A semi‐local spectral/hp element solver for linear elasticity problems

We develop an efficient semi‐local method for speeding up the solution of linear systems arising in spectral/hp element discretization of the linear elasticity equations. The main idea is to approximate the element‐wise residual distribution with a localization operator we introduce in this paper, and subsequently solve the local linear system. Additionally, we decouple the three directions of displacement in the localization operator, hence enabling the use of an efficient low energy preconditioner for the conjugate gradient solver. This approach is effective for both nodal and modal bases in the spectral/hp element method, but here, we focus on the modal hierarchical basis. In numerical tests, we verify that there is no loss of accuracy in the semi‐local method, and we obtain good parallel scalability and substantial speed‐up compared to the original formulation. In particular, our tests include both structure‐only and fluid‐structure interaction problems, with the latter modeling a 3D patient‐specific brain aneurysm. Copyright © 2014 John Wiley & Sons, Ltd.     

Topology optimization applied to the design of 2D swirl flow devices

The design of fluid devices, such as flow machines, mixers, separators, and valves, with the aim to improve performance is of high interest. One way to achieve it is by designing them through the topology optimization method. However, there is a specific large class of fluid flow problems called 2D swirl flow problems which presents an axisymmetric flow with (or without) flow rotation around the axisymmetric axis. Some devices which allow such simplification are hydrocyclones, some pumps and turbines, fluid separators, etc. Once solving a topology optimization problem for this class of problems using a 3D domain results in a quite high computational cost, the development and use of 2D swirl models is of high interest. Thus, the main objective of this work is to propose a topology optimization formulation for 2D swirl flow fluid problem to design these kinds of fluid devices. The objective is to minimize the relative energy dissipation considering the viscous and porous effects. The 2D swirl laminar fluid flow modelling is solved by using the finite element method. A traditional material model is adopted by considering nodal design variables. An interior point optimization (IPOPT) algorithm is applied to solve the optimization problem. Numerical examples are presented to illustrate the application of this model for various 2D swirl flow cases.     

Effect of different levels of pine honey addition on physicochemical,microbiological and sensory properties of set‐type yoghurt

In this study, the effects of different levels of pine honey addition (3%, 5% and 7% w/v) to the yoghurt milk on starter bacteria, physicochemical and sensory characteristics of set‐type yoghurts during the storage were investigated. Antioxidant activity and total phenolic content of yoghurts with added honey increased compared to control yoghurt. There was a significant increase in water‐holding capacity (WHC), viscosity, total solids, redness (a*) and yellowness (b*) values of the yoghurt samples with the addition of honey at higher concentrations, whereas water activity (aw), pH and luminosity (L*) values decreased. Viscosity and WHC of the yoghurts increased during the storage.     

Weathering of metapelites from the Quadrilátero Ferrífero mineral province,southeastern Brazil

Low-grade metamorphic rocks are known for their low mechanical strength and high weatherability. In the Quadrilátero Ferrífero, an important mineral province located in southeastern Brazil, this set of features results in frequent issues with mining and road slope instability, mainly associated with phyllites. Despite the significant iron ore production that occurs in this province, little is known about the geotechnical properties of the materials constituting the weathering front. Here, we report work aimed at investigating the changes in the basic properties of phyllites at four weathering grades. The methodology used included the field classification and mapping of four weathering grades in order to assess their spatial distribution on a road slope, as well as sampling for geological characterization by petrography and X-ray diffraction (XRD). In addition, the authors performed a physical characterization of all weathering grades, including index properties, mercury porosimetry, and strength data obtained with a Schmidt hammer both in the field and in the laboratory as well as using the point load test (PLT). Results showed the relevance of structural features such as discontinuities and metamorphic foliation observed in the weathering morphology in situ, with different weathering intensities occurring along the slope. Changes in the porosity and pore size distribution in the weathering front were nonlinear, as were resistance variations. The difficulty involved in performing the macroscopic identification of weathering grades due to the very fine texture of the rock as well as microstructural heterogeneities are likely causes of the observed variability in phyllite properties. This fundamental knowledge may aid the prediction of short-term and long-term scenarios for slope stability based on rock weatherability.

