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This paper deals with the discrete maximum principle and energy stability of a new difference scheme for solving Allen-Cahn equations. By combining the second-order central difference approximation in space and the Crank-Nicolson method with Newton linearized technique in time, a two-level linearized difference scheme for Allen-Cahn equations is derived, which can yield accuracy of order two both in time and space. Under appropriate conditions, the scheme is proved to be uniquely solvable and able to preserve the maximum principle and energy stability of the equations in the discrete sense. With some numerical experiments, the theoretical results and computational effectiveness of the scheme are further illustrated.

In this work, we develop a new linear, decoupled numerical scheme for the typical phase-field surfactant model. An improved scalar auxiliary variable (SAV) approach is used to discretize the governing equations in time. Different from the classical SAV approach, this improved form can calculate the phase field function ϕ, surfactant function ψ, and auxiliary variables in a step-by-step manner, i.e., the auxiliary variables are treated totally explicitly, thus we can directly calculate ϕ and ψ instead of computing the inner products. At each time step, the surfactant ψ can be directly obtained by an explicit way, then ϕ is updated by solving a linear system with constant coefficient. Therefore, the implementation of this improved SAV approach is easier than the classical SAV approach. The energy stability in first-order case can be analytically proved by using the our method. The numerical experiments show that our proposed method not only achieves desired first- and second-order accuracy but also satisfies the desired discrete energy dissipation law even if some larger time steps are used. Furthermore, the coarsening dynamics with different average concentrations can be well simulated by using our method. The co-continuous and drop patterns are generated in the even compositions case and uneven compositions case, respectively.

We are concerned with asymptotic behaviours of solutions for linear wave equations with frictional damping only on Wentzell boundary, but without any interior damping. Making some elaborate and subtle analysis of an associated auxiliary system, we obtain an ideal estimate of the resolvent of the generator of the system along the imaginary axis. This enables us to prove that the energies of the system decay polynomially. Our energy stability result presents a solution, in the linear case, to the problem proposed by Cavalcanti et al. (2007) [8] , which was put forward as a “hard problem” due to the lack of interior damping.

In this paper, a number of energy stable numerical schemes are proposed for the fractional Cahn–Hilliard equation. We prove mass conservation, unique solvability and energy stability for three time semi-discretized schemes based on the first-order semi-implicit scheme, the Crank–Nicolson scheme and the BDF2 scheme respectively. Then we present error analysis for these numerical schemes with the Fourier spectral approximation in space. Some numerical experiments are finally carried out to confirm accuracy and effectiveness of these proposed methods.

In this paper, we consider numerical approximations to solving the Cahn-Hilliard phase field model for diblock copolymers. We combine the recently developed SAV (scalar auxiliary variable) approach with the stabilization technique to arrive at a novel stabilized-SAV method, where a crucial linear stabilization term is added to enhancing the stability and keeping the required accuracy while using the large time steps. The scheme is very easy-to-implement and fast in the sense that one only needs to solve two decoupled fourth-order biharmonic equations with constant coefficients at each time step. We further prove the unconditional energy stability of the scheme rigorously. Through the comparisons with some other prevalent schemes like the fully-implicit, convex-splitting, and non-stabilized SAV scheme for some benchmark numerical examples in 2D and 3D, we demonstrate the stability and the accuracy of the developed scheme numerically.

Two novel and efficient modified techniques based on recently developed stabilized invariant energy quadratization (IEQ) approach to deal with nonlinear terms in gradient flows are proposed in this paper. We proved the unconditional energy stability for a class of gradient flows and their semi-discrete schemes carefully and rigorously. One of the contributions for this approach is that we succeeded in finding suitable positive preserving functions in square root and do not need to add a positive constant which cannot be fixed before computing. Secondly, all nonlinear terms can be treated semi-explicitly, and one only needs to solve three decoupled linear equations with constant coefficients at each time step. Finally, several numerical simulations are demonstrated to verify the accuracy and efficiency of our proposed schemes.

