3,929 research outputs found
Measuring and explaining farm inefficiency in a panel data set of mixed farms
This paper aims to estimate a translog stochastic frontier production function in the analysis of a panel of 150 mixed Catalan farms in the period 1989-1993, in order to attempt to measure and explain variation in technical inefficiency scores with a one-stage approach. The model uses gross value added as the output aggregate measure. Total employment, fixed capital, current assets, specific costs and overhead costs are introduced into the model as inputs. Stochastic frontier estimates are compared with those obtained using a linear programming method using a two-stage approach. The specification of the translog stochastic frontier model appears as an appropriate representation of the data, technical change was rejected and the technical inefficiency effects were statistically significant. The mean technical efficiency in the period analyzed was estimated to be 64.0%. Farm inefficiency levels were found significantly at 5% level and positively correlated with the number of economic size units.Technical efficiency, stochastic frontier approach, agricultural economics, frontier productions, farm efficiency
Gravity in the Randall-Sundrum Brane World
We discuss the weak gravitational field created by isolated matter sources in
the Randall-Sundrum brane-world. In the case of two branes of opposite tension,
linearized Brans-Dicke (BD) gravity is recovered on either wall, with different
BD parameters. On the wall with positive tension the BD parameter is larger
than 3000 provided that the separation between walls is larger than 4 times the
AdS radius. For the wall of negative tension, the BD parameter is always
negative but greater than -3/2. In either case, shadow matter from the other
wall gravitates upon us. For equal Newtonian mass, light deflection from shadow
matter is 25 % weaker than from ordinary matter. Hence, the effective mass of a
clustered object containing shadow dark matter would be underestimated if
naively measured through its lensing effect. For the case of a single wall of
positive tension, Einstein gravity is recovered on the wall to leading order,
and if the source is stationary the field stays localized near the wall. We
calculate the leading Kaluza-Klein corrections to the linearized gravitational
field of a non-relativistic spherical object and find that the metric is
different from the Schwarzschild solution at large distances. We believe that
our linearized solution corresponds to the field far from the horizon after
gravitational collapse of matter on the brane.Comment: 8 pages, 1 figure. Replaced with revised version to be published in
Phys. Rev. Lett. Some comments adde
Spatiotemporal Stacked Sequential Learning for Pedestrian Detection
Pedestrian classifiers decide which image windows contain a pedestrian. In
practice, such classifiers provide a relatively high response at neighbor
windows overlapping a pedestrian, while the responses around potential false
positives are expected to be lower. An analogous reasoning applies for image
sequences. If there is a pedestrian located within a frame, the same pedestrian
is expected to appear close to the same location in neighbor frames. Therefore,
such a location has chances of receiving high classification scores during
several frames, while false positives are expected to be more spurious. In this
paper we propose to exploit such correlations for improving the accuracy of
base pedestrian classifiers. In particular, we propose to use two-stage
classifiers which not only rely on the image descriptors required by the base
classifiers but also on the response of such base classifiers in a given
spatiotemporal neighborhood. More specifically, we train pedestrian classifiers
using a stacked sequential learning (SSL) paradigm. We use a new pedestrian
dataset we have acquired from a car to evaluate our proposal at different frame
rates. We also test on a well known dataset: Caltech. The obtained results show
that our SSL proposal boosts detection accuracy significantly with a minimal
impact on the computational cost. Interestingly, SSL improves more the accuracy
at the most dangerous situations, i.e. when a pedestrian is close to the
camera.Comment: 8 pages, 5 figure, 1 tabl
The Impact of the Post-Liberalisation Growth of LCCs on the Tourism Trends in Spain
This paper describes the basic characteristics of low cost companies (LCCs) and their expansion in Spain, one of the most popular tourist destinations in the world according to the World Tourism Organization. Using a demand perspective, the evolution of LCCs and the main implications for the tourism marked between 2000 and 2005 are analysed. The evident tendency of Low-Cost companies towards a marked growth in the number of passengers is contrasted with the evident stagnation of traditional or full service companies. The results of the analysis also show that highly significant trends related to the development of LCCs include the growing use of the Internet as an information search engine and tool for booking and paying for tourist services, the substitution of traditional holiday packages (travel and transport) for direct booking systems and a reduction in the length of stays at a destination.
"The connection between distortion risk measures and ordered weighted averaging operators"
Distortion risk measures summarize the risk of a loss distribution by means of a single value. In fuzzy systems, the Ordered Weighted Averaging (OWA) and Weighted Ordered Weighted Averaging (WOWA) operators are used to aggregate a large number of fuzzy rules into a single value. We show that these concepts can be derived from the Choquet integral, and then the mathematical relationship between distortion risk measures and the OWA and WOWA operators for discrete and nite random variables is presented. This connection oers a new interpretation of distortion risk measures and, in particular, Value-at-Risk and Tail Value-at-Risk can be understood from an aggregation operator perspective. The theoretical results are illustrated in an example and the degree of orness concept is discussed.Fuzzy systems; Degree of orness; Risk quantification; Discrete random variable JEL classification:C02,C60
Frequency dynamics of gain-switched injection-locked semiconductor lasers
The frequency dynamics of gain-switched singlemode semiconductor lasers subject to optical injection is investigated. The requirements for low time jitter and reduced frequency chirp operation are studied as a function of the frequency mismatch between the master and slave lasers. Suppression of the power overshoot, typical during gain-switched operation, can be achieved for selected frequency detunings
The resonant damping of fast magnetohydrodynamic oscillations in a system of two coronal slabs
Observations of transversal coronal loop oscillations very often show the
excitation and damping of oscillations in groups of coronal loops rather than
in individual and isolated structures. We present results on the oscillatory
properties (periods, damping rates, and spatial distribution of perturbations)
for resonantly damped oscillations in a system of two inhomogeneous coronal
slabs and compare them to the properties found in single slab loop models. A
system of two identical coronal loops is modeled, in Cartesian geometry, as
being composed by two density enhancements. The linear magnetohydrodynamic
(MHD) wave equations for oblique propagation of waves are solved and the
damping of the different solutions, due to the transversal inhomogeneity of the
density profile, is computed. The physics of the obtained results is analyzed
by an examination of the perturbed physical variables. We find that, due to the
interaction between the loops, the normal modes of oscillation present in a
single slab split into symmetric and antisymmetric oscillations when a system
of two identical slabs is considered. The frequencies of these solutions may
differ from the single slab results when the distance between the loops is of
the order of a few slab widths. Oblique propagation of waves weakens this
interaction, since solutions become more confined to the edges of the slabs.
The damping is strong for surface-like oscillations, while sausage body-like
solutions are unaffected. For some solutions, and small slab separations, the
damping in a system of two loops differs substantially from the damping of a
single loop.Comment: 25 pages, 9 figure
- …