Trace gas measurements from infrared satellite for chemistry and climate applications

Space-borne thermal infrared instruments working in the nadir geometry are providing spectroscopic measurements of species that impact on the chemical composition of the atmosphere and on the climate forcing: H2O, CO2, N2O, CH4, CFCs, O3, and CO. The atmospheric abundances obtained from the analysis of IMG/ADEOS measurements are discussed in order to demonstrate the potential scientific return to be expected from future missions using advanced infrared nadir sounders. Some strengths and limitations of passive infrared remote sensing from space are illustrated. © 2003 European Geosciences Union.

Analyzing and selecting tasks for mathematics teaching: a heuristic

In planning units and lessons every day, teachers face the problem of designing a sequence of activities to promote learning. In particular, they are expected to foster the development of learning goals in their students. Based on the idea of learning path of a task, we describe a heuristic procedure to enable teachers to characterize a learning goal in terms of its cognitive requirements and to analyze and select tasks based on this characterization. We then present an example of how a group of future teachers used this heuristic in a preservice teachers training course and discuss its contributions and constraints.

Doctoral programs and academic research: Mathematics education in the Spanish university

We have shown a description of the changes and innovations happened in Spain concerning the research on Mathematics Education during the last 25 years, highlighting specially the fast development of the last 10 years. Neither of these great and striking changes would have taken place if there was not been an evolution within the Spanish society, and particularly, within its educational system. Thanks to this, we have found the appropriate conditions for research development.

Basic components in the scienctific didactical training of the secondary school mathematics teachers

Secondary mathematics teacher training in Spain is currently the subject of a heated revision debate. The speed of social, cultural, scientific and economic changes have left a hundred years old teacher training model well behind. However, academical inertia and professional interests are impeding a real new training of the mathematics teacher as an autonomous mathematical educator. Teachers of Didactic of Mathematics and the Spanish Associations of mathematics teachers have recently been discussing the issue. Their conclusions are included here.

The role of technology in the study of semiotic representations in mathematics

En este trabajo resumimos algunas reflexiones sobre el papel que pueden desarrollar la tecnología en el estudio de sistemas semióticos de representación, y que constituyen el núcleo para la comprensión de los procesos de construcción del conocimiento matemático de los estudiantes. La cita corresponde con el resumen de una página publicado.

How mathematics is defined and measured in PISA 2003

In this report I present a summary of the three dimensions used in PISA 2003assessment in mathematics: Content, Process and Situation, and I includesome examples of items.

Proyecto "mete" (mathematics education traditions of europe): el foco matemático

Este artículo presenta los resultados de un estudio sobre las tradiciones de enseñanza en cuatro países europeos: Bélgica (Flandes), Inglaterra, Hungría y España. Se trata de un estudio a pequeña escala en el que se emplean métodos cuantitativos y cualitativos, y que, en lugar de pretender obtener generalizaciones, está orientado a arrojar alguna luz que posibilite la mejora de la enseñanza y el aprendizaje de las matemáticas. Establece comparaciones con los resultados de los test TIMSS y PISA y extrae alguna conclusión para la formación inicial de maestros y profesores de matemáticas. Extraemos de éste los resultados relativos a los datos cuantitativos y nos centramos en el foco matemático.

The Experience of Security in Mathematics

In this paper, we report some findings from an investigation of a topic related to affect and mathematics which is not well-represented in the literature. For some mathematicians, mathematics itself is a source of security in an uncertain world, and we investigated this feeling and experience in the case of 19 adult mathematicians working in universities and schools in Greece. The focus reported here is on ways that a relationship with mathematics offers a sense of permanence and stability on the one hand, and an assurance of novelty and progress on the other.

How mathematics is defined and measured in PISA 2003

Description of some variables used in PISA 2003 project to asses competences.

Characterizing mentors’ performance in mathematics teacher education

This study describes the performance of the mentors in a blended graduate-level training program of teachers in the field of secondary school mathematics. We codified and analyzed the mentors’ comments on the projects presented by the groups of in-service teachers for whom they (the mentors) were responsible. To do this, we developed a structure of categories and codes based on a combination of a literature review, a model of teacher learning, and a cyclical review of the data. We performed two types of analysis: frequency and cluster. The first analysis permitted us to characterize the common actions shared by most of the mentors. From the second, we established three profiles of the mentors’ actions.

