1,721,013 research outputs found
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
Assessment of biological nutrients removal from the supernatant originating fromt the anaerobic digestion of the organic fraction of the municipal solid waste
No full textThis work critically evaluates the biological processes and technologies applied to remove nitrogen and phosphorus from the anaerobic supernatant produced from the treatment of the organic fraction of municipal solid waste (OFMSW) and from its co-digestion with other biodegradable organic waste (BOW) streams. The wide application of anaerobic digestion for the treatment of several organic waste streams results in the production of high quantities of anaerobic effluents. Such effluents are characterized by high nutrient content, since organic and particulate nitrogen and phosphorus are hydrolysed in the anaerobic digestion process. Consequently, adequate post treatment of this stream is required in order to comply with the existing land application, water reuse and discharge legislation in the European Union (EU) countries. This may include physicochemical and biological processes, with the latter being more advantageous due to their lower cost. Nitrogen removal is accomplished through the conventional nitrification/denitrification, short-cut nitrogen removal (i.e. nitritation/denitritation) and the complete autotrophic nitrogen removal process; the latter is accomplished by the anaerobic ammonium oxidation (anammox) process. As this liquid stream is characterized by low COD/TKN ratio, conventional denitrification/nitrification is not an attractive option; short-cut nitrogen removal and autotrophic nitrogen removal are more promising processes. Both suspended and attached growth processes have been employed to treat the anaerobic supernatant. Specifically, the sequencing batch reactor (SBR), the membrane bioreactor (MBR), the conventional activated sludge (CAS) and the moving bed biofilm reactor (MBBR) processes have been investigated. Physicochemical phosphorus removal via struvite precipitation has been extensively examined. Enhanced biological phosphorus removal from the anaerobic supernatant can take place through the sequential anaerobic/aerobic or anoxic/aerobic processes. More recently, denitrifying phosphorus removal via nitrite or nitrate has been explored. The removal of phosphorus from the anaerobic supernatant of OFMSW is an interesting research topic which has not yet been explored. The anaerobic effluent is often recycled back into the digester; however, this may result in the inhibition of the process due to the accumulation of dissolved ions (i.e. chloride, ammonium) and potentially other substances in the reactor. Consequently, it is possible to recycle only part of the effluent. At the moment standardization in the design of facilities that treat anaerobic supernatant produced from the treatment of OFMSW is still under development. To move towards this direction it is first necessary to assess the performance of alternative treatment options. This work (i) concentrates existing data regarding the characteristics of the anaerobic supernatant produced from the treatment of OFMSW and from their co-digestion with other BOW, (ii) provides data documenting the effect of the anaerobic digestion operating conditions on the supernatant quality and (iii) critically evaluates alternative options for the post-treatment of the liquid fraction produced from the anaerobic digestion process
Production and use of short chain fatty acids to enhance the via-nitrite biological nutrients removal from anaerobic supernatant
No full textThe use of the different external carbon source was investigated to enhance the short-cut nitrificationdenitrification (SCND) and the denitrifying phosphorus removal via nitrite (DPRN) using a sequencing batch reactor (SBR) to treat anaerobic supernatant. The SBR was fed with liquid effluent from the anaerobic co-digestion of waste activated sludge (WAS) and organic fraction of municipal solid waste (OFMSW). After the start-up period of 20 days, a stable and reliable via-nitrite pathway was achieved. Then, three available carbon sources (fresh drainage liquid from OFMSW, fermentation liquid from OFMSW, cattle manure and maize silage (CM&MS) fermentation liquid) were investigated. Significant insitu specific denitritation rates (sNUR) in the range of 0.51-1.16 kgNO2-N / kgVSSd were obtained for OFMSW and CM&MS related carbon sources. The specific consumptions obtained for the liquid effluents from OFMSW and CM&MS raged from 2.7-3.1 kgCOD / kgNO 2-Nrem. The presence of short chain fatty acids (SCFA), namely butyric and propionic acids in the fermentation liquid enhanced the DPRN. The cost of the external carbon source can be lower than 0.1 € / kgCOD when OFMSW is fermented. The total specific cost for nitrogen removal may decrease by 22% when the OFMSW fermentation liquid is used instead of methano
GASEOUS EMISSIONS FROM THE BIOLOGICAL VIA NITRITE NITROGEN REMOVAL PROCESS TREATING ANAEROBICALLY CO-DIGESTED EFFLUENTS
No full textIn this work the gaseous emissions of nitrous oxide (N2O), carbon dioxide (CO2) methane (CH4),
ammonia (NH3) and methyl mercaptan (CH3SH) produced from the nitritation/denitritation
biological nutrient removal (BNR) process were determined in a sequencing batch reactor
(SBR). The SBR treated the anaerobic supernatant produced from the anaerobic co-digestion of
the organic fraction of municipal solid waste (OFMSW) and waste activated sludge (WAS). Two
experimental periods were carried out: period 1 in which a volumetric nitrogen loading rate
(vNLR) of 0.81 kgN/m3d was applied, using acetic acid as carbon source and period 2 with
vNLR=1.09 kgN/m3d using fermentation liquid produced from biowaste as carbon source. N2O
emissions were 0.24% and 1.38% of the influent nitrogen load in periods 1 and 2 respectively.
