1,720,982 research outputs found
Acoustic and thermal performances of ceramic tiles and tiling systems
No full textAcoustic and thermal performances of floating floor and/or radiant floor can be improved by using ceramic tiles with tailored porosity and microstructure. Porcelain stonewares are still the most widespread typology of tiles, due to their high physical and mechanical performances coming from a very low level of open porosity and water absorption (≤0.5 wt%). However their closed porosity values, usually neglected, can be significantly different from one product to another. As a consequence, the properties directly dependent on the total porosity, such as thermal and acoustic ones, may be strongly diverse among commercial tiles.
Several commercial porcelain stoneware tiles having different composition, microstructure and porosity, were selected for the present work. These tiles, alone or coupled with different types of resilient underlayer materials (glass fibre, cork and rubber), were studied on the basis of dynamic stiffness. Their acoustic and thermal properties were investigated in terms of thermal conductivity and walking noise reduction
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
High-temperature behaviour of alkali-activated composites based on fly ash and recycled refractory particles
No full textThis study aims to develop innovative and sustainable alkali-activated composites with enhanced performance at high temperatures. To reduce production costs and promote a circular economy model, coal fly ashes are selected as a precursor for the alkali activation and recycled refractory particles are used to develop products with high thermal dimensional stability. Matrices and composites are investigated as a function of two curing conditions (heat curing vs room temperature curing) and amounts of dispersed phase (recycled refractory particles) added to the matrix. Thermal stability is assessed based on thermal exposure in a muffle furnace at 800 and 1000 °C, heating microscope analysis, and dilatometry. In addition, mineralogical quantitative analyses are performed to obtain an insight into phase changing after thermal exposure. Results show that the recycled refractory particles do not hinder the alkali activation process, significantly reduce heat-induced cracking, increase the maximum temperature of dimensional stability of the composites up to 1240 °C, and improve the linear dimensional stability during heating. In addition, the heat curing does not significantly increase the temperature range of dimensional stability, whereas the room temperature curing generates a product less prone to cracking when exposed to high temperature, and therefore it can be preferred
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
Sintered glass-ceramic articles from plasma vitrified asbestos containing waste
No full textPlasma vitrification is a safe technique for eliminating the environmental impact of asbestos-containing materials. Additional advantages may arise from the obtainment of valuable ceramics from vitrified waste, if low cost treatments, comparable to those applied to traditional ceramics, are feasible. In the present paper the application of a fast heating rate (40°C/min) to produce dense sinter-crystallized materials from vitrified asbestos-containing waste, having a strength in excess of 100 MPa, is discussed. Sinter-crystallization, with fast heating processes, constituted also the basis of cellular glass-ceramics and a new type of stoneware, with waste glass replacing conventional feldspar fluxes
Metodo per la realizzazione di prodotti ceramici comprendenti materiale riciclato
No full textThe usage of glasses as additives for traditional ceramics has been extensively investigated. Although interesting (for the properties of the final products), this solution does not generally allow a large absorption of glass. The present application illustrates a novel approach, consisting in replacing the feldspar flux, in the formulation of porcelain stoneware tiles, completely with finely powdered glass, with a specially designed chemical composition, derived from the melting of several inorganic waste (mainly consisting of mining residues and glass cullet). For an optimized glass/clay ratio, the ceramic materials, obtained sintered in a temperature range of 950-1050°C, exhibited a complex of mechanical properties similar to that of conventional porcelain stoneware, which must be sintered at much higher temperatures. This is mainly attributable to interactions between the glass and clay residues upon heat treatment, favoring the precipitation of several reinforcing crystal phases.
The presented process brings several advantages in the field of ceramic manufacturing. A large quantity of waste is potentially absorbed in the form of raw materials, so that ceramic production leads to important environmental benefits. Secondly, the generally high costs of inorganic waste vitrification (due to the high energy consumption during melting) could be reduced or compensated, by the usage of powdered glass (whose production is much simpler than that of massive glass objects and could exploit the low cost plants, currently available in large ceramic industries, dedicated to the preparation of glazes) and the remarkable savings in the raw materials (feldspar fluxes are generally expensive) and in the energy consumption in the sintering process of the new ceramics
'Glass based stoneware' as a promising route for the recycling of waste glasses
No full textSoda-lime-silica scrap or waste glasses are almost widely accepted sintering additives for the manufacturing of traditional ceramics. Although interesting, this solution does not fully exploit the potentialities of glasses compared to feldspar fluxes. In fact, glasses exhibit the softening, and consequently the ability of viscous flow sintering, at much lower temperatures than those required for feldspar melting, and this could be very useful to develop “environmentally friendly” ceramics, i.e. made with a reduced consumption of energy and natural raw materials. In the present study it is reported a high glass recycle approach which replaces the feldspar flux, in the formulation of porcelain stoneware, with finely powdered soda-lime glass or glasses from dismantled cathode ray tubes (CRTs). This allowed the manufacturing of ceramics at 880-920°C and 750-775°C, respectively. The final products were optimised by the addition of calcium hydroxide for soda-lime glass and Al2O3 platelets for CRT glasses, in order to promote the partial devitrification of the glass or control the fracture propagation. Due to their overall mechanical properties (bending strength exceeding 70 MPa, hardness exceeding 6 GPa, fracture toughness exceeding 1.1 MPa m0.5), the new products could find applications in the construction industry
Recycle of waste glass into "Glass-ceramic Stoneware"
No full textThe reuse of soda-lime-silica scrap or waste glasses as additives for traditional ceramics has been extensively investigated in the literature. Although interesting, this solution does not generally allow large quantities of glass to be recycled. The present study reports a novel high glass recycle approach, which replaces, in the formulation of porcelain stoneware, the feldspar flux with finely powdered glass derived from the melting of different waste products, e.g. lime from fume abatement systems, feldspar mining residues and scrap soda-lime glass. At an optimized glass/clay ratio, the “glass-ceramic stoneware” samples sinter at 1000°C. The “glass-ceramic stoneware” has a bending strength approaching 90 MPa and a fracture toughness exceeding 2.0 MPa m0.5, similar to those of conventional porcelain stoneware, which requires sintering at higher temperatures. The high strength and fracture toughness are attributed to the interaction between the glass and clay residues upon sintering, which allows the development of several different crystalline phases
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