Logarithmic spiral trajectories generated by Solar sails     

Marco Bassetto  Lorenzo Niccolai  Alessandro A. Quarta  Giovanni Mengali 《Celestial Mechanics and Dynamical Astronomy》2018,130(2):18

Analytic solutions to continuous thrust-propelled trajectories are available in a few cases only. An interesting case is offered by the logarithmic spiral, that is, a trajectory characterized by a constant flight path angle and a fixed thrust vector direction in an orbital reference frame. The logarithmic spiral is important from a practical point of view, because it may be passively maintained by a Solar sail-based spacecraft. The aim of this paper is to provide a systematic study concerning the possibility of inserting a Solar sail-based spacecraft into a heliocentric logarithmic spiral trajectory without using any impulsive maneuver. The required conditions to be met by the sail in terms of attitude angle, propulsive performance, parking orbit characteristics, and initial position are thoroughly investigated. The closed-form variations of the osculating orbital parameters are analyzed, and the obtained analytical results are used for investigating the phasing maneuver of a Solar sail along an elliptic heliocentric orbit. In this mission scenario, the phasing orbit is composed of two symmetric logarithmic spiral trajectories connected with a coasting arc.  相似文献   

Multi-hazard assessment in Europe under climate change   总被引：2，自引：0，他引：2  

Giovanni Forzieri  Luc Feyen  Simone Russo  Michalis Vousdoukas  Lorenzo Alfieri  Stephen Outten  Mirco Migliavacca  Alessandra Bianchi  Rodrigo Rojas  Alba Cid 《Climatic change》2016,137(1-2):105-119

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Hexavalent chromium and some trace metals in concrete from buildings of different ages in northern Italy     

Eric Costeri  Giovanni Martinelli  Giampaolo Sighinolfi  Lorenzo Tassi  Paolo Zannini 《Environmental Earth Sciences》2016,75(21):1420

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Satellite radar data for back-analyzing a landslide event: the Ponzano (Central Italy) case study     

Lorenzo Solari  Federico Raspini  Matteo Del Soldato  Silvia Bianchini  Andrea Ciampalini  Federica Ferrigno  Stefano Tucci  Nicola Casagli 《Landslides》2018,15(4):773-782

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Effect of frictional heating and thermal advection on pre-seismic sliding: a numerical simulation using a rate-, state- and temperature-dependent friction law     

Salvatore de Lorenzo  Mariano Loddo 《Journal of Geodynamics》2010,49(1):1-13

Laboratory experiments on simulated faults in rocks clearly show the temperature dependence of dynamic rock friction. Since rocks surrounding faults are permeable, we have developed a numerical method to describe the thermo-mechanical evolution of the pre-seismic sliding phase which takes into account both the rate-, state- and temperature-dependent friction law and the heat advection term in the energy equation. We consider a laminar fluid motion perpendicular to a vertical fault plane and assume that fluids move away from the fault plane. A semi-analytical temperature solution which accounts for the variability of slip velocity and stress on the fault has been found. This solution has been generalized to the case of a time varying fluid velocity and then was used to include the thermal pressurization effect. After discretizing the temperature solution, the evolution of the system is obtained by the solution of a system of first order differential equations which allows us to determine the evolution of slip, slip rate, friction coefficient, effective normal stress, temperature and fluid velocity. The numerical solutions are found using a Runge-Kutta method with an adaptative stepsize control in time. When the thermal pressurization effects can be neglected, the heat advection effect gives rise to a delay, with respect to the purely conductive case, of the earthquake occurrence time. This delay increases with increasing permeability H of the system. When the thermal pressurization effects are taken into account the situation is opposite, i.e. the onset of instability tends to precede that of the purely conductive case. The advance in the time of occurrence of instability increases with increasing coefficient of thermal pressurization. In the small permeability range (H ≤ 10^?18 m²), the seismic moment and nucleation length of the pre-seismic phase are significantly smaller than those predicted by the purely conductive model.  相似文献   

Close range radar remote sensing of concrete degradation in a textile factory floor     

