1,720,994 research outputs found
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Laminate zeolite structure prepared using papermaking techniques for carbon dioxide capture: synthesis, characterisation and performance
No full textCarbon capture and storage technology has become a possible solution to address the problem of global warming due to the increasing use of fossil fuels. The application of this technology by many carbon dioxide emitting industrial units is still hindered by the process and equipment cost associated with the capture of carbon dioxide. Zeolites have become a major player in this field due to their high adsorption capacity for carbon dioxide. Traditional use of zeolites in the form of pellets or beads has issues relating to high mass transfer resistance and increased energy consumption required to overcome high pressure drop for such systems. Novel structured adsorbents have been developed to manage these problems but they require high precision and cost for their manufacture. Although they are superior to beads/pellets in terms of breakthrough characteristics, they have very low loading of adsorbent. To overcome the limitations of high cost and low loading of non-particulate structures and the disadvantages of the conventional adsorbent structures, new preparatory techniques for adsorbent structures are being researched. For more practical applications, a zeolite structured adsorbent needs to be created that has high adsorption capacity, low pressure drop, high mass transfer and provides overall high system efficiency. In addition, the very large scale of the flue gas capture application demands that the adsorbent structure should be made using low cost materials and processes. Motivated by the low cost of papermaking technology, we have studied and adapted this technique to create a highly loaded, large surface area sheet structure. Zeolites have already found use in the paper industry as fillers and retention aids and can therefore be easily adapted to current paper mills to create structured laminate adsorbents. This project looks towards creating zeolite laminate structured adsorbent using papermaking techniques for carbon dioxide capture. The selection of materials for the preparation of laminate structures is initially done to create structures that are strong and have high porosity with high loading of zeolite. An easy method of preparing laminate zeolite sheet structures is also outlined. This leads to the next part of the project which is characterisation of the zeolite laminate sheet structures. Although few materials were used in preparation of the sheets, the many variables involved in sheet forming would make it very time consuming to create each unique sheet structure and characterise the properties. Hence, to speed up the process, a partial factorial design method was used to characterise the laminate sheets. 16 experiments were completed. SEM and mercury porosity methods were used to characterise the porosity of the sheet structures. These results show that porosity of the structure is mainly affected by the amount of silica present in the structure. Nitrogen adsorption and carbon dioxide adsorption measurements were studied to determine the loading in the laminate sheet structures, since the adsorption capacity is completely dependent on the zeolite. The strength of the laminate structures were measured using a novel testing method as it was difficult to apply the routine strength measurement methods to some of the weak laminate samples. Considering the application of the laminate structures, a vibratory sieve was used to determine the comparative strength of the different structures from the partial factorial design. It was found that laminate structures with either 40-55wt% micron zeolite or 30wt% nano zeolite had adequate strength for breakthrough testing. Structures with higher loading of zeolite fell apart very easily. The kinetics of the laminate samples were also measured using the Rate of Adsorption software in ASAP 2010. These results show that the presence of nano zeolite increases the adsorption kinetics of the laminate structures and on the whole the laminate structure had higher kinetics when compared to powder or beads due to overcoming macropore diffusion resistance. The structures which had the best characteristics from the partial factorial design were used for breakthrough testing. Testing for different porosities, it was found that structures with high porosity i.e. samples having 40wt% zeolite had higher effective diffusivities and lower pressure drop when compared to structure with low porosity i.e. samples having 20wt% zeolite. Other methods of increasing spacing between the folds of the laminate structures were also tested and using a wire to create spacing was found to be the best method to lower pressure drop. In some instances, the effective diffusivities were reduced while in other instances they were the same. But the method of winding to produce laminate structures for breakthrough testing produced highly variable results. An idea of printing hydrophobic channels on the paper samples was considered to improve breakthrough characteristics of the laminate structures. Since printing is easy, cheap and can be adapted to a large industrial setting, this method of creating channels for gas flow in the laminate structures has many advantages. An initial assessment of this method showed that using AKD to create hydrophobic patterns on the sheet was successful as different levels of depth were observed between the AKD treated and untreated sections in the final laminate structure. To create distinguishable regions of AKD treated and untreated sections, the amount of the zeolite loading and ceramic loading were also fixed at 8g zeolite and 6.5g ceramic fibres. A method of printing parallel hydrophobic channels was established and the sheets were coated with two different weight % of colloidal silica (40wt% and 20wt%). These differing amounts of colloidal silica create laminate structures with different depths of channels as seen from SEM imaging. Breakthrough assessment of the printed laminate structures show that the structures with 20wt% silica have higher effective diffusivities and lower pressure drop when compared to structures with 40wt% silica or structures without hydrophobic printing, showing that laminate structures with printed channels is a very attractive adsorbent structure for CO2 capture
Eco-friendly cellulose nanofibre membranes
