone have inherent, programmed diversity, with specific bone type-related differences in growth, differentiation and pro-angiogenic potential in vitro.

  17. Conservation of Campomanesia adamantium (CAMB. O. berg seeds in different packaging and at varied temperatures

    Directory of Open Access Journals (Sweden)

    Silvana de Paula Quintão Scalon

    2013-03-01

    Full Text Available This article aims at evaluating the effects of different packaging and varied storage temperatures on the germination potential of seeds of Campomanesia adamantium Camb. O. Berg. The seeds were packaged in glass, aluminum foil and plastic containers, or maintained inside intact fruits at 5, 10 and 15 ºC during 0, 7, 14 and 21 days. After these periods the seeds were sown in Germitest® germination paper and maintained in incubation chambers at 25 ºC under constant white light for 42 days. Seed moisture contents were evaluated both before and after storage, as well as germination percentages, germination speed index, root and aerial portion of seedlings lengths, and total dry weights. All possible combinations of packing materials, temperatures and storage times were tested, with four repetitions of 25 seeds for each treatment. C. adamantium seeds showed initial water contents of 31.5%. Glass and aluminum packaging were efficient at maintaining the water content of the seeds, and provided greater germination speed index than the other packaging materials. Germination percentages, seedlings lengths and dry weights did not vary among the different temperatures tested. C. adamantium seeds can be stored for up to 21 days at temperatures between 5 and 15 ºC without altering their physiological quality. In terms of cost-benefit efficiencies, these seeds can be stored without significant damage for 21 days while still inside the fruits at temperatures of 5, 10 or 15 ºC.

  18. A SECOND ORDER L∞ CONVERGENT DIFFERENCE SCHEME FOR LINEAR HYPERBOLIC EQUATION WITH DERIVATIVE BOUNDARY CONDITIONS%带导数边界条件的线性双曲方程的一个二阶L∞收敛格式

    Institute of Scientific and Technical Information of China (English)

    万正苏

    2002-01-01

    In this paper, a difference scheme is derived for the one dimensionallinear hyperbolic differential equation with derivative boundary conditions by themethod of reduction of order. It is proved that the scheme is unconditionally sta-ble, uniquely solvable and second order convergent in L∞ norm. Two numericalexamples are presented.

  19. An evolutionarily conserved negative feedback mechanism in the Hippo pathway reflects functional difference between LATS1 and LATS2.

    Science.gov (United States)

    Park, Gun-Soo; Oh, Hyangyee; Kim, Minchul; Kim, Tackhoon; Johnson, Randy L; Irvine, Kenneth D; Lim, Dae-Sik

    2016-04-26

    The Hippo pathway represses YAP oncoprotein activity through phosphorylation by LATS kinases. Although variety of upstream components has been found to participate in the Hippo pathway, the existence and function of negative feedback has remained uncertain. We found that activated YAP, together with TEAD transcription factors, directly induces transcription of LATS2, but not LATS1, to form a negative feedback loop. We also observed increased mRNA levels of Hippo upstream components upon YAP activation. To reveal the physiological role of this negative feedback regulation, we deleted Lats2 or Lats1 in the liver-specific Sav1-knockout mouse model which develops a YAP-induced tumor. Additional deletion of Lats2 severely enhanced YAP-induced tumorigenic phenotypes in a liver specific Sav1 knock-out mouse model while additional deletion of Lats1 mildly affected the phenotype. Only Sav1 and Lats2 double knock-down cells formed larger colonies in soft agar assay, thereby recapitulating accelerated tumorigenesis seen in vivo. Importantly, this negative feedback is evolutionarily conserved, as Drosophila Yorkie (YAP ortholog) induces transcription of Warts (LATS2 ortholog) with Scalloped (TEAD ortholog). Collectively, we demonstrated the existence and function of an evolutionarily conserved negative feedback mechanism in the Hippo pathway, as well as the functional difference between LATS1 and LATS2 in regulation of YAP.

  20. Post-harvest conservation of camu–camu fruits (Myrciaria dubia (Kunth Mc Vaugh using different temperatures and packages

    Directory of Open Access Journals (Sweden)

    Maria Luiza GRIGIO

    2015-12-01

    Full Text Available Abstract The camu-camu tree (Myrciaria dubia (Kunth Mc Vaugh is fruit-bearing tree belonging to the family Myrtaceae. This work was conducted with the purpose of evaluating the type of storage temperature and package which allow better conservation of the quality attributes of camu-camu. The experimental design utilized was the completely randomized with three replications in a factorial arrangement (3x3x8, constituted of three different storage temperatures (laboratory ambiente or 25 ± 2 °C, 15 °C and 20 °C, three types of packages (no package, PET and PVC and fourteen days’ storage, the fruits being analyzed every two days. The fruits were evaluated as to fresh mass loss, pH, soluble solids contents, titrable acidity, ascorbic acid, carotenoids, anthocyanins, chlorophylls A and B and maturation index (SS/AT. According to the results obtained, the quality attributes and ascorbic acid content were conserved for longer time in the fruits stored on PVC-film covered expanded polystyrene trays at 15 °C. It follows that the best temperature for the storage of camu-camu is 15 °C and the package that best keeps its quality attributes is the PVC-film covered expanded polystyrene tray.

  1. SOIL CONSERVATION EFFICIENCY OF DIFFERENT MODELS CONVERTING FROM STEEP FARMING SLOPE PLOTS IN YA'AN, SICHUAN, CHINA

    Institute of Scientific and Technical Information of China (English)

    Yulin DENG; Yan PENG; Yukuan WANG; Zongting YANG

    2003-01-01

    Converting farming slope land into artificial forestland or grassland is a major measure of soil/water conservation. Five conversion practices, namely, 1) a control plot still tilled with a crop (maize), 2) a folder grass-growing plot seeded with Lolium perenne, 3) a young alder tree-growing plot, 4) a pear orchard plot and 5)a bamboo plot intercropped with folder grass, were monitored to compare the soil conservation efficiency of those changes in Ya'an, Sichuan for 3 years between September 1998 and August 2001. Results showed that the 5 designed converting models functioned differently in erosion control. The most effective model was bamboo groves intercropped with folder grass (Lolium perenne). The folder grass (Lolium perenne) growing model was more effective than the pure pear orchard model. The least effective model was the young alder tree-growing slope, which was even less effective than the control (a slope without converted cultivation). Meanwhile, changes in the soil's physical properties reflected the same results.Therefore, the optimum model for controlling watershed and slope erosion was by converting farming land into forestland or grassland.

  2. Life at a different pace: Annual itineraries are conserved in seasonal songbirds

    Indian Academy of Sciences (India)

    S Malik; S Singh; S Rani; V Kumar

    2014-06-01

    The duration of life history state (LHS) reflects the adaptive strategy a species has evolved to cope with a changing environment. Inhabitants at different latitudes may thus have significant differences in the rates of metabolic and physiological processes underlying LHSs. Birds, in order to maximize their fitness in the environment in which they live, seasonally switch from one LHS to another during the year. The present study investigated whether an annual itinerary of a species would determine its rate of reaction to inductive long days. We compared the photoinduced cycles of changes in body mass and testes, as indices of migratory and reproductive LHSs, between two long day breeding species, the migratory redheaded bunting and non-migratory Indian weaverbird. Changes in body mass and testis size were measured in photosensitive buntings and weaverbirds ( = 7 each) on short days (LD 8:16) subjected first to 0.5 h weekly light increments until the light period was 13 h per day, and then maintained on LD 13:11 for another 32 weeks. A similar observation was recorded on a group of buntings ( = 14) and weaverbirds ( = 9) maintained on increasing natural day lengths (NDL; Lucknow, 26°55′ N, 80°59′ E) for 47 weeks. As predicted, the rates of induction of seasonal cycles under an identical inductive photoperiod were significantly faster in temperate buntings with five annual LHSs than in the subtropical weaverbirds with three annual LHSs. This suggests that annual itineraries of songbirds with which they may have evolved with at their breeding latitudes, determine their response to the external photoperiodic environment.

  3. Conserved differences in protein sequence determine the human pathogenicity of Ebolaviruses

    Science.gov (United States)

    Pappalardo, Morena; Juliá, Miguel; Howard, Mark J.; Rossman, Jeremy S.; Michaelis, Martin; Wass, Mark N.

    2016-01-01

    Reston viruses are the only Ebolaviruses that are not pathogenic in humans. We analyzed 196 Ebolavirus genomes and identified specificity determining positions (SDPs) in all nine Ebolavirus proteins that distinguish Reston viruses from the four human pathogenic Ebolaviruses. A subset of these SDPs will explain the differences in human pathogenicity between Reston and the other four ebolavirus species. Structural analysis was performed to identify those SDPs that are likely to have a functional effect. This analysis revealed novel functional insights in particular for Ebolavirus proteins VP40 and VP24. The VP40 SDP P85T interferes with VP40 function by altering octamer formation. The VP40 SDP Q245P affects the structure and hydrophobic core of the protein and consequently protein function. Three VP24 SDPs (T131S, M136L, Q139R) are likely to impair VP24 binding to human karyopherin alpha5 (KPNA5) and therefore inhibition of interferon signaling. Since VP24 is critical for Ebolavirus adaptation to novel hosts, and only a few SDPs distinguish Reston virus VP24 from VP24 of other Ebolaviruses, human pathogenic Reston viruses may emerge. This is of concern since Reston viruses circulate in domestic pigs and can infect humans, possibly via airborne transmission. PMID:27009368

  4. Comparison of different grading schemes in InGaAs metamorphic buffers on GaAs substrate: Tilt dependence on cross-hatch irregularities

    Science.gov (United States)

    Kumar, Rahul; Bag, Ankush; Mukhopadhyay, Partha; Das, Subhashis; Biswas, Dhrubes

    2015-12-01

    InGaAs graded metamorphic buffers (MBs) with different grading strategies have been grown by molecular beam epitaxy (MBE) on GaAs (0 0 1) substrate. A detailed comparative analysis of surface using atomic force microscopy (AFM), and bulk properties using high resolution X-ray diffraction (HRXRD) and room temperature photoluminescence (RTPL) of grown MBs have been presented to comprehend the effectiveness of different grading scheme on InGaAs MBs. Conventional, statistical and fractal analysis on measured AFM data has been performed for in-depth investigation of these surfaces. The grading scheme has been found to have little impact on residual strain while it affects the epitaxial tilt significantly. Moreover, the tilt has been found to depend on growth front irregularities. Tilt magnitude in a graded MB has been found to vary with composition while tilt azimuth has been found to be almost same in the graded layers. PL Intensity and a shift in the PL peaks have been used to study the quality of the MB and residual strain comparatively.

  5. Double-Difference Waveform Inversion with a Modified Total-Variation Regularization Scheme: Application to Time-Lapse Walkaway VSP Data

    Science.gov (United States)

    Lin, Y.; Huang, L.

    2014-12-01

    Quantifying reservoir changes is crucial for safe and long-term geologic carbon storage. We develop a new double-difference waveform inversion method with a modified total-variation regularization scheme to jointly invert time-lapse seismic data for geophysical properties changes in reservoirs/target monitoring regions. Our new method avoids the non-differentiability of the total-variation regularization scheme, and improves the robustness of waveform inversion. We use time-lapse seismic data for joint inversion to reduce inversion artifacts outside target monitoring regions. Two walkaway vertical seismic profiling (VSP) datasets were acquired at the SACROC enhanced-oil-recovery (EOR) field in Texas in 2008 and 2009 for monitoring CO2 injection and migration. We apply our new double-difference waveform inversion method to the SACROC time-lapse VSP datasets. Our joint inversion result reveals a region with seismic-wave velocities lower than the other regions in the reservoir. This velocity decrease is caused by CO2 injection and migration.

