1,720,963 research outputs found
Volcanic Soils: Inverse Modeling of Thermal Conductivity Data
No full textVolcanic ash soils are formed from ash and cinder deposits that largely consist of non-crystalline minerals, volcanic glass and organic matter. Their application to engineering ground technology requires a thorough knowledge and good understanding of their historical formation, structure, mineralogy and thermal and hydraulic properties. Consequently, inverse modeling was applied to the thermal conductivity () data of 22 soils from Hokkaido (northern Japan). A large majority of these soils contained volcanic ash that markedly influenced their physical properties. For example, 11 natural soils (volcanic, highland and lowland soils) had average values of 0.14W m(-1)K(-1) and 0.52Wm(-1)K(-1) at dryness ((dry)) and saturation ((sat)), respectively. The inverse modeling of data revealed that the average values of soil solids ((s)) and volcanic glass ((vgl)) were about 0.48Wm(-1)K(-1) and 0.25Wm(-1)K(-1), respectively. The influence of organic matter on (s) was found to have a minor effect. A reverse analysis of saturated frozen soils revealed that, at -5 degrees C, about 87% of water was converted into ice, i.e., unfrozen water content ((un-w))approximate to 0.13
Thermal Conductivity of Pyroclastic Soil (Pozzolana) from the Environs of Rome
No full textThe paper reveals the experimental procedure and thermo-physical characteristics
of a coarse pyroclastic soil (Pozzolana), from the neighborhoods of Rome,
Italy. The tested samples are comprised of 70.7% sand, 25.9% silt, and 3.4% clay.
Their mineral composition contained 38% pyroxene, 33% analcime, 20% leucite,
6% illite/muscovite, 3% magnetite, and no quartz content was noted. The effective
thermal conductivity of minerals was assessed to be about 2.14W·m−1·K−1. A transient
thermal probe method was applied to measure the thermal conductivity (λ) over
a full range of the degree of saturation (Sr), at two porosities (n) of 0.44 and 0.50,
and at room temperature of about 25 ◦C. The λ data obtained were consistent between
tests and showed an increasing trend with increasing Sr and decreasing n. At full
saturation (Sr = 1), a nearly quintuple λ increase was observed with respect to full
dryness (Sr = 0). In general, the measured data closely followed the natural trend
of λ versus Sr exhibited by published data at room temperature for other unsaturated
soils and sands. The measured λ data had an average root-mean-squared error (RMSE)
of 0.007W·m−1·K−1 and 0.008W·m−1·K−1 for n of 0.50 and 0.44, respectively, as
well as an average relative standard deviation of the mean at the 95%confidence level
(RSDM0.95) of 2.21% and 2.72 % for n of 0.50 and 0.44, respectively.
B V. R. Tarnawski
vlodek.tarnawski
Canadian Field Soils IV: Modeling Thermal Conductivity at Dryness and Saturation
No full textThe thermal conductivity data of 40 Canadian soils at dryness (lambda(dry)) and at full saturation (lambda(sat)) were used to verify 13 predictive models, i.e., four mechanistic, four semi-empirical and five empirical equations. The performance of each model, for lambda(dry) and lambda(sat), was evaluated using a standard deviation (SD) formula. Among the mechanistic models applied to dry soils, the closest lambda(dry) estimates were obtained by MaxRTCM (SD = +/- 0.018 Wm(-1).K-1), followed by de Vries and a series-parallel model (S-||). Among the semi-empirical equations (deVries-ave, Advanced Geometric Mean Model (A-GMM), Chaudhary and Bhandari (C-B) and Chen's equation), the closest lambda(dry) estimates were obtained by the C-B model (+/- 0.022 Wm(-1).K-1). Among the empirical equations, the top lambda(dry) estimates were given by CDry-40 (+/- 0.021 Wm(-1).K-1 and +/- 0.018 Wm(-1).K-1 for18-coarse and 22-fine soils, respectively). In addition, lambda(dry) and lambda(sat) models were applied to the lambda(sat) database of 21 other soils. From all the models tested, only the maxRTCM and the CDry-40 models provided the closest lambda(dry) estimates for the 40 Canadian soils as well as the 21 soils. The best lambda(sat) estimates for the 40-Canadian soils and the 21 soils were given by the A-GMM and the S-|| model
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
On modelling the thermal conductivity of soils using normalized-multi-variable pedotransfer functions
No full textA comprehensive analysis of 6-published and 15-new Kersten (Ke) functions, i.e. normalized soil thermal conductivity (λ) expressions, was conducted using a complete λ data base of 40 Canadian soils. It was confirmed that Ke depended mainly on the degree of soil saturation (Sr), while additional dependency on volumetric content of sand (θsa) as the second variable and organic matter (θo-m) as the third variable , was marginal. Furthermore, a few Ke(Sr) functions did not fully meet the fundamental requirements at Sr boundaries, i.e. and . However, accurate λ estimates were still obtained within small Ke deviations, i.e. and . After applying a least square regression analysis to 21 functions, the following Ke(Sr) were found to be the highest ranking:
From the novel Ke functions, two earned notable attention, namely: the 1st and 3rd Ke functions from the above list. The former is an extension to full Sr range for the original model by Johansen, while the latter is a simple power-exponential function. The λ estimates obtained by the functions listed above closely followed experimental data of a majority of 40-Canadian soils and Standard Sands. Standard deviation (SD) was used to determine the predictive performance of the Ke(Sr) functions: 17-coarse soils SDave ≈ 0.19 W m−1 K−1, 22-fine soils SDave ≈ 0.11 W m−1 K−1, and Standard Sands SDave ≈ 0.16 W m−1 K−1.
In addition, the highest ranking functions, listed above, underwent validation against soil data from different places and dissimilar geneses. In general, the obtained estimates of λ closely follow experimental data: Chinese soils (SDave ≈ 0.160 W m−1 K−1), American soils (SDave ≈ 0.125 W m−1 K−1). However, uncertain λ estimates were obtained for soils of diverse geneses (volcanic origin)
- …
