Knowledge, management and intelligent decision support for protection scheme design and application in electrical power systems

The paper describes a research project carried out inconjunction with two major UK utilities, focusing on the introduction of knowledge management and intelligent decision support to the existing protection design and application processes operated within both companies. A brief overview is provided of the generic design process, and the development of the web-based Design Engineering Knowledge Application System (DEKAS). This system incorporates intelligent case based reasoning (CBR) functionality to address the knowledge management and decision support requirements of each company's design process. The perceived key benefits of DEKAS relating to the management and utilisation of the data, information and knowledge throughout the protection design process is also discussed

3-D Laser Shaping of Ceramic and Ceramic Composite Materials

A versatile, automated, laser-based system, capable of producing complex threedimensional shapes of ceramic and ceramic composite materials, through either controlled layer ablation or solid freeform fabrication, is currently under development. The system comprises a 1.2 kW C021aser, positioning system, beam scanner, non-contacting positioning sensor, beam conditioner and CAD/CAM system. This paper reports progress in relating machine parameters (scan rate, feed, beam power and polarization) to process measurables (material removal rate and surface roughness), and demonstrates the potential for rapid prototyping and direct manufacturing of: (a) rotationally symmetric components based on ablative ceramics such as Si3N4 and (b) graphite fuel cell plenumsMechanical Engineerin

TeV scale resonant leptogenesis from supersymmetry breaking

We propose a model of TeV-scale resonant leptogenesis based upon recent models of the generation of light neutrino masses from supersymmetry-breaking effects with TeV-scale right-handed (rhd) neutrinos, $N_i$. The model leads to naturally large cosmological lepton asymmetries via the resonant behaviour of the one-loop self-energy contribution to $N_i$ decay. Our model addresses the primary problems of previous phenomenological studies of low-energy leptogenesis: a rational for TeV-scale rhd neutrinos with small Yukawa couplings so that the out-of equilibrium condition for $N_i$ decay is satisfied; the origin of the tiny, but non-zero mass splitting required between at least two $N_i$ masses; and the necessary non-trivial breaking of flavour symmetries in the rhd neutrino sector. The low mass-scale of the rhd neutrinos and their superpartners, and the TeV-scale $A$-terms automatically contained within the model offer opportunities for partial direct experimental tests of this leptogenesis mechanism at future colliders.Comment: 10 Pages latex, version for JHE

Supersymmetric Euler-Heisenberg effective action: Two-loop results

The two-loop Euler-Heisenberg-type effective action for N = 1 supersymmetric QED is computed within the background field approach. The background vector multiplet is chosen to obey the constraints D_\a W_\b = D_{(\a} W_{\b)} = const, but is otherwise completely arbitrary. Technically, this calculation proves to be much more laborious as compared with that carried out in hep-th/0308136 for N = 2 supersymmetric QED, due to a lesser amount of supersymmetry. Similarly to Ritus' analysis for spinor and scalar QED, the two-loop renormalisation is carried out using proper-time cut-off regularisation. A closed-form expression is obtained for the holomorphic sector of the two-loop effective action, which is singled out by imposing a relaxed super self-duality condition.Comment: 27 pages, 2 eps figures, LaTeX; V2: typos corrected, comments and reference adde

Dynamic Bayesian Combination of Multiple Imperfect Classifiers

Classifier combination methods need to make best use of the outputs of multiple, imperfect classifiers to enable higher accuracy classifications. In many situations, such as when human decisions need to be combined, the base decisions can vary enormously in reliability. A Bayesian approach to such uncertain combination allows us to infer the differences in performance between individuals and to incorporate any available prior knowledge about their abilities when training data is sparse. In this paper we explore Bayesian classifier combination, using the computationally efficient framework of variational Bayesian inference. We apply the approach to real data from a large citizen science project, Galaxy Zoo Supernovae, and show that our method far outperforms other established approaches to imperfect decision combination. We go on to analyse the putative community structure of the decision makers, based on their inferred decision making strategies, and show that natural groupings are formed. Finally we present a dynamic Bayesian classifier combination approach and investigate the changes in base classifier performance over time.Comment: 35 pages, 12 figure

Analysis of harmonic distortion in an Integrated Power System for naval applications

