9,939 research outputs found
Iron Losses Prediction with PWM Supply Using Low and High Frequency Measurements: Analysis and Results Comparison
In this paper, two different methods for iron loss prediction are analyzed. The first method is based on the classical separation of loss contributions (hysteresis, eddy-current, and excess losses). The model requires loss contribution separation using iron loss measurements with sinusoidal supply. In this paper, this method will be called the ldquolow-frequency method.rdquo The second method, named the ldquohigh-frequency method,rdquo is based on the assumption that, under pulsewidth modulation supply, the higher order flux density harmonics do not influence the magnetic work conditions. These magnetic conditions depend only on the amplitude of the fundamental harmonic of the flux density. In this paper, both the proposed methodologies and the related measurements are described in detail, and the obtained results are compared with the experimental ones. The experimental results show that both methods allow getting excellent results. The high-frequency method is better than the lower one but requires a more complex test bench. Depending on the accuracy required by the user, the more handy method can be chosen, with the guarantee that the estimation errors will be lower than 5
Extraction of proton form factors in the timelike region from unpolarized e+e- --> p pbar events
We have performed numerical simulations of the unpolarized e+e- --> p pbar
process in kinematic conditions under discussion for a possible upgrade of the
existing DAFNE facility. By fitting the cross section angular distribution with
a typical Born expression, we can extract information on the ratio |G_E/G_M| of
the proton electromagnetic form factors in the timelike region within a 5-10%
uncertainty. We have explored also non-Born contributions to the cross section
by introducing a further component in the angular fit, which is related to
two-photon exchange diagrams. We show that these corrections can be identified
if larger than 5% of the Born contribution, and if relative phases of the
complex form factors do not produce severe cancellations.Comment: 10 pages in RevTeX style; 8 figures in eps forma
Valorizar a paisagem : ver o mar com outros olhos
A secção UAciência é coordenada pelo Professor Universitário Armindo Rodrigues.O objetivo principal do projeto SCAPETOUR — Promoção das paisagens costeiras e marinhas para a diversificação de produtos turísticos e o de promover o turismo de natureza nos Açores, proporcionando informação com base científica em geo e biodiversidade, bem como avaliar e conceber percursos ecoturísticos para atividades como por exemplo coasteering, canyoning e mergulho. Pretendemos assim, valorizar a paisagem costeira e marinha com base em vários critérios que combinam naturalidade, perceção dos turistas/operadores e importância da vida marinha (fauna e flora).
O Arquipélago dos Açores apresenta um elevado potencial para o turismo, devido às suas características diferenciadoras e a sua beleza natural, tendo sido recentemente distinguido com a atribuição do certificado de destino turístico sustentável, pelo Global Sustainable Tourism Council. O sector do turismo é considerado como uma prioridade estratégica para o desenvolvimento da economia regional.
[…].info:eu-repo/semantics/publishedVersio
Mosaic multi-state scenario vs. one-state description of supercooled liquids
According to the mosaic scenario, relaxation in supercooled liquids is ruled
by two competing mechanisms: surface tension, opposing the creation of local
excitations, and entropy, providing the drive to the configurational
rearrangement of a given region. We test this scenario through numerical
simulations well below the Mode Coupling temperature. For an equilibrated
configuration, we freeze all the particles outside a sphere and study the
thermodynamics of this sphere. The frozen environment acts as a pinning field.
Measuring the overlap between the unpinned and pinned equilibrium
configurations of the sphere, we can see whether it has switched to a different
state. We do not find any clear evidence of the mosaic scenario. Rather, our
results seem compatible with the existence of a single (liquid) state. However,
we find evidence of a growing static correlation length, apparently unrelated
to the mosaic one.Comment: 4 pages, 3 figures, final version accepted in PR
Growth and Containment of a Hierarchical Criminal Network
We model the hierarchical evolution of an organized criminal network via
antagonistic recruitment and pursuit processes. Within the recruitment phase, a
criminal kingpin enlists new members into the network, who in turn seek out
other affiliates. New recruits are linked to established criminals according to
a probability distribution that depends on the current network structure. At
the same time, law enforcement agents attempt to dismantle the growing
organization using pursuit strategies that initiate on the lower level nodes
and that unfold as self-avoiding random walks. The global details of the
organization are unknown to law enforcement, who must explore the hierarchy
node by node. We halt the pursuit when certain local criteria of the network
are uncovered, encoding if and when an arrest is made; the criminal network is
assumed to be eradicated if the kingpin is arrested. We first analyze
recruitment and study the large scale properties of the growing network; later
we add pursuit and use numerical simulations to study the eradication
probability in the case of three pursuit strategies, the time to first
eradication and related costs. Within the context of this model, we find that
eradication becomes increasingly costly as the network increases in size and
that the optimal way of arresting the kingpin is to intervene at the early
stages of network formation. We discuss our results in the context of dark
network disruption and their implications on possible law enforcement
strategies.Comment: 16 pages, 11 Figures; New title; Updated figures with color scheme
better suited for colorblind readers and for gray scale printin
New analytic solutions of the collective Bohr hamiltonian for a beta-soft, gamma-soft axial rotor
New analytic solutions of the quadrupole collective Bohr hamiltonian are
proposed, exploiting an approximate separation of the beta and gamma variables
to describe gamma-soft prolate axial rotors. The model potential is a sum of
two terms: a beta-dependent term taken either with a Coulomb-like or a
Kratzer-like form, and a gamma-dependent term taken as an harmonic oscillator.
