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Determination of the minimum ignition energy of wood dust
No full textPrašne eksplozije se pojavljajo v delovnih okoljih, kjer je v delovnih procesih prisoten gorljiv prah. Poleg prisotnosti gorljivega prahu mora biti za nastanek prašne eksplozije izpolnjenih pet dejavnikov, ki bodo natančneje predstavljeni v nadaljevanju. Na začetek in potek eksplozije pa vplivajo številne spremenljivke.
V sklopu diplomskega dela so predstavljene fizikalne lastnosti in eksplozijski parametri treh vrst lesnih prahov: bukov, smrekov in macesnov. Vzorcem smo določili vsebnost vlage s termično analizo in specifično površino po BET metodi. Vzorce lesnega prahu smo presejali in tako dobili različne velikostne frakcije določene vrste lesnega prahu. Prvotnim vzorcem in izbranim velikostnim frakcijam smo določili velikosti in porazdelitev velikosti delcev. Določili smo minimalno vžigno energijo vzorcem lesnega prahu. Meritve so bile izvedene za vse tri prvotne vzorce lesnega prahu, ter za tri velikostne frakcije (80-100 μm, 100-125 μm in 125-160 μm) za bukov in smrekov lesni prah.
Po končanih meritvah, smo dobili območja minimalne vžigne energije. Območje v katerem se vname macesnov prah je med 600 in 1000 mJ. Za prvotni smrekov prah je območje vžiga med 10 in 30 mJ, za bukov prah pa med 30 in 100 mJ. Za smrekov prah je območje za velikostno frakcijo 125-160 μm in 80-100 μm med 30 in 100 mJ, za velikostno frakcijo 100-125 μm pa med 100 in 300 mJ. Za bukov prah smo izvedli meritve za enake velikostne frakcije, vendar je do vžiga prišlo le pri frakciji 125-160 μm, pri ostalih dveh pa ne. Eksplozijsko območje za to frakcijo je med 300 in 600 mJ. Rezultate meritev sem primerjala z vrednostmi iz literature. Za macesnov prah v literaturi nisem našla nobenih vrednosti. Za smrekov in bukov prah je vrednost MVE iz literature nižja od naše izmerjene vrednosti.
Glede na rezultate določitev območja minimalne vžigne energije lesnih prahov ugotavljam, da najmanjšo verjetnost za nastanek eksplozije predstavlja macesnov lesni prah. Najbolj nevaren pa je lesni prah smreke, saj je do vžiga prišlo pri vseh treh frakcijah in prvotnem vzorcu. Poleg tega pa ima smrekov prah tudi najnižje vrednosti energije potrebne za vžig.Dust explosions occur in work environments where combustible dust is present in work processes. In addition to the presence of combustible dust, five factors must be met for a dust explosion to occur, which will be presented below. The beginning and course of the explosion are influenced by many variables.
The thesis presents the physical properties and explosion parameters of three types of wood powders: beech, spruce and larch. The moisture content of the samples was determined by thermal analysis and specific surface area by the BET method. Wood dust samples were sieved to obtain different size fractions of a certain type of wood dust. Particle sizes and particle size distributions were determined from the original samples and selected size fractions. We determined the minimum ignition energy of the wood dust samples. Measurements were performed for all three original wood dust samples, and for the three size fractions (80-100 μm, 100-125 μm and 125-160 μm) for beech and spruce wood dust.
After the measurements were completed, we obtained areas of minimum ignition energy. The area in which larch dust ignites is between 600 and 1000 mJ. For the original spruce dust, the ignition range is between 10 and 30 mJ, and for beech dust between 30 and 100 mJ. For spruce dust, the range for the size fraction 125-160 μm and 80-100 μm is between 30 and 100 mJ, and for the size fraction 100-125 μm between 100 and 300 mJ. For beech powder, measurements were performed for the same size fractions, but ignition occurred only in the fraction 125-160 μm, and not in the other two. The explosion range for this fraction is between 300 and 600 mJ. I compared the results of the measurements with the values from the literature. I found no literature values for larch powder. For spruce and beech dust, the MVE value from the literature is lower than our measured values.
