15,449 research outputs found
Distributed state estimation in sensor networks with randomly occurring nonlinearities subject to time delays
This is the post-print version of the Article. The official published version can be accessed from the links below - Copyright @ 2012 ACM.This article is concerned with a new distributed state estimation problem for a class of dynamical systems in sensor networks. The target plant is described by a set of differential equations disturbed by a Brownian motion and randomly occurring nonlinearities (RONs) subject to time delays. The RONs are investigated here to reflect network-induced randomly occurring regulation of the delayed states on the current ones. Through available measurement output transmitted from the sensors, a distributed state estimator is designed to estimate the states of the target system, where each sensor can communicate with the neighboring sensors according to the given topology by means of a directed graph. The state estimation is carried out in a distributed way and is therefore applicable to online application. By resorting to the Lyapunov functional combined with stochastic analysis techniques, several delay-dependent criteria are established that not only ensure the estimation error to be globally asymptotically stable in the mean square, but also guarantee the existence of the desired estimator gains that can then be explicitly expressed when certain matrix inequalities are solved. A numerical example is given to verify the designed distributed state estimators.This work was supported in part by the National Natural Science Foundation of China under Grants 61028008, 60804028 and 61174136, the Qing Lan Project of Jiangsu Province of China, the Project sponsored by SRF for ROCS of SEM of China, the Engineering and Physical Sciences Research Council (EPSRC) of the UK under Grant GR/S27658/01, the Royal Society of the UK,
and the Alexander von Humboldt Foundation of Germany
Quasi-classical determination of the in-plane magnetic field phase diagram of superconducting Sr_2RuO_4
We have carried out a determination of the magnetic-field-temperature (H-T)
phase diagram for realistic models of the high field superconducting state of
tetragonal Sr_2RuO_4 with fields oriented in the basal plane. This is done by a
variational solution of the Eilenberger equations.This has been carried for
spin-triplet gap functions with a {\bf d}-vector along the c-axis (the chiral
p-wave state) and with a {\bf d}-vector that can rotate easily in the basal
plane. We find that, using gap functions that arise from a combination of
nearest and next nearest neighbor interactions, the upper critical field can be
approximately isotropic as the field is rotated in the basal plane. For the
chiral {\bf d}-vector, we find that this theory generically predicts an
additional phase transition in the vortex state. For a narrow range of
parameters, the chiral {\bf d}-vector gives rise to a tetracritical point in
the H-T phase diagram. When this tetracritical point exists, the resulting
phase diagram closely resembles the experimentally measured phase diagram for
which two transitions are only observed in the high field regime. For the
freely rotating in-plane {\bf d}-vector, we also find that additional phase
transition exists in the vortex phase. However, this phase transition
disappears as the in-plane {\bf d}-vector becomes weakly pinned along certain
directions in the basal plane.Comment: 12 pages, 8 figure
Emergence of intrinsic superconductivity below 1.178 K in the topologically non-trivial semimetal state of CaSn3
Topological materials which are also superconducting are of great current
interest, since they may exhibit a non-trivial topologically-mediated
superconducting phase. Although there have been many reports of pressure-tuned
or chemical-doping-induced superconductivity in a variety of topological
materials, there have been few examples of intrinsic, ambient pressure
superconductivity in a topological system having a stoichiometric composition.
