1,721,044 research outputs found
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
Temperature effect on the rock salt instant strength characteristics
No full textThe mechanical behavior of rock salt has been studied for many decades. Early engineering studies were driven largely by the need to design safe salt mines. In recent times more of the study is concerned to understand the long term behavior of the rock salt to develop and assess the safety of rock salt deposits for the storage of radio active waste. The physical and mechanical characteristics of salt are evidenced in its compact texture, low porosity, low permeability and strong rheological properties (creep behavior). These properties are however necessary for stability analysis and the design of engineering structures in salt mines. Long term effect of the temperature on rock salt mechanical behavior has been documented by various researchers. Temperature also has pronounced effect on short term behavior like instant strength of the rock salt. Generally the trend is that as the temperature increases the instant strength decreases. For the stability of structures like solution-mined caverns, dry salt mines, storage and disposal caverns and boreholes used in the exploration and production of oil and gas comprehensive study of the instant strength of the rock salt is also vital. The objective of this research was to study the temperature effect on the instant strength of the rock salt obtained from Polkowice - Sieroszowice mine in the Lower Selicia. After laboratory tests using uniaxial compressive strength test method, it was observed that the at the given range of temperature applied in the test (10 degree C to 80 degree C) the rock salt instant strength does not show any correlation with the temperature. In other words the instant strength of the rock does not decrease as temperature increase. This kind of unanticipated behavior towards the temperature in terms of strength which is rare for the rock salt could be due to the reason that the range of temperature used in the test was not sufficient for the rock salt to show any alteration in its strength value. Since there was no significant effect of given temperature range on the strength values of the rock salt, classical failure criterion like Mohr-Coulomb criterion was considered as the suitable criterion to justify the strength changes on the rock salt samples. On the other hand density emerges out as a crucial factor that influences the instant strength of the rock salt. Higher uniaxial compressive strength values can be observed for the samples having higher density. This research work is useful to understand the mechanical behavior of the rock salt which behaves in a complex manner when there are lots of factors involved like geology, temperature, density, loading history, maturity of the crystals etc. are involved. It is therefore deemed necessary that more through studying and testing is required.Geo-engineeringApplied Earth SciencesCivil Engineering and Geoscience
Stability analysis of Embankments located within A-8 interstate motorway Wroc?aw by-pass
No full textRoads support our daily life, and play crucial role in supporting the infrastructure for economic activities. However, road disaster can be caused by different natural conditions of slope failures such as rainfall, steep topography, brittle geology, etc. Road disaster occurrences do not only cause the primary disaster from the infrastructure point of view; but also the secondary disaster, hindrance to the society and the economic activity by traffic stops. In order to prevent or mitigate such road disasters caused by diverse reasons; measures should be taken in every phases of road engineering practices, usually mainly thorough investigation about the surface geology, the subsurface conditions of the foundation and the careful testing of the construction materials principally. Hence detailed investigation about the site is compulsory before commencing the design and construction phases. In addition, post construction phases mainly regular monitoring and maintenance must be undertaken to give the intended service of the highway. Limit equilibrium method is one of the most widely used stability analysis in practice due to its reliability for most practical cases. Its simplified approach can be used in the preliminary assessment only while more complex analysis that gives more accurate results can be carried out with computer programs. This research presents results of stability analysis of A-8 motorway Wroclaw bypass on selected embankments under construction founded on heterogeneous soft soil layers. Different methods of limit equilibrium analysis adopted in computer analysis program SLIDE 2D was used to calculate the Factor of Safety of each embankment. The discussion was based on the results of the computation carried out for cross-sections of A-8 motorway characterized by variability of height and reinforcement conditions. The limit equilibrium method which satisfies both force and moment equilibrium give better prediction on the stability of the slope. In addition to that the method whose assumption mimics the slope condition is preferred. The assessment was executed by referring to the slope stability requirement by Polish regulations.Geo-EngineeringApplied Earth SciencesCivil Engineering and Geoscience
