243,761 research outputs found
Anisotropy of Imbalanced Alfvenic Turbulence in Fast Solar Wind
We present the first measurement of the scale-dependent power anisotropy of
Elsasser variables in imbalanced fast solar wind turbulence. The dominant
Elsasser mode is isotropic at lower spacecraft frequencies but becomes
increasingly anisotropic at higher frequencies. The sub-dominant mode is
anisotropic throughout, but in a scale-independent way (at higher frequencies).
There are two distinct subranges exhibiting different scalings within what is
normally considered the inertial range. The low Alfven ratio and shallow
scaling of the sub-dominant Elsasser mode suggest an interpretation of the
observed discrepancy between the velocity and magnetic field scalings. The
total energy is dominated by the latter. These results do not appear to be
fully explained by any of the current theories of incompressible imbalanced MHD
turbulence.Comment: 5 pages, 2 figure
Experimental investigation of the asymmetric spectroscopic characteristics of electron- and hole-doped cuprates
Quasiparticle tunneling spectroscopic studies of electron- (n-type) and hole-doped (p-type) cuprates reveal that the pairing symmetry, pseudogap phenomenon and spatial homogeneity of the superconducting order parameter are all non-universal. We compare our studies of p-type YBa2Cu3O7-delta and n-type infinite-layer Sr(0.9)Ln(0.1)CuO(2) (Ln = La, Gd) systems with results from p-type Bi2Sr2CaCu2Ox and n-type one-layer Nd1.85Ce0.15CuO4 cuprates, and attribute various non-universal behavior to different competing orders in p-type and n-type cuprates
Anisotropy of Alfv\'enic Turbulence in the Solar Wind and Numerical Simulations
We investigate the anisotropy of Alfv\'enic turbulence in the inertial range
of slow solar wind and in both driven and decaying reduced magnetohydrodynamic
simulations. A direct comparison is made by measuring the anisotropic
second-order structure functions in both data sets. In the solar wind, the
perpendicular spectral index of the magnetic field is close to -5/3. In the
forced simulation, it is close to -5/3 for the velocity and -3/2 for the
magnetic field. In the decaying simulation, it is -5/3 for both fields. The
spectral index becomes steeper at small angles to the local magnetic field
direction in all cases. We also show that when using the global rather than
local mean field, the anisotropic scaling of the simulations cannot always be
properly measured.Comment: 9 pages, 8 figure
Transformation media that rotate electromagnetic fields
We suggest a way to manipulate electromagnetic wave by introducing a rotation
mapping of coordinates that can be realized by a specific transformation of
permittivity and permeability of a shell surrounding an enclosed domain. Inside
the enclosed domain, the information from outside will appear as if it comes
from a different angle. Numerical simulations were performed to illustrate
these properties.Comment: 5 pages, 3 figure
The Electronic States of Two Oppositely doped Mott Insulators Bilayers
We study the effect of Coulomb interaction between two oppositely doped
low-dimensional tJ model systems. We exactly show that, in the one-dimensional
case, an arbitrarily weak interaction leads to the formation of charge neutral
electron-hole pairs. We then use two different mean-field theories to address
the two-dimensional case, where inter-layer excitons also form and condense. We
propose that this results in new features which have no analog in single
layers, such as the emergence of an insulating spin liquid phase. Our simple
bilayer model might have relevance to the physics of doped Mott insulator
interfaces and of the new four layer Ba2CaCu4O8 compound.Comment: 4 pages, 1 figur
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Studying RFID adoption by SMES in the Taiwanese IT industry
With the advent of Radio Frequency Identification (RFID), organisations have the opportunity to rethink how their organisation will operate and integrate in the supply chain. Especially for Small to Medium Sized Enterprises (SMEs), that they have limited resources adopting such an innovative technology (i.e. RFID) can be daunting. Literature indicates that SMEs that deal with implementation have so far only a few guidelines regarding specific opportunities and risks. This research is therefore trying to fill the gap by employing Exploratory Factor Analysis (EFA) techniques and utilising a questionnaire survey with the aim of exploring the factors that affect SMEsâ RFID adoption in the Taiwan Information Technology (IT) manufacturing industry. In doing so, the adoption factors which are classified into 3 different adopters categories named ready adopter (cost and management), initiator adopter (competitiveness and process efficiency) and unprepared adopter (IT management difficulties, IT implementation difficulties and cost of implementation) using EFA technique. A SMEs RFID adoption model is then proposed. It is anticipated that the findings of this research will not only enhance the research in RFID adoption in SMEs, but can also act as a reference for practitioners in the industry and researchers in the academic field
Simple choreographies of the planar Newtonian -body Problem
In the -body problem, a simple choreography is a periodic solution, where
all masses chase each other on a single loop. In this paper we prove that for
the planar Newtonian -body problem with equal masses, , there are
at least different main simple choreographies. This
confirms a conjecture given by Chenciner and etc. in \cite{CGMS02}.Comment: 31pages, 6 figures. Refinements in notations and proof
Investigating the Physical Origin of Unconventional Low-Energy Excitations and Pseudogap Phenomena in Cuprate Superconductors
We investigate the physical origin of unconventional low-energy excitations
in cuprate superconductors by considering the effect of coexisting competing
orders (CO) and superconductivity (SC) and of quantum fluctuations and other
bosonic modes on the low-energy charge excitation spectra. By incorporating
both SC and CO in the bare Green's function and quantum phase fluctuations in
the self-energy, we can consistently account for various empirical findings in
both the hole- and electron-type cuprates, including the excess subgap
quasiparticle density of states, ``dichotomy'' in the fluctuation-renormalized
quasiparticle spectral density in momentum space, and the occurrence and
magnitude of a low-energy pseudogap being dependent on the relative gap
strength of CO and SC. Comparing these calculated results with experiments of
ours and others, we suggest that there are two energy scales associated with
the pseudogap phenomena, with the high-energy pseudogap probably of magnetic
origin and the low-energy pseudogap associated with competing orders.Comment: 10 pages, 5 figures. Invited paper for the 2006 Taiwan International
Conference on Superconductivity. Correspondence author: Nai-Chang Yeh
(e-mail: [email protected]
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