  6. Comparative study of Green's function matrix elements and charge transfers obtained from different partitioning schemes of molecular charge in hydrogen-bonded complexes

    Directory of Open Access Journals (Sweden)

    Parnaíba-da Silva Antenor J.

    2006-01-01

    Full Text Available RHF and MP2 ab initio molecular orbital calculations using the 4-31G**, 6-311G** and cc-pVTZ basis sets have revealed that the Green's function matrix element (G D,A values show a good correlation with the amount of intermolecular transferred charges obtained from different charge partitioning schemes for the CNH?CNH, NCH?CNH, CNH?NCH and NCH?NCH hydrogen bonded complexes. This is evident specially when the hydrogen bond distance is progressively increased from the equilibrium position until 4.5 Å. However, G D,A values show a better linear correlation with deltaQ values using corrected Mülliken charges, which are obtained from the charge-charge flux-overlap (CCFO model for infrared intensities. In this case, both G D,A and deltaQcorr form two practically superposed exponential curves. On the other hand, G D,A values show a smaller agreement with deltaQ values obtained from atomic charges derived from natural bonding orbitals. This is clearly verified when considering the first order exponential decay rate of G D,A versus deltaQ obtained from different charge partitioning schemes.

  7. Comparison of different undulator schemes with superimposed alternating gradients for the VUV-FEL at the TESLA Test Facility

    Energy Technology Data Exchange (ETDEWEB)

    Pflueger, J.; Nikitina, Y.M. [DESY/HASYLAB, Hamburg (Germany)

    1995-12-31

    For the VUV-FEL at the TESLA Test Facility an undulator with a total length of 30 m is needed. In this study three different approaches to realize an undulator with a sinusoidal plus a superimposed quadrupolar field were studied with the 3D code MAFIA.

  8. An Energy Conserving Parallel Hybrid Plasma Solver

    CERN Document Server

    Holmstrom, M

    2010-01-01

    We investigate the performance of a hybrid plasma solver on the test problem of an ion beam. The parallel solver is based on cell centered finite differences in space, and a predictor-corrector leapfrog scheme in time. The implementation is done in the FLASH software framework. It is shown that the solver conserves energy well over time, and that the parallelization is efficient (it exhibits weak scaling).

  9. 高阶抛物型方程的一族高精度恒稳差分格式%A FAMILY OF ABSOLUTELY STABLE DIFFERENCE SCHEMES OF HIGH ACCURACY FOR SOLVING HIGH ORDER PARABALIC EQUATION

    Institute of Scientific and Technical Information of China (English)

    曾文平

    2003-01-01

    A family of three-layer implicit difference Schemes of high accuracy with two parameters for solving high order parabolic equationδu/δt=(-1)m+1δ2mu/δx2m(where m is positive integers) are constructed. In the special case α=1/2, β=0, We obtain a two-layer difference scheme. These schemes are proved to be absolutely stable for arbiratily chosen non-negative parameters, And the order of the truncation error is O((△t)2+(△x)6). They are shown by numerical examples to be effective, and practice consistant with theoretical analysis.

  10. The Effect of Different in-situ Water Conservation Tillage Methods on Growth and Development of Taro (Colocasia esculenta L.

    Directory of Open Access Journals (Sweden)

    A.M. Manyatsi

    2011-01-01

    Full Text Available Taro (Colocasia esculenta L. is an important food crop in the diet of Swazi people. However, there is dearth of information in the country on appropriate agronomic practices which can adequately conserve soil moisture to meet taro crop water requirements. The effects of in-situ water conservation practices on growth, development and yield of taro were investigated. Five in-situ water conservation methods/treatments [tied ridges, ridges, half moon, flat (not irrigated and flat (irrigated] were evaluated. The flat (irrigated treatment served as a control. The experiment was conducted in a sandy clay loam soil at Luyengo. The treatments were laid in a randomized complete block design (RCBD replicated three times. Each plot measured 5.0 m x 5.0 m with inter-row spacing of 0.9 m and intra- row plant spacing of 0.3 m for flat seedbeds. The ridges were 0.3 m high and 1 m apart, and ties were 0.2 m high spaced at 0.5 m intervals. The half moons had a diameter of 0.5 m. Planting was done in October 2009 using corms. The plants were rainfed, except for the irrigated treatment where irrigation w as done to field capacity when soil moisture matric potential reached 10 bars. Parameters measured included soil moisture, plant emergence, plant height, number of leaves, leaf length and leaf width. Leaf area and Leaf Area Index (LAI were calculated. The fresh yield of corms was measured at 24 weeks after planting. The results showed plant emergence rate after three weeks being highest under the half moon, at 94% followed in decreasing order by irrigated flat at 90% , tied ridges at 85%, ridges at 82% and lastly flat (not irrigated at 80%. The various treatments did not show significant (p>0.05 differences in plant height throughout the growing period. However plants grown in irrigated flat plots consistently exhibited significantly (p<0.01 the highest number of leaves compared to other treatments. A similar trend w as also observed with LAI. Taro corm yield were

  11. Direct Numerical Simulation of Transitional and Turbulent Flow Over a Heated Flat Plate Using Finite-Difference Schemes

    Science.gov (United States)

    Madavan, Nateri K.

    1995-01-01

    The work in this report was conducted at NASA Ames Research Center during the period from August 1993 to January 1995 deals with the direct numerical simulation of transitional and turbulent flow at low Mach numbers using high-order-accurate finite-difference techniques. A computation of transition to turbulence of the spatially-evolving boundary layer on a heated flat plate in the presence of relatively high freestream turbulence was performed. The geometry and flow conditions were chosen to match earlier experiments. The development of the momentum and thermal boundary layers was documented. Velocity and temperature profiles, as well as distributions of skin friction, surface heat transfer rate, Reynolds shear stress, and turbulent heat flux were shown to compare well with experiment. The numerical method used here can be applied to complex geometries in a straightforward manner.

  12. [Dynamics of functional parameters in different schemes for bronchial asthma therapy: results of the STRELA-ACT multicentre study].

    Science.gov (United States)

    Ogorodova, L M; Kulikov, E S; Deev, I A; Cherniak, B A; Fassakhov, R S

    2011-01-01

    Different strategies for disease control in real clinical practice are compared in terms of dynamics of functional parameters in patients with persistent bronchial asthma. This prospective multicentre surveillance study was carried out in 19 Russian clinics using the common protocol. The patients were divided in 3 groups in accordance with the changes of basal antiinflammatory therapy during the study period. Group A--stepwise increase in the extent of combined salmoterol/fluticason therapy, group B--long-term stable-dose salmoterol/fluticason therapy, group C--salmoterol/fluticason therapy with gradual decrease of the dose and/or transition to an alternative variant. Statistical analysis using Statistica 6.0 program included data from 543 patients. The results suggest that the two first modalities increased the level of control (ACT test) and improved characteristics of external respiration throughout the study period. Strategy 3 was associated with a decrease in the external respiration function and the level of control.

  13. An interference-based optical authentication scheme using two phase-only masks with different diffraction distances

    Science.gov (United States)

    Lu, Dajiang; He, Wenqi; Liao, Meihua; Peng, Xiang

    2017-02-01

    A new method to eliminate the security risk of the well-known interference-based optical cryptosystem is proposed. In this method, which is suitable for security authentication application, two phase-only masks are separately placed at different distances from the output plane, where a certification image (public image) can be obtained. To further increase the security and flexibility of this authentication system, we employ one more validation image (secret image), which can be observed at another output plane, for confirming the identity of the user. Only if the two correct masks are properly settled at their positions one could obtain two significant images. Besides, even if the legal users exchange their masks (keys), the authentication process will fail and the authentication results will not reveal any information. Numerical simulations are performed to demonstrate the validity and security of the proposed method.

  14. An efficient class of WENO schemes with adaptive order

    Science.gov (United States)

    Balsara, Dinshaw S.; Garain, Sudip; Shu, Chi-Wang

    2016-12-01

    Finite difference WENO schemes have established themselves as very worthy performers for entire classes of applications that involve hyperbolic conservation laws. In this paper we report on two major advances that make finite difference WENO schemes more efficient. The first advance consists of realizing that WENO schemes require us to carry out stencil operations very efficiently. In this paper we show that the reconstructed polynomials for any one-dimensional stencil can be expressed most efficiently and economically in Legendre polynomials. By using Legendre basis, we show that the reconstruction polynomials and their corresponding smoothness indicators can be written very compactly. The smoothness indicators are written as a sum of perfect squares. Since this is a computationally expensive step, the efficiency of finite difference WENO schemes is enhanced by the innovation which is reported here. The second advance consists of realizing that one can make a non-linear hybridization between a large, centered, very high accuracy stencil and a lower order WENO scheme that is nevertheless very stable and capable of capturing physically meaningful extrema. This yields a class of adaptive order WENO schemes, which we call WENO-AO (for adaptive order). Thus we arrive at a WENO-AO(5,3) scheme that is at best fifth order accurate by virtue of its centered stencil with five zones and at worst third order accurate by virtue of being non-linearly hybridized with an r = 3 CWENO scheme. The process can be extended to arrive at a WENO-AO(7,3) scheme that is at best seventh order accurate by virtue of its centered stencil with seven zones and at worst third order accurate. We then recursively combine the above two schemes to arrive at a WENO-AO(7,5,3) scheme which can achieve seventh order accuracy when that is possible; graciously drop down to fifth order accuracy when that is the best one can do; and also operate stably with an r = 3 CWENO scheme when that is the only thing

  15. [Population structure of Polythore gigantea (Odonata: Polythoridae) in lotic systems with different conservation states in Antioquia-Colombia].

    Science.gov (United States)

    Altamiranda-S, Mariano; Ortega-M, Oscar

    2012-09-01

    The knowledge about population structure and dynamics of some neotropical species, especially those living in lotic systems is still barely studied. This study had the aim to assess if the conservation status of some lotic systems, is related to some demographic variables of P. gigantea, so this may be used as a model for ecological monitoring. For this, we evaluated the population structure of P. gigantea three times per month (almost one sampling event every eight days) in four streams of the state of Antioquia, Colombia, from March-June 2009. The specimens were collected using entomological nets along a transect of 200m in the littoral zone of each stream. The insects were marked on the wings and the population size was estimated with the mark-recapture method. Our results showed that the largest population size was recorded for the stream "La Catedral" with aprox 299 individuals, followed by the stream "La Doctora" with 218 individuals. Nevertheless, no significant differences in population size among the evaluated streams were found; and no statistical relationships were found between vegetation variables and the population size of P. gigantea. However, taking into account the limited dispersal capacity of P. gigantea, its survival in the studied streams was considered to be at risk, due to the continuous modification of large riparian forest areas, which cause the increase of forest patches, with different levels of interconnection, and hinder long-term permanence of populations.

  16. Comparative transcriptomics of convergent evolution: different genes but conserved pathways underlie caste phenotypes across lineages of eusocial insects.

    Science.gov (United States)

    Berens, Ali J; Hunt, James H; Toth, Amy L

    2015-03-01

    An area of great interest in evolutionary genomics is whether convergently evolved traits are the result of convergent molecular mechanisms. The presence of queen and worker castes in insect societies is a spectacular example of convergent evolution and phenotypic plasticity. Multiple insect lineages have evolved environmentally induced alternative castes. Given multiple origins of eusociality in Hymenoptera (bees, ants, and wasps), it has been proposed that insect castes evolved from common genetic "toolkits" consisting of deeply conserved genes. Here, we combine data from previously published studies on fire ants and honey bees with new data for Polistes metricus paper wasps to assess the toolkit idea by presenting the first comparative transcriptome-wide analysis of caste determination among three major hymenopteran social lineages. Overall, we found few shared caste differentially expressed transcripts across the three social lineages. However, there is substantially more overlap at the levels of pathways and biological functions. Thus, there are shared elements but not on the level of specific genes. Instead, the toolkit appears to be relatively "loose," that is, different lineages show convergent molecular evolution involving similar metabolic pathways and molecular functions but not the exact same genes. Additionally, our paper wasp data do not support a complementary hypothesis that "novel" taxonomically restricted genes are related to caste differences. © The Author 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  17. Energy reserves of Artibeus lituratus (Chiroptera: Phyllostomidae) in two areas with different degrees of conservation in Minas Gerais, Brazil.

