277 research outputs found
The flow over delta wings at low speeds with leading edge separation
A low speed investigation of the flow over a 40 degree apex angle delta wing with sharp leading edges had been made in order to ascertain details of the flow in the viscous region near the leading edge of the suction surface of the wing. A physical picture of the flow was obtained from the surface flow and a smoke technique of flow visualization, combined with detailed measurements of total head, dynamic pressure, flow directions and vortex core positions in the flow above the wing
Remote Predictive Mapping 4. Utilizing High Resolution Satellite Imagery, Western Minto Inlier, Victoria Island, NWT
The very high spatial resolution and stereo capability of GeoEye-1 images were utilized to map the geology of a part of the western Neoproterozoic Minto Inlier on Victoria Island. To optimize the results of predictive mapping, a LANDSAT-7 image together with a SPOT-5 image were also used in concert with the GeoEye-1 images. The predictive bedrock geology map, interpreted based on 3D stereo visualization, presents much more detailed geological information compared to the existing 1:500,000 scale geological map of the area. The high spatial and moderate spectral resolution of GeoEye images allowed us to distinguish a black shale unit (black shale member), and resolve subtle spectral and textural differences between massive stromatolitic dolostone and dolostone containing fine-grained interlayers in an upper carbonate member. As well, an important distinction could be made between Proterozoic sedimentary strata and unconformably overlying interlayered sandstone and carbonate rocks of Cambro-Ordovician age. The SWIR bands in the LANDSAT and SPOT images proved to be very useful in identifying gabbro sills. A geological map, based on field work, was used to evaluate the remote predictive map. Comparison of the predictive map with the field map shows that the two maps look similar in terms of the regional distribution of the lithological units; however, there are discrepancies between the two maps, especially in areas in which the bedrock is covered by glacial sediments and/or other overburden materials. The spectral similarity between different stratigraphic units comprising similar rock types, also contributed to differences between the predictive map and the field map.Nous avons utilisĂ© la trĂšs haute rĂ©solution spatiale et les capacitĂ©s stĂ©rĂ©oscopiques des images GeoEye-1 pour cartographier la gĂ©ologie dâune partie de la partie ouest de lâenclave de Minto, datant du NĂ©oprotĂ©rozoĂŻque, de lâĂźle Victoria. Pour optimiser les rĂ©sultats de la cartographie prĂ©dictive, nous avons aussi utilisĂ© une image LANDSAT-7 et une image SPOT-5 avec les images GeoEye-1. Les cartes gĂ©ologiques prĂ©dictives du substratum rocheux, interprĂ©tĂ©es Ă partir dâune visualisation stĂ©rĂ©oscopique 3D, prĂ©sentent des renseignements gĂ©ologiques beaucoup plus dĂ©taillĂ©s que la carte gĂ©ologique actuelle de cette zone Ă lâĂ©chelle de 1/500 000. La haute rĂ©solution spatiale et la rĂ©solution spectrale modĂ©rĂ©e des images GeoEye nous ont permis de distinguer une unitĂ© dâampĂ©lite (membre dâampĂ©lite) et de rĂ©soudre des diffĂ©rences spectrales et texturales subtiles entre la dolomie stromatolithique massive et la dolomie contenant des interstrates Ă grain fin dans un membre carbonatĂ© supĂ©rieur. De plus, nous avons pu faire une distinction importante entre les strates sĂ©dimentaires du ProtĂ©rozoĂŻque et les couches interstratifiĂ©es de roches carbonatĂ©es et de grĂšs du Cambro-Ordovicien qui les surmontent en discordance. Les bandes IRCL des images des satellites LANDSAT et SPOT ont Ă©tĂ© trĂšs utiles pour identifier les filons-couches de gabbro. Une carte gĂ©ologique basĂ©e sur des travaux rĂ©alisĂ©s sur le terrain a servi Ă Ă©valuer la carte de tĂ©lĂ©cartographie prĂ©dictive. Une comparaison de la carte prĂ©dictive et de la carte dressĂ©e sur le terrain montre que les deux cartes semblent similaires en ce qui a trait Ă la rĂ©partition rĂ©gionale des unitĂ©s lithologiques; mais il y a des diffĂ©rences, surtout aux endroits oĂč le substratum rocheux est couvert de sĂ©diments glaciaires et/ou dâautres matĂ©riaux de recouvrement. La similitude spectrale entre les diffĂ©rentes unitĂ©s stratigraphiques ayant des lithologies similaires a aussi contribuĂ© Ă causer des diffĂ©rences entre la carte prĂ©dictive et la carte dressĂ©e sur le terrain
A Comparison of Different Remotely Sensed Data for Classifying Bedrock Types in Canadaâs Arctic: Application of the Robust Classification Method and Random Forests
The Geological Survey of Canada, under the Remote Predictive Mapping project of the Geo-mapping for Energy and Minerals program, Natural Resources Canada, has the mandate to produce up-to-date geoscience maps of Canadaâs territory north of latitude 60°. Over the past three decades, the increased availability of space-borne sensors imaging the Earthâs surface using increasingly higher spatial and spectral resolutions has allowed geologic remote sensing to evolve from being primarily a qualitative discipline to a quantitative discipline based on the computer analysis of digital images.   