In this paper, we propose stable second-order numerical schemes for the fractional Cahn–Hilliard and Allen–Cahn equations, which are based on the convex splitting in time and the Fourier spectral method in space. It is shown that the scheme for the fractional Cahn–Hilliard equation preserves mass. Meanwhile, the unique solvability and energy stability of the numerical schemes for the fractional Cahn–Hilliard and Allen–Cahn equations are proved. Finally, we present some numerical experiments to confirm the accuracy and the effectiveness of the proposed methods.

We consider numerical approximations for a phase-field dendritic crystal growth model, which is a highly nonlinear system that couples the anisotropic Allen–Cahn type equation and the heat equation. By combining the stabilized-Invariant Energy Quadratization method with a novel decoupling technique, the scheme requires solving only a sequence of linear elliptic equations at each time step, making it the first, to the best of the author’s knowledge, totally decoupled, linear, unconditionally energy stable scheme for the model. We further prove the unconditional energy stability rigorously and present various numerical simulations to demonstrate the stability and accuracy.

In this paper, we consider numerical approximations for the anisotropic Cahn–Hilliard equation. We develop two linear and second-order schemes that combine the IEQ approach with the stabilization technique, where several extra linear stabilization terms are added in and they can be shown to be crucial to suppress the non-physical spatial oscillations caused by the strong anisotropy. We show the well-posedness of the resulting linear systems and further prove their corresponding unconditional energy stabilities rigorously. Various 2D and 3D numerical simulations are presented to demonstrate the stability, accuracy, and efficiency of the proposed schemes.

A comparative study of structural, electronic and magnetic Ca2+, Sr2+ and Ba2+ A-site ion substitution of BiFeO3 with different Fe oxidation states was carried out. Calculation shows doped compounds favours energy stability in Fe oxidation states of 2+ and 4+ compared to 3+ charge. Electronic band gap makes significant changes with value of 1.32 eV, 1.36 eV and 1.31 eV for Ca, Sr and Ba doped respectively, compared to pure BiFeO3 of 1.41 eV. The net magnetization shows improvement with use of the dopant elements compared to pure BiFeO3. These changes indicate the role of the heterovalent dopant in BiFeO3.

The variable time-stepping technique is powerful in capturing the multi-scale behaviors (e.g., the solution changes rapidly in certain regions of time) for the Allen–Cahn equation. Based on the scalar auxiliary variable (SAV) approach and the Crank–Nicolson schemes, we establish the unconditional energy stability and error estimates rigorously for the Allen–Cahn equation on variable grids. A numerical experiment is performed to verify the theoretical results. To the best of our knowledge, this is the first topic on the convergence analysis for the SAV schemes on variable grids.

We propose a second-order accurate energy-stable time-integration method that controls the evolution of numerical instabilities introducing numerical dissipation in the highest-resolved frequencies. Our algorithm further extends the generalized- α method and provides control over dissipation via the spectral radius. We derive the first and second laws of thermodynamics for the Swift–Hohenberg equation and provide a detailed proof of the unconditional energy stability of our algorithm. Finally, we present numerical results to verify the energy stability and its second-order accuracy in time.

Microgrids have become increasingly popular in the United States. Supported by favorable federal and local policies, microgrid projects can provide greater energy stability and resilience within a project site or community. This paper reviews major federal, state, and utility-level policies driving microgrid development in the United States. Representative U.S. demonstration projects are selected and their technical characteristics and non-technical features are introduced. The paper discusses trends in the technology development of microgrid systems as well as microgrid control methods and interactions within the electricity market. Software tools for microgrid design, planning, and performance analysis are illustrated with each tool’s core capability. Finally, the paper summarizes the successes and lessons learned during the recent expansion of the U.S. microgrid industry that may serve as a reference for other countries developing their own microgrid industries.

