Sequence Modelling For Analysing Student Interaction with Educational Systems

The analysis of log data generated by online educational systems is an important task for improving the systems, and furthering our knowledge of how students learn. This paper uses previously unseen log data from Edulab, the largest provider of digital learning for mathematics in Denmark, to analyse the sessions of its users, where 1.08 million student sessions are extracted from a subset of their data. We propose to model students as a distribution of different underlying student behaviours, where the sequence of actions from each session belongs to an underlying student behaviour. We model student behaviour as Markov chains, such that a student is modelled as a distribution of Markov chains, which are estimated using a modified k-means clustering algorithm. The resulting Markov chains are readily interpretable, and in a qualitative analysis around 125,000 student sessions are identified as exhibiting unproductive student behaviour. Based on our results this student representation is promising, especially for educational systems offering many different learning usages, and offers an alternative to common approaches like modelling student behaviour as a single Markov chain often done in the literature.Comment: The 10th International Conference on Educational Data Mining 201

Thermal radiation dominated heat transfer in nanomechanical silicon nitride drum resonators

Nanomechanical silicon nitride (SiN) drum resonators are currently employed in various fields of applications that arise from their unprecedented frequency response to physical quantities. In the present study, we investigate the thermal transport in nanomechanical SiN drum resonators by analytical modelling, computational simulations, and experiments for a better understanding of the underlying heat transfer mechanism causing the thermal frequency response. Our analysis indicates that radiative heat loss is a non-negligible heat transfer mechanism in nanomechanical SiN resonators limiting their thermal responsivity and response time. This finding is important for optimal resonator designs for thermal sensing applications as well as cavity optomechanics.Comment: 8 pages, 4 figures in main text, 3 figures in supplementar

Osmotically driven pipe flows and their relation to sugar transport in plants

In plants, osmotically driven flows are believed to be responsible for translocation of sugar in the pipe-like phloem cell network, spanning the entire length of the plant. In this paper, we present an experimental and theoretical study of transient osmotically driven flows through pipes with semipermeable walls. We extend the experimental work of Eschrich, Evert and Young \cite[]{Eschrich:1972} by providing a more accurate version of their experiment allowing for better comparison with theory. In the experiments we measure the dynamics and structure of a "sugar front", i.e. the transport and decay of a sudden loading of sugar in a pipe which is closed in both ends. We include measurements of pressure inside the membrane tube allowing us to compare the experiments directly with theory and, in particular, to confirm quantitatively the exponential decay of the front in a closed tube.In a novel setup we are able to measure the entire concentration profile as the sugar front moves. In contrast to previous studies we find very good agreement between experiment and theory. In the limit of low axial resistance (valid in our experiments as well as in many cases in plants) we show that the equations can be solved exactly by the method of characteristics yielding, in general, an implicit solution. Further we show that under more general conditions the equations of motion can be rewritten as a single integro-differential equation, which can be readily solved numerically. The applicability of our results to plants is discussed and it is shown that it is probable that the pressure-flow hypothesis can account for short distance transport of sugar in plants.Comment: 34 pages, Submitted to Journal of Fluid Mechanics on May 28, 200

Gut bacteria and necrotizing enterocolitis: cause or effect?

Development of necrotising enterocolitis (NEC) is considered to be dependent on the bacterial colonisation of the gut. With little concordance between published data and a recent study failing to detect a common strain in infants with NEC, more questions than answers are arising about our understanding of this complex disease

Hvordan lykkes med implementering av Taktskifte/Løft i Grong Sparebank og Lillestrøm Banken

Sammendrag: Oppgavens problemstilling er: Hvordan lykkes med implementering av Taktskifte/Løft i Grong- og Lillestrøm Sparebank? Vi vil i oppgaven se på hvordan konteksten til bankene er i forhold til hvordan utformingen på en endringsprosess burde være. Formålet med oppgaven er at bankene i Eika som skal gå i gang med endringene har verdifull informasjon som kan lette arbeidet med implementeringen gjennom å se hvordan 2 banker har valgt å gjennomføre dette. På denne måten kan de se hvilke utfordringer de støtte på underveis. Oppgaven ble strukturert som en casestudie hvor vi gjennomførte intervjuer med sentrale personer i de to studerte bankene. Videre ble kaleidoskopet av Balogun and Hailey (2008) brukt som oppslagsverk og struktur for oppgaven videre. Konteksten til begge bankene ble analysert og vi så på resultatet opp mot teorien på området. Generelt kan vi si at bankene hadde lagt opp endringsprosessen veldig likt som teorien foreslo. Det var dog noen resultater rundt kapabiliteten til de ansvarlige, samt målemetodene som skilte seg ut

Influence of reed beds (Phragmites australis) and submerged vegetation on pike (Esox lucius)

Eutrophication and reduced grazing have led to an expansion of the common reed (Phragmites australis) in ar-chipelago areas in the Baltic Sea, while at the same time the composition of submerged vegetation has changed. Although reed is important as nursery habitat for many fish species, extensive emergent vegetation may reduce biodiversity and abundance of predatory fish. Pike (Esox lucius) is a predatory fish whose larvae and young-of -the-year find both food and shelter in reed but use different micro-habitats during different life-stages. Here we investigate the influence of reed and submerged vegetation on abundance and body size of adult pike during the spawning season. We predicted that coastal bays with extensive but heterogeneous reed beds with higher cover of submerged vegetation would have more and larger pike than bays with smaller, homogenous reed belts or with less submerged vegetation. To test these predictions, we estimated abundance and size-structure of adult pike from catches in angling fishing among 22 bays in the Stockholm archipelago at the Swedish Baltic Sea coast. Our analyses show that catches of adult pike were positively associated with both extensive reed beds and cover of rooted submerged vegetation. However, pike size was not correlated with any vegetation variable, but instead increased with wave exposure and bay area. Our study suggests that reed beds and submerged vegetation are important for adult pike during the spawning season, and even the most extensive reed beds had no evident negative effect on pike populations. We could not see any clear relationship between emergent reed habitat and cover of submerged vegetation among the studied bays, and conclude that to maintain pike population during the spawning season it is important that coastal bays have sufficient amounts of both reed beds and rooted submerged vegetation