1,720,967 research outputs found
Thermal Response of Helix Ground Heat Exchangers
No full textThis paper is devoted to the thermal analysis of shallow ground heat exchangers with pipes arranged in a helix configuration. The pipes where the carrier fluid is circulated typically embrace a cylindrical volume that is filled by ground or concrete, the latter being the case of the so called geopiles. Other pipes dispositions include conic helices that can be easily inserted in proper excavations. The analysis of the transient thermal behavior of a helix/ground assembly is here carried out according to different approaches, including the exploitation of superposition techniques, the finite element modelling and experiments in a reduced scale mock up. Different geometrical configurations have been taken into account and also the variability of ground and concrete thermal properties have been considered. A detailed description of the experimental set up is provided and the model results have been processed in order to develop suitable temperature response factors (or g -functions) to be employed for predicting the ground heat exchanger behavior in different operating conditions
Suivi temporel des perturbations thermiques induites par les corbeilles géothermiques : modélisation pétrophysique et imagerie géo-électrique
No full textBasket geothermal heat exchanger buried at shallow depth and connected to heat pumps can be used to heat and/or cool buildings. Heat transfers and performance related to geothermal basket are complex due to heterogeneous petrophysical properties of the soil, freezing of ground and surface environmental conditions e.g. air temperature variations. To study heat transfers, a geophysical monitoring of electrical conductivity and induced polarization has been developed using three experiments at different scales. First, a petrophysical model was designed from laboratory measurements. This model describes at the pore scale, the variation of electrical conductivity and chargeability according to the soil temperature and frost. This model was applied to an in-situ experiment to monitor the growth of an ice-core. We have also designed an analogic experiment at small scale and under controlled conditions in order to study the heat transfers and the effect of the soil freezing according to different environmental conditions. This study shows the importance of lateral flow and the influence of freezing during system operation. The petrophysical model was tested and validated with several datasets and geophysical monitoring was able to detect the formation and melting of the ice core.Les corbeilles géothermiques sont des échangeurs thermiques hélicoïdaux implantés dans le proche sous-sol qui couplés à une pompe à chaleur, permettent de chauffer et/ou de rafraichir les bâtiments. Comprendre les transferts thermiques liés à ces systèmes et étudier leurs performances requiert de prendre en compte les propriétés pétrophysiques hétérogènes du sol, les phénomènes de changement de phase et les conditions environnementales, dont les variations de température de l’air et la pluviométrie. Dans ce but un monitoring géophysique en conductivité électrique et en polarisation provoquée a été développé à l’aide de trois expériences à différentes échelles. Tout d’abord, un modèle pétrophysique a été élaboré à partir d’une série d’expériences en laboratoire. Ce modèle décrit la variation de la conductivité électrique et de la chargeabilité en fonction de la température et du gel du sol à l’échelle porale. Ce modèle a été appliqué à une expérience in-situ pour suivre la formation d’un noyau de glace. Nous avons aussi développé une expérience analogique à échelle réduite et en conditions contrôlée pour mieux comprendre les transferts de chaleur au sein du sol et étudier l’impact du gel dans différentes conditions environnementales. Ces études ont montré l’importance des apports thermiques latéraux et l’impact du changement de phase lors du prélèvement de chaleur par la corbeille. Le modèle pétrophysique a été validé sur plusieurs jeux de données et les résultats du monitoring géophysique permettent de détecter la formation et la fonte d’un noyau glace
Temporal monitoring of thermal disturbances induced by shallow heat exchangers : petrophysics modeling and geo-electrical imaging
No full textLes corbeilles géothermiques sont des échangeurs thermiques hélicoïdaux implantés dans le proche sous-sol qui couplés à une pompe à chaleur, permettent de chauffer et/ou de rafraichir les bâtiments. Comprendre les transferts thermiques liés à ces systèmes et étudier leurs performances requiert de prendre en compte les propriétés pétrophysiques hétérogènes du sol, les phénomènes de changement de phase et les conditions environnementales, dont les variations de température de l’air et la pluviométrie. Dans ce but un monitoring géophysique en conductivité électrique et en polarisation provoquée a été développé à l’aide de trois expériences à différentes échelles. Tout d’abord, un modèle pétrophysique a été élaboré à partir d’une série d’expériences en laboratoire. Ce modèle décrit la variation de la conductivité électrique et de la chargeabilité en fonction de la température et du gel du sol à l’échelle porale. Ce modèle a été appliqué à une expérience in-situ pour suivre la formation d’un noyau de glace. Nous avons aussi développé une expérience analogique à échelle réduite et en conditions contrôlée pour mieux comprendre les transferts de chaleur au sein du sol et étudier l’impact du gel dans différentes conditions environnementales. Ces études ont montré l’importance des apports thermiques latéraux et l’impact du changement de phase lors du prélèvement de chaleur par la corbeille. Le modèle pétrophysique a été validé sur plusieurs jeux de données et les résultats du monitoring géophysique permettent de détecter la formation et la fonte d’un noyau glace.Basket geothermal heat exchanger buried at shallow depth and connected to heat pumps can be used to heat and/or cool buildings. Heat transfers and performance related to geothermal basket are complex due to heterogeneous petrophysical properties of the soil, freezing of ground and surface environmental conditions e.g. air temperature variations. To study heat transfers, a geophysical monitoring of electrical conductivity and induced polarization has been developed using three experiments at different scales. First, a petrophysical model was designed from laboratory measurements. This model describes at the pore scale, the variation of electrical conductivity and chargeability according to the soil temperature and frost. This model was applied to an in-situ experiment to monitor the growth of an ice-core. We have also designed an analogic experiment at small scale and under controlled conditions in order to study the heat transfers and the effect of the soil freezing according to different environmental conditions. This study shows the importance of lateral flow and the influence of freezing during system operation. The petrophysical model was tested and validated with several datasets and geophysical monitoring was able to detect the formation and melting of the ice core
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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