In this paper we propose a new high order accurate space–time discontinuous Galerkin (DG) finite element scheme for the solution of the linear elastic wave equations in first order velocity-stress formulation in two and three-space dimensions on staggered unstructured triangular and tetrahedral meshes. The method reaches arbitrary high order of accuracy in both space and time via the use of space–time basis and test functions. Within the staggered mesh formulation, we define the discrete velocity field in the control volumes of a primary mesh, while the discrete stress tensor is defined on a face-based staggered dual mesh. The space–time DG formulation leads to an implicit scheme that requires the solution of a linear system for the unknown degrees of freedom at the new time level. The number of unknowns is reduced at the aid of the Schur complement, so that in the end only a linear system for the degrees of freedom of the velocity field needs to be solved, rather than a system that involves both stress and velocity. Thanks to the use of a spatially staggered mesh, the stencil of the final velocity system involves only the element and its direct neighbors and the linear system can be efficiently solved via matrix-free iterative methods. Despite the necessity to solve a linear system, the numerical scheme is still computationally efficient. The chosen discretization and the linear nature of the governing PDE system lead to an unconditionally stable scheme, which allows large time steps even for low quality meshes that contain so-called sliver elements. The fully discrete staggered space–time DG method is proven to be energy stable for any order of accuracy, for any mesh and for any time step size. For the particular case of a simple Crank–Nicolson time discretization and homogeneous material, the final velocity system can be proven to be symmetric and positive definite and in this case the scheme is also exactly energy preserving. The new scheme is applied to several test problems in two and three space dimensions, providing also a comparison with high order explicit ADER-DG schemes.

An Yb:YAG dual-crystal regenerative amplifier was developed. The thermal effects were largely decreased by the dual-crystal configuration and optimized cavity design. The chirped pulse was amplified to 3.5 mJ with excellent energy stability (root mean square ∼ 0.95%) and beam quality (M2

We focus on a reduced-order finite element (FE) method for the Allen-Cahn equation. Toward this end, we first derive a traditional FE (TFE) formulation for the Allen-Cahn equation and the energy stability and error estimates of the TFE solutions. Then we use the proper orthogonal decomposition (POD) technique to generate a set of POD bases from a few TFE solutions, establish a novel reduced-order FE (ROFE) formulation for the Allen-Cahn equation by the set of POD bases, and discuss the energy stability and error estimates of the ROFE solutions. Finally, we provide some numerical experiments to confirm the validity of the novel ROFE formulation.

In this paper, we present the Convex Splitting RungeKutta (CSRK) methods which provide a simple unified framework to solve phase-field models such as the AllenCahn, CahnHilliard, and phase-field crystal equations. The core idea of the CSRK methods is the combination of convex splitting methods and multi-stage implicitexplicit RungeKutta methods. Our CSRK methods are high-order accurate in time and we investigate the energy stability numerically. We present numerical experiments to show the accuracy and efficiency of the proposed methods up to the third-order accuracy.

In this paper, we consider the numerical solution of a binary fluid–surfactant phase field model, in which the free energy contains a nonlinear coupling entropy, a Ginzburg–Landau double well potential, and a logarithmic Flory–Huggins potential. The resulting system consists of two nonlinearly coupled Cahn–Hilliard type equations. We develop a first and a second order time stepping schemes for this system using the “Invariant Energy Quadratization” approach; in particular, the system is transformed into an equivalent one by introducing appropriate auxiliary variables and all nonlinear terms are then treated semi-explicitly. Both schemes are linear and lead to symmetric positive definite systems in space at each time step, thus they can be efficiently solved. We further prove that these schemes are unconditionally energy stable in the discrete sense. Various 2D and 3D numerical experiments are performed to validate the accuracy and energy stability of the proposed schemes.

The reaction paths of hydrogen generation from water molecule with Pt7 cluster are presented, based on the density functional theory with the generalized gradient approximation. The 12 stable complex structures of the H2O@Pt7 reactants and the corresponding structures of the H2 + O@Pt7 and H + HO@Pt7 products are optimized for various adsorption sites on the cluster. The frequency analysis has been used to confirm the energy stability of the structures. The geometries of the transition states and the intrinsic reaction coordinates are calculated at the same theoretical level. The energy barrier for each reaction is determined. The results demonstrated that Pt7 cluster can abstract H or H2 from H2O molecule depend on the initial structures of reactant and the active energy. These results are helpful for designing the practical hydrogen generation scheme with these reactions.

