Statistical Distribution Of Particles Research Articles

Evaluation of shear stress accumulation on blood components in normal and dysfunctional bileaflet mechanical heart valves using smoothed particle hydrodynamics

Evaluating shear induced hemodynamic complications is one of the major concerns in design of the mechanical heart valves (MHVs). The monitoring of these events relies on both numerical simulations and experimental measurements. Currently, numerical approaches are mainly based on a combined Eulerian–Lagrangian approach. A more straightforward evaluation can be based on the Lagrangian analysis of the whole blood. As a consequence, Lagrangian meshfree methods are more adapted to such evaluation. In this study, smoothed particle hydrodynamics (SPH), a fully meshfree particle method originated to simulate compressible astrophysical flows, is applied to study the flow through a normal and a dysfunctional bileaflet mechanical heart valves (BMHVs). The SPH results are compared with the reference data. The accumulation of shear stress patterns on blood components illustrates the important role played by non-physiological flow patterns and mainly vortical structures in this issue. The statistical distribution of particles with respect to shear stress loading history provides important information regarding the relative number of blood components that can be damaged. This can be used as a measure of the response of blood components to the presence of the valve implant or any implantable medical device. This work presents the first attempt to simulate pulsatile flow through BMHVs using SPH method.

INVESTIGATION OF LIGHT SCATTERING AND DYNAMIC PROGRESS IN SOLUTION USING A NEAR-FIELD OPTICAL MICROSCOPE

The local near-field light scattering and the series dynamic progress of dyestuff PAN particles in solution were investigated taking advantage of optical fiber probe and the near-field detection techniques, including the dissolving and crystallizing progress, Brownian movement and the statistical distribution of particles. Some useful and interesting results were obtained, and are in good agreement with the theoretical analysis. These findings will contribute to the research of near-field optics in a liquid environment as well as provide direct and valuable results for statistical physics.

Stochastic dose estimation for inhaled particulates

The inherent variability of morphological and physiological parameters can cause significant statistical variations in the deposition patterns of inhaled particles in the human lungs. From a dosimetric point of view, the two major sources of variability are (i) the statistical distribution of particles deposited among all airways in a given generation, caused by the biological variability of the lung structure, and (ii) the local distribution of particles deposited within a given airway bifurcation resulting from the inhomogeneity of flow patterns and associated deposition mechanisms. Due to the stochastic nature of particle transport within the lungs in general, and within airway bifurcations in particular, this variability can be described mathematically by stochastic models. In addition to average values, stochastic models also provide information about the statistical distributions of deposition patterns, reflecting intra- and intersubject variability in particle deposition.

Modeling Ductile Fracture of Al Alloys in Relation with Statistical Distribution of Second Phase Particles

Fracture toughness tests have been carried out on two Al alloys (7075 and 7475) containing different amounts of Fe and Si. These materials were tested in T3, T6 and T7 conditions, along six orientations (LT, LS, TL, TS, SL and ST). Large variations in the fracture toughness (20-60 MPa√m) were measured. Mechanical tests on notched specimens were also performed to determine the influence of stress triaxiality ratio on ductility. These specimens were calculated by finite element method. Quantitative metallography was largely used to measure the volume fraction of intermetallic particles (Mg 2 Si and Fe-rich precipitates) and the statistical distribution of these particles. The Gurson potential is used to interpret these test resulls carried out on volume elements and on cracked specimens. It is shown that the ductility of notched specimens and the measured variations in fracture toughness can be interpreted with the Gurson potential provided that the non homogeneous distribution of intermetallic particles is taken into account. A model has been developed to relate the toughness of the alloys to the field strength, the critical void growth rate calculated on notched specimen from Rice and Tracey equation and to the mean distance between the clusters of second phase particles.

Mechanism of formation of lead sulfide ultrafine particles in reverse micellar systems.

Ultrafine PbS particles were prepared using AOT/isooctane reverse micellar systems as reaction media. On the basis of the change in UV-visible absorption spectra expressing the change in the size of semiconductor particles, the mechanism of the particle formation was studied. Because of the relatively large solubility of PbS, the growth of particles by Ostwald ripening was significant at low reactant concentration. When an excess amount of lead ion or sulfide ion was used, ultrafine PbS particles having stable spectra could be prepared. Particle coagulation was found to be controlled by the statistical distribution of particles among the reverse micelles. By irradiating a reverse micellar solution containing PbS particles stabilized by an excess amount of sulfide ion using a Xenon lamp, hydrogen was generated by the photocatalytic reduction of water.

Particle motion and charging with electrodynamic fluidization

The regularities of particle dynamics in a dispersed material bed fluidized by electric forces are studied. Statistical distribution of particles in velocities and in charges received by the dispersant in particle-electrode interactions are determined. Results of particle specific volume flows at the electrode surface and electrode charge transfer are summarized by criterion equations suitable for engineering application.