Catálogo de publicaciones - libros

We develop a lubrication model for the viscous drop spreading with evaporation. It is then solved in the quasi-static case and the numerical method is used in the parameter identification in the application to DNA chips.

We propose and evaluate a method for the recognition of airborne fungi spores. We suggest a similarity-based object-recognition method to identify spores in a digital microscopic image. We do not use the gray values of the case, but the object edges instead. The similarity measure measures the average angle between the vectors of the template and the object. Case generation is done semi-automatically by manually tracing the object, automatic shape alignment, similarity calculation, clustering, and prototype calculation.

Miniaturized robotic manipulators are a key element in future highprecision minimally invasive surgery and telesurgery. This development is supported by the rapidly decreasing size of robotic sensors and actuators. Severe limitations are currently induced by the drives of the micro-joints.

The present paper deals with the optimal control of an advanced six-sectional branched manipulator. Joints are driven by weak, but fast, and strong, but slow, actuators acting in parallel. This results in the new and challenging problem of constrained optimal control of multibody systems subject to rivalling controls. For efficient treatment the differential equations of the state and adjoint variables are recursively defined. Geometric constraints lead to state constraints of second order. The complete problem of optimal control is transferred into a piecewise defined, highly nonlinear multi-point boundary value problem. The numerical solution of the boundary value problem is by the advanced multiple shooting method .

A mathematical and numerical model to predict the non-linear behaviour of concrete as multiphase porous material is proposed. The model can be usefully applied to several practical cases: evaluation of concrete performance in the high temperature range, e.g. during fire, to early stages of maturing of massive concrete structures, to shotcrete in tunnelling, and to durability. All the important phase changes of water and chemical reactions, i.e. adsorption-desorption, condensation-evaporation, and hydration-dehydration, as well as the related heat and mass sources or sinks are considered. Changes of the material properties caused by temperature and pressure changes, concrete damage or carbonation, fresh concrete hardening, as well as coupling between thermal, hygral and mechanical phenomena are taken into account. This model further allows to incorporate sorption hysteresis. Some relevant applications of the model will be shown in this work.

For the modelling of the glass press-blow process level set functions are used. Special difficulties arise due to velocity gradients in the domain. A reinitialisation procedure for unstructured triangular meshes is adapted to these difficulties and is applied.

We consider a model for laser surface remelting, a process to improve the surface quality of steel components. The mathematical model consists of the two-dimensional heat equation for temperature and an ordinary differential equation for the liquid phase. The equations are coupled via source terms. We study the efficient numerical simulation using adaptive grids, which are especially well-suited for problems with moving heat sources. To account for the local high activity due to the heat source, we introduce local uniform grids and couple the solutions on the global coarse and local fine grids using the local defect correction (LDC) technique.

We consider minimizing the mass of an injection moulding machine, fulfilling certain constraints. The deformation of its frame is described by the plain stress state equations for linear elasticity. The minimization problem is a nonlinear constrained one. When the design parameters change, then also the shape will change. Generating a new finite element mesh for each single shape leads to a non-differentiable objective. Here we deform the mesh elastically.

This work deals with the motion of a long slender elastic fiber in a turbulent flow. Neglecting the fiber effect on the turbulence, a centered differentiable Gaussian field is derived for the randomly fluctuating component of the flow velocity. The construction of the initial double-velocity correlation tensor is hereby based on the model and Kolmogorov’s universal equilibrium theory. Its dynamic is described by Taylor’s hypothesis of frozen turbulence. Using an empirical drag coefficient, the developed fluctuation field leads to a correlated stochastic force that can numerically be treated as white noise with flow dependent amplitude.

The conventional material from which silos are usually constructed is steel, and the existing codes and standards on these structures reect the design criteria appropriate for an isotropic material. This paper deals with the design optimisation of the silos made from composite materials. The purpose of the present study is to perform the design optimisation of cylindrical composite silos loaded with the unsymmetrical external pressure caused by the action of wind. The design methodology is outlined, and the effectiveness of the optimisation is demonstrated using a particular example. In this case, the resultant optimised design produced a 29% saving in wall thickness, and thus material cost, in comparison with the non-optimised wall thickness.

In this paper, we perform a linear stability analysis using normal modes on the two-dimensional system of two superposed fluids confined between two infinite plates in the presence of a large temperature gradient. The movement of the fluids is characterized by a combination of inertial and buoyancy forces, thus we are dealing with a mixed convection problem. The results of the linear stability analysis show that for large wave numbers, the small amplitude waves travel with the interface velocity.