1,720,959 research outputs found
Sammenligning av flybåren og bakkebaserte resistivitetsmålinger for å indikere kvikkleire i Orkdal, Trøndelag
No full textDenne masteroppgaven er skrevet som en del av et samarbeidsprosjekt mellom Norges geologiske undersøkelse (NGU) og Norges vassdrags- og energidirektorat (NVE), som ble initiert av Orkland kommune, Trøndelag i forbindelse kvikkleirproblematikk i kommunen. Prosjektet har som hovedmål å videreutvikle anvendelsen av geofysiske metoder for tredimensjonal kartlegging av dalfyllinger, med spesielt fokus på marin leire og identifisering av potensielle kvikkleireforekomster. Løsmassene i Orkdal er avsatt i den karakteristiske lagrekkefølgen som oppstår som et resultat av isens tilbaketrekning under siste istid og påfølgende strandforskyving. På dalbunn blir det avsatt sedimenter fra breen, inkludert morene og mulige breelvavsetninger. Disse sedimentene blir deretter dekket av mektige hav- og fjordavsetninger, og på toppen dekkes dalen av elveavsetninger.
På bakgrunn av at de tradisjonelle metodene for å påvise kvikkleire er kostbare, tidkrevende og kun gir punktvis informasjon om undergrunnen, er det de siste tiårene sett nytten av supplerende geofysiske undersøkelser. Denne oppgaven fokuserer hovedsaklig på ulike resistivitetsmålinger, fra helikopter, langs bakken, i borehull og i laboratoriet. Resistivitetsmålinger bygger på prinsippet om at jordarter har naturlig store forskjeller i elektrisk ledningsevne, og kan ved hjelp av det differensiere mellom marin, saltholdig leire og utvasket, mulig kvikkleire. Det mest brukte resistivitetsintervallet for utvasket, mulig kvikkleire er 10-100 \ohm m, og bestemmelse av dette intervallet er viktig for tolkningsmulighetene ved bruk av metodene. Resistiviteten til leire påvirkes av en rekke faktorer og videre forskning på dette vil ha stor nytteverdi.
De geofysiske metodene elektrisk resistivitetstomografi (ERT) og helikopterbåren elektromagnetiske (HEM) målinger gir sammenhengende informasjon om undergrunnen og dekker store områder på forholdsvis kort tid. Dette gjør de egnet til tidlig fase kvikkleirekartlegging for å optimalisere borelokasjoner. Resultatene fra bakkebaserte og helikopterbaserte resistivitetsmålinger viser både i denne studien og tidligere studier et godt overordnet samsvar hvis man sammenligner hovedstrukturer. En en-til-en sammenligning blir ofte misvisende på grunn av forskjell i oppløsning og inversjonsprosedyre. Metodene viser også samsvar med resistivitetsmålinger utført i borehull og i laboratoriet, noe som styrker metodenes pålitelighet og anvendbarhet. ERT- og HEM-data viser best lineær korrelasjon ved lave resistivitetsverdier, slik som i leire. Og viser en avtagende trend ved høyere resistivitetsverdier. De største avvikene fra den lineære trenden mellom metodene er funnet til å være i de grunneste 10 meterene i undergrunnen, ofte på grunn av tilstedeværelse av tørrskorpeleire.This master's thesis is written as part of a collaborative project between the Geological Survey of Norway (NGU) and the Norwegian Water Resources and Energy Directorate (NVE), initiated by the municipality of Orkland in Trøndelag. The main objective of the project is to further develop the application of geophysical methods for three-dimensional mapping of valley fill deposits, with a specific focus on marine clay and identification of potential quick clay. The sediments in Orkdal reflects the characteristic stratigraphy resulting from the deglaciation during the last glacial period. At the base, sediments from the glacier, including till and glaciofluvial deposits, are deposited. These sediments are then covered by thick layers of marine deposits, and finally the valley floor will be covered by fluvial deposits.
Due to the expensive, time-consuming, and localized nature of traditional methods for detecting quick clay, there has been an increasing recognition in recent decades of the utility of supplementary geophysical investigations. This thesis primarily focuses on various resistivity measurements conducted from helicopters, on the ground, in boreholes, and in the laboratory. Resistivity measurements are based on the principle that different soil types exhibit natural variations in electrical conductivity, allowing for differentiation between marine, saline clay and leached, potentially quick clay. The most common resistivity range for leached, potentially quick clay is 10-100 Ωm, and the determination of this range is crucial for the proper interpretation of results. The resistivity of clay is influenced by various factors and is a promising parameter for further research.
