排序方式： 共有51条查询结果，搜索用时 78 毫秒
31.
Marco Belan Sergio de Ponte Daniela Tordella Silvano Massaglia Andrea Mignone Eberhard Bodenschatz Attilio Ferrari 《Astrophysics and Space Science》2011,336(1):9-14
Stars form in regions of the galaxy that are denser and cooler than the mean interstellar medium. These regions are called
Giant Molecular Clouds. At the beginning of their life, up to 105–106 years, stars accrete matter from their rich surrounding environment and are origin of a peculiar phenomenon that is the jet
emission. Jets from Young Stellar Objects (YSOs) are intensively studied by the astrophysical community by observations at
different wavelengths, analytical and numerical modeling and laboratory experiments. Indications about the jet propagation
and its resulting morphologies are here obtained by means of a combined study of hypersonic jets carried out both in the laboratory
and by numerical simulations. 相似文献
32.
33.
Rainfall as a trigger of shallow mass movements. A case study in the Dolomites, Italy 总被引：7，自引：0，他引：7
The article presents results of regional analysis on a historical basis correlating the occurrence of shallow mass movements
and disruptive events in time with precipitation trends. For the latter, different time-spans have been considered in an attempt
to find the most typical ones which might have triggered landslides. Research was carried out in the 850 km2 wide basin of the River Cordevole in the Dolomites (NE Italy). Data concerning slope movements and floods, which have affected
the area since the last century, were collected. Events which took place after 1920 have been correlated with the significant
pluviometric events recorded. In spite of the regionally high variability of both geological conditions and spatial distribution
of precipitation, three types of typical pluviometric trends related to an effective rainfall period of 15 days and to a peak
rainfall of 24–48 h preceding the onset of the movements were identified.
Received: 1 November 1996 · Accepted: 25 June 1997 相似文献
34.
The Impact of Human Recreational Activities in Marine Protected Areas: What Lessons Should Be Learnt in the Mediterranean Sea? 总被引：2，自引：0，他引：2
Marco Milazzo Renato Chemello Fabio Badalamenti Raffaele Camarda Silvano Riggio 《Marine Ecology》2002,23(S1):280-290
Abstract. The aesthetic appeal of marine reserves and the facilities provided, together with the increased public awareness of nature, all contribute to creating massive tourism in MPAs. Human activities are being changed inside MPAs in two ways: humans as top predators are generally being removed, but in turn they could come back at great numbers as visitors.
Many authors have studied the impact of visitors, and the results highlight that the consequences can be very substantial and may represent a severe threat to the overall diversity of marine communities. To date, the documented effects of human recreational activities on natural communities are restricted to assessing the consequences of trampling over intertidal and upper infralittoral areas, boat anchoring in seagrass meadows and tropical reefs, or SCUB A-diving.
In this paper we review the available literature world-wide on the effects of human recreational activities in marine communities. The objective is to address the extent of these impacts and to highlight the gaps of knowledge to be filled in order to optimise decision making on research, monitoring, and management of Mediterranean MPAs. A specific plan for managing tourism use in each Mediterranean MPA should be designated. These strategies should be implemented through education, training, and changes in legislation and policy. 相似文献
Many authors have studied the impact of visitors, and the results highlight that the consequences can be very substantial and may represent a severe threat to the overall diversity of marine communities. To date, the documented effects of human recreational activities on natural communities are restricted to assessing the consequences of trampling over intertidal and upper infralittoral areas, boat anchoring in seagrass meadows and tropical reefs, or SCUB A-diving.
In this paper we review the available literature world-wide on the effects of human recreational activities in marine communities. The objective is to address the extent of these impacts and to highlight the gaps of knowledge to be filled in order to optimise decision making on research, monitoring, and management of Mediterranean MPAs. A specific plan for managing tourism use in each Mediterranean MPA should be designated. These strategies should be implemented through education, training, and changes in legislation and policy. 相似文献
35.
Benthic Community and Sediment Types: A Structural Analysis 总被引：2，自引：0，他引：2
Eugenio Fresi Maria Cristina Gambi Silvano Focardi Roberto Bargagli Franco Baldi Lucia Falciai 《Marine Ecology》1983,4(2):101-121
Abstract. The distribution of the macrobenthic community, in relation to various physical and chemical characteristics of the sediment, was studied along the coast of Southern Tuscany (Central Tyrrhenian) in an area under the influence of the Ombrone River outflow.