    Science.gov (United States)

    Melo, B E S; Barros, M S; Carvalho, T F; Amaral, T S; Freitas, M B

    2012-02-01

    Forest fragmentation associated with the expansion of human development is a phenomenon that occurs worldwide. Studies reveal that there have been both a decline in species diversity and a decrease in Neotropical bat population size because of habitat loss. The aim of this study was to investigate whether human action has been affecting the food availability to wildlife species, which could impact the storage of body energy reserves. For this purpose, fruit-eating bats (Artibeus lituratus) were collected in two areas in Minas Gerais state, Brazil. The concentrations of plasma glucose, as well as glycogen, lipids and protein in liver in muscles were performed, in addition to adipose tissue weight and carcass fatty acids. Our results indicate that fat reserves were significantly lower in most tested tissues (muscle of the hindlimbs, breast muscles, adipose tissue and carcass) in animals collected in the region with a higher degree of human disturbance. The other parameters showed no significant differences in the groups collected at different locations. In conclusion, we suggest that human action on the environment may be affecting the storage of body fat energy reserves of this species during the autumn, particularly in metropolitan region areas of Belo Horizonte, MG - Brazil, requiring special attention to the species conservation.

  18. Energy reserves of Artibeus lituratus (Chiroptera: Phyllostomidae in two areas with different degrees of conservation in Minas Gerais, Brazil

    Directory of Open Access Journals (Sweden)

    BES Melo

    Full Text Available Forest fragmentation associated with the expansion of human development is a phenomenon that occurs worldwide. Studies reveal that there have been both a decline in species diversity and a decrease in Neotropical bat population size because of habitat loss. The aim of this study was to investigate whether human action has been affecting the food availability to wildlife species, which could impact the storage of body energy reserves. For this purpose, fruit-eating bats (Artibeus lituratus were collected in two areas in Minas Gerais state, Brazil. The concentrations of plasma glucose, as well as glycogen, lipids and protein in liver in muscles were performed, in addition to adipose tissue weight and carcass fatty acids. Our results indicate that fat reserves were significantly lower in most tested tissues (muscle of the hindlimbs, breast muscles, adipose tissue and carcass in animals collected in the region with a higher degree of human disturbance. The other parameters showed no significant differences in the groups collected at different locations. In conclusion, we suggest that human action on the environment may be affecting the storage of body fat energy reserves of this species during the autumn, particularly in metropolitan region areas of Belo Horizonte, MG - Brazil, requiring special attention to the species conservation.

  19. A TVD SCHEME FOR INCOMPRESSIBLE FLOW COUPLED WITH DIFFERENT TURBULENCE MODLES ON A GROUND- MOUNTED SQUARE-RIB FLOW

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A finite-difference Total Variation Diminishing (TVD) numerical simulation model for coupling the Reynolds Averaged Navier-Stokes (RANS) equations, pressure-relative continuity equation and various k-ε turbulence models was developed to solve the incompressible flow based on the pseudo-compressibility method. The hyperbolicity of all these equations was studied and the discretization of the fully coupling equations with all the primal variables and source terms were made in this article. Numerical simulation for modeling the flow around a ground-mounted square rib was implemented and validated by comparing with the published wind tunnel experimental data. It is shown that such a numerical simulation method with a proper turbulence model has a very good accuracy to simulate the flow around a surface-mounted rib. It is concluded that the Renormalization Group (RNG) and Chen-Kim k-ε turbulence models have much better ability to predict the characteristics of the vortex structure and flow separation than the standard k-ε model.

  20. Comparative Evaluation of Cash Benefit Scheme of Janani Suraksha Yojana for Beneficiary Mothers from Different Health Care Settings of Rewa District, Madhya Pradesh, India.

    Directory of Open Access Journals (Sweden)

    Trivedi R

    2014-05-01

    Full Text Available Introduction: For better outcomes in mother and child health, Government of India launched the National Rural Health Mission (NRHM in 2005 with a major objective of providing accessible, affordable and quality health care to the rural population; especially the vulnerable. Reduction in MMR to 100/100,000 is one of its goals and the Janani Suraksha Yojana (JSY is the key strategy of NRHM to achieve this reduction. The JSY, as a safe motherhood intervention and modified alternative of the National Maternity Benefit Scheme (NMBS, has been implemented in all states and Union territories with special focus on low performing states. The main objective and vision of JSY is to reduce maternal, neo-natal mortality and promote institutional delivery among the poor pregnant women of rural and urban areas. This scheme is 100% centrally sponsored and has an integrated delivery and post delivery care with the help of a key person i.e. ASHA (Accredited Social Health Activist, followed by cash monetary help to the women. Objectives: 1To evaluate cash benefit service provided under JSY at different health care settings. 2 To know the perception and elicit suggestions of beneficiaries on quality of cash benefit scheme of JSY. Methodology: This is a health care institute based observational cross sectional study including randomly selected 200 JSY beneficiary mothers from the different health care settings i.e., Primary Health Centres, Community Health Centres, District Hospital and Medical College Hospital of Rewa District of Madhya Pradesh state. Data was collected with the help of set pro forma and then analysed with Epi Info 2000. Chi square test was applied appropriately. Results: 60% and 80% beneficiaries from PHC and CHC received cash within 1 week after discharge whereas 100% beneficiaries of District Hospital and Medical College Hospital received cash at the time of discharge; the overall distribution of time of cash disbursement among beneficiaries of

  1. MODELING OF THREE-PHASE THREE LEG TRANSFORMER DEVICES FOR ENGINEERING CALCULATIONS OF ASYMMETRICAL MODES FOR DIFFERENT SCHEMES OF WINDING CONNECTIONS

    Directory of Open Access Journals (Sweden)

    Bosneaga V.A

    2013-08-01

    Full Text Available The model is proposed for the calculation and research of steady state asymmetric modes and transients in three-phase three legs transformer devices with arbitrary diagram of windings connection, taking into account the electromagnetic coupling of the windings, located on different legs. Using as an example distribution transformer of 10/0.4 kV calculations and analysis were performed of the most characteristic steady asymmetrical modes, that occur during short circuit, phase failure, unbalanced load for the most common windings connections and, in particular, associated with the occurrence of zero sequence magnetic flow. For the considered regimes and schemes vector diagrams were constructed for currents and voltages as well as for the relative values of magnetic flow, which give a clear idea about their particular features.

  2. The stability and convergence of an explicit difference scheme for the Schrödinger equation on an infinite domain by using artificial boundary conditions

    Science.gov (United States)

    Sun, Zhi-zhong

    2006-12-01

    This article is concerned with the numerical solution to the time-dependent Schrödinger equation on an infinite domain. Two exact artificial boundary conditions are introduced to reduce the original problem into an initial boundary value problem with a finite computational domain. The artificial boundary conditions involve the 1/2 order fractional derivative in t. Then, a fully discrete explicit three-level difference scheme is derived. The truncation errors are analyzed in detail. The stability and convergence with the convergence order of O( h3/2 + τh-1/2) are proved under the condition τ/ h2 < 1/2 by the energy method. A numerical example is given to demonstrate the accuracy and efficiency of the proposed method. Two open problems are brought forward at the end of the article.

  3. Solitary wave of the Korteweg-de Vries equation based on lattice Boltzmann model with three conservation laws

    Science.gov (United States)

    Wang, Huimin

    2017-01-01

    In this paper, a new lattice Boltzmann model for the Korteweg-de Vries (KdV) equation is proposed. By using the Chapman-Enskog expansion and the multi-scale time expansion, a series of partial differential equations in different time scales and several higher- order moments of equilibrium distribution functions are obtained. In order to make the scheme obey the three conservation laws of the KdV equation, two equilibrium distribution functions are used and a correlation between the first conservation law and the second conservation law is constructed. In numerical examples, the numerical results of the KdV equation obtained by this scheme are compared with those results obtained by the previous lattice Boltzmann model. Numerical experiments demonstrate this scheme can be used to reduce the truncation error of the lattice Boltzmann scheme and preserve the three conservation laws.

  4. The Number, Organization, and Size of Polymorphic Membrane Protein Coding Sequences as well as the Most Conserved Pmp Protein Differ within and across Chlamydia Species.

    Science.gov (United States)

    Van Lent, Sarah; Creasy, Heather Huot; Myers, Garry S A; Vanrompay, Daisy

    2016-01-01

    Variation is a central trait of the polymorphic membrane protein (Pmp) family. The number of pmp coding sequences differs between Chlamydia species, but it is unknown whether the number of pmp coding sequences is constant within a Chlamydia species. The level of conservation of the Pmp proteins has previously only been determined for Chlamydia trachomatis. As different Pmp proteins might be indispensible for the pathogenesis of different Chlamydia species, this study investigated the conservation of Pmp proteins both within and across C. trachomatis,C. pneumoniae,C. abortus, and C. psittaci. The pmp coding sequences were annotated in 16 C. trachomatis, 6 C. pneumoniae, 2 C. abortus, and 16 C. psittaci genomes. The number and organization of polymorphic membrane coding sequences differed within and across the analyzed Chlamydia species. The length of coding sequences of pmpA,pmpB, and pmpH was conserved among all analyzed genomes, while the length of pmpE/F and pmpG, and remarkably also of the subtype pmpD, differed among the analyzed genomes. PmpD, PmpA, PmpH, and PmpA were the most conserved Pmp in C. trachomatis,C. pneumoniae,C. abortus, and C. psittaci, respectively. PmpB was the most conserved Pmp across the 4 analyzed Chlamydia species.

  5. Do Farmers Using Conventional and Non-Conventional Systems of Agriculture Have Different Perceptions of the Diversity of Wild Birds? Implications for Conservation.

    Science.gov (United States)

    Silva-Andrade, Horasa Lima; de Andrade, Luciano Pires; Muniz, Lauana Souza; Telino-Júnior, Wallace Rodrigues; Albuquerque, Ulysses Paulino; Lyra-Neves, Rachel Maria

    2016-01-01

    Farmers' perceptions of birds' interactions with agricultural production systems are fundamental to species conservation efforts. In the present study, we evaluated the perceptions of birds held by farmers who engage in conventional and non-conventional agricultural production processes and the implications of potential differences in these perceptions on species conservation. To accomplish this, data were collected using questionnaires, semi-structured interviews, and other complementary sources of information gathered from 191 farmers in northeastern Brazil. Although some similarities were identified among the farmers in their perceptions and local ecological knowledge (LEK) of birds, differences existed between the conventional and non-conventional farmers in their attitudes toward, conflicts with, and usage of bird species. Compared to the conventional farmers, the non-conventional farmers could identify more bird species, possessed more favorable attitudes toward birds, and engaged in practices more beneficial to the conservation of avifauna. The perceptions that were identified were related to the type of agriculture practiced, and such perceptions may affect the conservation of bird species. Therefore, the adoption of certain agricultural practices has important implications for conservation. Our results indicate the need for investment in public policies, programs and actions that account for farmers' knowledge and perceptions. Such investments will contribute to the development and adoption of practices supporting wild bird conservation in agricultural areas.

  6. Do Farmers Using Conventional and Non-Conventional Systems of Agriculture Have Different Perceptions of the Diversity of Wild Birds? Implications for Conservation.

