Destabilization by noise of tranverse perturbations to heteroclinic cycles: a simple model and an example from dynamo theory

We show that transverse perturbations from structurally stable heteroclinic cycles can be destabilized by surprisingly small amounts of noise, even when each individual fixed point of the cycle is stable to transverse modes. A condition that favours this process is that the linearization of the dynamics in the transverse direction be characterized by a non-normal matrix. The phenomenon is illustrated by a simple two-dimensional switching model and by a simulation of a convectively driven dynamo

Uncovering the problem-solving process to design effective worked examples.

Van Gog, T. (2006). Uncovering the problem-solving process to design effective worked examples. Unpublished doctoral dissertation. Open University of the Netherlands, The Netherlands

Voorbeeldig leren

__Abstract__ Rede in verkorte vorm uitgesproken bij de aanvaarding van het ambt van bijzonder hoogleraar

A Grammar Compression Algorithm based on Induced Suffix Sorting

We introduce GCIS, a grammar compression algorithm based on the induced suffix sorting algorithm SAIS, introduced by Nong et al. in 2009. Our solution builds on the factorization performed by SAIS during suffix sorting. We construct a context-free grammar on the input string which can be further reduced into a shorter string by substituting each substring by its correspondent factor. The resulting grammar is encoded by exploring some redundancies, such as common prefixes between suffix rules, which are sorted according to SAIS framework. When compared to well-known compression tools such as Re-Pair and 7-zip, our algorithm is competitive and very effective at handling repetitive string regarding compression ratio, compression and decompression running time

A test of the testing effect: Acquiring problem-solving skills from worked examples.

Van Gog, T., & Kester, L. (2012). A test of the testing effect: Acquiring problem-solving skills from worked examples. Cognitive Science, 36, 1532-1541. doi:10.1111/cogs.12002The „testing effect‟ refers to the finding that after an initial study opportunity, testing is more effective for long-term retention than restudying. The testing effect seems robust and is a finding from the field of cognitive science that has important implications for education. However, it is unclear whether this effect also applies to the acquisition of problem-solving skills, which is important to establish given the key role problem solving plays in for instance math and science education. Worked examples are an effective and efficient way of acquiring problem-solving skills. Forty students either only studied worked examples (SSSS) or engaged in testing after studying an example by solving an isomorphic problem (STST). Surprisingly, results showed equal performance in both conditions on an immediate retention test after five minutes, but the SSSS condition outperformed the STST condition on a delayed retention test after one week. These findings suggest the testing effect might not apply to acquiring problem-solving skills from worked examples.This research was funded by a Veni Grant from the Netherlands Organization for Scientific Research (NWO) awarded to Tamara van Gog (# 451-08-003). During the realization of this work, Liesbeth Kester was also supported by a Veni grant from NWO (# 451-07-007)