Children's reasoning with schemes in the context of science education: studies of exemplification, analogy and transformation

It is clear from common experiences that abstract ideas are often difficult to understand,\ud and that the use of concrete examples is often useful, perhaps always necessary. The\ud research investigates some aspects of the relation between abstraction and examples:\ud how 11-12 year old children move in their thinking between more and less generic\ud levels; between greater and lesser degrees of abstraction; from example to generalization\ud and vice versa, in the context of science education. The central interest is in how\ud children use and modify concrete reasoning schemes. Its significance is in eliciting deep\ud and implicit ideas which affect how children learn science. The empirical work consists\ud of four related studies. The analysis is both qualitative and quantitative, in both cases\ud looking for patterns in response.\ud The first study explores the limitations of the boundaries of ontological categories in\ud children's transformations of entities. Results provide evidence that ontological\ud categories such as natural kinds and artefacts exist in thinking and that schemes are the\ud "bridges" which can make possible even cross-ontological transformations.\ud The second study explores the way that dimensions organise various entities and\ud suggests a novel analysis of analogies. Results show that schemes appear in children's\ud reasoning as packages. The presence of one scheme may predict the presence of another.\ud Children use schemes such as "flow" and "path", which interact and modify one\ud another.\ud The use of examples in science teaching varies. The focus of the third study is on the\ud analysis of examples of ideas in terms of objects which can be seen schematically.\ud Results show that children are able to give consistent examples, in many cases different\ud from the examples in their text books. Schemes that are used by children in the\ud description of objects appear together across the various examples. Examples constrain\ud the schemes children use to describe entities that take part in them. Examples work\ud rather like metaphors.\ud The fourth study shows that children are able to establish connections between concrete\ud examples and generalizations. They think of some instances as better examples of ideas\ud than others. The fit between examples and ideas is good when schemes such as\ud `support', 'border', 'autonomous action' or better when several such anticipated\ud schemes, are satisfied and poor when some are and some not

Field Operation Planning for Agricultural Vehicles: A Hierarchical Modeling Framework

Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 9 (2007): Field Operation Planning for Agricultural Vehicles: A Hierarchical Modeling Framework. Manuscript PM 06 021. Vol. IX. February, 2007

Optimal Dynamic Motion Sequence Generation for Multiple Harvesters

Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 9 (2007): Optimal Dynamic Motion Sequence Generation for Multiple Harvesters. Manuscript ATOE 07 001. Vol. IX. July, 2007

Analysis of the detachment of citrus fruits by vibration using artificial vision

The vibratory behaviour of citrus fruits is studied using slow-motion cameras in order to gain a better understanding of the parameters involved in fruit detachment when mechanical harvesting is done using shakers. Single citrus fruits with a small portion of stem were vibrated using strokes from 60 mm to 180 mm and frequencies from 3 Hz to 18 Hz. The movement was recorded at 300 fps and the main parameters considered for fruit detachment were determined through the analysis of the video sequences. Image-processing algorithms created for this purpose were applied to the automated estimation of the centroid of the fruit, the angle of the stem pistil axis, and the position of some selected points in the fruit in each frame of the video sequences to obtain dynamic parameters such as the position, speed and acceleration of the fruit during the movement until it is detached. The signals obtained from the image processing were filtered, providing results in accordance with the calibration systems. In general, results suggest that the inertial forces transmitted to the fruit were lower than the tensile forces required to detach the fruit by pulling it in the stem pistil direction. The largest peaks were observed using long strokes that required fewer cycles for detachment. On the other hand, short strokes combined with high frequencies needed more cycles, and thus a fatigue phenomenon was present. Short strokes and low frequencies were unable to detach some fruit. (C) 2014 IAgrE. Published by Elsevier Ltd. All rights reserved.This work was founded by the Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria (INIA) through the projects RTA2009-00118-C02-01 and RTA2009-00118-C02-02, and co-founded by European FEDER founds.Torregrosa Mira, A.; Albert Gil, FE.; Aleixos Borrás, MN.; Ortiz Sánchez, MC.; Blasco Ivars, J. (2014). Analysis of the detachment of citrus fruits by vibration using artificial vision. Biosystems Engineering. 119:1-12. https://doi.org/10.1016/j.biosystemseng.2013.12.010S11211

Balanços energéticos agropecuários: uma importante ferramenta como indicativo de sustentabilidade de agroecossistemas.

No Brasil, pouca atenção se tem dado às formas e caminhos com que os fluxos energéticos se distribuem nos sistemas produtivos. Na agropecuária, a atenção tem sido voltada a novas fontes de energia (biomassa) ou em tecnologia alternativa, visando a racionalização do uso de energia fóssil ou elétrica. Entretanto, a agricultura tem se desenvolvido baseada fortemente na utilização intensiva de máquinas agrícolas, com conseqüente uso de combustíveis fósseis. Um fator de estrangulamento muito forte no consumo energético geral tem sido a utilização massiva de fertilizantes derivados do petróleo nos agroecossistemas. Estudos de Balanços Energéticos visam determinar os pontos de estrangulamento energético fundamentando a busca por tecnologias poupadoras de energia, especialmente aquelas de origem fóssil (combustível, fertilizante, agrotóxicos, energia despendida na fabricação das máquinas e implementos, etc.). No Brasil, a Região Sul, é onde se encontram vários trabalhos buscando uma agricultura mais auto-sustentável, do ponto de vista da utilização da energia. Em vista da possibilidade de eventuais futuras crises energéticas, o presente trabalho procura analisar o estado-da-arte dos estudos em Balanço Energético, no Brasil e no Mundo, como uma ferramenta de indicação da sustentabilidade dos sistemas agropecuários