76,371 research outputs found
Minimal formulation of the linear spatial analysis of capillary jets: Validity of the two-mode approach
A rigorous and complete formulation of the linear evolution of harmonically stimulated
capillary jets should include infinitely many spatial modes to account for arbitrary exit
conditions [J. Guerrero et al., J. Fluid Mech. 702, 354 (2012)]. However, it is not rare to
find works in which only the downstream capillary dominant mode, the sole unstable one,
is retained, with amplitude determined by the jet deformation at the exit. This procedure
constitutes an oversimplification, unable to handle a flow rate perturbation without jet
deformation at the exit (the most usual conditions). In spite of its decaying behavior, the
other capillary mode (subdominant) must be included in what can be called a “minimal
linear formulation.” Deformation and mean axial velocity amplitudes at the jet exit are the
two relevant parameters to simultaneously find the amplitudes of both capillary modes.
Only once these amplitudes are found, the calculation of the breakup length may be
eventually simplified by disregarding the subdominant mode. Simple recipes are provided
for predicting the breakup length, which are checked against our own numerical simulations.
The agreement is better than in previous attempts in the literature. Besides, the limits of
validity of the linear formulation are explored in terms of the exit velocity amplitude, the
wave number, the Weber number, and the Ohnesorge number. Including the subdominant
mode extends the range of amplitudes for which the linear model gives accurate predictions,
the criterion for keeping this mode being that the breakup time must be shorter than a
given formula. It has been generally assumed that the shortest intact length happens for the
stimulation frequency with the highest growth rate. However, we show that this correlation
is not strict because the amplitude of the dominant mode has a role in the breakup process
and it depends on the stimulation frequency.Ministerio de Economía, Industria y Competitividad, Spain, under Contract No. FIS2014-25161Junta de Andalucía under Contract No. P11-FQM-791
Interaction and imitation in a world of Quixotes and Sanchos
Producción CientíficaThis paper studies a two-population evolutionary game in a new setting in between a symmetric and an asymmetric evolutionary model. It distinguishes two types of agents: Sanchos, whose payoffs are defined by a prisoner’s dilemma game, and Quixotes, whose payoffs are defined by a snowdrift game. Considering an imitative revision protocol, a revising agent is paired with someone from his own population or the other population. When matched, they observe payoffs, but not identities. Thus, agents in one population interact and imitate agents from their own population and from the other population. In this setting we prove that a unique mixed-strategy asymptotically stable fixed point of the evolutionary dynamics exists. Taking as an example the compliance with social norms, and depending on the parameters, two type of equilibrium are possible, one with full compliance among Quixotes and partial compliance among Sanchos, or another with partial compliance among Quixotes and defection among Sanchos. In the former type, Sanchos comply above their Nash equilibrium (as they imitate compliant Quixotes). In the latter type, Quixotes comply below their Nash equilibrium (as they imitate defecting Sanchos)
X-ray/gamma-ray flux correlations in the BL Lacs Mrk 421 and 501 using HAWC data
The HAWC gamma ray observatory is located at the Sierra Negra Volcano in
Puebla, Mexico, at an altitude of 4,100 meters. HAWC is a wide field of view
array of 300 water Cherenkov detectors that are continuously surveying ~ 2sr of
the sky, operating since March 2015. The large collected data sample allows
HAWC to perform an unbiased monitoring of the BL Lac Mrk 421. This is the
closest and brightest known extragalactic high-synchrotron-peaked BL Lac in the
gamma-ray/X- ray bands and is extensively monitored by the Large Area Telescope
(LAT) on-board the Fermi satellite, and the BAT and XRT instruments of the
Swift satellite. In this work, we use 25 months of HAWC data together with
Swift-XRT data to characterize potential correlations between both wavelengths.
