David Newman
University of Alaska Fairbanks, Physics, Faculty Member
The initiation, termination, and control of internal transport barriers associated with E × B flow shear near local minima of magnetic shear are examined for burning plasmas to determine if the positive feedback loops between profiles,... more
The initiation, termination, and control of internal transport barriers associated with E × B flow shear near local minima of magnetic shear are examined for burning plasmas to determine if the positive feedback loops between profiles, instability, transport, and flow shear operate in regimes with fusion self-heating. A five-field transport model for the evolution of profiles of density, ion and electron temperature, ion and electron fluctuations, and radial electric field is utilized to examine the efficacy of controls associated with external inputs of heat and particles, including neutral beam injection, RF, pellets, and gas puffing. The response of the plasma to these inputs is studied in the presence of self-heating. The latter is affected by the external inputs and their modification of profiles and is, therefore, not an external control. Provided sufficient external power is applied, internal transport barriers can be created and controlled, both in ion and electron channels....
Research Interests: Physics, Materials Science, Atomic Physics, Tokamak, Classical Physics, and 3 morePlasma, Electron, and Ion
Many complex infrastructure systems, such as electric power transmission grids, display characteristics of a critical or near critical behavior with a risk of large cascading failures. Understanding this risk and its relation to the... more
Many complex infrastructure systems, such as electric power transmission grids, display characteristics of a critical or near critical behavior with a risk of large cascading failures. Understanding this risk and its relation to the system state as it evolves could allow for a more realistic risk assessment and even for mitigation measures. We use the OPA model of cascading blackouts and grid evolution to describe and quantify regimes of criticality of the power grid.
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In order to study the complex global dynamics of a series of blackouts in power transmission systems a dynamical model of such a system has been developed. This model includes a simple representation of the dynamical evolution by... more
In order to study the complex global dynamics of a series of blackouts in power transmission systems a dynamical model of such a system has been developed. This model includes a simple representation of the dynamical evolution by incorporating the growth of power demand, the engineering response to system failures, and the upgrade of generator capacity. Two types of blackouts have been identified, each having different dynamical properties. One type of blackout involves the loss of load due to transmission lines reaching their load limits but no line outages. The second type of blackout is associated with multiple line outages. The dominance of one type of blackout over the other depends on operational conditions and the proximity of the system to one of its two critical points. The model displays characteristics such as a probability distribution of blackout sizes with power tails similar to that observed in real blackout data from North America.
Research Interests: Applied Mathematics, Computer Science, Physics, Medicine, Chaos, and 15 moreInterdisciplinary, Power Transmission, Power Plants, Electric Power System, Operant Conditioning, Numerical Analysis and Computational Mathematics, Dynamic Model of WSN, Blackout, Electric Power Transmission, Critical Point, Complex Dynamics, Dynamic Properties, Load Shedding, dynamic model, and Physical Phenomena
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At the November 14-15, 2000, meeting of the Fusion Energy Sciences Advisory Committee, a Panel was set up to address questions about the Theory and Computing program, posed in a charge from the Office of Fusion Energy Sciences (see... more
At the November 14-15, 2000, meeting of the Fusion Energy Sciences Advisory Committee, a Panel was set up to address questions about the Theory and Computing program, posed in a charge from the Office of Fusion Energy Sciences (see Appendix A). This area was of theory and computing/simulations had been considered in the FESAC Knoxville meeting of 1999 and in the deliberations of the Integrated Program Planning Activity (IPPA) in 2000. A National Research Council committee provided a detailed review of the scientific quality of the fusion energy sciences program, including theory and computing, in 2000.
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Research Interests: Applied Mathematics, Computer Science, Algorithms, Decision Making, Nonlinear dynamics, and 15 moreRisk Taking, Science and Technology, Medicine, Risk Analysis, Chaos, Humans, Computer Simulation, Risk Aversion, System Theory, Complex network, Numerical Analysis and Computational Mathematics, Statistical models, Dynamic Model of WSN, dynamic model, and consumer demand
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Research Interests: Fractal Geometry, Political Science, Nonlinear dynamics, Power System, Cellular Automata, and 12 moreRisk assessment, Complex System, Power Transmission, Financial Market, Self Organization, Spin Glass, Risk Assessment, Electric Power, Plate tectonic, Network Model, Music Information Dynamics, and Adverse effect
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Research Interests: Stochastic Process, Research Agenda, Risk Analysis, Complex System, Probability Distribution & Applications, and 11 morePower Transmission, Power System Security, Phase transition, Critical Loads, Branching Process, Electric Power, North American, Power System Modeling, Reference Point, Complex Dynamics, and Probability Distribution
Research Interests: Computer Science, Probability Distribution & Applications, Power Transmission, North America, Self Organization, and 10 moreCriticality, Operant Conditioning, Dynamic Model of WSN, Blackout, Critical Point, Cascading Failure, Complex Dynamics, Dynamic Properties, dynamic model, and Probability Distribution
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Research Interests: Computer Science, Risk assessment, Risk Analysis, Complex System, Probability Distribution & Applications, and 9 morePower Transmission, Power Law, Critical Infrastructure, Risk Assessment, Dynamic Model of WSN, Power Law Distribution, Probabilistic Model, dynamic model, and Probability Distribution
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We compare and test statistical estimates of failure propagation in data from versions of a probabilistic model of loading-dependent cascading failure and a power system blackout model of cascading transmission line overloads. The... more
We compare and test statistical estimates of failure propagation in data from versions of a probabilistic model of loading-dependent cascading failure and a power system blackout model of cascading transmission line overloads. The comparisons suggest mechanisms affecting failure propagation and are an initial step toward monitoring failure propagation from practical system data. Approximations to the probabilistic model describe the forms of probability distribution of cascade sizes.
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We propose an analytically tractable model of loading-dependent cascading failure that captures some of the salient features of large blackouts of electric power transmission systems. This leads to a new application and derivation of the... more
We propose an analytically tractable model of loading-dependent cascading failure that captures some of the salient features of large blackouts of electric power transmission systems. This leads to a new application and derivation of the quasibinomial distribution and its generalization to a saturating form with an extended parameter range. The saturating quasibinomial distribution of the number of failed components has a power-law region at a critical loading and a significant probability of total failure at higher loadings.