Search results for "math"
showing 10 items of 25151 documents
Does using a visual-representation tool foster students’ ability to identify forces and construct free-body diagrams?
2013
Earlier research has shown that after physics instruction, many students have difficulties with the force concept, and with constructing free-body diagrams (FBDs). It has been suggested that treating forces as interactions could help students to identify forces as well as to construct the correct FBDs. While there is evidence that identifying interactions helps students in quantitative problem solving, there is no previous research investigating the effect of a visual-representation tool—an interaction diagram (ID)—on students’ ability to identify forces, and to construct the correct FBDs.We present an empirical study conducted in 11 Finnish high schools on students (n ¼ 335, aged 16) takin…
Lidar detection of carbon dioxide in volcanic plumes
2015
Volcanic gases give information on magmatic processes. In particular, anomalous releases of carbon dioxide precede volcanic eruptions. Up to now, this gas has been measured in volcanic plumes with conventional measurements that imply the severe risks of local sampling and can last many hours. For these reasons and for the great advantages of laser sensing, the thorough development of volcanic lidar has been undertaken at the Diagnostics and Metrology Laboratory (UTAPRAD-DIM) of the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA). In fact, lidar profiling allows one to scan remotely volcanic plumes in a fast and continuous way, and with high s…
Experimental Validation of Maximum Constant Boost Control and Switching Frequency Optimal for three-phase Quasi-Z-Source Converters
2020
This paper presents a modified modulation scheme for quasi-Z-Source converters, based on the Maximum Constant Boost Control (MCBC) concept and Switching Frequency Optimal (SFO) as reference signal. The effectiveness of the proposed technique is validated by comparing the obtained results (in terms of AC harmonic content and voltage stress) with those carried out from traditional modulation schemes. For this reason, a test bench has been assembled and the benefits of the SFO MCBC modulation scheme have been valuated.
Decoupled control scheme of grid-connected split-source inverters
2017
Grid-connected power conversion systems for renewable energy sources must fulfill several requirements, e.g., the high efficiency, the reduced cost and complexity, and, quite often, the boost capabilities that is usually achieved using a front-end dc–dc boost converter before the inversion stage, leading to a two-stage architecture. Meanwhile, single-stage power conversion systems, which perform the boosting operation within the inversion one, offer some potential advantages, in terms of reducing the complexity and the volume of the whole system. Among several proposed options, the split-source inverter (SSI) has been recently proposed by Abdelhakim et al. as an alternative option with some…
Relationship between volume and energy of vector fields
2001
Abstract A unified study of energy and volume functionals is presented here by determining the critical points of a functional that extends simultaneously energy and volume and that is defined on the product of the manifold of smooth maps C∞(M,N) times the manifold M of riemannian metrics on M. The restriction of this functional to different submanifolds of the space of vector fields X (M)× M is also considered, and used to study several functionals generalizing volume and energy or total bending of vector fields
R. Ghezzi - Volume measures in non equiregular sub-Riemannian manifolds
2017
In this talk we study the Hausdorff volume in a non equiregular sub-Riemannian manifold and we compare it to a smooth volume. First we give the Lebesgue decomposition of the Hausdorff volume. Then we focus on the regular part, show that it is not commensurable with a smooth volume and give conditions under which it is a Radon measure. Finally we give a complete characterization of the singular part. This is a joint work with F. Jean (ENSTA).
Dynamics in Interaction in Bilingual Team Teaching: Examples from a Finnish Preschool Classroom
2018
The current study aims to explore team teaching as it is manifested in bilingual interactional patterns in a preschool classroom in Finland. The data was collected in a preschool classroom where a bilingual pedagogy in Finnish (majority language) and Swedish (minority language) was implemented with monolingual Finnishspeaking children. Video recordings were made while two teachers with different predefined language roles were team teaching a class of 20 children during two circle times. A two-level analytic model was developed: on the macro level activity types, participant roles (type of leadership) and language allocation (the teachers’ relative use of Finnish and Swedish) were identified…
Challenging Transmission Modes of Teaching in Science Classrooms : Enhancing Learner-Centredness through Dialogicity
2017
There is an ongoing reform towards more inquiry-based teaching in school curriculum policy in South Africa. Reform towards more inquiry-based approaches is already integrated in pre-service teacher education programmes. As inquiry-based approaches have been gaining momentum worldwide, there is an increasing concern that dialogic interaction in classroom communication is being neglected. This is especially within teacher-orchestrated classroom interactions that should foster greater learner centredness and thus authentic scientific inquiry. In learner-centred teaching approaches, student contributions should be explicitly taken into account as part of classroom interactions in science. Learn…
Associations Among Teacher–Child Interactions, Teacher Curriculum Emphases, and Reading Skills in Grade 1
2017
Research Findings: The purpose of the present study was to examine the extent to which the quality of teacher–child interactions and teachers’ self-reported curriculum emphases are related to children’s reading skill development during their 1st school year. To accomplish this, we assessed the reading skills of 1,029 Finnish children (M age = 85.77 months) twice during Grade 1, and the children’s teachers (n = 91) completed questionnaires concerning their literacy-related curriculum emphases. In addition, teacher–child interactions in terms of emotional support, classroom organization, and instructional support were observed in 29 classrooms. The results of multilevel modeling showed that a…
Waste heat recovery from a marine waste incinerator using a thermoelectric generator
2012
Published version of an article published in the journal: Journal of Electronic Materials. Also available from the publisher at: http://dx.doi.org/10.1007/s11664-012-2009-6 A marine waste incinerator has been evaluated for waste heat harvesting using thermoelectric generators (TEG). The application has been evaluated using mathematical modeling to optimize the heat exchanger and some vital design parameters of the TEG. The calculation shows that it is possible to extract 58 kW el at a price of 6.6 US$/W from an 850-kW th incinerator when optimizing for maximum power. However, minimizing the cost, it is possible to get 25 kW el at a price of 2.5 US$/W. A trade-off between the two targets lea…