2,008 research outputs found
Supervisory observer for parameter and state estimation of nonlinear systems using the DIRECT algorithm
A supervisory observer is a multiple-model architecture, which estimates the
parameters and the states of nonlinear systems. It consists of a bank of state
observers, where each observer is designed for some nominal parameter values
sampled in a known parameter set. A selection criterion is used to select a
single observer at each time instant, which provides its state estimate and
parameter value. The sampling of the parameter set plays a crucial role in this
approach. Existing works require a sufficiently large number of parameter
samples, but no explicit lower bound on this number is provided. The aim of
this work is to overcome this limitation by sampling the parameter set
automatically using an iterative global optimisation method, called DIviding
RECTangles (DIRECT). Using this sampling policy, we start with 1 + 2np
parameter samples where np is the dimension of the parameter set. Then, the
algorithm iteratively adds samples to improve its estimation accuracy.
Convergence guarantees are provided under the same assumptions as in previous
works, which include a persistency of excitation condition. The efficacy of the
supervisory observer with the DIRECT sampling policy is illustrated on a model
of neural populations
StreetlightSim: a simulation environment to evaluate networked and adaptive street lighting
Sustaining the operation of street lights incurs substantial financial and environmental cost. Consequently, adaptive lighting systems have been proposed incorporating ad-hoc networking, sensing, and data processing, in order to better manage the street lights and their energy demands. Evaluating the efficiency and effectiveness of these complex systems requires the modelling of vehicles, road networks, algorithms, and communication systems, yet tools are not available to permit this. This paper proposes StreetlightSim, a novel simulation environment combining OMNeT++ and SUMO tools to model both traffic patterns and adaptive networked street lights. StreetlightSim’s models are illustrated through the simulation of a simple example, and a more complex scenario is used to show the potential of the tool and the obtainable results. StreetlightSim has been made open-source, and hence is available to the community
Long time dynamics following a quench in an integrable quantum spin chain: local versus non-local operators and effective thermal behavior
We study the dynamics of the quantum Ising chain following a zero-temperature
quench of the transverse field strength. Focusing on the behavior of two-point
spin correlation functions, we show that the correlators of the order parameter
display an effective asymptotic thermal behavior, i.e., they decay
exponentially to zero, with a phase coherence rate and a correlation length
dictated by the equilibrium law with an effective temperature set by the energy
of the initial state. On the contrary, the two-point correlation functions of
the transverse magnetization or the density-of-kinks operator decay as a
power-law and do not exhibit thermal behavior. We argue that the different
behavior is linked to the locality of the corresponding operator with respect
to the quasi-particles of the model: non-local operators, such as the order
parameter, behave thermally, while local ones do not. We study which features
of the two-point correlators are a consequence of the integrability of the
model by analizing their robustness with respect to a sufficiently strong
integrability-breaking term.Comment: 18 pages, 11 figures, published version. Extensive changes, one
author adde
ACCELERATIVE STABILIZATION OF SOLID WASTE IN ANAEROBIC/AEROBIC LAB-SCALE LANDFILL BIOREACTORS
Joint Research on Environmental Science and Technology for the Eart
Finite-temperature Mott transitions in multi-orbital Hubbard model
We investigate the Mott transitions in the multi-orbital Hubbard model at
half-filling by means of the self-energy functional approach. The phase
diagrams are obtained at finite temperatures for the Hubbard model with up to
four-fold degenerate bands. We discuss how the first-order Mott transition
points and as well as the critical temperature depend
on the orbital degeneracy. It is elucidated that enhanced orbital fluctuations
play a key role to control the Mott transitions in the multi-orbital Hubbard
model.Comment: 8 pages, 7 figure
Clinical evaluation of the Shin-Nippon SRW-5000 autorefractor in adults:an update
Purpose: The Shin-Nippon SRW-5000 is an open view autorefractor that superseded the Canon R-1 autorefractor in the mid-1990s and has been used widely in optometry and vision science laboratories. It has been used to measure refractive error, accommodation responses both statically and dynamically, off-axis refractive error, and adapted to measure pupil size. This paper presents an overview of the original 2001 clinical evaluation of the SRW-5000 in adults (Mallen et al., Ophthal Physiol Opt 2001; 21: 101) and provides an update on the use and modification of the instrument since the original publication. Recent findings: The SRW-5000 instrument, and the family of devices which followed, have shown excellent validity, repeatability, and utility in clinical and research settings. The instruments have also shown great potential for increased research functionality following a number of modifications. Summary: The SRW-5000 and its derivatives have been, and continue to be, of significant importance in our drive to understand myopia progression, myopia control techniques, and oculomotor function in human vision
Field-induced phase transitions in a Kondo insulator
We study the magnetic-field effect on a Kondo insulator by exploiting the
periodic Anderson model with the Zeeman term. The analysis using dynamical mean
field theory combined with quantum Monte Carlo simulations determines the
detailed phase diagram at finite temperatures. At low temperatures, the
magnetic field drives the Kondo insulator to a transverse antiferromagnetic
phase, which further enters a polarized metallic phase at higher fields. The
antiferromagnetic transition temperature takes a maximum when the Zeeman
energy is nearly equal to the quasi-particle gap. In the paramagnetic phase
above , we find that the electron mass gets largest around the field where
the quasi-particle gap is closed. It is also shown that the induced moment of
conduction electrons changes its direction from antiparallel to parallel to the
field.Comment: 7 pages, 6 figure
Poster Abstract: Solar-Powered Adaptive Street Lighting Evaluated with Real Traffic and Sunlight Data
Street lighting is an important resource; it has been shown to reduce crime, improve road safety, and increase economic activity. These benefits, however, come with a cost: an annual emission of 64 million tonnes of CO2. Solar-powered street lighting is attractive for its use of renewable energy and its ease of installation (particularly in off-grid applications), but sizing and control is a non-trivial task. This paper describes TALiSMaN-Green, a traffic-aware street lighting scheme which takes account of road users as well as the available energy to dynamically adjust lighting levels. Simulations using real traffic and sunlight data illustrate that solar-powered streetlights can be managed to deliver consistent usefulness throughout the night
Incommensurate state in a quasi-one-dimensional bond-alternating antiferromagnet with frustration in magnetic fields
We investigate the critical properties of the bond-alternating spin
chain with a next-nearest-neighbor interaction in magnetic fields. By the
numerical calculation and the exact solution based on the effective
Hamiltonian, we show that there is a parameter region where the longitudinal
incommensurate spin correlation becomes dominant around the half-magnetization
of the saturation. Possible interpretations of our results are discussed. We
next investigate the effects of the interchain interaction (). The
staggered susceptibility and the uniform magnetization are calculated by
combining the density-matrix renormalization group method with the interchain
mean-field theory. For the parameters where the dominant longitudinal
incommensurate spin correlation appears in the case , the
staggered long-range order does not emerge up to a certain critical value of
around the half-magnetization of the saturation. We calculate the
static structure factor in such a parameter region. The size dependence of the
static structure factor at implies that the system has a
tendency to form an incommensurate long-range order around the
half-magnetization of the saturation. We discuss the recent experimental
results for the NMR relaxation rate in magnetic fields performed for
pentafluorophenyl nitronyl nitroxide.Comment: 10 pages, 12 figures, final version, to appear in PRB vol. 70, No. 5
(2004
- …