1,207 research outputs found
Fault classification in dynamic processes using multiclass relevance vector machine and slow feature analysis
This paper proposes a modifed relevance vector machine with slow feature analysis fault classification for industrial processes. Traditional support vector machine classification does not work well when there are insufficient training samples. A relevance vector machine, which is a Bayesian learning-based probabilistic sparse model, is developed to determine the probabilistic prediction and sparse solutions for the fault category. This approach has the benefits of good generalization ability and robustness to small training samples. To maximize the dynamic separability between classes and reduce the computational complexity, slow feature analysis is used to extract the inner dynamic features and reduce the dimension. Experiments comparing the proposed method, relevance vector machine and support vector machine classification are performed using the Tennessee Eastman process. For all faults, relevance vector machine has a classification rate of 39%, while the proposed algorithm has an overall classification rate of 76.1%. This shows the efficiency and advantages of the proposed method
Robust decoupling mixed sensitivity controller design of looper control system for hot strip mill process
This article considers a robust decoupling controller design for a multivariate control system with parameter uncertainties for the hot rolling mill process. The left and right coprime factorization theory is used to properly select the free and weighting matrices. The necessary and sufficient conditions for robust decoupling controller are also proposed. Then, by analyzing the changes in the dynamic response resulting from perturbations in the tension and angle system parameters in the hot strip rolling process, a modified multivariate model is developed. Furthermore, the selection method for a practical weighting function is studied, so that the robust and decoupling performance can be simultaneously realized for the controller implementation. Finally, the effectiveness of the proposed control approach is demonstrated using a case study from an industrial hot rolling mill
An ADRC-based control strategy for FRT improvement of wind power generation with a doubly-fed induction generator
This paper proposes a second-order active disturbance rejection control (ADRC)-based control strategy with an integrated design of the flux damping method, for the fault ride-through (FRT) improvement in wind power generation systems with a doubly-fed induction generator (DFIG). First, a first principles model of the rotor and grid side converter of DFIG is developed, which is then used to theoretically analyze the system characteristics and show the damage caused to the DFIG system by a grid voltage fault. Then, the flux damping method is used to suppress the rotor current during a fault ride-through. In order to enhance the robustness and effectiveness of the flux damping method under complex working conditions, an ADRC approach is proposed for disturbance attenuation of the DFIG systems. Finally, a comparison of the proposed method with three other control approaches on a 1.5-MV DFIG system benchmark is performed. It is shown that the proposed method can adaptively and effectively improve the system performance during an FRT
The role of insulin receptor substrate 2 in hypothalamic and β cell function
Insulin receptor substrate 2 (Irs2) plays complex roles in energy homeostasis. We generated mice lacking Irs2 in β cells and a population of hypothalamic neurons (RIPCreIrs2KO), in all neurons (NesCreIrs2KO), and in proopiomelanocortin neurons (POMCCreIrs2KO) to determine the role of Irs2 in the CNS and β cell. RIPCreIrs2KO mice displayed impaired glucose tolerance and reduced β cell mass. Overt diabetes did not ensue, because β cells escaping Cre-mediated recombination progressively populated islets. RIPCreIrs2KO and NesCreIrs2KO mice displayed hyperphagia, obesity, and increased body length, which suggests altered melanocortin action. POMCCreIrs2KO mice did not display this phenotype. RIPCreIrs2KO and NesCreIrs2KO mice retained leptin sensitivity, which suggests that CNS Irs2 pathways are not required for leptin action. NesCreIrs2KO and POMCCreIrs2KO mice did not display reduced β cell mass, but NesCreIrs2KO mice displayed mild abnormalities of glucose homeostasis. RIPCre neurons did not express POMC or neuropeptide Y. Insulin and a melanocortin agonist depolarized RIPCre neurons, whereas leptin was ineffective. Insulin hyperpolarized and leptin depolarized POMC neurons. Our findings demonstrate a critical role for IRS2 in β cell and hypothalamic function and provide insights into the role of RIPCre neurons, a distinct hypothalamic neuronal population, in growth and energy homeostasis
Parking functions, labeled trees and DCJ sorting scenarios
In genome rearrangement theory, one of the elusive questions raised in recent
years is the enumeration of rearrangement scenarios between two genomes. This
problem is related to the uniform generation of rearrangement scenarios, and
the derivation of tests of statistical significance of the properties of these
scenarios. Here we give an exact formula for the number of double-cut-and-join
(DCJ) rearrangement scenarios of co-tailed genomes. We also construct effective
bijections between the set of scenarios that sort a cycle and well studied
combinatorial objects such as parking functions and labeled trees.Comment: 12 pages, 3 figure
Non-Markovian dynamics for an open two-level system without rotating wave approximation: Indivisibility versus backflow of information
By use of the two measures presented recently, the indivisibility and the
backflow of information, we study the non-Markovianity of the dynamics for a
two-level system interacting with a zero-temperature structured environment
without using rotating wave approximation (RWA). In the limit of weak coupling
between the system and the reservoir, and by expanding the time-convolutionless
(TCL) generator to the forth order with respect to the coupling strength, the
time-local non-Markovian master equation for the reduced state of the system is
derived. Under the secular approximation, the exact analytic solution is
obtained and the sufficient and necessary conditions for the indivisibility and
the backflow of information for the system dynamics are presented. In the more
general case, we investigate numerically the properties of the two measures for
the case of Lorentzian reservoir. Our results show the importance of the
counter-rotating terms to the short-time-scale non-Markovian behavior of the
system dynamics, further expose the relations between the two measures and
their rationality as non-Markovian measures. Finally, the complete positivity
of the dynamics of the considered system is discussed
Comparison of S=0 and S=1/2 Impurities in Haldane Chain Compound,
We present the effect of Zn (S=0) and Cu (S=1/2) substitution at the Ni site
of S=1 Haldane chain compound . Y NMR allows us to
measure the local magnetic susceptibility at different distances from the
defects. The Y NMR spectrum consists of one central peak and several
less intense satellite peaks. The shift of the central peak measures the
uniform susceptibility, which displays a Haldane gap 100 K and it
corresponds to an AF coupling J260 K between the near-neighbor Ni spins.
