479 research outputs found
The Non-coplanar 6-Li(p,pd)4-He Reaction at 120 and 200 MeV
This research was sponsored by the National Science Foundation Grant NSF PHy 87-1440
Effects of Mn and Ti doping on superconductivity and charge ordering in NaxCoO2 system
The superconductivity in Na0.3Co1-xMxO2.1.3H2O and the charge ordering in
Na0.5Co1-xMxO2 have been investigated for M = Mn and Ti substituting for Co. We
have first successfully synthesized the single-phase Na0.7Co1-xMxO2(M= Mn and
Ti) materials with 0 < = x < = 0.1, then we obtained Na0.5Co1-xMxO2 (0 < = x <
= 0.1, M = Mn and Ti) by Na deintercalation and Na0.3Co1-xMxO2.1.3H2O (0 < = x
< = 0.1, M = Mn and Ti) by an additional water intercalations. X-ray
diffraction measurements revealed that all samples are single-phase materials,
their lattice parameters depend systematically on the Ti and Mn contents.
Measurements of physical properties indicate that the superconductivity in
Na0.3Co1-xMxO2.1.3H2O is suppressed evidently by Co-site doping and killed at x
= 0.02 for Mn doping and x = 0.01 for Ti doping. Charge ordering and magnetic
properties in Na0.5Co1-xMxO2 were also influenced by M-atom doping.Comment: 22 pages, 3 tables, and 6 figure
Quantum information processing with superconducting qubits in a microwave field
We investigate the quantum dynamics of a Cooper-pair box with a
superconducting loop in the presence of a nonclassical microwave field. We
demonstrate the existence of Rabi oscillations for both single- and
multi-photon processes and, moreover, we propose a new quantum computing scheme
(including one-bit and conditional two-bit gates) based on Josephson qubits
coupled through microwaves.Comment: 7 pages, 1 figur
Experimental Study on Seismic Behavior of Cluster-Reinforced Precast Concrete Columns with Grouting-Anchor Connections
The prefabricated residential buildings have become one of the most dominating construction methods in the modern construction industry. The seismic behavior of prefabricated components is crucial in the limit state design of the precast structure. This paper investigates the seismic behavior of a new type precast concrete column that has clustered steel reinforcement with grouting connection. Quasi-static tests are carried out on three cast-in-situ columns and seven precast columns. Axial compression ratio, lap length and lap space are the main variables considered. The failure process, hysteresis curve, skeleton curve, stiffness degradation, displacement ductility and energy dissipation are elaborated. The experimental results show that the precast columns with cluster reinforcement have similar seismic behavior to the cast-in-situ columns. Reducing the axial pressure can improve the ductility and energy consumption performance of the cluster-reinforced columns and exert its ductility to improve its seismic performance. During the assembly, a moderate increase in lap length can improve the seismic behavior of precast columns, whereas the lap space has an insignificant effect on the seismic behavior which indicates that the lap space is not an important factor during construction. The research outcome can serve as a reference for further development and application of precast structures
EGAM Induced by Energetic-electrons and Nonlinear Interactions among EGAM, BAEs and Tearing Modes in a Toroidal Plasma
In this letter, it is reported that the first experimental results are
associated with the GAM induced by energetic electrons (eEGAM) in HL-2A Ohmic
plasma. The energetic-electrons are generated by parallel electric fields
during magnetic reconnection associated with tearing mode (TM). The eEGAM
localizes in the core plasma, i.e. in the vicinity of q=2 surface, and is very
different from one excited by the drift-wave turbulence in the edge plasma. The
analysis indicated that the eEGAM is provided with the magnetic components,
whose intensities depend on the poloidal angles, and its mode numbers are
jm/nj=2/0. Further, there exist intense nonlinear interactions among eEGAM,
BAEs and strong tearing modes (TMs). These new findings shed light on the
underlying physics mechanism for the excitation of the low frequency (LF)
Alfv\'enic and acoustic uctuations.Comment: 5 pages,4 figure
Structural Phase Transitions and Sodium Ordering in Na0.5CoO2: a Combined Electron Diffraction and Raman Spectroscopy Study
The nonstoichiometric NaxCoO2 system exhibits extraordinary physical
properties that correlate with temperature and Na concentration in its layered
lattice without evident long-range structure modification when conventional
crystallographic techniques are applied. For instance, Na0.7CoO2, a
thermodynamically stable phase, shows large thermoelectric power;
water-intercalated Na0.33CoO2.1.3H2O is a newly discovered superconductor with
Tc ~ 4K, and Na0.5CoO2 exhibits an unexpected charge ordering transition at
around Tco ~ 55 K. Recent studies suggest that the transport and magnetic
properties in the NaxCoO2 system strongly depend on the charge carrier density
and local structural properties. Here we report a combined variable temperature
transmission electron microscopy and Raman scattering investigation on
structural transformations in Na0.5CoO2 single crystals. A series of structural
phase transitions in the temperature range from 80 K to 1000 K are directly
identified and the observed superstructures and modulated phases can be
interpreted by Na-ordering. The Raman scattering measurements reveal phase
separation and a systematic evolution of active modes along with phase
transitions. Our work demonstrates that the high mobility and ordering of
sodium cations among the CoO2 layers are a key factor for the presence of
complex structural properties in NaxCoO2 materials, and also demonstrate that
the combination of electron diffraction and Raman spectroscopy measurements is
an efficient way for studying the cation ordering and phase transitions in
related systems.Comment: 22 pages, 5 figure
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