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81.
82.
Jürg Trösch Giorgio Salvadè Kurt Stocker 《Aquatic Sciences - Research Across Boundaries》1987,49(1):16-28
The northern and the southern basin of Lake Lugano, Switzerland, are separated by an artificial dam. The flow of the water
is not only influenced by the outflow of the northern basin but also by gravitational oscillations (seiches) of both basins.
A longperiodic peak around 100 minutes can be explained by a mathematical model. The interaction of the internal waves is
a coupled oscillation with a period of 74 hours.
相似文献
83.
Stefano Ceriani Neil S. Mancktelow Giorgio Pennacchioni 《Journal of Structural Geology》2003,25(12):2005-2021
The rotational behaviour of a rigid particle embedded in a linear viscous matrix undergoing cylindrical simple shear (Couette) flow was studied in 2D rock-analogue experiments. The influence of particle shape (elliptical vs. monoclinic), aspect ratio and the nature of the matrix/particle interface (lubricated vs. unlubricated) was investigated. Both matrix (PDMS) and lubricant (liquid soap) were linear viscous, with a viscosity ratio of ca. 104. Without lubricant, the rotational behaviour of all particles closely approximates the Jeffery theory. Lubricated monoclinic particles with the long diagonal initially parallel to the shear direction show back rotation and approach a stable position. Lubricated elliptical particles initially parallel to the shear direction also show back rotation but only transiently stabilize. Weak planar zones in the matrix adjacent to unlubricated elliptical particles do not induce backward rotation. In general for elliptical particles, rotation rate as a function of orientation depends on axial ratio and thickness of the lubricant mantle. For thick mantles (initially >10% of the volume of the particle), rotation rates are faster than Jeffery theory. For very thin mantles they are markedly slower compared with thick mantles, particularly when the long axis is nearly parallel to the shear direction. Rotation rates are never strictly zero, so true stabilization does not occur. However, for more elongate particles (axial RATIO=6) rotation rates are so slow that a very strong shape preferred orientation would develop in a lubricated elliptical particle population. In experiments, the volume of lubricant is constant and the thickness adjacent to the long side of the particle progressively decreases with increasing strain. In natural examples of porphyroclast systems, the weak mantle continually develops by recrystallization and/or cataclasis of the rigid clast core and a steady state between production and thinning could be attained, potentially leading to true stabilization for particles with a high axial ratio. 相似文献
84.
M. Focardi E. Pace M. Farina A. M. Di Giorgio J. Colomé Ferrer I. Ribas C. Sierra Roig L. Gesa Bote J. C. Morales J. Amiaux C. Cara J. L. Augurés E. Pascale G. Morgante V. Da Deppo M. Pancrazzi V. Noce S. Pezzuto M. Frericks F. Zwart G. Bishop K. Middleton P. Eccleston G. Micela G. Tinetti 《Experimental Astronomy》2018,45(1):1-20
In this paper we present the electromagnetic modeling and beam pattern measurements of a 16-elements ultra wideband sparse random test array for the low frequency instrument of the Square Kilometer Array telescope. We discuss the importance of a small array test platform for the development of technologies and techniques towards the final telescope, highlighting the most relevant aspects of its design. We also describe the electromagnetic simulations and modeling work as well as the embedded-element and array pattern measurements using an Unmanned Aerial Vehicle system. The latter are helpful both for the validation of the models and the design as well as for the future instrumental calibration of the telescope thanks to the stable, accurate and strong radio frequency signal transmitted by the UAV. At this stage of the design, these measurements have shown a general agreement between experimental results and numerical data and have revealed the localized effect of un-calibrated cable lengths in the inner side-lobes of the array pattern. 相似文献
85.
Armando Bazzani Stefano Marmi Giorgio Turchetti 《Celestial Mechanics and Dynamical Astronomy》1989,47(4):333-359
We prove that non resonant isochronous symplectic maps in a neighborhood of an elliptic fixed point are stable for exponentially long times with the inverse of the distance from the fixed point. In the proof we make use of the majorant series method together with an idea for optimizing remainder estimates first applied to Hamiltonian problems by Nekhoroshev. 相似文献
86.
Giorgio E. O. Giacaglia 《Celestial Mechanics and Dynamical Astronomy》1975,12(4):519-520
Using Sylvester's theorem on matrices, an elegant expression is obtained for the solutions of the restricted problem of three bodies in the neighborhood of the equilibrium points. 相似文献
87.