This analysis shows that HAWC and Swift-XRT data are correlated even stronger
than expected for quasi-simultaneous observations.Comment: Presented at the 35th International Cosmic Ray Conference (ICRC2017),
Bexco, Busan, Korea. See arXiv:1708.02572 for all HAWC contribution
Structural Changes in the Transmission Mechanism of Monetary Policy in Mexico: A Non-linear VAR Approach
In this paper we present a first approach to the study of the transformation in the transmission mechanism of monetary policy that has taken place in Mexico in recent years. For this purpose, we use a non-linear VAR model that allows for regime shifts. The comparison of the different regimes identified leads to the following main findings: a) there was a major structural change in the transmission mechanism around January 2001, date that coincides with the formal adoption of the inflation targeting framework; b) after this change, fluctuations in the real exchange rate have had smaller effects on the process of price formation, the formation of inflation expectations and the nominal interest rate; c) also, there have been stronger reactions of the nominal interest rate to increases in the output gap and the rate of inflation; and d) the movements of the nominal interest rate have a more effective influence on the real exchange rate and the rate of inflation.Monetary policy, Mexico, Monetary transmission mechanism
Uncertainty about the Persistence of Cost-Push Shocks and the Optimal Reaction of the Monetary Authority.
In this paper we formalize the uncertainty about the persistence of cost-push shocks using an open economy optimal control model with Markov regime-switching and robust control. The latter is used in only one of the regimes producing relatively more persistent cost-push shocks in that regime. Conditional on being in the regime with relatively less persistence, we obtain two main results: a) underestimating the probability of switching to the regime with relatively more persistent cost-push shocks causes higher welfare losses than its overestimation; and b) the welfare losses associated with either underestimation or overestimation of such probability increase with the size of the penalty on inflation deviations from its target. Keywords: Model uncertainty, Robustness, Markov regime-switching, Monetary policy, Inflation targeting.Model uncertainty, Robustness, Markov regime-switching, Monetary policy, Inflation targeting
Rotating and counterrotating relativistic thin disks as sources of stationary electrovacuum spacetimes
A detailed study is presented of the counterrotating model (CRM) for
electrovacuum stationary axially symmetric relativistic thin disks of infinite
extension without radial stress, in the case when the eigenvalues of the
energy-momentum tensor of the disk are real quantities, so that there is not
heat flow. We find a general constraint over the counterrotating tangential
velocities needed to cast the surface energy-momentum tensor of the disk as the
superposition of two counterrotating charged dust fluids. We then show that, in
some cases, this constraint can be satisfied if we take the two counterrotating
tangential velocities as equal and opposite or by taking the two
counterrotating streams as circulating along electro-geodesics. However, we
show that, in general, it is not possible to take the two counterrotating
fluids as circulating along electro-geodesics nor take the two counterrotating
tangential velocities as equal and opposite. A simple family of models of
counterrotating charged disks based on the Kerr-Newman solution are considered
where we obtain some disks with a CRM well behaved. We also show that the disks
constructed from the Kerr-Newman solution can be interpreted, for all the
values of parameters, as a matter distribution with currents and purely
azimuthal pressure without heat flow. The models are constructed using the
well-known "displace, cut and reflect" method extended to solutions of vacuum
Einstein-Maxwell equations. We obtain, in all the cases, counterrotating
Kerr-Newman disks that are in agreement with all the energy conditions.Comment: 22 pages, 7 figures, Late
The effect of nature on designers' creativity, according to their personality profile
The aim of this work is to demonstrate whether natural environments, either real or simulated, tend to enhance designers' creativity, and whether the effects differ depending on their personality profile. Numerous studies have been conducted on the variables that shape the work environment and affect the designer's creativity, but few take into account the interaction between the work environment and the designer's personality profile. The aim of this study is to carry out a practical experiment in which a certain number of individuals solve conceptual design problems in different work environments, followed by an assessment of the creativity of the results. The results show higher values of creativity for both types of natural setting than in a neutral scenario. The personality of the designers determines whether the highest values are achieved in real or in artificial nature
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