    Directory of Open Access Journals (Sweden)

    Horasa Lima Silva-Andrade

    Full Text Available Farmers' perceptions of birds' interactions with agricultural production systems are fundamental to species conservation efforts. In the present study, we evaluated the perceptions of birds held by farmers who engage in conventional and non-conventional agricultural production processes and the implications of potential differences in these perceptions on species conservation. To accomplish this, data were collected using questionnaires, semi-structured interviews, and other complementary sources of information gathered from 191 farmers in northeastern Brazil. Although some similarities were identified among the farmers in their perceptions and local ecological knowledge (LEK of birds, differences existed between the conventional and non-conventional farmers in their attitudes toward, conflicts with, and usage of bird species. Compared to the conventional farmers, the non-conventional farmers could identify more bird species, possessed more favorable attitudes toward birds, and engaged in practices more beneficial to the conservation of avifauna. The perceptions that were identified were related to the type of agriculture practiced, and such perceptions may affect the conservation of bird species. Therefore, the adoption of certain agricultural practices has important implications for conservation. Our results indicate the need for investment in public policies, programs and actions that account for farmers' knowledge and perceptions. Such investments will contribute to the development and adoption of practices supporting wild bird conservation in agricultural areas.

  7. Effect of different mulching materials on maize growth and yield in conservation agriculture systems of sub-humid Zimbabwe

    Directory of Open Access Journals (Sweden)

    W. Mupangwa

    2016-06-01

    Full Text Available The introduction of conservation agriculture (CA for smallholders increased the competition for crop residues between crop and livestock enterprises of the mixed smallholder farming system. Smallholders practicing CA have resorted to using grass and leaf litter in addition to available crop residues. The effect of these different mulching materials on maize (Zea mays L. growth and yield is not well documented in smallholder CA systems of southern Africa. A two-year experiment was run in 2012/13 and 2013/14 seasons to evaluate the effect of maize residues, grass (Hyparrhenia filipendula (L. Stapf. and leaf litter that farmers are currently using and residues from leguminous species, sunhemp (Crotolaria juncea L. and Tephrosia (Tephrosia vogelii ((Hook f. on maize nitrogen (N uptake, growth and yield. Significant differences in soil water content across treatments were only observed during March in 2012/13 season. Maize residues retained more soil water and Tephrosia had the lowest soil water content when seasonal rainfall pattern was erratic. Grass and Tephrosia treatments had the lowest chlorophyll content. Conventional ploughing, maize residues and leaf litter had similar chlorophyll content which was significantly higher than grass and Tephrosia treatments. At a site with higher initial soil fertility conventional ploughing treatment out yielded the other treatments by 727–1265 kg ha−1. With more degraded sandy soil conventional practice had 119–430 kg ha−1 more maize grain than the CA treatments. With adequate fertilization, the mulching materials have a similar effect on maize growth in basins and direct seeding. Further studies on different application rates of mulching materials and mineral N fertilizer, and nutrient release patterns of these residues are critical in order to better understand soil fertility management under smallholder CA systems.

  8. THE RELAXING SCHEMES FOR HAMILTON-JACOBI EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    Hua-zhong Tang; Hua-mu Wu

    2001-01-01

    Hamilton-Jacobiequation appears frequently in applications, e.g., in differential games and control theory, and is closely related to hyperbolic conservation laws[3, 4, 12]. This is helpful in the design of difference approximations for Hamilton-Jacobi equation and hyperbolic conservation laws. In this paper we present the relaxing system for HamiltonJacobiequations in arbitrary space dimensions, and high resolution relaxing schemes for Hamilton-Jacobi equation, based on using the local relaxation approximation. The schemes are numerically tested on a variety of 1D and 2D problems, including a problem related to optimal control problem. High-order accuracy in smooth regions, good resolution of discontinuities, and convergence to viscosity solutions are observed.

  9. [Topsoil phosphorus forms and availability of different soil and water conservation plantations in typical black soil region, northeast China].

    Science.gov (United States)

    Yang, Xiao-Yan; Fan, Rui-Ying; Wang, En-Heng; Xia, Xiang-You; Chen, Xiang-Wei

    2014-06-01

    Aiming to understand soil phosphorus status of plantations in typical black soil region of Northeast China, the topsoil (0-10 cm) phosphorus fractionations and its availability were examined in four soil and water conservation plantations dominantly composed of Larix gmelini, Fraxinus mandshurica, Pinus sylvestris var. mongolica and Populus nigra var. italica x P. cathayan, respectively. The results showed that total P, Olsen-P and the concentration of different P fractionations in F. mandshurica and P. nigra var. italica x P. cathayan plantations were significantly higher than that of the other two coniferous plantations. Organic P was the major fractionation in the four plantations' topsoil, and sodium hydroxide extractable organic P (NaOH-Po ) representing moderately labile organic phosphorus was predominant, which accounted for 58.9% of total P. The contents of H2O-Pi and NaHCO3-P which were more labile to plant were lower, only accounting for 1.2% and 6.6% of total P, respectively. Except for NaHCO3-Po, all the other P fractions of four plantations correlated with each other, and they also had significant correlations with soil organic matter, total P, Olsen-P. Compared with the coniferous plantations, the broadleaf plantations presented higher availability of phosphorus.

  10. Differences of Anxiety Levels between Students of Natural Sciences and Social Studies Major Based on School Environmental Factors in Senior High Schools with Rintisan Sekolah Bertaraf Internasional Scheme

    Directory of Open Access Journals (Sweden)

    Arviana Adamantina Putri

    2014-08-01

    Full Text Available Background: Senior High Schools with Rintisan Sekolah Bertaraf Internasional (RSBI scheme are senior high schools that pilot international standards in learning methods and high curriculum targets. This factor may lead to a rise of anxiety amongst students, both for students in Natural Sciences major and Social Studies major. There are three factors which cause anxiety in the school environment, namely: dissatisfaction towards the curriculum, the teacher, and the school management. Methods: This study used retrospective cohort design. Subjects were selected using the convenience sampling method. Natural Sciences students (n=32 and Social Studies students (n=14 had their anxiety level measured using the Taylor Manifest Anxiety Scale. The dissatisfaction towards the school environment factors was assessed using a school evaluation questionnaire. Results: The anxiety measurement showed that students in both Natural Sciences and Social Studies major experienced severe anxiety (Natural Sciences vs. Social Studies: 75% vs. 86%. The study results based on the school evaluation questionnaire showed dissatisfactions towards the three school environmental factors (curriculum factor, Natural Sciences vs. Social Studies: 59% vs. 64%; teacher factor, Natural Sciences vs. Social Studies: 3% vs. 43%; school management factor, Natural Sciences vs. Social Studies: 3% vs. 14%. The chi-square test results showed that the difference in the anxiety levels between the students of Natural Sciences and Social Studies majors was insignificant (p>0.05. Conclusions: Students of Natural Sciences and Social Studies majors of senior high schools with RSBI scheme experienced severe anxiety. However, there is no strong evidence that the school environment causes this severe anxiety.

  11. Effect of revaccination using different schemes among adults with low or undetectable anti-HBs titers after hepatitis B virus vaccination.

    Science.gov (United States)

    Lin, Chao-Shuang; Xie, Shi-Bin; Liu, Jing; Zhao, Zhi-Xin; Chong, Yu-Tian; Gao, Zhi-Liang

    2010-10-01

    Our objective was to investigate the effect of various reimmunization schemes for hepatitis B in adults with low or undetectable anti-HBs titers. Over 2 years, 10 μg of Saccharomyces cerevisiae-recombinant hepatitis B virus (HBV) vaccine (synthesized in China) was used in at least one standardized scheme to immunize 2,310 healthy male and nonpregnant female adults. Of these, 240 subjects tested negative for hepatitis B markers. These 240 subjects were equally divided into 4 groups. The first group, designated Engerix-40, was revaccinated with 40 μg Engerix-B; the second, Engerix-20, was revaccinated with 20 μg Engerix-B; the third, Chinese-20, was revaccinated with 20 μg Chinese-made yeast-recombinant vaccine; and the last group, Chinese-10, was revaccinated with 10 μg Chinese-made yeast-recombinant vaccine. Blood samples were collected before and 1, 2, 8, and 12 months after the first injection. The anti-HBs-positive conversion rates of the Engerix-40, Engerix-20, and Chinese-20 groups were higher than that of the Chinese-10 group (P anti-HBs conversion rate increased in all groups, but values were significantly different from those for the other groups only in the Chinese-10 group (P anti-HBs geometric mean titers (GMTs) of the Engerix-40, Engerix-20, and Chinese-20 groups were higher than in the Chinese-10 group (P anti-HBs titers in subjects with low or undetectable titers after HBV vaccination.

  12. 一类对流扩散方程的特征-修正差分格式及最大模估计%MODIFIED CHARACTERISTIC DIFFERENCE SCHEME AND MAXIMUM NORM ESTIMATE FOR A KIND OF CONVECTION-DIFFUSION EQUATION

    Institute of Scientific and Technical Information of China (English)

    杜宁

    2002-01-01

    A new technique is introduced to approximate the values of the inter-polated points instead of using local quadratic interpolation. A modified charac-teristic difference scheme based on the new technique is formulated to treat a con-vection-diffusion problem of the form cu,+bux- (aux)x=f. Convergence and sta-bility of the scheme are analyzed, and an error estimate of O(△t+h2) in maxi-mum norm is presented.

  13. 20:60:20--differences in energy behaviour and conservation between and within households with electricity monitors.

    Directory of Open Access Journals (Sweden)

    Niamh Murtagh

    Full Text Available The introduction of electricity monitors (in-home displays; IHDs, which show accurate and up-to-the-minute energy usage, is expected to lead to reduction in consumption. Studies of feedback on domestic electricity use have generally supported this view. However, such studies also demonstrate wide variation between households. Examining the heterogeneity of responses is essential for understanding the actual and potential effectiveness of IHDs and in order to target interventions effectively. To explore differences between households' responses to IHDs, we conducted a qualitative study with 21 households who had an IHD for more than six months. Of the 21, only four households continued to refer to the IHD and the findings suggest that attempts to reduce energy consumption were situated in wider social and physical contexts. Further, the participants demonstrated energy saving behaviour before and outside of IHD usage. The patterns of energy behaviours and attempts at electricity conservation could best be understood by categorising the households into three types: the Monitor Enthusiasts (20%, the Aspiring Energy Savers (60% and the Energy Non-Engaged (20%. The factors of importance in energy behaviour differed between the categories. Financial savings contributed to efforts to reduce energy use but only up to boundaries which varied considerably between households. Social practices and social relationships appeared to constrain what actions households were prepared to undertake, illuminating aspects of inter-household variation. Within the household, all energy users were not equal and we found that women were particularly influential on energy use through their primary responsibility for domestic labour on behalf of the household. The implications of the findings for environmental campaigning are discussed.

  14. 20:60:20--differences in energy behaviour and conservation between and within households with electricity monitors.

    Science.gov (United States)

    Murtagh, Niamh; Gatersleben, Birgitta; Uzzell, David

    2014-01-01

    The introduction of electricity monitors (in-home displays; IHDs), which show accurate and up-to-the-minute energy usage, is expected to lead to reduction in consumption. Studies of feedback on domestic electricity use have generally supported this view. However, such studies also demonstrate wide variation between households. Examining the heterogeneity of responses is essential for understanding the actual and potential effectiveness of IHDs and in order to target interventions effectively. To explore differences between households' responses to IHDs, we conducted a qualitative study with 21 households who had an IHD for more than six months. Of the 21, only four households continued to refer to the IHD and the findings suggest that attempts to reduce energy consumption were situated in wider social and physical contexts. Further, the participants demonstrated energy saving behaviour before and outside of IHD usage. The patterns of energy behaviours and attempts at electricity conservation could best be understood by categorising the households into three types: the Monitor Enthusiasts (20%), the Aspiring Energy Savers (60%) and the Energy Non-Engaged (20%). The factors of importance in energy behaviour differed between the categories. Financial savings contributed to efforts to reduce energy use but only up to boundaries which varied considerably between households. Social practices and social relationships appeared to constrain what actions households were prepared to undertake, illuminating aspects of inter-household variation. Within the household, all energy users were not equal and we found that women were particularly influential on energy use through their primary responsibility for domestic labour on behalf of the household. The implications of the findings for environmental campaigning are discussed.

