La qualité lexicale de textes produits à la fin du primaire et l’influence du contexte socioéconomique

Cet article présente les résultats d’une étude visant à comparer des textes d’élèves de 6e année du primaire provenant de milieux socioéconomiques contrastés. L’analyse des productions écrites a porté sur le choix lexical et les décisions concernant l’orthographe d’usage. Au total, 105 élèves (63 de milieux défavorisés et 42 de milieux favorisés) ont été soumis à une épreuve de production écrite d’une durée de cinq minutes, à partir d’une histoire séquentielle imagée. Les résultats révèlent des différences entre les milieux socioéconomiques à l’égard du pourcentage d’erreurs d’orthographe d’usage dans le texte, mais pas sur le plan de la diversité lexicale

Analytical investigation of the heat-transfer limits of a novel solar loop-heat pipe employing a mini-channel evaporator

© 2018 by the authors. This paper presents an analytical investigation of heat-transfer limits of a novel solar loop-heat pipe developed for space heating and domestic hot water use. In the loop-heat pipe, the condensate liquid returns to the evaporator via small specially designed holes, using a mini-channel evaporator. The study considered the commonly known heat-transfer limits of loop-heat pipes, namely, the viscous, sonic, entrainment, boiling and heat-transfer limits due to the two-phase pressure drop in the loop. The analysis considered the main factors that affect the limits in the mini-channel evaporator: the operating temperature, mini-channel aspect ratio, evaporator length, evaporator inclination angle, evaporator-to-condenser height difference and the dimension of the holes. It was found that the entrainment is the main governing limit of the system operation. With the specified loop design and operational conditions, the solar loop-heat pipe can achieve a heat-transport capacity of 725 W. The analytical model presented in this study can be used to optimise the heat-transfer capacity of the novel solar loop-heat pipe

A review of solar photovoltaic-thermoelectric hybrid system for electricity generation

Solar energy application in a wider spectrum has the potential for high efficiency energy conversion. However, solar cells can only absorb photon energy of the solar spectrum near the solar cell band-gap energy, and the remaining energy will be converted into thermal energy. The thermoelectric generator is a good choice to utilize this thermal energy. This paper analyses the feasibility of photovoltaic-thermoelectric (PV-TE), and reviews the current types and performance of PV-TE. Furthermore, it presents the optimization and development of PV-TE. In addition, this paper presents the challenge and efficient improvement of PV-TE in actual application. Therefore, this paper would provide a valuable reference for further research into the field of PV-TE and its applications

Energy performance analysis of a novel solar PVT loop heat pipe employing a microchannel heat pipe evaporator and a PCM triple heat exchanger

This study presents a numerical analysis of the energy efficiency for a novel solar PVT Loop Heat Pipe (PVT-LHP) employing a novel Micro-channel evaporator and a novel PCM heat storage exchanger. It presents a description of the different sub-models in the PVT-LHP system (the PVT model, the microchannel heat collector model and the novel PCM triple heat exchanger model) and the integrated model of the system. The integrated model of the system was solved by ensuring a heat balance at the condenser and the evaporator. A parametric analysis has been performed in order to assess the influence of the environmental parameters (i.e. solar radiation, air temperature, wind velocity), structural parameters (i.e. glazing cover, the number of absorbing microchannel heat pipes, PV cell packing factor), the circulating fluid variables (i.e. cold-water inlet temperature and water mass flow rate) on the energy performance of the system. The novel PVT-LHP has been compared with a onventional Solar PVT-LHP system. It was found that lower solar radiation, lower ambient air temperature, higher wind speed, higher packing factor, lower cold-water inlet temperature and a smaller cover number led to an enhanced electrical efficiency, but a reduced thermal efficiency of the module; whereas a higher coldwater mass flow rate and a greater number of microchannel heat pipes gave rise to both thermal and electrical efficiencies of the module. It was also found that an increase of solar radiation, ambienttemperature, cover number, microchannel heat pipe number and packing factor are favourable factors for the overall COP (Coefficient Of Performance) of the system, whereas an increase of wind velocity and cold water mass flow rate are unfavourable. The study indicated the existence of an optimal cover number, number of microchannel heat pipes and mass flowrate. Under the given design conditions, the electrical, thermal and overall efficiency of the PV/LHP module were 12.2%, 55.6% and 67.8% respectively and the novel system can achieve 28% higher overall energy efficiency and 2.2 times higher COP compared to a conventional system. The integrated computer model developed in this study can be used to design and optimize the novel PVT-LHP heating system

Simulation and experiment on thermal performance of a micro-channel heat pipe under different evaporator temperatures and tilt angles

