Space–time interface-tracking with topology change (ST-TC)

To address the computational challenges associated with contact between moving interfaces, such as those in cardiovascular fluid–structure interaction (FSI), parachute FSI, and flapping-wing aerodynamics, we introduce a space–time (ST) interface-tracking method that can deal with topology change (TC). In cardiovascular FSI, our primary target is heart valves. The method is a new version of the deforming-spatial-domain/stabilized space–time (DSD/SST) method, and we call it ST-TC. It includes a master–slave system that maintains the connectivity of the “parent” mesh when there is contact between the moving interfaces. It is an efficient, practical alternative to using unstructured ST meshes, but without giving up on the accurate representation of the interface or consistent representation of the interface motion. We explain the method with conceptual examples and present 2D test computations with models representative of the classes of problems we are targeting.     

A comparison for Turkish provinces’ performance of urban air pollution

The objective of this paper is to assess the environmental performance of Turkish provinces by using a non-parametric method, Data Envelopment Analysis. The results of ranking are based on the provinces’ ability to produce the largest equi-proportional increase in the desirable output-gross domestic product and decrease in the undesirable output namely, air pollutants. The results indicate that 7.41% of the sample provinces are relatively efficient. The results also show that, regions with the highest level gross domestic product per capita have the highest efficiency scores. New industrial districts have lower efficiencies in spite of relatively higher income per capita. In the second stage of the study the possible relationship between environmental efficiency scores and input, output variables are investigated by a regression analysis. According to the results, there is a positive relationship between gross domestic product and efficiency scores.     

Effect of dust content on some properties of concrete

Summary The region mapped is located in the north-eastern part of the Parana basin in Brazil. The area contains sedimentary rocks and large flows and intrusions of basaltic rocks. As a result of transcurrent faulting due to the displacement of Atlantic plates to the west, followed by uplift, flexuring and normal faulting, the most important rivers draining the region flow out of the basin over fractured zones following the dip of the beds from SE to NW. Study of the frequency of occurrence of erosion surfaces in the more fractured zones offers a means of studying the structural conditions in the area and the degree of fracturing of rock masses. Geomorphological mapping, together with statistical surveys of erosion surfaces and regions with high and low degrees of depression and tilting, permits the localisation of areas more suitable for civil engineering works because of reduced seismicity, slope instability and water flows.

---

Cartographie morphotectonique pour la construction d'ouvrages d'art dans la partie nord-est du bassin du parana, Bresil

Résumé La région cartographiée est située dans la partie nord-est du bassin du Parana, au Brésil. Elle comprend des roches sédimentaires et des roches basaltiques en grandes coulées et en intrusions. Du fait de la présence de failles de décrochement dues au déplacement des plaques atlantiques vers l'ouest, puis à leur soulèvement, à leur flexure et à la formation de failles normales, les principaux cours d'eau qui drainent cette région sortent du bassin en traversant des zones fracturées et en suivant le pendage des couches du sud-est vers le nord-ouest. L'étude de la fréquence des surfaces d'érosion dans les zones les plus fracturées constitue un moyen d'étude des conditions structurales de la région et du degré de fracturation des masses rocheuses. La cartographie géomorphologique, associée à une enquête statistique sur la surface d'érosion et sur les régions comportant de hauts degrés ou de bas degrés de dépression et d'inclinaison, permet de localiser comme aires les plus favorables à la construction de grands ouvrages celles qui présentent une moindre sismicité, une moindre instabilité des talus et moins d'inondations.

     

Wall shear stress calculations in space–time finite element computation of arterial fluid–structure interactions

The stabilized space–time fluid–structure interaction (SSTFSI) technique was applied to arterial FSI problems soon after its development by the Team for Advanced Flow Simulation and Modeling. The SSTFSI technique is based on the Deforming-Spatial-Domain/Stabilized Space–Time (DSD/SST) formulation and is supplemented with a number of special techniques developed for arterial FSI. The special techniques developed in the recent past include a recipe for pre-FSI computations that improve the convergence of the FSI computations, using an estimated zero-pressure arterial geometry, Sequentially Coupled Arterial FSI technique, using layers of refined fluid mechanics mesh near the arterial walls, and a special mapping technique for specifying the velocity profile at inflow boundaries with non-circular shape. In this paper we introduce some additional special techniques, related to the projection of fluid–structure interface stresses, calculation of the wall shear stress (WSS), and calculation of the oscillatory shear index. In the test computations reported here, we focus on WSS calculations in FSI modeling of a patient-specific middle cerebral artery segment with aneurysm. Two different structural mechanics meshes and three different fluid mechanics meshes are tested to investigate the influence of mesh refinement on the WSS calculations.     

Solution of linear systems in arterial fluid mechanics computations with boundary layer mesh refinement

Computation of incompressible flows in arterial fluid mechanics, especially because it involves fluid–structure interaction, poses significant numerical challenges. Iterative solution of the fluid mechanics part of the equation systems involved is one of those challenges, and we address that in this paper, with the added complication of having boundary layer mesh refinement with thin layers of elements near the arterial wall. As test case, we use matrix data from stabilized finite element computation of a bifurcating middle cerebral artery segment with aneurysm. It is well known that solving linear systems that arise in incompressible flow computations consume most of the time required by such simulations. For solving these large sparse nonsymmetric systems, we present effective preconditioning techniques appropriate for different stages of the computation over a cardiac cycle.     

Magnetic and optical characterization of Mn-doped PbS nanocrystals supported in oxide glass matrix

The evidence of successful growth of Mn-doped PbS (Pb_1−xMn_xS) nanocrystals (NCs) in SiO₂–Na₂CO₃–Al₂O₃–PbO₂–B₂O₃ template, using the fusion method, is reported on in this study. The as-grown Pb_1−xMn_xS NC is characterized using optical absorption, electron paramagnetic resonance, and atomic force microscopy. The data are discussed in terms of two distinct scenarios, namely a core-doped and a shell-doped nanostructure.     

A nested iterative scheme for computation of incompressible flows in long domains

We present an effective preconditioning technique for solving the nonsymmetric linear systems encountered in computation of incompressible flows in long domains. The application category we focus on is arterial fluid mechanics. These linear systems are solved using a nested iterative scheme with an outer Richardson scheme and an inner iteration that is handled via a Krylov subspace method. Test computations that demonstrate the robustness of our nested scheme are presented.