1,720,952 research outputs found
Parametric design-tool to optimize preliminary design of navigation lock chambers
No full textSummaryIn the twentieth century a substantial number of navigation locks were build in the Netherlands. The navigation locks built in that era mostly had a life span of 80 to 100 years. This means that in the coming years most of these locks will be in need of either renovation or replacement. Rijkswaterstaat, the administrator of most of the locks in the Netherlands, is likely to put out tenders for the renovation and replacement of these locks. Companies can subsequently submit a proposal for design and/or construction. This proposal includes a preliminary design of the lock. During this phase of the design multiple possible alternatives will be reviewed to check which of those satisfy the design requirements and how they will be implemented. The time available to create a proposal is limited and the preliminary design phase is time consuming due to the numerous design alternatives available. Therefore, several alternatives are often not elaborated, which already leads to converging in the design process in an early phase. When the time needed to create a design of the alternatives can be reduced, the converging can be postponed to the detailed design and more attention can be paid to out-of-the-box thinking during preliminary design. This time saving can be accomplished by the use of automation and parametric design. With parametric design all the possible alternatives can be calculated in a given range of parameters. After comparison of these generated alternatives a well-educated choice can be made for the direction in preliminary design. This research aims to optimize preliminary lock design in the tendering phase by creating a design-tool that automatically generates all plausible alternatives based on the Design Criteria and boundary conditions of the client. Eventually, the complete preliminary lock design can be accomplished with a parametric design tool. However, an advantage of a design tool is that it can be composed of different building blocks which all design a specific part of the navigation lock. The basis of the parametric design tool should be a relevant part of the lock when looking at the total costs of this part, the design costs, the variety of options and the relation with other parts. The lock chamber is chosen as a starting point for the design tool. The lock chamber, like the lock head and the mechanics, has high investment costs and a high percentage of design costs. The lock chamber however, is in contrast to the other parts of the lock, not heavily dependent on other components. This makes it an interesting component to make a parametric design tool out of. The parametric model, that has been developed as a part of this thesis, includes the commonly used chamber types for inland navigation locks. These common types are retaining wall structures with an under water concrete floor including sheet pile, combi and diaphragm walls, and a U-basin structure, which can be constructed in an open building pit or in a temporary retaining wall building pit. When the design tool is finished, research is conducted on the behaviour of the alternatives in different circumstances. The effects of the main design criteria are examined. These include the length of the chamber, width, depth, water drop and local soil profile. These values are mostly depended on the vessels that need to be accommodated and the local circumstances. Next to that, the impact of different construction methods, the use of materials and the variation in unit prices are elaborated. In this thesis the second Juliana lock near Gouda is used as reference case. For this case it has been found that a sheet pile wall structure is economically most attractive, followed by the U-basin with an open building pit, a diaphragm wall structure and least feasible a U-basin structure with a retaining wall building pit. It is concluded that the length of the lock does hardly impact the design of the alternatives. The width of the chamber does influence the dimensions of the structure. The floor has to be stronger for larger widths and, because of this, the diaphragm wall structure will become more attractive compared to the U-basin structures. The depth and water drop mainly impacts the dimensions of the walls. This, combined with the increased soil handling with open building pits, leads to decreasing interest in U-basin structures. When looking at the construction methods and materials, it can be noted that the length of the tension piles is especially important for the pile plan and the floor. The concrete strength for the U-basins is of importance, while the under water concrete strength and the casting method hardly influence the total costs. When looking at environmental impact, the alternative with the least material use is most attractive, the sheet pile wall structure followed, by the diaphragm wall structure. The type of material does heavily influence the environmental impact. The U-basin structures have more environmental impact due to the construction of a larger temporary building pit. The environmental impact consists of three main components, the used materials, transport of these materials and the processes for the construction of the lock. For the U-basin structures the last two components have a large impact, while for the retaining wall structures the materials used have a large footprint. The proposed CO2 taxes of € 0,05 an €0,20 per kg CO2 equivalent will lead to an average cost increase of respectively 4,5% and 16.5%. The impact per alternative differs, but does not influence the order of economical feasibility. As from a CO2 tax of € 0,68 per kg CO2 equivalent the diaphragm wall structure will become financially more attractive compared to the U-basin structure with open building pit. Despite the calculated strengths and costs, each structure has its own advantages, disadvantages and limitations in construction, final use and maintenance. Special attention should be paid to these properties, since certain construction methods may be excluded by design requirements and uncertainties can lead to high risk. Further research could focus on steel sheet or combi piles constructed in bentonite excavations, resolving the limitations of vibrations during sheet pile construction and the uncertainties of diaphragm walls.Civil Engineering | Hydraulic Engineerin
Early colonization of littoral communities on polyurethane coated substrates: A field and laboratory study
No full textMaterials used for urbanized coastal structures often create a hard substra te ready to be colonized. Elastocoast, a new coastal protection material made from stones and polyurethane, is such a material. This study examined the recovery and growth during the winter of 2007-2008 of the biological community on two dykes in the Netherlands which were refurbished with Elastocoast at the beginning of the storm season, and describes an algal colonization experiment done with Elastocoast in the laboratory. In the field, 4 months after the cons truction of the Elastocoast top layer, dyke vegetation has returned, though strongly zonated and leaving large patches without any vegetation. Main algal species are Enteromorplta mi1tima and Fucus spiralis. Animals found on the Elastocoast layer mainly consisted of Littoriua sp. and Patella Vulgata. The Elastocoast pilots in the field were examined for 25 weeks, it is expected that the biological community will recover further when given enough time. The laboratory experiment showed that by colonization by micro-algae under favorable circumstances can be fast and substantial, by numerous micro algae and animals. Elastocoast therefore seems to be a material which allows community recovery to be fast and according to the typical vegetation of that area
Author Correction: Priority list of biodiversity metrics to observe from space
Get PDFIn the version of this Perspective originally published, Claudia Roeoesli was missing from the author list. This has now been corrected
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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