Experiencias de metrología escolar (VI).

Se presentan algunos ejercicios prácticos relacionados con el teorema de Pitágoras. Se emplean sencillos instrumentos de medida y por medio de una metodología activa, que integra la actividad manual con la intelectual, los alumnos comprueban las propiedades del teorema.

Distribución de tiempo y de trabajo de una jornada escolar.

La jornada escolar tiene un horario de nueve a doce horas por la mañana y de quince a diecisiete horas por la tarde. Por la mañana, tras la izada de la bandera y la oración, se dedican veinticinco minutos al cálculo mental y una hora al lenguaje y la lectura expresiva con ejercicios de ortografía, redacción, gramática y literatura. Tras el recreo, otra hora dedicada a la geometría, con la explicación del teorema de Pitágoras y sus aplicaciones prácticas. Por la tarde, un tiempo para completar trabajos o ejercicios pendientes y la última hora dividida en dos tiempos iguales para las clases de historia y dibujo. También, se redactan unas notas sobre las características de la escuela y de los alumnos que han servido de muestra para este trabajo.

Trabajos manuales.

Se describen algunas formas de aplicar los trabajos manuales a la enseñanza de las matemáticas. La cartulina y las tijeras tienen valor didáctico para que los niños aprendan las fracciones, las medidas de longitud y de superficie, el valor de los ángulos de un triángulo y el teorema de Pitágoras. Se dan indicaciones para la confección de poliedros regulares y otros sólidos geométricos, de mosaicos con motivos geométricos y de señales de circulación.

El estudio del triángulo como elemento para la adquisición de los conceptos geométricos básicos en el nuevo diseño curricular de Educación Primaria y primer ciclo de ESO.

Esta innovación obtuvo Mención honorífica en los Premios Nacionales de Investigación e Innovación Educativas 1994

Hacia un proyecto curricular de geometría para el ciclo 12-16 : su determinación en base a la utilización de geoplanos.

Elaborar una programación de matemáticas fundamentada en una determinada concepción 'constructivista' del aprendizaje, en la que se aborda el estudio del Teorema de Pitágoras (para séptimo y octavo de EGB o primer ciclo de la ESO). Explicitar y fundamentar exhaustivamente los principios de procedimiento asumidos para la elección, secuenciación y evaluación de las actividades recogidas en la unidad didáctica. Ensayar la programación de manera experimental en diferentes cursos, recurriendo a los geoplanos cuadrados como material manipulativo. Reelaborarla tras la primera experimentación. Presentar la programación de la unidad didáctica, fundamentada epistemológica, psicológica, sociológica y pedagógicamente. Hipótesis: La utilización de material manipulativo, como los geoplanos cuadrados, posibilita la concreción de una metodología constructivista del aprendizaje de la geometría en el ciclo 12-16. Alumnos del área de matemáticas de educación secundaria obligatoria. Se enmarca dentro de la investigación en la acción. El trabajo se ha desarrollado en torno a un seminario de discusión y a la puesta en práctica de las actividades. Se centra más en la fundamentación teórica de la unidad didáctica propuesta que en su aplicación. Seminario de discusión, actividades manipulativas con geoplanos. 1. El conjunto de actividades propuestas en torno al tema 'Teorema de Pitágoras' satisface los principios psico-pedagógicos de intervención que se deducen de una concepción constructivista del proceso de aprendizaje de los conocimientos científicos y que se explicitan como los más adecuados en las propuestas actuales de la Administración educativa, en concreto en el DCB. Asimismo, satisfacen los criterios recogidos en las orientaciones para la enseñanza y evaluación de dicho documento referidos al área de matemáticas en la ESO. 2. Se incluyen actividades previas con geoplanos para la ed. primaria y una explicación del material y de la concepción educativa de su creador, Caleb Gattegno. 3. A pesar de no haber desarrollado de forma sistemática la observación de la puesta en práctica de las actividades, se constata el alto grado de satisfacción y aprovechamiento que han mostrado todos los alumnos.

