Phenomenology of the Lense-Thirring effect in the Solar System

Recent years have seen increasing efforts to directly measure some aspects of the general relativistic gravitomagnetic interaction in several astronomical scenarios in the solar system. After briefly overviewing the concept of gravitomagnetism from a theoretical point of view, we review the performed or proposed attempts to detect the Lense-Thirring effect affecting the orbital motions of natural and artificial bodies in the gravitational fields of the Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of the impact of several sources of systematic uncertainties of dynamical origin to realistically elucidate the present and future perspectives in directly measuring such an elusive relativistic effect.Comment: LaTex, 51 pages, 14 figures, 22 tables. Invited review, to appear in Astrophysics and Space Science (ApSS). Some uncited references in the text now correctly quoted. One reference added. A footnote adde

Learning from multimedia and hypermedia

Computer-based multimedia and hypermedia resources (e.g., the world wide web) have become one of the primary sources of academic information for a majority of pupils and students. In line with this expansion in the field of education, the scientific study of learning from multimedia and hypermedia has become a very active field of research. In this chapter we provide a short overview with regard to research on learning with multimedia and hypermedia. In two review sections, we describe the educational benefits of multiple representations and of learner control, as these are the two defining characteristics of hypermedia. In a third review section we describe recent scientific trends in the field of multimedia/hypermedia learning. In all three review sections we will point to relevant European work on multimedia/hypermedia carried out within the last 5 years, and often carried out within the Kaleidoscope Network of Excellence. According to the interdisciplinary nature of the field this work might come not only from psychology, but also from technology or pedagogy. Comparing the different research activities on multimedia and hypermedia that have dominated the international scientific discourse in the last decade reveals some important differences. Most important, a gap seems to exist between researchers mainly interested in a “serious” educational use of multimedia/ hypermedia and researchers mainly interested in “serious” experimental research on learning with multimedia/hypermedia. Recent discussions about the pros and cons of “design-based research” or “use-inspired basic research” can be seen as a direct consequence of an increasing awareness of the tensions within these two different cultures of research on education

Is a Design Rationale Vital when Predicting Change Impact? - A Controlled Experiment on Software Architecture Evolution

Software process improvement efforts often seek to shorten development lead-time. A potential means is to facilitate architectural changes by providing a design rationale, i.e. a documentation of why the architecture is built as it is. The hypothesis is that changes will be faster and more correct if such information is available during change impact analysis. This paper presents a controlled experiment where the value of having access to a retrospective design rationale is evaluated both quantitatively and qualitatively. Realistic change tasks are applied by 17 subjects from both industry and academia on two complex systems from the domain of embedded real-time systems. The results from the quantitative analysis show that, for one of the systems, there is a significant improvement in correctness and speed when subjects have access to a design rationale document. In the qualitative analysis, design rationale was considered helpful for speeding up changes and improving correctness. For the other system the results were inconclusive, and further studies are recommended in order to increase the understanding of the role of a design rationale in architectural evolution of software systems