1,720,989 research outputs found
Algorithms for solving crystal structure using texture
No full textPreferred orientation information can be used successfully to help the extraction of reliable structure factors from powder data to employ single crystal like structure solution methods. The methodology has been extended a little further and some new algorithms have been presented to simplify the procedure in a unique improved step. Using an approach derived from Rietveld Texture Analysis the simultaneous texture determination and structure factors extraction can be done
Object Oriented programming and fast computation techniques in Maud, a program for powder diffraction analysis written in Java
No full textReX: a computer program for structural analysis using powder diffraction data
No full textMulti-platform software has been developed for the analysis of powder diffraction data, with particular focus on structure solution. The program
provides a Rietveld optimization engine, with the possibility of refining parameters describing both the sample and the instrument model. Geometric
constraints such as rigid fragments and torsion angles can be defined for the atomic structure, to reduce the number of degrees of freedom of the model. An innovative hierarchical description of the asymmetric unit has been adopted, which allows, in principle, the definition of arbitrarily complex geometric relationships. Additionally, global optimization algorithms may be used in place of the standard nonlinear least squares, when particularly challenging problems are being faced
Crystal structure and texture refinement of polymers from diffraction images
No full textIn the present work, we present a methodology to analyze diffraction images of polymers to obtain crystal structure, texture and microstructural information. A laboratory image plate system has been used to collect diffraction images in transmission and reflection diffraction of aligned and strained fibers of different polymers.
The images have been processedby a structure refinement approach including a Rietveld Texture Analysis for each polymer
Rietveld structural and microstructural characterization of pharmaceutical products using the program Maud
No full textBrittle plus plastic deformation of gypsum aggregates experimentally deformed in torsion to high strains: Quantitative microstructural and texture analysis from optical and diffraction data
No full textThis contribution presents a quantitative microstructural analysis of a polycrystalline aggregate of gypsum, deformed in torsion (T = 70-90 °C) at γ (shear strain) ranging from 0 to 4.82. Quantitative microstructural analysis is used to compare the evolution of microstructures observed by optical microscope with those obtained from analysis of X-ray and neutron diffraction data. This analysis shows that during experimental deformation, gypsum accommodated strain by brittle and plastic deformation mechanisms, developing Riedel-like microfaults with plastic foliations and crystallographic preferred orientation (CPO). The relations of microstructures show that with increasing strain, the Riedel systems start from R planes with an angle of ≈30° to the Imposed Shear Plane. This angle decreases (5°-15°) when strain increases, and Y planes develop. Quantitative texture analysis (QTA) shows that S-foliations start developing at low γ and maintain their orientation up to high y, and that the most active slip system is the (010) along normal to (100) and the [001]-axis. Shape preferred orientation (SPO) of gypsum does not coincide with the theoretical orientation as it does not decrease with increasing strain. This discrepancy is explained by the role of the brittle shear planes that impose a back rotation to gypsum. No brittle to plastic transition occurs. But both plastic and brittle structures contemporaneously accommodate and localize strain
Early copper Alpine metallurgy
No full textA few of the oldest Alpine copper objects, dating from the Late Neolithic and the Early Copper Age of the Italian Eastern Alps (Alto Adige and Trentino), have been analyzed in order to interpret the manufacturing processes. Conventional metallographic analysis using optical microscopy with reflected light was employed to investigate two copper fragments from Isera La Torretta, Trento. State-of-the-art techniques of crystallographic texture analysis using neutron powder diffraction were used to study three copper axes from Alto Adige: The copper axe of the Iceman, and those from Castelrotto and Colma, Bolzano. The results of the experiments allowed full interpretation of the metallurgical techniques. The copper objects from Isera were rolled from sheets of native copper that had previously been slightly thinned at room temperature. The Iceman and the Colma copper axes were cast into bivalve molds and never underwent significant hot or cold working. The copper axe from Castelrotto shows a marked cube texture deriving from extensive recrystallization due to cold working followed by high
temperature annealing. All three axes are presently in the softened state. Neutron diffraction texture analysis proved to be an excellent innovative technique for the totally non-invasive metallographic analysis and interpretation of thick metal objects
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
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