Presentació: Elements per a la comprensió crítica de la reforma de l'ensenyament secundari

La reforma de l'ensenyament secundari ha estat i és encara un tema polémic, controvertit. En sentir crítiques referents a l'estat actual de l'ensenyament secundari per part de professionals procedents de sectors deis diferents estaments educatius, tant si aquestes crítiques són favorables a la reforma com si no ho són, és facil percebre un ambient general de preocupació. Davant d'aquest ambient, cal pensar que alguna cosa no deu acabar d'anar bé perqué s'hagi creat un clima de descontent tan generalitzat.

Nonlinear Pile Behavior in Integral Abutment Bridges, HR-227, Part 1, 1982

The highway departments of all fifty states were contacted to find the extent of application of integral abutment bridges, to survey the different guidelines used for analysis and design of integral abutment bridges, and to assess the performance of such bridges through the years. The variation in design assumptions and length limitations among the various states in their approach to the use of integral abutments is discussed. The problems associated with lateral displacements at the abutment, and the solutions developed by the different states for most of the ill effects of abutment movements are summarized in the report. An algorithm based on a state-of-the-art nonlinear finite element procedure was developed and used to study piling stresses and pile-soil interaction in integral abutment bridges. The finite element idealization consists of beam-column elements with geometric and material nonlinearities for the pile and nonlinear springs for the soil. An idealized soil model (modified Ramberg-Osgood model) was introduced in this investigation to obtain the tangent stiffness of the nonlinear spring elements. Several numerical examples are presented in order to establish the reliability of the finite element model and the computer software developed. Three problems with analytical solutions were first solved and compared with theoretical solutions. A 40 ft H pile (HP 10 X 42) in six typical Iowa soils was then analyzed by first applying a horizontal displacement (to simulate bridge motion) and no rotation at the top and then applying a vertical load V incrementally until failure occurred. Based on the numerical results, the failure mechanisms were generalized to be of two types: (a) lateral type failure and (b) vertical type failure. It appears that most piles in Iowa soils (sand, soft clay and stiff clay) failed when the applied vertical load reached the ultimate soil frictional resistance (vertical type failure). In very stiff clays, however, the lateral type failure occurs before vertical type failure because the soil is sufficiently stiff to force a plastic hinge to form in the pile as the specified lateral displacement is applied. Preliminary results from this investigation showed that the vertical load-carrying capacity of H piles is not significantly affected by lateral displacements of 2 inches in soft clay, stiff clay, loose sand, medium sand and dense sand. However, in very stiff clay (average blow count of 50 from standard penetration tests), it was found that the vertical load carrying capacity of the H pile is reduced by about 50 percent for 2 inches of lateral displacement and by about 20 percent for lateral displacement of 1 inch. On the basis of the preliminary results of this investigation, the 265-feet length limitation in Iowa for integral abutment concrete bridges appears to be very conservative.

Importance of polyethylene thickness in total shoulder arthroplasty: a finite element analysis.

BACKGROUND: Articular surfaces reconstruction is essential in total shoulder arthroplasty. Because of the limited glenoid bone support, thin glenoid component could improve anatomical reconstruction, but adverse mechanical effects might appear. METHODS: With a numerical musculoskeletal shoulder model, we analysed and compared three values of thickness of a typical all-polyethylene glenoid component: 2, 4 (reference) and 6mm. A loaded movement of abduction in the scapular plane was simulated. We evaluated the humeral head translation, the muscle moment arms, the joint force, the articular contact pattern, and the polyethylene and cement stress. Findings Decreasing polyethylene thickness from 6 to 2mm slightly increased humeral head translation and muscle moment arms. This induced a small decreased of the joint reaction force, but important increase of stress within the polyethylene and the cement mantel. Interpretation The reference thickness of 4mm seems a good compromise to avoid stress concentration and joint stuffing.

Nonlinear Finite Element Study of Piles in Integral Abutment Bridges, HR-227, Part 2, 1982

