957 research outputs found
Patterns of childbearing in Russia 1994 - 1998
In this paper we analyze the determinants of births in Russia in the 1990s and the changes in their effects since the 1980s and factors influencing fertility intentions in the 1990s. In the first part, based on the current social and economic situation in Russia, specific hypotheses for different parities (realized and intended fertility) are developed and subsequently tested by using logistic regression methods. On the basis of the Russian Longitudinal Monitoring Survey (RLMS) we find that the social differentiation that took place in Russia in the 1990s resulted in an increasing importance of economic conditions for a first, second or third birth. The same applies to parity-specific intentions.
Gaussian process hyper-parameter estimation using parallel asymptotically independent Markov sampling
Gaussian process emulators of computationally expensive computer codes
provide fast statistical approximations to model physical processes. The
training of these surrogates depends on the set of design points chosen to run
the simulator. Due to computational cost, such training set is bound to be
limited and quantifying the resulting uncertainty in the hyper-parameters of
the emulator by uni-modal distributions is likely to induce bias. In order to
quantify this uncertainty, this paper proposes a computationally efficient
sampler based on an extension of Asymptotically Independent Markov Sampling, a
recently developed algorithm for Bayesian inference. Structural uncertainty of
the emulator is obtained as a by-product of the Bayesian treatment of the
hyper-parameters. Additionally, the user can choose to perform stochastic
optimisation to sample from a neighbourhood of the Maximum a Posteriori
estimate, even in the presence of multimodality. Model uncertainty is also
acknowledged through numerical stabilisation measures by including a nugget
term in the formulation of the probability model. The efficiency of the
proposed sampler is illustrated in examples where multi-modal distributions are
encountered. For the purpose of reproducibility, further development, and use
in other applications the code used to generate the examples is freely
available for download at https://github.com/agarbuno/paims_codesComment: Computational Statistics \& Data Analysis, Volume 103, November 201
Thermoelectric and Magnetothermoelectric Transport Measurements of Graphene
The conductance and thermoelectric power (TEP) of graphene is simultaneously
measured using microfabricated heater and thermometer electrodes. The sign of
the TEP changes across the charge neutrality point as the majority carrier
density switches from electron to hole. The gate dependent conductance and TEP
exhibit a quantitative agreement with the semiclassical Mott relation. In the
quantum Hall regime at high magnetic field, quantized thermopower and Nernst
signals are observed and are also in agreement with the generalized Mott
relation, except for strong deviations near the charge neutrality point
Diameter Dependence of the Transport Properties of Antimony Telluride Nanowires
We report measurements of electronic, thermoelectric, and galvanomagnetic
properties of individual single crystal antimony telluride (Sb2Te3) nanowires
with diameters in the range of 20-100 nm. Temperature dependent resistivity and
thermoelectric power (TEP) measurements indicate hole dominant diffusive
thermoelectric generation, with an enhancement of the TEP for smaller diameter
wires up to 110 uV/K at T = 300 K. We measure the magnetoresistance, in
magnetic fields both parallel and perpendicular to the nanowire [110] axis,
where strong anisotropic positive magnetoresistance behavior was observed
A combined Raman lidar for low tropospheric studies
One of the main goals of laser sensing of the atmosphere was the development of techniques and facilities for remote determination of atmospheric meteorological and optical parameters. Of lidar techniques known at present the Raman-lidar technique occupies a specific place. On the one hand Raman lidar returns due to scattering on different molecular species are very simple for interpretation and for extracting the information on the atmospheric parameters sought, but, on the other hand, the performance of these techniques in a lidar facility is overburdened with some serious technical difficulties due to extremely low cross sections of Raman effect. Some results of investigations into this problem is presented which enables the construction of a combined Raman lidar capable of acquiring simultaneously the profiles of atmospheric temperature, humidity, and some optical characteristics in the ground atmospheric layer up to 1 km height. The operation of this system is briefly discussed
Optical models of the molecular atmosphere
The use of optical and laser methods for performing atmospheric investigations has stimulated the development of the optical models of the atmosphere. The principles of constructing the optical models of molecular atmosphere for radiation with different spectral composition (wideband, narrowband, and monochromatic) are considered in the case of linear and nonlinear absorptions. The example of the development of a system which provides for the modeling of the processes of optical-wave energy transfer in the atmosphere is presented. Its physical foundations, structure, programming software, and functioning were considered
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