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Search Results: 1 - 10 of 448522 matches for " J. L. Borne "
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Chandra Observations of Arp 220: The Nuclear Source
D. L. Clements,J. C. McDowell,S. Shaked,A. C. Baker,K. Borne,L. Colina,S. Lamb,C. Mundell
Physics , 2002, DOI: 10.1086/344439
Abstract: We present the first results from 60ks of observations of Arp 220 using the ACIS-S instrument on Chandra. We report the detection of several sources near the galaxy's nucleus, including a point source with a hard spectrum that is coincident with the western radio nucleus B. This point source is mildly absorbed (N_H ~ 3 x 10^22 cm^-2) and has an estimated luminosity of 4 x 10^40 erg/s. In addition, a fainter source may coincide with the eastern nucleus A. Extended hard X-ray emission in the vicinity raises the total estimated nuclear 2-10 keV X-ray luminosity to 1.2 x 10^41 erg/s, but we cannot rule out a hidden AGN behind columns exceeding 5 x 10^24 cm^-2. We also detect a peak of soft X-ray emission to the west of the nucleus, and a hard point source 2.5 kpc from the nucleus with a luminosity of 6 x 10^39 erg/s.
Chandra Observations of Extended X-ray Emission in Arp 220
J. C. McDowell,D. L. Clements,S. A. Lamb,S. Shaked,N. C. Hearn,L. Colina,C. Mundell,K. Borne,A. C. Baker,S. Arribas
Physics , 2003, DOI: 10.1086/375289
Abstract: We resolve the extended X-ray emission from the prototypical ultraluminous infrared galaxy Arp 220. Extended, faint edge-brightened, soft X-ray lobes outside the optical galaxy are observed to a distance of 10 to 15 kpc on each side of the nuclear region. Bright plumes inside the optical isophotes coincide with the optical line emission and extend 11 kpc from end to end across the nucleus. The data for the plumes cannot be fit by a single temperature plasma, and display a range of temperatures from 0.2 to 1 keV. The plumes emerge from bright, diffuse circumnuclear emission in the inner 3 kpc centered on the Halpha peak, which is displaced from the radio nuclei. There is a close morphological correspondence between the Halpha and soft X-ray emission on all spatial scales. We interpret the plumes as a starburst-driven superwind, and discuss two interpretations of the emission from the lobes in the context of simulations of the merger dynamics of Arp 220.
Integral Field Spectroscopy of Mrk 273: Mapping 10^3 km/s Gas Flows and an Off-Nucleus Seyfert 2 Nebula
L. Colina,S. Arribas,K. Borne
Physics , 1999, DOI: 10.1086/312389
Abstract: Integral field optical spectroscopy with the INTEGRAL fiber-based systemis used to map the extended ionized regions and gas flows in Mrk 273, one of the closest Ultraluminous Infrared galaxies (ULIRGs). The Hbeta and [OIII]5007 maps show the presence of two distinct regions separated by 4'' (3.1 kpc) along position angle (PA) 240. The northeastern region coincides with the optical nucleus of the galaxy and shows the spectral characteristics of LINERs. The southwestern region is dominated by [OIII] emission and is classified as a Seyfert 2. Therefore, in the optical, Mrk 273 is an ultraluminous infrared galaxy with a LINER nucleus and an extended off-nucleus Seyfert 2 nebula. The kinematics of the [OIII] ionized gas shows (i) the presence of highly disturbed gas in the regions around the LINER nucleus, (ii) a high-velocity gas flow with a peak-to-peak amplitude of 2.4 x 10^3 km/s, and (iii) quiescent gas in the outer regions (at 3 kpc). We hypothesize that the high-velocity flow is the starburst-driven superwind generated in an optically obscured nuclear starburst, and that the quiescent gas is directly ionized by a nuclear source, like the ionization cones typically seen in Seyfert galaxies.
A generalized regular form for multivariable sliding mode control
W. Perruquetti,J. P. Richard,P. Borne
Mathematical Problems in Engineering , 2001, DOI: 10.1155/s1024123x01001508
Abstract: The paper shows how to compute a diffeomorphic state space transformation in order to put the initial mutivariable nonlinear model into an appropriate regular form. This form is an extension of the one proposed by Lukyanov and Utkin [9], and constitutes a guidance for a “natural” choice of the sliding surface. Then stabilization is achieved via a sliding mode strategy. In order to overcome the chattering phenomenon, a new nonlinear gain is introduced.
Lyapunov analysis of sliding motions: Application to bounded control
Perruquetti W.,Richard J. P.,Borne P.
Mathematical Problems in Engineering , 1997,
Abstract: The results concern the fundamental problem of Lyapunov analysis of sliding motions. It consist first to estimate the useful part of the sliding surface (the so-called “sliding domain”) and second to estimate the useful part of the state domain that is the domain of all initial conditions for which the corresponding solutions converge to the sliding domain. The application of such results concern the design of a realistic bounded control. Several examples are exposed in order to illustrate the obtained results.
Feedback control of time-delay systems with bounded control and state
Dambrine M.,Richard J. P.,Borne P.
Mathematical Problems in Engineering , 1995,
Abstract: This paper is concerned with the problem of stabilizing linear time-delay systems under state and control linear constraints. For this, necessary and sufficient conditions for a given non-symmetrical polyhedral set to be positively invariant are obtained. Then existence conditions of linear state feedback control law respecting the constraints are established, and a procedure is given in order to calculate such a controller. The paper concerns memoryless controlled systems but the results can be applied to cases of delayed controlled systems. An example is given.
Lyapunov analysis of sliding motions: Application to bounded control
W. Perruquetti,J. P. Richard,P. Borne
Mathematical Problems in Engineering , 1996, DOI: 10.1155/s1024123x9700046x
Abstract:
A generalized regular form for multivariable sliding mode control
Perruquetti W.,Richard J. P.,Borne P.
Mathematical Problems in Engineering , 2001,
Abstract: The paper shows how to compute a diffeomorphic state space transformation in order to put the initial mutivariable nonlinear model into an appropriate regular form . This form is an extension of the one proposed by Lukyanov and Utkin [9], and constitutes a guidance for a “natural” choice of the sliding surface. Then stabilization is achieved via a sliding mode strategy. In order to overcome the chattering phenomenon, a new nonlinear gain is introduced.
Feedback control of time-delay systems with bounded control and state
M. Dambrine,J. P. Richard,P. Borne
Mathematical Problems in Engineering , 1995, DOI: 10.1155/s1024123x95000081
Abstract:
Specific heat across the superconducting dome in the cuprates
A. J. H. Borne,J. P. Carbotte,E. J. Nicol
Physics , 2010, DOI: 10.1103/PhysRevB.82.094523
Abstract: The specific heat of the superconducting cuprates is calculated over the entire phase diagram. A d-wave BCS approach based on the large Fermi surface of Fermi liquid and band structure theory provides a good description of the overdoped region. At underdoping it is essential to include the emergence of a second energy scale, the pseudogap and its associated Gutzwiller factor, which accounts for a reduction in the coherent piece of the electronic Green's function due to increased correlations as the Mott insulating state is approached. In agreement with experiment, we find that the slope of the linear in T dependence of the low temperature specific heat rapidly increases above optimum doping while it is nearly constant below optimum. Our theoretical calculations also agree with recent data on Bi$_2$Sr$_{2-\rm x}$La$_{\rm x}$CuO$_{6+\delta}$ for which the normal state is accessed through the application of a large magnetic field. A quantum critical point is located at a doping slightly below optimum.
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