1,051 research outputs found
A Sampled-data Regulator using Sliding Modes and Exponential Holder for Linear Systems
In a general command tracking and disturbance rejection problem, it is known that a sampled-data controller using zero-order hold may only guarantee asymptotic tracking at the sampling instances, but in general cannot guarantee the absence of ripples between the sampling instants. In this paper, a discrete robust regulator and a sampled-data robust regulator using slide modes techniques and exponential holder are presented. In particular, it is shown that the controller proposed for the sampled-data system ensures asymptotic tracking when applied to the continuous-time system
U B V R I Photometry of Stellar Structures throughout the Disk of the Barred Galaxy NGC 3367
We report new detailed surface U, B, V, R, and I photometry of 81 stellar
structures in the disk of the barred galaxy NGC 3367. The images show many
different structures indicating that star formation is going on in the most
part of the disk. NGC 3367 is known to have a very high concentration of
molecular gas distribution in the central regions of the galaxy and bipolar
synchrotron emission from the nucleus with two lobes (at 6 kpc) forming a
triple structure similar to a radio galaxy. We have determined the U, B, V, R,
and I magnitudes and U - B, B - V, U - V, and V - I colors for the central
region (nucleus), a region which includes supernovae 2003 AA, and 79 star
associations throughout NGC 3367. Estimation of ages of star associations is
very difficult due to several factors, among them: filling factor, metallicity,
spatial distribution of each structure and the fact that we estimated the
magnitudes with a circular aperture of 16 pixels in diameter, equivalent to
kpc. However, if the colors derived for NGC 3367 were similar to
the colors expected of star clusters with theoretical evolutionary star tracks
developed for the LMC and had a similar metallicity, NGC 3367 show 51 percent
of the observed structures with age type SWB I (few tens of Myrs), with seven
sources outside the bright surface brightness visible disk of NGC 3367.Comment: Accepted for publication (abr 2007) in The Astronomical Journal (July
2007 issue
Azimuthal anisotropy and correlations in the hard scattering regime at RHIC
Azimuthal anisotropy () and two-particle angular correlations of high
charged hadrons have been measured in Au+Au collisions at
=130 GeV for transverse momenta up to 6 GeV/c, where hard
processes are expected to contribute significantly. The two-particle angular
correlations exhibit elliptic flow and a structure suggestive of fragmentation
of high partons. The monotonic rise of for GeV/c is
consistent with collective hydrodynamical flow calculations. At \pT>3 GeV/c a
saturation of is observed which persists up to GeV/c.Comment: As publishe
Azimuthal anisotropy of K0S and Lambda + Lambda -bar production at midrapidity from Au+Au collisions at sqrt[sNN]=130 GeV
We report STAR results on the azimuthal anisotropy parameter v2 for strange particles K0S, Lambda , and Lambda -bar at midrapidity in Au+Au collisions at sqrt[sNN]=130 GeV at the Relativistic Heavy Ion Collider. The value of v2 as a function of transverse momentum, pt, of the produced particle and collision centrality is presented for both particles up to pt~3.0 GeV/c. A strong pt dependence in v2 is observed up to 2.0 GeV/c. The v2 measurement is compared with hydrodynamic model calculations. The physics implications of the pt integrated v2 magnitude as a function of particle mass are also discussed.Alle Autoren: C. Adler, Z. Ahammed, C. Allgower, J. Amonett, B. D. Anderson, M. Anderson, G. S. Averichev, J. Balewski, O. Barannikova, L. S. Barnby, J. Baudot, S. Bekele, V. V. Belaga, R. Bellwied, J. Berger, H. Bichsel, A. Billmeier, L. C. Bland, C. O. Blyth, B. E. Bonner, A. Boucham, A. Brandin, A. Bravar, R. V. Cadman, H. Caines, M. Calderón de la Barca