Mixed surimi gels with 5 and 8% of pea flour (PF) and 1.41% of pea protein isolate (PPI) were made to replace part of the myofibrillar proteins with legume compounds. Viscoelastic properties in the linear viscoelastic range of fresh mixed gels and control surimi gel were compared with frozen-stored gels for one year. Fresh PPI-surimi gels were more flexible (higher γmax), with greater energy stability (higher E parameter) and gel strength (higher G′ and G″ moduli) than the control gel. These gel properties were sustained after one year of frozen storage. Fresh mixed PF-surimi gels at 5% and 8% PF concentration were less flexible with lower network-energy, less solid-like character (higher tanδ) and higher gel strength, particularly at 8% PF as compared to the control gel. Frozen storage of PF-surimi gels slightly reduced γmax, E, tanδ and percentage of elasticity. Surprisingly, in the control surimi gel, frozen storage improved the energy stability, conformational flexibility, maintaining similar values of gel strength and mechanical elasticity to fresh gel., This work was supported by the Spanish. Ministry of Economy and Competitiveness (RTA 2015-00003-CO2).

The numerical approximations for the coupled Cahn–Hilliard system describing the phase separation of the copolymer and homopolymer mixtures are considered in this paper. To develop easy to implement time marching schemes with unconditional energy stabilities, we use the Scalar Auxiliary Variable (SAV) approach for achieving two efficient, decoupled, and linear numerical schemes, where a new scalar auxiliary variable is introduced to reformulate the model. The schemes lead to decoupled linear equations with constant coefficients at each time step, and their unique solvability and unconditional energy stabilities are proved rigorously. Numerical examples are performed to demonstrate the accuracy and energy stability of the proposed schemes, and numerous benchmark simulations are also presented to show a variety of morphologies of pattern formations of the copolymer and homopolymer mixtures.

In this paper, we consider numerical approximations for the anisotropic phase-field crystal model. The model is a sixth-order nonlinear equation with an anisotropic Laplace operator. To develop easy-to-implement and unconditionally energy stable time marching schemes, we combine the scalar auxiliary variable (SAV) approach with the stabilization method, where two extra stabilization terms are added to enhance the stability and keep the required accuracy while using large time steps. By using the first-order backward Euler and second-order backward differentiation formula, we obtain two highly efficient and linear numerical schemes and prove their unconditional energy stabilities rigorously. We demonstrate the accuracy, stability, and efficiency of the developed schemes through numerous benchmark numerical experiments.

In this paper, we develop a series of efficient numerical schemes to solve the phase field model for homopolymer blends. The governing system is derived from the energetic variational approach of a total free energy, that consists of a nonlinear logarithmic Flory–Huggins potential, and a gradient entropy with a concentration-dependent de-Gennes type coefficient. The main challenging issue to solve this kind of models numerically is about the time marching problem, i.e., how to develop suitable temporal discretizations for the nonlinear terms in order to preserve the energy stability at the discrete level. We solve this issue in this paper, by developing the first and second order temporal approximation schemes based on the “Invariant Energy Quadratization” method, where all nonlinear terms are treated semi-explicitly. Consequently, the resulting numerical schemes lead to a symmetric positive definite linear system to be solved at each time step. The unconditional energy stabilities are further proved. Various numerical simulations of 2D and 3D are presented to demonstrate the stability and the accuracy of the proposed schemes.

We focus on proposing and analyzing a reduced-order finite difference (ROFD) iterative scheme based on a proper orthogonal decomposition (POD) technique for Allen-Cahn equations with a small perturbation parameter and strong nonlinearity. We prove the discrete maximum-principle (DMP) preserving and discrete energy-stability (DES) preserving of the ROFD iterative solutions under a reasonable restriction on the time step size. We also analyze the convergence of the ROFD iterative solutions for Allen-Cahn equations. Numerical tests are presented to verify our proposed ROFD method, such as error estimates, convergence rates, DMP-preserving and DES-preserving. Moreover, it is shown that the computing time of ROFD iterative schemes with very few unknowns is much less than that of usual finite difference (FD) iterative schemes.