The zonation of the benthos was found to be primarily under the control of a gradient of water movement, as is reflected by variations in the sediment structure from the coast to the open sea. This correlation is somehow influenced by secondary gradients such as the degree of mixing of the sediment and the deposition of terrigenous materials along the river plume. 相似文献
The zonation of the benthos was found to be primarily under the control of a gradient of water movement, as is reflected by variations in the sediment structure from the coast to the open sea. This correlation is somehow influenced by secondary gradients such as the degree of mixing of the sediment and the deposition of terrigenous materials along the river plume. 相似文献
36.
Removal of Pb2 ,Cu~(2 ),Zn~(2 )and Cd~(2 )from aqueous solutions by sorption on a natural phosphate rock(FAP)was investigated.The effects of the contact time and initial metal concentration were examined in the batch method.The percentage sorption of heavy metals from solution ranges generally between 50% and 99%.The amount of sorbed metal ions follows the order Cu>Pb>Cd>Zn. Heavy metal immobilization was attributed to both surface complexation of metal ions on the surface of FAP grains and partial dissolution and precipitation of a heavy metal-containing phosphate.The very low desorption ratio of heavy metals further supports the effectiveness of FAP as an alternative and low-cost material to remove toxic Pb~(2 ),Cu~(2 ),Zn~(2 )and Cd~(2 )from polluted waters. 相似文献
37.
Giovanardi Tommaso Girardi Vicente A. V. Correia Ciro T. Sinigoi Silvano Tassinari Colombo C. G. Mazzucchelli Maurizio 《Mineralogy and Petrology》2017,111(2):291-314
Mineralogy and Petrology - The Cana Brava complex is the northernmost of three layered complexes outcropping in the Goiás state (central Brasil). New field and geochemical evidences suggest... 相似文献
38.
Silvano Molendi 《Experimental Astronomy》2017,44(3):263-271
Background has played an important role in X-ray missions, limiting the exploitation of science data in several and sometimes unexpected ways. In this presentation I review past X-ray missions focusing on some important lessons we can learn from them. I then go on discussing prospects for overcoming background related limitations in future ones. 相似文献
39.
Alessandro Bemporad Paolo Pagano Silvio Giordano Silvano Fineschi 《Experimental Astronomy》2017,44(1):83-96
Observations of the solar corona in the FeXIV 530.3 nm “green line” have been very important in the past, and are planned for future coronagraphs on-board forthcoming space missions such as PROBA-3 and Aditya. For these instruments, a very important parameter to be optimized is the spectral width of the band-pass filter to be centred over the “green line”. Focusing on solar eruptions, motions occurring along the line of sight will Doppler shift the line profiles producing an emission that will partially fall out of the narrower pass-band, while broader pass-band will provide observations with reduced spectral purity. To address these issues, we performed numerical (MHD) simulation of CME emission in the “green line” and produced synthetic images assuming 4 different widths of the pass-band (Δλ = 20 Å, 10 Å, 5 Å, and 2 Å). It turns out that, as expected, during solar eruptions a significant fraction of “green line” emission will be lost using narrower filters; on the other hand these images will have a higher spectral purity and will contain emission coming from parcels of plasma expanding only along the plane of the sky. This will provide a better definition of single filamentary features and will help isolating single slices of plasma through the eruption, thus reducing the problem of superposition of different features along the line of sight and helping physical interpretation of limb events. For these reasons, we suggest to use narrower band passes (Δλ ≤ 2 Å) for the observations of solar eruptions with future coronagraphs. 相似文献
40.
Exploiting the use of physical information for the calibration of a lumped hydrological model 
下载免费PDF全文
下载免费PDF全文 Salvatore Manfreda Leonardo Mita Silvano Fortunato Dal Sasso Caterina Samela Leonardo Mancusi 《水文研究》2018,32(10):1420-1433
In hydrological modelling, the challenge is to identify an optimal strategy to exploit tools and available observations in order to enhance model reliability. The increasing availability of data promotes the use of new calibration techniques able to make use of additional information on river basins. In the present study, a lumped hydrological model—designed with the aim of utilizing remotely sensed data—is introduced and calibrated, adopting four different schemes that adopt, to varying extents, available physical information. The physically consistent conceptualization of the hydrological model used allowed development of a step by step calibration based on a combination of information, such as remotely sensed data describing snow cover, recession curves obtained from streamflow measurements, and time series of surface run‐off obtained with a baseflow mathematical filter applied to the streamflow time‐series. Results suggest that the use of physical information in the calibration procedure tends to increase model reliability with respect to approaches where the parameters are calibrated using an overall statistic based, considerably or exclusively, on streamflow data. 相似文献