1,721,105 research outputs found
CFD simulation of pollutant dispersion around buildings: comparison between RANS k-ε and LES approaches
No full textTurbulence modeling is a key issue in computational wind engineering, particularly in the prediction of pollutant dispersion in cities. To be directly applicable, turbulence models
need validation by comparison with experiments. This paper evaluates the performance of two different modeling approaches (RANS k-e and LES) for three test cases with varying complexity. For each case, wind tunnel experiments are used for validation. It is shown that the performance of the standard k-e model is very case-dependent and that it also depends on the turbulent Schmidt number, whose optimum value is a priori unknown. On the contrary, LES with the dynamic subgrid-scale model shows a good performance for all cases, without requiring any parameter input to solve the dispersion equation. For the test case of an actual urban environment, predicted concentration values with LES differ from experiments by less than a factor of 2, compared to less than a factor of 4 with the standard k-e model
Mechanically ventilated double skin Façade with semi-transparent photovoltaics, implementing electrical storage and heat pumps to reduce peak demand
No full textSemi-Transparent Photovoltaics (STPV) can be integrated on Double Skin Facades (DSF) to enhance the electrical and thermal performance of a building. In a mechanically ventilated DSF, the heat extracted from the DSF can be used to increase the Coefficient of Performance (COP) of a heat pump based mechanical system, or it can be introduced directly to the building. In addition, the STPV integrated on the outermost layer of the DSF, can control the solar gains, may allow controlled levels of the daylight into the zone and creates a microclimate around the building. In the present study we investigate the mismatch between the electricity production by the STPV and the electricity needed for heating and lighting by the adjacent building zones and develop ways of reducing this mismatch. A DSF-STPV combination, coupled with battery storage within the building, is considered in order to shift the peak demand of the building and provide better matching of generation and loads. Because STPV is integrated in the DSF, the heating demand during the day decreases as the building receives solar heat gains and at the same time produces electricity. This electricity produced by the STPV can be stored in a battery and later be used at the grid peak hours to reduce the peak demand by operating the heat pump. The preheated air, that is flowing within the cavity of the DSF-STPV, assists an air sourced heat pump to increase its COP and the heat produced is used to keep the building warm during the grid peak hours when the set point is reduced. With the use of such a predictive heating strategy, the peak demand of the building can coincide with the peak of the solar electricity production resulting in more than 80% reduction in the electricity consumption during the peak demand hours of the grid
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
Modeling of double skin façades integrating photovoltaic panels and automated roller shades: Analysis of the thermal and electrical performance
Full text linkA numerical model is developed for simulating a single or multi–story Double Skin Façade integrating Photovoltaics (DSF-PV). The DSF-PV can co-generate solar electricity and heat, while it also allows daylight to be transmitted to the interior space. The buoyancy-driven air flow inside the cavity may be assisted by a fan to cool down the photovoltaics while providing natural or hybrid ventilation to adjacent zones. Automated roller shades are also implemented in the model and help regulate heating and cooling loads but also control the daylight levels in the indoor space. A parametric analysis for different control strategies for the airflow within the cavity and the roller shading devices is performed with the purpose to apply the proposed methodology to minimize the heating and cooling demand of the DSF-PV system. In addition, a parametric analysis for different adjacent zones floor areas is performed. The simulations show that a DSF-PV system can supply approximately 120kWh/façade area/year covering the yearly electricity demand of the adjacent office if the floor area is approximately less than 3 times larger than the floor area
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
Double skin façades integrating photovoltaics and active shadings: a case study for different climates
No full textIn this paper the energy potential of an innovative Double Skin Façade integrating
Photovoltaics (DSF-P) for different weather conditions is investigated. The proposed system
consists of semi-transparent and opaque PV modules integrated in the exterior skin of the
façade and active shading devices implemented within the cavity. The innovative single or
multi–story proposed DSF can co-generate solar electricity and thermal energy (for space
heating or other building applications). In order to effectively cool down the photovoltaics
and increase their electrical efficiency, the buoyancy-driven air flow within the cavity may be
assisted by a fan (natural / hybrid ventilation). Active roller blinds are taken into account to
regulate heating and cooling loads while controlling the daylight in the corresponding
adjacent indoor spaces. With the aim to simulate the system performance, the temperature
distribution and the airflow in the DSF, a mathematical model was developed. It is also
capable to predict the energy flow, as well as the active and passive effects of the DSF-P on
the energy consumption of the adjacent perimeter zones. The simulation model is based on a
detailed transient finite difference thermal network, including accurate algorithms for the
calculation of the heat transfer phenomena taking place within the DSF-P. The model, also
allows performing parametric and sensitivity analyses, useful for pre-feasibility studies at the
design phase of new buildings or for retrofit projects implementing the proposed DSF-P. In
this paper, in order to determine the values of critical design and operating parameters that
minimize the overall energy consumptions, a parametric analysis is carried out. Thus, a case
study related to a high-rise office building located in diverse climate zones is presented.
Simulation results show the effects due to some crucial DSF-P design and operation
parameters on the energy demand of the adjacent zones, and the effectiveness of the proposed
system to reach the goal of net zero energy building
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