  15. 20∶60∶20 - Differences in Energy Behaviour and Conservation between and within Households with Electricity Monitors

    Science.gov (United States)

    Murtagh, Niamh; Gatersleben, Birgitta; Uzzell, David

    2014-01-01

    The introduction of electricity monitors (in-home displays; IHDs), which show accurate and up-to-the-minute energy usage, is expected to lead to reduction in consumption. Studies of feedback on domestic electricity use have generally supported this view. However, such studies also demonstrate wide variation between households. Examining the heterogeneity of responses is essential for understanding the actual and potential effectiveness of IHDs and in order to target interventions effectively. To explore differences between households' responses to IHDs, we conducted a qualitative study with 21 households who had an IHD for more than six months. Of the 21, only four households continued to refer to the IHD and the findings suggest that attempts to reduce energy consumption were situated in wider social and physical contexts. Further, the participants demonstrated energy saving behaviour before and outside of IHD usage. The patterns of energy behaviours and attempts at electricity conservation could best be understood by categorising the households into three types: the Monitor Enthusiasts (20%), the Aspiring Energy Savers (60%) and the Energy Non-Engaged (20%). The factors of importance in energy behaviour differed between the categories. Financial savings contributed to efforts to reduce energy use but only up to boundaries which varied considerably between households. Social practices and social relationships appeared to constrain what actions households were prepared to undertake, illuminating aspects of inter-household variation. Within the household, all energy users were not equal and we found that women were particularly influential on energy use through their primary responsibility for domestic labour on behalf of the household. The implications of the findings for environmental campaigning are discussed. PMID:24642946

  16. On K-Line and K x K Block Iterative Schemes for a Problem Arising in 3-D Elliptic Difference Equations.

    Science.gov (United States)

    1980-01-01

    Seidel method and the SOR method Cas well as the optimal overrelaxation parameter wb) are determined by the spectral radius of the block Jacobi scheme...scheme using klines and k x k blocks. These spectral radii were computed by the power method. The Gauss- Seidel method was chosen because the general

  17. DEVELOPMENT AND APPLICATIONS OF WENO SCHEMES IN CONTINUUM PHYSICS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    This paper briefly presents the general ideas of high order accurate weighted essentially non-oscillatory (WENO) schemes, and describes the similarities and differences of the two classes of WENO schemes: finite volume schemes and finite difference schemes. We also briefly mention a recent development of WENO schemes,namely an adaptive approach within the finite difference framework using smooth time dependent curvilinear coordinates.``

  18. A fourth order accuracy summation-by-parts finite difference scheme for acoustic reverse time migration in boundary-conforming grids

    Science.gov (United States)

    Wang, Ying; Zhou, Hui; Yuan, Sanyi; Ye, Yameng

    2017-01-01

    The fourth order accuracy finite difference scheme is known advantageous in reducing memory and improving efficiency. Summation-by-parts finite difference operator is a natural way for wavefield simulation in complicated domains containing surface topography and irregular interfaces. The application of summation-by-parts method guarantees the stability of numerical approximation for heterogeneous media on curvilinear grids. This paper extends the second order summation-by-parts finite difference method to the fourth order case for the discretization of acoustic wave equation and perfect matched layer in boundary-conforming grids. In particular, the implementation of the fourth order method for wavefield simulation and reverse time migration in complicated domains can significantly improve the efficiency and decrease the storage. The elliptic method is applied for boundary-conforming grid generation in complicated domains. Under such grids, the two-dimensional acoustic wave equation in second order displacement formulation is compactly reformulated for forward modeling and reverse time migration, and the symmetric and compact form of perfectly matched layers expressed in a curvilinear coordinate system are applied to suppress artificial reflections. The discretizations of the acoustic wave equation and perfectly matched layer formula are fourth and second order accuracy in space and time respectively, where the spatial discretization satisfies the principle of summation-by-parts and is stable. Numerical experiments are presented to compare the accuracy of the second with fourth order summation-by-parts finite difference methods and to evaluate the efficiency of reverse time migration by using these two methods. As well, comparisons are performed between the fourth order accuracy summation-by-parts finite difference method and central finite difference method to illustrate the stability superiority of summation-by-parts operators.

  19. 构造高分辨率格式的反扩散混合法%Mixed Anti-diffusion Method for High Resolution Schemes

    Institute of Scientific and Technical Information of China (English)

    LI Rong-hua; ZHANG Wei-wei

    2004-01-01

    In this paper we study a kind of mixed anti-diffusion method for partial differntial equations. Firstly, we use the method to construct some difference schemes for the conservation laws. The schemes are of second order accuracy and are total variation decreasing (TVD). In particular, there are only three knots involved in the schemes. Secondly, we extend the method to construct a few high accuracy difference schemes for elliptic and parabolic equations. Numerical experiments are carried out to illustrate the efficiency of the method.

  20. Comparison Between Structural Analysis of Residential Building (Flat Scheme Subjected to Gravity With Respect to Seismic Forces (In zone II and zone III For Different Storey Heights

    Directory of Open Access Journals (Sweden)

    Pranita R. Kayarkar

    2014-11-01

    Full Text Available The recent development in methods to analyze the RC frame structure brings us to this study. This paper is approach to introduce the comparison between structural analysis of Residential building (Flat Scheme subjected to gravity with respect to seismic forces ( in zone II and zone III for different storey heights. For structural engineers, seismic load should be considered as important aspect that needs to be included in the building design. However majority of buildings constructed in India are designed for gravity loading only and poorly detailed to accommodate lateral loads. The purpose of this paper is to investigate the comparison between structural analysis of residential building subjected to gravity with respect to seismic forces in zone II and zone III for different storey heights. The analysis for residential building (G+3 is carried out by using software SAP by seismic coefficient method. Columns, beams and footing has been drawn. Microsoft office Excel 2007 programs were used for drafting , and analysis of columns, beams and footing. This analysis gives better understanding the seismic performance of buildings. The results show that the building which is designed only for gravity load is found inadequate to resist seismic load in zone II and zone III.

  1. Influence of Difference Schemes and Limiters on Numerical Simulation of Double-Ellipsoid%差分格式及限制器对双椭球数值模拟的影响

    Institute of Scientific and Technical Information of China (English)

    胡俊; 张磊; 任坦

    2012-01-01

    为探究差分格式和限制器对高超声速热流密度计算结果的影响,以N-S方程为基本控制方程,采用FDS的Roe格式、FVS的van Leer格式对双椭球模型进行了数值模拟,并采用Roe格式选取min mod、van Leer、Osher_C三种限制器对双椭球进行了进一步数值模拟.研究了不同空间差分格式、不同限制器对双椭球压力、气动热数值模拟结果的影响,并对双椭球模型的流场进行了相关分析.研究结果表明:差分格式和限制器对压力系数影响不大,而对热流密度影响较大,采用minmod限制器的Roe格式计算精度最高.%In order to study the effect of difference schemes and limiters, on the basis of Navier-Stokes equation, the flow fields around double-ellipsoid were simulated numerically using Roe scheme of FDS and van Leer scheme of FVS. The limiters of min mod, van Leer, Osher_C under Roe difference scheme were also simulated. The effects of different difference schemes and limiters on the simulation results of double-ellipsoid's aerodynamics and aerothermodynamics were researched and the flow fields of double-ellipsoid were analyzed. The results indicate that the effect of difference schemes and limiters on pressure is less than heat flux and Ree scheme with minmod limitors can obtain high accuracy results.

  2. Is there an ideal way to initiate antiplatelet therapy with aspirin? A crossover study on healthy volunteers evaluating different dosing schemes with whole blood aggregometry

    Directory of Open Access Journals (Sweden)

    Overbeck Ursula

    2011-04-01

    Full Text Available Abstract Background Guidelines recommend an early initiation of aspirin treatment in patients with acute cerebral ischemia. Comparative studies on the best starting dose for initiating aspirin therapy to achieve a rapid antiplatelet effect do not exist. This study evaluated the platelet inhibitory effect in healthy volunteers by using three different aspirin loading doses to gain a model for initiating antiplatelet treatment in acute strokes patients. Methods Using whole blood aggregometry, this study with a prospective, uncontrolled, open, crossover design examined 12 healthy volunteers treated with three different aspirin loading doses: intravenous 500 mg aspirin, oral 500 mg aspirin, and a course of 200 mg aspirin on two subsequent days followed by a five-day course of 100 mg aspirin. Aspirin low response was defined as change of impedance exceeding 0 Ω after stimulation with arachidonic acid. Results Sufficient antiplatelet effectiveness was gained within 30 seconds when intravenous 500 mg aspirin was used. The mean time until antiplatelet effect was 74 minutes for 500 mg aspirin taken orally and 662 minutes (11.2 hours for the dose scheme with 200 mg aspirin with a high inter- and intraindividual variability in those two regimes. Platelet aggregation returned to the baseline range during the wash-out phase within 4 days. Conclusion Our study reveals that the antiplatelet effect differs significantly between the three different aspirin starting dosages with a high inter- and intraindividual variability of antiplatelet response in our healthy volunteers. To ensure an early platelet inhibitory effect in acute stroke patients, it could be advantageous to initiate the therapy with an intravenous loading dose of 500 mg aspirin. However, clinical outcome studies must still define the best way to initiate antiplatelet treatment with aspirin.

  3. Stability analysis of the von Neumann--Richtmyer difference scheme with rate dependent materials relations. Part 2. Subcycling and the Malvern relation. [Application to WONDY

    Energy Technology Data Exchange (ETDEWEB)

    Hicks, D.L.

    1977-05-01

    Stability criteria are developed for solving problems involving rate-dependent material properties in hydrocodes such as WONDY. As severe restrictions in the allowable timestep size result for small relaxation times, subcycling was introduced to solve this problem. That is, if the subcycle number (m) is large enough, then the timestep restriction as it exists in WONDY is sufficient for stability; this is shown herein for the case of a simple backward difference subcycling scheme for the Malvern rate-dependent material relation. The problem of precisely how large m must be for a given ratio of the timestep to the relaxation time, h = ..delta..t/tau, was studied. Although the form of solution for m as a function of h is complicated, it can be incorporated easily into WONDY. In the extreme cases of h very small or large, the solution can be simply stated: if h is very small, then m = 1 suffices; if h greater than 2, then m greater than or equal to h suffices. The fact that the solution reduces to m greater than or equal to h for large h is an elegant and interesting result.

  4. Performance Analysis of Mobile WiMAX System using Turbo Coding Technique for Different Modulation Schemes under AWGN and Rayleigh Channel

    Directory of Open Access Journals (Sweden)

    P. Samundiswary

    2013-02-01

    Full Text Available In wireless communication, future demands must be met using more data throughput wireless technologies. Since bandwidth is limited and user demand continues to grow. This problem could be solved by WiMAX technology based on IEEE 802.16e specifications, which provides high data services on mobile environment. So, to support high data rate traffic, the error correction could be enhanced by incorporating a better channel coding technique in mobile WiMAX physical layer. Further, coding technique is used for providing reliable information through the transmission channel to the user. It is used to reduce the level of noise and interferences in electronic medium. The amount of error detection and correction required and its effectiveness depends on the signal to noise ratio. The advantages of Forward Error Correction (FEC are that a back-channel is not required, or that retransmission of data can often be avoided, at the cost of higher bandwidth requirements on average. In this paper, the performance of mobile WiMAX system with convolutional turbo coding is determined and analyzed for various modulation schemes under different channels. The BER performance of mobile WiMAX system using convolutional turbo Coding is determined and compared with the existing concatenated Reed Solomon(RS coding in the presence of AWGN and Rayleigh Channel. From the simulation results, it is verified that convolutional turbo coding provides better BER performance than concatenated RS coding

  5. A stable interface element scheme for the p-adaptive lifting collocation penalty formulation

    Science.gov (United States)

    Cagnone, J. S.; Nadarajah, S. K.

