4,411,231 research outputs found
Morphological characterization of a polymeric microfiltration membrane by synchrotron radiation computed microtomography
Most commercial polymeric membranes are prepared by phase inversion. The performance of the membranes depends greatly on the morphology of the porous structure formed during the
different steps of this process. Researchers in this field have found it extremely difficult to foresee how a change in the composition of the polymer solution will affect pore formation without a set of methods designed to yield detailed knowledge of the morphological structure.
This paper reports the new potential associated with X-Ray synchrotron microtomography to characterize the 3D structure of a PvDF hollow fibre microfiltration membrane prepared by phase inversion. 3D morphological data obtained from the ID19 line at the ESRF are presented. The membrane actually appears as a complex three-dimensional bi-continuum of interconnected pores. Within the hollow fibre structure, different regions with various
thicknesses and pore size distributions have been identified and well characterized.
Transversal views show the anisotropic finger-like structure of pores, while longitudinal
sections reveal a honeycomb structure which resembles the structure of highly concentrated water in oil emulsion or dispersion. This typical structure might be obtained during the phase inversion process. How the phase inversion process may result in these morphologies is finally discussed
Graphical Modeling for Multivariate Hawkes Processes with Nonparametric Link Functions
Hawkes (1971) introduced a powerful multivariate point process model of
mutually exciting processes to explain causal structure in data. In this paper
it is shown that the Granger causality structure of such processes is fully
encoded in the corresponding link functions of the model. A new nonparametric
estimator of the link functions based on a time-discretized version of the
point process is introduced by using an infinite order autoregression.
Consistency of the new estimator is derived. The estimator is applied to
simulated data and to neural spike train data from the spinal dorsal horn of a
rat.Comment: 20 pages, 4 figure
Nuclear shadowing in inclusive and tagged deuteron structure functions and extraction of F_2^p-F_2^n at small x from electron-deuteron collider data
We review predictions of the theory of leading twist nuclear shadowing for
inclusive unpolarized and polarized deuteron structure functions F_2^D, g_1^D
and b_1^D and for the tagged deuteron structure function F_2^D(x,Q^2,\vec{p}).
We analyze the possibility to extract the neutron structure function F_2^n from
electron-deuteron data and demonstrate that an account of leading twist nuclear
shadowing leads to large corrections for the extraction of F_2^n from the
future deuteron collider data both in the inclusive and in the tagged structure
function modes. We suggest several strategies to address the extraction of
F_2^n and to measure at the same time the effect of nuclear shadowing via the
measurement of the distortion of the proton spectator spectrum in the
semi-inclusive e D \to e^{\prime}NX process. We address the issue of the final
state interactions in the e D \to e^{\prime}NX process and examine how they
affect the extraction of F_2^n.Comment: 19 pages, 7 figures. Published in Mod. Phys. Lett.
An object-based classification approach for mapping "migrant housing" in the mega-urban area of the Pearl River Delta (China)
Urban areas develop on formal and informal levels. Informal development is often highly dynamic, leading to a lag of spatial information about urban structure types. In this work, an object-based remote sensing approach will be presented to map the migrant housing urban structure type in the Pearl River Delta, China. SPOT5 data were utilized for the classification (auxiliary data, particularly up-to-date cadastral data, were not available). A hierarchically structured classification process was used to create (spectral) independence from single satellite scenes and to arrive at a transferrable classification process. Using the presented classification approach, an overall classification accuracy of migrant housing of 68.0% is attained
Manganese ferrite thin films Part I: Preparation and structure
The preparation of manganese ferrite thin films by the reactive evaporation of oxidic materials is reported. The process is not critical and provides homogeneous mirror-like films with spinel structure. An annealing procedure below 750 °C has a strong influence on the properties of the films. Special attention is paid to the partial oxygen pressure during the annealing process. For this purpose data are collected from the literature concerning the equilibrium conditions of the spinel structure for varying manganese-iron contents. The lattice constant of the spinel structure of the films is determined by electron diffraction
Regge Analysis of Diffractive and Leading Baryon Structure Functions from DIS
In this paper we present a combined analysis of the H1 data on leading baryon
and diffractive structure functions from DIS, which are handled as two
components of the same semi-inclusive process. The available structure function
data are analyzed in a series of fits in which three main exchanges are taking
into account: pomeron, reggeon and pion. For each of these contributions, Regge
factorization of the correspondent structure function is assumed. By this
procedure, we extract information about the interface between the diffractive,
pomeron-dominated, region and the leading proton spectrum, which is mostly
ruled by secondary exchanges. One of the main results is that the relative
reggeon contribution to the semi-inclusive structure function is much smaller
than the one obtained from a analysis of the diffractive structure function
alone.Comment: ps file, 22 pages, 5 figures. Totally revised version with major
changes, to appear in Physical Review
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