In this paper, we develop an unconditionally energy stable, second-order accurate time marching scheme for solving a penalized Allen–Cahn type Ohta–Kawasaki phase-field model for diblock copolymers, where the total free energy of the system consists of the double-well potential, the nonlocal Ohta–Kawasaki free energy functional, and a penalization potential to enforce the conservation of the modified volume approximately. The developed scheme combines the SAV (scalar auxiliary variable) approach with the stabilization technique, where a crucial linear stabilization term is added to enhance the stability while using the large time steps. The scheme is very easy-to-implement and one only needs to solve two decoupled elliptic equations with constant coefficients at each time step. We further prove the unconditional energy stability of the scheme rigorously and demonstrate the stability and the accuracy of the developed scheme numerically through simulating numerous numerical examples in 2D and 3D.

This paper is concerned with the stability and error estimates of the local discontinuous Galerkin (LDG) method coupled with semi-implicit spectral deferred correction (SDC) time-marching up to third order accuracy for the Allen–Cahn equation. Since the SDC method is based on the first order convex splitting scheme, the implicit treatment of the nonlinear item results in a nonlinear system of equations at each step, which increases the difficulty of the theoretical analysis. For the LDG discretizations coupled with the second and third order SDC methods, we prove the unique solvability of the numerical solutions through the standard fixed point argument in finite dimensional spaces. At the same time, the iteration and integral involved in the semi-implicit SDC scheme also increase the difficulty of the theoretical analysis. Comparing to the Runge–Kutta type semi-implicit schemes which exclude the left-most endpoint, the SDC scheme in this paper includes the left-most endpoint as a quadrature node. This makes the test functions of the SDC scheme more complicated and the energy equations are more difficult to construct. We provide two different ideas to overcome the difficulty of the nonlinear terms. By choosing the test functions carefully, the energy stability and error estimates are obtained in the sense that the time step Δ t only requires a positive upper bound and is independent of the mesh size h . Numerical examples are presented to illustrate our theoretical results.

In this paper, we expand the classical phase-field model for diblock copolymers (BCPs) to the magnetic-coupled case, where the free energy of the system is modeled as the combination of the nonlocal Ohta-Kawasaki free energy and the classical Ginzburg-Landau formalism for ferromagnetic ordering. To solve the model, we develop an efficient, second-order time marching scheme by adopting the recently developed stabilized-SAV (Scalar Auxiliary Variable) approach. The energy stability of the scheme is proved and several numerical examples are presented to show that the morphology patterns are strongly influenced by the magnetic field.

A class of bound preserving and energy dissipative schemes for the porous medium equation are constructed in this paper. The schemes are based on a positivity preserving approach for Wasserstein gradient flow and a perturbation technique, and are shown to be uniquely solvable, bound preserving, and in the first-order case, also energy dissipative. Ample numerical results are presented to validate the theoretical results and demonstrate the effectiveness of the new schemes.

This paper aims to present a new second-order maximum-principle preserving finite difference scheme for Allen–Cahn equations with periodic boundary conditions. The discrete maximum principle, the maximum-norm error estimate and the discrete energy stability of the proposed scheme are discussed. It is shown that the proposed scheme is unconditionally energy-stable by choosing proper parameters. A numerical experiment is performed to verify the theoretical results.

The Flux Reconstruction (FR) approach offers an efficient route to achieving high-order accuracy on unstructured grids. Additionally, FR offers a flexible framework for defining a range of numerical schemes in terms of so-called FR correction functions. Recently, a one-parameter family of FR correction functions were identified that lead to stable schemes for 1D linear advection problems. In this study we develop a procedure for identifying an extended range of stable, symmetric, and conservative FR correction functions. The procedure is applied to identify ranges of such correction functions for various orders of accuracy. Numerical experiments are undertaken, and the results found to be in agreement with the theoretical findings.

