Magnetic Fields in Star-Forming Regions: Theoretical Aspects     

Daniele Galli 《Astrophysics and Space Science》2005,295(1-2):43-51

We review the basic theoretical elements leading to our current understanding of the role of magnetic fields in the process of star formation. In particular, we concentrate on: (i) the relevance of the mass-to-flux ratio for the stability of molecular clouds; (ii) the consequences of magnetic flux leakage for the evolution of cloud cores; (iii) the phase of anisotropic dynamical collapse following the formation of strongly peaked density distributions; (iv) the mechanism of magnetic braking as a possible solution to the angular momentum problem in star formation.  相似文献   

Chemical and isotopic assessment in volcanic thermal waters: Cases of Ischia (Italy) and São Miguel (Azores,Portugal)     

Ignacio Morell  Antonio Pulido‐Bosch  Linda Daniele  José Virgilio Cruz 《水文研究》2008,22(22):4386-4399

Isotopic fractionation of ¹⁰B/¹¹B provides a sound tool for identifying hydrogeochemical processes in complex areas, owing to its ability to discriminate between various scenarios. In addition, the occurrence of boron as a minor element in areas of active volcanism allows its use in comparison with concentrations of other conservative or non‐conservative ions. This allows the detection of water mixtures of diverse origin and temperature, deep or shallow, including fresh water, seawater and even brines. This tool was applied in studies of the volcanic islands of Ischia and São Miguel, across widely differing geographical and climatic contexts. Five groups of waters have been identified in Ischia Island: marine, transition, hot carbonated, cold carbonated and fresh waters. For São Miguel Island the identified groups are cold carbonic, hot carbonic, boiling and acidic boiling waters. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

The Piànico tephra: an early Middle Pleistocene record of intraplate volcanism in the Mediterranean     

Daniele L. Pinti  Xavier Quidelleur  Pierre Lahitte  Cyril Aznar  Sergio Chiesa  Pierre-Yves Gillot 《地学学报》2003,15(3):176-186

ABSTRACT Distal tephra are a valuable record of the volcano-tectonic evolution of an area under study. Here, we document the case of the Early Middle Pleistocene rhyolitic tephra of Piànico, discovered in the Southern Italian Alps. The geochemical characteristics of Piànico are unique among the distal tephra outcropping in Italy and indicate an intraplate volcanism at the source. The alkali composition and trace elements show a striking resemblance with the rhyolitic complex of the Euganean Hills, located 170 km from Piànico. However, these rhyolites are much older (Oligocene). Alternatively, the source of this intraplate volcanic episode could be located in the southern Tyrrhenian Sea.  相似文献   

Climate change adaptation strategies for smallholder farmers in the Brazilian Sertão     

Jennifer Burney  Daniele Cesano  Jarrod Russell  Emilio Lèvre La Rovere  Thais Corral  Nereide Segala Coelho  Laise Santos 《Climatic change》2014,126(1-2):45-59

Climate models agree that semi-arid regions around the world are likely to experience increased rainfall variability and longer droughts in the coming decades. In regions dependent on agriculture, such changes threaten to aggravate existing food insecurity and economic underdevelopment, and to push migration to urban areas. In the Brazilian semi-arid region, the Sertão, farmers’ vulnerability to climate—past, present, and future—stems from several factors, including low yielding production practices and reliance on scarce and seasonally variable water resources. Using interpolated local climate data, we show that, since 1962, in the Bacia do Jacuípe—one of the poorest regions in the Sertão of Bahía state—average temperatures have increased?~?2 °C and rainfall has decreased?~?350 mm. Over the same time period, average milk productivity—the main rural economic activity in the county—has fallen while in Brazil and in Bahía as a whole milk productivity has increased dramatically. This paper teases apart the drivers of climate vulnerability of the Bacia do Jacuípe in relation to the rest of Bahía. We then present the results of a suite of pilot projects by Adapta Sertão, a coalition of organizations working to improve the adaptive capacity of farmers living in the semi-arid region. By testing a number of different technologies and arrangements at the farm level, Adapta Sertão has shown that interventions focused on balanced animal diets and efficient irrigation systems can help reduce (but not eliminate) the dependence of production systems from climate. They are thus viable adaptation strategies that should be tested at a larger scale, with implications for semi-arid regions worldwide.  相似文献   

