Time-limited and band-limited environment: Signals and systems

Of concern is an environment made up of signals and systems tightly confined both in time and frequency. Such an environment is often encountered in transmission line circuits, radar, sonar, and optical circuits, and when the principal signals are well-defined sharp pulses. It will be seen that once this environment is achieved, the signals and systems possess some attractive properties. A conventional system may preserve the symmetry of a propagating signal or change its symmetry from even to odd or from odd to even. Another system may be used to predict the arrival of an incoming pulse with a high degree of accuracy. Electrical networks may also be associated with these properties. Approximation problems, existence theorems, and realization schemes will be addressed and developed.     

Perceived costs and benefits as determinants of user behaviour: an experiment with matchmaking

A cost-benefit approach is employed to model the discretionary use of a computerized information system. The model is constructed by integrating a systemic view of human-computer interaction with a contingency model for selecting decision strategies. It is then used to analyse the effect of presentation format on search behaviour.

An experiment on matchmaking was performed using two formats: sequential and parallel. Subjects were asked to find the best spouse for a candidate using an information retrieval system that displayed information about the individuals according to the subject's specific requests. The subject's search behaviour and perception of complexity were recorded. A first analysis of the protocols revealed different behaviours, as predicted by the cost-benefit mechanism. A second analysis incorporated a measure of individual differences in perception to gain a better understanding of the effects of display format on perceived complexity and, thereby, on behaviour. The findings support the use or the cost-benefit model. The design implications of the model are also discussed.     

A method of analysis of the relaxation data for evaluation of the chemical diffusion coefficient in the case of partial rate control by surface reaction

A general method of regression analysis of the experimental data concerning relaxation experiments on binary compounds for the evaluation of the chemical diffusion coefficient is presented for cases in which the surface reaction exerts a partial control of the overall equilibration kinetics, assuming that the surface reaction follows a linear type of rate law. A rigorous method of analysis of data for the case of exclusive rate control by solid-state diffusion is also developed as a special solution. Application of the method to theoretically calculated curves indicates the correctness of the procedure developed. Limitations connected with the possible occurrence of forms different from the linear for the surface rate law are finally considered.     

The model multiplicity problem: experimenting with real-timespecification methods

The object-process methodology (OPM) specifies both graphically and textually the system's static-structural and behavioral-procedural aspects through a single unifying model. This model singularity is contrasted with the multimodel approach applied by existing object oriented system analysis methods. These methods usually employ at least three distinct models for specifying various system aspects: mainly structure, function, and behavior. Object modeling technique (OMT), the main ancestor of the unified modeling language (UML), extended with timed statecharts, represents a family of such multimodal object oriented methods. Two major open questions related to model multiplicity vs. model singularity have been: 1) whether or not a single model, rather than a combination of several models, enables the synthesis of a better system specification; and 2) which of the two alternative approaches yields a specification that is easier to comprehend. The authors address these questions through a double-blind controlled experiment. To obtain conclusive results, real time systems, which exhibit a more complex dynamic behavior than nonreal time systems were selected as the focus of the experiment. We establish empirically that a single model methodology, OPM, is more effective than a multimodel one, OMT, in terms of synthesis. We pinpoint specific issues in which significant diiferences between the two methodologies were found. The specification comprehension results show that there were significant differences between the two methods in specific issues     

OPM vs. UML--Experimenting with Comprehension and Construction of Web Application Models

Object-Process Methodology (OPM), which is a holistic approach to modeling and evolving systems, views objects and processes as two equally important entities that describe the system's structure and behavior in a single model. Unified Modeling Language (UML), which is the standard object-oriented modeling language for software systems, separates the system model into various aspects, each of which is represented in a different view (diagram type).The exponential growth of the Web and the progress of Internet-based architectures have set the stage for the proliferation of a variety of Web applications, which are classified as hybrids between hypermedia and information systems. Such applications require a modeling approach that is capable of clearly specifying aspects of their architecture, communication, and distributive nature. Since UML and OPM are two candidates for this task, this study has been designed to establish the level of comprehension and the quality of the constructed Web application models using each one of these two approaches.In the experiment we carried out, third year undergraduate information systems engineering students were asked to respond to comprehension and construction questions about two representative Web application models. The comprehension questions related to the system's structure, dynamics, and distribution aspects. The results suggest that OPM is better than UML in modeling the dynamics aspect of the Web applications. In specifying structure and distribution aspects, there were no significant differences. The results further suggest that the quality of the OPM models students built in the construction part was superior to that of the corresponding UML models.     

