1,720,956 research outputs found
Closing the mass-balance of pyroprobe research regarding biomass fast pyrolysis
No full textPresently, the majority of the worlds energy supply is dependent on fossil fuels. As these fuels area limited resource and have significant negative side effects, the way humanity uses these is unsustainable and other sources of energy have to be found. One of these sustainable energy sources is plant-derived biomass. However, biomass cannot be efficiently used in its natural form and needs to be converted to other products through processes such as pyrolysis and gasification. Pyrolysis will be the focus of this thesis, as fast pyrolysis of Miscanthus is studied for the BRISK 2 project at Process & Energy (TU Delft). However, the current setup used for pyrolysis research does not provide a complete mass-closure of the experiments, with only 80% of the total mass accounted for in the char, tar and gaseous yields. In order to improve this closure, four different methods were developed and investigated during this thesis. All of the pyrolysis experiments were performed in a Pyroprobe 5200. The pyrolysis parameters were comparable to fast pyrolysis, with a high heating rate of 600°C/s, a low residence time of 10 s and a Final Pyrolysis Temperature between 600°C and 1000°C. The objective of the first adjustment was to improve the purge flow stability, reduce the amount of blockages in the system and increase the accuracy of the experiments. The flow meter, controlling the purge flow, was replaced with a mass-flow controller and a tube in the setup was simplified and shortened. No further blockages were observed and the total mass-closure improved on average by 7.85 wt% over the temperature range of 600-1000°C, with an increase at every temperature. The second considered element was the homogeneity of the biomass. Two biomass feedstocks were investigated, the first feedstock consisted of inhomogeneous pellets grinded down to a size less than 80μm, while the second type was homogenized biomass of a size of less than 200μm. Both biomass types performed comparably to each other and better than the previous data collected with the setup. At 600°C the inhomogeneous biomass performed better, while at 700°C the homogeneous biomass gave a higher yield. The last two experimental series both focused on gravimetrically measuring the tars collected in the condenser of the setup, which was not gravimetrically measured before. The first of these methods removed the condenser in favour of a direct capture in a quartz trap. This gave a maximum yield increase of 1.14 wt% at 700°C. However, concerns of contaminating the gas mixture with tars arose, therefore this method was not investigated at higher temperatures. In the second technique, the 2ml of isopropanol in the condenser was evaporated from a glass Petri dish, leaving the tars behind. This method was explored over a larger temperature range (600-1000°C), yet only provided a maximum increase of 1.5 wt% at 1000°C, while giving significant fluctuations between experiments. Thus proving that neither of these methods is a suitable way of gravimetrically measuring the condenser.Molecular Science and Technolog
The golden age of wasted TVs: Regaining precious metals and critical raw materials from low and medium grade PCBs within the EU, including a technical case study for FDP TVs and monitors
No full textIn recent decades Europe has been increasing its demand and consumption of electronics. This has in turn resulted in major outflows of waste electronics (WEEE) that are usually not properly dealt with. This is especially the case for low to medium grade printed circuit boards (PCBs) which unlike higher grade electronics such as computers are currently not profitable to recycle. Therefore this thesis, as a part of the Peacoc project, investigated the low energy separation methods roll sorting, magnetic separation and magnetic density separation to concentrate the precious and critical metals found in the components of these discarded PCBs. The resulting secondary material flows were then evaluated on their impact in the EU from a material and energetical perspective.The roll sorter was able to significantly increase the concentrations of the precious metal rich target components (Central processing units, IC chips and transistors, MLCC + Ta capacitors, Small transistors and IC chips and Connectors of plastic with golden pins). The machine sorted the feed into multiple width sizes (< 3.0, 3.0 - 5.0, 5.0 - 7.0 and > 7.0 mm) of which all except > 7.0 were used for further processing, increasing the overall grade from 18.66 to 42.61 wt%. This was further increased by the magnetic separator (lightly and non magnetic fractions for < 3.0 mm and only the non magnetic fraction for 3.0 - 7.0 mm) to 53.69 wt% and magnetic density separation (only for non magnetic 5.0 - 7.0 mm)to 66.23 wt%. Recovery for all target categories was near 100% with the exception of Connectors of plastic with golden pins as these were too large for the roll sorter to sort.The thesis also took a broader approach by employing a dynamic material flow analysis to determine the low to medium grade PCBs and their accompanying precious metal flows in the EU. The expected metal flows were low (∼4%) compared to the EU’s overall demand in 2020 and expected to decrease over the years due to miniaturisation (decreasing size and weight) of the components. Furthermore, only around 36.68 wt% of the maximum precious metal flows were expected to be captured due to low collection rates of WEEE and small loses in separation and metallurgical recovery. Nonetheless, a sizeable fraction of the EU’s electronics sector’s demand (over 10%) could be supplied. These results were confirmed by modelling different future scenarios, a Monte-Carlo uncertainty and sensitivity analysis of the model.Lastly, the thesis explored the topic of critical raw materials (CRMs) and the direct energy requirements of Peacoc’s recovery system. It was found that beryllium, antimony, platinum and palladium were the only CRMs that had any significant potential to supply the EU (9.13% for beryllium, 1.58% for antimony,1.32% for platinum and 4.02% for palladium). If only looking at the electronics sector this was also the case for cobalt and vanadium. The newly captured secondary precious metals were shown to require significantly less energy to produce, around an order of magnitude, compared to primary production but were similar to other recycling pathways. Furthermore, the majority of energy was required during metallurgical recovery showing a potential for further mechanical concentration during separation.In conclusion it can be stated that the separation technologies (roll sorting, magnetic separation and magnetic density separation) are effective methods for separating the components of low to medium grade PCBs. However, their impact on the circularity and energetical footprint of the whole EU are expected to be small.PeacocIndustrial Ecolog
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
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