Recent trends in seasonal and annual precipitation indices in Tuscany (Italy)     

Giorgio Bartolini  Alessandro Messeri  Daniele Grifoni  Daniele Mannini  Simone Orlandini 《Theoretical and Applied Climatology》2014,118(1-2):147-157

Global warming alters the hydrological cycle since a rise in temperature leads to an increase in the moisture-holding capacity of the atmosphere at a rate of about 7 %/°C. This fact can influence the global, but also local characteristics of precipitation, such as total amount and intensity. Therefore, it is important to study changes in rainfall regime in regions with complex orography, like Tuscany, where there are strong spatial gradients in precipitation amounts. The aim of this study is to look for temporal change in precipitation from 1955 to 2007 searching for spatial differences. Daily data of 21 meteorological stations were analyzed to identify trends in seasonal and annual precipitation indices. Cluster analysis applied to principal components was applied to identify homogeneous groups of stations. A decrease in precipitation was observed at annual time scale, during winter and spring, especially in northwestern areas. Wet days highlighted a decrease in all of Tuscany, due to the same seasons. In northern Tuscany, the decrease in rainfall amount was mainly determined by a lower frequency of rainy events which in turn caused a decrease in the occurrence of extreme daily precipitation events (75th, 90th, and 95th percentile). In central-southern Tuscany, no significant changes were observed except for an increase in precipitation fraction, due to extreme events and in mean daily total amount for wet days. These results are consistent with recent findings for the Mediterranean area and confirm the usefulness of cluster analysis for the analysis of the spatial distribution of precipitation.  相似文献   

Improving crop type determination using satellite imagery: A study for the Regione del Veneto,Italy     

Daniele Ehrlich  John Estes  Joseph Scepan 《国际地球制图》2013,28(2):35-47

The Regione del Veneto (Italy) is cooperating with the University of California, Santa Barbara and other researchers in Italy and the U.S.A. to develop a system of econometric crop production modeling. Five crops are to be included in this project: small grains (wheat and barley), corn, sugar beets, soybeans, orchards and vineyards. A critical part of the crop yield modeling process is the identification of crops using multispectral satellite data. This paper explores two strategies to improve crop classification accuracies: (1) use of ancillary data stored in digital format and (2) use of multitemporal data. Ancillary information stored on digital files were used in this research to remove (mask) non‐agricultural areas from satellite image data. Comparison between the classification of masked and unmasked images showed that improvement ranged from 3% to 26% depending on crop type. The multidate classification was performed by compiling an image of transformed spectral bands and three TM‐5 bands. The transformed bands were TM band 4 over TM band 3. Based on the work conducted in this study it is clear that crop type determination from satellite imagery is possible for small field agricultural areas such as those found in Italy.  相似文献   

A modeling language to support the interoperability of global navigation satellite systems     

Daniele Gianni  Joachim Fuchs  Pierluigi De Simone  Marco Lisi 《GPS Solutions》2013,17(2):175-198

The availability of multiple Global Navigation Satellite Systems (GNSS) will offer the opportunity to provide seamless navigation services and improved positioning performance. However, before this opportunity can be exploited, a number of issues need to be solved to ensure the compatibility and interoperability of existing GNSS. In particular, the GNSS interoperability can be technically defined as the capability of receivers to compute their global position using two or more GNSS signals. This capability can be more effectively achieved if Signal-In-Space interface specifications are available in a consistent, unambiguous, and possibly standard format, which can support engineers to design interoperable receivers. We aim to support the design of interoperable receivers with the introduction of the Interface Communication Modeling Language (ICML), a graphical language for the formal specification of Signal-In-Space interfaces. The ICML language enables receiver engineers to specify these interfaces at different levels of abstraction, such as analog signal or binary data. In addition, the ICML language also supports the specification of conversion routines between adjacent levels, for the representation of the dynamic aspects—e.g., convolution and encryption processes—of the interface specification. As such, the ICML language proposes an alternative format to textual-based interface specifications and can possibly integrate with the ongoing trend of the Model-based Systems Engineering approaches. We present the structure of the framework implementing the language and an example ICML-based specification for a simplified and reduced version of the Galileo Freely Accessible Navigation (F/NAV) message. The language metamodel is also attached for technical reference. An important caveat: no endorsement is made for the use of the ICML language for the official Galileo Signal-In-Space interface specification.  相似文献   

