Effects of alcohol and caffeine on maritime navigational skills

Twelve experienced navigators participated in an experiment to determine the effects of alcohol, caffeine, and an alcohol+caffeine mixture on performance during the following tasks: visual search, the search and location of items on a navigational chart (chartsearch) and the solving of maritime navigational problems. Alcohol (75 ml) produced impairment in performance on visual search (p<0.05) and navigational problem-solving (p<0.01). Caffeine was found to enhance performance on visual search (p<0.05) but not on the chartsearch, although a significant correlation was found between performance on the two tests (p<0.05). Caffeine was not found to improve the accuracy of navigational problem-solving (p>0.05). Neither alcohol nor caffeine had any significant effect on the speed of problem-solving (p>0.05).     

Prediction of translational accommodation coefficient

A simple empirical equation has been developed from experimental data for prediction of the translational accommodation coefficient. It contains such basic parameters of gas-surface interaction as the atomic weights of gas and solid surface atoms, their temperatures and the ratio of specific heats of the gas. Adequate agreement with experimental data available in the literature for monatomic, diatomic and polyatomic gases is obtained for a wide range of gas-surface parameters.     

Dimensional model reduction in non‐linear finite element dynamics of solids and structures

A general approach to the dimensional reduction of non‐linear finite element models of solid dynamics is presented. For the Newmark implicit time‐discretization, the computationally most expensive phase is the repeated solution of the system of linear equations for displacement increments. To deal with this, it is shown how the problem can be formulated in an approximation (Ritz) basis of much smaller dimension. Similarly, the explicit Newmark algorithm can be also written in a reduced‐dimension basis, and the computation time savings in that case follow from an increase in the stable time step length. In addition, the empirical eigenvectors are proposed as the basis in which to expand the incremental problem. This basis achieves approximation optimality by using computational data for the response of the full model in time to construct a reduced basis which reproduces the full system in a statistical sense. Because of this ‘global’ time viewpoint, the basis need not be updated as with reduced bases computed from a linearization of the full finite element model. If the dynamics of a finite element model is expressed in terms of a small number of basis vectors, the asymptotic cost of the solution with the reduced model is lowered and optimal scalability of the computational algorithm with the size of the model is achieved. At the same time, numerical experiments indicate that by using reduced models, substantial savings can be achieved even in the pre‐asymptotic range. Furthermore, the algorithm parallelizes very efficiently. The method we present is expected to become a useful tool in applications requiring a large number of repeated non‐linear solid dynamics simulations, such as convergence studies, design optimization, and design of controllers of mechanical systems. Copyright © 2001 John Wiley & Sons, Ltd.     

Information mining — Reflections on recent advancements and the road ahead in data, text, and media mining

In this introduction, we briefly summarize the state of data and text mining today. Taking a very broad view, we use the term information mining to refer to the organization and analysis of structured or unstructured data that can be quantitative, textual, and/or pictorial in nature. The key question, in our view, is, “How can we transform data (in the very broad sense of this term) into ‘actionable knowledge’, knowledge that we can use in pursuit of a specified objective(s).” After detailing a set of key components of information mining, we introduce each of the papers in this volume and detail the focus of their contributions.     

Virtual surgeries in patients with congenital heart disease: a multi-scale modelling test case

The objective of this work is to perform a virtual planning of surgical repairs in patients with congenital heart diseases--to test the predictive capability of a closed-loop multi-scale model. As a first step, we reproduced the pre-operative state of a specific patient with a univentricular circulation and a bidirectional cavopulmonary anastomosis (BCPA), starting from the patient's clinical data. Namely, by adopting a closed-loop multi-scale approach, the boundary conditions at the inlet and outlet sections of the three-dimensional model were automatically calculated by a lumped parameter network. Successively, we simulated three alternative surgical designs of the total cavopulmonary connection (TCPC). In particular, a T-junction of the venae cavae to the pulmonary arteries (T-TCPC), a design with an offset between the venae cavae (O-TCPC) and a Y-graft design (Y-TCPC) were compared. A multi-scale closed-loop model consisting of a lumped parameter network representing the whole circulation and a patient-specific three-dimensional finite volume model of the BCPA with detailed pulmonary anatomy was built. The three TCPC alternatives were investigated in terms of energetics and haemodynamics. Effects of exercise were also investigated. Results showed that the pre-operative caval flows should not be used as boundary conditions in post-operative simulations owing to changes in the flow waveforms post-operatively. The multi-scale approach is a possible solution to overcome this incongruence. Power losses of the Y-TCPC were lower than all other TCPC models both at rest and under exercise conditions and it distributed the inferior vena cava flow evenly to both lungs. Further work is needed to correlate results from these simulations with clinical outcomes.