1,720,963 research outputs found
Notch sensitivity on fully reversed axial fatigue behaviour of different polypropylene compounds
No full textNowadays recycling is one of the most important keyword to reduce product-costs. In view of this, thermoplastics are very attractive materials for their recycling feasibility. In this paper the static behaviour, the fatigue behaviour and the damage evolution of different polypropylene compounds, characterised by different fractions of recycled material, were investigated. Their fatigue notch sensitivity was analysed as well.
Tensile static and fully reversed fatigue tests were carried out on three different material systems, namely a 42 wt% calcium carbonate filled polypropylene (PP), a 42 wt% calcium carbonate filled polypropylene containing 25% recycled PP and a 42 wt% calcium carbonate filled 100% recycled polypropylene. The notch sensitivity was investigated on double-edge notched specimens machined from 5-mm-thick injected moulded plates. Three different notch geometries were analysed, namely a 10 mm semicircular notch radius, a 2 mm U-notch radius and a 0.5 mm V-notch radius. During the experimental tests, the damage evolution was investigated by using an on board travelling microscope. As a result, it was found that all materials are largely notch insensitive in high cycle fatigue
Fully Reversed Axial Notch Fatigue Behaviour of Virgin and Recycled Polypropylene Compounds
No full textIn this paper, the fatigue behaviour of different polypropylene compounds, characterized by different fractions of recycled material, were analysed. Fully reversed fatigue tests were carried out on three different polypropylene (PP) compounds, namely a 42 wt% calcium carbonate filled PP (EA209), a 42 wt% calcium carbonate filled polypropylene containing 25% recycled PP (R2025) and a 42 wt% calcium carbonate filled 100% recycled polypropylene (R2100). Both plain and notched samples were tested. In particular, the notch sensitivity was investigated on double-edge notched specimens machined from 5-mm-thick injected moulded plates. Three different notch geometries were analysed, namely a 10 mm circular notch radius (Kt=1.65), a 2 mm U-notch radius (Kt=3.17) and a 0.5 mm V-notch radius (Kt=5.97). During the experimental tests, the fatigue damage evolution was monitored by using on board travelling microscope and, after failure, fracture surfaces were analysed as well. In view of this extensive body of evidence, it was concluded that the analysed PP compounds are notch insensitive. The presence of 25% recycled PP slightly influenced the fatigue behaviour with respect to the compound made of virgin PP. Consequently, in the present paper, a single design-stress-life curve was proposed for EA209 and R2025 plain and notched compounds, characterised by an inverse slope, k, equal to 13 and a reference net stress amplitude evaluated at 2 million cycles, A,50%, equal to 11 MPa. Conversely, a down-graded stress-life design curve was determined for R2100 compound, having k=16 and A,50%=8 MPa. Finally, the fatigue damage analysis highlighted that damage mechanisms and their evolution were independent on the type of material and notch radius and consisted of void formation and coalescence
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
Improved storage and disposal of dried tannery sludges
No full textIn this work we quantitatively studied the opportunities to improve the compaction of dried wastewater treatment sludges from tanneries, possibly combining with pelletization. Measurements of bulk density have been carried out at the industrial and laboratory scale, using different packing procedures, amenable to industrial processes. Waste as powder, pellets and their mixtures have been considered. Mixtures of powder and pellets is the best packing policy. The best compaction results was achieved by controlled vibration of a 30/70%wt mixture of powders and pellets, leading to a final bulk density of 1 t/m3, i.e. an improvement of compaction by more than 54% with respect to poured powders, but also larger than 35% compared to poured pellets. That means increasing the mass storage capacity by a factor of 1.56
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
Improved compaction of dried tannery wastewater sludge
No full textWe quantitatively studied the advantages of improving the compaction of a powder waste by several techniques, including its pelletization. The goal is increasing the mass storage capacity in a given storage volume, and reducing the permeability of air and moisture, that may trigger exothermic spontaneous reactions in organic waste, particularly as powders. The study is based on dried sludges from a wastewater treatment, mainly from tanneries, but the indications are valid and useful for any waste in the form of powder, suitable to pelletization. Measurements of bulk density have been carried out at the industrial and laboratory scale, using different packing procedures, amenable to industrial processes. Waste as powder, pellets and their mixtures have been considered. The bulk density of waste as powder increases from 0.64 t/m3 (simply poured) to 0.74 t/m3 (tapped) and finally to 0.82 t/m3 by a suitable, yet simple, packing procedure that we called dispersion filling, with a net gain of 28% in the compaction by simply modifying the collection procedure. Pelletization increases compaction by definition, but the packing of pellets is relatively coarse. Some increase in bulk density of pellets can be achieved by tapping; vibration and dispersion filling are not efficient with pellets. Mixtures of powder and pellets is the optimal packing policy. The best compaction result was achieved by controlled vibration of a 30/70 wt% mixture of powders and pellets, leading to a final bulk density of 1 t/m3, i.e. an improvement of compaction by more than 54% with respect to simply poured powders, but also larger than 35% compared to just pellets. That means increasing the mass storage capacity by a factor of 1.56. Interestingly, vibration can be the most or the least effective procedure to improve compaction of mixtures, depending on characteristics of vibration. The optimal packing (30/70 wt% powders/pellets) proved to effectively mitigate the onset of smouldering, leading to self-heating, according to standard tests, whereas the pure pelletization totally removes the self-heating hazard
Self-heating of dried industrial tannery wastewater sludge induced by pyrophoric iron sulfides formation
No full textSimilarly to many powders of solids, dried sludge originated from tannery wastewater may result in a self-heating process, under given circumstances. In most cases, it causes a moderate heating (reaching 70-90°C), but larger, off-design residence times in the drier, in a suboxic atmosphere, extremely reactive solids can be produced. Tannery waste contains several chemicals that mostly end up in the wastewater treatment sludge. Unexpected and uncontrolled self heating could lead to a combustion and even to environmental problems. Elaborating on previous studies, with the addition of several analytical determinations, before and after the self-heating, we attempted to formulate a mechanism for the onset of heating. We demonstrated that the system Fe/S/O has been involved in the process. We proved that the formation of small quantities of pyrophoric iron sulfides is the key. They are converted to sulfated by reaction with water and oxygen with exothermic processes. The pyrite/pyrrhotite production depends on the sludge drying process. The oxidation of sulfides to oxides and sulfates through exothermic steps, reasonably catalyzed by metals in the sludge, occurs preferentially in a moist environment. The mechanism has been proved by reproducing in the laboratory prolonged heating under anoxic/suboxic atmosphere
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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