1,721,023 research outputs found
Well-being in autoinflammatory diseases: impact of illness perception, coping strategies and the distribution of dependency
No full textKeplerian Map Theory for High-Fidelity Prediction of the Third-Body Perturbative Effect
Full text linkThis paper introduces an accurate model to monitor the motion of a particle of negligible mass under the simultaneous gravitational attraction of many celestial bodies, in the restricted three-body problem dynamical regime. It relies on the Lagrange planetary equations and applies the perturbation approach to the three-body potential. This approach benefits from a dynamical model based on the slow-varying Keplerian elements, with respect to the classical formulation of the N-body problem in Cartesian coordinates, which ensures a high computational efficiency. An extensive validation of the theory is presented, to test the accuracy of the model in different scenarios and prove its competitiveness from a computational point of view. The model is eventually adopted for computing a trajectory where the third-body perturbation plays a significant role; the target mission is a multi-flyby trajectory design in the Jupiter sphere of influence, where the gravity fields of the gaseous planet and the four Galilean moons are simultaneously considered
Optimal Active Debris Removal Sequence Identification Through Combined Debris Index Analysis and Long-Term Projection of the Orbital Environment
Full text linkApplication of Active Feedback Control for Investigation of Debris Mitigation Strategies on a Density-Based Model of the Population Evolution
Full text linkThe population of objects in space faced an unforeseeable growth in the last decades. There-fore, it is now imperative to reiterate the debris mitigation guidelines and reconsider the approach to the debris proliferation problem. Different counteractions are available to deal with the sit-uation. However, how to efficiently combine and apply these methods for sustainable use of the space environment is still an open question. To respond to this need, the GREEN SPECIES project, funded by a consolidator grant of the European Research Council, will develop a con-trolled model of the space debris population to define optimal mitigation policies. In its current version, the system exploits a statistical model in which debris and intact objects move in a one-dimensional domain in orbital radius and binned in spherical shells. The evolution of the environment is modelled in terms of the objects' density dynamics. The system includes the effect of atmospheric drag, sources as launches and in-orbit fragmentations, and artificial sink mechanisms such as post mission disposals and active debris removals. The resulting set of ordi-nary differential equations is integrated with a state-dependent linear feedback controller to tune different inputs and reach a predefined target. The novel appraoch exploits the benefits of control techniques to investigate the effectiveness of diversified rules in space and time to mitigate the debris proliferation and its risk to missions in low Earth orbit
Magnetic Field, Stress and Temperature Control of Phase Transitions in Ni55Mn20Ga25 Shape Memory Alloy
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Phase Space Description of the Debris’ Cloud Dynamics Through a Continuum Approach
Full text linkThis paper proposes a continuity equation-based debris' evolutionary model for the long-term propagation of fragments' clouds under atmospheric drag, J2 perturbation, solar radiation pressure and third-body perturbation. In particular, it focuses on enhancing the computational efficiency of the dynamical model. This purpose is achieved by cutting off some long-term effects of the perturbations, through averaging of the dynamics equations, and by deriving analytical expressions for the Earth's and Moon's ephemerides, through least squares fitting method. A new cost-free computation of the needed trace of the Jacobian for conservative forces is also proposed. The paper includes a validation phase, where the tool is applied to the modelling and propagation of two fragmentation clouds, characterised by a different dynamical regime, which allows to preliminarily identify some boundaries of applicability of the implemented dynamical model
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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