Similarity Solutions for Boundary Layer Flows on a Moving Surface in Non-Newtonian Power-Law Fluids

A similarity analysis of the boundary layer flow caused by the motion of a semi-infinite flat sulface in a non-Newtonian power-law fluid at rest is made in this paper. These similar solutions fall into two categories: similarity solutions corresponding to steady boundary layers over moving surfaces and similarity solutions corresponding to unsteady boundary layers past moving flat surfaces, respectively. Except in the special case n = 1/2 (pseudoplastic) and n = 1 (Newtonian) fluids, solutions of the first category problems must be obtainednumerically. However, for the second category analytical solutions are possible for a large class of pseudoplasticfluids (n < 1), including the case of a Newtonianfluid (n = 1)

Radiation Effects on the Flow near the Stagnation Point of a Stretching Sheet

The present paper is concerned with the study of the radiation effects (Rosseland model) on the flow of an incompressible viscous fluid over a flat sheet near the stagnation point. The system of ordinary differential equations is solved numerically using the Runge-Kutta method coupled with a shooting technique. The results show that a boundary layer is formed and its thickness increases with the radiation, velocity and temperature parameters and decreases when the Prandtl number is increased

A mathematical framework for contact detection between quadric and superquadric surfaces

The calculation of the minimum distance between surfaces plays an important role in computational mechanics, namely, in the study of constrained multibody systems where contact forces take part. In this paper, a general rigid contact detection methodology for non-conformal bodies, described by ellipsoidal and superellipsoidal surfaces, is presented. The mathematical framework relies on simple algebraic and differential geometry, vector calculus, and on the C2 continuous implicit representations of the surfaces. The proposed methodology establishes a set of collinear and orthogonal constraints between vectors defining the contacting surfaces that, allied with loci constraints, which are specific to the type of surface being used, formulate the contact problem. This set of non-linear equations is solved numerically with the Newton-Raphson method with Jacobian matrices calculated analytically. The method outputs the coordinates of the pair of points with common normal vector directions and, consequently, the minimum distance between both surfaces. Contrary to other contact detection methodologies, the proposed mathematical framework does not rely on polygonal-based geometries neither on complex non-linear optimization formulations. Furthermore, the methodology is extendable to other surfaces that are (strictly) convex, interact in a non-conformal fashion, present an implicit representation, and that are at least C2 continuous. Two distinct methods for calculating the tangent and binormal vectors to the implicit surfaces are introduced: (i) a method based on the Householder reflection matrix; and (ii) a method based on a square plate rotation mechanism. The first provides a base of three orthogonal vectors, in which one of them is collinear to the surface normal. For the latter, it is shown that, by means of an analogy to the referred mechanism, at least two non-collinear vectors to the normal vector can be determined. Complementarily, several mathematical and computational aspects, regarding the rigid contact detection methodology, are described. The proposed methodology is applied to several case tests involving the contact between different (super)ellipsoidal contact pairs. Numerical results show that the implemented methodology is highly efficient and accurate for ellipsoids and superellipsoids.Fundação para a Ciência e a Tecnologia (FCT

Feature Selection via Chaotic Antlion Optimization

Selecting a subset of relevant properties from a large set of features that describe a dataset is a challenging machine learning task. In biology, for instance, the advances in the available technologies enable the generation of a very large number of biomarkers that describe the data. Choosing the more informative markers along with performing a high-accuracy classification over the data can be a daunting task, particularly if the data are high dimensional. An often adopted approach is to formulate the feature selection problem as a biobjective optimization problem, with the aim of maximizing the performance of the data analysis model (the quality of the data training fitting) while minimizing the number of features used.This work was partially supported by the IPROCOM Marie Curie initial training network, funded through the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme FP7/2007-2013/ under REA grants agreement No. 316555, and by the Romanian National Authority for Scientific Research, CNDIUEFISCDI, project number PN-II-PT-PCCA-2011-3.2- 0917. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Landslide Risk Assessment by Using a New Combination Model Based on a Fuzzy Inference System Method

Landslides are one of the most dangerous phenomena that pose widespread damage to property and human lives. Over the recent decades, a large number of models have been developed for landslide risk assessment to prevent the natural hazards. These models provide a systematic approach to assess the risk value of a typical landslide. However, often models only utilize the numerical data to formulate a problem of landslide risk assessment and neglect the valuable information provided by experts’ opinion. This leads to an inherent uncertainty in the process of modelling. On the other hand, fuzzy inference systems are among the most powerful techniques in handling the inherent uncertainty. This paper develops a powerful model based on fuzzy inference system that uses both numerical data and subjective information to formulate the landslide risk more reliable and accurate. The results show that the proposed model is capable of assessing the landslide risk index. Likewise, the performance of the proposed model is better in comparison with that of the conventional techniques

Rotating Flow of Power-Law Fluids over a Stretching Surface

The steady flow of a non-Newtonian power-law fluid due to a stretching surface in a rotating fluid has been investigated in this paper. After a similarity transformation, the set of non-linear ordinary differential equations have been solved numerically using the Keller-box method for some values of the parameter  which is the ratio of the rotation rate to the stretching rate and the power-law index. It is found that both the skin frictions coefficients in the x and y directions decrease with the increase of the parameter. However, for smaller values of  the skin friction coefficients are higher for the dilatant fluid and smaller for the pseudoplastic fluid, respectively