The higher dissolved oxygen (DO= 1.5 mg/L) concentration as well as the lower accumulation of
nitrite resulted in significantly lower N2O emissions in period 1 compared to 2. NH3 emissions
were very low (<1% of influent nitrogen load), while some methane (5.3% of influent load as
COD) was emitted during period 2, as the lower DO (0.95 mg/L) concentration probably created
micro-anaerobic conditions within the sludge flocs; this was also favoured by the use of
fermentation liquid as a carbon source
Coupling the treatment of low strength anaerobic effluent with fermented biowaste for nutrient removal via nitrite
No full textNutrient removal via nitrite was investigated in a sequencing batch reactor (SBR) treating low strength effluent produced from an upflow anaerobic sludge blanket (UASB). Domestic organic waste (DOW) and vegetable and fruit waste (VFW) were fermented and applied as external carbon source to the SBR. Nutrient removal via nitrite was much higher when DOW fermentation liquid (FL) was applied rather than VFW FL and acetic acid. The DOW FL contained propionic acid and butyric acid in significant proportions, favouring the nutrient removal via nitrite, while the VFW FL contained mainly acetic acid, which was associated with lower nutrient via nitrite activity. The application of high volumetric nitrogen loading rate (vNLR 1⁄4 0.19e0.21 kgN m3d1) in combination with low dissolved oxygen (DO) concentration
during the aerobic phase, resulted in high and stable nitrite accumulation (NO
eN >97%). These conditions favoured the phosphorus uptake via nitrite, which reached high rates (5.95 ± 2.21 mgP (gVSS h) 1 ), while the aerobic phosphorus removal was much lower. Through mass balances, it was demonstrated that the application of the UASB-SBR process with nutrient removal via nitrite at a decentralized level is a sustainable solution for effective co-treatment of domestic sewage and biowaste
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
Nitritation-denitritation and enhanced via nitrite biological phosphorus removal from the liquid resulting from the anaerobic co-digestion of WAS and OFMSW
No full textThe application of anaerobic digestion (AD) for the co-treatment of waste activated sludge (WAS) and of the organic fraction of municipal solid waste (OFMSW) results in the production of an anaerobic effluent which has particular characteristics and must receive adequate post-treatment for the removal of nutrients. In this work, the short-cut nitrogen removal (SCNR) and denitrifying phosphorus removal via nitrite (DPRN) were studied using a sequencing batch reactor (SBR) for the treatment of the anaerobic supernatant. The long-term stability and behaviour of the biological via-nitrite processes were examined under ordinary and extraordinary operation of the full scale AD plant and the dewatering process. Nutrients removal was tested at low volumetric nitrogen loading rates (vNLR = 0.2 kg m-3d-1), at the vNLR of the system’s nitrifying capacity (0.8 kg m-3d-1) and above its nitrifying capacity (1.1 kg m-3d-1). The feasibility of applying low-cost external carbon sources produced from the pre-treatment of OFMSW and other biowaste was tested; these include fermentation liquid (FL) and liquid drainage (LD) from OFMSW, and FL from cattle manure and maize silage (CM&MS). Complete washout of nitrite oxidizing bacteria (NOB) was accomplished (i.e. 100% NO2-N/NOx-N) at all times, even when the free ammonia (FA) concentration in the reactor was very low (<0.45 mg NH3-N L-1). The type of external carbon source critically impacted on the specific nitrite uptake rate (sNUR) with acetic acid and CM&MS resulting in high specific denitrification rates. DPRN was very effective when all three carbon sources were used and particularly when FL from OFMSW was applied
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
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