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Search Results: 1 - 10 of 244149 matches for " L. Xiao "
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GSH 90-28-17: a Possible Old Supernova Remnant
L. Xiao,M. Zhu
Physics , 2013, DOI: 10.1093/mnras/stt2258
Abstract: GSH 90-28-17 is a high-latitude galactic HI supershell, identified in the HI supershell catalogs with a velocity of $v_{lsr}\sim-17$ \kms. We used the new Arecibo GALFA-HI survey data which have much higher resolution and sensitivity than what were previously available to re-examine the properties of the supershell. We derived a new distance of 400 pc for GSH 90-28-17 and suggested that it is related to the Lac OB1 association. The radius of GSH 90-28-17 is 66.0$\pm$3.5 pc. The HI mass of the shell is (3.1$\pm0.1)\times10^{4}$ M$_{\odot}$. It has an age of $\sim4.5$ Myr and a total kinetic energy of (8.2$\pm0.3)\times10^{48}$ ergs. We extracted radio continuum data for the GSH 90-28-17 region from the 408 MHz all-sky Survey and Bonn 1420 MHz survey, and filtered the diffuse background Galactic emission. A radio loop-like ridge is found to be associated with the HI shell at both frequencies, and shows a nonthermal origin with a TT-plot index of $\alpha$=-1.35$\pm$0.69. In addition, the pulsar J2307+2225 with a similar distance is found in the shell region. We conclude that GSH 90-28-17 is probably an old, type II supernova remnant in the solar neighborhood.
Radio perspectives on the Monoceros SNR G205.5+0.5
L. Xiao,M. Zhu
Physics , 2012, DOI: 10.1051/0004-6361/201218938
Abstract: The Monoceros Loop (SNR G205.5+0.5) is a large shell-type supernova remnant located in the Rosette Complex region. It was suggested to be interacting with the Rosette Nebula. We aim to re-examine the radio spectral index and its spatial variation over the Monoceros SNR, and study its properties of evolution within the complex interstellar medium. We extracted radio continuum data for the Monoceros complex region from the Effelsberg 21 cm and 11 cm surveys and the Urumqi 6 cm polarization survey. We used the new Arecibo GALFA-HI survey data with much higher resolution and sensitivity than that previously available to identify the HI shell related with the SNR. Multi-wavelengths data are included to investigate the properties of the SNR. The spectral index $\alpha$ ($S_{\nu}\propto\nu^{\alpha}$) averaged over the SNR is $-0.41 \pm$0.16. The TT-plots and the distribution of $\alpha$ over the SNR show spatial variations which steepen towards the inner western filamentary shell. Polarized emission is prominent on the western filamentary shell region. The RM there is estimated to be about 30$\pm$77n rad m$^{-2}$, where the n=1 solution is preferred, and the magnetic field has a strength of about 9.5 $\mu$G. From the HI channel maps, further evidence is provided for an interaction between the Monoceros SNR and the Rosette Nebula. We identify partial neutral hydrogen shell structures in the northwestern region at LSR velocities of +15 km s$^{-1}$ circumscribing the continuum emission. The HI shell has swept up a mass of about 4000 M$_{\odot}$ for a distance of 1.6 kpc. The western HI shell, well associated with the dust mission, is found to lie outside of the radio shell. We suggest that the Monoceros SNR is evolving within a cavity blown-out by the progenitor, and has triggered part of the star formation in the Rosette Nebula.
Fetching marked items from an unsorted database in NMR ensemble computing
L. Xiao,G. L. Long
Physics , 2001, DOI: 10.1103/PhysRevA.66.052320
Abstract: Searching a marked item or several marked items from an unsorted database is a very difficult mathematical problem. Using classical computer, it requires $O(N=2^n)$ steps to find the target. Using a quantum computer, Grover's algorithm uses $O(\sqrt{N=2^n})$ steps. In NMR ensemble computing, Brushweiler's algorithm uses $\log N$ steps. In this Letter, we propose an algorithm that fetches marked items in an unsorted database directly. It requires only a single query. It can find a single marked item or multiple number of items.
Methods for molecular dynamics with nonadiabatic transitions
D. F. Coker,L. Xiao
Physics , 1994, DOI: 10.1063/1.469428
Abstract: We show how the dynamically nonlocal formulation of classical nuclear motion in the presence of quantal electronic transitions presented many years ago by Pechukas can be localized in time using time dependent perturbation theory to give an impulsive force which acts when trajectories hop between electronic surfaces. The action of this impulsive force is completely equivalent to adjusting the nuclear velocities in the direction of the nonadiabatic coupling vector so as to conserve energy, a procedure which is widely used in surface hopping trajectory methods. This is the first time the precise connection between these two formulations of the nonadiabatic dynamics problem has been considered. We also demonstrate that the stationary phase approximation to the reduced propagator at the heart of Pechukas' theory is not unitary due to its neglect of nonstationary paths. As such mixed quantum-classical evolution schemes based on this approximation are not norm conserving and in general must fail to give the correct branching between different competing electronic states. Tully's phase coherent, fewest switches branching algorithm is guaranteed to conserve the norm. The branching between different alternatives predicted by this approach, however, may be inaccurate, due to use of the approximate local dynamics. We explore the relative merits of these different approximations using Tully's 1D two state example scattering problems for which numerically exact results are easily obtained.