No full textDue to the rapid population growth, mounting energy concerns and increasing environmental crisis, the development of new and more energy efficient membranes for water and air purification is becoming an important task. Currently, membranes made from petro-based polymers are used. Although they have been widely recognized because of their excellent properties, they pose environmental problems during production and disposal stages of the life cycle. The essential characteristics of next generation membranes should be high efficiency, high durability, low operating pressure, low cost, and be able to be fabricated using environmentally friendly processes. Cellulose nanofibres are of technological interests as renewable, sustainable and eco-and bio-friendly raw materials to produce such nanomembranes. They possess excellent properties and can be used in environmental, biomedical and other functional filtration applications. The research in this thesis focused on developing the ‘green’ nano-membrane having high mechanical strength and pore size control. Cellulose nanofibre dimensions, diameter and length, are critical for establishing the structure-property relationships in the later part of this research. Cellulose nanofibre diameter controls the pore size of the nanofibre membranes and aspect ratio controls the preparation of nanofibre membrane via filtration. There is currently no easy means of rapidly quantifying aspect ratio of nanofibres because the two ends of nanofibres cannot be seen in microscopic images due to entanglement between fibres, although diameter distributions can be measured from microscopic images at high magnification. A simple method was developed to estimate aspect ratio of nanofibres from sedimentation and yield stress measurements. The gel-point was measured both from the height of a layer of cellulose nanofibres sedimented from a dilute suspension or from the lowest solids concentration at which a yield stress could be measured using a vane rheometer. The two methods were closely in agreement for all samples. Aspect ratio was then calculated using either the Effective Medium (EMT) or Crowding Number (CN) theories. Fabrication of nanofibre sheet is time consuming for the existing methods because they use fine filter media to retain the cellulose nanofibres on filter medium. A rapid and commercially feasible method for preparing cellulose nanofibre sheet was developed to produce high quality nanofibre sheets using large pore size filter medium. The retention of nanofibres is improved by using the concentration of the forming suspension higher than connectivity threshold to allow the connected fibre suspension to bridge over the large pore openings. Nanofibre sheet preparation required 13 minutes in total. The mechanical strength of cellulose nanofibre paper is a key property but tensile strength measurement requires a substantial amount of test material. To minimise the time for testing mechanical properties and the loss of sample, it has been established that zero/short span test can be used instead of standard tensile test to measure the tensile strength for nanofibre sheets. This is because there are no fibres bridging between and directly gripped by both jaws, just as the case in tensile tests. The zero-span test was shown to be a sensitive measure of the sheet strength at a short scale. Cellulose nanofibre sheets possess good dry and wet strength compared to standard cellulose fibre sheets. However, wet strength of nanofibre sheet is low for use in certain applications like filtration. The effect of the addition of two cationic polymers, CPAM and PAE, on cellulose nanofibre sheet forming characteristics such as water drainage and nanofibre retention and strength of cellulose nanofibre sheet is investigated. It is found that the retention of nanofibre increased with the addition of either polymer; in addition wet strength of nanofibre sheet greatly increased with the addition of PAE. The method developed to prepared nanofibre sheet with high wet strength, was adapted to prepare nanofibre membranes and nanofibre composite membranes. Their performance in filtration applications was then evaluated. Cellulose nanofibre composite membranes were prepared using suspensions of cellulose nanofibres, silica nanoparticles (22nm) and polyamide-amine-epichlorohydrin (PAE) via filtration. It was demonstrated that silica nanoparticles act as spacers to control pore size of nanofibre network. PAE was added to adhere the negatively-charged nanoparticles to the nanofibres and also to improve the wet strength of the membrane. Membranes prepared with nanofibres alone showed high flux but low rejection due to large pore size. In contrast, nanofibre composite membranes showed water flux of 80 LMH (litres per square meter per hour) and Molecular Weight Cut Off of 200 kDa. The addition of silica nano particles controlled pore size. These results demonstrate the potential of cellulose nanofibre composite membranes in ultrafiltration. The produced membranes are readily recyclable as a feed stock to a conventional paper making process. By conducting these studies, a novel strategy to rapidly produce eco-friendly cellulose nanofibre composite membranes for ultrafiltration applications was developed
Strength agent: PAE application in TMP rejects
No full textIn this paper cationic polymer Nopcobond 1213 as a class of polyamideamine epichorohydrin (PAE) resins were used to enhance the wet and the dry strength of paper at 5 different addition rate 0mg/g, 2mg/g, 5mg/g, 10mg/g and 20mg/g by mixing with two types of pulp with three different pressing level (0bar, 3.75 bar and 5.6 bar): (1) reject TMP radiate pine pulp taken from the feed stream of the rejected refiner (2.09% shive content); (2) fractionated shive-free of the first type of pulp. This study has found that Nopcobond 1213 significantly increases strength for handsheets made from both type of pulp and 5mg/g is the optimum addition rate. In addition, light basis weight, about 0.2-0.35 kg/m3 paper products are able to made from the TMP reject stream with desirable tensile strength (dry tensile index about 10-25 Nm/g, wet tensile index about 1-7 Nm/g). Handsheet were made and tested for physical properties and opacity properties including bulk, tensile strength, bending stiffness, fibre strength and formation, ring crush compressive strength, light scattering coefficient and opacity. Due to the long fibre and small amount of fines loss in the shive-free pulp, test samples showed relatively lower tensile strength compared to the whole pulp. Moreover, the shive-free handsheets did not completely dry in the drying process (due to wrinkles formation of high temperature), freely dried shive-free handsheets had worse formation than handsheets made from the whole pulp (as they are totally dried in drying section), therefore polymer in the shive-free handsheets reduced its performance in imparting paper strength. The whole pulp handsheets with better formation and more long fibres in the pulp showed good strength but relatively lower light scattering coefficient and opacity. The coarse and large fibres made handsheets from the whole pulp less sensitive to the different levels of pressing
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