1,720,987 research outputs found
R-value estimation by local thermographic analysis
No full textIR thermography applied in a proper way is able to detect very accurately temperature difference between air and surfaces. By means of this tool is now possible to analyse the local instantaneous heat flux through the surface of a building. In case of steady thermal state, this gives the thermal performance evaluation of the building envelope. In case of a transient condition an averaging process or a system identification algorithm must be applied on time-series of such a data. In any case, it is demonstrated that a standard technique based on thermal flux meter for the thermal resistance (R-value) measurements is more affected by errors than thermographic measurements using this new approach. The method is illustrated with experimental results obtained into a residential building. A dedicated thermographic apparatus is used to map the temperature of the indoor surface of an internal wall and to measure in same positions the air temperature at 10 cm from the surface. From these data the local heat flux is detected at any point of the internal surface. A conventional thermogram of the corresponding outside surface or the outdoor air temperature history allows an easy way to achieve both thermal conductance and transmittance of the investigated wall. In this way it is possible the evaluation of both radiative and convective heat flux on a local basis with a space resolution of 1 cm. The results are here presented within a comparison with the local measurement with a thermal flux-meter device. These results are important in order to enhance energy efficiency and comfort in buildings
Automatic U-value measurement by local thermographic analysis
No full textThe measurement of U-value is an important issue for energy budget evaluation, but conventional techniques are not satisfactory. To date, IR thermography has barely been used for a qualitative measurement or to support other standardized measuring. The proposed method is able to very accurately detect the temperature difference between the air and a surface. The instantaneous heat flux through the inner surface of a room is monitored starting from a local mapping of such data. The improvements detailed in this paper include the evaluation of both convective and radiative heat flux on a local basis with a space resolution of 1 cm. In particular, the surface heat exchange coefficient is evaluated with a fast algorithm. A steady thermal state, with the help of the outside air temperature, allows for the thermal performance evaluation of the building envelope. In the case of a transient condition, an averaging process or a system identification algorithm must be applied on time-series of such data. An automatic procedure has been set up in order to accomplish this recording. In either case, it is shown that a conventional technique based on heat flux metering for the U-value measurement is much less informative about critical points than quantitative IR thermography. Tests in situ are reported and compared with results obtained both by the standard methods for measurement and computation
High resolution and automatic survey of buildings by IR thermography
No full textThe paper illustrates a new approach to achieve the temperature distribution of a buildings composing a global view,
at high resolution. It starts from the state of the art and describes how to manage the thermograms content. The on line
radiometric calibration of raw thermograms allows obtaining a high accuracy of temperature readings. The calibration is
performed using a grid of special targets viewed by the thermographic camera.
An accurate global view of the building envelope is produced with images of thousands per thousands pixels trough
an automatic mosaic composition of thermograms. Advanced image processing, including the geometric correction is
performed in real time. The final result is a 3D model of the building, georeferenced and with capability to perform heat flux
measurements.
In addition, IR images, Near IR and visible electromagnetic bands are fused for the building material evaluation.
As case study, the exterior surface of Palazzo Ducale in Venice, is analyzed and illustrated
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
Infrared thermography for moisture detection : a laboratory study and on the field test
No full textIR Thermography (IRT) is applied to map moisture distribution, to localise areas with anomalous water content.
In this paper two different approaches are presented using IR thermography as a tool for mapping evaporation flux on the surface, with the aim to find out the limits of the technique.
The first part of the paper illustrates a set of laboratory measurements, which allows evaluating the evaporation rate versus the moisture content of different porous materials and the diffusion of water inside the wall. By data of evaporation flux measured in laboratory on samples it is possible to understand the behaviour of water inside the meso- and micro-pores to obtain an empirical relationship between evaporation flux and the cooling recorded by thermography, under particular conditions. From the typical trend of evaporation flux rate it is possible to infer a way to read thermographic passive surveys in order to single out the areas more at risk due to surface degradation.
Secondarily, active and passive tests are applied in situ in order to map on the building surface different regions accordingly to the water evaporation. The output is not the absolute moisture evaluation, but a value ranked accordingly a scale, where the saturation condition represents the minimum negative value and the zero is the physiological moisture content (dry). This map is coupled to the IR picture of the surface whose temperature is given by the natural evaporation when equilibrium conditions with the environment are reached, as in the passive approach. This is obtained by processing the experimental data using a robust algorithm, that is able to synthesize the surface temperature history during the test with enhanced evaporation
Characterization of radiant systems for heating and cooling
No full textWater based surface embedded heating and cooling systems exhibit peculiar features compared with other HVAC systems. Therefore, many studies have been developed defining how to design and test the components of these systems. Nevertheless, advanced technical solutions requires a deeper analysis of the performances both of the components and of the overall assembly. In the following study a low-thickness heating and cooling radiant module with a non-conventional geometry of the embedded piping layer points out some open issues. The thermal performance of this system have been measured inside a climatic chamber; tests are combined with simulations in order to set up numerical models, successively used for the optimization of the system. A test facility has been set up for measuring the performance of a full scale heating and cooling floor designed for industrial applications.Different alternative methods have been applied to measure the heat delivered to the conditioned environment. Among them, the well-known enthalpy balance is used as a reference. A new method, based on quantitative infrared thermography, has been developed in order to determine local heat fluxes, with centimetric spatial resolution on the surfaces. Results collected for two years by the different methods have been compared and analyzed. The comparison, applied both to wide and narrow surfaces, suggests some useful remarks on the characterization procedures derived from current standards
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
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