1,790 research outputs found
Smart Asset Management for Electric Utilities: Big Data and Future
This paper discusses about future challenges in terms of big data and new
technologies. Utilities have been collecting data in large amounts but they are
hardly utilized because they are huge in amount and also there is uncertainty
associated with it. Condition monitoring of assets collects large amounts of
data during daily operations. The question arises "How to extract information
from large chunk of data?" The concept of "rich data and poor information" is
being challenged by big data analytics with advent of machine learning
techniques. Along with technological advancements like Internet of Things
(IoT), big data analytics will play an important role for electric utilities.
In this paper, challenges are answered by pathways and guidelines to make the
current asset management practices smarter for the future.Comment: 13 pages, 3 figures, Proceedings of 12th World Congress on
Engineering Asset Management (WCEAM) 201
75As NMR local probe study of magnetism in (Eu1-xKx)Fe2As2
75As NMR measurements were performed as a function of temperature and doping
in (Eu1-xKx)Fe2As2 (x=0,0.38,0.5,0.7) samples. The large Eu2+ moments and their
fluctuations are found to dominate the 75As NMR properties. The 75As nuclei
close to the Eu2+ moments likely have a very short spin-spin relaxation time
(T2) and are wiped out of our measurement window. The 75As nuclei relatively
far from Eu2+ moments are probed in this study. Increasing the Eu content
progressively decreases the signal intensity with no signal found for the
full-Eu sample (x=0). The large 75As NMR linewidth arises from an inhomogeneous
magnetic environment around them. The spin lattice relaxation rate (1/T1) for
x=0.5 and 0.7 samples is nearly independent of temperature above 100K and
results from a coupling to paramagnetic fluctuations of the Eu2+ moments. The
behavior of 1/T1 at lower temperatures has contributions from the
antiferromagnetic fluctuations of the Eu2+ moments as also the fluctuations
intrinsic to the FeAs planes and from superconductivity.Comment: 6 pages, 6 figures (to appear in EPJB
Magnetism and superconductivity in Eu0.2Sr0.8(Fe0.86Co0.14)2As2 probed by 75As NMR
We report bulk superconductivity (SC) in
EuSr(FeCo)As single crystals by
means of electrical resistivity, magnetic susceptibility, and specific heat
measurements with 20 K with an antiferromagnetic
(AFM) ordering of Eu moments at 2.0 K in
zero field. As NMR experiments have been performed in the two external
field directions (H) and (H). As-NMR spectra are analyzed in
terms of first order quadrupolar interaction. Spin-lattice relaxation rates
(1/) follow a law in the temperature range 4.2-15 K. There is no
signature of Hebel-Slichter coherence peak just below the SC transition
indicating a non s-wave or s type of superconductivity. The increase of
1/ with lowering the temperature in the range 160-18 K following
law reflecting 2D AFM spin fluctuations
Optimally Convex Controller and Model Reduction for a Dynamic System
This paper presents analysis and design of a family of controllers based on numerical convex optimization for an aircraft pitch control system. A design method is proposed here to solve control system design problems in which a set of multiple closed loop performance specifications are simultaneously satisfied. The transfer matrix of the system is determined through the convex combination of the transfer matrices of the plant and the controllers. The present system with optimal convex controller has been tested for stability using Kharitonov’s Stability Criteria. The simulation deals here withthe problem of pitch control system of a BRAVO fighter aircraft which results in higher order close loop transfer function. So the order of the higher order transfer function is reduced to minimize the complexity of the system
Magnetic susceptibility and heat capacity of a novel antiferromagnet: LiNi2P3O10 and the effect of doping
We report the synthesis, x-ray diffraction, magnetic susceptibility and
specific heat measurements on polycrystalline samples of undoped LiNi2P3O10 and
samples with non-magnetic impurity (Zn2+, S = 0) and magnetic impurity (Cu2+, S
= 1/2) at the Ni site. The magnetic susceptibility data show a broad maximum at
around 10 K and a small anomaly at about 7 K in the undoped sample.There is a
lambda-like anomaly in the specific heat at 7 K, possibly due to the onset of
antiferromagnetic ordering in the system. The magnetic entropy change at the
ordering temperature is close to the value corresponding to Rln(2S+1) expected
for an S = 1 system. The temperature corresponding to the broad maximum and the
ordering temperature both decrease on Zn and Cu substitutions and also in
applied magnetic fields
Field tuned critical fluctuations in YFe2Al10: Evidence from magnetization, 27Al (NMR, NQR) investigations
We report magnetization, specific heat, and NMR investigations on YFe2Al10
over a wide range in temperature and magnetic field and zero field (NQR)
measurements. Magnetic susceptibility, specific heat and spin-lattice
relaxation rate divided by T (1/T1T) follow a weak power law (T^-0.4)
temperature dependence, which is a signature of critical fluctuations of Fe
moments. The value of the Sommerfeld-Wilson ratio and linear relation between
1/T1T and chi(T) suggest the existence of ferromagnetic correlations in this
system. No magnetic ordering down to 50 mK in Cp(T) and the unusual temperature
and field scaling of the bulk and NMR data are associated with a magnetic
instability which drives the system to quantum criticality. The magnetic
properties of the system are tuned by field wherein ferromagnetic fluctuations
are suppressed and a crossover from quantum critical to FL behavior is observed
with increasing magnetic field
Spin liquid behaviour in Jeff=1/2 triangular lattice Ba3IrTi2O9
Ba3IrTi2O9 crystallizes in a hexagonal structure consisting of a layered
triangular arrangement of Ir4+ (Jeff=1/2). Magnetic susceptibility and heat
capacity data show no magnetic ordering down to 0.35K inspite of a strong
magnetic coupling as evidenced by a large Curie-Weiss temperature=-130K. The
magnetic heat capacity follows a power law at low temperature. Our measurements
suggest that Ba3IrTi2O9 is a 5d, Ir-based (Jeff=1/2), quantum spin liquid on a
2D triangular lattice.Comment: 10 pages including supplemental material, to be published in Phys.
Rev. B (Rapid Comm.
Contiguous 3d and 4f magnetism: towards strongly correlated 3d electrons in YbFe2Al10
We present magnetization, specific heat, and 27Al NMR investigations on
YbFe2Al10 over a wide range in temperature and magnetic field. The magnetic
susceptibility at low temperatures is strongly enhanced at weak magnetic
fields, accompanied by a ln(T0/T) divergence of the low-T specific heat
coefficient in zero field, which indicates a ground state of correlated
electrons. From our hard X-ray photo emission spectroscopy (HAXPES) study, the
Yb valence at 50 K is evaluated to be 2.38. The system displays valence
fluctuating behavior in the low to intermediate temperature range, whereas
above 400 K, Yb3+ carries a full and stable moment, and Fe carries a moment of
about 3.1 mB. The enhanced value of the Sommerfeld Wilson ratio and the dynamic
scaling of spin-lattice relaxation rate divided by T [27(1/T1T)] with static
susceptibility suggests admixed ferromagnetic correlations. 27(1/T1T)
simultaneously tracks the valence fluctuations from the 4f -Yb ions in the high
temperature range and field dependent antiferromagnetic correlations among
partially Kondo screened Fe 3d moments at low temperature, the latter evolve
out of an Yb 4f admixed conduction band.Comment: To appear in Phys. Rev. Let
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