1,720,995 research outputs found
Statistical size scaling of compressive strength of quasi-brittle materials incorporating specimen length-to-diameter ratio effect
No full textStatistical size scaling of compressive strength of quasi-brittle materials demands to define a global stress parameter pertinent to the well accepted mechanism of shear stress induced fracture. The work proposes to adopt the resultant stress acting on the diagonal cross-section of a uniaxial compression specimen from one loading end to the other loading end in place of the conventional nominal compressive stress on two loading ends for statistical size scaling. As a result, the size effect on compressive strength is partitioned into specimen volume effect and specimen length-to-diameter ratio effect according to a recently developed formulation for the generalized weakest link statistics. This proposal is validated by three published data sets on the compressive strength of concrete, rock and four cohesive soils as preliminary case studies
Standardized Weibull statistics of ceramic strength
Full text linkIn order to estimate Weibull parameters in the Weibull statistical fracture theory as truly material properties independent of specimen geometry and loading mode, first the Weibull statistical fracture theory is transformed into the ordinary Weibull distribution function under certain approximation. Then the standardized format of ordinary Weibull distribution is introduced to enable Weibull modulus as the single parameter for estimation via the maximum likelihood method. The method of using standardized Weibull distribution for strength data synchronization and Weibull modulus estimation is validated by analyzing extensive strength data sets measured from uniaxial flexure, biaxial flexure and their combination, and from smooth and notched specimens. The technical path to estimate the scale parameter and threshold strength as material properties in the Weibull statistical fracture theory and effect of sample size on the estimation accuracy are also discussed
Statistics of ceramic strength: Use ordinary Weibull distribution function or Weibull statistical fracture theory?
No full text"Weibull statistics" for strength distribution analysis refers to either the ordinary Weibull distribution function or the Weibull statistical fracture theory. The ordinary Weibull distribution function is an empirical distribution function on an equal footing with other type of classical empirical distributions such as normal and log-normal distributions for fitting the statistical data of various random variables nonexclusive to materials strength. It has no explicit physical meaning and cannot be used for size scaling and prediction of strength. The Weibull statistical fracture theory is a weakest-link statistical fracture model for a solid with the strength distribution of an elemental volume being described by the ordinary Weibull distribution function. It has the capability of size scaling and prediction of strength for specimens with different geometries and different loading modes. The three-parameter Weibull statistical fracture theory in uniaxial flexure of prismatic beams is reformulated and validated by both numerical and real strength experiments of different ceramics
Использование неплавящегося вольфрамового электрода в среде аргона для поверхностного упрочнения конструкционных сталей
Full text linkЛебедев, Ю. М. Использование неплавящегося вольфрамового электрода в среде аргона для поверхностного упрочнения конструкционных сталей / Ю. М. Лебедев, Yu Zhishui, В. А. Мартыненко // Зб. наук. пр. НУК. – Миколаїв: НУК, 2007. – № 4 (415). – С. 58-64.Выполнены исследования структурных превращений и геометрических характеристик зоны упрочнения при поверхностной обработке неплавящимся вольфрамовым электродом в среде аргона. Рассмотрено влияние длины дуги на геометрические характеристики зоны упрочнения
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
Statistical size scaling of breakage strength of irregularly-shaped particles
Full text linkThe microdefects in a material responsible for fracture initiation in particle breakage may not always have a uniform spatial distribution. This work applies the power-law spatial flaw distribution based weakest link formulation of cumulative failure probability for statistical size scaling of breakage strength of irregularly-shaped particles. Four sets of published breakage strength data of different sized grains made of different materials including rock, basalt, sugar, and potash are adopted to validate the power-law spatial flaw distribution based weakest link model. Since the power-law spatial flaw distribution based weakest link model encompasses the uniform spatial flaw distribution based weakest link model as its subordinate member, while the Weibull statistical strength theory is a special case of the uniform spatial flaw distribution based weakest link model, this work extends the capability to investigate size scaling of particle breakage strength
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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