1,720,966 research outputs found
Rainfall, streamflow and sediment relationship in a hilly semi-agricultural catchment in Northern Italy.
No full textThe paper analyzes the rainfall-flow-sediment relationships obtained after two monitoring years in a small semi-agricultural catchment in Apennines mountain range (Italy) with temperate mediterranean climate. The climate seasonality involves intra-annual variability in the hydrological response. Flow characteristics are correlated with rainfall depth, while duration, erosivity and previous rainfall are correlated with flow parameters depending on the season. The lack of a well defined relationship between these variables may be due to the flow mechanisms themselves, that vary with seasons. In summer Hortonian flow dominates, while in the other seasons runoff is generated by the Dunnian mechanism or by a combination of both mechanisms.
Sediment concentration and soil loss are more correlated with streamflow than with rainfall parameters. Silt is the most eroded fractions. There is a significant correlation between the mean diameter of soil particles and the flow within the same flood event, but in general the relationship is influenced by supply condition (soil moisture, initial baseflow, etc)
Thermal conductivity of fired clays: Effects of mineralogical and physical properties of the raw materials
No full textThe physical, chemical and mineralogical properties of representative commercial Italian clays were investigated by X-ray powder diffraction and Rietveld refinements, laser granulometry, X-ray fluorescence spectroscopy and calcimetry. The clays were used to prepare bricks by both extrusion and uniaxial pressing. The effective thermal conductivity of the fired bricks was determined and correlated with physical and mineralogical properties of the raw materials. Unfortunately, the complex nature of the system with many influencing parameters and interactions did not allow linear correlations with single parameters. Hence, a multiple linear regression approach was attempted and a statistically valid model was built for extruded samples. Although the model cannot be regarded as conclusive, due to the system complexity and the limited number of observations, the results gave some indications regarding the role played by the raw materials properties on the effective thermal conductivity of the bricks. The pore forming effect of organic material decreases the thermal conductivity of the bricks. On the contrary, the thermal conductivity increases with decreasing particle size, possibly due to an increased sintering rate and/or improved particle packing. © 2010 Elsevier B.V
Porcelain stoneware with pegmatite and nepheline syenite solid solutions: Pore size distribution and descriptive microstructure
No full textInvestigations correlating the pore size distribution-cumulative pore volume to the microstructure are used to compare the efficiency of two solid solutions of pegmatite and nepheline syenite as fluxing agents for the design of porcelainized stoneware. Particularly the fusibility of the two solid solutions was modified by adjusting the CaO content of the bodies. As results, the pegmatite based flux produced an extended viscous phase capable on embedding the crystalline phases and close open porosity as from 1175°C. Conversely, the bodies with nepheline syenite remained relatively porous up to 1225°C although the similar results of the mechanical strength at this temperature. The investigations on microstructure, pores size distribution and cumulative pore volume indicated almost complete reduction of the open pores in the pegmatite based bodies and the development of a band of closed pores ranged between 0.080 and 0.9μm showing P series as a more compact structure. For the nepheline syenite based bodies, the incomplete reduction of the open pores and the relative absence of the band of pores between 0.080 and 0.9μm were ascribed to the difference in fusibility and the viscosity of the glassy phases. These differences were interpreted in term of the differential action of CaO in Na2O-Al2O3-SiO2 and K2O-Al2O3-SiO2 on the amount and viscosity of the liquid phase formed already described in the literature. © 2013 Elsevier Ltd
Application of heating microscopy on sintering and melting behaviour of natural sands of archaeological interest
No full textIn antiquity, beach sand was one of the main raw materials for glass-making and for the production of other vitreous materials, like Egyptian blue and faience. During the 1st century AD, glass and pigments manufacturing industry was active along the Gulf of Naples, Italy, where we sampled four littoral sands. Samples were analyzed with different techniques: chemical analysis was performed by means of X-Ray Fluorescence (XRF) and mineralogical analyses with X-Ray Powder Diffraction (XRPD) and Raman Spectroscopy. The complete sintering to melting thermal behaviour of the four sands was studied by heating microscopy or hot-stage microscope (HSM) equipped with an high resolution camera capable to collect sample profile during heating. The effect of the grain size on the sintering curves, which were automatically elaborated by specimen profile transformation, was also investigated. Finally, some deductions about the granulometry effect and the presence of alkaline and alkaline-earth oxides on sintering and melting behaviour were drawn. All the four sands were found suitable for highly sintered manufacts rather than glasses, to reach complete amorphous materials the addition of fluxes was necessary
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
Facile synthesis of B-type carbonated nanoapatite with tailored microstructure
No full textNanolime and a phosphate-based chelating agent were used to synthesize B-type carbonated apatite. Developed Rietveld refinement strategies allowed one to determine process yield, product crystallinity as well as structural (unit cell) and microstructural (size, strain) parameters. The effect of synthesis temperature (20-60 °C) as well as Ca/P ratio (1.5-2.5) and solid content (10-30 wt%) of the starting batch on these properties were investigated. FTIR, TEM and gas adsorption data provided supporting evidence. The process yield was 42-60 wt% and found to be governed by the Ca/P ratio. The purified products had high specific surface area (107-186 m2/g) and crystallinity (76-97%). The unit cell parameters, correlated to the degree of structural carbonate, were sensitive to the Ca/P ratio. Instead, temperature governed the microstructural parameters. Less strained and larger crystals were obtained at higher temperatures. Long-term aging up to 6 months at 20 °C compensated for higher crystal growth kinetics at higher temperature. © 2014 Elsevier Inc
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
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