Sánchez, A. Cardenas, J. Carroll, J. Castillo, M. Castro, D. Cebra, P. Chaloupka, S. Chattopadhyay, Y. Chen, S. P. Chernenko, M. Cherney, A. Chikanian, B. Choi, W. Christie, J. P. Coffin, T. M. Cormier, J. G. Cramer, H. J. Crawford, W. S. Deng, A. A. Derevschikov, L. Didenko, T. Dietel, J. E. Draper, V. B. Dunin, J. C. Dunlop, V. Eckardt, L. G. Efimov, V. Emelianov, J. Engelage, G. Eppley, B. Erazmus, P. Fachini, V. Faine, K. Filimonov, E. Finch, Y. Fisyak, D. Flierl, K. J. Foley, J. Fu, C. A. Gagliardi, N. Gagunashvili, J. Gans, L. Gaudichet, M. Germain, F. Geurts, V. Ghazikhanian, O. Grachov, V. Grigoriev, M. Guedon, E. Gushin, T. J. Hallman, D. Hardtke, J. W. Harris, T. W. Henry, S. Heppelmann, T. Herston, B. Hippolyte, A. Hirsch, E. Hjort, G. W. Hoffmann, M. Horsley, H. Z. Huang, T. J. Humanic, G. Igo, A. Ishihara, Yu. I. Ivanshin, P. Jacobs, W. W. Jacobs, M. Janik, I. Johnson, P. G. Jones, E. G. Judd, M. Kaneta, M. Kaplan, D. Keane, J. Kiryluk, A. Kisiel, J. Klay, S. R. Klein, A. Klyachko, A. S. Konstantinov, M. Kopytine, L. Kotchenda, A. D. Kovalenko, M. Kramer, P. Kravtsov, K. Krueger, C. Kuhn, A. I. Kulikov, G. J. Kunde, C. L. Kunz, R. Kh. Kutuev, A. A. Kuznetsov, L. Lakehal-Ayat, M. A. C. Lamont, J. M. Landgraf, S. Lange, C. P. Lansdell, B. Lasiuk, F. Laue, A. Lebedev, R. Lednický, V. M. Leontiev, M. J. LeVine, Q. Li, S. J. Lindenbaum, M. A. Lisa, F. Liu, L. Liu, Z. Liu, Q. J. Liu, T. Ljubicic, W. J. Llope, G. LoCurto, H. Long, R. S. Longacre, M. Lopez-Noriega, W. A. Love, T. Ludlam, D. Lynn, J. Ma, R. Majka, S. Margetis, C. Markert, L. Martin, J. Marx, H. S. Matis, Yu. A. Matulenko, T. S. McShane, F. Meissner, Yu. Melnick, A. Meschanin, M. Messer, M. L. Miller, Z. Milosevich, N. G. Minaev, J. Mitchell, V. A. Moiseenko, C. F. Moore, V. Morozov, M. M. de Moura, M. G. Munhoz, J. M. Nelson, P. Nevski, V. A. Nikitin, L. V. Nogach, B. Norman, S. B. Nurushev, G. Odyniec, A. Ogawa, V. Okorokov, M. Oldenburg, D. Olson, G. Paic, S. U. Pandey, Y. Panebratsev, S. Y. Panitkin, A. I. Pavlinov, T. Pawlak, V. Perevoztchikov, W. Peryt, V. A Petrov, M. Planinic, J. Pluta, N. Porile, J. Porter, A. M. Poskanzer, E. Potrebenikova, D. Prindle, C. Pruneau, J. Putschke, G. Rai, G. Rakness, O. Ravel, R. L. Ray, S. V. Razin, D. Reichhold, J. G. Reid, F. Retiere, A. Ridiger, H. G. Ritter, J. B. Roberts, O. V. Rogachevski, J. L. Romero, A. Rose, C. Roy, V. Rykov, I. Sakrejda, S. Salur, J. Sandweiss, A. C. Saulys, I. Savin, J. Schambach, R. P. Scharenberg, N. Schmitz, L. S. Schroeder, A. Schüttauf, K. Schweda, J. Seger, D. Seliverstov, P. Seyboth, E. Shahaliev, K. E. Shestermanov, S. S. Shimanskii, V. S. Shvetcov, G. Skoro, N. Smirnov, R. Snellings, P. Sorensen, J. Sowinski, H. M. Spinka, B. Srivastava, E. J. Stephenson, R. Stock, A. Stolpovsky, M. Strikhanov, B. Stringfellow, C. Struck, A. A. P. Suaide, E. Sugarbaker, C. Suire, M. Šumbera, B. Surrow, T. J. M. Symons, A. Szanto de Toledo, P. Szarwas, A. Tai, J. Takahashi, A. H. Tang, J. H. Thomas, M. Thompson, V. Tikhomirov, M. Tokarev, M. B. Tonjes, T. A. Trainor, S. Trentalange, R. E. Tribble, V. Trofimov, O. Tsai, T. Ullrich, D. G. Underwood, G. Van Buren, A. M. VanderMolen, I. M. Vasilevski, A. N. Vasiliev, S. E. Vigdor, S. A. Voloshin, F. Wang, H. Ward, J. W. Watson, R. Wells, G. D. Westfall, C. Whitten, Jr., H. Wieman, R. Willson, S. W. Wissink, R. Witt, J. Wood, N. Xu, Z. Xu, A. E. Yakutin, E. Yamamoto, J. Yang, P. Yepes, V. I. Yurevich, Y. V. Zanevski, I. Zborovský, H. Zhang, W. M. Zhang, R. Zoulkarneev, and A. N. Zubarev (STAR Collaboration
Disappearance of back-to-back high hadron correlations in central Au+Au collisions at = 200 GeV
Azimuthal correlations for large transverse momentum charged hadrons have
been measured over a wide pseudo-rapidity range and full azimuth in Au+Au and
p+p collisions at = 200 GeV. The small-angle correlations
observed in p+p collisions and at all centralities of Au+Au collisions are
characteristic of hard-scattering processes already observed in elementary
collisions. A strong back-to-back correlation exists for p+p and peripheral Au
+ Au. In contrast, the back-to-back correlations are reduced considerably in
the most central Au+Au collisions, indicating substantial interaction as the
hard-scattered partons or their fragmentation products traverse the medium.Comment: submitted to Phys. Rev. Let
Evidence from d+Au measurements for final-state suppression of high hadrons in Au+Au collisions at RHIC
We report measurements of single-particle inclusive spectra and two-particle
azimuthal distributions of charged hadrons at high transverse momentum (high
) in minimum bias and central d+Au collisions at =200 GeV.