Current Behaviour and Dynamics of the Lowermost Italian Glacier (Montasio Occidentale,Julian Alps)     

Luca Carturan  Giovanni A. Baldassi  Aldino Bondesan  Simone Calligaro  Alberto Carton  Federico Cazorzi  Giancarlo Dalla Fontana  Roberto Francese  Alberto Guarnieri  Nicola Milan  Daniele Moro  Paolo Tarolli 《Geografiska Annaler: Series A, Physical Geography》2013,95(1):79-96

Smaller glaciers (<0.5 km²) react quickly to environmental changes and typically show a large scatter in their individual response. Accounting for these ice bodies is essential for assessing regional glacier change, given their high number and contribution to the total loss of glacier area in mountain regions. However, studying small glaciers using traditional techniques may be difficult or not feasible, and assessing their current activity and dynamics may be problematic. In this paper, we present an integrated approach for characterizing the current behaviour of a small, avalanche‐fed glacier at low altitude in the Italian Alps, combining geomorphological, geophysical and high‐resolution geodetic surveying with a terrestrial laser scanner. The glacier is still active and shows a detectable mass transfer from the accumulation area to the lower ablation area, which is covered by a thick debris mantle. The glacier owes its existence to the local topo‐climatic conditions, ensured by high rock walls which enhance accumulation by delivering avalanche snow and reduce ablation by providing topographic shading and regulating the debris budget of the glacier catchment. In the last several years the glacier has displayed peculiar behaviour compared with most glaciers of the European Alps, being close to equilibrium conditions in spite of warm ablation seasons. Proportionally small relative changes have also occurred since the Little Ice Age maximum. Compared with the majority of other Alpine glaciers, we infer for this glacier a lower sensitivity to air temperature and a higher sensitivity to precipitation, associated with important feedback from increasing debris cover during unfavourable periods.  相似文献   

The 2-D lattice theory of Flower Constellations     

Martín E. Avendaño  Jeremy J. Davis  Daniele Mortari 《Celestial Mechanics and Dynamical Astronomy》2013,116(4):325-337

The 2-D lattice theory of Flower Constellations, generalizing Harmonic Flower Constellations (the symmetric subset of Flower Constellations) as well as the Walker/ Mozhaev constellations, is presented here. This theory is a new general framework to design symmetric constellations using a $2\times 2$ 2 × 2 lattice matrix of integers or by its minimal representation, the Hermite normal form. From a geometrical point of view, the phasing of satellites is represented by a regular pattern (lattice) on a two-Dimensional torus. The 2-D lattice theory of Flower Constellations does not require any compatibility condition and uses a minimum set of integer parameters whose meaning are explored throughout the paper. This general minimum-parametrization framework allows us to obtain all symmetric distribution of satellites. Due to the $J_2$ J 2 effect this design framework is meant for circular orbits and for elliptical orbits at critical inclination, or to design elliptical constellations for the unperturbed Keplerian case.  相似文献   

The 3-D lattice theory of Flower Constellations     

Jeremy J. Davis  Martín E. Avendaño  Daniele Mortari 《Celestial Mechanics and Dynamical Astronomy》2013,116(4):339-356

Flower Constellations (FCs) have been extensively studied for use in optimal constellation design. The Harmonic FCs (HFCs) subset, representing the symmetric configurations, have recently been reformulated into 2-D Lattice Flower Constellations (2D-LFCs), encompassing the complete set of HFCs. Elliptic orbits are generally avoided due to the deleterious effects of Earth’s oblateness on the constellation, but here we present a novel concept for avoiding this problem and enabling more effective global coverage utilizing elliptic orbits. This new 3D Lattice Flower Constellations (3D-LFCs) framework generalizes the 2D-LFCs, Walker constellations, elliptical Walker constellations, and many of Draim’s global coverage constellations. Previous studies have shown FCs can provide improved performance in global navigation over existing Global Navigation Satellite Systems (GNSS). We found a 3D-LFC design that improved the average positioning accuracy by 3.5 % while reducing launch $\varDelta v$ Δ v requirements when compared to the existing Galileo GNSS constellation.  相似文献