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11.
An integrated learning object, a web-based inquiry environment “Young Scientist” for basic school level is introduced by applying the semiosphere conception for explaining learning processes. The study focused on the development of students’ (n = 30) awareness of the affordances of learning objects (LO) during the 3 inquiry tasks, and their ability of dynamically reconstructing meanings in the inquiry subtasks through exploiting these LO affordances in “Young Scientist”. The problem-solving data recorded by the inquiry system and the awareness questionnaire served as the data-collection methods.It was demonstrated that learners obtain complete awareness of the LO affordances in an integrated learning environment only after several problem-solving tasks. It was assumed that the perceived task-related properties and functions of LOs depend on students’ interrelations with LOs in specific learning contexts. Learners’ overall awareness of certain LO affordances, available in the inquiry system “Young Scientist”, developed with three kinds of patterns, describing the hierarchical development of the semiosphere model for learners. The better understanding of the LO affordances, characteristic to the formation of the functioning semiosphere, was significantly related to the advanced knowledge construction during these inquiry subtasks that presumed translation of information from one semiotic system to another. The implications of the research are discussed in the frames of the development of new contextual gateways for learning with virtual objects. It is assumed that effective LO-based learning has to be organized through pedagogically constrained gateways by manifesting certain LO affordances in the context in order to build up the dynamic semiosphere model for learners. 相似文献
12.
Y. L. Zhang) G. Spinks) ) Departmentof Mechanical Engineering Ngee Ann Polytechnic Clementi Road Singapore) Intelligent Polymer Research Institute University of Wollongong Northfields Ave Wollongong NSW Australia 《金属学报(英文版)》1999,12(4):421-426
1.IntroductionRecently,therehasbeenanupsurgeofinterestinthepreventionofcorrosionofsteelthroughtheuseofconductivepolymercoatings〔1〕.Unfortunately,poorcoatingadhesivedurability,whichhadoftenbeenencounteredduringcoatingemploied,limitedtheapplicationofco… 相似文献
13.
N. Alexeyeva A. Sarapuu K. Tammeveski F.J. Vidal-Iglesias J. Solla-Gullón J.M. Feliu 《Electrochimica acta》2011,(19):6702
The kinetics of O2 reduction on novel electrocatalyst materials deposited on carbon substrates were studied using the rotating disk electrode (RDE) technique. Palladium nanoparticles and Pd–M (PdCo and PdFe) nanoalloys supported on Vulcan XC-72R were prepared using two different synthetic routes. The catalyst samples were examined by transmission electron microscopy (TEM) and the average size of metal nanoparticles was determined. Electrochemical measurements were performed in 0.5 M H2SO4 and in 0.1 M NaOH solutions. The influence of different synthetic conditions on the values of specific activity and other kinetic parameters was investigated. These parameters were determined from the Tafel plots taking into account the real electroactive area for each electrode. Pd nanoparticles and Pd–M nanoalloys exhibit significantly high electrocatalytic activity for the four-electron reduction of oxygen to water. 相似文献
14.
Saari P.M. Kaarli R.K. Sarapuu R.V. Sonajalg H.R. 《Quantum Electronics, IEEE Journal of》1989,25(3):339-345
Polarization-preserving phase conjugation of an arbitrarily-polarized multiple-pulse optical signal by using a modified scheme of time-and-space-domain holography is predicted theoretically and demonstrated experimentally. The experimental results obtained by utilizing octaethylporphin-doped polystyrene at 1.8 K as a spectrally-selective recording material indicate that in full accordance with the theory, the reconstructed phase-conjugated replicas of the multiple-pulse optical signal appear temporally reversed and have conjugated wavefronts while the original temporal and spatial dependence of the polarization state is restored. Thus, complete phase conjugation of an optical signal is demonstrated 相似文献
15.
The electrochemical reduction of oxygen on thin Pd films with a nominal thickness of 0.25-10 nm on polycrystalline Au substrate (Pd/Au) was studied. The Pd films were prepared by electron beam evaporation and oxygen reduction was studied in 0.1 M HClO4 and 0.05 M H2SO4 solutions using the rotating disk electrode (RDE) method. The surface morphology of Pd overlayers was examined by scanning tunnelling microscopy (STM). O2 reduction predominantly proceeds through 4e− pathway on all Pd/Au electrodes. The specific activity (SA) of oxygen reduction was lower in H2SO4 solution and decreased slightly with decreasing the Pd film thickness. In HClO4, the SA was higher and not significantly dependent on the film thickness. The Tafel slope values close to −60 mV at low current densities and −120 mV at high current densities were found for all electrodes. 相似文献
16.
Schulze Spüntrup Frederik Ave Giancarlo Dalle Imsland Lars Harjunkoski Iiro 《Optimization and Engineering》2022,23(3):1255-1287
Optimization and Engineering - Large fleets of engineering assets that are subject to ongoing degradation are posing the challenge of how and when to perform maintenance. For a given case study,... 相似文献