The Gamow-Teller Resonance in Finite Nuclei in the Relativistic Random Phase Approximation

Gamow-Teller(GT) resonances in finite nuclei are studied in a fully consistent relativistic random phase approximation (RPA) framework. A relativistic form of the Landau-Migdal contact interaction in the spin-isospin channel is adopted. This choice ensures that the GT excitation energy in nuclear matter is correctly reproduced in the non-relativistic limit. The GT response functions of doubly magic nuclei $^{48}$Ca, $^{90}$Zr and $^{208}$Pb are calculated using the parameter set NL3 and $g_0'$=0.6 . It is found that effects related to Dirac sea states account for a reduction of 6-7 % in the GT sum rule.Comment: 9 pages, 1 figur

Real-time motion planning based vibration control of a macro-micro parallel manipulator system for super antenna

A macro-micro manipulator (M3) system, composed of a rigid parallel manipulator serially mounted on a flexible cable suspended parallel manipulator, is used to precisely position the feed source of a super antenna. In order to reduce the impact of mechanical vibrations of the macro manipulator and achieve accurate positioning and orientating of the micro manipulator, a real-time motion planning based vibration control strategy is presented. This strategy comprises: (1) To determine the optimal position and orientation of the cable driven parallel manipulator, the real-time optimization is conducted according to the principle of uniform tension in the six driving cables; (2) Synchronized points and the “judge and wait” technique ensure the continuity and synchrony of the trajectory tracking of the two parallel manipulators; (3) The preadjustment of the micro parallel manipulator minimizes the drastic dynamical coupling as a result of its high-speed manipulation. Experimental results of the field model validate the high precision of the M3 system for super antenna when tracking a circular arc trajectory

A spatial filter and two linear PZT arrays based composite structure imaging method

Aerospace structures make increasing use of composite materials which can generate inner damage easily by outer impact. Thus, the damage and impact monitoring of composite structures is an important research topic of structural health monitoring (SHM) technology. Among existing SHM methods, piezoelectric transducer (PZT) array and Lamb wave based structural imaging method has become an effective approach to monitor the damage and impact. However, the anisotropic feature of the composite structures makes it difficult to achieve accurate damage and impact localization which are dependent on Lamb wave group velocity. In recent years, a linear PZT array and spatial filter based damage imaging method has been developed. But this method is only applied to damage monitoring at the current stage and it also needs the Lamb wave group velocity to fulfill the damage localization. In this paper, a spatial filter and two linear PZT arrays based structural imaging method for composite structures is proposed. With this method, an acoustic source angle-time image for each linear PZT array can be obtained by using the spatial filter technique. Then, it is transformed to an acoustic source probability-angle image of the linear PZT array. Based on the probability-angle image, the angle of the acoustic source relative to the linear PZT array can be estimated accurately. By fusing the two probability-angle images of the two linear PZT arrays, the acoustic source can be localized accurately without using the Lamb wave group velocity. Damage and impact can be both considered to be acoustic source on composite structure. Thus, they can be localized easily and accurately by using the proposed structural imaging method. This method is validated on a carbon fiber composite laminate plate, including damage imaging and impact imaging. The imaging and localization results are in good agreement with the actual damage and impact positions, and the maximum localization error is no more than 1 cm

Impact of high-frequency pumping on anomalous finite-size effects in three-dimensional topological insulators

Lowering of the thickness of a thin-film three-dimensional topological insulator down to a few nanometers results in the gap opening in the spectrum of topologically protected two-dimensional surface states. This phenomenon, which is referred to as the anomalous finite-size effect, originates from hybridization between the states propagating along the opposite boundaries. In this work, we consider a bismuth-based topological insulator and show how the coupling to an intense high-frequency linearly polarized pumping can further be used to manipulate the value of a gap. We address this effect within recently proposed Brillouin-Wigner perturbation theory that allows us to map a time-dependent problem into a stationary one. Our analysis reveals that both the gap and the components of the group velocity of the surface states can be tuned in a controllable fashion by adjusting the intensity of the driving field within an experimentally accessible range and demonstrate the effect of light-induced band inversion in the spectrum of the surface states for high enough values of the pump.Comment: 6 pages, 3 figure

Cerebellar Functional Parcellation Using Sparse Dictionary Learning Clustering

10.3389/fnins.2016.00188Frontiers in neuroscience10188GUSTO (Growing up towards Healthy Outcomes

A Novel Large Moment Antiferromagnetic Order in K0.8Fe1.6Se2 Superconductor

The discovery of cuprate high Tc superconductors has inspired searching for unconventional su- perconductors in magnetic materials. A successful recipe has been to suppress long-range order in a magnetic parent compound by doping or high pressure to drive the material towards a quantum critical point, which is replicated in recent discovery of iron-based high TC superconductors. The long-range magnetic order coexisting with superconductivity has either a small magnetic moment or low ordering temperature in all previously established examples. Here we report an exception to this rule in the recently discovered potassium iron selenide. The superconducting composition is identified as the iron vacancy ordered K0.8Fe1.6Se2 with Tc above 30 K. A novel large moment 3.31 {\mu}B/Fe antiferromagnetic order which conforms to the tetragonal crystal symmetry has the unprecedentedly high an ordering temperature TN = 559 K for a bulk superconductor. Staggeredly polarized electronic density of states thus is suspected, which would stimulate further investigation into superconductivity in a strong spin-exchange field under new circumstance.Comment: 5 figures, 5 pages, and 2 tables in pdf which arXiv.com cannot tak