Paula M. Carreira José M. Marques M. Rosário Carvalho Giorgio Capasso Fausto Grassa 《Journal of Volcanology and Geothermal Research》2010,189(1-2):49-56
Na–HCO3–CO2-rich thermomineral waters issue in the N of Portugal, within the Galicia-Trás-os-Montes region, linked to a major NNE-trending fault, the so-called Penacova-Régua-Verin megalineament. Along this tectonic structure different occurrences of CO2-rich thermomineral waters are found: Chaves hot waters (67 °C) and also several cold (16.1 °C) CO2-rich waters. The δ2H and δ18O values of the thermomineral waters are similar to those of the local meteoric waters. The chemical composition of both hot and cold mineral waters suggests that water–rock reactions are mainly controlled by the amount of dissolved CO2 (g) rather than by the water temperature. Stable carbon isotope data indicate an external CO2 inorganic origin for the gas. δ13CCO2 values ranging between ? 7.2‰ and ? 5.1‰ are consistent with a two-component mixture between crustal and mantle-derived CO2. Such an assumption is supported by the 3He/4He ratios measured in the gas phase, are between 0.89 and 2.68 times the atmospheric ratio (Ra). These ratios which are higher than that those expected for a pure crustal origin (≈ 0.02 Ra), indicating that 10 to 30% of the He has originated from the upper mantle. Release of deep-seated fluids having a mantle-derived component in a region without recent volcanic activity indicates that extensive neo-tectonic structures originating during the Alpine Orogeny are still active (i.e., the Chaves Depression). 相似文献
88.
Andrea Cattaneo Andrea Rossotti Giorgio Pasquarè Anna Somigliana Domenico M. Cavallo 《Environmental Earth Sciences》2011,63(4):861-871
Since Etrurian age, the Viterbo Province (Central Italy) is famous for its ancient towns carved out of local ignimbrite deposits
which geologically represent the sedimentation of pumice-rich, volcano-related pyroclastic flows. Almost the entire study
area is geologically characterized by a thick succession of ignimbrites, tephra fallouts and lava flow deposits locally subjected
to zeolitization. Among zeolites, fibrous erionite represents a well-known health hazard and so this work aims at locating
and quantifying the presence of fibrous zeolites in volcanic deposits of the Viterbo area, suggesting at the same time a standard
operational procedure useful in other areas showing the same possible hazard. 41 samples collected in the Viterbo area were
analyzed by X-ray powder diffraction, optical and electron microscopy. Fibrous zeolites were detected in five samples and
quantified in amounts ranging from 0.35 to 1.66% vol. They generally occur in tetragonal or orthorhombic prismatic habit and
showed chemical composition mainly consistent with K-phillipsite. Fibrous zeolites occurred with aspect ratios (mean = 6.3),
comparable or lower than those of erionite fibers reported in previous studies and mean diameters >3 μm. 相似文献
89.
Giorgio Bartolini Valentina di Stefano Giampiero Maracchi Simone Orlandini 《Theoretical and Applied Climatology》2012,107(1-2):279-295
We created a new homogenized daily minimum and maximum temperature data set (1955–2007) for the central Mediterranean area of Tuscany (Italy). Yearly and seasonal long-term trends of some climatic and extreme climatic indices were investigated. The results highlighted a positive trend for mean temperature of about 0.9°C per 50 years with a slightly more pronounced increase in maximum temperature. Seasonal analysis revealed a by far much greater increase in summer (June, July, August) and spring (March, April, May) temperature in respect of autumn and winter, this finding consistent with most recent Mediterranean evidences. Warm extremes showed an overall tendency to increase, while a slight not significant decrease trend was found in regard to frost days and cold extremes. Comparisons with different patterns of Mediterranean warming confirmed the magnitude of recent very fast rise in temperature, especially during summer. This change could be due to last decades modifications of general circulation patterns and land–temperature, land–precipitation positive feedback processes dependent from soil moisture. All these results confirm that the Mediterranean is a region especially responsive and thus very vulnerable to climate change. 相似文献
90.
Giovanni Chiodini Stefano Caliro Giorgio Caramanna Domenico Granieri Carmine Minopoli Roberto Moretti Lavinia Perotta Guido Ventura 《Pure and Applied Geophysics》2006,163(4):759-780
The marine sector surrounding Panarea Island (Aeolian Islands, South Italy) is affected by widespread submarine emissions
of CO2 -rich gases and thermal water discharges which have been known since the Roman Age. On November 3rd, 2002 an anomalous degassing event affected the area, probably in response to a submarine explosion. The concentrations of
minor reactive gases (CO, CH4 and H2) of samples collected in November and December, 2002 show drastic compositional changes when compared to previous samples
collected from the same area in the 1980s. In particular the samples collected after the November 3rd phenomenon display relative increases in H2 and CO and a strong decrease in the CH4 contents, while other gas species show no significant change. The interaction of the original gas with seawater explains
the variable contents of CO2, H2S, N2, Ar and He which characterize the different samples, but cannot explain the large variations of CO, CH4 and H2 which are instead compatible with changes in the redox, temperature and pressure conditions of the system. Two models, both
implying an increasing input of magmatic fluids are compatible with the observed variations of minor reactive species. In
the first one, the input of magmatic fluids drives the hydrothermal system towards atypical (more oxidizing) redox conditions,
slowly pressurizing the system up to a critical state. In the second one, the hydrothermal system is flashed by the rising
high-T volcanic fluid, suddenly released by a magmatic body at depth. The two models have different implications for volcanic
surveillance and risk assessment: In the first case, the November 3rd event may represent both the culmination of a relatively slow process which caused the overpressurization of the hydrothermal
system and the beginning of a new phase of quiescence. The possible evolution of the second model is unforeseeable because
it is mainly related to the thermal, baric and compositional state of the deep magmatic system that is poorly known. 相似文献