A graph-based approach for extracting terminological properties from information sources with heterogeneous formats

The problem of handling both the integration and the cooperation of a large number of information sources characterised by heterogeneous representation formats is a challenging issue. In this context, a central role can be played by the knowledge about the semantic relationships holding between concepts belonging to different information sources (intersource properties). In this paper, we propose a semiautomatic approach for extracting two kinds of intersource properties, namely synonymies and homonymies, from heterogeneous information sources. In order to carry out the extraction task, we introduce both a conceptual model, for representing involved sources, and a metrics, for measuring the strength of the semantic relationships holding among concepts represented within the same source.     

Constructing meta-CASE workbenches by exploiting visual language generators

In this paper, we propose an approach for the construction of meta-CASE workbenches, which suitably integrates the technology of visual language generation systems, UML metamodeling, and interoperability techniques based on the GXL (graph exchange language) format. The proposed system consists of two major components. Environments for single visual languages are generated by using the modeling language environment generator (MEG), which follows a metamodel/grammar-approach. The abstract syntax of a visual language is defined by UML class diagrams, which serve as a base for the grammar specification of the language. The workbench generator (WoG) allows designers to specify the target workbench by means of a process model given in terms of a suitable activity diagram. Starting from the supplied specification WoG generates the customized workbench by integrating the required environments.     

Detecting feature interaction in CPL

This article addresses the problem of detecting feature interactions in the area of telephony systems design. The proposed approach consists of two phases: filtering and testing. The filtering phase detects possible interactions by identifying incoherencies in a logic specification of the main elements of the features, consisting of preconditions, triggers, results and constraints. If incoherencies are identified, then an interaction is suspected, test cases corresponding to the suspected interaction are generated and testing is applied to see if the interaction actually exists. Two case studies, carried out on established benchmarks, show that this approach gives good results in practice. Nicolas Gorse received a Master of Computer Science from the University of Ottawa, School of Information Technology and Engineering in 2001.He is currently a Ph.D. candidate in the Département d'Informatique et Recherche Opérationnelle of the Université de Montréal. His research interests relate to formal methods and their application in the design and verification of complex electronic systems at high levels of abstraction. Luigi Logrippo received a degree in law from the University of Rome (Italy) in 1961, and in the same year he started a career in computing. He worked for several computer companies and in 1969 he obtained a Master of Computer Science from the University of Manitoba, followed by a Ph.D. of Computer Science from the University of Waterloo in 1974.He was with the University of Ottawa for 29 years, where he was Chair of the Computer Science Department for 7 years. In 2002 he moved to the Université du Québec en Outaouais, Département d'Informatique et Ingénierie, while remaining associated with the University of Ottawa as an Adjunct Professor.His interest area is formal and logic-based methods and their applications in the design of communications systems. For a number of years he worked on the development of tools and methods for the language LOTOS. Current research deals with the formal analysis of advanced communications services made possible by internet telephony, of the policies that govern them, and of their interactions, in application areas such as presence features and e-commerce contracts. Jacques Sincennes is a research programmer/systems analyst at the University of Ottawa, School of Information Technology and Engineering. He has held this position for the past 17 years. He is coauthor of a number of papers and a patent application.An erratum to this article is available at .     

Modelling of fluid properties in hydraulic positive displacement machines

This paper presents a numerical model for the simulation of a swash-plate axial piston pump, focusing on the characterization of fluid properties.As it is well known, the reduction of flow oscillations (which generates pressure ripples and produces vibration and noise in the entire circuit) and the avoidance of cavitation are the major problems in the design of these pumps. Developing a simulation code can be very useful for component optimisation in order to predict and reduce the undesired phenomena. The paper first gives a quick overview on a previously developed pump model; afterwards four different models of the fluid are presented: they take into account cavitation in different ways. Their aim at characterizing as well as possible the unsteady and erratic cavitation features in a simplified manner, in order to apply the models to the simulation of hydraulic components.In the second part of the paper an application is shown of these models to an axial piston pump: a few results are presented and compared with available test data. The effects of the fluid models on the predicted pump performance are shown and commented.     

