1,720,960 research outputs found
Laboratory investigation of frost susceptibility of crushed rock aggregates and field assessment of frost heave and frost depth
Full text linkIn Nordic countries that experience seasonal frost, understanding how it affects the service life of linear transport infrastructures such as roads and railways is essential. Frost action both regroup frost heave and thaw weakening processes. This research focuses on frost heave, which occurs when three conditions are met: freezing temperature, water availability and frost-susceptible materials. Frost susceptibility is therefore defined as the ability of an unbound granular material (natural soil or crushed rock aggregate) to form ice lenses due to cryosuction, which is the suction of water to the frost front. Frost heave in a frostsusceptible material lifts the layers above the freezing front. Many kinds of damage are attributable to frost heave, such as cracks in and unevenness of the road surface, making it uncomfortable and even dangerous for road users. Frost heave and subsequent thawing can significantly reduce the service life of roads and are accompanied by high associated maintenance and reparation costs. Knowledge of the frost susceptibility of the materials comprising the different layers of transport infrastructure is therefore crucial to optimal frost design.
This research mainly aimed to characterize the frost susceptibility of crushed rock aggregates. Laboratory experiments using a multi-ring frost cell were carried out to estimate the segregation potential of the 0-4 mm fraction of crushed rock aggregates. Twenty-four tests performed on nine different rock types found that crushed rock aggregates with a fines content of <63 μm between 11.6% to 25.5% are highly frost susceptible. The study found poor correlation between <63 μm fines content and segregation potential. The latter was used to characterize the frost susceptibility of the different crushed rock aggregates primarily for its capacity to estimate frost heave magnitude easily. The use of a grain size criterion, as presently used in Norway, seems to be efficient for dividing non-frost-susceptible from frost-susceptible aggregates, but does not allow estimation of crushed rock aggregates’ segregation potential with a good degree of confidence.
As frost heave tests require a costly laboratory setup and specialist personnel, the segregation potentials of crushed rock materials were estimated using material index properties such as initial water content, liquid limit, mean particle size of the fine fraction and specific surface area of the fine fraction. This method is used by the Quebec Ministry of Transportation for soils, and the goal here was to assess the suitability of the methodology for use with crushed rock aggregates. It was found that estimation from material indexes gave segregation potential results within a range of ±15% compared to those obtained from frost heave tests. There was a direct correlation between the specific surface area of the fine fraction of a crushed rock aggregate and its segregation potential, from which an equation was developed. The study showed that the crushing phase had an effect on the frost susceptibility of the tested crushed rocks. Aggregates are more frost susceptible after the first crushing stage than after the third or fourth crushing stages. The hypothesis that the fine fraction is enriched by weak minerals at the first crushing could explain this behaviour, but further research is necessary before this theory can be presented with confidence.
The design was optimized by modelling three road sections with different frost protection layers using the SSR model and the I3C ME software. The fully-instrumented test site is situated in the Røros municipality where harsh winters are the norm, with the freezing index of an average winter equal to that of regions such as Oslo, Trondheim, Narvik, Tromsø etc. It was found that the SSR model is suitable for both frost penetration and frost heave estimation for thick (2.05 meters) layered road structures. The SSR also permitted the back-calculation of key parameters such as dry density, moisture content and segregation potential, making it useful for assessing existing infrastructure parameters. Using a segregation potential function, i.e. segregation potential according to time, was found to produce optimal frost heave estimations in a transient thermal regime
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
Frost protection of roads
No full textTelehiv er forskyvelsen av jordoverflate som forårsakes av dannelsen av islinser i bære - og forsterkningslagene. Når frosten når telefarlig undergrunn vil vann bli sugd opp nedenfra ved hjelp av kapillært poresug gjennom frostsikringslaget hvis dette ikke er tilstrekkelig isolert. Vannet vil så fryse og danne horisontale islinser som kan bli flere centimere tykke. Denne utvidelsen er det ikke plass til og dermed oppstår forskyvelsen av overflaten. Ujevnhetene i vegbanen fører til forringet kjørekomfort og økte kostnader i form av større slitasje på bil og veg.
Mangelen på naturlig tilslag har ført til at Norge nå bruker sprengstein som bygningsmasteriale. I Norge brukes telefarlighetklassifiseringssystemet til Statens Vegvesen og inndeler telefarlighet etter andelen finstoff, dvs. materiale med diameter < 0,065 mm. Lokale pukkverk sitter på store mengder sprengstein som ikke kan utnyttes fordi de klassifiseres som telefarlige. Dette fører til store kostnader.
En mulig måte å benytte sprengstein i frostsikringslaget er ved hjelp av tilsetningsstoffer for å redusere frostfølsomheten. Frosthevetester av ubehandlede - og behandlede prøver fra flere pukkverk ble utført ved NTNU. Tilsetningsstoffene som ble testet var Dustex og en blanding av Terrasil og Zycobond. Vertikalt hiv, frostdybde og verdier for segregeringspotensialet ble beregnet for hver av prøvene
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
Frost protection of roads
Full text linkTelehiv er forskyvelsen av jordoverflate som forårsakes av dannelsen av islinser i bære - og forsterkningslagene. Når frosten når telefarlig undergrunn vil vann bli sugd opp nedenfra ved hjelp av kapillært poresug gjennom frostsikringslaget hvis dette ikke er tilstrekkelig isolert. Vannet vil så fryse og danne horisontale islinser som kan bli flere centimere tykke. Denne utvidelsen er det ikke plass til og dermed oppstår forskyvelsen av overflaten. Ujevnhetene i vegbanen fører til forringet kjørekomfort og økte kostnader i form av større slitasje på bil og veg.
Mangelen på naturlig tilslag har ført til at Norge nå bruker sprengstein som bygningsmasteriale. I Norge brukes telefarlighetklassifiseringssystemet til Statens Vegvesen og inndeler telefarlighet etter andelen finstoff, dvs. materiale med diameter < 0,065 mm. Lokale pukkverk sitter på store mengder sprengstein som ikke kan utnyttes fordi de klassifiseres som telefarlige. Dette fører til store kostnader.
En mulig måte å benytte sprengstein i frostsikringslaget er ved hjelp av tilsetningsstoffer for å redusere frostfølsomheten. Frosthevetester av ubehandlede - og behandlede prøver fra flere pukkverk ble utført ved NTNU. Tilsetningsstoffene som ble testet var Dustex og en blanding av Terrasil og Zycobond. Vertikalt hiv, frostdybde og verdier for segregeringspotensialet ble beregnet for hver av prøvene.Frost heave is cracking of the road surface due to formation of ice lenses in base and subbase layers. Water enters these two layers through the subgrade layer if this is not sufficiently isolated. Because of capillary suction, the amount of water migrating upwards is related to the amount of fines in the soil.
Scarcity of natural aggregates are forcing countries to use crushed rock aggregates to construct roads to ensure layers of appropriate specifications. Local quarries are left with a large amount of crushed rock aggregates that do not fulfil criteria set by the Norwegian Public Road Administration regarding the content of fines (0-4mm). The problem of storage, disposed and lack of opportunity cost is large for local quarries.
A possible way to utilise crushed rock aggregates in a frost protection layer is by using additives to reduce the frost-susceptibility. Frost heave tests of untreated - and treated - samples from several quarries were performed at NTNU. Additives tested were Dustex and a mixture of Terrasil and Zycobond. Frost heave, frost penetration depth and segregation potential values were calculated for each of the samples
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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