813 research outputs found
Flipping forests: estimating future carbon sequestration of the boreal forest using remotely sensed data
No full textTo reduce uncertainty in national and global carbon budgets, carbon sequestration can be estimated for large areas of land by driving an aspatial ecosystem simulation model (ESM) spatially, with remotely sensed biophysical data. This letter investigates the impact of future climate change on the boreal forest carbon budget by driving the FOREST-BGC (-Bio-Geochemical Cycling) ESM (under three different carbon dioxide (CO2) emission scenarios) using remotely sensed (NOAA AVHRR) estimates of leaf area index (LAI) as part of the Boreal Ecosystem Atmosphere Study (BOREAS).We demonstrate that boreal forests will continue to provide a substantial 'brake' on the rate of increase in atmospheric CO2, provided anthropogenic emissions reduce dramatically to within the limits of the 'Kyoto Protocol'. However, if anthropogenic emissions follow the unmitigated scenario (i.e. 'business as usual'), carbon sequestration will increase to a maximum by around 2050 but thereafter collapse, resulting in a disappearance of the boreal carbon sink by around 2080. An ESM and remotely sensed data was a viable predictive tool for the study of carbon sequestration over land and has potential as an aid for policy and management decisions
Polygon-based aggregation of remotely sensed data for regional ecological analyses
No full textGiven current concerns about global climate change, there is an urgent need to quantify and monitor accurately the magnitude of present day terrestrial carbon sinks. This may be achieved by driving ecosystem simulation models (ESMs) spatially with remotely sensed estimates of ecological variables, such as leaf area index (LAI). Conventional procedures for analysing digital remotely sensed images rely upon pixel-based methods, using spectral information from each pixel to allocate it to a land cover type or estimate a surface property (e.g. LAI). Groups of pixels, within areas assumed to be ‘thematically homogeneous’, will not necessarily provide the same allocation or estimation due to data noise, atmospheric effects and natural variation of the surface. Pixels on the boundary between areas are an additional problem as their spectral information derives from more than one surface type. If contextual information on the spatial pattern and structure of the landscape could be included in the analysis (e.g. forest inventory polygons, agricultural land parcels), then the accuracy of the allocations or estimations (e.g. of LAI) could be increased. Polygon-based approaches, where all pixels within a defined area are presumed similar and so can be combined prior to analysis, offer a solution. These approaches are implemented most efficiently within an integrated GIS where raster and ancillary data can be analysed with reference to vector land polygons. A procedure using remotely sensed data in a polygon format to produce accurate spatial estimates of LAI (on which to drive an ESM) is described. In relation to a pixel-based procedure, the polygon-based procedure provided: (1) increased accuracy, (2) more appropriate and realistic representations of the environment and (3) a powerful and flexible framework for further data analysis. <br/
On the equilibrium problem and infinitesimal mechanisms of class theta tensegrity systems
No full textThis work presents a study on the equilibrium problem and the infinitesimal mechanisms of class θ= 1 tensegrity prisms. Local solutions of the self-equilibrium problem are numerically obtained through Newton-Raphson iterations. The presented results suggest that the analyzed structures can be usefully employed as building blocks of novel tensegrity metamaterials, due to their rich kinematic response and the considerably large number of infinitesimal mechanisms. © 2019 Author(s)
Full 3D CAD procedure for the speedy evaluation of the seismic vulnerability of masonry towers
No full textA very straightforward 3D CAD approach for the speedy evaluation of the seismic vulnerability of existing masonry towers is presented. The procedure requires only the detailed 3D geometric model of the structure and automatically calculates the collapse acceleration on a user defined failure mechanism. In this paper, few pre-assigned mechanisms are tested, as for instance vertical splitting, simple overturning at the base, rocking with inclined yield lines and combined rocking and vertical splitting. The restriction of the possible tower failure within such a few mechanisms grounds on previous numerical research in the field and post-earthquake surveys experience. In any case, any user can define his own mechanisms according to the specificity of the case-study under consideration, directly shaping distinct volumes inside the CAD software. The procedure is automatized and the direct application of the principle of virtual works-assuming that masonry behaves as a no-tension material-allows the immediate evaluation of the horizontal acceleration at collapse. The mechanism associated to the minimum acceleration, in agreement with the kinematic theorem of limit analysis, is that most probably would occur in reality during a seismic event. The approach allows a straightforward evaluation of the seismic vulnerability of a tower and can be used even by practitioners not familiar with advanced FE computations and limit analysis concepts, so adapting well to the heterogeneous community involved in cultural heritage preservation. The automatized procedure is applied in this paper to a historical tower located in central Italy, to show the capabilities of the approach. © 2019 Author(s)
