A5024866420- Magnetic confinement fusion research
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Theoretical and Computational Physics
- Distributed and Parallel Computing Systems
- Crystallography and molecular interactions
- Laser-Plasma Interactions and Diagnostics
- Infrastructure Resilience and Vulnerability Analysis
- Nuclear Physics and Applications
- Fusion materials and technologies
- Fluid Dynamics and Turbulent Flows
- Scientific Computing and Data Management
- Complex Network Analysis Techniques
- Parallel Computing and Optimization Techniques
- Power System Reliability and Maintenance
- Advanced Data Storage Technologies
- Physics of Superconductivity and Magnetism
- Complex Systems and Time Series Analysis
- Atomic and Subatomic Physics Research
- Nuclear reactor physics and engineering
- Fractional Differential Equations Solutions
City of Cape Town
2024
Oak Ridge National Laboratory
2010-2020
University of Alaska Fairbanks
2007
Martin Marietta Materials (United States)
1990-2003
Universidad Carlos III de Madrid
2002
Lodestar Research Corporation (United States)
1996
University of Wisconsin–Madison
1996
Olin Corporation (United States)
1990
Union Carbide (United States)
1984
Fusion Academy
1982
We give an overview of a complex systems approach to large blackouts electric power transmission caused by cascading failure. Instead looking at the details particular blackouts, we study statistics and dynamics series with approximate global models. Blackout data from several countries suggest that frequency is governed law. The law makes risk consequential consistent system being designed operated near critical point. Power overall loading or stress relative operating limits key factor...
Cascading failures in large-scale electric power transmission systems are an important cause of blackouts. Analysis North American blackout data has revealed law (algebraic) tails the size probability distribution which suggests a dynamical origin. With this observation as motivation, we examine cascading failure simplified system model load demand is increased. The represents generators, loads, line network, and operating limits on these components. Two types critical points identified...
We define a model for the evolution of long series electric power transmission system blackouts. The describes opposing forces, which have been conjectured to cause self-organized criticality in There is slow time scale representing forces load growth and capacity fast cascading line overloads outages. scales are coupled: leads outages lead increased capacity. result dynamic equilibrium blackouts all sizes occur. means study complex dynamics this equilibrium. Markov property briefly...
To explore the character of transport in a plasma turbulence model with avalanche transport, motion tracer particles has been followed. Both time evolution moments distribution function particle radial positions, 〈|r(t)−r(0)|n〉, and their finite scale Lyapunov number are used to determine anomalous diffusion exponent, ν. The numerical results show that mechanism is superdiffusive an exponent ν close 0.88±0.07. exit times trapped into stochastic jets also determined. These have lowest...
Numerical evidence of nondiffusive transport in three-dimensional, resistive pressure-gradient-driven plasma turbulence is presented. It shown that the probability density function (pdf) tracer particles' radial displacements strongly non-Gaussian and exhibits algebraic decaying tails. To model these results we propose a macroscopic for pdf based on use fractional derivatives space time incorporate unified way space-time nonlocality (non-Fickian transport), non-Gaussianity, scaling. The...
Transport of tracer particles is studied in a model three-dimensional, resistive, pressure-gradient-driven plasma turbulence. It shown that this system transport anomalous and cannot be described the context standard diffusion paradigm. In particular, probability density function (pdf) radial displacements tracers strongly non-Gaussian with algebraic decaying tails, moments exhibit superdiffusive scaling. To these results we present fractional derivatives space time. The incorporates unified...
A simple model for a power transmission system is presented. In this model, disturbances of all sizes may occur. They are randomly triggered and have the characteristic behavior avalanches. single parameter describes scaling avalanche size. This combines measure closeness to maximum load, size transferred loads during an overloading event, connectivity system. The probability distribution function disturbance has power-scaling range with exponent close -1.
In order to study the complex global dynamics of a series blackouts in power transmission systems dynamical model such system has been developed. This includes simple representation evolution by incorporating growth demand, engineering response failures, and upgrade generator capacity. Two types have identified, each having different properties. One type blackout involves loss load due lines reaching their limits but no line outages. The second is associated with multiple dominance one over...
A model for plasma transport near marginal stability is presented. The based on subcri- tical resistive pressure-gradient-driven turbulence. Three-dimensional nonlinear calculations this show effective subcritical mean profiles. This exhibits some of the characteristic properties self-organized criticality. Perturbative techniques are used to elucidate properties. Propagation positive and negative pulses studied. observed results suggest a possible explanation apparent nonlocal effects ob-...