The inclusive yield is enhanced in d+Au collisions relative to binary-scaled
p+p collisions, while the two-particle azimuthal distributions are very similar
to those observed in p+p collisions. These results demonstrate that the strong
suppression of the inclusive yield and back-to-back correlations at high
previously observed in central Au+Au collisions are due to final-state
interactions with the dense medium generated in such collisions.Comment: Final journal version. Data tables for figures may be downloaded from
the STAR home page: http://www.star.bnl.gov --> Publications --> Access to
STAR published dat
Rapidity and centrality dependence of proton and antiproton production from 197Au + 197Au collisions at √SNN = 130 GeV
We report on the rapidity and centrality dependence of proton and antiproton transverse mass distributions from 197Au + 197Au collisions at sqrt[sNN ]=130 GeV as measured by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). Our results are from the rapidity and transverse momentum range of |y| <0.5 and 0.35< pt <1.00 GeV/c . For both protons and antiprotons, transverse mass distributions become more convex from peripheral to central collisions demonstrating characteristics of collective expansion. The measured rapidity distributions and the mean transverse momenta versus rapidity are flat within |y| <0.5 . Comparisons of our data with results from model calculations indicate that in order to obtain a consistent picture of the proton (antiproton) yields and transverse mass distributions the possibility of prehadronic collective expansion may have to be taken into account
Pion-Xi correlations in Au-Au collisions at STAR
We present pion-Xi correlation analysis in Au-Au collisions at sqrt(s_NN)=
200 GeV and sqrt(s_NN) = 62.4 GeV, performed using the STAR detector at RHIC. A
Xi*(1530) resonance signal is observed for the first time in Au-Au collisions.
Experimental data are compared with theoretical predictions. The strength of
the Xi* peak is reproduced in the correlation function assuming that pions and
Xis emerge from a system in collective expansion.Comment: To appear in the proceedings of 18th Nuclear Physics Division
Conference of the EPS (NPDC18),Prague, 23.8.-29.8. 200
Azimuthal anisotropy of K0s and Lambda prduction at mid-rapidity from Au+Au collisions at root s = 130 GeV
We report STAR results on the azimuthal anisotropy parameter v2 for strange
particles K0S, L and Lbar at midrapidity in Au+Au collisions at sNN = 130 GeV
at RHIC. The value of v2 as a function of transverse momentum of the produced
particles pt and collision centrality is presented for both particles up to pt
3.0 GeV/c. A strong pt dependence in v2 is observed up to 2.0 GeV/c. The v2
measurement is compared with hydrodynamic model calculations. The physics
implications of the pt integrated v2 magnitude as a function of particle mass
are also discussed.Comment: 6 pages, 4 figures, by the STAR collaboratio
Transverse momentum and collision energy dependence of high hadron suppression in Au+Au collisions at ultrarelativistic energies
We report high statistics measurements of inclusive charged hadron production
in Au+Au and p+p collisions at \sqrtsNN=200 GeV. A large, approximately
constant hadron suppression is observed in central Au+Au collisions for
5\lt\pT\lt12 GeV/c. The collision energy dependence of the yields and the
centrality and \pT dependence of the suppression provide stringent constraints
on theoretical models of suppression. Models incorporating initial-state gluon
saturation or partonic energy loss in dense matter are largely consistent with
observations. We observe no evidence of \pT-dependent suppression, which may be
expected from models incorporating jet attentuation in cold nuclear matter or
scattering of fragmentation hadrons.Comment: Final journal version. Data tables for figures may be downloaded from
the STAR home page: http://www.star.bnl.gov --> Publications --> Access to
STAR published dat
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