6,680 research outputs found
Family networks and school enrolment: evidence from a randomized social experiment
We present evidence on whether and how a householdâs behavior is influenced by the
presence and characteristics of its extended family. Using data from the PROGRESA
program in Mexico, we exploit information on the paternal and maternal surnames of
heads and spouses in conjunction with the Spanish naming convention to identify the inter
and intra generational family links of each household to others in the same village. We
then exploit the randomized research design of the PROGRESA evaluation data to identify
whether the treatment effects of PROGRESA transfers on secondary school enrolment
vary according to the characteristics of extended family. We find PROGRESA only raises
secondary enrolment among households that are embedded in a family network. Eligible
but isolated households do not respond. The mechanism through which the extended
family influences household schooling choices is the redistribution of resources within
the family network from eligibles that receive de facto unconditional cash transfers from
PROGRESA, towards eligibles on the margin of enrolling children into secondary school
Effective Hamiltonian for a half-filled asymmetric ionic Hubbard chain with alternating on-site interaction
We derive an effective spin Hamiltonian for the one-dimensional half-filled asymmetric ionic Hubbard model (IHM) with alternating on-site interaction in the limit of strong repulsion. It is shown that the effective Hamiltonian is that of a spin S = 1/2 anisotropic XXZ Heisenberg chain with alternating next-nearest-neighbor (NNN) and three-spin couplings in the presence of a uniform and a staggered magnetic field
Radiative emission of solar features in Ca II K
We investigated the radiative emission of different types of solar features
in the spectral range of the Ca II K line.
We analyzed full-disk 2k x 2k observations from the PSPT Precision Solar
Photometric Telescope. The data were obtained by using three narrow-band
interference filters that sample the Ca II K line with different pass bands.
Two filters are centered in the line core, the other in the red wing of the
line. We measured the intensity and contrast of various solar features,
specifically quiet Sun (inter-network), network, enhanced network, plage, and
bright plage (facula) regions. Moreover, we compared the results obtained with
those derived from the numerical synthesis performed for the three PSPT filters
with a widely used radiative code on a set of reference semi-empirical
atmosphere models.Comment: In Proceedings of the 25th NSO Workshop: Chromospheric Structure and
Dynamic
Steady states analysis and exponential stability of an extensible thermoelastic system
In this work we consider a nonlinear model for the vibrations of a thermoelastic beam with fixed ends resting on an elastic foundation. The behavior of the related dissipative system accounts for both the midplane stretching of the beam and the Fourier heat conduction. The nonlinear term enters the motion equation, only, while the dissipation is entirely contributed by the heat equation. Under stationary axial load and uniform external temperature the problem uncouples and the bending equilibria of the beam satisfy a semilinear equation. For a general axial load , the existence of a finite/infinite set of steady states is proved and buckling occurrence is discussed. Finally, long-term dynamics of solutions and exponential stability of the straight position are scrutinized
On some nonlinear models for suspension bridges
In this paper we discuss some mathematical models describing the nonlinear vibrations of different kinds of single-span simply supported suspension bridges and we summarize some results about the longtime behavior of solutions to the related evolution problems. Finally, in connection with the static counterpart of a general string-beam nonlinear model, we present some original results concerning the existence of multiple buckled solutions
Plasma flows and magnetic field interplay during the formation of a pore
We studied the formation of a pore in AR NOAA 11462. We analysed data
obtained with the IBIS at the DST on April 17, 2012, consisting of full Stokes
measurements of the Fe I 617.3 nm lines. Furthermore, we analysed SDO/HMI
observations in the continuum and vector magnetograms derived from the Fe I
617.3 nm line data taken from April 15 to 19, 2012. We estimated the magnetic
field strength and vector components and the LOS and horizontal motions in the
photospheric region hosting the pore formation. We discuss our results in light
of other observational studies and recent advances of numerical simulations.
The pore formation occurs in less than 1 hour in the leading region of the AR.
The evolution of the flux patch in the leading part of the AR is faster (< 12
hour) than the evolution (20-30 hour) of the more diffuse and smaller scale
flux patches in the trailing region. During the pore formation, the ratio
between magnetic and dark area decreases from 5 to 2. We observe strong
downflows at the forming pore boundary and diverging proper motions of plasma
in the vicinity of the evolving feature that are directed towards the forming
pore. The average values and trends of the various quantities estimated in the
AR are in agreement with results of former observational studies of steady
pores and with their modelled counterparts, as seen in recent numerical
simulations of a rising-tube process. The agreement with the outcomes of the
numerical studies holds for both the signatures of the flux emergence process
(e.g. appearance of small-scale mixed polarity patterns and elongated granules)
and the evolution of the region. The processes driving the formation of the
pore are identified with the emergence of a magnetic flux concentration and the
subsequent reorganization of the emerged flux, by the combined effect of
velocity and magnetic field, in and around the evolving structure.Comment: Accepted for publication in Astronomy and Astrophysic
Asymptotic dynamics of nonlinear coupled suspension bridge equations
In this paper we study the long-term dynamics of a doubly nonlinear abstract system which involves a single differential operator to different powers. For a special choice of the nonlinear terms, the system describes the motion of a suspension bridge where the road bed and the main cable are modeled as a nonlinear beam and a vibrating string, respectively, and their coupling is carried out by nonlinear springs. The set of stationary solutions turns out to be nonempty and bounded. As the external loads vanish, the null solution of the system is proved to be exponentially stable provided that the axial load does not exceed some critical value. Finally, we prove the existence of a bounded global attractor of optimal regularity in connection with an arbitrary axial load and quite general nonlinear terms
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