881 research outputs found

    Emission Dispatch Problem with Cubic Function Considering Transmission Loss using Particle Swarm Optimization

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    In this research, authors have exploited particle swarm optimization (PSO) technique for solving the emission dispatch problem. Authors have used cubic function, instead of quadratic function, to solve emission dispatch problem to make the system more robust against nonlinearities of actual power generator. PSO with cubic function reveals better results by optimizing less emission of hazardous gases, transmission losses and showing robustness against nonlinearities than simplified direct search method (SDSM)

    Neutrons from multiplicity-selected Au-Au collisions at 150, 250, 400, and 650 AMeV

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    We measured neutron triple-differential cross sections from multiplicity-selected Au-Au collisions at 150, 250, 400, and 650 \AMeV. The reaction plane for each collision was estimated from the summed transverse velocity vector of the charged fragments emitted in the collision. We examined the azimuthal distribution of the triple-differential cross sections as a function of the polar angle and the neutron rapidity. We extracted the average in--plane transverse momentum ⟨Px⟩\langle P_x\rangle and the normalized observable ⟨Px/P⊥⟩\langle P_x/P_\perp\rangle, where P⊥P_\perp is the neutron transverse momentum, as a function of the neutron center-of-mass rapidity, and we examined the dependence of these observables on beam energy. These collective flow observables for neutrons, which are consistent with those of protons plus bound nucleons from the Plastic Ball Group, agree with the Boltzmann--Uehling--Uhlenbeck (BUU) calculations with a momentum--dependent interaction. Also, we calculated the polar-angle-integrated maximum azimuthal anisotropy ratio R from the value of ⟨Px/P⊥⟩\langle P_x/P_\perp\rangle.Comment: 20 LaTeX pages. 11 figures to be faxed on request, send email to sender's addres

    Collapse of Flux Tubes

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    The dynamics of an idealized, infinite, MIT-type flux tube is followed in time as the interior evolves from a pure gluon field to a q‾ q\overline q \ q plasma. We work in color U(1). q‾ q\overline q\ q pair formation is evaluated according to the Schwinger mechanism using the results of Brink and Pavel. The motion of the quarks toward the tube endcaps is calculated by a Boltzmann equation including collisions. The tube undergoes damped radial oscillations until the electric field settles down to zero. The electric field stabilizes the tube against pinch instabilities; when the field vanishes, the tube disintegrates into mesons. There is only one free parameter in the problem, namely the initial flux tube radius, to which the results are very sensitive. Among various quantities calculated is the mean energy of the emitted pions.Comment: 16 pages plus 12 figures. RevTex3. DOE/ER/40427-160N9

    The Chromo-Dielectric Soliton Model: Quark Self Energy and Hadron Bags

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    The chromo-dielectric soliton model (CDM) is Lorentz- and chirally-invariant. It has been demonstrated to exhibit dynamical chiral symmetry breaking and spatial confinement in the locally uniform approximation. We here study the full nonlocal quark self energy in a color-dielectric medium modeled by a two parameter Fermi function. Here color confinement is manifest. The self energy thus obtained is used to calculate quark wave functions in the medium which, in turn, are used to calculate the nucleon and pion masses in the one gluon exchange approximation. The nucleon mass is fixed to its empirical value using scaling arguments; the pion mass (for massless current quarks) turns out to be small but non-zero, depending on the model parameters.Comment: 24 pages, figures available from the author

    Hard probes in heavy ion collisions at the LHC: PDFs, shadowing and pApA collisions

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    This manuscript is the outcome of the subgroup ``PDFs, shadowing and pApA collisions'' from the CERN workshop ``Hard Probes in Heavy Ion Collisions at the LHC''. In addition to the experimental parameters for pApA collisions at the LHC, the issues discussed are factorization in nuclear collisions, nuclear parton distributions (nPDFs), hard probes as the benchmark tests of factorization in pApA collisions at the LHC, and semi-hard probes as observables with potentially large nuclear effects. Also, novel QCD phenomena in pApA collisions at the LHC are considered. The importance of the pApA program at the LHC is emphasized.Comment: The writeup of the working group "PDFs, shadowing and pApA collisions" for the CERN Yellow Report on Hard Probes in Heavy Ion Collisions at the LHC, 121 pages. Subgroup convenors: K.J. Eskola, J.w. Qiu (theory) and W. Geist (experiment). Editor: K.J. Eskol

    A WORKFLOW FOR GEOMETRIC COLOUR PHOTOGRAPHY OF PAINTED SURFACES

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    Colour fidelity is vital when documenting painted surfaces. The 2.5D nature of many painted surfaces makes orthophotos and digital surface models (DSMs) common products of the documentation process. This paper presents a workflow to combine photographic and photogrammetric methods to produce aligned colour and depth (orthophotos and DSMs). First, two photogrammetric software (Agisoft Photoscan and Capturing Reality Reality Capture) were tested to determine if they adjusted the colour data during the processing stages. It was found that Photoscan can produce 16-bit orthophotos without manipulating the data; however, Reality Capture is currently limited to 8-bit results. When capturing a surface using photogrammetry, it is common to use the same data for colour and depth. The presented workflow, however, argues that better colour accuracy can be achieved by capturing the two datasets separately and combining them in photogrammetric software. The workflow is demonstrated through the documentation of an unnamed religious painting from the 17th century
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