© 2019 Elsevier Ltd For a solar collector with a heat pipe, the tilt angle is an important factor which has a direct impact on the orientation (surface azimuth angle) and affects the amount of solar radiation reaching the surface of the collector. The performance of the microchannel heat pipe (MCHP), as a highly efficient heat transfer device, can be influenced by gravity and two-phase flow pattern. The relationship between the performance of the MCHP and the tilt angles is nonlinear. In this paper, the effect of the evaporator temperature and tilt angle on the thermal performance of the MCHP, especially the temperature distribution along the heat pipe wall and the effective thermal conductivity, will be investigated. An experimental study with different evaporator temperatures and tilt angles is carried out. Additionally, thermal characteristics of the MCHP have been simulated and verified by the experimental results. In addition, the temperature distribution along the MCHP and the effective thermal conductivity for different working conditions have been performed. These results would provide many references for the solar collector with MCHP system design, optimization, and installation

Ontology-based database approach for handling preferences

Information systems now manage huge amount of data. Users are overwhelmed by the numerous results provided in response to their requests. These results must often be sorted and filtered in order to be usable. Moreover, the "one size fits all" approach has shown its limitation for information searching in many applications, particularly in the e-commerce domain. The capture and exploitation of user preferences have been proposed as a solution to overcome this problem. However, the existing approaches usually define preferences for a particular application. Thus, it is difficult to share and reuse the handled preferences in other contexts. In this chapter, we propose a sharable, formal and generic model to represent user's preferences. The model gathers several preferences models proposed in the Database and Semantic Web communities. The novelty of our approach is that the defined preferences are attached to the ontologies which describe the semantic of the data manipulated by the applications. Moreover, the proposed model offers a persistence mechanism and a dedicated language; it is implemented using Ontology-Based Databases (OBDB) system extended in order to take into account preferences. OBDB manage both ontologies and the data instances. The preference model is formally defined using the EXPRESS data modelling language which ensures us a free ambiguity definition and the approach is illustrated through a case study in the tourism domain. © 2010, IGI Global

Methodology for the in situ characterisation of soil vapor contaminants and their impact on the indoor air quality of buildings

International audienceThis study presents a fast and nonintrusive in situ methodology to characterise the Volatile Organic Compounds (VOCs) fluxes of contaminated sites and to quantify their intrusion into future buildings built on these sites. It could be used to conduct exhaustive ground pre-characterisation and indoor air assessments for future on-site buildings. The methodology involved the use of a specific apparatus called the "experimental box", representing convective and diffusive transfers of soil gas pollutants into buildings, to quantify an equivalent homogeneous concentration of the contaminant in the soil gas. Furthermore, this equivalent homogeneous concentration was used to quantify the indoor air pollutant concentration in a future building using an analytical transfer model associated with a numerical ventilation model. This methodology was applied on an experimental site. A critical analysis highlights its interest as a powerful complementary tool to constitute complementary support for decision-making methods and for human health risk assessment

An internet-supported school physical activity intervention in low socioeconomic status communities: results from the Activity and Motivation in Physical Education (AMPED) cluster randomised controlled trial

Objective Quality physical education (PE) is the cornerstone of comprehensive school physical activity (PA) promotion programmes. We tested the efficacy of a teacher professional learning intervention, delivered partially via the internet, designed to maximise opportunities for students to be active during PE lessons and enhance adolescents’ motivation towards PE and PA. Methods A two-arm cluster randomised controlled trial with teachers and Grade 8 students from secondary schools in low socioeconomic areas of Western Sydney, Australia. The Activity and Motivation in Physical Education (AMPED) intervention for secondary school PE teachers included workshops, online learning, implementation tasks and mentoring sessions. The primary outcome was the proportion of PE lesson time that students spent in moderate-to-vigorous physical activity (MVPA), measured by accelerometers at baseline, postintervention (7–8 months after baseline) and maintenance (14–15 months). Secondary outcomes included observed PE teachers’ behaviour during lessons, students’ leisure-time PA and students’ motivation. Results Students (n=1421) from 14 schools completed baseline assessments and were included in linear mixed model analyses. The intervention had positive effects on students’ MVPA during lessons. At postintervention, the adjusted mean difference in the proportion of lesson time spent in MVPA was 5.58% (p\u3c0.001, approximately 4 min/lesson). During the maintenance phase, this effect was 2.64% (p\u3c0.001, approximately 2 min/lesson). The intervention had positive effects on teachers’ behaviour, but did not impact students’ motivation. Conclusions AMPED produced modest improvements in MVPA and compares favourably with previous interventions delivered exclusively face-to-face. Online teacher training could help facilitate widespread dissemination of professional learning interventions