2,594 research outputs found
MIMO nonlinear PID predictive controller
A class of nonlinear generalised predictive controllers (NGPC) is derived for multi-input multi-output (MIMO) nonlinear systems with offset or steady-state response error. The MIMO composite controller consists of an optimal NGPC and a nonlinear disturbance observer. The design of the nonlinear disturbance observer to estimate the offset is particularly simple, as is the associated proof of overall nonlinear closed-loop system stability. Moreover, the transient error response of the disturbance observer can be arbitrarily specified by simple design parameters. Very satisfactory performance of the proposed MIMO nonlinear predictive controller is demonstrated for a three-link nonlinear robotic manipulator example
Digital image correlation approach to cracking and decohesion in a brittle coating/ductile substrate system
By using a digital image correlation technique, the full/local field strain in a brittle coating/ductile substrate system during tension has been successfully monitored. One of the most important experimental results indicates that the distribution of interfacial shear stress in the segmented coating is antisymmetric about the center, which clarifies several controversial assumptions introduced in theoretical models. Two key mechanical properties of thermal barrier coatings, fracture strength in coating and interfacial adhesion strength, were determined as 35.0 ± 4.6 and 14.1 ± 3.2 MPa, respectively, which are consistent with available experimental data
Preparation of spin squeezed atomic states by optical phase shift measurement
In this paper we present a state vector analysis of the generation of atomic
spin squeezing by measurement of an optical phase shift. The frequency
resolution is improved when a spin squeezed sample is used for spectroscopy in
place of an uncorrelated sample. When light is transmitted through an atomic
sample some photons will be scattered out of the incident beam, and this has a
destructive effect on the squeezing. We present quantitative studies for three
limiting cases: the case of a sample of atoms of size smaller than the optical
wavelength, the case of a large dilute sample and the case of a large dense
sample.Comment: 18 page
Impurity state in Haldane gap for S=1 Heisenberg antiferromagnetic chain with bond doping
Using a new impurity density matrix renormalization group scheme, we
establish a reliable picture of how the low lying energy levels of a
Heisenberg antiferromagnetic chain change {\it quantitatively} upon bond
doping. A new impurity state gradually occurs in the Haldane gap as ,
while it appears only if with as . The
system is non-perturbative as . This explains the
appearance of a new state in the Haldane gap in a recent experiment on
YCaBaNiO [J.F. DiTusa, et al., Phys. Rev. Lett. 73 1857(1994)].Comment: 4 pages of uuencoded gzip'd postscrip
Cosmological constraints on the generalized holographic dark energy
We use the Markov ChainMonte Carlo method to investigate global constraints
on the generalized holographic (GH) dark energy with flat and non-flat universe
from the current observed data: the Union2 dataset of type supernovae Ia
(SNIa), high-redshift Gamma-Ray Bursts (GRBs), the observational Hubble data
(OHD), the cluster X-ray gas mass fraction, the baryon acoustic oscillation
(BAO), and the cosmic microwave background (CMB) data. The most stringent
constraints on the GH model parameter are obtained. In addition, it is found
that the equation of state for this generalized holographic dark energy can
cross over the phantom boundary wde =-1.Comment: 14 pages, 5 figures. arXiv admin note: significant text overlap with
arXiv:1105.186
Combined constraints on modified Chaplygin gas model from cosmological observed data: Markov Chain Monte Carlo approach
We use the Markov Chain Monte Carlo method to investigate a global
constraints on the modified Chaplygin gas (MCG) model as the unification of
dark matter and dark energy from the latest observational data: the Union2
dataset of type supernovae Ia (SNIa), the observational Hubble data (OHD), the
cluster X-ray gas mass fraction, the baryon acoustic oscillation (BAO), and the
cosmic microwave background (CMB) data. In a flat universe, the constraint
results for MCG model are,
()
,
()
,
()
,
()
, and ()
.Comment: 12 pages, 1figur
Defect and anisotropic gap induced quasi-one-dimensional modulation of local density of states in YBaCuO
Motivated by recent angle-resolved photoemission spectroscopy (ARPES)
measurement that superconducting YBaCuO (YBCO) exhibits a
-symmetry gap, we show possible quasi-one-dimensional
modulations of local density of states in YBCO. These aniostropic gap and
defect induced stripe structures are most conspicuous at higher biases and
arise due to the nesting effect associated with a Fermi liquid. Observation of
these spectra by scanning tunneling microscopy (STM) would unify the picture
among STM, ARPES, and inelastic neutron scattering for YBCO.Comment: 4 pages, 4 figure
Wavefunction topology of two-dimensional time-reversal symmetric superconductors
We discuss the topology of the wavefunctions of two-dimensional time-reversal
symmetric superconductors. We consider (a) the planar state, (b) a system with
broken up-down reflection symmetry, and (c) a system with general spin-orbit
interaction. We show explicitly how the relative sign of the order parameter on
the two Fermi surfaces affects this topology, and clarify the meaning of the
classification for these topological states.Comment: only the Introduction has been modified from v
Cold atoms in videotape micro-traps
We describe an array of microscopic atom traps formed by a pattern of
magnetisation on a piece of videotape. We describe the way in which cold atoms
are loaded into one of these micro-traps and how the trapped atom cloud is used
to explore the properties of the trap. Evaporative cooling in the micro-trap
down to a temperature of 1 microkelvin allows us to probe the smoothness of the
trapping potential and reveals some inhomogeneity produced by the magnetic
film. We discuss future prospects for atom chips based on microscopic
permanent-magnet structures.Comment: Submitted for EPJD topical issue "Atom chips: manipulating atoms and
molecules with microfabricated structures
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