The geophysical methods electrical resistivity tomography (ERT) and helicopter-borne electromagnetic (HEM) measurements provide continuous information about the subsurface and cover large areas in relatively short timeframes. Consequently, they are suitable for early-phase quick clay mapping to optimize drilling locations. The results from both ERT and HEM demonstrate good overall agreement for the main sedimentological structures, both in this and previous studies. One-to-one comparisons can be misleading due to differences in resolution and inversion procedures. These methods also show consistency with resistivity measurements conducted in boreholes and in the laboratory, which strengthens the reliability and applicability of the methods. ERT and HEM data exhibit the strongest linear correlation at low resistivity values, such as those corresponding to clay. As resistivity values increase, the correlation tends to decrease. The largest deviations from the linear trend are found in the shallowest 10 meters of the subsurface, often due to the presence of dry crust clay
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Fuzzy clustering for the compilation of pseudo-lithology maps and the exploration of zones of mineralization in Karasjok, northern Norway
No full textNorthern Norway has an extensive geological variation compared to other parts of Norway. It is home to major ore deposits containing base and precious metals. It is located within Fennoscandia, which has been identified as a significant metal-producing region in Europe. Recently, Northern Norway has extensively been surveyed using several geophysical techniques, which led to coverage improvement of basic geological information relevant to the assessment of its mineral potential.The study area, in the vicinity of Karasjok, is located on the Karasjok Greenstone Belt and comprises mainly Palaeoproterozoic rocks. This terrane is located on the same Palaeoproterozoic greenstone terrane of northern Finland, in which the detected gold deposits showed, with a few exceptions, similar characteristics to gold occurrences in Palaeoproterozoic greenstone belts in other parts of the world. Also, economic mineral deposits, e.g. Ni-Cu-PGE-Au mineralization, are largely restricted to events that occurred during the Palaeoproterozoic era. However, the study area for this study still remains largely under-explored and previous research and field work of the Karasjok Greenstone Belt have proven unsuccessful to locate significant mineral deposits. This area contains very few outcrops and traditional methods to map such areas are challenging.A large number of different geophysical data sets exist for Norway. While individual data sets cannot provide direct information about the lithology of the mapped area, a combination of multiple data sets makes it possible to delineate and interpret characteristic regions of potentially similar lithology. This is of particular interest where the geological map may be unreliable or that geological mapping itself is difficult, for example, due to difficult accessibility or large vegetation coverage.In this study, three fuzzy clustering algorithms, i.e. the fuzzy c-means algorithm, the Gustafson-Kessel algorithm, and the possibilistic fuzzy c-means algorithm, have been applied to compile pseudo-lithology maps and to characterize zones of mineralization by integrating recently acquired high-resolution airborne geophysical data sets of Karasjok. These algorithms have been applied for the integration of long-wavelength data sets, i.e. gravity and magnetic data reflecting deep geological features, the integration of short-wavelength data sets, i.e. gravity and magnetic data reflecting shallow geological features, and the integration of three near-surface data sets, i.e. the two short-wavelength data sets and a potassium data set. Analyzing the interrelationship of the data sets and pre-processing the data sets, have shown to be necessary steps in order to determine what kind of geological differentiation of the study area will be obtained when applying the clustering algorithms.The application of the fuzzy clustering algorithms for the compilation of pseudo-lithology maps have shown promising results. While the long-wavelength data sets indicated different, likely deeper, geological features than has been mapped on the current bedrock map and did not show similar structures on a lo- cal scale, the clustering with short-wavelength data sets indicated similarities on a local scale. Adding the potassium data set as a third dimension, results in patterns that clearly reflect the presence of the Archaean tonalities gneisses and granites of the Jergul Gneiss Complex within the study area. This showed how the use of clustering with three data sets can obtain a larger geological differentiation of the study area. It is concluded that the local structures have a more detailed composition than currently mapped.The application of clustering algorithms for the identification of zones of mineralization for this study has proven to be a powerful tool as it allows for the extraction of clusters of interests. One can simply use the clusters of interest to outline the areas of interest. In this case, the focus was to find areas that contain possible Ni-Cu-PGE mineralization, which are commonly reflected by high Bouguer and high magnetic anomalies. During this study, the clustering algorithm not only identified zones that were mentioned by previous re- search to contain possible mineralization, but also three additional zones that have not been explored or identified before.Aerospace Engineerin
Variations on the Author
No full text“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
No full textWe 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
The Evolution of Deep-Water Salt-Tectonic Structures, Numerical Modeling Studies applied to the Northwestern Gulf of Mexico
No full textSalt tectonics is a key player in the evolution of many worldwide sedimentary basins on rifted continental margins. For more than a century, the evolving structures have been studied; but focus remained primarily on the onshore and shallow-water regions. The evolution of the poorly studied deep-water salt-tectonic structures is the focus of this thesis. Investigations are performed using 2D numerical models that comprise a viscous salt layer overlain by a frictional-plastic passive margin sedimentary sequence from shelf to deep water.
This thesis addresses multiple salt-tectonic processes (gravity spreading, evolution of fold belts and salt canopies, diapirism) in a general context but with special focus on the structural evolution of the northwestern Gulf of Mexico (GoM). Here, multiple phases of gravity-spreading induced salt mobilization and thin-skinned deformation occurred throughout the Cenozoic. During the latest, late Oligocene-Miocene phase, the Perdido Fold Belt (PFB) formed from a 4.5km thick pre-kinematic section as a prominent salt-cored deep-water structure above the pinch-out of the autochthonous salt. It is here demonstrated with analytical as well as numerical calculations that the folding of the PFB can have formed by gravity spreading alone without basement tectonics. A requirement for this deformation is very high pore-fluid pressure in the sediments, which effectively reduces the sediments' mechanical strength. These values are refined using numerical models that couple compaction-induced fluid pressure to mechanical deformation. It is shown that very high fluid pressure is only necessary at the landward base of the deforming system; fluid pressure in other regions may remain moderate. This study shows, for the first time, the regional and dynamic evolution of pore-fluid pressure in a continental margin sedimentary system above salt. Additionally, the contribution of `lateral compaction' during fold-belt evolution is addressed.
Landward of the PFB, a large-scale canopy developed during the Eocene. Its evolution is studied by investigating three different concepts of canopy evolution that have been proposed in the scientific literature. A canopy evolving via the mechanism of squeezed diapirs is most similar to the Eocene canopy of the northwestern GoM. A canopy evolving via the mechanism of breached anticlines is similar to that observed above the landward end of the PFB. Dynamic diapir growth is addressed in a neutral stress regime under uneven sedimentation employing a new mechanism of diapir initiation and evolution
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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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