6,451 research outputs found
Coherent Interactions in Nucleus-Nucleus Collisions
At the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National
Laboratory and at the Large Hadron Collider (LHC) at CERN, particles will be
produced in coherent and diffractive nuclear interactions. In extremely
peripheral nuclear collisions (b2R), coherent interactions occur at very
high rates and are dominated by photon-Pomeron or photon-meson processes. In
these reactions, the photon and the Pomeron/meson from the electromagnetic and
nuclear fields couple coherently to all nucleons. The rates for photonuclear
interactions are roughly two orders of magnitude larger than for two-photon
interactions at comparable center-of-mass energies.Comment: 10 pages, 4 figures, Presented at the IXth Blois Workshop on Elastic
and Diffractive Scattering, Pruhonice near Prague, Czech Republic, June 9-15,
200
System size dependence of two-particle angular correlations in p+p, Cu+Cu and Au+Au collisions
We present a systematic study of two-particle angular correlations in p+p,
Cu+Cu and Au+Au collisions over a broad range of pseudorapidity and azimuthal
angle. The PHOBOS detector has a uniquely large angular coverage for inclusive
charged particles, which allows for the study of correlations on both long- and
short-range scales. A complex two-dimensional correlation structure emerges
which is interpreted in the context of a cluster model. The cluster size and
its decay width are extracted from the two-particle pseudorapidity correlation
function. The cluster size found in semi-central Cu+Cu and Au+Au collisions is
comparable to that found in p+p but a non-trivial increase of cluster size with
decreasing centrality is observed. Moreover, the comparison between Cu+Cu and
Au+Au systems shows an interesting scaling of the cluster size with the
measured fraction of total cross section (which is related to ),
suggesting a geometric origin. These results should provide insight into the
hadronization stage of the hot and dense medium created in heavy ion
collisions.Comment: 4 pages, 5 figures, presented at the 19th International Conference on
Ultra-Relativistic Nucleus-Nucleus Collisions, "Quark Matter 2008", Jaipur,
India, February 4-10, 200
Vertical axis wind turbine with continuous blade angle adjustment
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 26).The author presents a concept for a vertical axis wind turbine that utilizes each blade's entire rotational cycle for power generation. Each blade has its own vertical axis of rotation and is constrained to rotate at the rate of one half of a revolution per full revolution of the rotor. For a rotor of radius r and blades of width b, a technical analysis predicts a theoretical maximum power coefficient of CP = b 2r+b, neglecting wind flow interference by upwind blades. This theoretical power coefficient is generally greater than the efficiency of a typical Savonius wind turbine (CP ~~ 0.15), and it reaches CP = 0.5 at the limiting blade width, b = 2r. The analysis also predicts a static torque and optimal tip-speed ratio that are both greater than those of a Savonius wind turbine with similar blade dimensions. Design considerations for implementing the kinematic constraint and for blade adjustment to account for changes in wind direction are discussed, and the author's prototype is presented. Testing of the prototype demonstrated that implementation of the kinematic constraint is feasible, and that efficiencies greater than those achievable by a Savonius turbine are plausible. In 4 m s wind conditions, the prototype yielded an estimated CP of 0.15, with much room for improvement through design changes and blade optimization in future iterations of this style of turbine.by Samuel Bruce Weiss.S.B
Asymptotic behavior of Palais-Smale sequences associated with fractional Yamabe type equations
In this paper, we analyze the asymptotic behavior of Palais-Smale sequences
associated with fractional Yamabe type equations on an asymptotically
hyperbolic Riemannian manifold. We prove that Palais-Smale sequences can be
decomposed into the solution of the limit equation plus a finite number of
bubbles, which are the rescaling of the fundamental solutions to the fractional
Yamabe equation on Euclidean space. We also verify the non-interfering fact for
multi-bubbles.Comment: 29 page
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