Nonlinear Control of pressurized water reactors with uncertainties estimation via high order sliding mode     

Mauro Cappelli  Bernardino Castillo–Toledo  Stefano Di Gennaro 《Journal of The Franklin Institute》2021,358(2):1308-1326

In this work, dynamic controllers are designed for reactor power, pressurizer water level, and pressure control in the primary circuit of a pressurized water reactor. These nonlinear controllers use super-twisting sliding-mode estimators to enhance their robustness versus parameter variations and external disturbances. Hence, the perturbative terms can be canceled by the control, thus improving the dynamic behavior of the controlled system. The designed controllers ensure good performances and better transient behavior, also in the presence of uncertainties and disturbances. A performance study of the proposed controllers is carried out in the presence also of unmodeled dynamics.  相似文献   

Edge superconductivity in multilayer WTe2 Josephson junction     

Ce Huang  Awadhesh Narayan  Enze Zhang  Xiaoyi Xie  Linfeng Ai  Shanshan Liu  Changjiang Yi  Youguo Shi  Stefano Sanvito  Faxian Xiu 《国家科学评论(英文版)》2020,7(9):1468

WTe₂, as a type-II Weyl semimetal, has 2D Fermi arcs on the (001) surface in the bulk and 1D helical edge states in its monolayer. These features have recently attracted wide attention in condensed matter physics. However, in the intermediate regime between the bulk and monolayer, the edge states have not been resolved owing to its closed band gap which makes the bulk states dominant. Here, we report the signatures of the edge superconductivity by superconducting quantum interference measurements in multilayer WTe₂ Josephson junctions and we directly map the localized supercurrent. In thick WTe₂ (, the supercurrent is uniformly distributed by bulk states with symmetric Josephson effect (). In thin WTe₂ (10 nm), however, the supercurrent becomes confined to the edge and its width reaches up to and exhibits non-symmetric behavior . The ability to tune the edge domination by changing thickness and the edge superconductivity establishes WTe₂ as a promising topological system with exotic quantum phases and a rich physics.  相似文献   

Unravelling the dynamics of knowledge creation in communities of practice though complexity theory lenses     

Stefano?BorzilloEmail author  Renata?Kaminska-Labbé 《知识管理研究与实践》2011,9(4):353-366

Drawing on a longitudinal case study of Alpha Chemicals, we use four complexity theory constructs – adaptive tension, enabling leadership, enhanced cooperation, and boundary spanning – to explain the continuous knowledge creation dynamics in Communities of practice (CoPs). Our findings show that the virtual cycle of knowledge creation results from CoPs oscillating between guided and self-directed modes. In a guided mode, adaptive tension and enabling leadership prevail, resulting in knowledge expansion. In a self-directed mode, enhancing cooperation and boundary spanning are the most significant, resulting in knowledge probing. This research uncovers the value of conceptualizing CoPs as complex adaptive systems with emergent and intentional processes coexisting to create a virtual knowledge creation cycle. Our findings complement the dominant theory on CoPs’ insights by moving beyond the control/autonomy debate and highlighting that knowledge creation dynamics results from a flexible combination and recombination of the different top-down and bottom-up forces.  相似文献   

A driver model of a two-man bobsleigh     

Francesco Braghin  Mauro Donzelli  Stefano Melzi  Edoardo Sabbioni 《Sports Engineering》2011,13(4):181-193

Up to now, the optimization of structural parameters affecting the performance of a bobsleigh has been carried out mainly on the basis of athletes’ feedback, thus leading to a series of small modifications without univocal guidelines. Even though on-track tests represent a basic step for the final tuning of the sled, experimentation does not seem to represent an appropriate tool to objectively determine the influence of such structural parameters on the overall performance. In fact, their effect can easily be masked by driving errors, changes in the ice surface conditions and temperature thus requiring repeated tests for achieving statistical evidence. For this reason, numerical analysis, carried out with a 3D model of the bobsled, turns out to be a privileged instrument to optimize bob design although limitations in the sled model (e.g. ice friction properties that still have to be fully understood) may affect the obtained results. However, such tool is able to provide useful indications only if a correct driver model is implemented. This work focuses on the development of a numerical model of a bobsleigh driver that aims at reproducing the driving behaviour of real-world cup drivers and is basically made up of two steps: the identification of the trajectory that allows minimizing run time and the determination of the driver’s inputs to exactly follow that trajectory. For comparison purposes, the simulated driver’s inputs are compared with recorded ones on Cesana Pariol Olympic track.  相似文献   