Dynamical spin-spin coupling of quantum dots
Vahram L. Grigoryan,Jiang Xiao
Physics , 2013, DOI: 10.1209/0295-5075/104/17008
Abstract: We carried out a nested Schrieffer-Wolff transformation of an Anderson two-impurity Hamiltonian to study the spin-spin coupling between two dynamical quantum dots under the influence of rotating transverse magnetic field. As a result of the rotating field, we predict a novel Ising type spin-spin coupling mechanism between quantum dots, whose strength is tunable via the magnitude of the rotating field. The strength of the new coupling could be comparable to the strength of the RKKY coupling. The dynamical coupling with the intristic RKKY coupling enables to construct a four level system of maximally entangled Bell states in a controllable manner.
Optimal Sensor Location Design for Reliable Fault Detection in Presence of False Alarms
Fan Yang,Deyun Xiao,Sirish L. Shah
Sensors , 2009, DOI: 10.3390/s91108579
Abstract: To improve fault detection reliability, sensor location should be designed according to an optimization criterion with constraints imposed by issues of detectability and identifiability. Reliability requires the minimization of undetectability and false alarm probability due to random factors on sensor readings, which is not only related with sensor readings but also affected by fault propagation. This paper introduces the reliability criteria expression based on the missed/false alarm probability of each sensor and system topology or connectivity derived from the directed graph. The algorithm for the optimization problem is presented as a heuristic procedure. Finally, a boiler system is illustrated using the proposed method.
Calculations of ${\cal O}(p^6)$ Resonance Coupling Constants in the Scalar Sector of the ENJL Model
Su, M. X.;Xiao, L. Y.
High Energy Physics - Phenomenology , 2007, DOI: 10.1088/0253-6102/49/5/41
Abstract: We derive the scalar resonance coupling constants of resonance chiral theory from the Extended Nambu Jona-Lasinio model by using heat-kernel expansion.
Coupling phases and amplitudes of minor constituents with temperature perturbations in the lower thermosphere
Y. W. Chen,F. L. Xiao
Annales Geophysicae (ANGEO) , 2003,
Abstract: Based on the linearized theory of atmospheric gravity waves (AGW) and considering the effects of temperature perturbation on the chemical rate coefficients, the formulae of coupling relations between nj/nj and T'/T driven by AGW (nj and T denote the background quantities) are described, the coupling phases and amplitudes of minor constituents O3, NO, H, OH, and O are analyzed in detail for the mesopause (86 km) and just upside of the O layer (100 km) at daytime. A general principle is outlined: the coupling phases are strongly dependent on density scale heights and perturbation scales, while the amplitudes are little affected by these two factors. A criterion to distinguish the coupling behaviour is given: when the minor constituent number density scale height Hj satisfies 1-γHm/Hj>0 (Hm denotes the scale height of the major constituent), the dynamical perturbation process always keeps the nj/nj in phase with T'/T, i.e. keeps the nj/nj in antiphase with that of the major constituent. The results obtained indicate that both the temperature dependence of reaction rate coefficients and the profile slopes of the O distribution may have a major influence on the behaviour of the coupling relations.
A new species of Agnathosia Amsel, 1954 from China (Lepidoptera: Tineidae, Meessiinae)
Y. L. Xiao,H. H. Li
SHILAP Revista de Lepidopterología , 2011,
Abstract: Se describe una nueva especie, a saber Agnathosia obisagittalis Xiao & Li, sp. n., basándose en ejemplares recogidos en China. Se proveen fotografías del adulto y la genitalia del macho, así como un dibujo de la venación.
A systematic study on the genus Crypsithyris Meyrick, 1907 from China (Lepidoptera: Tineidae)
Y. L. Xiao,H. H. Li
SHILAP Revista de Lepidopterología , 2005,
Abstract: En este trabajo se tratan cinco especies del género Crypsithyris Meyrick, 1907 de China, incluyendo tres especies nuevas para la ciencia (Crypsithyris introflexa Xiao & Li, sp. n., Crypsithyris obtusangula Xiao & Li, sp. n. y Crypsithris hebeiensis Xiao & Li, sp. n.) y una especie (Crypsithris spelaea Meyrick) se cita nueva para China. Se dan las fotografías de los adultos, de la venación alar y de la estructura genital de las nuevas especies. Se dan claves de las especies chinas.
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