排序方式： 共有16条查询结果，搜索用时 281 毫秒
1.
Gianmarco Alberti 《制图学和地理信息科学》2018,45(6):510-528
Cost-surface analysis in Geographic Information System (GIS) environment has been less frequently used in the study of ancient sail navigation than in other studies of the human past. Navigation cost-surface analysis entails the use of GIS tools that are versatile but not very easy to grasp and to put to work. This article describes an ArcGIS toolbox built to facilitate cost-surface analysis of ancient sail navigation. It estimates the navigation time from a start location, considering parameters relevant for the generation of an accumulated anisotropic cost-surface, automating the complex workflow required to meaningfully pre- and post-process the data. Acknowledging the limitations inherent to the tool, and to the modeling of a complex matter such as sail navigation, the toolbox is first described and then used in a worked example. Historically recorded voyages in the Mediterranean during classical antiquity are compared to estimated durations generated by the toolbox. In spite of structural and expected limitations, the results indicate that the proposed toolbox may produce reasonable estimates. These should be thought of as values gravitating around, not matching, likely past durations. The estimated values may prove useful as an indication of the order of magnitude of past voyages’ duration, and as frame of reference in measuring ancient maritime space through time. 相似文献
2.
Stefano De Santis Paolo Casadei Gerardo De Canio Gianmarco de Felice Marialaura Malena Marialuisa Mongelli Ivan Roselli 《地震工程与结构动力学》2016,45(2):229-251
An innovative solution for the seismic protection of existing masonry structures is proposed and investigated through shake table tests on a natural scale wall assemblage. After a former test series carried out without reinforcement, the specimen was retrofitted using Steel Reinforced Grout. The strengthening system comprises horizontal strips of ultra‐high strength steel cords, externally bonded to the masonry with hydraulic lime mortar, and connectors to transversal walls, applied within the thickness of the plaster layer. In order to assess the seismic performance of the retrofitted wall, natural accelerograms were applied with increasing intensity up to failure. Test results provide a deep understanding of the effectiveness of mortar‐based composites for improving the out‐of‐plane seismic capacity of masonry walls, in comparison with traditional reinforcements with steel tie‐bars. The structural implications of the proposed solution in terms of dynamic properties and damage development under earthquake loads are also discussed.Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
3.
Rutger de Wit Lucas J. Stal Bente Aa. Lomstein Rodney A. Herbert Hans van Gemerden Pierluigi Viaroli Victor-Ugo Cecherelli Francisco Rodríguez-Valera Marco Bartoli Gianmarco Giordani Roberta Azzoni Bart Schaub David T. Welsh Andrew Donnelly Ana Cifuentes Josefa Antn Kai Finster Lise B. Nielsen Anne-Grethe Underlien Pedersen Anne Turi Neubauer Marina A. Colangelo Sander K. Heijs 《Continental Shelf Research》2001,21(18-19)
“Buffer capacities” has been defined in ecology as a holistic concept (e.g., Integration of Ecosystem Theories: A Pattern, second ed. Kluwer, Dordrecht, 1997, 388pp), but we show that it can also be worked out in mechanistic studies. Our mechanistic approach highlights that “buffering capacities” can be depleted progressively, and, therefore, we make a distinction between current and potential “buffering capacities”. We have applied this concept to understand the limited “local stability” in seagrass ecosystems and their vulnerability towards structural changes into macro-algal dominated communities. We explored the following processes and studied how they confer buffering capacities to the seagrass ecosystem: (i) net autotrophy is persistent in Zostera noltii meadows where plant assimilation acts as a sink for nutrients, this contrasted with the Ulva system that shifted back and forth between net autotrophy and net heterotrophy; (ii) the Z. noltii ecosystem possesses a certain albeit rather limited capacity to modify the balance between nitrogen fixation and denitrification, i.e., it was found that in situ nitrogen fixation always exceeded denitrification; (iii) the nitrogen demand of organoheterotrophic bacteria in the sediment results in nitrogen retention of N in the sediment and hence a buffer against release of nitrogen compounds from sediments, (iv) habitat diversification in seagrass meadows provides shelter for meiofauna and hence buffering against adverse conditions, (v) sedimentary iron provides a buffer against noxious sulfide (note: bacterial sulfide production is enhanced in anoxic sediment niches by increased organic matter loading). On the other hand, in the coastal system we studied, sedimentary iron appears less important as a redox-coupled buffer system against phosphate loading. This is because most inorganic phosphate is bound to calcium rather than to iron. In addition, our studies have highlighted the importance of plant–microbe interactions in the seagrass meadows. 相似文献
4.
de Felice Gianmarco Fugger Rebecca Gobbin Francesca 《Bulletin of Earthquake Engineering》2022,20(2):941-962
Bulletin of Earthquake Engineering - The out-of-plane collapse of the façade represents one of the major threats and the most frequent cause of damages of churches due to strong earthquakes.... 相似文献
5.