Memoria y adquisici??n del pensamiento matem??tico : las proposiciones como conjunto de secuencias condicionales

Resumen tomado de la publicaci??n

Mercadores de Letras : Rumos e Estratégias dos Editores e Livreiros no Estado Novo

Os "mercadores de letras" que agora publicamos corresponde ao texto da nossa dissertação de mestrado em História Contemporânea, defendida na faculdade de Letras de Universidade de Lisboa, em 1998. Por diversas razões e apesar de algumas propostas, sempre com a intenção de aligeirar o texto, não o publicamos na altura. Os projetos entretanto encetados e os novos rumos tomados pela nossa atividade de investigação, nomeadamente a opção pelo doutoramento em museologia, desviaram-nos decisivamente da nossa investigação sobre os editores e livreiros, sobre a divulgação do livro e da leitura. Foram anos de muita atividade. Em colaboração com o nosso amigo Ricardo Machaqueiro, desenvolvemos vários trabalhos sobre editoras e sobre os editores, nomeadamente sobre a Civilização do Porto, a Prelo a Teorema. Fizemos alguns trabalhos sobre Bibliotecas de Lisboa: A saudosa Biblioteca Popular, a biblioteca dos Operários da Sociedade Geral, A biblioteca do Arsenal do Alfeite, onde buscamos os vestígios da atividade de Bento Gonçalves, a Biblioteca da Voz do Operário. Trabalhamos várias livrarias, como a livraria leitura do Porto e a Livraria Ler, a livraria do Luís Alves, tertúlia do lisboeta bairro de Campo de Ourique, ao pé da estátua da Maria da Fonte. Alguns destes textos foram dados ao prelo em periódicos. A ver vamos se alguns serão reeditados.

Mercadores de Letras

Os ―mercadores de letras” que agora publicamos corresponde ao texto da nossa dissertação de mestrado em História Contemporânea, defendida na faculdade de Letras de Universidade de Lisboa, em 1998. Por diversas razões e apesar de algumas propostas, sempre com a intenção de aligeirar o texto, não o publicamos na altura. Os projetos entretanto encetados e os novos rumos tomados pela nossa atividade de investigação, nomeadamente a opção pelo doutoramento em museologia, desviaram-nos decisivamente da nossa investigação sobre os editores e livreiros, sobre a divulgação do livro e da leitura. Foram anos de muita atividade. Em colaboração com o nosso amigo Ricardo Machaqueiro, desenvolvemos vários trabalhos sobre editoras e sobre os editores, nomeadamente sobre a Civilização do Porto, a Prelo a Teorema. Fizemos alguns trabalhos sobre Bibliotecas de Lisboa: A saudosa Biblioteca Popular, a biblioteca dos Operários da Sociedade Geral, A biblioteca do Arsenal do Alfeite, onde buscamos os vestígios da atividade de Bento Gonçalves, a Biblioteca da Voz do Operário. Trabalhamos várias livrarias, como a livraria leitura do Porto e a Livraria Ler, a livraria do Luís Alves, tertúlia do lisboeta bairro de Campo de Ourique, ao pé da estátua da Maria da Fonte. Alguns destes textos foram dados ao prelo em periódicos. A ver vamos se alguns serão reeditados

Radiative forcing since preindustrial times due to ozone change in the troposphere and the lower stratosphere

