Further Results to Time-Dependent Local Scour at Bridge Elements

This research intends to clarify the limitations of a local scour equation recently proposed, based on extended laboratory data collected at VAW, Zurich, Switzerland. The present project is concerned with four items: (1) clarification of the minimum laboratory dimensions required to apply Froude similitude; (2) effect of sloping abutments on scour advance; (3) extension of scour formula to spur dikes; and (4) effect of unsteady flow on scour development. These items were investigated mainly from an experimental point of view based on some 150 laboratory experiments and accounted for by a hydraulic approach. It was found that the basic scour equation mentioned may be applied provided additional limitations are specified. These are discussed in the light of the densimetric particle Froude number, the threshold Froude number, and other important parameters that influence the progress of local scour. The results of this study may be applied to practice, provided the limitations of the computational approach are respected.     

Progressive crushing of fiber-reinforced composite structural components of a Formula One racing car

The present paper describes an experimental and numerical investigation on energy absorbers for Formula One side impact and steering column impact. The crash tests are performed measuring the load-shortening diagram and the energy absorbed by the structure. A finite element model is then developed using the non-linear, explicit dynamic code LS-DYNA. To set up the numerical model, tubes crushing testing are conducted to determine the material failure modes and to characterise them with LS-DYNA. The results presented in this study show that the composite structural components of the investigated Formula One racing car possess high value of specific absorbed energy and crash load efficiency around 1.1. The finite element simulations accurately predict the overall shape, magnitude and pulse duration in all the types of impact as well as the deformation and failure of the structures. Comparing the numerical data of the specific absorbed energy to the experimental results, the differences are around 10%.     

CNN‐based architecture for real‐time object‐oriented video coding applications

This paper presents a new CNN‐based architecture for real‐time video coding applications. The proposed approach, by exploiting object‐oriented CNN algorithms and MPEG encoding capabilities, enables low bit‐rate encoder/decoder to be designed. Simulation results using Claire video sequence show the effectiveness of the proposed scheme. Copyright © 2005 John Wiley & Sons, Ltd.     

Towards Syntax-Aware Editors for Visual Languages

Editors for visual languages should provide a user-friendly environment supporting end users in the composition of visual sentences in an effective way. Syntax-aware editors are a class of editors that prompt users into writing syntactically correct programs by exploiting information on the visual language syntax. In particular, they do not constrain users to enter only correct syntactic states in a visual sentence. They merely inform the user when visual objects are syntactically correct. This means detecting both syntax and potential semantic errors as early as possible and providing feedback on such errors in a non-intrusive way during editing. As a consequence, error handling strategies are an essential part of such editing style of visual sentences.In this work, we develop a strategy for the construction of syntax-aware visual language editors by integrating incremental subsentence parsers into free-hand editors. The parser combines the LR-based techniques for parsing visual languages with the more general incremental Generalized LR parsing techniques developed for string languages. Such approach has been profitably exploited for introducing a noncorrecting error recovery strategy, and for prompting during the editing the continuation of what the user is drawing.     

An efficient algebraic multigrid method for solving optimality systems

An algebraic multigrid method (AMG) for solving convection-diffusion optimality systems is presented. Results of numerical experiments demonstrate robustness of the AMG scheme with respect to changes of the weight of the cost of the control and show that the computational performance of the proposed AMG scheme is comparable to that of AMG applied to single scalar equations.     

Fabrication of miniaturized Si-based electrocatalytic membranes

The increasing interest for lightweight and portable electronic systems, cellphones and small digital devices is driving technological research towards integrated regenerating power sources with small dimensions and great autonomy. Conventional batteries are already unable to deliver power in ever smaller volumes while maintaining the requirements of long duration and light weight. A possible solution to overcome these limits is the use of miniaturized fuel cells. The fuel cell offers a greater gravimetric energy density compared to conventional batteries. The micromachining technology of silicon is an important tool to reduce the fuel cell structure to micron sizes. The use of silicon also gives the opportunity to integrate the power source and the electronic circuits controlling the fuel cell on the same structure. This article reports preliminary results concerning the micromachining process for fabricating a silicon-based electrocatalytic membrane for miniaturized Si-based proton-exchange membrane (PEM) fuel cells.     

Procedure for calibrating an ultrasonic sensor for online monitoring of conversion in latex reactors

In order to estimate online conversion and polymer composition through sound velocity measurements, a mathematical model for calculating sound velocity in emulsion polymerization has been developed. With respect to previous modeling approaches, its main features are as follows: (1) the application to three‐phase, reacting systems of Urick equation (usually adopted for estimating sound velocity in multiphase, dispersed, unreacting systems, such as emulsions and suspensions); and (2) the development of an empirical relationship for estimating particle compressibility as a function of conversion during the reaction. The model has been validated through several sets of experimental data of batch and semibatch homo‐ and copolymerizations involving styrene, butyl acrylate, vinyl acetate, and methyl methacrylate. In most of the examined cases, the performances of the calibration model are satisfactory. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1451–1477, 1999     

Influence of solvent and filler on some physical properties of a fluoroelastomer

Samples of virgin and a crosslinked fluorinated rubber, containing different amounts of carbon black and solvated with methylethyl ketone, have been investigated by differential scanning calorimetry. Although the polymer–solvent interaction increases with decreasing temperature, a process of solvent separation was observed for all of the systems. This process can be attributed to a T_g regulation effect in which solvent crystallization occurs only when the crystallization temperature is higher than the T_g of the system. The interaction between rubber and filler, approximately temperature independent, was found to not influence the glass transition of the rubber–methylethyl ketone systems, even when the carbon black content is on the order of 35 wt %. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 377–384, 1999