Approximate Dynamic Programming via Sum of Squares Programming

We describe an approximate dynamic programming method for stochastic control problems on infinite state and input spaces. The optimal value function is approximated by a linear combination of basis functions with coefficients as decision variables. By relaxing the Bellman equation to an inequality, one obtains a linear program in the basis coefficients with an infinite set of constraints. We show that a recently introduced method, which obtains convex quadratic value function approximations, can be extended to higher order polynomial approximations via sum of squares programming techniques. An approximate value function can then be computed offline by solving a semidefinite program, without having to sample the infinite constraint. The policy is evaluated online by solving a polynomial optimization problem, which also turns out to be convex in some cases. We experimentally validate the method on an autonomous helicopter testbed using a 10-dimensional helicopter model.Comment: 7 pages, 5 figures. Submitted to the 2013 European Control Conference, Zurich, Switzerlan

Devons-nous utiliser des phénomènes évolutifs en introduction à l'étude de l'électricité ? Le cas de la résistance

La plupart des curricula traditionnels ou constructivistes proposés jusqu'à maintenant en électricité sont centrés sur des tâches liées à des états stationnaires de circuits en courant continu, impliquant le traitement d'un nombre limité de phénomènes. Ils ne s'intéressent qu'aux effets du courant à un instant déterminé, et non à leur évolution dans le temps. Dans le champ expérimental de l'introduction à l'électricité, nous proposons d'étudier des phénomènes évolutifs. Nous les utilisons dans le cadre de l'enseignement de la notion de résistance électrique. Nous pensons que la combinaison de situations mettant en oeuvre des états stationnaires et des phénomènes évolutifs dans un enseignement sur la résistance peut aider les élèves à reconsidérer leur conception intuitive du transfert de l'énergie, et augmenter leur compréhension de faits expérimentaux liés à un modèle circulatoire du fonctionnement d'un circuit

Différenciation conceptuelle : un enseignement d'hydrostatique, fondé sur le développement et la contradiction des conceptions des élèves

Cet article propose une stratégie susceptible de faciliter la différenciation conceptuelle chez des élèves de l'enseignement obligatoire. Cette stratégie est mise en oeuvre pour améliorer la différenciation des notions de pression et de force pressante par des élèves dont la connaissance initiale à propos des liquides est dominée par une notion «parente» indifférenciée. Cette notion recouvre des caractéristiques à la fois de la pression et de la force pressante. La stratégie s'appuie sur ce qui, dans la connaissance première des élèves, est compatible avec le modèle scientifique; elle les conduit à une situation conflictuelle lorqu'ils ont acquis la compétence nécessaire pour percevoir des contradictions dans leurs explications des faits expérimentaux. Les résultats de l'application de cette stratégie dans l'enseignement secondaire grec sont positifs

Transferring a Teaching Learning Sequence Between Two Different Educational Contexts : the Case of Greece and Finland

In the present paper, we report on the idea of exchanging educational innovations across European countries aiming to shed light on the following question: how feasible and useful is it to transfer an innovation across different national educational settings? The innovation, in this case, Inquiry-Based Teaching Learning Sequences, is recognized as a crucial component of renewal science teaching in European countries. Two local working groups from two different Universities, in Finland and Greece, were created consisting of researchers and experienced primary teachers. The transfer from Greece to Finland was rather challenging because of the differences between the two educational contexts. The initial, as well as the revised Teaching Learning Sequence, were implemented for 11-12-year-old students including the content to be taught, that is Floating-Sinking phenomena and density, and the learning environment aspects such as learning Control of Variables Strategy. A combination of qualitative and quantitative research methods was implemented in order to formulate concrete recommendations on feasible and useful aspect. The feasible aspect adduces answers to the query of "how" this transfer worked in practice. Concerning this aspect, the recognition of what is innovative for each national partner was recognized as a crucial factor for the design and revision of both Teaching Learning Sequences. The useful aspect illuminates students' improvement in the achievement of conceptual as well as procedural knowledge. The results revealed that the psychological paths that bring about this success are ecumenical and independent of the history of the educational group.Peer reviewe