The highway departments of the states which use integral abutments in bridge design were contacted in order to study the extent of integral abutment use in skewed bridges and to survey the different guidelines used for analysis and design of integral abutments in skewed bridges. The variation in design assumptions and pile orientations among the various states in their approach to the use of integral abutments on skewed bridges is discussed. The problems associated with the treatment of the approach slab, backfill, and pile cap, and the reason for using different pile orientations are summarized in the report. An algorithm based on a state-of-the-art nonlinear finite element procedure previously developed by the authors was modified and used to study the influence of different factors on behavior of piles in integral abutment bridges. An idealized integral abutment was introduced by assuming that the pile is rigidly cast into the pile cap and that the approach slab offers no resistance to lateral thermal expansion. Passive soil and shear resistance of the cap are neglected in design. A 40-foot H pile (HP 10 X 42) in six typical Iowa soils was analyzed for fully restrained pile head and pinned pile head. According to numerical results, the maximum safe length for fully restrained pile head is one-half the maximum safe length for pinned pile head. If the pile head is partially restrained, the maximum safe length will lie between the two limits. The numerical results from an investigation of the effect of predrilled oversized holes indicate that if the length of the predrilled oversized hole is at least 4 feet below the ground, the vertical load-carrying capacity of the H pile is only reduced by 10 percent for 4 inches of lateral displacement in very stiff clay. With no predrilled oversized hole, the pile failed before the 4-inch lateral displacement was reached. Thus, the maximum safe lengths for integral abutment bridges may be increased by predrilling. Four different typical Iowa layered soils were selected and used in this investigation. In certain situations, compacted soil (> 50 blow count in standard penetration tests) is used as fill on top of natural soil. The numerical results showed that the critical conditions will depend on the length of the compacted soil. If the length of the compacted soil exceeds 4 feet, the failure mechanism for the pile is similar to one in a layer of very stiff clay. That is, the vertical load-carrying capacity of the H pile will be greatly reduced as the specified lateral displacement increases.

An operator formulation of the multiscale finite-volume method with correction function

The multiscale finite-volume (MSFV) method has been derived to efficiently solve large problems with spatially varying coefficients. The fine-scale problem is subdivided into local problems that can be solved separately and are coupled by a global problem. This algorithm, in consequence, shares some characteristics with two-level domain decomposition (DD) methods. However, the MSFV algorithm is different in that it incorporates a flux reconstruction step, which delivers a fine-scale mass conservative flux field without the need for iterating. This is achieved by the use of two overlapping coarse grids. The recently introduced correction function allows for a consistent handling of source terms, which makes the MSFV method a flexible algorithm that is applicable to a wide spectrum of problems. It is demonstrated that the MSFV operator, used to compute an approximate pressure solution, can be equivalently constructed by writing the Schur complement with a tangential approximation of a single-cell overlapping grid and incorporation of appropriate coarse-scale mass-balance equations.

Atmospheric deposition and migration of artificial radionuclides in Alpine soils (Val Piora, Switzerland) compared to the distribution of selected major and trace elements.

Artificial radionuclides ((137)Cs, (90)Sr, Pu, and (241)Am) are present in soils because of Nuclear Weapon Tests and accidents in nuclear facilities. Their distribution in soil depth varies according to soil characteristics, their own chemical properties, and their deposition history. For this project, we studied the atmospheric deposition of (137)Cs, (90)Sr, Pu, (241)Am, (210)Pb, and stable Pb. We compared the distribution of these elements in soil profiles from different soil types from an alpine Valley (Val Piora, Switzerland) with the distribution of selected major and trace elements in the same soils. Our goals were to explain the distribution of the radioisotopes as a function of soil parameters and to identify stable elements with analogous behaviors. We found that Pu and (241)Am are relatively immobile and accumulate in the topsoil. In all soils, (90)Sr is more mobile and shows some accumulations at depth into Fe-Al rich horizons. This behavior is also observed for Cu and Zn, indicating that these elements may be used as chemical analogues for the migration of (90)Sr into the soil.

Interpolating and sampling sequences in finite Riemann surfaces

We provide a description of the interpolating and sampling sequences on a space of holomorphic functions on a finite Riemann surface, where a uniform growth restriction is imposed on the holomorphic functions.

Elements ressaltats per infants i mestres en la creació d'un conte integrant les TIC i intercanvi d'aquest entre dues escoles a través d'una videoconferència

Les noves tecnologies de la Informació i la Comunicació esdevenen el tema principal d’aquesta investigació. L’objectiu primordial del treball és donar resposta al següent interrogant: què destaquen els infants i mestres d’una experiència d’aula en la qual s’integren les TIC? Aquesta recerca s’aproxima a la Grounded Theory, que es centra en crear la teoria a partir de l’anàlisi de les dades. En aquest treball és a partir de les dades analitzades que es defineixen les dimensions i indicadors per tal de donar resposta a la pregunta formulada inicialment. La intervenció que s’ha realitzat ha estat portada a terme amb les classes de P-4 i P-5 de dues escoles. Consisteix en explicar el mateix conte, sense final, a les dues aules i que aquestes s’inventin un final per tal d’explicar-se’l a través d’una videoconferència. Els resultats obtinguts amb els instruments de recollida de dades utilitzats en la investigació (dibuix infantil, grups de discussió i entrevistes) mostren que infants i mestres no destaquen el mateix d’una intervenció d’aula utilitzant les TIC. Els infants es centren més en el contingut, mentre que les mestres destaquen la metodologia i la tecnologia emprada.