From density-function theory calculation, the structural, electronic and magnetic properties of χ -carbides (Fe,Cr) 5 C 2 are investigated. With the increase of Cr content in χ -carbides (Fe,Cr) 5 C 2 , the formation energy of χ carbide gradually decrease and energy stability of them increase. The formation energy of Cr 5 C 2 is −0.354 eV/f.u, and the stability of Cr 5 C 2 is higher than other χ carbides (Fe,Cr) 5 C 2 , Mn 5 C 2 and Fe 5 C 2 . There exists charges transfer from metal cation (Fe/Cr) to C atoms in χ -carbides, and this reveals an ionic contribution to the bonds. The addition of Cr decreases the magnetic moments of χ carbide, and the magnetic moments (Ms) of Cr 2 Cr 2 FeC 2 and Cr 5 C 2 are 0 μ B /f.u., while it expresses opposite magnetic characters of the same atom at different sites in the other χ type (Fe,Cr) 5 C 2 carbides. The 3d states of metal atoms in the majority states (up) move to above the Femi level and some metal atoms (Fe/Cr) in χ type (Fe,Cr) 5 C 2 are undergone the anti-ferromagnetic transformation.

Thermosolutal convection with reaction in a porous media of Darcy type is studied using the energy method. The effect of the reaction terms on the temperature and salt Rayleigh numbers are presented graphically. Furthermore, nonlinear energy stability boundaries for different values of the reaction terms are compared with the linear instability boundaries obtained by Pritchard and Richardson (2007).

The brain has a central role in the regulation of energy stability of the organism. It is the organ with the highest energetic demands, the most susceptible to energy deficits, and is responsible for coordinating behavioral and physiological responses related to food foraging and intake. Dietary interventions have been shown to be a very effective means to extend lifespan and delay the appearance of age-related pathological conditions, notably those associated with brain functional decline. The present review focuses on the effects of these interventions on brain metabolism and cerebral redox state, and summarizes the current literature dealing with dietary interventions on brain pathology.

Atomic and electronic structures for a number of GaAs(001) surface geometries were studied within the density functional theory (DFT) in order to re-examine the energy stability of surface reconstructions in the Ga-rich limit. The (2 × 4) mixed-dimer model developed for InP(001)-(2 × 4) surface was adopted for Ga-rich GaAs(001)-(2 × 4) surface. It is shown that the energetically favored Ga-rich (2 × 4) reconstructions are stabilized by dimerized Ga and As atoms. Our DFT calculations predict the coexistence of (2 × 4) and (4 × 4) reconstructions on GaAs(001) in the Ga-rich limit.

Background: Nitric oxide synthase inducible (iNOS) inhibits the proliferation of T-lympho-cytes and its role has been associated in disease such as cancer. Various studies have alsofound out the expression and the activity of iNOS in cancer. Thus requiring attention fornovel inhibitors against this enzyme.Methods: In the present study, the three-dimensional structure of iNOS of Gallus gallus wasgenerated by homology modelling using Modeller 9v8. The generated model was accessedfor geometrical errors and energy stability check. Further, a molecular docking analysiswas carried out against quercetin and its analogues and the docked analogues wereaccessed for ADMEetoxicity parameters.Results: The three-dimensional structure of iNOS of G. gallus was generated and theassessment analysis revealed the generated model is reliable. The molecular docking andADMEetoxicity analysis revealed three analogues have favourable interaction energy withenhanced pharmacological parameters than quercetin at the binding cavity of iNOSenzyme.Conclusion: The analogues of quercetin could be a lead molecule and supports for experi-mental testing as iNOS inhibitors in fighting against cancer.Copyright a 2013, JPR Solutions; Published by Reed Elsevier India Pvt. Ltd. All rightsreserved.

Scanning Tunneling Microscopy (STM) observations of the Si(111) 13 × 13 − R 13.9 ° -Co surface reconstruction show that two types of clusters coexist on the surface appearing as dark and bright on the images. The atomic structure of the dark ones has been recently proposed by L. Chaput et al. (L. Chaput, F. Dulot, M. C. Hanf, P. Wetzel, Surf. Sci. 604 (2010) 513) [ 34 ]. We found that each dark cluster consists of three Co atoms located on substitutional sites of the Si(111) surface with an overlying triangle of six Si adatoms. Here, we present the determination of the bright clusters atomic structure. Combining high-resolution filled and empty-state STM images and DFT simulations, we show that bright clusters consist of additional Si adatoms located on top of the six Si atoms terminating the dark clusters. These Si adatoms are in number of one, two or three. Energy stability of these three configurations and description of the electronic states are discussed in detail.

