Sulla stabilità dei metodi Pseudo Runge-Kutta

Sommario Si studia la stabilità dei metodi pseudo Runge-Kutta. Si confrontano gli intervalli di stabilità con gli analoghi metodi di Runge-Kutta e a differenze finite.

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On study the stability of Pseudo Runge-Kutta methods. On compare the space of stability with the analogous Runge Kutta and multi-steps methods.

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Lavoro eseguito nell'ambito dei gruppi di ricerca del C.N.R., L'antore ringrazia il Prof.Wolf Gross per le utili discussioni sull'argomento. Della presente nota è stata data comunicazione al IX Congresso U.M.I.     

Analyzing, modelling, and specifying visual interaction

 This paper discusses the processes underlying human-computer visual interaction, thereby analysing the characteristics of visual interaction; a model and a theory of visual interaction, from which a formal specification of visual interactive systems that are trustable by their users can be derived, are also illustrated. Such a theory is called theory of visual sentences, since each message on the computer screen is described as a visual sentence, i.e., an element of a visual language that specifies the interaction. The concept of relational structure is introduced to take into account different kinds of relations which can exist among the characteristic patterns present in a visual sentence. A formal model of the dynamics of visual interaction is presented, which is specified as transformations of visual sentences, modelled through visual rewriting systems, and transformations of relational structures. Particular attention is given to usability issues so as to satisfy relevant features needed to allow non-ambiguity of interpretation, adequate communication, determinism and system viability. An example of visual interaction is given where an immunologist interacts with a simulation of the human immune system. This work was supported by the Italian Ministry of University and Research under the Research Project of National Interest “Specification, Design and Development of Visual Interactive Systems”.     

SUE inspection: an effective method for systematic usabilityevaluation of hypermedia

SUE inspection is a novel usability evaluation method for hypermedia, which falls into the category of inspection methods. Its primary goal is to favor a systematic usability evaluation (SUE), for supplying hypermedia usability inspectors with a structured flow of activities, allowing them to obtain more reliable, comparable, and cost-effective evaluation results. This is obtained especially due to the use of evaluation patterns, called abstract tasks (AT), which describe in details the activities that evaluators must carry out during inspection. AT helps share and transfer evaluation know-how among different evaluators, thus making it easier to learn the SUE inspection method by newcomers. A further notable advantage provided by the SUE inspection over other existent approaches is that it focuses on navigation and information structures, making evident some problems that other "surface-oriented" approaches might not reveal. This paper describes the SUE inspection for hypermedia. It also reports on a validation experiment, involving 28 evaluators, that has shown the major effectiveness and efficiency of the SUE inspection for hypermedia, with respect to traditional heuristic evaluation techniques     

An adaptive visual environment for digital libraries

CDL (Corporate Digital Library) is a prototypical intelligent digital library service that is currently being developed at the University of Bari, as an evolution of a previous project named IDL (Intelligent Digital Library). Among the characterizing features of CDL there are a retrieval engine and several facilities available for the library users. In this paper, we present the web-based visual environment we have developed with the aim of improving user-library interaction. The CDL environment is equipped with some novel visual tools that are primarily intended for inexperienced users, who represent most of the users that usually have access to digital libraries. Machine Learning techniques have been exploited in CDL for document analysis, classification, and understanding, as well as for building a user modeling module, which is the basic component for providing CDL with user interface adaptivity. This feature is also discussed in the paper. Received: 15 December 1997 / Revised: June 1999     

A method for high-order multipoint boundary value problems with Birkhoff-type conditions

In this paper an efficient numerical method for solving a class of multipoint boundary value problems with special boundary conditions of Birkhoff-type is presented. After a quick reference to Birkhoff-type interpolation polynomial which satisfies the particular conditions, and a result on the existence and uniqueness of solution of the given problem, an algorithm is introduced to find a polynomial that approximates the solution. It is a general collocation method. Then an a priori estimation of the error of this approximation is given. Finally, to show the efficiency and the applicability of the method, numerical results are presented. These numerical experiments provide favourable comparisons with the NDSolve command of Mathematica.     

Study of the activity of Grubbs catalyst-functionalized multiwalled carbon nanotubes in the ring opening metathesis polymerization

The synthesis of polynorbornene by ring opening metathesis polymerization (ROMP), in the presence of 1st and 2nd generation Grubbs catalyst-functionalized multiwalled carbon nanotubes (MWCNT), has been studied. MWCNTs were obtained by catalytic chemical vapour deposition (CCVD) of ethylene. A full characterization of the 1st and 2nd generation Grubbs catalyst-functionalized nanotubes was performed by FTIR and TG-DTG-MS. The amount of catalyst grafted to the nanotube surface was estimated. The activity of the catalyst-functionalized nanotubes in ROMP of 2-norbornene was found to be similar to that of bare 1st and 2nd generation Grubbs catalysts. The characterization of polynorbornene-carbon nanotube composites shows that the nanotubes are well dispersed in the polymer matrix.     

Intramuscular versus vaginal progesterone in assisted reproduction: a comparative study

Thirty-one patients with mild-to-moderate Alzheimer's disease (AD) underwent a test battery of complex visual tasks. We assessed the scores using a principal-factor analysis to elucidate the underlying deficits. There were three independent factors: The first factor included the tasks of identifying and comparing forms of visual stimuli. The second factor consisted of digit span and digit symbol tasks, and the third factor consisted of a specified visual counting task. We considered these three factors as representing the dysfunctions of object recognition, general attention and spatial recognition, respectively. These results underline the disturbances of the two visual systems, object vision and spatial vision, in early-AD patients.