Thesis (Nav. E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (p. 89-91).This research quantifies the voltage distortion over the broad range of operating conditions experienced by a Naval warship. A steady state model of an Integrated Power System (IPS) was developed in a commercially available power system simulation tool. The system chosen for this study was a three-phase, 4160 VAC, 80 MW power system with a 450 VAC bus to supply traditional ship service loads. Sensitive loads, such as combat systems equipment, are isolated from the harmonic content of the 450 volt bus via solid state inverters. Power generation for this system included two 30 MW and two 10 MW generators. The sizing of these generators was based on operating configurations that would result in the best fuel efficiency under the most common loading conditions. Model components were simulated and compared to data recorded for the U.S. Navy's Full Scale Advanced Development (FSAD) test system for the IPS at the Philadelphia Land Based Engineering Site (LBES). The propulsion motor used in the simulations was developed based on the advanced induction motor installed at LBES.(cont.) Various loading conditions, including battle, cruise and anchor were simulated for both 10⁰F and 90⁰F ambient design conditions and with propulsion loads ranging from 0% to 100%. Numerous system configuration changes were implemented to determine their impact on system harmonics. These included operating the propulsion converter front end rectifiers in both controlled (varying commutation angle) and uncontrolled (diode bridge) configurations; implementation of both twelve and six pulse rectification; and installation of a tuned passive 5th harmonic filter. The simulation results are compared to both IEEE Std 519-1992 and Mil-Std 1399.by Edward G. West.S.M.Nav.E

Form factors of the exotic baryons with isospin I=5/2

The electromagnetic form factors of the exotic baryons are calculated in the framework of the relativistic quark model at small and intermediate momentum transfer. The charge radii of the E+++ baryons are determined.Comment: 12pages, 2 figure

Magnetic field diagnostics and spatio-temporal variability of the solar transition region

Magnetic field diagnostics of the transition region from the chromosphere to the corona faces us with the problem that one has to apply extreme UV spectro-polarimetry. While for coronal diagnostic techniques already exist through infrared coronagraphy above the limb and radio observations on the disk, for the transition region one has to investigate extreme UV observations. However, so far the success of such observations has been limited, but there are various projects to get spectro-polarimetric data in the extreme UV in the near future. Therefore it is timely to study the polarimetric signals we can expect for such observations through realistic forward modeling. We employ a 3D MHD forward model of the solar corona and synthesize the Stokes I and Stokes V profiles of C IV 1548 A. A signal well above 0.001 in Stokes V can be expected, even when integrating for several minutes in order to reach the required signal-to-noise ratio, despite the fact that the intensity in the model is rapidly changing (just as in observations). Often this variability of the intensity is used as an argument against transition region magnetic diagnostics which requires exposure times of minutes. However, the magnetic field is evolving much slower than the intensity, and thus when integrating in time the degree of (circular) polarization remains rather constant. Our study shows the feasibility to measure the transition region magnetic field, if a polarimetric accuracy on the order of 0.001 can be reached, which we can expect from planned instrumentation.Comment: Accepted for publication in Solar Physics (4.Mar.2013), 19 pages, 9 figure

Simulations of neutron background in a time projection chamber relevant to dark matter searches

Presented here are results of simulations of neutron background performed for a time projection chamber acting as a particle dark matter detector in an underground laboratory. The investigated background includes neutrons from rock and detector components, generated via spontaneous fission and (alpha, n) reactions, as well as those due to cosmic-ray muons. Neutrons were propagated to the sensitive volume of the detector and the nuclear recoil spectra were calculated. Methods of neutron background suppression were also examined and limitations to the sensitivity of a gaseous dark matter detector are discussed. Results indicate that neutrons should not limit sensitivity to WIMP-nucleon interactions down to a level of (1 - 3) x 10^{-8} pb in a 10 kg detector.Comment: 27 pages (total, including 3 tables and 11 figures). Accepted for publication in Nuclear Instruments and Methods in Physics Research - Section

Scale-free memory model for multiagent reinforcement learning. Mean field approximation and rock-paper-scissors dynamics

A continuous time model for multiagent systems governed by reinforcement learning with scale-free memory is developed. The agents are assumed to act independently of one another in optimizing their choice of possible actions via trial-and-error search. To gain awareness about the action value the agents accumulate in their memory the rewards obtained from taking a specific action at each moment of time. The contribution of the rewards in the past to the agent current perception of action value is described by an integral operator with a power-law kernel. Finally a fractional differential equation governing the system dynamics is obtained. The agents are considered to interact with one another implicitly via the reward of one agent depending on the choice of the other agents. The pairwise interaction model is adopted to describe this effect. As a specific example of systems with non-transitive interactions, a two agent and three agent systems of the rock-paper-scissors type are analyzed in detail, including the stability analysis and numerical simulation. Scale-free memory is demonstrated to cause complex dynamics of the systems at hand. In particular, it is shown that there can be simultaneously two modes of the system instability undergoing subcritical and supercritical bifurcation, with the latter one exhibiting anomalous oscillations with the amplitude and period growing with time. Besides, the instability onset via this supercritical mode may be regarded as "altruism self-organization". For the three agent system the instability dynamics is found to be rather irregular and can be composed of alternate fragments of oscillations different in their properties.Comment: 17 pages, 7 figur