1,720,961 research outputs found
Investigating the clean production and storage of hydrogen from conventional and non-conventional resources via pyrolysis and adsorption
No full textThe world energy vision is centred on transitioning from fossil fuels to green and renewable energy resources such as biomass, wind, solar, nuclear, and hydrogen. Among these potential energy sources, hydrogen has received great attention from researchers due to its physiochemical properties that enable it to be utilized in many industries. Biomass is also considered a green energy source and is readily available to be converted into clean energy via different conversion routes. Pyrolysis is considered a clean method to convert biomass into renewable energy - in particular H2. Thus, this study systematically investigated the clean production of H2 rich biogas from both renewable and non-renewable resources via pyrolysis. The effect of pyrolysis parameters like temperature, pressure and H2O ratio on known H2 production secondary reactions were analysed and optimum conditions for production were determined. However, H2 is a low-density gas and cannot be easily compressed, making the process of storing it difficult and expensive. Thus, a H2 economy cannot be fully established if drawbacks in H2 storage are not remedied. Therefore, this study also investigated the feasibility of non-conventional resources materials such as waste biomass, biochar, waste plastics and organic metal frameworks to adsorb and store H2. The effect of materials surface textural properties, adsorption pressure and temperature were studied. In overall, the major part of this work is converting waste materials into energy (H2) and porous storage materials for H2. An in house built fixed bed pyrolysis system was used for all the pyrolysis reactions. Materials surface characterization was performed using Fourier-Transformed infrared spectroscope (FTIR), X-ray powder diffraction (XRD), Brunauer-Emmet-Teller (BET), Scanning Electron Microscopy (SEM), and Transmission electron microscopy (TEM). The thermal degradation behaviour of the samples was done by a Thermogravimetric Analyser (TGA) analysis. Adsorption experiments were conducted using an automated Sievert’s PCT Pro instrument. It is not certain if renewable energy sources can cover the energy demand and supply, hence we still need energy from fossil fuels and we also need to identify other potential energy sources that are abundantly found everywhere and use clean technologies to convert them into energy. Thus, kerogen which is the most abundant type of organic matter with a high hydrogen content was thermally converted to H2 via pyrolysis. Interestingly, H2 and CH4 were the main gas produced, with H2 having the highest concentration in all the temperatures studied. CO and CO2 emission was only in trace amounts, and the process can be considered very environmentally friendly. H2 production reached 81.28 Vol.%, 79.49 Vol.%, and 68.82 Vol.% at 350 ⁰C, 600 ⁰C, and 800 ⁰C.
Biomass from waste wheat straw was successively converted into H2 concentrated gas with very low greenhouse gas emission. Elevated temperatures and high biomass-water mass ratios were necessary to converted the biomass waste into H2 rich biogas, while simultaneously minimizing greenhouse gas production. Maximum H2 yield reached 92.53 Vol.% (equivalent to 224.14 gH2/kg.WS) at 1000 ⁰C and 1:4 WS:H2O ratio. The impact of pressure and temperature (500-900 ⁰C, and 1.01-30 bar range) on the selectivity of H2 rich biogas production was also investigated and both temperature and pressure, influenced H2 formation. Increasing temperature and pressure increased H2 production (which peaked to 86.07 Vol.% at 800 ⁰C and 30 bar).
The feasibility of pyrolysis derived biochar to store H2 at atmospheric and cryogenic temperatures, i.e. 30 ⁰C and -196.0 ⁰C and under vacuum to 70 bar pressure) was investigated. The maximum H2 adsorption capacity at ambient temperature was 2.50 mol/kg at 66.33 bar (for 900 ℃ biochar) which significantly increased to 15.29 mol/kg at cryogenic temperature at 46.21 bar. Microplastic waste (MicroPE)– a significant environmental pollutant – was tested for H2 storage. H2 adsorption capacity of MicroPE increased with increasing the adsorption pressure (from 0.06 mol/kg at 17.21 bar to 0.20 mol/kg at 68.11 bar for raw MicroPE). MicroPE 4 activated with aqueous NaOH significantly changed H2 adsorption under the same operating conditions. H2 adsorption increased to 0.50 mol/kg at 68.11 bar when MicroPE was treated with 0.002 mol/L aqueous NaOH.
The physicochemical properties of Metal Organic Frameworks (MOFs) make them suitable for H2 storage. Therefore, the relationship between adsorption temperature and pressure with the MOFs surface textural properties towards H2 storage was studied. Two Iron-based MOFs (12- MIL-88B(Fe), 24-MIL-88B(Fe) with different surface textural properties were synthesized and tested for H2 adsorption at 30 ˚C, 0 ˚C, -78.5 ˚C, and -196 ºC and from vacuum pressure to 55 bar. Results showed that at 30 ˚C and 0 ˚C adsorption temperature, pore volume, surface area, and adsorption pressure greatly influenced H2 adsorption performance, while under low temperature (-78.5 ˚C) and cryogenic temperature (-196 ˚C) the Fe-MOF with the wider pore size adsorbed more H2 molecules. While pressure continued to positively promote the amount of H2 adsorption at all temperatures studied
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
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
A progress insight of the formation of hydrogen rich syngas from coal gasification
Get PDFThis review paper aims to explore the research progress in the formation of hydrogen rich gas from different innovative coal gasification parameters. Promotion effects of parameters such as pressure, temperature, catalyst, coal type, reactor setup, and gasification agents (H2O, O2, supercritical water) were extensively analysed. The formation of hydrogen gas through coal gasification was sub-divided into H2 production from fixed bed gasification system, fluidized bed system, and entrained flow system. The advantages of coal and biomass co-gasification towards clean energy formation was also reviewed. Co-gasification and elevated temperatures, pressures, and steam-carbon ratios were reported to positively influence the yields of H2 gas by facilitating steam reforming and water gas shift reactions. The presence of different catalyst and sorbents in the gasification reaction systems was also noticed to enhance the concentration of hydrogen in the gaseous products. Production of hydrogen rich syngas from fixed bed and fluidized bed gasifiers was assessed, and both methods were found to favour the formation of hydrogen gas. The polygeneration of hydrogen gas, electricity and carbon dioxide capture was discovered to be feasible via coal gasification techniques
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