10,655 research outputs found
Indirect effects of an aid program: how do liquidity injections affect non-eligibles' consumption?
Aid programs in developing countries are likely to affect both the treated and the non-treated households living in the targeted areas. Studies that focus on the treatment effecton the treated may fail to capture important spillover effects. We exploit the unique designof an aid program's experimental trial to identify its indirect effect on consumption for non-eligible households living in treated areas. We find that this effect is positive, and that itoccurs through changes in the insurance and credit markets: non-eligible households receivemore transfers, and borrow more when hit by a negative idiosyncratic shock, because of theprogram liquidity injection; thus they can reduce their precautionary savings. We also testfor general equilibrium effects in the local labor and goods markets; we find no significantchanges in labor income and prices, while there is a reduction in earnings from sales ofagricultural products, which are now consumed rather than sold. We show that this classof aid programs has important positive externalities; thus their overall effect is larger thanthe effect on the treated. Our results confirm that a key identifying assumption - that thetreatment has no effect on the non-treated - is likely to be violated in similar policy designs. Aid programs in developing countries are likely to affect both the treated and the non-treated households living in the targeted areas. Studies that focus on the treatment effecton the treated may fail to capture important spillover effects. We exploit the unique designof an aid program's experimental trial to identify its indirect effect on consumption for non-eligible households living in treated areas. We find that this effect is positive, and that itoccurs through changes in the insurance and credit markets: non-eligible households receivemore transfers, and borrow more when hit by a negative idiosyncratic shock, because of theprogram liquidity injection; thus they can reduce their precautionary savings. We also testfor general equilibrium effects in the local labor and goods markets; we find no significantchanges in labor income and prices, while there is a reduction in earnings from sales ofagricultural products, which are now consumed rather than sold. We show that this classof aid programs has important positive externalities; thus their overall effect is larger thanthe effect on the treated. Our results confirm that a key identifying assumption - that thetreatment has no effect on the non-treated - is likely to be violated in similar policy designs
Application of the inhomogeneous Lippmann-Schwinger equation to inverse scattering problems
In this paper we present a hybrid approach to numerically solve
two-dimensional electromagnetic inverse scattering problems, whereby the
unknown scatterer is hosted by a possibly inhomogeneous background. The
approach is `hybrid' in that it merges a qualitative and a quantitative method
to optimize the way of exploiting the a priori information on the background
within the inversion procedure, thus improving the quality of the
reconstruction and reducing the data amount necessary for a satisfactory
result. In the qualitative step, this a priori knowledge is utilized to
implement the linear sampling method in its near-field formulation for an
inhomogeneous background, in order to identify the region where the scatterer
is located. On the other hand, the same a priori information is also encoded in
the quantitative step by extending and applying the contrast source inversion
method to what we call the `inhomogeneous Lippmann-Schwinger equation': the
latter is a generalization of the classical Lippmann-Schwinger equation to the
case of an inhomogeneous background, and in our paper is deduced from the
differential formulation of the direct scattering problem to provide the
reconstruction algorithm with an appropriate theoretical basis. Then, the point
values of the refractive index are computed only in the region identified by
the linear sampling method at the previous step. The effectiveness of this
hybrid approach is supported by numerical simulations presented at the end of
the paper.Comment: accepted in SIAM Journal on Applied Mathematic
Village economies and the structure of extended family networks
This paper documents how the structure of extended family networks in rural Mexico relates to the poverty and inequality of the village of residence. Using the Hispanic naming convention, we construct within-village extended family networks in 504 poor rural villages. Family networks are larger (both in the number of members and as a share of the village population) and out-migration is lower the poorer and the less unequal the village of residence. Our results are consistent with the extended family being a source of informal insurance to its members
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
Quantum synchronization as a local signature of super- and subradiance
We study the relationship between the collective phenomena of super and
subradiance and spontaneous synchronization of quantum systems. To this aim we
revisit the case of two detuned qubits interacting through a pure dissipative
bosonic environment, which contains the minimal ingredients for our analysis.