    2012-02-01

    This paper presents a procedure for adaptive polynomial refinement in the context of the lifting collocation penalty (LCP) formulation. The LCP scheme is a high-order unstructured discretization method unifying the discontinuous Galerkin, spectral volume, and spectral difference schemes in single differential formulation. Due to the differential nature of the scheme, the treatment of inter-cell fluxes for spatially varying polynomial approximations is not straightforward. Specially designed elements are proposed to tackle non-conforming polynomial approximations. These elements are constructed such that a conforming interface between polynomial approximations of different degrees is recovered. The stability and conservation properties of the scheme are analyzed and various inviscid compressible flow calculations are performed to demonstrate the potential of the proposed approach.

  6. Analysis of different treatments schemes of ERT dataset in view of monitoring the structure of a soil tilled layer in space and in time

    Science.gov (United States)

    Seger, Maud; Besson, Arlene; Richard, Guy; Nicoullaud, Bernard; Giot, Guillaume; Cousin, Isabelle

    2010-05-01

    resistivity models often unrealistic. This point was particularly problematic in a studied case that we have conducted in field: it concerned the space and time monitoring of the soil structure by ERT measurements. The time monitoring was conducting during the entire period of growing, so ERT measurements were realized in wet as well as in dry conditions. In addition to that, we used an original experimental design of 72 electrodes spaced 10 cm apart, which was very sensitive to small heterogeneities in the near surface of the soil. The objective of the study was then to test different schemes of data treatments in view of obtaining the best model of electrical resistivity that correspond to the monitoring in space and time of the structural changes of a loamy tilled layer. These schemes gathered filtering strategies of raw data and various iterative least-square inversions options using Marquardt's method or smoothest inversion implemented in Res2Dinv software (Loke and Barker, 1999). They were comforted by an analysis of sensibility matrix. The time lapse method was also compared to independent inversion method. The resistivity values were converted at a given reference temperature. We discussed then the reliability, the quality and inconsistencies of resistivity models by comparison to the real structure features described on soil pits dug in the field after each ERT measurements. This work was part of the FP7-DIGISOIL project on "Integrated system of data collection technologies for mapping soil properties".

  7. Monotonicity Conditions for Multirate and Partitioned Explicit Runge-Kutta Schemes

    KAUST Repository

    Hundsdorfer, Willem

    2013-01-01

    Multirate schemes for conservation laws or convection-dominated problems seem to come in two flavors: schemes that are locally inconsistent, and schemes that lack mass-conservation. In this paper these two defects are discussed for one-dimensional conservation laws. Particular attention will be given to monotonicity properties of the multirate schemes, such as maximum principles and the total variation diminishing (TVD) property. The study of these properties will be done within the framework of partitioned Runge-Kutta methods. It will also be seen that the incompatibility of consistency and mass-conservation holds for ‘genuine’ multirate schemes, but not for general partitioned methods.

  8. Differences across health care systems in outcome and cost-utility of surgical and conservative treatment of chronic low back pain: a study protocol

    Directory of Open Access Journals (Sweden)

    Barz Thomas

    2008-06-01

    Full Text Available Abstract Background There is little evidence on differences across health care systems in choice and outcome of the treatment of chronic low back pain (CLBP with spinal surgery and conservative treatment as the main options. At least six randomised controlled trials comparing these two options have been performed; they show conflicting results without clear-cut evidence for superior effectiveness of any of the evaluated interventions and could not address whether treatment effect varied across patient subgroups. Cost-utility analyses display inconsistent results when comparing surgical and conservative treatment of CLBP. Due to its higher feasibility, we chose to conduct a prospective observational cohort study. Methods This study aims to examine if 1. Differences across health care systems result in different treatment outcomes of surgical and conservative treatment of CLBP 2. Patient characteristics (work-related, psychological factors, etc. and co-interventions (physiotherapy, cognitive behavioural therapy, return-to-work programs, etc. modify the outcome of treatment for CLBP 3. Cost-utility in terms of quality-adjusted life years differs between surgical and conservative treatment of CLBP. This study will recruit 1000 patients from orthopaedic spine units, rehabilitation centres, and pain clinics in Switzerland and New Zealand. Effectiveness will be measured by the Oswestry Disability Index (ODI at baseline and after six months. The change in ODI will be the primary endpoint of this study. Multiple linear regression models will be used, with the change in ODI from baseline to six months as the dependent variable and the type of health care system, type of treatment, patient characteristics, and co-interventions as independent variables. Interactions will be incorporated between type of treatment and different co-interventions and patient characteristics. Cost-utility will be measured with an index based on EQol-5D in combination with cost

  9. Effectiveness of soil and water conservation structures in reducing runoff and soil loss for different land use and slope gradients: Case study from northern Ethiopia

    Science.gov (United States)

    Taye, Gebeyehu; Poesen, Jean; Vanwesemael, Bas; Vanmaercke, Matthias; Teka, Daniel; Deckers, Jozef; Goosse, Tom; Maetens, Willem; Nyssen, Jan; Hallet, Vincent; Haregeweyn, Nigussie

    2014-05-01

    Land degradation and recurrent drought are the major threats to rain-fed agriculture in the semi-arid Ethiopian highlands. To mitigate drought and to ensure food security in the Tigray region, water harvesting using reservoirs for irrigation development has become a priority since 1990. However, the success of water harvesting in reservoirs is limited due to the reduced inflow. As a result, less area is irrigated than originally planned. The aim of this study is to investigate the effectiveness of soil and water conservation (SWC) structures in reducing runoff and soil loss under different land use types and slope gradients. Six runoff measuring sites, corresponding to three slope gradients (5%, 12% and 16%) were established for cropland and rangeland in the Mayleba catchment (Tigray). In total, 21 large runoff plots (with lengths of 60 to 100 m and widths of 10 m) were monitored daily for runoff production and soil loss during the main rainy season (July-September) in 2010. For each site in cropland, three plots were installed and treated with stone bunds and stone bunds with trenches in addition to a control plot. At each site in rangeland four runoff plots were installed: a plot treated with stone bunds, a plot treated with trenches, a plot treated with stone bunds and trenches as well as a control plot. Overall uncertainties on the runoff and soil loss measurements were estimated by means of Monte Carlo simulation techniques. The results show that the seasonal runoff coefficient (RCs) was much higher for rangeland (0.38 < RCs < 0.50) compared to RCs-values for cropland (0.11 < RCS < 0.15). Seasonal soil loss (SLs) values were five to six times larger on rangeland (28.6 < SLs < 50.0 ton ha-1) compared to that for cropland (4.6 < SLs < 11.4 ton ha-1). All tested SWC structures are effective in reducing runoff and soil loss compared to control plots. However, reduction in RCs were relatively much smaller than reductions in SLs. Trenches and stone bunds with

  10. 外存分配策略对磁盘存储效率的影响研究%Impact on the Efficiency of Disk Storage Using Difference Disk Allocation Schemes

    Institute of Scientific and Technical Information of China (English)

    薄杨; 董坤

    2012-01-01

    本文总结了几种常见的磁盘分配策略,对各磁盘分配策略的分配过程进行了分析和研究,分析了几种常见磁盘分配策略各自的特点,并通过对比总结了不同外存分配方式对磁盘存储效率可能产生的影响,且对外存分配策略的发展进行了展望。%This paper summarizes some disk allocation schemes,which are researched and analyzed.The impact on the efficiency of disk storage using difference disk allocation schemes is summarized.And the paper also expects the development of the disk allocation schemes.

  11. Optimal Numerical Schemes for Compressible Large Eddy Simulations

    Science.gov (United States)

    Edoh, Ayaboe; Karagozian, Ann; Sankaran, Venkateswaran; Merkle, Charles

    2014-11-01

    The design of optimal numerical schemes for subgrid scale (SGS) models in LES of reactive flows remains an area of continuing challenge. It has been shown that significant differences in solution can arise due to the choice of the SGS model's numerical scheme and its inherent dissipation properties, which can be exacerbated in combustion computations. This presentation considers the individual roles of artificial dissipation, filtering, secondary conservation (Kinetic Energy Preservation), and collocated versus staggered grid arrangements with respect to the dissipation and dispersion characteristics and their overall impact on the robustness and accuracy for time-dependent simulations of relevance to reacting and non-reacting LES. We utilize von Neumann stability analysis in order to quantify these effects and to determine the relative strengths and weaknesses of the different approaches. Distribution A: Approved for public release, distribution unlimited. Supported by AFOSR (PM: Dr. F. Fahroo).

  12. On the application of subcell resolution to conservation laws with stiff source terms

    Science.gov (United States)

    Chang, Shih-Hung

    1989-01-01

    LeVeque and Yee recently investigated a one-dimensional scalar conservation law with stiff source terms modeling the reacting flow problems and discovered that for the very stiff case most of the current finite difference methods developed for non-reacting flows would produce wrong solutions when there is a propagating discontinuity. A numerical scheme, essentially nonoscillatory/subcell resolution - characteristic direction (ENO/SRCD), is proposed for solving conservation laws with stiff source terms. This scheme is a modification of Harten's ENO scheme with subcell resolution, ENO/SR. The locations of the discontinuities and the characteristic directions are essential in the design. Strang's time-splitting method is used and time evolutions are done by advancing along the characteristics. Numerical experiment using this scheme shows excellent results on the model problem of LeVeque and Yee. Comparisons of the results of ENO, ENO/SR, and ENO/SRCD are also presented.

  13. Breeding schemes in reindeer husbandry

    Directory of Open Access Journals (Sweden)

    Lars Rönnegård

    2003-04-01

    Full Text Available The objective of the paper was to investigate annual genetic gain from selection (G, and the influence of selection on the inbreeding effective population size (Ne, for different possible breeding schemes within a reindeer herding district. The breeding schemes were analysed for different proportions of the population within a herding district included in the selection programme. Two different breeding schemes were analysed: an open nucleus scheme where males mix and mate between owner flocks, and a closed nucleus scheme where the males in non-selected owner flocks are culled to maximise G in the whole population. The theory of expected long-term genetic contributions was used and maternal effects were included in the analyses. Realistic parameter values were used for the population, modelled with 5000 reindeer in the population and a sex ratio of 14 adult females per male. The standard deviation of calf weights was 4.1 kg. Four different situations were explored and the results showed: 1. When the population was randomly culled, Ne equalled 2400. 2. When the whole population was selected on calf weights, Ne equalled 1700 and the total annual genetic gain (direct + maternal in calf weight was 0.42 kg. 3. For the open nucleus scheme, G increased monotonically from 0 to 0.42 kg as the proportion of the population included in the selection programme increased from 0 to 1.0, and Ne decreased correspondingly from 2400 to 1700. 4. In the closed nucleus scheme the lowest value of Ne was 1300. For a given proportion of the population included in the selection programme, the difference in G between a closed nucleus scheme and an open one was up to 0.13 kg. We conclude that for mass selection based on calf weights in herding districts with 2000 animals or more, there are no risks of inbreeding effects caused by selection.

  14. GECoRe: A New Geometrically Exact Remapping Scheme on the Sphere

    Science.gov (United States)

    Ullrich, P. A.; Lauritzen, P. H.