Density functional calculations are conducted to investigate the interlayer exchange coupling (IEC) between ferromagnetic Co slabs mediated by a CoSi spacer in Co/CoSi(001) multilayers with CsCl crystalline structure. For both sharp and mixed Co–Si interfaces we calculated the magnetic moment distribution and the energy stability for ferromagnetic (F) IEC and antiferromagnetic (AF) IEC between the Co slabs as function of the spacer thickness. We show that mixing near to the interface noticeably modifies the IEC to the extent that this can change from an oscillatory IEC as function of the spacer thickness to an exponentially decaying AF behavior.

In this paper, we show that regular solutions to the coupled nonlinear wave and Schrodinger systems with coercive polynomial nonlinearities are unique among distributional solutions enjoying the energy inequality. The arguments also yield the stabilities of classical solutions of the evolution systems in the energy norm.

Spanish Abstract: La estabilidad energetica de un pais es de suma importancia. A raiz de conflictos en paises de transito las politicas energeticas se dirigen cada vez mas a la autosuficiencia. En el siguiente trabajo se trataran las politicas energeticas de Alemania, Estados Unidos y Japon y el efecto del conflicto en Crimea en ellas.English Abstract: The energy stability from a country is of vital importance. Because of the conflicts in transit countries, the energy policies are now more devoted to autosufficiency. In this essay it will be discussed the energy policies from Germany, United States and Japan and the effect of the Crimea’s conflict on them.

This paper is a review of recent advances accomplished in the field of hydrotreatment (HDT) sulfide catalysts and using theoretical approaches based on the density functional theory (DFT) combined with thermodynamic models and microkinetic models. We illustrate first numerous concepts of modern DFT simulation for a better understanding of the industrial Co(Ni)MoS active phases: localization and role of the promoter, electronic properties and morphological changes induced by the reaction conditions or by promoter addition. Then, it is shown how support effects can be modeled by DFT to provide new insights on the local structure and energy stability of the active phase-support interface, where characterization techniques reach their limits. The comparison between γ-alumina and anatase-TiO2 supports is chosen as a relevant example. Finally, DFT simulations and microkinetic models help to rationalize “volcano-curve” type relationships between hydrodesulfurization (HDS) or hydrogenation (HYD) activities and the calculated sulfur–metal bond energy descriptor. This approach opens new routes to use systematic DFT simulations as a predictive tool. Perspectives for DFT simulations in the area of catalysis by sulfides are suggested.

We consider parabolic equations in two-dimensions with interfaces corresponding to concentrated heat capacity and singular own source. We give an analysis for energy stability of the solutions based on special Sobolev spaces (the energies also are given by the norms of these spaces) that are intrinsic to such problems. In order to define these spaces we study nonstandard spectral problems in which the eigenvalue appears in the interfaces (conjugation conditions) or at the boundary of the spatial domain. The introducing of appropriate spectral problems enable us to precise the values of the parameters which control the energy decay. In fact, in order for numerical calculation to be carried out effectively for large time, we need to know quantitatively this decay property.

We demonstrate a highly stable, diode-pumped regenerative amplifier for CPA laser systems that utilizes Nd:glass as the active medium. When end pumped with a 120-W quasi-cw (QCW) diode laser bar, a maximum pulse energy of 270 μJ has been achieved at an excellent pulse-to-pulse energy stability of 0.56% rms.

The fusion–evaporation reaction 10 B( 12 C, 2 n ) was used to make the first observation of in-beam γ decays from the astrophysically important nucleus 20 Na, lying adjacent to the proton drip-line. All states below the proton threshold in 20 Na were populated and identified in the experiment. These include new levels, previously unresolved levels, and states located with improved energy precision. The level structure of 20 Na, and its γ transitions, are compared to the mirror partner 20 F measured simultaneously in this experiment. In particular, a high degree of energy stability is found for all negative parity states. These results are discussed in the context of the nuclear shell model.