Reducing risk factors for eating disorders: Comparison of an Internet- and a classroom-delivered psychoeducational program.

This controlled trial compared Internet- (Student Bodies [SB]) and classroom-delivered (Body Traps [BT]) psychoeducational interventions for the reduction of body dissatisfaction and disordered eating behaviors/attitudes with a control condition. Participants were 76 women at a private university who were randomly assigned to SB, BT, or a wait-list control (WLC) condition. Measures of body image and eating attitudes and behaviors were measured at baseline, posttreatment, and 4-month follow-up. At posttreatment, participants in SB had significant reductions in weight/shape concerns and disordered eating attitudes compared with those in the WLC condition. At follow-up, disordered behaviors were also reduced. No significant effects were found between the BT and WLC conditions. An Internet-delivered intervention had a significant impact on reducing risk factors for eating disorders. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Quantum logic, Hilbert space, revision theory

Our starting point is the observation that with a given Hilbert space H we may, in a way to be made precise, associate a class of non-monotonic consequence relations in such a way that there exists a one-to-one correspondence between the rays of H and these consequence relations. The projectors in Hilbert space may then be viewed as a sort of revision operators. The lattice of closed subspaces appears as a natural generalisation of the concept of a Lindenbaum algebra in classical logic. The logics presentable by Hilbert spaces are investigated and characterised. Moreover, the individual consequence relations are studied. A key concept in this context is that of a consequence relation having a pointer to itself. It is proved that such consequence relations have certain remarkable properties in that they reflect their metatheory at the object level to a surprising extent. The tools used in the investigation stem from two different areas of research, namely from the disciplines of non-monotonic logic on the one hand and from Hilbert space theory on the other. There exist surprising connections between these two fields of research the investigation of which constitutes the purpose of this paper.     

MOSAICA: A web-2.0 based system for the preservation and presentation of cultural heritage

The question of how to present cultural heritage resources in a way that attracts potential users is becoming important in our ever-changing world. This paper describes MOSAICA system – a web 2.0-based toolbox, dedicated for the preservation and presentation of cultural heritage. This paper also describes an evaluation study that examined MOSAICA system’s usability and social impact. Online questionnaires and semi-structured interviews were administered among users from Israel, France, and Poland. Findings indicated positive views related to MOSAICA’s usage in terms of knowledge gain, ease of use, and attractiveness. Findings also indicated that learning about the stories, customs, and traditions of diverse cultures, via hypertext narratives, may enhance positive dispositions toward open-mindedness, in general, and non-judgmental views, in specific. MOSAICA system provides a generic framework for users, of any culture and religion, to actively engage in preserving their heritage via activities such as investigation, exploration, and storytelling.     

Incremental arc segmentation algorithm and its evaluation

We present an incremental arc segmentation algorithm, which recovers the vectorized arc fragments obtained by the vectorization of a piece of arc image in a stepwise fashion. Due to proper threshold selection and consistent checking of cocircularity of the assumed arc pieces, the algorithm accurately constructs arcs from the vector input. Nearly 200 synthetic arcs, ranging in radius from five to 50 pixels, in open angle from 1/8π to 2π, and in thickness from one to nine pixels, are used in the experiments and evaluation. Parts of six real drawings, containing about 200 arcs, are also processed. The algorithm works well for arc segments greater than 10 pixels in radius, π/4 in angle, and one pixel in width