Classification of remotely sensed data is a well-known and common image processing application that has been used since the early 1970s, concomitant with the launch of the first Landsat (ERTS) earth observational satellite. In this study, supervised classification is employed using a new algorithm known as the Robust Classification Method (RCM), as well as a Random Forest (RF) classifier, to a variety of remotely sensed data including Landsat-7, Landsat-8, Spot-5, Aster and airborne magnetic imagery, producing predictions (classifications) of bedrock lithology and Quaternary cover in central Victoria Island, Northwest Territories. The different data types are compared and contrasted to evaluate how well they classify various lithotypes and surficial materials; these evaluations are validated by confusion analysis (confusion matrices) as well as by comparing the generalized classifications with the newly produced geology map of the study area. In addition, three new Multiple Classification System (MCS) methods are proposed that leverage the best characteristics of all remotely sensed data used for classification.    Both RCM (using the maximum likelihood classification algorithm, or MLC) and RF provide good classification results; however, RF provides the highest classification accuracy because it uses all 43 of the raw and derived bands from all remotely sensed data. The MCS classifications, based on the generalized training dataset, show the best agreement with the new geology map for the study area.SOMMAIREDans le cadre de son projet de TĂ©lĂ©cartographie prĂ©dictive du Programme de gĂ©ocartographie de lâĂ©nergie et des minĂ©raux de Ressources naturelles Canada, la Commission gĂ©ologique du Canada a le mandat de produire des cartes gĂ©oscientifiques Ă jour du territoire du Canada au nord de la latitude 60°. Au cours des trois derniĂšres dĂ©cennies, le nombre croissant des dĂ©tecteurs aĂ©rospatiaux aux rĂ©solutions spatiales et spectrales de plus en plus Ă©levĂ©es a fait passer la tĂ©lĂ©dĂ©tection gĂ©ologique dâune discipline principalement qualitative Ă une discipline quantitative basĂ©e sur l'analyse informatique dâimages numĂ©riques.    La classification des donnĂ©es de tĂ©lĂ©dĂ©tection est une application commune et bien connue de traitement d'image qui est utilisĂ©e depuis le dĂ©but des annĂ©es 1970, parallĂšlement au lancement de Landsat (ERST) le premier satellite d'observation de la Terre. Dans le cas prĂ©sent, nous avons employĂ© une mĂ©thode de classification dirigĂ©e en ayant recours Ă un nouvel algorithme appelĂ© MĂ©thode de classification robuste (MRC), ainsi quâau classificateur Random Forest (RF), appliquĂ©s Ă une variĂ©tĂ© de donnĂ©es de tĂ©lĂ©dĂ©tection dont celles de Landsat-7, Landsat-8, Spot-5, Aster et dâimagerie magnĂ©tique aĂ©roportĂ©e, pour produire des classifications prĂ©dictives de la lithologie du substratum rocheux et de la couverture Quaternaire du centre de l'Ăźle Victoria, dans les Territoires du Nord-Ouest. Les diffĂ©rents types de donnĂ©es sont comparĂ©s et contrastĂ©s pour Ă©valuer dans quelle mesure ils classent les divers lithotypes et matĂ©riaux de surface; ces Ă©valuations sont validĂ©s par analyse de matrices de confusion et par comparaison des classifications gĂ©nĂ©ralisĂ©es des nouvelles cartes gĂ©ologiques de la zone d'Ă©tude. En outre, trois nouvelles mĂ©thodes par systĂšme de classification multiple (MCS) sont proposĂ©es qui permettent dâexploiter les meilleures caractĂ©ristiques de toutes les donnĂ©es de tĂ©lĂ©dĂ©tection utilisĂ©es pour la classification.    Tant la mĂ©thode MRC (utilisant l'algorithme de classification de vraisemblance maximale ou MLC que la mĂ©thode RF donne de bons rĂ©sultats de classification; toutefois câest la mĂ©thode RF qui offre la prĂ©cision de classification la plus Ă©levĂ©e car elle utilise toutes les 43 les bandes de donnĂ©es brutes et dĂ©rivĂ©es de toutes les donnĂ©es de tĂ©lĂ©dĂ©tection. Les classifications MCS, basĂ©es sur le jeu de donnĂ©es gĂ©nĂ©ralisĂ©es dâapprentissage, montrent le meilleur accord avec la nouvelle carte gĂ©ologique de la zone d'Ă©tude
Remote Predictive Mapping 3. Optical Remote Sensing â A Review for Remote Predictive Geological Mapping in Northern Canada
Optical remotely sensed data have broad application for geological mapping in Canadaâs North. Diverse remote sensors and digital image processing techniques have specific mapping functions, as demonstrated by numerous examples and associated interpretations. Moderate resolution optical sensors are useful for discriminating rock types, whereas sensors that offer increased spectral resolution (i.e. hyperspectral sensors) allow the geologist to identify certain rock types (mainly different types of carbonates, Fe-bearing rocks, sulphates and hydroxyl-(clay-) bearing rocks) as opposed to merely discriminating between them. Increased spatial resolution and the ability to visualize the earthâs surface in stereo are now offered by a host of optical sensors. However, the usefulness of optical remote sensing for geological mapping is highly dependent on the geologic, surficial and biophysical environment, and bedrock predictive mapping is most successful in areas not obscured by thick drift and vegetation/lichen cover, which is typical of environments proximal to coasts. In general, predictive mapping of surficial materials has fewer restrictions. Optical imagery can be enhanced in a variety of ways and fused with other geo-science datasets to produce imagery that can be visually interpreted in a GIS environment. Computer processing techniques are useful for undertaking more quantitative analyses of imagery for mapping bedrock, surficial materials and geomorphic or glacial features.
