1,722,028 research outputs found
Anaerobic digestion of source-segregated domestic food waste
No full textAnaerobic digestion (AD) is an attractive waste treatment process in which both pollution control and energy recovery can be achieved. Source-segregated domestic food waste (FW) has a high organic content on a dry weight basis and is rich in lipids and proteins, indicating the potential for a good biogas yield with high methane content. Process instability, however, has often been reported in food waste digesters, which was mainly manifested by the accumulation of volatile fatty acids (VFA) and reduction of specific methane production. Trace element (TE) supplementation has been proved to be an effective way to rectify this problem and has been applied to industrial AD plants. This practice, however, was usually characterised by a trial-and-error approach due to the lack of a clear understanding of the impact of TEs on AD under different process conditions. The aim of this study was therefore to optimise TE dosing strategies for FW digestion at different loading rates, with particular attention to the role of cobalt (Co) and selenium (Se).The limiting concentrations of Co and Se were studied in long-term continuously stirred tank reactor (CSTR)-type digester experiments at organic loading rates (OLR) from 1.8 to 5 kg volatile solids (VS) m-3 d-1. In a digester operated at OLR 1.8 kg VS m-3 d-1 without TE addition, dosing of Co at a strength of 1 mg Co kg-1 fresh matter was effective to stimulate the complete degradation of accumulated VFA. Around 2500 mg L-1 VFA built up, however, after OLR increased to 2.5 kg VS m-3 d-1; then dropped slightly by addition of Se at a strength of 0.05 mg Se kg-1 fresh matter. After stepwise increases in Se concentration to 0.2 mg kg-1, VFA reduced to less than 1000 mg L-1. In another 2 digesters, at OLR 3 and 4 kg VS m-3 d-1 respectively, TE washing-out was introduced for determination of the limiting Co concentration. All TE supplementation was ceased in these 2 digesters for around 300 days with the exception of continuous addition of 0.2 mg kg-1 of Se. VFA accumulation up to 30000 mg L-1 occurred in one digester immediately after the OLR increased from 4 to 5 kg VS m-3 d-1 and later up to 22500 mg L-1 in the other digester when OLR increased from 3 to 4 kg VS m-3 d-1. By gradually increasing Co concentration in both digesters to 0.3~0.5 mg kg-1, VFA started to be consumed. At the end of test, the recovered digester with OLR 5 kg VS m-3 d-1 was running stably with 0.2 mg kg-1 Se and 0.3~0.5 mg kg-1 Co addition, with a pH of 7.8, IA/PA ratio 0.4, specific methane production (SMP) 0.47 standard temperature and pressure (STP) m3 CH4 kg-1 VS d-1, volumetric methane production (VMP) 2.37 STP m3 CH4 m-3 d-1, and VFA concentration less than 500 mg L-1. To further understand the effect of trace elements on VFA production, short-term trials were carried out to assess their function in VFA production. The results indicated that with accumulated VFA, supplementation of trace elements stimulated VFA production to a greater extent than VFA consumption.Effect of organic loading rate on TE dosing strategy and digester performance was studied in 5 digesters, all of which had stable operation but different trace element addition histories. One pair digesters was run as control at OLR 5 kg VS m-3 d-1 over the course of the experiment, another pair operated with a gradual loading increase to 6, 7, 8 and 9 kg VS m-3 d-1. A SMP of 0.46±0.02 STP m3 CH4 kg-1 VS d-1 at OLR 8 kg VS m-3 d-1 was achieved. Volatile solids destruction (VSD) rates were similar between OLR 5 and 8 kg VS m-3 d-1, at approximately 0.74~0.75, but reduced to 0.71~0.72 at OLR 9 kg VS m-3 d-1. Residual methane production (RBP) test results showed that biogas production of digestate from OLR 5 and 7 kg VS m-3 d-1 were similar, whereas digestate from OLR 9 kg VS m-3 d-1 generated more biogas than OLR 5 kg VS m-3 d-1, indicating lower conversion efficiency was achieved at OLR 9 kg VS m-3 d-1. Nitrogen mass balance equations were developed to distinguish nitrogen distribution in digesters. These showed that microbial biomass density increased along with OLR increase, which in turn requires an increase in TE addition. The specific rate of biomass increase at OLR 9 kg VS m-3 d-1, however, was lower than at 8 kg VS m-3 d-1, reflecting the decrease in specific methane production and VSD rate. The results indicate that FW digester was able to operate at OLR 8 kg VS m-3 d-1, without loss of performance when compared with OLR 5 kg VS m-3 d-1. Loading 9 kg VS m-3 d-1 was regarded as overloaded due to the lower hydrolysis and acidification efficiency. The fifth digester, in which the same TE dosing was applied, was operated with random loading: a daily load between 2.5~7.5 kg VS m-3 d-1 was randomly introduced while weekly average OLR was maintained at 5 kg VS m-3 d-1. Stable performance was observed in this digester with 2.27 STP m3 CH4 m-3 d-1 of 30-day rolling average VMP and 76% of VSD rate, and VFA concentrations less than 500 mg L-1.Further research on essential TE supplementation for stable FW digestion at high loading was carried out. All TE additions were ceased except 0.3 mg kg-1 of Co and 0.2 mg kg-1 of Se, in two pairs of digesters at loading 5 and 8 kg VS m-3 d-1, respectively. VFA accumulation occurred in digesters at the higher loading, which finally failed. VFA fluctuated around 4000 mg L-1 in digesters at OLR 5 kg VS m-3 d-1, until the rest of trace elements in a full 11 trace elements recipe were reintroduced, when VFA degraded quickly to below 1000 mg L-1.The research provided new insight on optimising essential TE supplementation to FW digestion, especially at moderate and high loading rates, to ensure stable and high productive biogas production.<br/
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
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
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
Dataset for 'Comparison of variable and constant loading for mesophilic food waste digestion in a long-term experiment'
No full textThis dataset supports the publication: Song H, Zhang Y, Kusch-Brandt S and Banks CJ (2020) Comparison of variable and constant loading for mesophilic food waste digestion in a long-term experiment in Energies.
This dataset includes the calculation for Figure 2. 'VFA profiles', Figure 3. 'Operational parameters' and Figure 4. '28-days rolling average volumetric methane production'. </span
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
