The Stability of Flood Defences on Permeable Soils: The London Avenue Canal Failures in New Orleans

in Sixth International Conference on Case Histories in Geotechnical Engineering (2008, August)

The two failures of the London Avenue Canal floodwalls contributed largely to the flooding of central New Orleans due to hurricane Katrina. In this paper, both failures are analyzed and compared to each ... [more ▼]

The two failures of the London Avenue Canal floodwalls contributed largely to the flooding of central New Orleans due to hurricane Katrina. In this paper, both failures are analyzed and compared to each other since the flood defenses are both located on permeable soils. Photo’s observation and calculations are used for the analysis. Both failures are caused by the permeable sand layer below the floodwall that allowed high pore water pressures to develop below the floodwall. However, the south breach seems to be caused by the piping failure mechanism and the north breach by loss of stability. At the South breach, the impermeable top layer was thicker than at the North breach, increasing the stability. The North beach was less vulnerable for piping and the lack of stability caused a large breach. The London Avenue Canal failures are a clear yet tragic example of the failure of flood defenses on permeable soils. The failures show that multiple failure mechanism may occur and since there are many flood defenses on permeable soils world wide, the lessons from Katrina can be used to prevent future catastrophes. [less ▲]

Necessary and sufficient conditions for dynamical structure reconstruction of LTI networks

in IEEE Transactions on Automatic Control (2008), 53(7), 1670-1674

This paper formulates and solves the network reconstruction problem for linear time-invariant systems. The problem is motivated from a variety of disciplines, but it has recently received considerable ... [more ▼]

This paper formulates and solves the network reconstruction problem for linear time-invariant systems. The problem is motivated from a variety of disciplines, but it has recently received considerable attention from the systems biology community in the study of chemical reaction networks. Here, we demonstrate that even when a transfer function can be identified perfectly from input–output data, not even Boolean reconstruction is possible, in general, without more information about the system.We then completely characterize this additional information that is essential for dynamical reconstruction without appeal to ad-hoc assumptions about the network, such as sparsity or minimality. [less ▲]

Mortalitätssalienz und Angstbewältingung im Kontext einer Krebserkrankung

Doctoral thesis (2008)

Complex problem as competence: Item difficulty and competence levels in dynamic situations

Poster (2008, July 22)

Intergeo - Interoperable Interactive Geometry for Europe

Poster (2008, July 09)

Mathematics teacher development and technology: towards an International GeoGebra Institute

Poster (2008, July 09)

Research indicates that despite the numerous benefits of using technology in mathematics education, the process of embedding technology in classrooms is slow and complex. Most teachers need more than just ... [more ▼]

Research indicates that despite the numerous benefits of using technology in mathematics education, the process of embedding technology in classrooms is slow and complex. Most teachers need more than just being provided with technology if the benefits of technology are to be substantially realized. It has been suggested that adequate training and collegial support boost teachers' willingness to integrate technology into their teaching and to develop successful technology-assisted teaching practices. GeoGebra is free open-source dynamic software for mathematics teaching and learning that offers geometry and algebra features in a fully connected software environment. Its pool of free interactive materials and user forum are examples of online collaboration of a world-wide community of mathematics educators. In this poster presentation, we will outline the emergence of the software GeoGebra and its recent developments as well as the first steps towards (using present tense to show that work has already been done) International GeoGebra Institute to be able to offer structured training and support for teachers who are ready to integrate GeoGebra into their classrooms. In addition, we will organize and coordinate research projects in relation to GeoGebra to enhance the development of training and support materials. While our initial plan is to establish an IGI site at Florida Atlantic University (USA), in the long run our goal is to collaborate with colleagues and set up other institutes in various locations around the world. [less ▲]

Teaching and Learning Calculus with Free Dynamic Mathematics Software GeoGebra

Scientific Conference (2008, July 08)

Research suggests that despite the numerous benefits of using technology in mathematics education, the process of embedding technology in classrooms is slow and complex (Cuban, Kirkpatrick, & Peck, 2001 ... [more ▼]

Research suggests that despite the numerous benefits of using technology in mathematics education, the process of embedding technology in classrooms is slow and complex (Cuban, Kirkpatrick, & Peck, 2001). GeoGebra is open-source software for mathematics teaching and learning that offers geometry, algebra and calculus features in a fully connected and easy-to-use software environment. It is available free of charge and used by thousands of students and teachers around the world in classrooms and at home. In this presentation we will both present applications of GeoGebra for calculus teaching at the high school and college level, as well as raise some of the implications of free and easy-to-use software such as GeoGebra for technology integration into the teaching and learning of calculus. [less ▲]

Le tutorat comme métier impossible et de l'impossible. Les apports de la psychanalyse et les moyens institutionnels du tuteur dans le cadre d'une formation initiale d'enseignants

Doctoral thesis (2008)

Working memory, phonological awareness, and developing language skills

Poster (2008, July)

The relationship between working memory, verbal short-term memory, phonological awareness, and developing language skills was explored longitudinally in children growing up in a multilingual society. A ... [more ▼]

The relationship between working memory, verbal short-term memory, phonological awareness, and developing language skills was explored longitudinally in children growing up in a multilingual society. A sample of 121 children from Luxembourg were followed from the end of Kindergarten to 1st Grade, and completed multiple assessments of verbal short-term memory, complex working memory, phonological awareness, native and foreign vocabulary knowledge, language comprehension, and reading. Results indicate that relations between the measures were best characterized by a model consisting of two related but separable constructs – corresponding to verbal short-term memory and the central executive – that were distinct from phonological awareness. The data further showed that assessments of verbal short-term memory in Kindergarten significantly predicted vocabulary knowledge and comprehension in native and foreign languages one year later: Central executive and verbal short-term memory measures in Kindergarten were significantly associated with reading in 1st Grade and phonological awareness, indexed by rhyme detection, did not predict any of the language constructs one year later. The findings lend strong support to the position that verbal short-term memory is one of the main contributors to new word learning in both native and non-native languages by supporting the formation of stable phonological representations of new words in long-term memory. Verbal short-term memory also seems to play a significant role in the syntactic comprehension of sentences. The heard material might be kept active in verbal short-term memory while the child is listening to the sentence and processing it for comprehension. Finally working memory appears to make significant contributions to reading development. One explanation of these findings is that literacy classroom activities often impose heavy demands on working memory, the capacity of which therefore has a direct effect on the frequency of task failure or success in these classroom activities which consequently influences the rate of learning. [less ▲]

Gewalt in der Schule: Ursachen und Prävention

Presentation (2008, July)