Exact Solutions in SFT and Marginal Deformation in BCFT

In this note we will study solution of open bosonic string field theory based on action of operators from chiral algebra of boundary conformal field theory on identity element of string field theory star algebra. We will demonstrate that the string field theory action for fluctuation fields around this classical solution can be mapped to the string field theory action defined through the new boundary conformal field theory that arises from the original one through the marginal deformation inserted on the world-sheet boundary.Comment: 15 pages, references adde

Optimal Cross-Wind Towing and Power Generation with Tethered Kites

Non-powered flight vehicles such as kites can provide a means of transmitting wind energy from higher altitudes to the ground via tethers. Although there have been many proposals for systems to extract wind energy from higher altitudes, this paper focuses on the use of a light lifting body at the end of a tether to generate useful power. Two major configurations are studied: 1) the kite is used to tow a ground vehicle in the cross-wind direction, 2) the kite is flown to generate power using a ground generator. In both cases, the useful work done by the kite is transmitted to the ground through the tether. Both applications require automatic control of the kite. A simplified system model is used to study the nature of the optimal trajectories of the system for different wind speeds. Numerical results illustrate that optimal power generation requires complex three-dimensional kite trajectories, whereas cross-wind towing requires much simpler trajectories. A feedback tracking controller is demonstrated for tracking the kite trajectories in the presence of unsteady winds

Intelligent Systems for Green Developments

Alternative local energy sources are becoming increasingly popular, creating a new network of small suppliers. Fluctuations in the supply from such sources may cause instability and inefficiency in electricity distribution networks. The IdeaNeD consortium in the Netherlands aims to solve these problems

Combined simulation method for improved performance in grid integration studies including multi-terminal VSC-HVDC

This paper presents an interfacing method to combine stability-type simulations with electro-magnetic transients (EMT) calculation. The stability-type simulation is coupled with the EMT simulation by Thévenin-equivalent variable source representations, whereas the EMT-type simulator is connected to the stability-type simulation by Fourier analysis. The paper describes this procedure and elaborates on the numerical performance of this mutual coupling, which is done by studying an exemplary test case. The focus is on integrating multi-terminal VSC-HVdc schemes in stability-type simulations