Boundary homogenization for a quasi-linear elliptic problem

We describe the asymptotic behaviour of the solution of a quasi-linear elliptic problem posed in a cylinder and with homogeneous Dirichlet boundary conditions imposed on narrow helicoidal strips ε-periodically distributed on the lateral boundary of this cylinder when the parameter ε goes to 0. We use epi-convergence arguments in order to establish the limit behaviour. We also compute the rate of convergence of the solution of the original problem to that of the limit one.     

Isolation of Gravity Effects on Diffusion Flames by Magnetic Field

We present the experimental demonstration of the ability of magnetic field to remove buoyancy effects on flames. The experiment consists to observing the shape and colour changes of a laminar jet diffusion flame located in the air-gap of a Bitter magnet able to delivering up 650 T²/m in magnetic gradient intensity. At some critical (predicted theoretically) value of the upward magnetic field gradient strength, the flame becomes nearly hemispheric and free of soot similarly to flames at zero-gravity in drop towers.     

Finite element analysis of thermoelastic contact problem in functionally graded axisymmetric brake disks

An analysis of thermoelastic contact problem of functionally graded (FG) rotating brake disk with heat source due to contact friction is presented. Finite element method (FEM) is used. The material properties of disk are assumed to be represented by power-law distributions in the radial direction. The inner and outer surfaces considered are metal and ceramic, respectively. Pure material is considered for the brake pad. Coulomb contact friction is assumed as the heat source. It is divided into two equal parts between pad and brake disk which leads to thermal stresses. Mechanical response of FG disks are compared and verified with the known results from the literatures. The results show that the maximum value of radial displacement in mounted FG brake disk is not at outer surface. It is found that the all areas between pad and brake disk is in full-contact status when the ratio of pad thickness to brake disk thickness is 0.66. It is observed that the total strain due to thermomechanical load is negative for some parts of the disks, whereas, the thermal strains are always positive. It can be concluded that gradation index of the metal-ceramic has significant effect in the thermomechanical response of FG disks.     

Tensile,dielectric, and thermal properties of epoxy composites filled with silica,mica, and calcium carbonate

The minerals silica, mica, and calcium carbonate (CaCO₃) were used as fillers to produce epoxy thin film composites for capacitor application. The effects of filler loading and type on the morphology, tensile, dielectric, and thermal properties of the epoxy thin film composites were determined. Results showed that epoxy thin films with 20 vol% filler loading showed good dielectric properties, thermal conductivity, and thermal stability. However, the tensile properties of the thin films were reduced as the filler loading was increased due to brittleness. Dielectric constant and dielectric loss of epoxy/inorganic composite films generally increased with increasing mineral filler loading. Meanwhile, the presence of mineral filler improved the thermal stability of the thin film composites. The highest dielectric constant of 5.75 with 20 vol% filler loading at a frequency of 1 MHz was exhibited by the epoxy/CaCO₃ composite, followed by epoxy/mica and epoxy/silica. Therefore, the epoxy/CaCO₃ composite is the most potential candidate for capacitor application. Moreover, precipitated CaCO₃ provided better tensile properties and slightly improved the dielectric properties compared with mineral CaCO₃.     

Tabu search for the redundancy allocation problem of homogenous series–parallel multi-state systems

This paper develops an efficient tabu search (TS) heuristic to solve the redundancy allocation problem for multi-state series–parallel systems. The system has a range of performance levels from perfect functioning to complete failure. Identical redundant elements are included in order to achieve a desirable level of availability. The elements of the system are characterized by their cost, performance and availability. These elements are chosen from a list of products available in the market. System availability is defined as the ability to satisfy consumer demand, which is represented as a piecewise cumulative load curve. A universal generating function technique is applied to evaluate system availability. The proposed TS heuristic determines the minimal cost system configuration under availability constraints. An originality of our approach is that it proceeds by dividing the search space into a set of disjoint subsets, and then by applying TS to each subset. The design problem, solved in this study, has been previously analyzed using genetic algorithms (GAs). Numerical results for the test problems from previous research are reported, and larger test problems are randomly generated. Comparisons show that the proposed TS out-performs GA solutions, in terms of both the solution quality and the execution time.     