Processing of spinel-bearing compounds for zinc extraction
No full textThis thesis studies the zinc extraction from spinels through hydro and pyrometallurgical processing. Two zinc-bearing spinels are covered: zinc ferrite ZnO·Fe2O3 to a limited extent and gahnite ZnO·Al2O3 as the main subject, compounds which are found naturally on the Earth’s crust as well as in industrial residues from the zinc industry, steel industry and others. Zinc ferrite contains 27 % of Zn and 33 % as ZnO; resource recovery from ferrite has been studied already in the past. On the other hand, the processing of gahnite, containing 35 % of Zn and 44 % as ZnO, is studied more extensively since research in the field of extractive metallurgy is effectively non-existent. Hence, the main objective of the present thesis is finding routes of treatment for this spinel. Zinc ferrite was produced synthetically at the CiTG/3mE labs by mixing equimolar amounts of ZnO and Fe2O3 at 1100 °C. Gahnite was produced by an analog method, a mixture of equimolar amounts of ZnO and Al2O3. The first approach was hydrometallurgical. Atmospheric hot acid leaching (4 M, 95 °C, 120 min, L/S 40) was performed with H2SO4, HCl and HNO3, resulting in a non-detected dissolution of the compound. Pressure leaching (90 min, L/S 40) was carried out in an autoclave with H2SO4 and HNO3, resulting in a low (2.9 %; 0.75 M, 140 °C, 3.6 bar) and a moderate extraction (22.2 %; 4.0 M, 250 °C, 39.7 bar) respectively. The second approach was pyrometallurgical processing (60 min dwell, 10 °C/min heating rate), divided into two sub-routes. A series of carbothermic tests (1:1.25 stoichiometric ratio) successfully led to a full reduction of the spinel at 1300 °C (99.90 % extraction of zinc). Aluminothermic tests (1.5:2 stoichiometric ratio) successfully resulted in a 99.98 % zinc extraction at 1200 °C. The mix of gahnite and ferrite with carbon at 1300 °C produced a 99.65 % extraction of the metal. Addition of ZnO to the previous mixture resulted in a 100 % extraction, at 1300 °C. Further experiments with gahnite at 1200 °C by adding SiO2, first with carbon and later with aluminium, resulted in a moderate 23.14 % and a low 4.69 % extraction correspondingly. Trials with CaO at 1400 °C created a glass residue and a slag, in each case. It is thus possible to establish the zinc extraction from gahnite ZnO·Al2O3 as follows: Route / Zinc extraction Atmospheric acidic leaching / Non-detected Pressure leaching / Low – Moderate Reduction with aluminium and silica / Low Reduction with carbon and silica / Moderate Carbothermic reduction / Full Aluminothermic reduction / FullEuropean Mineral Engineering CourseGeoscience & EngineeringCivil Engineering and Geoscience
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
The global cropland footprint of Denmark's food supply 2000–2013
No full textThe global use of and pressure on land resources will continue to rise in tandem with the predicted rise in global population and food demand. Addressing unavoidable trade-offs between satisfying human needs and biodiversity conservation for future generations is of paramount importance when tackling the global environmental challenges of land use. Food consumption patterns are inextricably linked to land-use and land-use changes. The domestic supply and final use of food by humans and feed by animals within the borders of a country have environmental impacts overseas. Countries like Denmark, with considerably high livestock production, import "virtual" land needed to produce cereals and other fodder crops. Denmark's high meat and dairy consumption and trade levels make it a compelling case for this study. The overarching question is: how much land is required to support food and feed consumption in Denmark? This paper assesses the global cropland footprint of Danish food and feed supply from 2000 to 2013 using a consumption-based physical accounting approach. In addition to domestic croplands for local food and supply, we estimate the hectares of cropland displaced in other countries to satisfy Danish demand for food and feed in this period. Secondly, we calculate Denmark's global cropland requirements for the supply of specific livestock products, namely; pork, eggs, beef, milk, and mutton. Globally, animals provide a third of the protein in human diets and agricultural GDP. The total global cropland footprint of Danish food and feed supply decreased by 18% from 1568 kha in 2000 to 1282 kha in 2013 because of a reduction in the consumption of ruminant livestock products. A high share of this reduction can be attributed to increased local self-sufficiency in feed supply as opposed to rising food imports. The share of cropland used for feed in total cropland declined by 5% whereas the share of cropland used for food increased from 28% in 2000 to 32% by 2013. Our findings suggest that reducing domestic meat consumption coupled with local self-sufficiency policies for both food and feed supply could be a means of lowering ecological degradation in exporting countries
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
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