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http://hdl.handle.net/2440/12353
2014-08-30T08:12:24ZMultiple UAVs path planning algorithms: a comparative study
http://hdl.handle.net/2440/84723
Title: Multiple UAVs path planning algorithms: a comparative study
Author: Sathyaraj, B.M.; Jain, L.C.; Finn, A.; Drake, S.
Abstract: Unmanned aerial vehicles (UAVs) are used in team for detecting targets and keeping them in its sensor range. There are various algorithms available for searching and monitoring targets. The complexity of the search algorithm increases if the number of nodes is increased. This paper focuses on multi UAVs path planning and Path Finding algorithms. Number of Path Finding and Search algorithms was applied to various environments, and their performance compared. The number of searches and also the computation time increases as the number of nodes increases. The various algorithms studied are Dijkstra’s algorithm, Bellman Ford’s algorithm, Floyd-Warshall’s algorithm and the AStar algorithm. These search algorithms were compared. The results show that the AStar algorithm performed better than the other search algorithms. These path finding algorithms were compared so that a path for communication can be established and monitored.2007-12-31T13:30:00ZRotovibrational spectroscopy of hydrogen peroxide embedded in superfluid helium nanodroplets
http://hdl.handle.net/2440/84455
Title: Rotovibrational spectroscopy of hydrogen peroxide embedded in superfluid helium nanodroplets
Author: Raston, P.; Knapp, C.; Jager, W.
Abstract: We report the infrared depletion spectrum of para- and ortho-hydrogen peroxide embedded in superfluid helium nanodroplets in the OH stretching region. Six transitions were observed in the antisymmetric stretching band (v5) of H2O2, and three in the weaker symmetric stretching band (v1). While rotations about the b- and c-axes are slowed by a factor of [similar]0.4 relative to the gas phase, rotations about the a-axis are not significantly affected; this relates to the rotational speed about the a-axis being too fast for helium density to adiabatically follow. The trans tunneling splitting does not appear to be considerably affected by the helium droplet environment, and is reduced by only 6% relative to the gas phase, under the assumption that the vibrational shifts of the v5 and v1 torsional subbands are the same. The linewidths increase with increasing rotorsional energies, and are significantly narrower for energies which fall within the “phonon gap” of superfluid helium. These narrower lines are asymmetrically broadened, indicative of a dynamical coupling between the H2O2 rotor and surrounding helium density.2010-12-31T13:30:00ZTransparent Dirac potentials in one dimension: the time-dependent case
http://hdl.handle.net/2440/82986
Title: Transparent Dirac potentials in one dimension: the time-dependent case
Author: Dunne, Gerald Vincent; Thies, Michael
Abstract: We generalize the original derivation of transparent, static Schrödinger potentials by Kay and Moses, to obtain a large class of time-dependent transparent Dirac potentials in one spatial dimension. They contain previously found transparent potentials as special cases and play a key role in the semiclassical solution of the (1+1)-dimensional, fermionic quantum field theories of Gross-Neveu and Nambu–Jona-Lasinio types.2012-12-31T13:30:00ZA more accurate reconstruction system matrix for quantitative proton computed tomography
http://hdl.handle.net/2440/82699
Title: A more accurate reconstruction system matrix for quantitative proton computed tomography
Author: Penfold, S.; Rosenfeld, A.; Schulte, R.; Schubert, K.
Abstract: An accurate system matrix is required for quantitative protonCT (pCT) image reconstruction with iterative projection algorithms. The system matrix is composed of chord lengths of individual proton path intersections with reconstruction pixels. In previous work, reconstructions were performed assuming constant intersection chord lengths, which led to systematic errors of the reconstructedprotonstopping powers. The purpose of the present work was to introduce a computationally efficient variable intersection chord length in order to improve the accuracy of the system matrix. An analytical expression that takes into account the discrete stepping nature of the pCT most likely path (MLP) reconstruction procedure was created to describe an angle-dependent effective mean chord length function. A pCT dataset was simulated with GEANT4 using a parallel beam of 200 MeV protons intersecting a computerized head phantom consisting of tissue-equivalent materials with known relative stopping power. The phantom stopping powers were reconstructed with the constant chord length, exact chord length, and effective mean chord length approaches, in combination with the algebraic reconstruction technique. Relative stopping power errors were calculated for each anatomical phantom region and compared for the various methods. It was found that the error of approximately 10% in the mean reconstructedstopping power value for a given anatomical region, resulting from a system matrix with a constant chord length, could be reduced to less than 0.5% with either the effective mean chord length or exact chord length approaches. Reconstructions with the effective mean chord length were found to be approximately 20% faster than reconstructions with an exact chord length. The effective mean chord length method provides the possibility for more accurate, computationally efficient quantitative pCT reconstructions.2008-12-31T13:30:00Z