This paper studies the effect of energy market integration (EMI) on foreign direct investment (FDI). EMIs diminish energy uncertainty and price volatility in the host country and affect FDI through two channels: first, by harmonizing energy prices and, second, by reducing price dispersion. FDI may, as a result, increase both within and outside the EMI area, through energy stability mechanisms and price mechanisms, respectively. An empirical application on a global dataset including bilateral FDI data, during 2003-2012, using the gravity equation, shows that the integration of Portugal and Spain's electricity market in 2007 increased the amount of FDI's participants. Additionally, a positive increase in FDI from neighboring countries (in this instance, France), albeit lower in magnitude, is observed.

In this paper we analyze the numerical solution of problems in linear elastodynamics which combine finite elements in space and finite differences in time. After describing the continuum framework, we discuss the space-time discretization and we propose a convergence proof in the energy norm for the whole approximation. The modal analysis is used to provide a more convenient way to check for stability and consistency. The results of this analysis question the validity of the classical spectral criterion for the determination of the stability of space-time discretizations. Stronger conditions that guarantee energy stability for arbitrary initial conditions are proposed. Numerical simulations verifying these results are presented.

Recently, HVEE has completed a novel 3.5 MV single ended accelerator (Singletron™) for the University of Leipzig, Germany. For one of the main applications, the system will be connected to a nanobeamline to achieve submicron resolution. Because the energy stability and ripple of the beam, and beam brightness are of vital importance for the performance of a nanoprobe, special care has been taken in optimizing these parameters. The system consists of an RF source which is directly mounted on the accelerator tube, a switching magnet to bend the beam into a chamber for standard analysis purposes and an analysis magnet that directs the beam into the nanoprobe. The stability of the beam energy was measured at a terminal voltage of 1.881 MV. These measurements were taken during factory acceptance with large production equipment operational, which negatively influenced the stability of the mains. The measured stability was found to be approx. ±50 eV over 5 h, but it is anticipated that this figure will be as good as ±20 eV (i.e. ∼ 10−5) under normal laboratory conditions. The terminal voltage ripple was measured at 2.25 MV to be 25 Vpp (i.e. ∼ 1.1 × 10−5). Finally, the beam brightness of a 2.25 MeV hydrogen beam was measured by the use of two micrometer slit systems. A brightness of approx. 18 Amps · rad−2 m−2 eV−1 was obtained. In this article we will describe the considerations which have led to the layout of the present system.

A fully nonlinear stability analysis is developed for the model of thermal convection in a deep fluid layer presented by Zeytounian [1]. The analysis is completely rigorous and due to the nonlinearities present requires a generalized energy theory.

An actively and passively mode locked solid-state laser system has been constructed, which delivers single 25 ps pulses with energy up to 30 mJ at λ=1.061 μm. The system is characterized by its good time and energy stability, high pump efficiency and low pulse background. This was accomplished by using Nd:Cr:GSGG as active material and by developing a low voltage, solid state external pulse selector. The construction details of the system and its performance are described.

Recirculating, energy-recovery linacs can be used as driver accelerators for high power FELs. Instabilities which arise from fluctuations of the cavity fields are investigated. Energy changes can cause beam loss on apertures, or, when coupled to M 56 , phase oscillations. Both effects change the beam induced voltage in the cavities and can lead to unstable variations of the accelerating field. Stability analysis for small perturbations from equilibrium is performed and threshold currents are determined. Furthermore, the analytical model is extended to include amplitude and phase feedback, with the transfer function in the feedback path presently modeled as a low-pass filter. The feedback gain and bandwidth required for stability are calculated for the high power UV FEL proposed for construction at CEBAF.

In a recent paper on polytrons [H. Herminghaus, Nucl. Instr. and Meth. A305 (1991) 1] it was noted rather marginally that non-isochronous recirculation schemes should offer inherently superior energy stability as compared to isochronous schemes. Meanwhile several discussions showed that this beneficial feature does not seem to be recognized widely in the accelerator community. Therefore, in the following, the mechanism involved is briefly described and some numerical examples of its effect are given.