Tardivo Gianmarco Bixio Vincenzo Bixio Anna Chiara 《Theoretical and Applied Climatology》2022,149(1-2):169-183
Theoretical and Applied Climatology - This paper deals with precipitation events, particularly the problem of recognising events individually, of distinguishing one local... 相似文献
6.
The solution to the 2-D time-dependent unsaturated flow equation is numerically approximated by a second-order accurate cell-centered finite-volume discretization on unstructured grids. The approximation method is based on a vertex-centered Least Squares linear reconstruction of the solution gradients at mesh edges.A Taylor series development in time of the water content dependent variable in a finite-difference framework guarantees that the proposed finite volume method is mass conservative. A Picard iterative scheme solves at each time step the resulting non-linear algebraic problem. The performance of the method is assessed on five different test cases and implementing four distinct soil constitutive relationships. The first test case deals with a column infiltration problem. It shows the capability of providing a mass-conservative behavior. The second test case verifies the numerical approximation by comparison with an analytical mixed saturated–unsaturated solution. In this case, the water drains from a fully saturated portion of a 1-D column. The third and fourth test cases illustrate the performance of the approximation scheme on sharp soil heterogeneities on 1-D and 2-D multi-layered infiltration problems. The 2-D case shows the passage of an abrupt infiltration front across a curved interface between two layers. Finally, the fifth test case compares the numerical results with an analytical solution that is developed for a 2-D heterogeneous soil with a source term representing plant roots. This last test case illustrates the formal second-order accuracy of the method in the numerical approximation of the pressure head. 相似文献
7.
Gianmarco Giordani Martina Austoni José M. Zaldívar Dennis P. Swaney Pierluigi Viaroli 《Estuarine, Coastal and Shelf Science》2008
The Land-Ocean Interactions in the Coastal Zone (LOICZ) biogeochemical model (LBM) was applied at different temporal and spatial scales in 17 Italian lagoons of the LaguNet network (http://www.dsa.unipr.it/lagunet). A series of alternative assumptions taking into account benthic vegetation and sedimentary fluxes were introduced and compared with the classical LBM approach at various time scales. The reliability of the LBM application to the seventeen Italian lagoons was tested by comparison to a pool of shallow coastal systems from the global LOICZ database with comparable depths and sizes. The nutrient loads of the Italian sites can be considered relatively low, particularly for dissolved inorganic phosphorus (DIP). Although the median values of estimated internal transformations (source-sink) of both dissolved inorganic phosphorous and nitrogen at the LaguNet sites were comparable with the selected LOICZ sites, the positive and negative extreme values were one order of magnitude lower. Overall, the LBM applications to the Italian sites gave good quality budgets for shallow systems subjected to relatively low nutrient inputs and with a wide range of primary producer communities, including seagrass, macroalgae and phytoplankton. Furthermore, stoichiometry of Carbon:Nitrogen:Phosphorous for the different primary producer groups allowed the integration of previous studies by identifying a series of relationships between nutrient loads and ecosystem functions. 相似文献
8.
Camilla Colombo Massimiliano Vasile Gianmarco Radice 《Celestial Mechanics and Dynamical Astronomy》2009,105(1-3):75-112
In this paper an optimisation algorithm based on Differential dynamic programming is applied to the design of rendezvous and fly-by trajectories to near Earth objects. Differential dynamic programming is a successive approximation technique that computes a feedback control law in correspondence of a fixed number of decision times. In this way the high dimensional problem characteristic of low-thrust optimisation is reduced into a series of small dimensional problems. The proposed method exploits the stage-wise approach to incorporate an adaptive refinement of the discretisation mesh within the optimisation process. A particular interpolation technique was used to preserve the feedback nature of the control law, thus improving robustness against some approximation errors introduced during the adaptation process. The algorithm implements global variations of the control law, which ensure a further increase in robustness. The results presented show how the proposed approach is capable of fully exploiting the multi-body dynamics of the problem; in fact, in one of the study cases, a fly-by of the Earth is scheduled, which was not included in the first guess solution. 相似文献
9.
Troy A. Henderson John L. Junkins Gianmarco Radice 《Celestial Mechanics and Dynamical Astronomy》2009,104(4):355-368
A complex exponential solution has been derived which unifies the elliptic and hyperbolic trajectories into a single set of
equations and provides an exact, analytical solution to the unperturbed, Keplerian two-body problem. The formulation eliminates
singularities associated with the elliptic and hyperbolic trajectories that arise from these orbits. Using this complex exponential
solution formulation, a variation of parameters formulation for the perturbed two-body problem has been derived. In this paper,
we present the analytical formulation of the complex exponential solution, numerical simulations, a comparison with classical
solution methods, and highlight the benefits of this approach compared with the classical developments.
Previously presented as AAS 07-136 at the 17th AAS/AIAA Spaceflight Mechanics Meeting Sedona, Arizona, AAS 08-206 and AAS
08-230 at the 18th AAS/AIAA Spaceflight Mechanics Meeting Galveston, Texas. 相似文献
10.