Zn or Cu substitution does not affect the Haldane gap. The satellites, which
are evenly distributed on the two sides of the central peak, probe the
antiferromagnetic staggered magnetization near the substituted site, which
decays exponentially. Its extension is found identical for both impurities and
corresponds accurately to the correlation length (T) determined by Monte
Carlo (QMC) simulations for the pure compound. In the case of non-magnetic Zn,
the temperature dependence of the induced magnetization is consistent with a
Curie law with an "effective" spin S=0.4 on each side of Zn, which is well
accounted by Quantum Monte Carlo computations of the spinless-defect-induced
magnetism. In the case of magnetic Cu, the similarity of the induced magnetism
to the Zn case implies a weak coupling of the Cu spin to the nearest- neighbor
Ni spins. The slight reductionin the induced polarization with respect to Zn is
reproduced by QMC computations by considering an antiferromagnetic coupling of
strength J'=0.1-0.2 J between the S=1/2 Cu-spin and nearest-neighbor Ni-spin.Comment: 15 pages, 18 figures, submitted to Physical Review
Higher order bulk characteristic parameters of asymmetric nuclear matter
The bulk parameters characterizing the energy of symmetric nuclear matter and
the symmetry energy defined at normal nuclear density provide
important information on the equation of state (EOS) of isospin asymmetric
nuclear matter. While significant progress has been made in determining some
lower order bulk characteristic parameters, such as the energy
and incompressibility of symmetric nuclear matter as well as the symmetry
energy and its slope parameter , yet the higher order bulk
characteristic parameters are still poorly known. Here, we analyze the
correlations between the lower and higher order bulk characteristic parameters
within the framework of Skyrme Hartree-Fock energy density functional and then
estimate the values of some higher order bulk characteristic parameters. In
particular, we obtain MeV and MeV for the
third-order and fourth-order derivative parameters of symmetric nuclear matter
at and MeV, MeV,
MeV for the curvature parameter, third-order and
fourth-order derivative parameters of the symmetry energy at , using
the empirical constraints on , , , , and
the isoscalar and isovector nucleon effective masses. Furthermore, our results
indicate that the three parameters , , and can
reasonably characterize the EOS of symmetric nuclear matter up to
while the symmetry energy up to can be well described by
, , and .Comment: 6 pages, 7 figures. Typos fixed. Contribution to a special issue in
Science China: Physics, Mechanics & Astronom
Isospin Asymmetry in Nuclei and Neutron Stars
The roles of isospin asymmetry in nuclei and neutron stars are investigated
using a range of potential and field-theoretical models of nucleonic matter.
The parameters of these models are fixed by fitting the properties of
homogeneous bulk matter and closed-shell nuclei. We discuss and unravel the
causes of correlations among the neutron skin thickness in heavy nuclei, the
pressure of beta-equilibrated matter at a density of 0.1 fm, the
derivative of the nuclear symmetry energy at the same density and the radii of
moderate mass neutron stars. Constraints on the symmetry properties of nuclear
matter from the binding energies of nuclei are examined. The extent to which
forthcoming neutron skin measurements will further delimit the symmetry
properties is investigated. The impact of symmetry energy constraints for the
mass and moment of inertia contained within neutron star crusts and the
threshold density for the nucleon direct Urca process, all of which are
potentially measurable, is explored. We also comment on the minimum neutron
star radius, assuming that only nucleonic matter exists within the star.Comment: 49 pages, 17 figures, Phys. Rep. (in press); made improvements to
"RAPR" and corrected transition densitie
Gravitational Lensing at Millimeter Wavelengths
With today's millimeter and submillimeter instruments observers use
gravitational lensing mostly as a tool to boost the sensitivity when observing
distant objects. This is evident through the dominance of gravitationally
lensed objects among those detected in CO rotational lines at z>1. It is also
evident in the use of lensing magnification by galaxy clusters in order to
reach faint submm/mm continuum sources. There are, however, a few cases where
millimeter lines have been directly involved in understanding lensing
configurations. Future mm/submm instruments, such as the ALMA interferometer,
will have both the sensitivity and the angular resolution to allow detailed
observations of gravitational lenses. The almost constant sensitivity to dust
emission over the redshift range z=1-10 means that the likelihood for strong
lensing of dust continuum sources is much higher than for optically selected
sources. A large number of new strong lenses are therefore likely to be
discovered with ALMA, allowing a direct assessment of cosmological parameters
through lens statistics. Combined with an angular resolution <0.1", ALMA will
also be efficient for probing the gravitational potential of galaxy clusters,
where we will be able to study both the sources and the lenses themselves, free
of obscuration and extinction corrections, derive rotation curves for the
lenses, their orientation and, thus, greatly constrain lens models.Comment: 69 pages, Review on quasar lensing. Part of a LNP Topical Volume on
"Dark matter and gravitational lensing", eds. F. Courbin, D. Minniti. To be
published by Springer-Verlag 2002. Paper with full resolution figures can be
found at ftp://oden.oso.chalmers.se/pub/tommy/mmviews.ps.g
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