By using the Liouville formalism, we are able to find analytically the ultimate
connection between these phenomena. We find that dynamical synchronization is
due to the presence of long standing coherence between the ground state of the
system and the subradiant state. We finally show that, under pure dissipation,
the emergence of spontaneous synchronization and of subradiant emission occur
on the same time scale. This reciprocity is broken in the presence of dephasing
noise.Comment: 12 pages, 6 figure
Quantum correlation dynamics in photosynthetic processes assisted by molecular vibrations
During the long course of evolution, nature has learnt how to exploit quantum
effects. In fact, recent experiments reveal the existence of quantum processes
whose coherence extends over unexpectedly long time and space ranges. In
particular, photosynthetic processes in light-harvesting complexes display a
typical oscillatory dynamics ascribed to quantum coherence. Here, we consider
the simple model where a dimer made of two chromophores is strongly coupled
with a quasi-resonant vibrational mode. We observe the occurrence of wide
oscillations of genuine quantum correlations, between electronic excitations
and the environment, represented by vibrational bosonic modes. Such a quantum
dynamics has been unveiled through the calculation of the negativity of
entanglement and the discord, indicators widely used in quantum information for
quantifying the resources needed to realize quantum technologies. We also
discuss the possibility of approximating additional weakly-coupled off-resonant
vibrational modes, simulating the disturbances induced by the rest of the
environment, by a single vibrational mode.
Within this approximation, one can show that the off-resonant bath behaves
like a classical source of noise
A semi-Lagrangian scheme for the game -Laplacian via -averaging
We present and analyze an approximation scheme for the two-dimensional game
-Laplacian in the framework of viscosity solutions. The approximation is
based on a semi-Lagrangian scheme which exploits the idea of -averages. We
study the properties of the scheme and prove that it converges, in particular
cases, to the viscosity solution of the game -Laplacian. We also present a
numerical implementation of the scheme for different values of ; the
numerical tests show that the scheme is accurate.Comment: 34 pages, 3 figures. To appear on Applied Numerical Mathematic
Power calculation for gravitational radiation: oversimplification and the importance of time scale
A simplified formula for gravitational-radiation power is examined. It is
shown to give completely erroneous answers in three situations, making it
useless even for rough estimates. It is emphasized that short timescales, as
well as fast speeds, make classical approximations to relativistic calculations
untenable.Comment: Three pages, no figures, accepted for publication in Astronomische
Nachrichte
Improving Computational Efficiency in WEC Design: Spectral-Domain Modelling in Techno-Economic Optimization
Wave energy converter (WEC) optimization often underlines incremental and iterative approaches that result in suboptimal solutions, since all the elements that concur with a techno-economical evaluation are optimized separately due to computation constraints. A design process should rely on precise WEC models to ensure high result accuracy while minimizing the computational demand. These conflicting objectives can be addressed with non-linear time-domain models, known to be numerically accurate, and frequency-domain models due to their high computational efficiency. This work pursues the development of an all-encompassing optimization tool for a gyroscopic-type WEC called ISWEC that applies a new modelling technique named spectral-domain technique as a substitution to the complex time-domain model previously employed. In particular, the spectral-domain technique provides accurate and fast performance predictions of the ISWEC system and offers the possibility to model a hydraulic power take-off, not representable in the frequency domain. The article illustrates techno-economic trends associated with an early-stage design of the ISWEC in high-energy sea-sites, where the low-speed and high-torque profiles call for the use of hydraulic transmissions as opposed to the old electro-mechanical transmissions. The design tool proposed could facilitate the development of WEC technologies via efficient and accurate power assessment and via the possibility of carrying out advanced techno-economic optimisation that goes beyond linear models
Experimental investigation of the mooring system of a wave energy converter in operating and extreme wave conditions
A proper design of the mooring systems for Wave Energy Converters (WECs) requires an accurate investigation of both operating and extreme wave conditions. A careful analysis of these systems is required to design a mooring configuration that ensures station keeping, reliability, maintainability, and low costs, without affecting the WEC dynamics. In this context, an experimental campaign on a 1:20 scaled prototype of the ISWEC (Inertial Sea Wave Energy Converter), focusing on the influence of the mooring layout on loads in extreme wave conditions, is presented and discussed. Two mooring configurations composed of multiple slack catenaries with sub-surface buoys, with or without clump-weights, have been designed and investigated experimentally. Tests in regular, irregular, and extreme waves for a moored model of the ISWEC device have been performed at the University of Naples Federico II. The aim is to identify a mooring solution that could guarantee both correct operation of the device and load carrying in extreme sea conditions. Pitch motion and loads in the rotational joint have been considered as indicators of the device hydrodynamic behavior and mooring configuration impact on the WEC
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