Database systems: their applications to CAD software design

This paper concerns the application of database theories formulated mostly in the commercial and business area of data processing to CAD software design. The major approaches to database system design are analysed and examples of CAD software systems which have utilized them are indicated. An integraged approach to database system is proposed as an alternative for further investigations.     

Grain growth simulation of [001] textured YBCO films grown on (001) substrates with large lattice misfit: Prediction of misorientations of the remaining boundaries

We study the effects of (1) the variation of grain boundary energy with misorientation and (2) the large lattice misfit (>3%) between the films and substrates on grain growth in films by method of Monte Carlo simulations. The results from the grain growth simulation in YBa₂Cu₃O_7-x (YBCO) films was found to concur with previous experimental observation of preferred grain orientations for YBCO films deposited on various substrates such as (001) magnesium oxide (MgO) and (001) yttria stabilized zirconia (YSZ). The simulation has helped us to identify three factors influencing the competition of these [001] tilt boundaries. They are: (1) the relative depths of local minima in the boundary energy vs. misorientation curve, (2) the number of combinations of coincidence epitaxy (CE) orientations contributing to the exact misorientation for each of the high-angle-but-low-energy (HABLE) boundaries, and (3) the number of combinations of CE orientations within the angular ranges bracketing each of the exact HABLE boundaries. Hence, these factors can be applied to clarify the origin of special misorientations observed experimentally.     

Some factors associated with substance abuse among secondary school students in Trinidad and Tobago

Quantitative myocardial perfusion single-photon emission computed tomography can be improved further by technical advancements that are imminent in the clinical setting. These improvements are directed toward two main goals: (1) increasing the accuracy that the myocardial count distribution from tomographic slices represents the true tracer concentration and (2) increasing the accuracy of extracting this myocardial count distribution for quantitative analysis. Once these advancements are fully validated and implemented clinically, the clinical value of these cardiac diagnostic tests will be enhanced by increased accuracy of detecting and characterizing myocardial hypoperfusion and coronary artery disease.     

The subcellular localisation and the time course of bismuth in the gastric mucosa of rats after short-term administration of colloidal bismuth subcitrate

The aim of this study was to investigate if colloidal bismuth subcitrate (CBS) can penetrate the gastric mucus barrier to reach the different sites of the antral mucosa and to estimate the time course for CBS to reach and remain in the mucosa. A single dose of CBS was administered orally to rats that were sacrificed at different time intervals post treatment. The control group received gum acacia without CBS. Colloidal bismuth subcitrate, visualised as electron dense precipitate (EDP), was seen in the gastric mucus layer, intercellular spaces and intracellularly after 30 minutes and disappeared after 6 hours. Scant amounts of EDP were observed in the gastric crypts, confined only to the upper parts of these structures. We concluded that CBS can penetrate the mucus and has a wide but uneven distribution in the gastric mucosa. Colloidal bismuth subcitrate, in the concentration given only penetrated the upper two-thirds of gastric pits and not the lower one-third. We also concluded that CBS has to be given 6 hourly to ensure its continuous presence in the gastric mucosa.     

Big Data: from collection to visualization

Organisations are increasingly relying on Big Data to provide the opportunities to discover correlations and patterns in data that would have previously remained hidden, and to subsequently use this new information to increase the quality of their business activities. In this paper we present a ‘story’ of Big Data from the initial data collection and to the end visualization, passing by the data fusion, and the analysis and clustering tasks. For this, we present a complete work flow on (a) how to represent the heterogeneous collected data using the high performance RDF language, how to perform the fusion of the Big Data in RDF by resolving the issue of entity disambiguity and how to query those data to provide more relevant and complete knowledge and (b) as the data are received in data streams, we propose batchStream, a Micro-Batching version of the growing neural gas approach, which is capable of clustering data streams with a single pass over the data. The batchStream algorithm allows us to discover clusters of arbitrary shapes without any assumptions on the number of clusters. This Big Data work flow is implemented in the Spark platform and we demonstrate it on synthetic and real data.