1,723,187 research outputs found
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Potential hop reachable domain over surface of small bodies
No full textThe propagation of hopping trajectories with uncertainties is investigated over the surface of small celestial bodies. An intuitive geometric description of the accessible area referred to as the potential hop reachable domain, is provided when considering the uncertainties of the hopping rover’s state variables as well as the asteroid’s system parameters. A method to solve the envelope of the potential hop reachable domain is proposed by taking into account multi-hopping trajectories, which is applied to the asteroid 101955 Bennu. The influences of the state variables and asteroid physical parameters’ uncertainties on the propagation of hopping trajectories are discussed in detail. A comparison between the solved potential hop reachable domain and the Monte Carlo simulation is carried out to show the effectiveness of the method in this paper
Critical mass phenomena and blow-up behaviors of ground states in stationary second order mean-field games systems with decreasing cost
Full text linkThis paper is devoted to the study of Mean-field Games (MFG) systems in the mass-critical exponent case. We first derive the optimal Gagliardo-Nirenberg type inequality associated with the potential-free MFG system. Then, under some mild assumptions on the potential function, we show that there exists a critical mass M such that the MFG system admits a least-energy solution if and only if the total mass of population density M satisfies
Numerical Study on Low-Velocity Impact Between Asteroid Lander and Deformable Regolith
No full textInvestigating the impact process between the hopping lander and the regolith surfaces is of great significance for the
in situ asteroid explorations. The high-efficiency description of the regolith-interaction dynamics of the lander
remains to be analyzed. This paper presents a new method for effectively simulating the six-degree-of-freedom
motion of the lander when it impacts the regolith at a low velocity. The Bekker terramechanics theory is utilized for
calculating the impact force and torque, considering the notable deformable characteristic of the regolith.
Deformation of the regolith surfaces is tracked to simulate the formation of the impact crater. Parametric
simulations are implemented to verify this method by varying the regolith physical properties and the initial
lander state, respectively. The velocity and angular velocity of the lander are utilized as indicators for comparing
the hopping dynamics. Energy dissipation is discussed by calculating the restitution coefficients of different contact
scenarios
Wrinkling analysis of solar-photon sails
No full textThis paper regards small/midsize square sails on which a field of wrinkles appears owing to the necessary sail-membrane operations
before and during the deployment. We collected a large amount of data in our laboratory. Many ten thousands of measurements had
been statistically processed for characterizing some sail’s sampled membranes consisting of aluminized-polyimide layers ð2:5 þ 0:1Þlm
thin, and loaded at vertices. Such samples have exhibited area and orientation alterations, as a whole, which can affect the propulsive
acceleration of a sailcraft. Wrinkled-sail orientation has been given a thrust-specialized meaning for trajectory computation. Threedimensional
heliocentric minimum-time orbit transfer between Earth and Mercury orbits had been investigated. This had resulted in
wrinkled-sail sailcraft moving on trajectories remarkably different from those ones of the corresponding ideal unwrinkled-sail sailcraft.
Nevertheless, at least in the current framework, the most important result is that sail-wrinkled sailcraft’s interplanetary trajectories could
be optimized without resorting to stochastic differential equations
Random walk evaluation of Green's functions for groundwater flow in heterogeneous aquifers
Full text linkThe use of the Walk on Grid (WOG) approach for the reliable evaluation of the Green's function associated with groundwater flow scenarios in heterogeneous geologic media is explored. The study rests on the observation that, while the Green's function method (GFM) is one of the most significant and convenient approaches to tackle groundwater flow, Green's function evaluation is fraught with remarkable difficulties in the presence of realistic groundwater settings taking place in complex heterogeneous geologic formations. Here WOG approach is used to simulate pressure dissipation by lattice random walk and establish a quantitative relationship between space-time distribution of random walkers and the Green's function associated with the underlying flow problem. WOG-based Green's function method is tested (a) in three scenarios where analytical formulations are available for the Green's function and (b) in two groundwater flow systems with increased level of complexity. Our results show that WOG can (a) accurately evaluate the Green's function, being highly efficient when the latter can be analytically expressed in terms of infinite series; and (b) accurately and efficiently evaluate temporal evolutions of hydraulic heads at target locations in the heterogeneous systems. As such, a WOG-based approach can be employed as an efficient surrogate model in scenarios involving groundwater flow in complex heterogeneous domains
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