La educación superior argentina en debate. Situación, problemas y perspectivas.

La educación superior argentina en debate. Situación, problemas y perspectivas

The Role Of Student Voice And Choice In Learner-Centered Competency Reform

Progressive reforms, pervasive throughout American education, are once again beginning to reshape the established traditional system to provide our students with an educational experience and learning opportunities that will better prepare them with twenty-first century skills. These reforms, rooted in constructivism and social learning, are characterized by an updated progressive vision of competency education that places students in the center of their education. Giving students authentic voice and choice has potential to engage these most important stakeholders in educational reform. This qualitative case study set in eleven upper elementary classrooms in one school, explores the opportunities for voice and choice as learners engage with educators to co-create a more personalized educational pathway through standards of competency. Insights gained from interviews with teachers, student focus groups, observations and artifacts describe how students experience voice and choice, and provide an understanding of how voice and choice contribute to reshaping the learning environment and the experience of the learner. The results of this study help educators understand how voice and choice support a collaborative classroom culture, increase engagement with learning standards, and further considers the perspective of young learners who gained insights about themselves as learners and who connected voice and choice with core values of respect, pride and freedom. Examining competency reform at one school provides practical insights into the structural supports, roles of the teacher and students, use of tools, and specific factors that sustain and challenge the transformation. Empowering students through voice and choice is a powerful way to engage with learners as stakeholders who may play an important role in developing and sustaining learner-centered competency reforms

Metal matrix composite: structure and technologies

I compositi a matrice metallica sono materiali aventi elevate potenzialità di applicazione, i cui punti critici riguardano soprattutto le tecnologie di produzione e le lavorazioni alle macchine utensili. Un composito a matrice di titanio rinforzato con lunghe fibre unidirezionali in SiC, il Ti6Al4V-SiCf, è candidato per componenti di turbine aeronautiche soggette a medie temperature (fino a 600°C) per lunghi tempi di esposizione. Per questo ne sono state esaminate sia le reazioni di tipo microchimico, le quali accadono soprattutto nell’interfaccia fibra/matrice, sia le proprietà meccaniche. La microstruttura allo stato tal quale e dopo lunghi trattamenti termici (fino a 100 ore e 600°C) è stata esaminata mediante diffrazione ai raggi X (XRD), spettrometria elettronica (SEM/EDS), spettroscopia di fotoemissione (XPS) e spettroscopia Auger (AES). Il comportamento meccanico, anche qui sia allo stato tal quale che dopo trattamenti termici, è stato studiato attraverso prove ad indentazione strumentata (FIMEC), di modulo dinamico, prove di trazione e di fatica. Inoltre sono state eseguite prove di frizione interna per verificare il caratteristico comportamento anelastico del materiale, durante condizioni di elevato stato vibrazionale e di alta temperatura. Lo studio, sviluppato sullo stesso composito prodotto però mediante due processi di fabbricazione differenti come Hot Isostatic Pressure and Roll Diffusion Bonding, ha confermato l’idoneità del materiale alle applicazioni considerate. Per quanto riguarda lo studio della lavorabilità, sono stati studiati, dal punto di vista dell’operazione di foratura, i materiali compositi a matrice di alluminio rinforzati a fibre corte o particolato, valutando le migliori condizioni di riduzione delle forze di taglio, soprattutto in funzione delle temperatura del pezzo da forare.Metal matrix composites are materials having high application potentiality, whose critical points regards especially production technology and machining. A titanium matrix composite reinforced by unidirectional SiC fibers, Ti6Al4V-SiCf , is candidate to components of aeronautical turbines subjected at middle temperatures (500-600°C) for long exposure time. It has been examined about the micro-chemical reactions, occurring especially on the fiber-matrix interface, and the mechanical properties. The microstructure, in as-fabricated condition and after long-term heat treatments simulating the work condition has been investigated by means of high-temperature X-ray diffraction (XRD), energy dispersion spectrometry (SEM/EDS), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The mechanical behaviour, in as-fabricated condition and after heat treatments, have been inspected by instrumented indentation (FIMEC), dynamic modulus, tensile and fatigue tests. Moreover, to the verify the characteristic anelastic phenomena for the composite, internal friction probes have been carried out by using a vibrating reed technique with electrostatic excitation and frequency modulation detection of flexural vibration. The study has been developed on the same composite produced by two different fabrication process, Hot Isostatic Pressure and Roll Diffusion Bonding, confirming the suitable of the material for the considered applications. About the composite machining, aluminium matrix composite reinforced by short fiber or particle has been studied about drilling operations, evaluating the better condition to reduce the cutting forces (thrust and torque), especially as function of the workpiece temperature (hot drilling

