130,557 research outputs found
L’arboretum d' Harcourt
No full textPortevin Gaston. L’arboretum d' Harcourt. In: La Terre et La Vie, Revue d'Histoire naturelle, tome 4, n°1, 1934. pp. 49-50
A propos du centenaire de D. K. Tschernoff : rôle de la cristallographie dans les origines de la Métallographie
No full textPortevin Albert. A propos du centenaire de D. K. Tschernoff : rôle de la cristallographie dans les origines de la Métallographie. In: Bulletin de la Société française de Minéralogie, volume 62, 7-12, 1939. pp. 283-288
Efeito de Portevin-LeChatelier: Fenomenologia e Mecanismos
No full textThe phenomenology and the mechanisms of Portevin-LeChatelier effect in tension are studied for an aluminium alloy for electric conductors, ductalex. Portevin-LeChatelier effect is analyzed using charge-time plots and by Luders' band characteristics. A method to measure Luder's bands velocity and length using charge-time plots is developed. This method enables such measurements without using extensometers. Portevin-LeChatelier effect and associated Luders' bands are investigated as a function of temperatures, extension velocity and the mechanical state of material, particularly as a function of localized hardness increases and after ageing under tension and at various temperatures. The conclusion is taken that the Portevin-LeChatelier effect depends on the condition of dynamic aging if dislocations and on the materials's mechanic state but it is independent of the strain gradient. This last conclusion contradicts phenomenological models developed by some authorsAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1200 Lisboa / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga
Experimental studies of Portevin-Le Chatelier plastic instabilities in carbon-manganese steels by infrared pyrometry
No full textThe dynamic strain aging (DSA) phenomenon that occurs in some materials under certain temperature and strain rate conditions can cause plastic strain localization in the form of Portevin-Le Chatelier (PLC) bands. Carbon-manganese steels are used commonly and frequently in construction because of their ductility, low cost and ability to form mechanically. In these steels, the DSA phenomenon occurs for common quasi-static strain rates from 150 to 300 °C, which makes band observation complicated. PLC bands on a carbon-manganese steel that was sensitive to DSA were studied using an infrared camera. Specimen heating was achieved using an induction furnace (with an adapted coil inductor), which allows for temperature recording during tensile tests. Thermography with an infrared camera was used to estimate the band characteristics and increments in band plastic strain, which is an important parameter for material behavior identification necessary for DSA phenomenon modeling. This technique had been developed only for PLC phenomenon observation at ambient temperature on aluminum alloys. Band characteristics on the carbon-manganese steels have been compared with results obtained previously on aluminum alloys
Dissochaetus parallelus Portevin 1921
No full textD. parallelus Portevin, 1921: 535; Jeannel, 1936: 153 (assignment to group); Szymczakowski, 1969b: 411 (description of male genitalia); Salgado, 2005d: 980, 2010a: 298, 2018b: 421. Holotype male [a single specimen in original description, assumed as holotype] in MNHN [in Jeannel, 1936; original description refers to Grouvelle collection]. Type locality: Caracas, [Distrito Capital], Venezuela. Distribution: Ecuador: Pichincha Province; Peru: Cajamarca Department; Venezuela: Distrito Capital and Miranda State.Published as part of Peck, Stewart B., Gnaspini, Pedro & Newton, Alfred F., 2020, Updated catalog and generic keys of the Leiodidae (Insecta: Coleoptera) of the Neotropical region (" Latin America ": Mexico, the West Indies, and Central and South America), pp. 1-114 in Zootaxa 4741 (1) on page 28, DOI: 10.11646/zootaxa.4741.1.1, http://zenodo.org/record/377289
Dissochaetus latus Portevin 1907
No full textD. latus Portevin, 1907: 70; Jeannel, 1936: 152 (assignment to group); Salgado, 2014b: 96 (male types seen), Salgado, 2018a: 62 (partial description, distribution). Syntypes (3 specimens, sex and depository not given in original description), in MNHN [in Jeannel, 1936]. Type locality: “ Bolivia ” [Note: Jeannel, 1936 mentions “ Bolivia ” as type locality and then he mentions the localities “Mapiri, several specimens” in MNHN and “Coroico” in Pic collection; Salgado, 2014b examined, from MNHN, a male type from Mapiri and aedeagus preparations of two additional “type” specimens (he refers to “type species” but probably meant “type specimens”)]. Distribution: Bolivia: La Paz Department; Peru: Huánuco Department.Published as part of Peck, Stewart B., Gnaspini, Pedro & Newton, Alfred F., 2020, Updated catalog and generic keys of the Leiodidae (Insecta: Coleoptera) of the Neotropical region (" Latin America ": Mexico, the West Indies, and Central and South America), pp. 1-114 in Zootaxa 4741 (1) on page 26, DOI: 10.11646/zootaxa.4741.1.1, http://zenodo.org/record/377289
Dissochaetus geayi Portevin 1903
No full textD. geayi Portevin, 1903b: 329; Jeannel, 1936: 153 (assignment to group ovalis); Gnaspini, 1999: 375; Salgado, 2018a: 64 (assignment to group). Holotype female [a single specimen in original description, assumed as holotype] in MNHN. Type locality: Igarapé Lunier, Amapá State, Brazil [Note: When described, the locality belonged to French Guiana (as “Riviere Lunier”; Gnaspini, 1999: 375)]. Distribution: Brazil: Amapá State: known only from type locality.Published as part of Peck, Stewart B., Gnaspini, Pedro & Newton, Alfred F., 2020, Updated catalog and generic keys of the Leiodidae (Insecta: Coleoptera) of the Neotropical region (" Latin America ": Mexico, the West Indies, and Central and South America), pp. 1-114 in Zootaxa 4741 (1) on page 24, DOI: 10.11646/zootaxa.4741.1.1, http://zenodo.org/record/377289
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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