SOMMAIRE
Les donnĂ©es recueillies par tĂ©lĂ©dĂ©tection optique offrent beaucoup de possibilitĂ©s pour la cartographie gĂ©ologique des rĂ©gions nordiques canadiennes. La diversitĂ© des tĂ©lĂ©capteurs et des techniques de traitement numĂ©rique des donnĂ©es permet la dĂ©finition de fonctions de cartographie spĂ©cifique, tel que lâillustre de nombreux exemples et interprĂ©tations associĂ©es. Des capteurs optiques de moyenne rĂ©solution sont utiles pour diffĂ©rencier les types de roche, alors que les capteurs Ă plus fines rĂ©solutions (les capteurs hyperspectraux, par ex.) permettent au gĂ©ologue de subdiviser certains types de roches (principalement diffĂ©rents types de carbonates, roches ferrugineuses, roches Ă sulfates et Ă hydroxyle (argile). Une meilleure rĂ©solution spatiale et la fonction de vision stĂ©rĂ©oscopique sont maintenant offertes sur une gamme de capteurs optiques. Cela dit, lâutilitĂ© de la tĂ©lĂ©dĂ©tection optique pour la cartographie gĂ©ologique est fortement tributaire des conditions de la gĂ©ologie de surface et de son environnement biophysique, le potentiel prĂ©dictif de la tĂ©lĂ©cartographie Ă©tant maximal pour les rĂ©gions exemptes dâune couverture Ă©paisse de dĂ©pĂŽts glaciaires ou dâune couverture vĂ©gĂ©tale/lichen caractĂ©ristique typique des environnements longeant les cĂŽtes. Divers procĂ©dĂ©s permettent de rehausser lâimagerie optique et de rĂ©aliser des fusions avec dâautres jeux de donnĂ©es gĂ©oscientifiques et de produire une imagerie visuellement inter-prĂ©table en environnement de SIG. Les techniques de traitement de donnĂ©es par ordinateur sont utiles pour dâautres types dâanalyse quantitative dâimagerie pour la cartographie des matĂ©riaux de couverture du socle et pour rĂ©pertorier des formes glaciaires et gĂ©omorphologiques
On the influence of virtual camber effect on airfoil polars for use in simulations of Darrieus wind turbines
Darrieus vertical-axis wind turbines are experiencing renewed interest from researchers and manufacturers, though their efficiencies still lag those of horizontal-axis wind turbines. A better understanding of their aerodynamics is required to improve on designs, for example through the development of more accurate low-order (e.g. blade element momentum) models. Many of these models neglect the impact of the curved paths that are followed by blades on their performance. It has been theorized that the curved streamlines of the flow impart a virtual camber and incidence on them, giving a performance analogous to a cambered blade in a rectilinear flow. To test the extent of this effect, wind tunnel experiments have been conducted in a rectilinear flow to obtain lift and drag for three airfoils: a NACA 0018 and two conformal transforms of the profile. The transformed airfoils exhibit the virtual camber that the theory predicts is imparted to a NACA 0018 when used in a Darrieus turbine with blade chord-to-turbine radius ratios, c/R, of 0.114 and 0.25. A parallel computational fluid dynamics campaign has been conducted to study the aerodynamic behavior of the same blades in curvilinear flow in Darrieus-like motion with c/R = 0.114 and 0.25, at tip-speed ratios of 2.1 and 3.1, using novel techniques to obtain blade effective angles of attack. The analysis confirms that the theory holds, with the wind tunnel results for the NACA 0018 being analogous to numerical results for the relevant cambered airfoils. In addition, turbine performance is calculated using computational fluid dynamics and a blade element momentum code, for each of the blades in turn. The computational fluid dynamics results for the NACA 0018 agree closely to blade element momentum results for the equivalent cambered airfoil where c/R = 0.25, for both turbine power and blade tangential forces. Agreement between the two methods using geometrically identical blades is poor at both the blade and turbine level for c/R = 0.25. It is concluded that when modeling a Darrieus rotor using blade element momentum methods, applying experimental data for the profile used in the turbine will yield inaccurate results if the c/R ratio is high, in such cases it is necessary to select a profile based on the virtual shape of the blades
Comment on âNew palaeomagnetic result from Vendian red sediments in Cisbaikalia and the problem of the relationship of Siberia and Laurentia in the Vendianâ by S. A. Pisarevsky, R. A. Komissarova and A. N. Khramov
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73333/1/j.0956-540x.2001.01474.x.pd
Environmental DNA captures elasmobranch diversity in a temperate marine ecosystem
