2,567 research outputs found
REGIONAL IMPACTS OF ALTERNATIVE ENERGY ALLOCATION STRATEGIES
In this paper we report on the development and use of an information system for state or regional energy planning which attempts to deal with both external effects and information needs. A regional economic model is included as an integral part of the information system. External impacts of alternative energy allocation rules are simulated and criteria for evaluating these impacts are presented.Community/Rural/Urban Development,
Improving access to information and restoring the public’s faith in democracy through deliberative institutions
Advocates for public deliberation claim that increased citizen involvement in political decision-making can improve democratic governance. Studies have shown that deliberation can be beneficial for participants, but less is known about its impact on the wider public. Looking at the case of Citizens’ Initiative Reviews in Oregon, Katherine R. Knobloch shows that knowing about or using the information provided by deliberative institutions can improve the public’s faith in self-government
Competition between Traveling Fluid Waves of Left and Right Spiral Vortices and Their Different Amplitude Combinations
Stability, bifurcation properties, and the spatiotemporal behavior of
different nonlinear combination structures of spiral vortices in the counter
rotating Taylor-Couette system are investigated by full numerical simulations
and by coupled amplitude equation approximations. Stable cross-spiral
structures with continuously varying content of left and right spiral modes are
found. They provide a stability transferring connection between the initially
stable, axially counter propagating wave states of pure spirals and the axially
standing waves of so-called ribbons that become stable slightly further away
from onset of vortex flow.Comment: 4 pages, 5 figure
Development of an Optimized Quadrupole Resonator at HZB
Abstract Current superconducting cavities are generally made of solid Niobium. A possibility to reduce cost as well as increase the quality factor and or accelerating fields is to use thin film coated cavities. Apart from Niobium thin films, other substances such as Magnesium diboride, Niobium nitride and Niobium tin are promising candidates. Measuring the RF properties of superconducting thin films, specifically the surface resistance, with a high resolution at frequencies, magnetic field levels and operating temperature as realized in RF cavities, is needed to drive forward this development. Presently, only few setups exist capable of measuring the surface resistance of thin films samples with a resolution in the nano ohm range at RF frequencies below 3 GHz. A dedicated test stand consisting of a quadrupole resonator is therefore being constructed at the Helmholtz Zentrum Berlin. Starting with the 400 MHz quadrupole resonator developed by CERN, the design was adapted and optimized to 433 MHz making available the higher harmonic mode at 1.3 GHz for RF characterization of samples in the L band using simulation data obtained with CST Microwave Studio. A number of relevant figures of merit have been improved to provide a higher resolution, a lower peak electric field and less sensitivity to microphonics, enabling measurements with high resolution at high magnetic field level
Solidification fronts in supercooled liquids: how rapid fronts can lead to disordered glassy solids
We determine the speed of a crystallisation (or more generally, a
solidification) front as it advances into the uniform liquid phase after the
system has been quenched into the crystalline region of the phase diagram. We
calculate the front speed by assuming a dynamical density functional theory
model for the system and applying a marginal stability criterion. Our results
also apply to phase field crystal (PFC) models of solidification. As the
solidification front advances into the unstable liquid phase, the density
profile behind the advancing front develops density modulations and the
wavelength of these modulations is a dynamically chosen quantity. For shallow
quenches, the selected wavelength is precisely that of the crystalline phase
and so well-ordered crystalline states are formed. However, when the system is
deeply quenched, we find that this wavelength can be quite different from that
of the crystal, so that the solidification front naturally generates disorder
in the system. Significant rearrangement and ageing must subsequently occur for
the system to form the regular well-ordered crystal that corresponds to the
free energy minimum. Additional disorder is introduced whenever a front
develops from random initial conditions. We illustrate these findings with
results obtained from the PFC.Comment: 14 pages, 7 figure
Some analytical results for an algebraic flux correction scheme for a steady convection-diffusion equation in 1D
Algebraic flux correction schemes are nonlinear discretizations of convection dominated problems. In this work, a scheme from this class is studied for a steady-state convection--diffusion equation in one dimension. It is proved that this scheme satisfies the discrete maximum principle. Also, as it is a nonlinear scheme, the solvability of the linear subproblems arising in a Picard iteration is studied, where positive and negative results are proved. Furthermore, the non-existence of solutions for the nonlinear scheme is proved by means of counterexamples. Therefore, a modification of the method, which ensures the existence of a solution, is proposed. A weak version of the discrete maximum principle is proved for this modified method
Analysis of algebraic flux correction schemes
A family of algebraic flux correction schemes for linear boundary value problems in any space dimension is studied. These methods' main feature is that they limit the fluxes along each one of the edges of the triangulation, and we suppose that the limiters used are symmetric. For an abstract problem, the existence of a solution, existence and uniqueness of the solution of a linearized problem, and an a priori error estimate, are proved under rather general assumptions on the limiters. For a particular (but standard in practice) choice of the limiters, it is shown that a local discrete maximum principle holds. The theory developed for the abstract problem is applied to convection-diffusion-reaction equations, where in particular an error estimate is derived. Numerical studies show its sharpness
Recommended from our members
A local projection stabilization finite element method with nonlinear crosswind diffusion for convection-diffusion-reaction equations
An extension of the local projection stabilization (LPS) finite element method for convection-diffusion-reaction equations is presented and analyzed, both in the steady-state and the transient setting. In addition to the standard LPS method, a nonlinear crosswind diffusion term is introduced that accounts for the reduction of spurious oscillations. The existence of a solution can be proved and, depending on the choice of the stabilization parameter, also its uniqueness. Error estimates are derived which are supported by numerical studies. These studies demonstrate also the reduction of the spurious oscillations
Amplitude equations for a system with thermohaline convection
The multiple scale expansion method is used to derive amplitude equations for
a system with thermohaline convection in the neighborhood of Hopf and Taylor
bifurcation points and at the double zero point of the dispersion relation. A
complex Ginzburg-Landau equation, a Newell-Whitehead-type equation, and an
equation of the type, respectively, were obtained. Analytic
expressions for the coefficients of these equations and their various
asymptotic forms are presented. In the case of Hopf bifurcation for low and
high frequencies, the amplitude equation reduces to a perturbed nonlinear
Schr\"odinger equation. In the high-frequency limit, structures of the type of
"dark" solitons are characteristic of the examined physical system.Comment: 21 pages, 8 figure
- …