1,720,959 research outputs found
Design and modelling of underground decay heat removal system for a district heating reactor
Full text linkDecay heat in fission reactors is a main concern from a safety perspective. Adequate removal of decay heat should be maintained under all circumstances to ensure reactor operability within safety limits and mitigating any undesirable consequences. This could be achieved by utilising passive safety which increases the inherent safety characteristics and reliability of the design.
The study carried out in this report investigates the feasibility of a proposed passive decay heat removal system for a 24 MWth nominal power underground district heating conceptual design. The proposed loop utilises air and steam mixture as a working fluid and relies on natural circulation to eject the heat from the containment to the ground as a buffer.
A Comprehensive review of condensation theory in horizontal tubes is provided in the literature review with a focus on the effect of non-condensable gas (NCG) on heat transfer. An analytical study is then performed using a MATLAB script substantiated with relevant correlations to determine the geometrical and operational parameters of the system. The analysis is initially performed for a pure steam case as a baseline then the effect of NCG is considered in a further updated model. This was followed by a numerical simulation using thermal hydraulic code system (TRACE) to study the overall behaviour of the loop. Both analytical and numerical results are compared.
The work presented in this report shows that removal of decay heat up to one month following shutdown is feasible with the proposed decay heat removal system. The presence of NCG in the loop has little to no effect on the condensation process and does not compromise the overall performance of the system significantly
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
Oblikovanje in modeliranje podzemnega sistema za odstranjevanje gnilobe toplote za reaktor za daljinsko ogrevanje
No full textDecay heat in fission reactors is a main concern from a safety perspective. Adequate removal of decay heat should be maintained under all circumstances to ensure reactor operability within safety limits and mitigating any undesirable consequences. This could be achieved by utilising passive safety which increases the inherent safety characteristics and reliability of the design.
The study carried out in this report investigates the feasibility of a passive decay heat removal system for a 24 MWth nominal power underground district heating conceptual design. The loop utilises air and steam mixture as a working fluid and relies on natural circulation to eject heat from the containment to the ground as a buffer.
A Comprehensive review of condensation theory in horizontal tubes is provided in the literature review with a focus on the effect of non-condensable gas (NCG) on heat transfer. An analytical study is then performed using a MATLAB script substantiated with relevant correlations to determine the geometrical and operational parameters of the system. The analysis is initially performed for a pure steam case as a baseline then the effect of NCG is considered in a further updated model. This was followed by a numerical simulation using thermal hydraulic code system (TRACE) to study the overall behaviour of the loop. Both analytical and numerical results are compared.
The work presented in this report shows that removal of decay heat up to one month following shutdown is feasible with the proposed decay heat removal system. The presence of NCG in the loop has little to no effect on the condensation process and does not compromise the overall performance of the system significantly.V današnjem svetu je jedrska energija uveljavljena kot čist in zanesljiv vir energije v omrežjih številnih držav. V luči doseganja ničelnih izpustov CO2 se raziskave o uporabi jedrske energije razvijajo v različne smeri. Daljinsko ogrevanje z jedrsko energijo je obetavno področje, o katerem razmišljajo zlasti številne severne države. Na Finski Lappeenranta University of Technology je to sprožilo razvoj eksperimentalnega reaktorja za daljinsko ogrevanje LUTHER.
LUTHER je razširljiv lahkovodni reaktor z nizko gostoto moči. Običajno vodo pri relativno nizkem tlaku in temperaturi uporablja kot moderator in hladilno tekočino. Del razvoja reaktorja predstavljajo varnostni sistemi. Študija, izvedena v tem magistrskem delu, raziskuje izvedljivost pasivnega sistema za odvajanje zaostale toplote za podzemno izvedbo reaktorja LUTHER z nazivno močjo 24 MWth. Zanka uporablja mešanico zraka, vode in vodne pare kot delovno tekočino in se zanaša na naravno konvekcijo za odvajanje toplote iz zadrževalnega hrama v zemljo v okolici elektrarne.
V prvem poglavju je predstavljen obsežen pregled literature, ki opisuje zasnove hlajenja zadrževalnih hramov večine sodobnih jedrskih elektrarn. Sledi pregled študij, ki obravnavajo hlajenje s kondenzacijo pare v dvofaznem toku vode, vodne pare in zraka.
V drugem poglavju sta predstavljena dva analitična modela, ki sem jih razvil za izvedbo analize. Temeljita na ustreznih korelacijah za določitev geometrijskih in obratovalnih parametrov sistema. Analiza se izvaja z uporabo programa MATLAB. Začetni izračuni so izvedeni za primer čiste pare brez prisotnosti nekondenzibilnih plinov, v našem primeru zraka. Učinek zraka, ki je prisoten v zadrževalnem hramu, je upoštevan v posodobljenem modelu prenosa toplote s kondenzacijo z uporabo degradacijskega faktorja (Lee & Kim, 2011), ki upošteva poslabšanje prenosa toplote ob prisotnosti zraka.
V tretjem in četrtem poglavju je opisana numerična študija z uporabo termično-hidravličnega računalniškega programa TRACE. Gre za sistemski računalniški program razvit v ZDA za termo-hidravlične analize vodno hlajenih jedrskih reaktorjev. Simulacije sem sprva izvajal za delno dolžino ene same hladilne cevi zakopane v tla, da sem preizkusil učinek različnih
parametrov na prenos toplote: tlaka, naklona cevi, materiala tal in količine zraka v zanki. Rezultati, pridobljene s preskusom z enojno cevjo, sem preučil in jih uporabil pri razvoju celotne zanke, ki bo vsebovala snop takšnih cevi in bo dovolj zmogljiva, da bo iz zadrževalnega hrama odvajala vso zaostalo toploto ki se sprošča zaradi radioaktivnih razpadov v ustavljenem jedrskem reaktorju.
V 5. poglavju sem predstavil in primerjal rezultate analitičnih in numeričnih študij in z rezultati pojasnil delovanje sistema in njegove omejitve. Ocenil sem tudi negotovosti rezultatov. Kvalitativno analitični in numerični rezultati kažejo podobne trend, a je med obema modeloma precejšnja kvantitativna razlika. Na podlagi dobljenih rezultatov ta študija dokazuje izvedljivost predhodne zasnove podzemnega sistema za odvajanje zakasnele toplote. Kot je razvidno iz spodnje slike, je hladilna zanka varnostnega sistema sposobna pasivno odvajati dovolj veliko količino zakasnele toplote daljše obdobja po zaustavitvi reaktorja. Prisotnost zraka v zanki ima le malo vpliva na proces kondenzacije in ne poslabša bistveno celotne učinkovitosti sistema. Pred dokončno potrditvijo zasnove varnostnega sistema bo potrebno dele računalniškega programa TRACE preveriti z dodatnimi eksperimenti. Na koncu pa bo za varnostne analize potrebno ponoviti obsežne numerične študije različnih možnih dogodkov
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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