The use of reaction-diffusion models rests on the key assumption that diffusive process is Gaussian. However, a growing number studies have pointed out presence anomalous diffusion, and there need to understand reactive systems in this type non-Gaussian diffusion. Here we study front dynamics where diffusion due asymmetric Levy flights. Our approach consists replacing Laplacian operator by fractional order alpha, whose fundamental solutions are alpha-stable distributions exhibit power law...
Electric power transmission systems are a key infrastructure, and blackouts of these have major consequences for the economy national security. Analyses blackout data suggest that size distributions law form over much their range. This result is an indication behave as complex dynamical system. We use simulation upgrading system to investigate how dynamics impact assessment mitigation risk. The failures in needs be approached with care. efforts can move new dynamic equilibrium while...
The Advanced Toroidal Facility (ATF), now under construction at Oak Ridge National Laboratory, will be the world’s largest stellarator experiment when it begins operation in early 1987. It have a 2.1-m major radius and 0.3-m average plasma radius, magnetic field capability of up to 2 T for 5-s pulse 1 steady state, 5 MW heating. ATF is designed study wide range toroidal confinement issues, including stability high-beta plasmas, low-collisionality transport, impurity behavior, configuration...
Fluctuation-induced fluxes have a bursty character. As consequence, significant part of the total particle flux is carried out by sporadic, large transport bursts. The local distribution function consistent with near-Gaussian character fluctuations. radial dependence statistical properties plasma fluctuations and induced been investigated in boundary region TJ-I tokamak [I. García-Cortés et al., Phys. Fluids B 4, 4007 (1992)] TJ-IU torsatron [E. Ascasibar Plasma Physics Controlled Fusion...
The intensity of single-crystal Bragg peaks obtained by mapping neutron time-of-flight event data into reciprocal space and integrating in various ways is compared. These methods include spherical integration with a fixed radius, ellipsoid fitting the peak intensity, one-dimensional profile fitting. In comparison to intensities real detector histogram space, integrated result better agreement factors more accurate atomic parameters. Furthermore, structure refinement using from demonstrated...
The nonlinear evolution of resistive pressure-gradient-driven turbulence with diamagnetic effects included generates a dc electric field (poloidal velocity) through the convective nonlinearity in momentum balance equation. This radial has strong shear and contributes to saturation turbulence; its effect on level is more important than change time length scales modes by direct ω* effects.
A model for blackouts in electric power transmission systems is implemented and studied simple networks with a regular structure. The describes load demand network improvements evolving on slow timescale as well the fast dynamics of cascading overloads outages. are demonstrated system networks. depend weakly topologies tested. probability distribution functions measures events show existence power-dependent tails.
Electric power transmission systems are a key infrastructure and blackouts of these have major direct indirect consequences on the economy national security. Analysis North American Electrical Reliability Council blackout data suggests existence size distributions with tails. This is an indication that dynamics behave as complex dynamical system. Here, we investigate how system impact assessment mitigation risk. The failures in needs to be approached care. efforts can move new dynamic...
Critical infrastructures have some of the characteristic properties complex systems. They exhibit infrequent large failures events. These events, though infrequent, often obey a power law distribution in their probability versus size. This behavior suggests that ordinary risk analysis might not apply to these It is thought this comes from different parts systems interacting with each other both space and time. While infrastructure can characteristics on own, reality individual interact even...
Resistive pressure-gradient-driven turbulence causes a modification of the average poloidal flow profile through Reynolds stress. The can be induced diamagnetic term and/or ‘‘seed’’ flow. This leads to several possible results for steady-state profile. If this is such that V″θ≠0 at singular surface, there reduction in linear growth rate and suppression fluctuation. When V″θ = 0 V′θ≠0, stabilization but fluctuation weak.
Equilibrium and stability properties of high-beta torsatrons are investigated using numerical semianalytical techniques based on the method toroidal averaging. The averaged equilibria compared with those obtained full three-dimensional codes. Good agreement is obtained, thus validating approach. plasmas for configurations different aspect ratios numbers field periods studied. role vertical also studied in detail. main conclusion that moderate-aspect-ratio (Ap≲8), self-stabilizing effect...
Evidence is mounting that potentially exploitable properties of technologically and chemically interesting crystalline materials are often attributable to local structure effects, which can be observed as modulated diffuse scattering (mDS) next Bragg diffraction (BD). BD forms a regular sparse grid intense discrete points in reciprocal space. Traditionally, the intensity each peak extracted by integration individual reflection first, followed application required corrections. In contrast,...