Investigation of Water to Ice Phase Change in Porous Media by Ultrasonic and Dielectric Measurements

The main objective of this paper is to study the evolution of the ice content of porous media submitted to subzero temperatures by dielectric and ultrasonic measurements. Dielectric measurements are made by a capacitive sensor-based apparatus. The amount of ice formed within the tested sample is estimated from the global dielectric constants of the sample and of all the phases that form the tested composite material. On the other hand, ultrasonic measurements are based on the evolution of the ultrasonic wave velocity through the tested sample during a freezing-thawing cycle. These two methods lead to very close results and appear to be cheaper alternatives to low temperature calorimetry. The ice content curves are analyzed with the help of thermoporometry concepts in order to characterize the pore-size distribution. Results appear to be complementary to mercury intrusion porosimetry ones. Moreover, the commonly observed hysteresis of the ice content during a freezing-thawing cycle is investigated with respect to material microstructure.     

Dual Norms and Image Decomposition Models

Following a recent work by Y. Meyer, decomposition models into a geometrical component and a textured component have recently been proposed in image processing. In such approaches, negative Sobolev norms have seemed to be useful to modelize oscillating patterns. In this paper, we compare the properties of various norms that are dual of Sobolev or Besov norms. We then propose a decomposition model which splits an image into three components: a first one containing the structure of the image, a second one the texture of the image, and a third one the noise. Our decomposition model relies on the use of three different semi-norms: the total variation for the geometrical component, a negative Sobolev norm for the texture, and a negative Besov norm for the noise. We illustrate our study with numerical examples.     

Preface: Volume 68, Issue 6

INFINITY 2002, the 4th International Workshop on Verification of Infinite-State Systems, was held as a satellite workshop of CONCUR 2002 (the 13th International Conference on Concurrency Theory) in Brno, Czech Republic, on August 24, 2002. The aim of the workshop is to provide a forum for researchers interested in the development of mathematical techniques for the analysis and verification of systems with infinitely many states. The topics of INFINITY 2002 included the following: techniques for modeling and analysis of infinite-state systems, equivalence-checking and model-checking with infinite-state systems, parameterized systems, calculi for mobility and security, finite-state abstractions of infinite-state systems.The volume consists of six contributed papers selected by the INFINITY 2002 programme committee. The papers were reviewed by the program committee consisting, besides editors, of

Parosh Abdulla	(Uppsala (SE))
Julian Bradfield	(Edinburgh (UK))
Didier Caucal	(Irisa (F))
Hubert Comon	(LSV Cachan (F))
Giorgio Delzanno	(Genova (I))
Yoram Hirshfeld	(Tel-Aviv (Israel))
Denis Lugiez	(Marseille (F))
Bernhard Steffen	(Dortmund (D))
P.S. Thiagarajan	(Chennai (India))
Moshe Vardi	(Rice (USA))

Full-size table

The programme of INFINITY 2002 was further enriched by an invited talk given by Colin Stirling, and by four short presentations of work in progress.This volume will be published as volume 68(6) in the series Electronic Notes in Theoretical Computer Science (ENTCS). This series is published electronically through the facilities of Elsevier Science B.V. and its auspices. The volumes in the ENTCS series can be accessed at the URL http://www.elsevier.nl/locate/entcsWe are very grateful to the CONCUR 2002 Organizing Committee for arranging all local affairs, and to Michael Mislove, the managing editor of ENTCS, for providing the opportunity to publish the INFINITY 2002 proceedings in the ENTCS series.December 9, 2002 Antonin Kucera, Richard Mayr     

Integrated advanced control and online optimization in olefins plant

The benefits of optimization cover a broad spectrum. In many cases the rewards are in the range of several million dollars per year. The first step prior to the implementation of optimization is a detailed study of the current operating conditions and philosophy and market demands. Only then can an optimizer be effectively designed and implemented.The system which consists of advanced control of key plant sections linked to a global online plant optimizer will be described. Since optimum operating conditions are almost always at one or more constraint boundaries, a major task of the advanced control strategies is constraint riding.The advanced control strategies and techniques used are described in detail.The online optimizer is based on a detailed model of the whole plant. Although the major benefits are in optimal operation of the cracking section, a detailed model of the separation section is essential for accurate prediction of constraints. Online data is used to identify changes in feed properties and a suitable starting point for the optimization as well as to update the model correlations and improve accuracy.The design of a simple and robust operator interface is critical to the success of such a system and will be described in detail.     

Noncontact interferometric optical probe for calibration of coordinate measuring machines

Our work deals with point length standards, which can be practically realized by two precise spheres or parts of spheres connected by a bar or array of spherical surfaces. The distance between the centers of spheres precisely determines the length. Two methods (mechanical and optical) are shown for determination of the centers of spheres of the length standard. The proposed optical method is based on the interference of light. General formulas are derived that make it possible to calculate accurately the center position of the spherical surface, which is used for the length standards. An analysis of the proposed method is described based on the third-order aberration theory. The proposed technique can be used for calibration and checking of computer numerical controlled machines.