H. Lorenzo  V. Cullar  M. C. Hernndez 《Journal of Applied Geophysics》2001,47(3-4)

This paper describes a GPR study carried out with the aim of evaluating deterioration of concrete floors in a textile factory. In the past, production process waste was spilt onto the floor of the factory. A slow but continuous action from this waste on the concrete caused a significant variation in its porosity that can be detected by studying changes in the GPR reflected pulse. A simple synthetic model was developed in order to obtain information about how the response of the GPR antenna pulse is affected by changes in the porosity of concrete. It should also be taken into account the different conditions of the factory floor at the time of testing, as it had been isolated from the action of waste for many years. The heterogeneous conditions of the floor and the simplicity of the model used did not allow for an accurate estimate of the porosity; however, it was possible to map degraded areas of the floor in relationship to changes in the reflected signal. Core samples taken showed that some areas had concrete porosity of 15% and up to 25%, which is closer to that of sand than to concrete.  相似文献   

Structure and distribution of the benthic macrofauna on a Northwest African sandy beach close to a freshwater river discharge     

Abdellatif Chaouti  Isabella Colombini  Mario Fallaci  Elena Gagnarli  Lorenzo Chelazzi  & Abdellatif Bayed 《Marine Ecology》2008,29(S1):99-107

The effects of the freshwater discharge of the Oued Sebou River on the macroinfauna, was studied on the sandy beach of Mehdia through the analysis of the abiotic parameters and of the macrozoobenthos. In autumn 2002 and spring 2003, three beach sites, each with two transects, localized at 50, 3500 and 5720 m from the river mouth respectively, were studied. Positive correlations were recorded for beach slope and pH whereas negative ones were obtained for organic matter content and salinity at increasing distances from the river mouth. Significant differences between beach sites and seasons occurred for median grain size, organic matter content and pH. For each beach site, mean macroinfauna abundance varied between 30 and 100 ind.·m⁻² and in spring there was a significant correlation between this parameter and the increasing distance from the river mouth. No significant correlation was instead found between species richness and the increasing distance, although the farthest beach site from the mouth had the highest number of species during both seasons. The results indicated the importance of organic matter content and salinity for the macrofaunal abundance whereas the diversity indices were more affected by beach slope and grain size. The results showed that there was no clear spatial trend in compound indices of the macrofauna across the sampled sites and the influence of the river discharge of Sebou River did not seem to be significant and consistent on the macrobenthos of this mesotidal shore. Comparison with microtidal shores revealed the influence of the tidal excursion and swell characteristics on the response of the benthic structures of sandy beaches to discharges of freshwater.  相似文献   

Dynamical determination of the quadrupole mass moment of a white dwarf     

Lorenzo Iorio 《Astrophysics and Space Science》2007,310(1-2):73-76

In this paper we dynamically determine the quadrupole mass moment Q of the magnetic white dwarf WD 0137-349 by looking for deviations from the third Kepler law induced by Q in the orbital period of the recently discovered brown dwarf moving around it in a close 2-hr orbit. It turns out that a purely Newtonian model for the orbit of WD 0137-349B, assumed circular and equatorial, is adequate, given the present-day accuracy in knowing the orbital parameters of such a binary system. Our result is Q=(−1.5±0.9)×10⁴⁷ kg m² for i=35 deg. It is able to accommodate the 3-sigma significant discrepancy of (1.0±0.3)×10⁻⁸ s⁻² between the inverse square of the phenomenologically determined orbital period and the inverse square of the calculated Keplerian one. The impact of i, for which an interval Δ i of possible values close to 35 deg is considered, is investigated as well.  相似文献   

Erratum to “Juno,the angular momentum of Jupiter and the Lense–Thirring effect” [New Astronomy 15 (2010) 554–560]     

Lorenzo Iorio 《New Astronomy》2011,16(1):17-18

I correct some errors, disclosed in the aforementioned paper, concerning the long-term precessions due to the multipolar expansion of the gravitational potential of Jupiter. The conclusions of the paper turn out to be even enforced since the systematic uncertainties on the Lense–Thirring signature due to the zonals are slightly reduced.  相似文献   

Juno,the angular momentum of Jupiter and the Lense–Thirring effect     

Lorenzo Iorio 《New Astronomy》2010,15(6):554-560

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