2,995 research outputs found
Using parallel computation to improve Independent Metropolis--Hastings based estimation
In this paper, we consider the implications of the fact that parallel
raw-power can be exploited by a generic Metropolis--Hastings algorithm if the
proposed values are independent. In particular, we present improvements to the
independent Metropolis--Hastings algorithm that significantly decrease the
variance of any estimator derived from the MCMC output, for a null computing
cost since those improvements are based on a fixed number of target density
evaluations. Furthermore, the techniques developed in this paper do not
jeopardize the Markovian convergence properties of the algorithm, since they
are based on the Rao--Blackwell principles of Gelfand and Smith (1990), already
exploited in Casella and Robert (1996), Atchade and Perron (2005) and Douc and
Robert (2010). We illustrate those improvements both on a toy normal example
and on a classical probit regression model, but stress the fact that they are
applicable in any case where the independent Metropolis-Hastings is applicable.Comment: 19 pages, 8 figures, to appear in Journal of Computational and
Graphical Statistic
Comments on "Particle Markov chain Monte Carlo" by C. Andrieu, A. Doucet, and R. Hollenstein
This is the compilation of our comments submitted to the Journal of the Royal
Statistical Society, Series B, to be published within the discussion of the
Read Paper of Andrieu, Doucet and Hollenstein.Comment: 7 pages, 4 figure
Influence of Attitude, School Facilities and Teacher Characteristics on the Performance of Secondary School Teachers Working in Rural Areas
The successful running of any education system depends upon the teacher, the pupil, the curriculum and the facilities. Teacher is the most important one and the pivot on whom the entire educational structure rests. For many teachers this is earnestly to be hoped; with regard to others, it is a despairing thought. It seems reasonable to assume that good teachers – those who are skilful in developing understanding of the world in which man lives, in rightful with respect to the ways and means of stimulating intellectual appetites and capable of patience, understanding and sincere feelings for others – may pave the way for an enlightened and productive society. Poor teaching – contrariwise would seem to be significant contributor of its unfortunate share to the perpetuation of ignorance, misunderstanding and intellectual and cultural stagnation. A teacher who is considered to be competent i.e. possessing all the desirable / required characteristics and attitude may also fail to perform his duties to the expected level. A competent teacher who works in a congenial atmosphere having all the facilities a standard school requires, stands a better chance of giving an amazing performance than a teacher who is equally competent but short of such a school atmosphere and school facilities. The secondary school education is a critical phase, as it is preparatory time for higher education or for vocational training. Moreover the pupils will be in their adolescence which is viewed as a crucial stage in their lives. The efficient teachers are essential during this period. Efficient teaching depends upon attitude, school facilities and teacher characteristics to some extent. Keeping this in view, the present investigation is proposed to study the influence of attitude, school facilities and teacher characteristics on the performance of teachers working in secondary schools located in rural areas of Visakhapatnam district, Andhra Pradesh State
Discussions on "Riemann manifold Langevin and Hamiltonian Monte Carlo methods"
This is a collection of discussions of `Riemann manifold Langevin and
Hamiltonian Monte Carlo methods" by Girolami and Calderhead, to appear in the
Journal of the Royal Statistical Society, Series B.Comment: 6 pages, one figur
On parameter estimation with the Wasserstein distance
Statistical inference can be performed by minimizing, over the parameter
space, the Wasserstein distance between model distributions and the empirical
distribution of the data. We study asymptotic properties of such minimum
Wasserstein distance estimators, complementing results derived by Bassetti,
Bodini and Regazzini in 2006. In particular, our results cover the misspecified
setting, in which the data-generating process is not assumed to be part of the
family of distributions described by the model. Our results are motivated by
recent applications of minimum Wasserstein estimators to complex generative
models. We discuss some difficulties arising in the approximation of these
estimators and illustrate their behavior in several numerical experiments. Two
of our examples are taken from the literature on approximate Bayesian
computation and have likelihood functions that are not analytically tractable.
Two other examples involve misspecified models.Comment: 29 pages (+18 pages of appendices), 6 figures. To appear in
Information and Inference: A Journal of the IMA. A previous version of this
paper contained work on approximate Bayesian computation with the Wasserstein
distance, which can now be found at arxiv:1905.0374
Optimal non-circular fiber geometries for image scrambling in high-resolution spectrographs
Optical fibers are a key component for high-resolution spectrographs to
attain high precision in radial velocity measurements. We present a custom
fiber with a novel core geometry - a 'D'-shape. From a theoretical standpoint,
such a fiber should provide superior scrambling and modal noise mitigation,
since unlike the commonly used circular and polygonal fiber cross sections, it
shows chaotic scrambling. We report on the fabrication process of a test fiber
and compare the optical properties, scrambling performance, and modal noise
behavior of the D-fiber with those of common polygonal fibers.Comment: 7 pages, 6 figures, submitted to SPIE Astronomical Telescopes &
Instrumentation 2016 (9912-192
Experimental investigation of cut-off phenomena in non-linear photonic crystal fibers
The modal cut-off is investigated experimentally in a series of high quality
non-linear photonic crystal fibers. We demonstrate a suitable measurement
technique to determine the cut-off wavelength and verify it by inspecting the
near field of the modes that may be excited below and above the cut-off. We
observe a double peak structure in the cut-off spectra, which is attributed to
a splitting of the higher order modes. The cut-off is measured for seven
different fiber geometries with different pitches and relative hole size, and a
very good agreement with recent theoretical work is found.Comment: 3 pages including 1 table and 4 figures. Accepted for Optics Letter
Aviram-Ratner rectifying mechanism for DNA base pair sequencing through graphene nanogaps
We demonstrate that biological molecules such as Watson-Crick DNA base pairs
can behave as biological Aviram-Ratner electrical rectifiers because of the
spatial separation and weak hydrogen bonding between the nucleobases. We have
performed a parallel computational implementation of the ab-initio
non-equilibrium Green's function (NEGF) theory to determine the electrical
response of graphene---base-pair---graphene junctions. The results show an
asymmetric (rectifying) current-voltage response for the Cytosine-Guanine base
pair adsorbed on a graphene nanogap. In sharp contrast we find a symmetric
response for the Thymine-Adenine case. We propose applying the asymmetry of the
current-voltage response as a sensing criterion to the technological challenge
of rapid DNA sequencing via graphene nanogaps
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