The Arab peoples of T.E. Lawrence's Seven Pillars of Wisdom in the light of post-colonial theory
No full textIt can be said that The Seven Pillars of Wisdom is a work whose true potential has not yet been discovered. That the work presents itself to be of greater value than may have previously seemed goes without question. However, during the more than eighty years of its existence, it was the author and not the work that created major interest in the academic world. The complicated character of T.E. Lawrence offered itself to psycho-analyst interpretation and most critiques have been built on these premises. Other works have concentrated on major historical events in Lawrence's life creating thorough biographies and numbers of fascinating approaches, some more, some less misleading were created. However. The Seven Pillars of Wisdom (from henceforth "Seven Pillars") foremostly survived in the shadows of David Lean's film "Lawrence of Arabia" and it was only during the late seventies, that concentration on the Seven Pillars as a text had begun to be cultivated. Additionally, it has only been during the past few years that works by writers such as Gertrude Bell, T.E. Lawrence or Charles M. Doughty have begun to gain a larger public interest. The aim of this work, however, is not to analyse the historical purpose of Lawrence's presence in the Middle East, nor to align the Seven Pillars with historical facts. Such..
The Arab peoples of T.E. Lawrence's Seven Pillars of Wisdom in the light of post-colonial theory
No full textIt can be said that The Seven Pillars of Wisdom is a work whose true potential has not yet been discovered. That the work presents itself to be of greater value than may have previously seemed goes without question. However, during the more than eighty years of its existence, it was the author and not the work that created major interest in the academic world. The complicated character of T.E. Lawrence offered itself to psycho-analyst interpretation and most critiques have been built on these premises. Other works have concentrated on major historical events in Lawrence's life creating thorough biographies and numbers of fascinating approaches, some more, some less misleading were created. However. The Seven Pillars of Wisdom (from henceforth "Seven Pillars") foremostly survived in the shadows of David Lean's film "Lawrence of Arabia" and it was only during the late seventies, that concentration on the Seven Pillars as a text had begun to be cultivated. Additionally, it has only been during the past few years that works by writers such as Gertrude Bell, T.E. Lawrence or Charles M. Doughty have begun to gain a larger public interest. The aim of this work, however, is not to analyse the historical purpose of Lawrence's presence in the Middle East, nor to align the Seven Pillars with historical facts. Such..
Minimum MSE estimation of a regression model with fixed effects from a series of cross sections (Revised version)
No full textEstimation
Pathways to Industrial-Scale Fuel Out of Thin Air from CO<sub>2</sub> Electrolysis
No full textUsing renewable energy as an input, Power-to-X technologies have the potential to replace fossil fuels and chemicals with dense-energy carriers that are instead derived out of thin air. In this work, we put into context what the industrial-scale production of chemicals from ambient CO2 using CO2 electrolysis means in terms of future required operating conditions and the device and catalyst scales that will be needed for the technology to assume its role in our global energy system.Accepted Author ManuscriptChemE/Materials for Energy Conversion and StorageChemE/Transport Phenomen
Mechanical modeling of the bandgap response of tensegrity metamaterials
No full textWe investigate the acoustic band structure of tensegrity mass-spring chains as a function of the applied, local and global states of prestress. We first study the bandgap response of linear monoatomic chains, which show lumped masses connected to tensegrity prisms acting as mechanical springs. Next, we present a numerical study on the nonlinear wave dynamics of the examined systems in the geometrically nonlinear regime that is induced by the presence of moderately large relative displacements between the lumped masses. Such a study confirms the results of the linear analysis in the case of an elastically hardening system. © 2019 Author(s)
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