Here, we report that the pure intermetallic CaSn3 not only exhibits topological
fermion properties but also has a superconducting phase at 1.178 K under
ambient pressure. The topological fermion properties, including the nearly zero
quasi-particle mass and the non-trivial Berry phase accumulated in cyclotron
motions, were revealed from the de Haas-van Alphen (dHvA) quantum oscillation
studies of this material. Although CaSn3 was previously reported to be
superconducting at 4.2K, our studies show that the superconductivity at 4.2K is
extrinsic and caused by Sn on the degraded surface, whereas its intrinsic bulk
superconducting transition occurs at 1.178 K. These findings make CaSn3 a
promising candidate for exploring new exotic states arising from the interplay
between non-trivial band topology and superconductivity, e.g. topological
superconductivityComment: 20 pages,4 figure
Weak anisotropy of the superconducting upper critical field in Fe1.11Te0.6Se0.4 single crystals
We have determined the resistive upper critical field Hc2 for single crystals
of the superconductor Fe1.11Te0.6Se0.4 using pulsed magnetic fields of up to
60T. A rather high zero-temperature upper critical field of mu0Hc2(0) approx
47T is obtained, in spite of the relatively low superconducting transition
temperature (Tc approx 14K). Moreover, Hc2 follows an unusual temperature
dependence, becoming almost independent of the magnetic field orientation as
the temperature T=0. We suggest that the isotropic superconductivity in
Fe1.11Te0.6Se0.4 is a consequence of its three-dimensional Fermi-surface
topology. An analogous result was obtained for (Ba,K)Fe2As2, indicating that
all layered iron-based superconductors exhibit generic behavior that is
significantly different from that of the high-Tc cuprates.Comment: 4 pages, 4 figures, submit to PR
Exploration of water-recycled cassava bioethanol production integrated with anaerobic digestion treatment
Due to the limited success of discharge target-hitting treatment in coping with environmental pollution from the alcohol industry, our attention was directed towards the distillery spent (DS) wash recycle in a cleaner bioethanol production by integrating anaerobic digestion treatment with conventional fermentation. An anaerobic digestion effluent from an alcohol waste water treatment plant is applicable for single use in ethanol fermentation. With further experimental estimate, the recycle of DS treated by a sole thermophilic up flow anaerobic sludge blanket (UASB) treatment was adverse to ethanol fermentation, resulting in a gradual increase of the residual total sugar from 1.2% at batch 1 to 8.0% at batch 5 after 48 h. With a combination of the thermophilic and mesophilic UASB treatment, the thirteenbatch fermentation recycling its DS achieved ~10.5% of ethanol production and > 90% of starch utilization after 48 h, which was comparable to that using tap water. This revealed a potential of the anaerobic digestion treatment in water-saving and emission reduction for bioethanol industry.Key words: Anaerobic digestion, cassava, cleaner bioethanol production, distillery spent wash, thermophilic and mesophilic up flow anaerobic sludge blanket, recycle and reuse
Anisotropy of magnetothermal conductivity in Sr2RuO4
The dependence of in-plane and interplane thermal conductivities of Sr2RuO4
on temperature, as well as magnetic field strength and orientation, is
reported. We found no notable anisotropy in the thermal conductivity for the
magnetic field rotation parallel to the conducting plane in the whole range of
experimental temperatures and fields, except in the vicinity of the upper
critical field Hc2, where the anisotropy of the Hc2 itself plays a dominant
role. This finding imposes strong constraints on the possible models of
superconductivity in Sr2RuO4 and supports the existence of a superconducting
gap with a line of nodes running orthogonal to the Fermi surface cylinder.Comment: published in Phys. Rev. Lett. 4pages, 4 eps figures, LaTe
Uncovering a pressure-tuned electronic transition in BiSrYCu2O8 using Raman scattering and x-ray diffraction
We report pressure tuned Raman and x-ray diffraction data of
Bi1.98Sr2.06Y0.68Cu2O8 revealing a critical pressure at 21 GPa with anomalies
in six physical quantities: electronic Raman background, electron-phonon
coupling, spectral weight transfer from high to low frequency, density
dependent behaviour of phonon and magnon frequencies, and a compressibility
change in the c-axis. For the first time in a cuprate, mobile charge carriers,
lattice, and magnetism all show anomalies at a distinct critical pressure in
the same experimental setting. Furthermore, the Raman spectral changes are
similar to that seen traversing the superconducting dome with doping,
suggesting that the critical pressure at 21 GPa is related to the much
discussed critical point at optimal doping.Comment: 5 pages, 4 figures, submitted to PR
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