28,735 research outputs found
Supersolid phase in spin dimer XXZ systems under magnetic field
Using quantum Monte Carlo method, we study, under external magnetic fields,
the ground state phase diagram of the two-dimensional spin =1/2 dimer model
with an anisotropic intra-plane antiferromagnetic coupling. With the anisotropy
, a supersolid phase characterized by a non-uniform
bose condensate density that breaks translational symmetry is found. The rich
phase diagram also contains a checkerboard solid and two different types of
superfluid phase formed by and spin triplets, with finite
staggered magnetization in z-axis and in-plane direction, respectively. As we
show, the model can be realized as a consequence of including the next nearest
neighbor coupling among dimers and our results suggest that spin dimer systems
may be an ideal model system to study the supersolid phase.Comment: 4 pages, 5 figure
Idealized Slab Plasma approach for the study of Warm Dense Matter
Recently, warm dense matter (WDM) has emerged as an interdisciplinary field
that draws increasing interest in plasma physics, condensed matter physics,
high pressure science, astrophysics, inertial confinement fusion, as well as
materials science under extreme conditions. To allow the study of well-defined
WDM states, we have introduced the concept of idealized-slab plasmas that can
be realized in the laboratory via (i) the isochoric heating of a solid and (ii)
the propagation of a shock wave in a solid. The application of this concept
provides new means for probing the dynamic conductivity, equation of state,
ionization and opacity. These approaches are presented here using results
derived from first-principles (density-functional type) theory, Thomas-Fermi
type theory, and numerical simulations.Comment: 37 pages, 21 figures, available, pdf file only. To appear in: Laser
and Particle beams. To appear more or less in this form in Laser and Particle
beam
Edge states in Open Antiferromagnetic Heisenberg Chains
In this letter we report our results in investigating edge effects of open
antiferromagnetic Heisenberg spin chains with spin magnitudes
using the density-matrix renormalization group (DMRG) method initiated by
White. For integer spin chains, we find that edge states with spin magnitude
exist, in agreement with Valence-Bond-Solid model picture. For
half-integer spin chains, we find that no edge states exist for spin
chain, but edge state exists in spin chain with , in
agreement with previous conjecture by Ng. Strong finite size effects associated
with spin dimmerization in half-integer spin chains will also be discussed.Comment: 4 pages, RevTeX 3.0, 5 figures in a separate uuencoded postscript
file. Replaced once to enlarge the acknowlegement
Experimental study of multiple cracks detection utilizing a probabilistic approach
This paper studies the possibility of using measured transient vibration data in the detection of multiple cracks on beams by following the Bayesian probabilistic framework. The proposed method adopts different classes of models in modelling a beam with different numbers of cracks. The number of cracks on the beam can then be identified by calculating the probability of a model class conditional on a given set of measured transient vibration data. By following the Bayesian probabilistic framework, the posterior probability density functions (PDFs) for a set of crack parameters, such as the crack locations and the corresponding extents, can be calculated. The PDFs allow engineers to quantify the uncertainties associated with the results of crack detection. The paper reports not only the theoretical developed but also the experimental verification of the proposed method
Hydration temperature rise and thermal stresses induced in segment-on-pier of prestressed concrete box girder bridge
The heat generation from chemical reactions of hardening concrete causes temperature rise and thermal expansion. When the concrete temperature eventually cools down to the ambient, thermal contraction would result. If the tendency of volume change and associated thermal movement are restrained, thermal stresses would be induced and this would lead to early thermal cracking. The issue of thermal cracking should be duly considered in mass concrete construction. Regarding concrete bridge construction, the piles, pile caps, bridge piers, crosshead girders, and bridge diaphragms are typical examples of mass concrete elements. A bridge project in real-life is selected for study in this paper, with focus on the segment-on-pier accommodating the diaphragm of prestressed concrete girder deck. The segment was instrumented to measure its actual early age temperature rise on site. Finite element simulation and analysis was conducted to evaluate the time variations of temperature distributions and thermal stresses induced in the bridge segment. The risk of thermal cracking can be indicated by the measurement and analysis results. The techniques employed in this study are useful for planning of temperature control measures in similar projects
Depression in Sj\uf6gren\u27s syndrome mediates the relationship between pain, fatigue, sleepiness, and overall quality of life
Time domain add-drop multiplexing scheme enhanced using a saw-tooth pulse shaper
We experimentally demonstrate the use of saw-tooth optical pulses, which are shaped using a fiber Bragg grating, to achieve robust and high performance time-domain add-drop multiplexing in a scheme based on cross-phase (XPM) modulation in an optical fiber, with subsequent offset filtering. As compared to the use of more conventional pulse shapes, such as Gaussian pulses of a similar pulse width, the purpose-shaped saw-tooth pulses allow higher extinction ratios for the add and drop windows and significant improvements in the receiver sensitivity for the dropped and added channels
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