Short-term,linear, and non-linear local effects of the tides on the surface dynamics in a new,high-resolution model of the Mediterranean Sea circulation     

Palma  Massimiliano  Iacono  Roberto  Sannino  Gianmaria  Bargagli  Andrea  Carillo  Adriana  Fekete  Balazs M.  Lombardi  Emanuele  Napolitano  Ernesto  Pisacane  Giovanna  Struglia  Maria Vittoria 《Ocean Dynamics》2020,70(7):935-963

Ocean Dynamics - The tides in the Mediterranean Sea are generally weaker than in other regions of the world ocean, but are locally intensified in passages with complex bathymetry, such as the...  相似文献   

Grazing Management Plans improve pasture selection by cattle and forage quality in sub-alpine and alpine grasslands     

Marco PITTARELLO  Massimiliano PROBO  Elisa PEROTTI  Michele LONATI  Giampiero LOMBARDI  Simone RAVETTO ENRI 《山地科学学报》2019,(9)

Over the last decades, the reduction of manpower for herd management has led to an increase of continuous grazing systems(CGS) in the Italian Alps, which allow cattle to roam freely. Under CGS, due to high selectivity, livestock exploit grasslands unevenly, over-and under-using specific areas at the same time with negative effects on their conservation. To counteract these effects, a specific policy and management tool(i.e. Grazing Management Plan) has been implemented by Piedmont Region since 2010. The Grazing Management Plans are based on the implementation of rotational grazing systems(RGS), with animal stocking rate adjusted to balance it with grassland carrying capacity. A case study was conducted on alpine summer pastures to test the 5-year effects produced by the implementation of a Grazing Management Plan in grasslands formerly managed under several years of CGS on 1) the selection for different vegetation communities by cattle, 2) the abundance of oligo-, meso-, and eutrophic plant species(defined according to Landolt N indicator value), and 3) forage yield, quality, and palatability. A total of 193 vegetation surveys were carried out in 2011 and repeated in 2016. Cows were tracked yearly with Global Positioning System collars to assess their grazing selectivity, and forage Pastoral Value(PV) was computed to evaluate forage yield, quality, and palatability. Five years after RGS implementation, cow selectivity significantly decreased and the preference for the different vegetation communities was more balanced than under CGS. The abundance of meso-and eutrophic species increased, whereas oligotrophic ones decreased. Moreover, the abundance of moderately to highly palatable plant species increased, whereas non-palatable plant species decreased, with a consequent significant enhancement of the PV. Our findings indicate that the implementation of Grazing Management Plans can be considered a sustainable and effective management tool for improving pasture selection by cattle and forage quality in mountain pastures.  相似文献   

A detrital apatite fission‐track study of the CIROS‐2 sedimentary record: Tracing ice pathways in the Ross Sea area over the last 5 Ma     

Xia Li  Massimiliano Zattin  Valerio Olivetti 《地学学报》2019,31(3):271-280

The Ross Sea is a crucial area to investigate pathways of ice during the Cenozoic as it records the evolution of both the East and West Antarctic Ice Sheets. This work is based on detrital apatite fission track (AFT) data extracted from the sedimentary record of well CIROS‐2, which spans the last 5 Ma. The AFT data show a large range of ages, and most of the grains fit well with two main components that fall between 24 and 42 Ma and between 43 and 70 Ma, whereas the other components are not regularly distributed through the well, thus indicating a mixture of provenance from different areas along the Transantarctic Mountains. As a whole, our work suggests glacial expansion over the McMurdo Sound during the Pliocene, and ice periodically invading and retreating in Pleistocene.  相似文献   

Optimal low-thrust trajectories to asteroids through an algorithm based on differential dynamic programming     

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   

Detection of Flow Distortions and Systematic Errors in Sonic Anemometry Using the Planar Fit Method     

Renzo Richiardone  Elena Giampiccolo  Silvia Ferrarese  Massimiliano Manfrin 《Boundary-Layer Meteorology》2008,128(2):277-302

We describe the coordinate transformations that can be used to convert the velocity components measured by a set of sonic anemometers with time-dependent tilt fluctuations into a single, time-independent coordinate system. By applying the planar fit method (PFM) to each anemometer dataset, it is possible, for planar flows, to locate the flow plane at each measurement point and compare its orientation with the topography. Installation on a ship is also considered. An application of this method to intercomparison data has led to the detection of an instrument error due to a misalignment between the assembly of the sonic transducers and the anemometer pedestal. If this error occurs, pedestal levelling does not guarantee that measurements are unbiased. A correction method is proposed and the results of two experiments are shown. Flow planarity at different levels and flow distortion caused by the mast are highlighted. The influence of the error on the evaluation of the Reynolds stresses using PFM or the double rotation method and the triple rotation method is discussed and the tilt corrected stresses calculated using the three methods compared.  相似文献   

Changes of the susceptibility to lava flow invasion induced by morphological modifications of an active volcano: the case of Mount Etna,Italy     

Tarquini  Simone  Favalli  Massimiliano 《Natural Hazards》2010,54(2):537-546

Changes of the susceptibility to lava flow invasion at Mount Etna are quantified by using lava flow simulations on four Digital Elevation Models documenting the morphostructural modifications of the volcano in the time interval 1986–2007. The probabilistic code DOWNFLOW is used to derive the areas invaded by several thousands of lava flows obtaining, for each DEM, maps of the susceptibility to lava flow invasion and of the lava flow hazard. These maps show, for the first time, the evolution of these surficial properties with time, and render a quantitative image of the effects of topographic changes on the preferential lava flow drainage paths. The results illustrate how the emplacement of new lava flows and the growth of scoria cones affect the probability of inundation by lava flows. We conclude that the persistent activity of this volcano requires a frequent updating of the topography for a reliable lava flow hazard assessment.  相似文献