In particular it is possible to give a one parameter paradigm for a beta-soft,
gamma-soft axial rotor that can be applied, with a considerable agreement, to
the spectrum of 234U.Comment: (Dipartimento di Fisica ``G.Galilei'' and INFN, via Marzolo 8,
I-35131 Padova, Italy) 10 pages, 3 figure
Supersymmetric exact sequence, heat kernel and super KdV hierarchy
We introduce the free N=1 supersymmetric derivation ring and prove the
existence of an exact sequence of supersymmetric rings and linear
transformations. We apply necessary and sufficient conditions arising from this
exact supersymmetric sequence to obtain the essential relations between
conserved quantities, gradients and the N=1 super KdV hierarchy. We combine
this algebraic approach with an analytic analysis of the super heat operator.We
obtain the explicit expression for the Green's function of the super heat
operator in terms of a series expansion and discuss its properties. The
expansion is convergent under the assumption of bounded bosonic and fermionic
potentials. We show that the asymptotic expansion when of the Green's
function for the super heat operator evaluated over its diagonal generates all
the members of the N=1 super KdV hierarchy.Comment: 20 pages, to be published in JM
Thermoelasticity of Fe2+-bearing bridgmanite
We present LDA+U calculations of high temperature elastic properties of
bridgmanite with composition (MgFe)SiO for
. Results of elastic moduli and acoustic velocities for the
Mg-end member (x=0) agree very well with the latest high pressure and high
temperature experimental measurements. In the iron-bearing system, we focus
particularly on the change in thermoelastic parameters across the state change
that occurs in ferrous iron above 30 GPa, often attributed to a high-spin
(HS) to intermediate spin (IS) crossover but explained by first principles
calculations as a lateral displacement of substitutional iron in the perovskite
cage. We show that the measured effect of this change on the equation of state
of this system can be explained by the lateral displacement of substitutional
iron, not by the HS to IS crossover. The calculated elastic properties of
(MgFe)SiO along an adiabatic mantle geotherm,
somewhat overestimate longitudinal velocities but produce densities and shear
velocities quite consistent with Preliminary Reference Earth Model data
throughout most of the lower mantle.Comment: Accepted for Geophysical Research Letters (DOI: 10.1002/2014GL062888
Measurement of correlations between low-frequency vibrational modes and particle rearrangements in quasi-two-dimensional colloidal glasses
We investigate correlations between low-frequency vibrational modes and
rearrangements in two-dimensional colloidal glasses composed of thermosensitive
microgel particles which readily permit variation of sample packing fraction.
At each packing fraction, the particle displacement covariance matrix is
measured and used to extract the vibrational spectrum of the "shadow" colloidal
glass (i.e., the particle network with the same geometry and interactions as
the sample colloid but absent damping). Rearrangements are induced by
successive, small reductions in packing fraction. The experimental results
suggest that low-frequency quasi-localized phonon modes in colloidal glasses,
i.e., modes that present low energy barriers for system rearrangements, are
spatially correlated with rearrangements in this thermal system
The Structure of Citizen Bystander Offering Behaviors Immediately After the Boston Marathon Bombing
In April of 2013, two pressure cooker bombs detonated near the finish line of the Boston Marathon. The resulting crowdsourced criminal investigation has been subject to intense scrutiny. What has not been discussed are the offering behaviors of Twitter users immediately following the detonations. The hashtag #BostonHelp offers a case study of what emergent, computer-mediated groups offer victims of a crisis event. Through creative appropriation of at-hand technologies (CAAT), this emergent group organized online offering and information about tangible resources on the ground. In this case, #BostonHelp participants harnessed blogs, social media, Google Forms, and pre-existing services to organize help for those in need. The resulting structure stabilized and became a symbol of the response itself. This case study offers an analysis of the structure created by computer-mediated crowds. We conclude with a discussion of trying to design, or even detect these behaviors at the start of a crisis response
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