The number of planar central configurations for the 4-body problem is finite when 3 mass positions are fixed

In the n{body problem a central con guration is formed when the position vector of each particle with respect to the center of mass is a common scalar multiple of its acceleration vector. Lindstrom showed for n = 3 and for n > 4 that if n ? 1 masses are located at xed points in the plane, then there are only a nite number of ways to position the remaining nth mass in such a way that they de ne a central con guration. Lindstrom leaves open the case n = 4. In this paper we prove the case n = 4 using as variables the mutual distances between the particles.

Estudi de l'efecte estabilitzador de les corretges en les cobertes lleugeres

L’acer és un dels materials més destacats dins l’àmbit estructural degut, en gran part, a laseva elevada capacitat tensional, tant en tracció com en compressió. Aquesta capacitatpermet estructures lleugeres i cobrir grans llums. En pòrtics de nusos rígids d’una nauindustrial és habitual l’ús de perfils oberts en doble T. Aquests perfils presenten una baixarigidesa a torsió i flexió lateral, el qual els fa propensos a patir inestabilitat quan es produeixcompressió en una de les seves ales en flexió, fenòmen que es coneix com a vinclamentlateral. Per aquest motiu, el càlcul en efectes de 2n ordre adquireix una importància mésrellevant a l’hora de dimensionar els elements estructurals. Un altre punt important és queels elements estructurals estan units entre ells, no treballen de manera individual, fet quecomporta un estudi més complex a l’hora de determinar les condicions de contorn de cadaelement.El present estudi pretén determinar l'efecte estabilitzador de les corretges en un pòrtic denusos rígids, i si és així, en quina magnitud pot arribar a afectar aquest grau de travat alconjunt estructural.L'Estudi s'ha realitzat seguint dues metodologies diferents. Els anàlisis estructurals parteixendels criteris indicats a les normatives d'estructures metàl•liques espanyola (CTE-DB-SE-A) il'europea (Eurocodig 3)

Design of Piles for Integral Abutment Bridges, HR-252, 1984

More and more, integral abutment bridges are being used in place of the more traditional bridge designs with expansion releases. In this study, states which use integral abutment bridges were surveyed to determine their current practice in the design of these structures. To study piles in integral abutment bridges, a finite element program for the soil-pile system was developed (1) with materially and geometrically nonlinear, two and three dimensional beam elements and (2) with a nonlinear, Winkler soil model with vertical, horizontal, and pile tip springs. The model was verified by comparison to several analytical and experimental examples. A simplified design model for analyzing piles in integral abutment bridges is also presented. This model grew from previous analytical models and observations of pile behavior. The design model correctly describes the essential behavioral characteristics of the pile and conservatively predicts the vertical load-carrying capacity. Analytical examples are presented to illustrate the effects of lateral displacements on the ultimate load capacity of a pile. These examples include friction and end-bearing piles; steel, concrete, and timber piles; and bending about the weak, strong, and 45° axes for H piles. The effects of cyclic loading are shown for skewed and nonskewed bridges. The results show that the capacity of friction piles is not significantly affected by lateral displacements, but the capacity of end-bearing piles is reduced. Further results show that the longitudinal expansion of the bridge can introduce a vertical preload on the pile.

Primers resultats dels estudis dels elements marmoris del jaciment de l'antiguitat tardana del Pla de Ses Figueres de l'illa de Cabrera

El Pla de ses Figueres és un jaciment que es troba a la riba del port de Cabrera, una petita illa de 1.836 ha. situada en el sud de les illes Balears. Diversos treballs de prospecció i d’excavació han donat a conèixer una important ocupació humana del lloc centrada en els segles V a VII dC. A les zones intervingudes s’han identificat una factoria de salaons, un possible taller de producció de porpra i una necròpoli. En el present treball s’exposaran set peces de marbre localitzades en dit jaciment dintre del projecte “Recuperació, consolidació i museïtzació del monestir bizantí de l’illa de Cabrera”, el qual ja fa dotze anys que finança ininterrompudament l’Ajuntament de Palma.