Teacher training by alternating classroom work and work analysis: from the perspective of a social conception of meaning and action     

Stefano Bertone  Sébastien Chaliès  Eric Flavier 《Teachers and Teaching》2013,19(6):653-667

This article explores teacher training by the alternation of classroom work and work analysis using an approach based on a social conception of meaning and action. The advantage of this approach is that it allows the development of professional activity in preservice teachers (PTs) to be assessed by tracking how the reflective tools acquired in training evolve in work and/or work analysis situations. The concepts of ‘meaning’ and ‘expectation’ are helpful in discussing the empirical data from a research program designed to evaluate the potential for PTs’ professional development offered by the alternating work/analysis programs of French University Institutes of Teacher Training. The main conclusions concern the need to organize PTs’ professional experiences within a training network so that PTs are not left on their own to face the diverse and complex situations of daily professional exercise. The effective procedures are those that allow PTs to construct concrete and circumstance‐based expectations that the professional rules they have learned are still operational. These expectations help PTs to efficiently calibrate and interpret the meaning of their work experience, while also allowing them to prepare to act differently.  相似文献   

Soccer,religion, authority: notes on the early evolution of association football in Italy     

Stefano Pivato 《国际体育史杂志》2013,30(3):426-428

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Walking Inside Out: Contemporary British Psychogeography     

Stefano Calzati 《Parallax》2016,22(3):380-383

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Comparing determinants of perceived and actual recycling skills: The role of motivational,behavioral and dispositional factors     

Paola Passafaro  Stefano Livi 《The Journal of environmental education》2017,48(5):347-356

An empirical investigation assessed the role of different factors of motivational, behavioral, and dispositional nature in the prediction of both perceived and actual skills concerning household waste recycling. A structured questionnaire (measuring attitudes, social norms, perceived control, need for cognitive closure, self-reported household recycling behavior and perceived recycling skills) and a simulation task (assessing actual recycling skills) were administered to 300 participants in Italy. Results indicate that, although positively related, perceived and actual skills are two distinct constructs differently related to motivational, behavioral, and dispositional factors. Implications for designing educational interventions to increase citizens' recycling skills are discussed.  相似文献   

The Dynamics of Interaction During Post‐lesson Conferences and the Development of Professional Activity: Study of a pre‐service physical education teacher and her co‐operating teacher     

Stefano Bertone  Sébastien Chaliès  Jacques Méard 《Asia-Pacific Journal of Teacher Education》2006,34(2):245-264

The purpose of this study was to characterise the development of a preservice physical education teacher's professional activity over the course of training interactions with her co‐operating teacher. The student teacher's professional development was studied using a hermeneutic and inductive approach based on the analysis of data from observation and self‐confrontation interviews. The results showed that the preservice teacher's conceptions regarding her teaching developed despite communication difficulties with her co‐operating teacher and that she constructed new knowledge—at times without her co‐operating teacher's awareness—even when she disagreed with him. However, the student teacher's classroom activity did not always change as a result of this new knowledge. The self‐confrontation interviews revealed her construction of knowledge, as well as the reasons for disagreement and her resistance to changing her classroom action.  相似文献   

Development of a scale of Sense of Community in university online courses     

Giulia Balboni  Vittore Perrucci  Stefano Cacciamani  Bruno D. Zumbo 《Distance Education》2018,39(3):317-333

Creating a sense of community in online classes contributes to student retention and to their overall satisfaction with the course itself. This study aimed to develop a scale of sense of community of students attending online university courses. A series of ordinal exploratory factor analyses were conducted on data obtained from 839 students enrolled in Italian universities. Using an item analysis method, we were able to select the 36 most valid items from an original set of 60 items we had previously defined. These items are distributed across three related factors measuring membership, influence, and fulfillment of needs. This factorial structure replicates the McMillan and Chavis’s model of sense of community, upon the basis of which this scale was developed. The three factors presented good ordinal alpha and adequate convergent/divergent validity coefficients. The scale represents an efficient tool for the design, monitoring, and evaluation of online courses.  相似文献