Time-dependent geomagnetic cutoff estimation along the ISS orbit

In this contribution we present the calculation of a realistic timedependent geomagnetic cutoff along the International Space Station orbit, at about 400km above the Earth’s surface. For this work the Tsyganenko05 and IGRF models have been employed, including the temporal variation of the external component of the geomagnetic field due to the solar activity. The technique and its results will be discussed, as well as the relevance of this study to distinguish galactic cosmic rays from trapped secondary components in the geomagnetic field

Lind, P., Small Business Management in Cross-Cultural Environments

Lind, P., Small Business Management in Cross-Cultural Environment

Fairness Properties of Constrained Market Equilibria

This paper studies the notion of fairness in pure exchange economies involving uncertainty and asymmetric information. We propose a new concept of coalitional fair allocation in order to solve the tension that may exist between efficiency and envy-freeness when the equity of allocations is evaluated at the {\it interim} stage. Some characterizations of constrained market equilibria are derived extending the analysis to economies that have both an atomic and an atomless sector.Mixed markets, coalitional fairness, envy, efficiency, asymmetric information

Progetto e Valutazione della sostenibilita energetica e ambientale di alloggi sociali nel Comune di Pontedera (PI)

Il presente lavoro ha come oggetto il progetto di alloggi sociali nel Comune di Pontedera (PI) e la relativa valutazione della sostenibilità secondo le "Linee Guida per l'edilizia sostenibile in Toscana". L'area di intervento ricade nel vigente Piano per l'Edilizia Economica e Popolare del Comune di Pontedera, che ha costituito il punto di partenza per la progettazione degli edifici. Infine sono stati analizzati gli aspetti energetici e ambientali, pervenendo ad una valutazione complessiva della sostenibilità del sistema edilizio progettato

Modalidad de educación semipresencial. Relato de una experiencia.

En una sociedad orientada cada vez más hacia la gestión del conocimiento como fuente principal de producción y riqueza, se requiere una renovación constante de la enseñanza y una mayor rapidez y fluidez de los procesos educativos, para responder a las exigencias del mundo del trabajo. La educación en todas sus etapas y en todas sus modalidades constituye un elemento fundamental de cohesión respetando la diversidad de las personas y grupos sociales, en la medida que articule una nueva y completa oferta educativa que permita la formación de las personas, de acuerdo con sus posibilidades, medios y necesidades individuales. La educación a distancia, por sus características y por la potencialidad que ofrecen las tecnologías de información y comunicación que ahora tiene a su alcance, se convierte en una alternativa importante para lograr que la educación superior llegue a todos los sectores de la sociedad. El objetivo de esta ponencia será analizar los alcances y limitaciones de la incorporación de la modalidad de enseñanza semipresencial en un programa educativo implementado por la Universidad Provincial del Sudoeste en la región de influencia de Bahía Blanca

Fabric-Reinforced Cementitious Matrix (FRCM) Carbon Yarns with Different Surface Treatments Embedded in a Cementitious Mortar: Mechanical and Durability Studies