    2008-12-01

    Land, ocean and atmospheric models are often implemented using different grid schemes, individually designed to enhance the accuracy or capture features unique to their respective model. However, coupling between these models requires accurate remapping of quantities between grids, and so efficient algorithms are often needed to handle these computations. Two grids where remapping is particularly important are the so-called cubed sphere grid and the regular latitude-longitude (RLL) grid. Notably, modern dynamical cores have moved towards implementing climate models on the cubed sphere, since it does not possess the polar singularity problems present in the RLL grid. Most existing schemes fail to take advantage of geometrical symmetries between these grids when performing remapping, and hence accuracy of the calculations is lost. Hence, a new geometrically exact conservative remapping scheme (GECoRe) is proposed and compared against the existing CaRS (Cascade Remapping between Spherical grids) and SCRIP (Spherical Coordinate Remapping and Interpolation Package) schemes. In our idealized comparison, we find that the new geometrically exact conservative remapping scheme greatly improves the accuracy of previous remapping schemes by several orders of magnitude while maintaining a practically identical computational cost.

  15. All-atom molecular dynamics simulations reveal significant differences in interaction between antimycin and conserved amino acid residues in bovine and bacterial bc1 complexes.

    Science.gov (United States)

    Kokhan, Oleksandr; Shinkarev, Vladimir P

    2011-02-02

    Antimycin A is the most frequently used specific and powerful inhibitor of the mitochondrial respiratory chain. We used all-atom molecular dynamics (MD) simulations to study the dynamic aspects of the interaction of antimycin A with the Q(i) site of the bacterial and bovine bc(1) complexes embedded in a membrane. The MD simulations revealed considerable conformational flexibility of antimycin and significant mobility of antimycin, as a whole, inside the Q(i) pocket. We conclude that many of the differences in antimycin binding observed in high-resolution x-ray structures may have a dynamic origin and result from fluctuations of protein and antimycin between multiple conformational states of similar energy separated by low activation barriers, as well as from the mobility of antimycin within the Q(i) pocket. The MD simulations also revealed a significant difference in interaction between antimycin and conserved amino acid residues in bovine and bacterial bc(1) complexes. The strong hydrogen bond between antimycin and conserved Asp-228 (bovine numeration) was observed to be frequently broken in the bacterial bc(1) complex and only rarely in the bovine bc(1) complex. In addition, the distances between antimycin and conserved His-201 and Lys-227 were consistently larger in the bacterial bc(1) complex. The observed differences could be responsible for a weaker interaction of antimycin with the bacterial bc(1) complex.

  16. The conservative characteristic FD methods for atmospheric aerosol transport problems

    Science.gov (United States)

    Fu, Kai; Liang, Dong

    2016-01-01

    In the paper, we develop the new conservative characteristic finite difference methods (C-CFD) for the atmospheric aerosol transport problems. We propose the time second-order and spatial high-order conservative characteristic finite difference methods for the aerosol vertical advection-diffusion process and the two-dimensional conservative characteristic finite difference methods for aerosol horizontal transport process in the second-order splitting algorithm. Based on the characteristic form of advection-diffusion equations tracking back along the characteristic curve, we treat the integrals over the tracking cells at the previous time level by the conservative interpolations and propose to treat the diffusion terms by the average along the characteristics, where the high-order discrete fluxes are obtained by approximating the cumulative mass function and are continuous at the tracking points. The important feature is that the proposed C-CFD schemes preserve mass and have second-order accuracy in time and high-order accuracy in space. Numerical tests are taken to show the accuracy in time and space and mass conservation of our C-CFD schemes, compared with the standard CFD method. A real case of air quality modelling during the 2008 Beijing Olympics and a severe haze in North China are further simulated and analyzed by using our C-CFD algorithm. Simulated results are in good agreement with observations. The developed C-CFD algorithm can be used for efficiently solving large scale atmospheric aerosol transport problems.

  17. An upwind super compact difference scheme for KdV-Burgers equation%一种求解 KdV-Burgers 方程的迎风超紧致差分格式

    Institute of Scientific and Technical Information of China (English)

    孙建安; 郭小霞; 贾伟

    2015-01-01

    In this paper , an upwind super compact difference scheme (USCD ) is proposed . The numerical characteristics of USCD are analyzed by using Fourier analysis , and compared with other upwind difference schemes and upwind compact difference schemes . According to analysis , it is found that USCD has better resolution and lower dissipation . Numerical solutions of the Burgers and KdV‐Burgers equations show that the USCD scheme has high‐order accuracy and is effective for long time evolution .%提出了一种迎风超紧致差分格式(USCD),利用Fourier分析方法对该格式的数值特性进行了分析,并与其他的迎风差分格式和迎风紧致差分格式做了对比。结果反映出USCD具有更好的分辨率和更低的耗散。通过对Burgers方程和KdV‐Burgers方程的数值模分析,进一步证实了USCD格式有更高的精度和对长时间演化问题的有效性。

  18. A new method for constructing total energy conservation algorithms

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Based on a basic rule for the research on numerical methods which requires that the properties of the original problem should be preserved as much as possible under discretization, a new method for constructing total energy conservation algorithms is presented. By this method, all kinds of implicit schemes with energy conservation laws including many classical conservation schemes can be constructed from a kind of special function. Also, the concrete criterion for judging total energy conservation schemes is given. Numerical tests show that these new schemes are effective.

  19. Ammonium transport proteins with changes in one of the conserved pore histidines have different performance in ammonia and methylamine conduction.

    Science.gov (United States)

    Wang, Jinan; Fulford, Tim; Shao, Qiang; Javelle, Arnaud; Yang, Huaiyu; Zhu, Weiliang; Merrick, Mike

    2013-01-01

    Two conserved histidine residues are located near the mid-point of the conduction channel of ammonium transport proteins. The role of these histidines in ammonia and methylamine transport was evaluated by using a combination of in vivo studies, molecular dynamics (MD) simulation, and potential of mean force (PMF) calculations. Our in vivo results showed that a single change of either of the conserved histidines to alanine leads to the failure to transport methylamine but still facilitates good growth on ammonia, whereas double histidine variants completely lose their ability to transport both methylamine and ammonia. Molecular dynamics simulations indicated the molecular basis of the in vivo observations. They clearly showed that a single histidine variant (H168A or H318A) of AmtB confines the rather hydrophobic methylamine more strongly than ammonia around the mutated sites, resulting in dysfunction in conducting the former but not the latter molecule. PMF calculations further revealed that the single histidine variants form a potential energy well of up to 6 kcal/mol for methylamine, impairing conduction of this substrate. Unlike the single histidine variants, the double histidine variant, H168A/H318A, of AmtB was found to lose its unidirectional property of transporting both ammonia and methylamine. This could be attributed to a greatly increased frequency of opening of the entrance gate formed by F215 and F107, in this variant compared to wild-type, with a resultant lowering of the energy barrier for substrate to return to the periplasm.

  20. QoS Analysis of the Integrated UMTS and WLAN Ad Hoc Network in different Security Schemes with Wormhole Attack under large Scalability for CBR Voice Interactive Traffic

    Directory of Open Access Journals (Sweden)

    Mr. Shashank Tripathi,

    2016-07-01

    Full Text Available The selection of security schemes against Wormhole Attack (WHA in next generation heterogeneous networks is based on major factors: authentication, confidentiality, and integrity and data availability. The effect of this active threat on Quality of Service (QoS of the Integrated Universal Mobile Telecommunications System (UMTS and Wireless Local Area Network (WLAN Ad Hoc network can be minimized by a suitable secure routing protocol. The aim of this work is to analyze QoS of the Integrated UMTS and WLAN network for Constant Bit-Rate (CBR voice messaging, interactive traffic under a secure distance vector routing protocol with various security schemes under WHA. This paper compares them on the basis of QoS metrics.

  1. Differences of Anxiety Levels between Students of Natural Sciences and Social Studies Major Based on School Environmental Factors in Senior High Schools with Rintisan Sekolah Bertaraf Internasional Scheme

    OpenAIRE

    Arviana Adamantina Putri; Leonardo Lubis; Tatang Muchtar Sutaryan

    2014-01-01

    Background: Senior High Schools with Rintisan Sekolah Bertaraf Internasional (RSBI) scheme are senior high schools that pilot international standards in learning methods and high curriculum targets. This factor may lead to a rise of anxiety amongst students, both for students in Natural Sciences major and Social Studies major. There are three factors which cause anxiety in the school environment, namely: dissatisfaction towards the curriculum, the teacher, and the school management. Metho...

  2. 不同微物理方案对一次梅雨锋暴雨过程模拟的影响%The effects of different microphysical schemes on the simulation of a meiyu front heavy rainfall

    Institute of Scientific and Technical Information of China (English)

    孙晶; 楼小凤; 史月琴

    2011-01-01

    The convective parameterization and microphysical scheme are two main approaches in a mesoscale atmospheric model to describing cloud and precipitation processes. When the grid scale of the model is small enough to distinguish the convective cloud scale, the microphysical scheme becomes more important. In this study, a case of heavy rainfall of Meiyu front happened on July 7-9, 2007 in China is simulated using the GRAPES mesoscale model. The effects of the different microphysical schemes (the Ncepcloud3 simple ice scheme, the Ncepcloud5 mixed phase scheme, the CAMS double moment mixed phase scheme) on heavy rainfall simulating are analyzed combining with the observations of precipitation, the radar echoes and hydro-meteors patterns. The results show that for this heavy rainfall case, the simulations using the CAMS scheme are better for the classes of light rain and moderate rain, and the Ncepcloud3 scheme and the Ncepcloud5 scheme are of higher TS for the torrential rain and the class above it. The maximum of the heavy rainfall center simulated using the CAMS scheme is close to the observation. The simulated results of mesoscale convective system developing processes are different using these schemes from each other. The area of weak convective echoes simulated by the Ncepcloud5 scheme is small. The CAMS scheme simulated a bigger area of weak convective echo which is basically consistent with observations. The vertical distributions of the mass content and number concentration of ice particles calculated by the CAMS dual parameters scheme are similar to the CloudSat observations. The ice particles calculated by the Ncepcloud3 scheme and Ncepcloud5 scheme are larger than the observation with no number concentration of theirs covered. The reasons of the simulative difference caused by using different schemes are preliminarily analyzed. During the forming stage of convective system, the simulative difference is mainly produced by dynamical process. While during both

  3. Linearization of conservative nonlinear oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Belendez, A; Alvarez, M L [Departamento de Fisica, IngenierIa de Sistemas y TeorIa de la Senal, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain); Fernandez, E; Pascual, I [Departamento de Optica, FarmacologIa y AnatomIa, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain)], E-mail: a.belendez@ua.es

    2009-03-11

    A linearization method of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force which allows us to obtain a frequency-amplitude relation which is valid not only for small but also for large amplitudes and, sometimes, for the complete range of oscillation amplitudes. Some conservative nonlinear oscillators are analysed to illustrate the usefulness and effectiveness of the technique.

  4. A Novel Iris Segmentation Scheme

    Directory of Open Access Journals (Sweden)

    Chen-Chung Liu

    2014-01-01

    Full Text Available One of the key steps in the iris recognition system is the accurate iris segmentation from its surrounding noises including pupil, sclera, eyelashes, and eyebrows of a captured eye-image. This paper presents a novel iris segmentation scheme which utilizes the orientation matching transform to outline the outer and inner iris boundaries initially. It then employs Delogne-Kåsa circle fitting (instead of the traditional Hough transform to further eliminate the outlier points to extract a more precise iris area from an eye-image. In the extracted iris region, the proposed scheme further utilizes the differences in the intensity and positional characteristics of the iris, eyelid, and eyelashes to detect and delete these noises. The scheme is then applied on iris image database, UBIRIS.v1. The experimental results show that the presented scheme provides a more effective and efficient iris segmentation than other conventional methods.