Promoting Students’ Interest and Motivation Towards Science Learning : the Role of Personal Needs and Motivation Orientations

This study aimed to design a teaching sequence for science education that enabled lower secondary school students to enhance their motivation towards science. Further, it looked to examine the way the designed teaching sequence affected students with different motivational profiles. Industry site visits, with embodied theory-based motivational features were included as part of the designed teaching sequence. The sequence was implemented in Finland and Greece with 54 participants, 27 from each country. Quantitative data was collected using the Evaluation of Science Inquiry Activities Questionnaire, based on the Intrinsic Motivation Inventory but did not map the expected outcomes. Interviews, however, showed that students with different motivational profiles found aspects within the module that met their psychological needs as explained by Self-Determination Theory. The results offer a perspective to adolescents’ psychological needs along with some insights into how students mediate the way they value an activity in the context of science education.Peer reviewe

A Sex-Specific Metabolite Identified in a Marine Invertebrate Utilizing Phosphorus-31 Nuclear Magnetic Resonance

Hormone level differences are generally accepted as the primary cause for sexual dimorphism in animal and human development. Levels of low molecular weight metabolites also differ between men and women in circulating amino acids, lipids and carbohydrates and within brain tissue. While investigating the metabolism of blue crab tissues using Phosphorus-31 Nuclear Magnetic Resonance, we discovered that only the male blue crab (Callinectes sapidus) contained a phosphorus compound with a chemical shift well separated from the expected phosphate compounds. Spectra obtained from male gills were readily differentiated from female gill spectra. Analysis from six years of data from male and female crabs documented that the sex-specificity of this metabolite was normal for this species. Microscopic analysis of male and female gills found no differences in their gill anatomy or the presence of parasites or bacteria that might produce this phosphorus compound. Analysis of a rare gynandromorph blue crab (laterally, half male and half female) proved that this sex-specificity was an intrinsic biochemical process and was not caused by any variations in the diet or habitat of male versus female crabs. The existence of a sex-specific metabolite is a previously unrecognized, but potentially significant biochemical phenomenon. An entire enzyme system has been synthesized and activated only in one sex. Unless blue crabs are a unique species, sex-specific metabolites are likely to be present in other animals. Would the presence or absence of a sex-specific metabolite affect an animal's development, anatomy and biochemistry

Alteration of the phospho- or neutral lipid content and fatty acid composition in Listeria monocytogenes due to acid adaptation mechanisms for hydrochloric, acetic and lactic acids at pH 5.5 or benzoic acid at neutral pH

This study provides a first approach to observe the effects on Listeria monocytogenes of cellular exposure to acid stress at low or neutral pH, notably how phospho- or neutral lipids are involved in this mechanism, besides the fatty acid profile alteration. A thorough investigation of the composition of polar and neutral lipids from L. monocytogenes grown at pH 5.5 in presence of hydrochloric, acetic and lactic acids, or at neutral pH 7.3 in presence of benzoic acid, is described relative to cells grown in acid-free medium. The results showed that only low pH values enhance the antimicrobial activity of an acid. We suggest that, irrespective of pH, the acid adaptation response will lead to a similar alteration in fatty acid composition [decreasing the ratio of branched chain/saturated straight fatty acids of total lipids], mainly originating from the neutral lipid class of adapted cultures. Acid adaptation in L. monocytogenes was correlated with a decrease in total lipid phosphorus and, with the exception of cells adapted to benzoic acid, this change in the amount of phosphorus reflected a higher content of the neutral lipid class. Upon acetic or benzoic acid stress the lipid phosphorus proportion was analysed in the main phospholipids present: cardiolipin, phosphatidylglycerol, phosphoaminolipid and phosphatidylinositol. Interestingly only benzoic acid had a dramatic effect on the relative quantities of these four phospholipids