Changes in atmospheric ozone have occurred since the preindustrial era as a result of increasing anthropogenic emissions. Within ACCENT, a European Network of Excellence, ozone changes between 1850 and 2000 are assessed for the troposphere and the lower stratosphere ( up to 30 km) by a variety of seven chemistry-climate models and three chemical transport models. The modeled ozone changes are taken as input for detailed calculations of radiative forcing. When only changes in chemistry are considered ( constant climate) the modeled global-mean tropospheric ozone column increase since preindustrial times ranges from 7.9 DU to 13.8 DU among the ten participating models, while the stratospheric column reduction lies between 14.1 DU and 28.6 DU in the models considering stratospheric chemistry. The resulting radiative forcing is strongly dependent on the location and altitude of the modeled ozone change and varies between 0.25 Wm(-2) and 0.45 Wm(-2) due to ozone change in the troposphere and - 0.123 Wm(-2) and + 0.066 Wm(-2) due to the stratospheric ozone change. Changes in ozone and other greenhouse gases since preindustrial times have altered climate. Six out of the ten participating models have performed an additional calculation taking into account both chemical and climate change. In most models the isolated effect of climate change is an enhancement of the tropospheric ozone column increase, while the stratospheric reduction becomes slightly less severe. In the three climate-chemistry models with detailed tropospheric and stratospheric chemistry the inclusion of climate change increases the resulting radiative forcing due to tropospheric ozone change by up to 0.10 Wm(-2), while the radiative forcing due to stratospheric ozone change is reduced by up to 0.034 Wm(-2). Considering tropospheric and stratospheric change combined, the total ozone column change is negative while the resulting net radiative forcing is positive.

Direct radiative effect of aerosols emitted by transport from road, shipping and aviation

Aerosols and their precursors are emitted abundantly by transport activities. Transportation constitutes one of the fastest growing activities and its growth is predicted to increase significantly in the future. Previous studies have estimated the aerosol direct radiative forcing from one transport sub-sector, but only one study to our knowledge estimated the range of radiative forcing from the main aerosol components (sulphate, black carbon (BC) and organic carbon) for the whole transportation sector. In this study, we compare results from two different chemical transport models and three radiation codes under different hypothesis of mixing: internal and external mixing using emission inventories for the year 2000. The main results from this study consist of a positive direct radiative forcing for aerosols emitted by road traffic of +20±11 mW m−2 for an externally mixed aerosol, and of +32±13 mW m−2 when BC is internally mixed. These direct radiative forcings are much higher than the previously published estimate of +3±11 mW m−2. For transport activities from shipping, the net direct aerosol radiative forcing is negative. This forcing is dominated by the contribution of the sulphate. For both an external and an internal mixture, the radiative forcing from shipping is estimated at −26±4 mW m−2. These estimates are in very good agreement with the range of a previously published one (from −46 to −13 mW m−2) but with a much narrower range. By contrast, the direct aerosol forcing from aviation is estimated to be small, and in the range −0.9 to +0.3 mW m−2.

Variational calculations of rovibrational states: a precise high-energy potential surface for HCN [and discussion]

We report the results of variational calculations of the rovibrational energy levels of HCN for J = 0, 1 and 2, where we reproduce all the ca. 100 observed vibrational states for all observed isotopic species, with energies up to 18000 cm$^{-1}$, to about $\pm $1 cm$^{-1}$, and the corresponding rotational constants to about $\pm $0.001 cm$^{-1}$. We use a hamiltonian expressed in internal coordinates r$_{1}$, r$_{2}$ and $\theta $, using the exact expression for the kinetic energy operator T obtained by direct transformation from the cartesian representation. The potential energy V is expressed as a polynomial expansion in the Morse coordinates y$_{i}$ for the bond stretches and the interbond angle $\theta $. The basis functions are built as products of appropriately scaled Morse functions in the bond-stretches and Legendre or associated Legendre polynomials of cos $\theta $ in the angle bend, and we evaluate matrix elements by Gauss quadrature. The hamiltonian matripx is factorized using the full rovibrational symmetry, and the basis is contracted to an optimized form; the dimensions of the final hamiltonian matrix vary from 240 $\times $ 240 to 1000 $\times $ 1000.We believe that our calculation is converged to better than 1 cm$^{-1}$ at 18 000 cm$^{-1}$. Our potential surface is expressed in terms of 31 parameters, about half of which have been refined by least squares to optimize the fit to the experimental data. The advantages and disadvantages and the future potential of calculations of this type are discussed.