  5. High-order WENO scheme for polymerization-type equations*

    Directory of Open Access Journals (Sweden)

    Gabriel Pierre

    2010-12-01

    Full Text Available Polymerization of proteins is a biochemical process involved in different diseases. Mathematically, it is generally modeled by aggregation-fragmentation-type equations. In this paper we consider a general polymerization model and propose a high-order numerical scheme to investigate the behavior of the solution. An important property of the equation is the mass conservation. The WENO scheme is built to preserve the total mass of proteins along time. Le processus biophysique de polymérisation de protéines entre en jeu dans différentes maladies. Mathématiquement, ceci est généralement modélisé par des équations de type agrégation-fragmentation. Dans cet article nous considérons un modèle général de polymérisation et proposons un schéma d’ordre élevé pour sa résolution numérique. Une propriété importante de l’équation est la conservation de la masse. Le schéma WENO est construit pour conserver la masse totale de protéines au cours du temps.

  6. A cell-centered lagrangian scheme in two-dimensional cylindrical geometry

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A new Lagrangian cell-centered scheme for two-dimensional compressible flows in planar geometry is proposed by Maire et al.The main new feature of the algorithm is that the vertex velocities and the numerical fluxes through the cell interfaces are all evaluated in a coherent manner contrary to standard approaches.In this paper the method introduced by Maire et al.is extended for the equations of Lagrangian gas dynamics in cylindrical symmetry.Two different schemes are proposed,whose difference is that one uses volume weighting and the other area weighting in the discretization of the momentum equation.In the both schemes the conservation of total energy is ensured,and the nodal solver is adopted which has the same formulation as that in Cartesian coordinates.The volume weighting scheme preserves the momentum conservation and the area-weighting scheme preserves spherical symmetry.The numerical examples demonstrate our theoretical considerations and the robustness of the new method.

  7. High Order Three Part Split Symplectic Integration Schemes

    CERN Document Server

    Gerlach, Enrico; Skokos, Charalampos; Bodyfelt, Joshua D; Papamikos, Georgios

    2013-01-01

    Symplectic integration methods based on operator splitting are well established in many branches of science. For Hamiltonian systems which split in more than two parts, symplectic methods of higher order have been studied in detail only for a few special cases. In this work, we present and compare different ways to construct high order symplectic schemes for general Hamiltonian systems that can be split in three integrable parts. We use these techniques to numerically solve the equations of motion for a simple toy model, as well as the disordered discrete nonlinear Schr\\"odinger equation. We thereby compare the efficiency of symplectic and non-symplectic integration methods. Our results show that the new symplectic schemes are superior to the other tested methods, with respect to both long term energy conservation and computational time requirements.

  8. Longevity of Juniperus procera seed lots under different storage conditions: implications for ex situ conservation in seed banks

    Institute of Scientific and Technical Information of China (English)

    Negash Mamo; Diriba Nigusie; Mulualem Tigabu; Demel Teketay; Miftah Fekadu

    2011-01-01

    Juniperus procera Endl. Is economically important timberspecies, but its populations are extremely small and fragmented in itsnatural habitat, thus, calling for immediate ex situ conservation. Here weexamined the effects of seed sources and storage temperature on thelongevity of Juniperus procera seed lots through collection and preserva-tion of seeds in seed banks. Seeds were collected from nine sites acrossthe species natural distribution in Ethiopia and stored in four warehouses:modern cold room (5℃), mud house (15℃), concrete block house (17℃)or corrugated iron house (20℃) for 42 months. Every three months, arandom sample of stored seeds were drawn and tested for germination. Ahighly significant variation (p 0.80; p<0.01). Cold storage also resulted in enhancement ofgermination through its stratification effect that terminated the non-deepphysiological dormancy of juniper seeds. In conclusion, seed lots withgood initial germination can be effectively stored in cold room (5℃) upto four years. In the absence of modern cold stores, mud houses can beused as a good altemative to store seeds at local level.

  9. Cryptanalysis and Improvement of Piveteau Signature Scheme with Message Recovery

    Institute of Scientific and Technical Information of China (English)

    李子臣; 成军祥; 戴一奇

    2003-01-01

    Piveteau signature scheme allows message recovery but the methodology differs from that of the Nyberg-Rueppel schemes. This paper analyzes the security of the Piveteau scheme by designing some attacks. Two improved methods to Piveteau signature scheme and Nyberg-Rueppel schemes were developed to avoid these weaknesses. Analyses of the security of the improved schemes prove that the improved methods can effectively handle the attacks proposed in this paper.

  10. High-Order Energy Stable WENO Schemes

    Science.gov (United States)

    Yamaleev, Nail K.; Carpenter, Mark H.

    2008-01-01

    A new third-order Energy Stable Weighted Essentially NonOscillatory (ESWENO) finite difference scheme for scalar and vector linear hyperbolic equations with piecewise continuous initial conditions is developed. The new scheme is proven to be stable in the energy norm for both continuous and discontinuous solutions. In contrast to the existing high-resolution shock-capturing schemes, no assumption that the reconstruction should be total variation bounded (TVB) is explicitly required to prove stability of the new scheme. A rigorous truncation error analysis is presented showing that the accuracy of the 3rd-order ESWENO scheme is drastically improved if the tuning parameters of the weight functions satisfy certain criteria. Numerical results show that the new ESWENO scheme is stable and significantly outperforms the conventional third-order WENO finite difference scheme of Jiang and Shu in terms of accuracy, while providing essentially nonoscillatory solutions near strong discontinuities.

  11. Generalized Group Signature Scheme

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The concept of generalized group signature scheme will bepresent. Based on the generalized secret sharing scheme proposed by Lin and Ha rn, a non-interactive approach is designed for realizing such generalized group signature scheme. Using the new scheme, the authorized subsets of the group in w hich the group member can cooperate to produce the valid signature for any messa ge can be randomly specified

  12. MIDI Programming in Scheme

    DEFF Research Database (Denmark)

    Nørmark, Kurt

    2010-01-01

    A Scheme representation of Standard MIDI Files is proposed. The Scheme expressions are defined and constrained by an XML-language, which in the starting point is inspired by a MIDI XML event language made by the MIDI Manufactures Association. The representation of Standard MIDI Files in Scheme ma...

  13. MIDI Programming in Scheme

    DEFF Research Database (Denmark)

    Nørmark, Kurt

    2010-01-01

    A Scheme representation of Standard MIDI Files is proposed. The Scheme expressions are defined and constrained by an XML-language, which in the starting point is inspired by a MIDI XML event language made by the MIDI Manufactures Association. The representation of Standard MIDI Files in Scheme ma...

  14. Entropy Stable Numerical Schemes for Two-Fluid Plasma Equations

    CERN Document Server

    Kumar, Harish

    2011-01-01

    Two-fluid ideal plasma equations are a generalized form of the ideal MHD equations in which electrons and ions are considered as separate species. The design of efficient numerical schemes for the these equations is complicated on account of their non-linear nature and the presence of stiff source terms, especially for high charge to mass ratios and for low Larmor radii. In this article, we design entropy stable finite difference schemes for the two-fluid equations by combining entropy conservative fluxes and suitable numerical diffusion operators. Furthermore, to overcome the time step restrictions imposed by the stiff source terms, we devise time-stepping routines based on implicit-explicit (IMEX)-Runge Kutta (RK) schemes. The special structure of the two-fluid plasma equations is exploited by us to design IMEX schemes in which only local (in each cell) linear equations need to be solved at each time step. Benchmark numerical experiments are presented to illustrate the robustness and accuracy of these schem...

  15. A benchmark study of numerical schemes for one-dimensional arterial blood flow modelling.

    Science.gov (United States)

    Boileau, Etienne; Nithiarasu, Perumal; Blanco, Pablo J; Müller, Lucas O; Fossan, Fredrik Eikeland; Hellevik, Leif Rune; Donders, Wouter P; Huberts, Wouter; Willemet, Marie; Alastruey, Jordi

    2015-10-01

    Haemodynamical simulations using one-dimensional (1D) computational models exhibit many of the features of the systemic circulation under normal and diseased conditions. Recent interest in verifying 1D numerical schemes has led to the development of alternative experimental setups and the use of three-dimensional numerical models to acquire data not easily measured in vivo. In most studies to date, only one particular 1D scheme is tested. In this paper, we present a systematic comparison of six commonly used numerical schemes for 1D blood flow modelling: discontinuous Galerkin, locally conservative Galerkin, Galerkin least-squares finite element method, finite volume method, finite difference MacCormack method and a simplified trapezium rule method. Comparisons are made in a series of six benchmark test cases with an increasing degree of complexity. The accuracy of the numerical schemes is assessed by comparison with theoretical results, three-dimensional numerical data in compatible domains with distensible walls or experimental data in a network of silicone tubes. Results show a good agreement among all numerical schemes and their ability to capture the main features of pressure, flow and area waveforms in large arteries. All the information used in this study, including the input data for all benchmark cases, experimental data where available and numerical solutions for each scheme, is made publicly available online, providing a comprehensive reference data set to support the development of 1D models and numerical schemes.

  16. 我国按比例安排残疾人就业地区差异及影响因素分析%Analysis on the Influence Factor and Regional Difference of Quota Scheme Employment of Disabled Person in China

    Institute of Scientific and Technical Information of China (English)

    尚珂; 梁土坤

    2013-01-01

    Quota scheme employment of disabled person is the effective way to promote the employment of persons with disabili⁃ties in modern society.This paper used the method of cluster analysis to analyze the influence factor of quota scheme employ⁃ment of disabled persons in China.It found out that the 31 provinces and cities in China can be divided into three categories which had significant differences.And GDP,policy differences and different levels of education of disabled people were the main factors that influence the regional difference of quota scheme employment.%  按比例安排残疾人就业,是现代社会促进残疾人就业的有效途径。文章利用聚类分析方法对我国按比例安排残疾人就业的地区差异进行了深入分析,发现可将我国内地31个省市分为三大类,各类之间存在显著差异。而地区生产总值、按比例安排残疾人就业政策差异以及地区间的残疾人受教育水平不同是影响按比例安排残疾人就业地区差异的重要因素。

  17. Conservative management.

    Science.gov (United States)

    Kruis, W; Leifeld, L; Pfützer, R

    2012-01-01

    Treatment of diverticulitis comprises at least two options: conservative or surgical management. There is a recent trend to limit surgical treatment of acute diverticulitis and to favor conservative management. This review addresses general aspects of conservative patient care with special focus on the treatment of patients with a first attack of diverticulitis. The presentation does not include a discussion of specific drugs which is given in other sections of this issue.

  18. High-order Finite Difference Solution of Euler Equations for Nonlinear Water Waves

    DEFF Research Database (Denmark)

    Christiansen, Torben Robert Bilgrav; Bingham, Harry B.; Engsig-Karup, Allan Peter

    2012-01-01

    is discretized using arbitrary-order finite difference schemes on a staggered grid with one optional stretching in each coordinate direction. The momentum equations and kinematic free surface condition are integrated in time using the classic fourth-order Runge-Kutta scheme. Mass conservation is satisfied...

  19. Introducing Conservation of Momentum

    Science.gov (United States)

    Brunt, Marjorie; Brunt, Geoff

    2013-01-01

    The teaching of the principle of conservation of linear momentum is considered (ages 15 + ). From the principle, the momenta of two masses in an isolated system are considered. Sketch graphs of the momenta make Newton's laws appear obvious. Examples using different collision conditions are considered. Conservation of momentum is considered…

  20. Cubication of Conservative Nonlinear Oscillators

    Science.gov (United States)

    Belendez, Augusto; Alvarez, Mariela L.; Fernandez, Elena; Pascual, Immaculada

    2009-01-01

    A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear…