34,068 research outputs found
Transient analysis of unbalanced short circuits of the ERDA-NASA 100 kW wind turbine alternator
Unbalanced short-circuit faults on the alternator of the ERDA-NASA Mod-O100-kW experimental wind turbine are studied. For each case, complete solutions for armature, field, and damper-circuit currents; short-circuit torque; and open-phase voltage are derived directly by a mathematical analysis. Formulated results are tabulated. For the Mod-O wind turbine alternator, numerical calculations are given, and results are presented by graphs. Comparisons for significant points among the more important cases are summarized. For these cases the transients are found to be potentially severe. The effect of the alternator neutral-to-ground impedance is evaluated
Synchronization of the ERDA-NASA 100 LkW wind turbine generator with large utility networks
The synchronizing of a wind turbine generator against an infinite bus under random conditions is studied. With a digital computer, complete solutions for rotor speed, generator power angle, electromagnetic torque, wind turbine torque, wind turbine blade pitch angle, and armature current are obtained and presented by graphs
Unified Analysis of Cosmological Perturbations in Generalized Gravity
In a class of generalized Einstein's gravity theories we derive the equations
and general asymptotic solutions describing the evolution of the perturbed
universe in unified forms. Our gravity theory considers general couplings
between the scalar field and the scalar curvature in the Lagrangian, thus
includes broad classes of generalized gravity theories resulting from recent
attempts for the unification. We analyze both the scalar-type mode and the
gravitational wave in analogous ways. For both modes the large scale evolutions
are characterized by the same conserved quantities which are valid in the
Einstein's gravity. This unified and simple treatment is possible due to our
proper choice of the gauges, or equivalently gauge invariant combinations.Comment: 4 pages, revtex, no figure
Rotation misorientated graphene moire superlattices on Cu(111): classical molecular dynamics simulations and scanning tunneling microscopy studies
Graphene on copper is a system of high technological relevance, as Cu is one
of the most widely used substrates for the CVD growth of graphene. However,
very little is known about the details of their interaction. One approach to
gain such information is studying the superlattices emerging due to the
mismatch of the two crystal lattices. However, graphene on copper is a
low-corrugated system making both their experimental and theoretical study
highly challenging. Here, we report the observation of a new rotational Moire
superlattice of CVD graphene on Cu (111), characterized by a periodicity of
nm and corrugation of , as measured
by Scanning Tunneling Microscopy. To understand the observed superlattice we
have developed a newly parameterized Tersoff-potential for the graphene/Cu
(111) interface fitted to nonlocal van der Waals density functional theory
(DFT) calculations. The interfacial force field with time-lapsed CMD provides
superlattices in good quantitative agreement with the experimental results, for
a misorientation angle of without any further parameter
adjustment. Furthermore, the CMD simulations predict the existence of two
non-equivalent high-symmetry directions of the Moir\'e pattern that could also
be identified in the experimental STM images.Comment: 7 pages, 2 figures, 2 table
Nonuniqueness for the kinetic Fokker-Planck equation with inelastic boundary conditions
We describe the structure of solutions of the kinetic Fokker-Planck equations
in domains with boundaries near the singular set in one-space dimension. We
study in particular the behaviour of the solutions of this equation for
inelastic boundary conditions which are characterized by means of a coefficient
describing the amount of energy lost in the collisions of the particles
with the boundaries of the domain. A peculiar feature of this problem is the
onset of a critical exponent rc which follows from the analysis of McKean (cf.
[26]) of the properties of the stochastic process associated to the
Fokker-Planck equation under consideration. In this paper, we prove rigorously
that the solutions of the considered problem are nonunique if and
unique if . In particular, this nonuniqueness explains the
different behaviours found in the physics literature for numerical simulations
of the stochastic differential equation associated to the Fokker-Planck
equation. In the proof of the results of this paper we use several asymptotic
formulas and computations in the companion paper [16].Comment: 64 pages, 1 figure. Previous version has been split into tw
Recommended from our members
Rethinking the Creative Economy: Participatory Action Research with Artists and Artisans in the Greater Franklin County
The Rethinking the Creative Economy Project utilized a participatory action research methodology with an asset-based approach to examine the noncapitalist practices of artists and artisans in the context of a community economy. By privileging noncapitalist practices, the contributions of artists and artisans can be assigned value, where no or little value was assigned before. In the context of creative economy development, by ignoring the diverse economy of artists and artisans there is a real danger of continuing a narrative of deficits and a lack of agency. However, artists and artisans are crucial to the viability of a creative economy because of their civic engagement. Without the civic engagement of artists and artisans, their creative endeavors and influence are limited to the confines of their studios and their close relationships. When artists and artisans are able to participate in civic engagement, building a relationship with their community, and are encouraged and rewarded for this engagement, the artists and artisans have the potential to transform a place into a vibrant reflection of the kind of world they would like to inhabit, a world that prioritizes social justice, creative expression, and sustainability. This strengthening of a sense of place performs an increase in the quality of life for a community by enabling a core identity to be retained even as regions evolve and change
Compressibility of graphene
We develop a theory for the compressibility and quantum capacitance of
disordered monolayer and bilayer graphene including the full hyperbolic band
structure and band gap in the latter case. We include the effects of disorder
in our theory, which are of particular importance at the carrier densities near
the Dirac point. We account for this disorder statistically using two different
averaging procedures: first via averaging over the density of carriers
directly, and then via averaging in the density of states to produce an
effective density of carriers. We also compare the results of these two models
with experimental data, and to do this we introduce a model for inter-layer
screening which predicts the size of the band gap between the low-energy
conduction and valence bands for arbitary gate potentials applied to both
layers of bilayer graphene. We find that both models for disorder give
qualitatively correct results for gapless systems, but when there is a band gap
at charge neutrality, the density of states averaging is incorrect and
disagrees with the experimental data.Comment: 10 pages, 7 figures, RevTe
- …