     

Amplitude,phase, and hybrid ternary modulation modes of a twisted-nematic liquid-crystal display at approximately 400 nm

Applicability of a commercial twisted-nematic liquid-crystal display is examined at approximately 400 nm. Different modulation modes predicted by Jones-matrix calculus are experimentally tested. High contrast amplitude modulation with negligible loss, high contrast and low loss hybrid ternary modulation, and 1.5pi continuous phase delay without intensity modulation and with low loss are presented. Simulation results of a 4f holographic system prove the usefulness of the high contrast for amplitude modulation, and the importance of pi phase difference between high transmission white levels in a hybrid ternary modulation.     

Influence of the Mixed Propoxy/Ethoxy Spacer Arrangement Order and of the Ionic Head Group Nature on the Adsorption and Aggregation of Extended Surfactants

Two families of extended surfactants were prepared with the same head groups (carboxylate, sulfate, disodium phosphate) and different intermediate spacer structures. In one there was an average of 7 propylene oxide groups on the side of the tail and an average of 7 ethylene oxide groups on the side of the head, to produce a sequence of two different polarity segments. In the other case the spacer contained the same average numbers of propylene and ethylene oxide groups but in some homogeneous arrangement. The intermediate spacer structure, without ionic head group and in the cases of the carboxylate and sulfate extended surfactants, had a packing density reduction which is associated to the homogeneously alkoxide arrangement in the spacer. Such an arrangement was found to produce about 20% more surface area at the interface, apparently because it results in some plumpness due to the spacer folding to remain close to the interface. Both the critical micelle concentration and occupied interfacial area of the extended surfactant increased with the ionization of the anionic group associated with the electrostatic repulsion effect.     

Extending the true boiling point curve of a heavy crude oil by means of molecular distillation and characterization of the products obtained

Petroleum is evaluated by means of the true boiling point (TBP) curve, making possible to investigate the yields of the products that will be obtained in refineries, as well as establishing operating strategies and process optimization. Refineries determine TBP curves until 838 K. With molecular distillation the TBP can reach values up to 973 K. Molecular distillation shows potential in the separation, purification, and concentration of products. Eta residue is fractioned and the TBP of the whole crude oil is extended. Products of the distillation were characterized by density, SimDis (simulated distillation), and molar mass. Results showed that density and molar mass of the cuts obtained increase as the process temperature increases. These analyses confirm the efficiency of the separation method by molecular distillation.     

Leaching of natural stibnite using sodium hydroxide solution

This paper presents the results of a laboratory investigation of alkaline leaching of stibnite sample, which originated from Pezinok (Slovakia) mine. The leaching media used was aqueous solution containing sodium hydroxide. This research focused on establishing the effect of the following parameters on alkaline leaching: NaOH concentration, temperature of leaching, and grain size of solid phase. The apparent activation energy and apparent order of stibnite reaction with the solution that contained NaOH were determined from experiments as E_a ≈ 50.7 kJ mol⁻¹ and n ≈ 1, respectively. The rate-determining step is the reaction at the solid/liquid interface. A simple mathematical model equation was applied to describe the dissolution of antimony during leaching and to summarize the kinetic data.     

Optical dispersion analysis within the IR range of thermally grown and TEOS deposited SiO2 films

SiO₂ thin films, with thickness ranging between approximately 13 and 95 nm, have been thermally grown at 950°C in dry oxygen and chemically vapor deposited at low pressures (0.3 Torr) by decomposition of tetraethylorthosilicate (TEOS) at 710°C, on Si (100) substrates. Dispersion analysis was performed on Fourier transform infrared (FTIR) transmission spectra of these films within the range 900–1400 cm⁻¹. It was found that the spectra were best described within this range, by four Lorentz oscillators located near 1060, 1089, 1165 and 1220 cm⁻¹ almost independent of film thickness. The polarization of the oscillators (proportional to their strength) was found to increase slightly, and their widths to decrease, with film thickness. From the study of the FTIR spectra obtained at room temperature, it was suggested that at this temperature, a considerable number of Si–O–Si angles in these SiO₂ films are distributed in a way expected at higher temperatures and that the distribution of the Si–O–Si angles depends on the thermal history of the film and the method of growth.