1,721,015 research outputs found
Assessing the Robustness of Intelligence-Driven Reinforcement Learning
No full textRobustness to noise is of utmost importance in reinforcement learning systems, particularly in military contexts where high stakes and uncertain environments prevail. Noise and uncertainty are inherent features of military operations, arising from factors such as incomplete information, adversarial actions, or unpredictable battlefield conditions. In RL, noise can critically impact decision-making, mission success, and the safety of personnel. Reward machines offer a powerful tool to express complex reward structures in RL tasks, enabling the design of tailored reinforcement signals that align with mission objectives. This paper considers the problem of the robustness of intelligence-driven reinforcement learning based on reward machines. The preliminary results presented suggest the need for further research in evidential reasoning and learning to harden current state-of-the-art reinforcement learning approaches prior to being mission-critical-ready
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
Chemical and structural characterization of UICC crocidolite fibres from Koegas Mine, Northern Cape (South Africa)
Full text linkIn the present work we report the full structural and spectroscopic characterization of an UICC crocidolite standard sample, that is a fibrous riebeckite from Koegas Mine, Northern Cape (South Africa). The chemical composition was obtained by SEM-EDS and cation site partition was retrieved by complementing chemical, Mössbauer and X-ray powder diffraction data. Cell parameters, fractional coordinates, and site scattering for M(1), M(2), M(3), M(4) were refined using the Rietveld method. The UICC crocidolite standard sample shows the chemical formula ANa0.026BNa2.000C (Fe2+2.212Fe3+2.041Mg0.747)Σ=5.000T(Si7.950Al0.022)Σ=7.972O22O(3)(OH)2, very close to that of the end-member riebeckite A□BNa2C(Fe2+3Fe3+2)Σ=5TSi8O22O(3)(OH)2, the major difference being the Fe3+/Fetot ratio of 0.48, slightly higher than the ideal ratio of 0.40. Cation site distribution of the UICC crocidolite standard sample is: [Mg0.50Fe3+0.31Fe2+1.19]Σ=2.00 at M(1); [Mg0.10Fe3+1.60Fe2+0.30]Σ=2.00 at M(2); [Mg0.15Fe3+0.13Fe2+0.72]Σ=1.00 at M(3). Refined cell parameters are: a=9.73516(19) Å, b=18.0453(3) Å, c=5.32895(9) Å, β =103.5159(12) °, V=910.23(3) Å3. Quantitative Phase Analysis indicates that 93.7(3) wt% of the sample consists of crocidolite, the remaining being distributed among five different phases including magnetite and quartz
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
PLASTERS,PAINTINGS AND FLOORS AT POMPEII: ARCHAEOMETRICAL INVESTIGATIONS
No full textA meeting on the methods and application
of thin section petrographic analysis
to archaeological ceramics &
other cultural material
Fe3+ reduction during biotite melting in graphitic metapelites: another origin of CO2 in granulites
No full textThe Fe3+/Fetot of all Fe-bearing minerals has
been analysed by Mössbauer spectroscopy in a suite of
biotite-rich to biotite-free graphitic metapelite xenoliths,
proxies of an amphibolite-granulite transition through
progressive biotite melting. Biotite contains 9 to 16%
Fe3+/Fetot, whereas garnet, cordierite and ilmenite are
virtually Fe3+ -free (0–1% Fe3+/Fetot) in all samples,
regardless of biotite presence. Under relatively reducing
conditions (graphite-bearing assemblages), biotite is the
only carrier of Fe3+ during high-temperature metamorphism;
therefore, its disappearance by melting represents
an important event of iron reduction during granulite
formation, because haplogranitic melts usually incorporate
small amounts of ferric iron. Iron reduction is
accompanied by the oxidation of carbon and the
production of CO2, according to the redox reaction:
2Fe2O3(Bt) + C(Gr) ) 4FeO(Crd;Grt;Ilm;Opx) + CO2(fluid;melt;Crd):
Depending on the nature of the peritectic Fe-Mg mineral
produced (garnet, cordierite, orthopyroxene), the CO2
can either be present as a free fluid component, or be
completely stored within melt and cordierite. The oxidation
of graphite by iron reduction can account for the
in situ generation of CO2, implying a consequential rather
than causal role of CO2 in some granulites and
migmatites. This genetic model is relevant to graphitic
rocks more generally and may explain why CO2 is
present in some granulites although it is not required for
their formation
Synthesis and structural characterization of Fe3+-doped calcium hydroxyapatites: role of precursors and synthesis method
No full textThis work evaluates the role of Ca and P precursors and of two different preparation methods, ceramic and hydrothermal, in the synthesis of undoped- and Fe3+-doped hydroxyapatite (HA), and tests the Fe3+solubility limits in HA. Previous studies have noted that different synthesis conditions lead to different products in variable amounts and recent literature quotes the highest amount of Fe3+ substituting for Ca in the HA structure in the range 0.2-0.5 as a function of temperature. Samples were characterized by X-ray powder diffraction, Mössbauer and Infrared spectroscopies. The samples obtained by the ceramic method at 800° contain mixtures of B-type carbonate-apatite and other phosphates whose type and number depend on Ca and P precursors. Samples synthesized at higher temperatures contain mixtures of hydroxyapatite, tricalcium phosphate and of magnetic phases, as hematite and ferrite, whose relative amounts depend on nominal composition and thermal treatment. Samples obtained by a hydrothermal route are richer in HA phase with respect to the solid state one, even if the obtained HA percentage depends on the pH. Mössbauer results suggest that Fe3+ is randomly distributed between Ca1 and Ca2 sites. At the highest doping levels a reduction takes place with the formation of iron(II) and magnetite
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