Based on the results of determining the range of minimum ignition energy of wood powders, I find that the lowest probability of an explosion is larch wood dust. The most dangerous, however, is spruce wood dust, as ignition occurred in all three fractions and the original sample. In addition, spruce dust also has the lowest values of energy required for ignition
Determination of material characteristics and explosion parameters of cellulose and particle board dust
No full textGlavna tema magistrskega dela so prašne eksplozije prahu ivernih plošč in prahu celuloze. Prašna eksplozija je nevarni pojav, ki lahko povzroči hude poškodbe in škodo za ljudi, opremo in okolico. Razumevanje tega fenomena je ključnega pomena za preprečevanje prašnih eksplozij.
V prvem delu je predstavljena teoretična osnova prašnih eksplozij in sicer zgorevanje, pogoji za nastanek prašne eksplozije in glavni dejavniki, ki vplivajo na potek eksplozije, npr. oblika in velikost delcev, vsebnost vlage, kemijska sestava prahu, koncentracija prahu, koncentracija oksidanta ter vrtinčenje. Predstavljeni so tudi eksplozijski parametri, ki opisujejo občutljivost za nastanek eksplozije ter silovitost eksplozije. Opisane so posledice eksplozije v primeru, da do te kljub sprejetim ukrepom vseeno pride ter ukrepi s katerimi lahko nastanek eksplozije preprečimo ali vsaj ublažimo njene posledice.
V sklopu eksperimentalnega dela smo za prah celuloze in prah ivernih plošč izvedli meritve snovnih karakteristik in eksplozijskih parametrov. Pred pričetkom meritev smo s sejalno analizo za vzorec prahu ivernih plošč pridobili posamezne velikostne frakcije. Nato smo izbranim vzorcem določili velikost in porazdelitev velikosti delcev, specifično površino, vsebnost vlage s termično analizo in vsebnost elementov ogljika, vodika in dušika z elementno analizo. Po določitvi snovnih karakteristik smo izvedli še meritve eksplozijski parametrov in sicer minimalne vžigne energije, minimalne eksplozijske koncentracije, maksimalnega eksplozijskega tlaka in maksimalno hitrost porasta tlaka ter izračunali indeks deflagracije.
V zadnjem delu sledi potrditev ali ovržba predpostavljenih hipotez, ki so predstavljene v namenu magistrskega dela ter primerjava meritev s podatki iz literature.The main topic of the master’s thesis is dust explosions of particleboard dust and cellulose dust. A dust explosion is a dangerous phenomenon that can cause serious injuries and damage to people, equipment and the environment. Understanding this phenomenon is critical for preventing dust explosions.
In the first part, the theoretical basis of dust explosions is presented, namely combustion, the conditions for the formation of a dust explosion and the main factors that influence the course of the explosion itself, e.g. particle shape and size, moisture content, chemical composition, dust concentration, oxidant concentration and turbulence. The explosion parameters are also presented, which describe the sensitivity and the intensity of the explosion. The consequences of an explosion if it occurs despite the measures taken are described, as well as the measures that can be taken to prevent the occurrence of an explosion or at least mitigate its consequences.
As part of the experimental work, we carried out measurements of material characteristics and explosion parameters for cellulose dust and particleboard dust. Before starting the measurements, individual fraction sizes were obtained using a sieving analysis for a particleboard dust sample. We then determined the size and size distribution of the selected samples, the specific surface area, the moisture content with thermal analysis and the content of the elements carbon, hydrogen and nitrogen with elemental analysis. After determining the material characteristics, we also carried out measurements of the explosion parameters - minimum ignition energy, minimum explosion concentration, maximum explosion pressure, maximum speed of pressure rise and calculated the deflagration index.
In the last part of the master\u27s thesis, the confirmation or refutation of the assumed hypotheses follows and also the comparison of measurements with data from the literature
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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