Many sharks, skates, and rays (elasmobranchs) are highly threatened by the activities of commercial fisheries, and a clear understanding of their distributions, diversity, and abundance can guide protective measures. However, surveying and monitoring elasmobranch species can be highly invasive or resource-intensive, and utilization of non-invasive environmental DNA-based methods may overcome these problems. Here, we studied spatial and seasonal variation in the elasmobranch community of the Western English Channel using environmental DNA (eDNA) collected from surface and bottom waters periodically over an annual cycle (2017â2018). In total we recovered 13 elasmobranch species within eDNA samples, and the number of transformed eDNA reads was positively associated with species (hourly) catch data resolved from 105-year time series trawl data (1914â2018). These results demonstrate the ability of eDNA to detect and semi-quantitatively reflect the prevalence of historically dominant and rare elasmobranch species in this region. Notably, eDNA recorded a greater number of species per sampling event than a conventional trawl survey in the same area over the same sampling years (2017â2018). Several threatened species were recovered within the eDNA, including undulate ray, porbeagle shark, and thresher shark. Using eDNA, we found differences in elasmobranch communities among sampling stations and between seasons, but not between sampling depths. Collectively, our results suggest that non-invasive eDNA-based methods can be used to study the spatial and seasonal changes in the diversity and abundance of whole elasmobranch communities within temperate shelf habitats. Given the threatened status of many elasmobranchs in human-impacted marine environments, eDNA analysis is poised to provide key information on their diversity and distributions to inform conservation-focused monitoring and management
Sustainable development and African local government: can electronic training help build capacities?
A recent study carried out by European and African organizations into the potential for electronic distance training (EDT) on sustainability in African local governments concluded that EDT was both 'useful and feasible'. This article reflects on some of the theoretical and practical implications of that study. It focuses on the connection between learning and sustainability and how EDT programmes might be designed and promoted. The paper argues that, while resource issues and poor access to Information and Communication Technologies (ICTs) create considerable constraints and point to the need for policies to improve access, in general the most important factors for successful capacity building relate to the design of learning programmes that take account of the work contexts and skill and capability requirements of those targeted as learners. 'Useful' and 'feasible' depend on (i) how work-based and work-related learning processes are understood and (ii) the conditions to promote learning within African local government.
Keywords: Africa; Electronic distance training; Local government; Sustainability; Workplace learnin
Trends in publications regarding evidence-practice gaps: A literature review
<p>Abstract</p> <p>Background</p> <p>Well-designed trials of strategies to improve adherence to clinical practice guidelines are needed to close persistent evidence-practice gaps. We studied how the number of these trials is changing with time, and to what extent physicians are participating in such trials.</p> <p>Methods</p> <p>This is a literature-based study of trends in evidence-practice gap publications over 10 years and participation of clinicians in intervention trials to narrow evidence-practice gaps. We chose nine evidence-based guidelines and identified relevant publications in the PubMed database from January 1998 to December 2007. We coded these publications by study type (intervention versus non-intervention studies). We further subdivided intervention studies into those for clinicians and those for patients. Data were analyzed to determine if observed trends were statistically significant.</p> <p>Results</p> <p>We identified 1,151 publications that discussed evidence-practice gaps in nine topic areas. There were 169 intervention studies that were designed to improve adherence to well-established clinical guidelines, averaging 1.9 studies per year per topic area. Twenty-eight publications (34%; 95% CI: 24% - 45%) reported interventions intended for clinicians or health systems that met Effective Practice and Organization of Care (EPOC) criteria for adequate design. The median consent rate of physicians asked to participate in these well-designed studies was 60% (95% CI, 25% to 69%).</p> <p>Conclusions</p> <p>We evaluated research publications for nine evidence-practice gaps, and identified small numbers of well-designed intervention trials and low rates of physician participation in these trials.</p
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