Radiative forcing due to changes in ozone and methane caused by the transport sector

The year 2000 radiative forcing (RF) due to changes in O3 and CH4 (and the CH4-induced stratospheric water vapour) as a result of emissions of short-lived gases (oxides of nitrogen (NOx), carbon monoxide and non-methane hydrocarbons) from three transport sectors (ROAD, maritime SHIPping and AIRcraft) are calculated using results from five global atmospheric chemistry models. Using results from these models plus other published data, we quantify the uncertainties. The RF due to short-term O3 changes (i.e. as an immediate response to the emissions without allowing for the long-term CH4 changes) is positive and highest for ROAD transport (31mWm-2) compared to SHIP (24 mWm-2) and AIR (17 mWm-2) sectors in four of the models. All five models calculate negative RF from the CH4 perturbations, with a larger impact from the SHIP sector than for ROAD and AIR. The net RF of O3 and CH4 combined (i.e. including the impact of CH4 on ozone and stratospheric water vapour) is positive for ROAD (+16(±13)(one standard deviation) mWm-2) and AIR (+6(±5) mWm-2) traffic sectors and is negative for SHIP (-18(±10) mWm-2) sector in all five models. Global Warming Potentials (GWP) and Global Temperature change Potentials (GTP) are presented for AIR NOx emissions; there is a wide spread in the results from the 5 chemistry models, and it is shown that differences in the methane response relative to the O3 response drive much of the spread.

A new cyano-bridged one-dimensional (GdFeIII)-Fe-III coordination polymer with o-phenanthroline as the blocking ligand: synthesis, structure, and magnetic properties

Synthesis, structural characterization, and magnetic properties of a new cyano-bridged one-dimensional iron (III)-gadolinium (III) compound, trans-[Gd(o-phen)(2)(H2O)(2)(mu-CN)(2)Fe(CN)(4)], - 2no-phen (o-phen = 1,10-phenanthroline), have been described. The compound crystallizes in the triclinic P (1) over bar space group with the following unit cell parameters: a = 10.538(14) angstrom, b = 12.004(14) angstrom, c = 20.61(2) angstrom, alpha = 92.41(1)degrees, beta = 92.76(1)degrees, gamma = 11 2.72(1)degrees, and Z = 2. In this complex, each gadolinium (III) is coordinated to two nitrile nitrogens of the CN groups coming from two different ferricyanides, the mutually trans cyanides of each of which links another different Gd-III to create -NC-Fe(CN)(4)-CN-Gd-NC- type 1-D chain structure. The one-dimensional chains are self-assembled in two-dimensions via weak C-H center dot center dot center dot N hydrogen bonds. Both the variable-temperature (2-300 K, 0.01 T and 0.8 T) and variable-field (0-50 000 Gauss, 2 K) magnetic measurements reveal the existence of very weak interaction in this molecule. The temperature dependence of the susceptibilities has been analyzed using a model for a chain of alternating classic (7/2) and quantum (1/2) spins. (c) 2005 Elsevier B.V. All rights reserved.

A fast identification algorithm for Box-Cox transformation based radial basis function neural network

In this letter, a Box-Cox transformation-based radial basis function (RBF) neural network is introduced using the RBF neural network to represent the transformed system output. Initially a fixed and moderate sized RBF model base is derived based on a rank revealing orthogonal matrix triangularization (QR decomposition). Then a new fast identification algorithm is introduced using Gauss-Newton algorithm to derive the required Box-Cox transformation, based on a maximum likelihood estimator. The main contribution of this letter is to explore the special structure of the proposed RBF neural network for computational efficiency by utilizing the inverse of matrix block decomposition lemma. Finally, the Box-Cox transformation-based RBF neural network, with good generalization and sparsity, is identified based on the derived optimal Box-Cox transformation and a D-optimality-based orthogonal forward regression algorithm. The proposed algorithm and its efficacy are demonstrated with an illustrative example in comparison with support vector machine regression.