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排序方式: 共有306条查询结果,搜索用时 15 毫秒
1.
Induced seismicity around the Tous New Dam (Spain) 总被引:2,自引:0,他引:2
2.
Gianluca Loffredo Filippo Frontera Damiano Pellicciotta Alessandro Pisa Vito Carassiti Stefano Chiozzi Federico Evangelisti Luca Landi Michele Melchiorri Stefano Squerzanti 《Experimental Astronomy》2005,20(1-3):413-420
We will report on the current configuration of the X-ray facility of the University of Ferrara recently used to perform reflectivity tests of mosaic crystals and to calibrate the experiment JEM–X aboard Integral. The facility is now located in the technological campus of the University of Ferrara in a new building (named LARIX laboratory= ̳LARge ̳Italian ̳X-ray facility) that includes a tunnel 100 m long with, on the sides, two large experimental rooms. The facility is being improved for determining the optical axis of mosaic crystals in Laue configuration, for calibrating Laue lenses and hard X-ray mirror prototypes. 相似文献
3.
Federico Ignacio Isla Orlando Mauricio Quiroz Londoño Luis Camilo Cortizo 《Environmental Earth Sciences》2018,77(17):610
The urban growth of the southern neighborhoods of Mar del Plata City provoked significant changes in the groundwater balance of the loessic sequences. These regional loessic levels with a significant portion of volcanic ash layers were reported subject to fluoride and nitrate concentrations. Residential houses pump from sands located 70 m depth and withdraw the sewages to depths less than 5 m. These effects cause significant local and seasonal (summer) increments of the water table outcropping via springs at certain unconformities of the coastal cliffs. A mathematical model was applied to analyze the water level lowering at the productive levels, while there is a decrease in the quality of the upper levels subject to waste discharges. Much of this groundwater flow is concentrated in unconformities between different types of sediments. Human activities have affected the aquifer dynamics increasing the groundwater pumping rates and the return velocity of the sewages. This should be considered in the management strategies of coastal hydric resources. 相似文献
4.
5.
Knowledge of marine geological environments in which shallow gas is accumulating is becoming increasingly important in global
studies of climate change because a measurable proportion of the total methane source comes from continental margins. Previous
studies have revealed that coastal environments represent important geological environments where microbial methane is being
generated, is accumulating, and is being released. In the Ría de Pontevedra, at least 4.5 km2 of seafloor in the innermost part of the ría is underlain by sediments containing natural gas. Seismic interpretation contributes
new findings for the definition of periods and geological environments in which the gas could have been generated, and is
accumulating and released in the Ría de Pontevedra. Groundtruthing the seismic data (facies, environments) makes it possible
to identify favourable geological environments for gas generation in the sedimentary infill of the Ría de Pontevedra. Sequence
stratigraphy based on high-resolution seismic profiles and post-Last Glacial Maximum sea-level records makes it possible to
establish the stratigraphic architecture of the ría and to define the periods in which gas could have been generated. The
results of this study show that the sedimentary infill is composed of a fifth-order sequence developed since the Last Glacial
Maximum. Within this sequence, gas appears to have accumulated in the Holocene deposits associated with the latest transgressive
and highstand system tracts. Seismic analysis shows that gas could have been generated in different geological environments
in the Ría de Pontevedra. If coastal environments at times of lower sea level were similar to those of the present, organic-rich
mud deposits (deposited mainly in lakes, estuaries and floodplains) could have survived transgression and remained buried
as potential gas sources in the inner part of the ría. 相似文献
6.
L. Bassani R. C. Butler A. J. Dean G. Di Cocco A. Della Ventura F. Perotti G. Villa 《Astrophysics and Space Science》1982,82(2):311-316
During a balloon flight in September 1979 of the MISO low-energy -ray telescope, the BL Lac-object MkN 501 was studied in the hard X-ray range above 30 keV and in the low energy -ray range up to 19 MeV. No statistically significant X- and -ray fluxes were detected. The implications of the upper limits obtained are discussed in the light of the relativistic jet theories recently proposed. 相似文献
7.
Some mechanisms which are expected to produce the growth of dust grains in the protosolar nebula are studied during the isothermal
and the adiabatic phase of the gravitational collapse.
Owing to the low sticking efficiency in the grain-grain collisions and also to the impossibility of gas capture by solid particles
in the physical environment considered, the main result is the production in about 106 yr of a set of particles similar in mass. The obtained mass limit (10−8–10−9 g) depends on the physical properties of the grains, and seems to be independent of the turbulence model used for the gas
motion. 相似文献
8.
Emilio J. Alfaro Federico Elias Jesús Cabrera-Caño 《Astrophysics and Space Science》2009,324(2-4):141-146
We perform a study into the spatial and kinematical distribution of young open clusters in the solar neighborhood, distinguishing between Gould Belt and local Galactic disk members. We use a previous estimate of the structural parameters of both systems obtained from a sample of O to B6 stars from Hipparcos. The two star-forming regions that dominate and give the Gould Belt its characteristic inclined shape show a striking difference in their content of star clusters: while Ori OB1 is richly populated by open clusters, not a single one can be found within the boundaries of Sco OB2. This is mirrored in velocity space, translating again into an abundance of clusters in the region of the kinematic space populated by the members of Ori OB1, and a marginal number of them associated with Sco OB2. We interpret all these differences by characterizing the Orion region as a cluster complex typically surrounded by a stellar halo, and the Sco-Cen region as an OB association in the outskirts of the complex. The different contents of star clusters, the different heights above the Galactic plane and the different residual velocities of Ori OB1 and Sco OB2 can be explained in terms of their relative position with respect to the density maximum of the Local Arm in the solar neighborhood. The origin of this feature could have been the interaction of a density wave with the local interstellar medium close to the Galactic co-rotation radius. 相似文献
9.
The notion of the “urban experiment” has become increasingly prevalent and popular as a guiding concept and trope used by both scholars and policymakers, as well as by corporate actors with a stake in the future of the city. In this paper, we critically engage with this emerging focus on “urban experiments”, and with its articulation through the associated concepts of “living labs”, “future labs”, “urban labs” and the like. A critical engagement with the notion of urban experimentation is now not only useful, but a necessity: we introduce seven specific areas that need critical attention when considering urban experiments: these are focused on normativity, crisis discourses, the definition of “experimental subjects”, boundaries and boundedness, historical precedents, “dark” experiments and non-human experimental agency. 相似文献
10.
Prediction of Stellar Atmospheric Parameters using Instance-Based Machine Learning and Genetic Algorithms 总被引:1,自引:0,他引:1
In this article we present a method for the automated prediction of stellar atmospheric parameters from spectral indices.
This method uses a genetic algorithm (GA) for the selection of relevant spectral indices and prototypical stars and predicts
their properties, using the k-nearest neighbors method (KNN). We have applied the method to predict the effective temperature,
surface gravity, metallicity, luminosity class and spectral class of stars from spectral indices. Our experimental results
show that the feature selection performed by the genetic algorithm reduces the running time of KNN up to 92%, and the predictive
accuracy error up to 35%.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献