Nowadays, FRCM systems are increasingly used for the strengthening and retrofitting of existing masonry and reinforced concrete structures. Their effectiveness strongly depends on the bond that develops at the interface between multifilament yarns, which constitute the reinforcing fabric, and the inorganic matrix. It is well known that fabric yarns, especially when constituted by dry carbon fibers, have poor chemical-physical compatibility with inorganic matrices. For this reason, many efforts are being concentrated on trying to improve the interface compatibility by using different surface treatments on multifilament yarns. In this paper, three different surface treatments have been considered. The first two involve yarn pre-impregnation with flexible epoxy resin or nano-silica coating, while the third one involves a fiber oxidation process. Uniaxial tensile tests were carried out on single carbon yarns to evaluate tensile strength, elastic modulus and ultimate strain before and after surface treatments, and also after yarn exposure to accelerated artificial aging conditions (1000 h in saline or alkaline solutions at 40◦C), to evaluate their long-term behavior in aggressive environments. Pull-out tests on single carbon yarns embedded in a cementitious mortar were also carried out, under normal environmental conditions and after artificial exposure. Epoxy proved to be the most effective treatment, by increasing the yarn tensile strength of 34% and the pull-out load of 138%, followed by nano-silica (+9%; +40%). All surface treatments were shown to remain effective even after artificial environmental exposures, with a maximum reduction of yarn tensile strength of about 13%

The contribution of weathering of the main Alpine rivers on the global carbon cycle

On geological time-scales the carbon fluxes from the solid Earth to the atmosphere mainly result from volcanism and metamorphic-decarbonation processes, whereas the carbon fluxes from atmosphere to solid Earth mainly depend on weathering of silicates and carbonates, biogenic precipitation and removal of CaCO3 in the oceans and volcanic gases – seawater interactions. Quantifying each contribution is critical. In this work, we estimate the atmospheric CO2 uptake by weathering in the Alps, using results of the study of the dissolved loads transported by 33 main Alpine rivers. The chemical composition of river water in unpolluted areas is a good indicator of surface weathering processes (Garrels and Mackenzie, 1971; Drever, 1982; Meybeck, 1984; Tardy, 1986; Berner and Berner, 1987; Probst et al., 1994). The dissolved load of streams originates from atmospheric input, pollution, evaporite dissolution, and weathering of carbonate and silicate rocks, and the application of mass balance calculations allows quantification of the different contributions. In this work, we applied the MEGA (Major Element Geochemical Approach) geochemical code (Amiotte Suchet, 1995; Amiotte Suchet and Probst, 1996) to the chemical compositions of the selected rivers in order to quantify the atmospheric CO2 consumed by weathering in Alpine region. The drainage basins of the main Alpine rivers were sampled near the basin outlets during dry and flood seasons. The application of the MEGA geochemical consisted in several steps. First, we subtracted the rain contribution in river waters knowing the X/Cl (X = Na, K, Mg, Ca) ratios of the rain. Next, we considered that all (Na+K) came from silicate weathering. The average molar ratio Rsil = (Na+K)/(Ca+Mg) for rivers draining silicate terrains was estimated from unpolluted French stream waters draining small monolithological basins (Meybeck, 1986; 1987). For the purpose, we prepared a simplified geo-lithological map of Alps according to the lithological classification of Meybeck (1986, 1987). Then for each basin we computed Rsil weighted average considering the surface and the mean precipitation for the surface area of each lithology. Lastly, we estimated the (Ca+Mg) originating from carbonate weathering as the remaining cations after silicate correction. Depending on time-scales of the phenomena (shorter than about 1 million year i.e. correlated to the short term carbon cycle, or longer than about 1 million years i.e. correlated to the long-term carbon cycle), we considered different equations for the quantification of the atmospheric CO2 consumed by weathering (Huh, 2010). The results show the net predominance of carbonate weathering on fixing atmospheric CO2 and that, considering the long-term carbon cycle, the amount of atmospheric CO2 uptake by weathering is about one order of magnitude lower than considering the short-term carbon cycle. Moreover, considering the short-term carbon cycle, the mean CO2 consumed by Alpine basins is of the same order of magnitude of the mean CO2 consumed by weathering by the 60 largest rivers of the world estimated by Gaillardet et al. (1999)