Molecular dynamics simulation of adsorption of Ag particles on a graphite substrate

We have performed for the first time a molecular dynamics simulation of the adsorption of gas-phase Ag particles on a graphite substrate to provide an insight into the results of a comprehensive STM-based experiment on this system. Both pair-wise and many-body interatomic potentials have been employed, and a Morse-type Ag–C potential was specifically constructed to describe the interactions at the interface. Our simulation has successfully reproduced a significant portion of the experimental findings. We have also observed the intercalation of silver in graphite.

Mathematical modelling of the solidification of liquid tin with electromagnetic stirring

It is well known that during alloy solidification, convection currents close to the so-lidification front have an influence on the structure of dendrites, the local solute concentration, the pattern of solid segregation, and eventually the microstructure of the casting and hence its mechanical properties. Controlled stirring of the melt in continuous casting or in ingot solidification is thought to have a beneficial effect. Free convection currents occur naturally due to temperature differences in the melt and for any given configuration, their strength is a function of the degree of superheat present. A more controlled forced convection current can be induced using electro-magnetic stirring. The authors have applied their Control-Volume based MHD method [1, 2] to the problem of tin solidification in an annular crucible with a water-cooled inner wall and a resistance heated outer one, for both free and forced convection situations and for various degrees of superheat. This problem was studied experimentally by Vives and Perry [3] who obtained temperature measurements, front positions and maps of electro-magnetic body force for a range of superheat values. The results of the mathematical model are compared critically against the experimental ones, in order to validate the model and also to demonstrate the usefulness of the coupled solution technique followed, as a predictive tool and a design aid. Figs 6, refs 19.

A multi-scale atomistic-continuum modelling of crack propagation in a two-dimensional macroscopic plate

A novel multi-scale seamless model of brittle-crack propagation is proposed and applied to the simulation of fracture growth in a two-dimensional Ag plate with macroscopic dimensions. The model represents the crack propagation at the macroscopic scale as the drift-diffusion motion of the crack tip alone. The diffusive motion is associated with the crack-tip coordinates in the position space, and reflects the oscillations observed in the crack velocity following its critical value. The model couples the crack dynamics at the macroscales and nanoscales via an intermediate mesoscale continuum. The finite-element method is employed to make the transition from the macroscale to the nanoscale by computing the continuum-based displacements of the atoms at the boundary of an atomic lattice embedded within the plate and surrounding the tip. Molecular dynamics (MD) simulation then drives the crack tip forward, producing the tip critical velocity and its diffusion constant. These are then used in the Ito stochastic calculus to make the reverse transition from the nanoscale back to the macroscale. The MD-level modelling is based on the use of a many-body potential. The model successfully reproduces the crack-velocity oscillations, roughening transitions of the crack surfaces, as well as the macroscopic crack trajectory. The implications for a 3-D modelling are discussed.

Numerical modelling of solder joint formation

Solder materials are used to provide a connection between electronic components and printed circuit boards (PCBs) using either the reflow or wave soldering process. As a board assembly passes through a reflow furnace the solder (initially in the form of solder paste) melts, reflows, then solidifies, and finally deforms between the chip and board. A number of defects may occur during this process such as flux entrapment, void formation, and cracking of the joint, chip or board. These defects are a serious concern to industry, especially with trends towards increasing component miniaturisation and smaller pitch sizes. This paper presents a modelling methodology for predicting solder joint shape, solidification, and deformation (stress) during the assembly process.

Dynamics of an axisymmetric electromagnetic ‘crucible’ melting

Different industrial induction melting processes involve free surface and melt-solid interface of the liquid metal subject to dynamic change during the technological operation. Simulation of the liquid metal dynamics requires to solve the non-linear, coupled hydrodynamic-electromagnetic-heat transfer problem accounting for the time development of the liquid metal free boundary with a suitable turbulent viscosity model. The present paper describes a numerical solution method applicable for various axisymmetric induction melting processes, such as, crucible with free top surface, levitation, semi-levitation, cold crucible and similar melting techniques. The presented results in the cases of semi-levitation and crucible with free top surface meltings demonstrate oscillating transient behaviour of the free metal surface indicating the presence of gravity-inertial-electromagnetic waves which are coupled to the internal fluid flow generated by both the rotational and potential parts of the electromagnetic force.