Crystallisation of high density polyethylene from dilute solution: Heterogeneous nucleation

The self-seeding crystallisation technique is applied to a dilute solution of polyethylene in xylene containing, in suspension, foreign particles; data concerning some pigments usually employed for colouring the plastics are reported. It is shown that this method allows easy demonstration of the interactions existing between the dissolved polymer and the pigment; at the same time, it is possible to study the morphology which is evolved as a consequence of these interactions under particularly simple conditions as only a small amount of polymer crystallises on the pigment particles. The behaviour of several pigments is consistent with the results obtained by crystallising the bulk polyethylene coloured with the same pigments. Some unusual morphologies are made evident.     

Preparation and physico-chemical characterisation of microporous polysaccharidic hydrogels

A new technique to obtain microporous hydrogels was realised. It permits us to obtain a microporous structure directly on the already cross-linked hydrogel. It consists in stratifying the already cross-linked hydrogel on to a filter with known porosity and forcing the CO2 bubbles, derived from the addition of HCl to a porogen salt (NaHCO3), to cross through the filter first and then the matrix. By changing the porosity of the filter, it was possible to modulate the porous morphology of the hydrogels. The polysaccharides selected were hyaluronane, alginate, and carboxymethylcellulose. The influence of the porous morphology on the physico-chemical properties of the gel has been evaluated by FT-IR, FRAP, calorimetric, water uptake, and rheological analysis.     

Morphological evaluation of bioartificial hydrogels as potential tissue engineering scaffolds

Poly(vinyl alcohol) hydrogels prepared by freeze-thawing procedure represent synthetic systems widely investigated as non-biodegradable scaffolds for tissue regeneration. In order to improve the biocompatibility properties of pure poly(vinyl alcohol) (PVA) hydrogels, blends of PVA with different biological macromolecules, such hyaluronic acid, dextran, and gelatin were prepared and used to produce bioartificial hydrogels. The porosity characteristics of these hydrogels were investigated by scanning electron microscopy and mercury intrusion porosimetry. The morphology of bioartificial hydrogels was evaluated and compared with that of pure PVA hydrogels. In particular the effect exerted by each biological component on pore size and distribution was investigated. The obtained results indicate that when a natural macromolecule is added to PVA the internal structure of the material changes. A small amount of biopolymer induces the structural elements of PVA matrix to take on a well evident lamellar appearance and an apparent preferential orientation. Comparing the results of SEM and mercury intrusion porosimetry it was concluded that hydrogels containing 20% of biological component have the most regular structure and at the same time the lowest total porosity. On the contrary samples with the highest content of natural polymer (40%) show the less regular structure and the highest total porosity.     

Global analysis of the riverine transport of 90Sr and 37Cs

Atmospheric nuclear weapons explosions and large-scale nuclear accidents may contaminate large areas of land with the long-lived radionuclides 137Cs and 90Sr. The mobility and bioavailability of these radionuclides in the environment is dependent primarily on soil characteristics and changes significantly over time after fallout (1-4). Radioisotope concentrations in different rivers and at different times after fallout vary over 2-3 orders of magnitude. Many previous studies have concentrated on the interactions of radiocesium and radiostrontium with various environmental components, but there are currently no operative models fortheirtransport over large spatial areas. We collected time-series measurements of 90Sr and 137Cs in 25 major European and Asian rivers and (using digital data sets with global coverage) determined characteristics of each of the rivers' catchments. This work has established, for the first time, a quantitative link between riverine transport of these radioisotopes and catchment and soil characteristics at a global scale. A generalized predictive model accounting for time changes in river concentrations and variation in catchment characteristics is developed. This can be used to predict the long-term riverine transport of these radiologically important radionuclides following any large-scale nuclear incident in North America, Europe, or (European and Asian) Russia.