1,216 research outputs found
Simultaneous 3D measurement of the translation and rotation of finite size particles and the flow field in a fully developed turbulent water flow
We report a novel experimental technique that measures simultaneously in
three dimensions the trajectories, the translation, and the rotation of finite
size inertial particles together with the turbulent flow. The flow field is
analyzed by tracking the temporal evolution of small fluorescent tracer
particles. The inertial particles consist of a super-absorbent polymer that
renders them index and density matched with water and thus invisible. The
particles are marked by inserting at various locations tracer particles into
the polymer. Translation and rotation, as well as the flow field around the
particle are recovered dynamically from the analysis of the marker and tracer
particle trajectories. We apply this technique to study the dynamics of
inertial particles much larger in size (Rp/{\eta} \approx 100) than the
Kolmogorov length scale {\eta} in a von K\'arm\'an swirling water flow
(R{\lambda} \approx 400). We show, using the mixed (particle/fluid) Eulerian
second order velocity structure function, that the interaction zone between the
particle and the flow develops in a spherical shell of width 2Rp around the
particle of radius Rp. This we interpret as an indication of a wake induced by
the particle. This measurement technique has many additional advantages that
will make it useful to address other problems such as particle collisions,
dynamics of non-spherical solid objects, or even of wet granular matter.Comment: 18 pages, 7 figures, submitted to "Measurement Science and
Technology" special issue on "Advances in 3D velocimetry
Turbulence attenuation by large neutrally buoyant particles
Turbulence modulation by inertial-range-size, neutrally-buoyant particles is
investigated experimentally in a von K\'arm\'an flow. Increasing the particle
volume fraction , maintaining constant impellers Reynolds
number attenuates the fluid turbulence. The inertial-range energy transfer rate
decreases as , suggesting that only particles
located on a surface affect the flow. Small-scale turbulent properties, such as
structure functions or acceleration distribution, are unchanged. Finally,
measurements hint at the existence of a transition between two different
regimes occurring when the average distance between large particles is of the
order of the thickness of their boundary layers.Comment: 7 pages, 4 figure
Naphthalene Adsorption on 13X Molecular Sieve
In this paper, naphthalene adsorption on 13X molecular sieve has been investigated. The isotherms and the net heat of adsorption have been determined in the range between 40 °C and 380 °C. Analysis of the results clearly indicates that the Dubinin-Radushkevitch model provides the best fitting equation for data points, with a specific limitation due to some steric hindrance effect
Coupling between aging and convective motion in a colloidal glass of Laponite
We study thermal convection in a colloidal glass of Laponite in formation.
Low concentration preparation are submitted to destabilizing vertical
temperature gradient, and present a gradual transition from a turbulent
convective state to a steady conductive state as their viscosity increases. The
time spent under convection is found to depend strongly on sample
concentration, decreasing exponentially with mass fraction of colloidal
particles. Moreover, at fixed concentration, it also depends slightly on the
pattern selected by the Rayleigh B\'{e}nard instability: more rolls maintain
the convection state longer. This behavior can be interpreted with recent
theoretical approaches of soft glassy material rheology.Comment: Eur. Phys. J. B 55, 101-107 (2007) The original publication is
available at http://www.springerlink.co
Integrating clinicians, knowledge and data: expert-based cooperative analysis in healthcare decision support
<p>Abstract</p> <p>Background</p> <p>Decision support in health systems is a highly difficult task, due to the inherent complexity of the process and structures involved.</p> <p>Method</p> <p>This paper introduces a new hybrid methodology <it>Expert-based Cooperative Analysis </it>(EbCA), which incorporates explicit prior expert knowledge in data analysis methods, and elicits implicit or tacit expert knowledge (IK) to improve decision support in healthcare systems. EbCA has been applied to two different case studies, showing its usability and versatility: 1) Bench-marking of small mental health areas based on technical efficiency estimated by <it>EbCA-Data Envelopment Analysis (EbCA-DEA)</it>, and 2) Case-mix of schizophrenia based on functional dependency using <it>Clustering Based on Rules (ClBR)</it>. In both cases comparisons towards classical procedures using qualitative explicit prior knowledge were made. Bayesian predictive validity measures were used for comparison with expert panels results. Overall agreement was tested by Intraclass Correlation Coefficient in case "1" and kappa in both cases.</p> <p>Results</p> <p>EbCA is a new methodology composed by 6 steps:. 1) Data collection and data preparation; 2) acquisition of "Prior Expert Knowledge" (PEK) and design of the "Prior Knowledge Base" (PKB); 3) PKB-guided analysis; 4) support-interpretation tools to evaluate results and detect inconsistencies (here <it>Implicit Knowledg </it>-IK- might be elicited); 5) incorporation of elicited IK in PKB and repeat till a satisfactory solution; 6) post-processing results for decision support. EbCA has been useful for incorporating PEK in two different analysis methods (DEA and Clustering), applied respectively to assess technical efficiency of small mental health areas and for case-mix of schizophrenia based on functional dependency. Differences in results obtained with classical approaches were mainly related to the IK which could be elicited by using EbCA and had major implications for the decision making in both cases.</p> <p>Discussion</p> <p>This paper presents EbCA and shows the convenience of completing classical data analysis with PEK as a mean to extract relevant knowledge in complex health domains. One of the major benefits of EbCA is iterative elicitation of IK.. Both explicit and tacit or implicit expert knowledge are critical to guide the scientific analysis of very complex decisional problems as those found in health system research.</p
Organic-rich shales from internal Betic basins (SE Spain) : potential source rocks analogs for the pre-Messinian Salt play in the western Mediterranean
Southeastern Spain has a large number of Late Neogene basins with substantial evaporitic deposits that developed under an overall NNW-SSE compressional regime related to the African-European tectonic plates collision. Located in the Betic Cordillera, they can be considered as marginal Mediterranean basins that became gradually isolated during the Tortonian and Early Messinian due to tectonic uplift. Different evaporitic units accumulated in these basins during isolation and, in several cases, evaporitic conditions were associated to episodes of important organic matter accumulation. Results obtained from Late Tortonian to Early Messinian shales collected from boreholes, mines and outcrops in the internal Betic basins of Las Minas de HellĂn, Cenajo and Socovos are presented. The organic matter was studied under fluorescence and scanning electron microscopy (SEM), and the main geochemical characteristics defined. They show a relation between organic-rich intervals with high potential of hydrocarbon generation, native sulfur, bio-induced dolomite and evaporitic deposits. These organicrich shales can be found before, during and after the evaporitic episodes. Results from the present study are compared with those previously obtained in the pre-evaporitic deposits of the Lorca Basin that showed high oil generation potential, a restricted-marine origin of the organic matter and a low degree of maturity. The occurrence of such potential source rocks in several basins points to a broad regional distribution. At a larger scale, in the Mediterranean Basin, organic-rich sediments were deposited before and during the Messinian Salinity Crisis. The studied examples could represent analogs for potential source rocks of the pre-Messinian salt play in the Western Mediterranea
Phenotypic plasticity of body pigmentation in Drosophila: correlated variations between segments
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