15,145 research outputs found

    Teacher education for effective technology integration

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    About a decade ago, several researchers used Shulman's (1986) framework about Pedagogical Content Knowledge (PCK) - a body of knowledge that constitutes a special amalgam of content, pedagogy, learners, and context - as a theoretical basis for developing TPCK or TPACK: a framework for guiding teachers' cognition about technology integration in teaching and learning (Angeli, Valanides, & Christodoulou, 2016). Different models of TPCK/TPACK are proposed in the literature, each with a different focus (on practice, instructional design, context, etc.) and with a different theoretical interpretation about the nature and development of the knowledge that teachers need to have to be able to teach with technology (e.g., Angeli & Valanides, 2005, 2009, 2013; Koehler & Mishra, 2008; Niess, 2005).In this direction, research is being carried out to identify TPCK design procedures for initial teacher education. In teaching, when transferring TPCK to design and methodological practices, there is a need to consider a number of factors, especially: the different modes of adopting technologies; the integration of tool affordances, content and pedagogy; the implementation of learning environments; the operationalization of knowledge; and detailed analysis of teaching models and approache

    Convergence in strongly monotone systems with an increasing first integral

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    Structural instability in an autophosphorylating kinase switch

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    We analyse a simple kinase model that exhibits bistability when there is no protein turnover, and show analytically that the property of being bistable is not necessarily conserved when degradation and synthesis of the kinase are taken into account

    Pressure drop and holdup predictions in horizontal oil-water flows for curved and wavy interfaces

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    In this work a modified two-fluid model was developed based on experimental observations of the interface configuration in stratified liquid-liquid flows. The experimental data were obtained in a horizontal 14. mmID acrylic pipe, for test oil and water superficial velocities ranging from 0.02. m/s to 0.51. m/s and from 0.05. m/s to 0.62. m/s, respectively. Using conductance probes, average interface heights were obtained at the pipe centre and close to the pipe wall, which revealed a concave interface shape in all cases studied. A correlation between the two heights was developed that was used in the two-fluid model. In addition, from the time series of the probe signal at the pipe centre, the average wave amplitude was calculated to be 0.0005. m and was used as an equivalent roughness in the interfacial shear stress model. Both the interface shape and roughness were considered in the two-fluid model together with literature interfacial shear stress correlations. Results showed that the inclusion of both the interface curvature and the equivalent roughness in the two-fluid model improved its predictions of pressure drop and interface height over the range of studied superficial oil and water velocities. Compared to the two-fluid model with other interfacial shear stress correlations, the modified model performed better particularly for predicting pressure drop

    Statistical Study of the Blue Straggler Properties in Galactic Globular Clusters

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    In this paper we report on the most significant results from a statistical analysis of the main properties of globular cluster blue straggler stars (BSS) extracted from the HST snapshot database of photometrically homogeneous CMDs (Piotto et al. 2002). The BSS relative frequency presents a significant anticorrelation with the collisional rate and with the cluster total absolute luminosity.Comment: 2 pages, 1 figure, A.S.P. Conf. Ser., in press in Vol. 296, 200

    Oscillations in I/O monotone systems under negative feedback

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    Oscillatory behavior is a key property of many biological systems. The Small-Gain Theorem (SGT) for input/output monotone systems provides a sufficient condition for global asymptotic stability of an equilibrium and hence its violation is a necessary condition for the existence of periodic solutions. One advantage of the use of the monotone SGT technique is its robustness with respect to all perturbations that preserve monotonicity and stability properties of a very low-dimensional (in many interesting examples, just one-dimensional) model reduction. This robustness makes the technique useful in the analysis of molecular biological models in which there is large uncertainty regarding the values of kinetic and other parameters. However, verifying the conditions needed in order to apply the SGT is not always easy. This paper provides an approach to the verification of the needed properties, and illustrates the approach through an application to a classical model of circadian oscillations, as a nontrivial ``case study,'' and also provides a theorem in the converse direction of predicting oscillations when the SGT conditions fail.Comment: Related work can be retrieved from second author's websit

    Multi-Stability in Monotone Input/Output Systems

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    This paper studies the emergence of multi-stability and hysteresis in those systems that arise, under positive feedback, starting from monotone systems with well-defined steady-state responses. Such feedback configurations appear routinely in several fields of application, and especially in biology. Characterizations of global stability behavior are stated in terms of easily checkable graphical conditions. An example of a signaling cascade under positive feedback is presented.Comment: See http://www.math.rutgers.edu/~sontag for related work; to appear in Systems and Control Letter
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