5,962 research outputs found
Domain structure in the monoclinic Pm phase of Pb(Mg1/3Nb2/3)O3 - PbTiO3 single crystals
The domain structure of (1-x)Pb(Mg1/3Nb2/3)O3- xPbTiO3 single crystals with
composition x ~ 0.33 in the range of the morphotropic phase boundary (MPB) was
studied. Based on the analysis of spontaneous strain compatibility and charge
of domain walls, we have established the permissible domain arrangements for
the ferroelectric phases of different symmetry, which are expected to occur in
the range of the MPB. Examination of (001)-oriented unpoled and electrically
poled (along the [001] direction) crystal plates in polarizing microscope
reveals a monophase state with the domain structure compatible with the
structure theoretically predicted for the Mc monoclinic phase (space group Pm),
which was recently discovered in the compositions close to the MPB by x-ray and
neutron diffraction studies. In the unpoled crystal the 180 deg. walls between
the domains whose spontaneous polarization vectors are parallel to the plane of
the crystal plate (i.e. a-domains) are observed. The domain structure of the
poled crystal is predominantly composed of crystallographically prominent Wf
walls parallel to (001) (i.e. the plane of the crystal plate) and inclined S
walls parallel to [110] or [1-10] direction. In poled and unpoled samples the
optical rotatory polarization effect is found, which is related to the
inhomogeneity of the sample resulting from the mixture of domains.Comment: PDF file, 30 pages, 15 figures (3 in color) collected on pp.18-3
Transport properties of dense deuterium-tritium plasmas
Consistent descriptions of the equation of states, and information about
transport coefficients of deuterium-tritium mixture are demonstrated through
quantum molecular dynamic (QMD) simulations (up to a density of 600 g/cm
and a temperature of eV). Diffusion coefficients and viscosity are
compared with one component plasma model in different regimes from the strong
coupled to the kinetic one. Electronic and radiative transport coefficients,
which are compared with models currently used in hydrodynamic simulations of
inertial confinement fusion, are evaluated up to 800 eV. The Lorentz number is
also discussed from the highly degenerate to the intermediate region.Comment: 4 pages, 3 figure
Simple analytical expression for crosstalk estimation in homogeneous trench-assisted multi-core fibers
carat: An R Package for Covariate-Adaptive Randomization in Clinical Trials
Covariate-adaptive randomization is gaining popularity in clinical trials because they enable the generation of balanced allocations with respect to covariates. Over the past decade, substantial progress has been made in both new innovative randomization procedures and the theoretical properties of associated inferences. However, these results are scattered across the literature, and a single tool kit does not exist for use by clinical trial practitioners and researchers to conduct and evaluate these methods. The R package carat is proposed to address this need. It facilitates a broad range of covariate-adaptive randomization and testing procedures, such as the most common and classical methods, and also reflects recent developments in the field. The package contains comprehensive evaluation and comparison tools for use in both randomization procedures and tests. This enables power analysis to be conducted to assist the planning of a covariate-adaptive clinical trial. The package also implements a command-line interface to allow for an interactive allocation procedure, which is typically the case in real-world applications. In this paper, the features and functionalities of carat are presented
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