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Wyszukujesz frazę "Lefebvre, B." wg kryterium: Autor


Wyświetlanie 1-6 z 6
Tytuł:
Stylophoran supertrees revisited
Autorzy:
Lefebvre, B
Powiązania:
https://bibliotekanauki.pl/articles/23222.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
supertree
Echinodermata
Mitrata
Paleozoic
Calcichordata
Stylophora
Ankyroida
Cornuta
paleontology
Opis:
Supertree analysis is a recent exploratory method that involves the simultaneous combination of two or more character−based source trees into a single consensus supertree. This method was recently applied by Ruta to a fossil group of enigmatic Palaeozoic forms, the stylophoran echinoderms. Ruta’s supertree suggested that mitrates are polyphyletic and originated from paraphyletic cornutes. Re−examination of Ruta’s data matrix strongly suggests that most source trees were based on dubious homologies resulting from theory−laden assumptions (calcichordate model) or superficial similarities (ankyroid scenario). A new supertree analysis was performed using a slightly corrected version of Ruta’s original combined matrix; the 70% majority−rule consensus of 24,168 most parsimonious supertrees suggests that mitrates are monophyletic and derived from paraphyletic cornutes. A second new supertree analysis was generated to test the influence of the pruning of three taxa in some calcichordate source trees; the 70% majority−rule consensus of 3,720 shortest supertrees indicates that both cornutes and mitrates are monophyletic and derived from a Ceratocystis−like ancestor. The two new supertree analyses demonstrate the dramatic influence of the relative contributions of each initial assumption of plate homologies (and underlying anatomical interpretations), in original source trees, on the final topology of supertrees.
Źródło:
Acta Palaeontologica Polonica; 2005, 50, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Conulariids from the Lower Ordovician of the southern Montagne Noire, France
Autorzy:
Van Iten, H.
Lefebvre, B.
Powiązania:
https://bibliotekanauki.pl/articles/2082222.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Cnidaria
Scyphozoa
Conulariida
Paleozoic
Gondwana
Europe
Opis:
The Tremadocian–Floian (Lower Ordovician) Saint-Chinian, La Maurerie, and Landeyran formations of the southern Montagne Noire (France) collectively contain at least two species of conulariids, namely Archaeoconularia cf. insignis and Conularia azaisi, the latter herein designated as the type species of the new genus, Galliconularia. Archaeoconularia insignis may also occur in the Lower Ordovician Fezouata Shale of southern Morocco, and an indeterminate species of this genus probably occurs in the Lower Ordovician Tonggao Formation of South China. Galliconularia azaisi differs from all other conulariids in having a raised facial midline and very fine, trochoidal transverse ribs which cross the midline ridge without interruption or diminution. In specimens preserving the outermost peridermal lamellae, the transverse ribs bear sub-microscopic nodes, and the broad interspaces are crossed by very slender interspace ridges. Finally, even though the Montagne Noire was part of the western Gondwanan passive margin during Cambro-Ordovician times, G. azaisi remains unknown outside of France.
Źródło:
Acta Palaeontologica Polonica; 2020, 65, 3; 629-639
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Morphology and palaeoecology of a new edrioblastoid from the Furongian of China
Autorzy:
Zhu, X.-J.
Zamora, S.
Lefebvre, B.
Powiązania:
https://bibliotekanauki.pl/articles/20097.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Opis:
A new edrioblastoid Cambroblastus guolensis is described from the Furongian (late Cambrian) Sandu Formation (South China). This represents the second occurrence of a Cambrian edrioblastoid, and the first ever reported from Asia, extending the palaeogeographic range of this very rare echinoderm grade. Surprisingly it preserves a complete stem and a distal holdfast suggesting edrioblastoids were hard substrate attachers living in soft bottom quiet environments.
Źródło:
Acta Palaeontologica Polonica; 2014, 59, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of the Shape of an Explosive Charge: Quantification of the Modification of the Pressure Field
Autorzy:
Simoens, B.
Lefebvre, M.
Powiązania:
https://bibliotekanauki.pl/articles/358774.pdf
Data publikacji:
2015
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
shape effect
emulsion explosive
C4
TNT
Opis:
Many scientific articles dealing with the detonation of explosive charges and their effects suppose that the charge is spherical and centrally initiated. Yet, when discussing the blast wave effect, the charge shape and the location of initiation could be as important as the composition or the mass of the considered explosive. Specifically, close to the charge, the shape may cause significant modifications of the pressure field compared to the predictions developed for spherical charges. Experiments have been carried out, using an emulsion explosive, TNT and C4, in order to quantify the shape effect. Unconfined, centrally initiated spherical and cylindrical charges with different length-to-diameter (L/D) ratios have been fired. The pressure in the median plane was recorded for different reduced distances. Results for spherical charges showed excellent agreement with well-known references. The expected change of the pressure field in the median plane of a cylindrical charge was observed, directly linked to the L/D ratio. Peak overpressure magnifications of up to almost 3 have been measured. The dimensions of the zone within which an increase of the blast wave effect is observed, have also been determined. A similar behaviour for TNT and C4 has been demonstrated; but a different behaviour has been observed for the emulsion explosive.
Źródło:
Central European Journal of Energetic Materials; 2015, 12, 2; 195-213
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Infuence of Different Parameters on the TNT-Equivalent of an Explosion
Autorzy:
Simoens, B.
Lefebvre, M. H.
Minami, F.
Powiązania:
https://bibliotekanauki.pl/articles/357938.pdf
Data publikacji:
2011
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
emulsion explosive
cylindrical charge
blast overpressure
blast impulse
Opis:
Emulsion explosives are used in a wide range of applications, amongst which some in closed vessels, where the properties at short range need to be known. A series of tests with spherical charges has been carried out to determine the TNT-equivalent at short range of an explosive emulsion based on both peak overpressure and impulse. Generally, the value is found to be constant over the considered range, with a value of 1 for overpressure and of 0.7 for impulse. In most common applications, explosive charges are not spherical. Experiments with cylindrical charges have been performed to study the infuence of (1) the shape of the charge (length-to-diameter ratio) and (2) the location of initiation (central or at one end). At the considered range, increasing L/D increases the peak overpressure and the impulse perpendicular to the axis, but decreases these effects on the axis. The central initiation causes the largest effects on the centreline. The initiation at one end causes a shift in the location of the peak overpressure, but the highest impulse remains on the centreline.
Źródło:
Central European Journal of Energetic Materials; 2011, 8, 1; 53-67
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Monte Carlo Analysis of Impact Ionization in Isolated-Gate InAs/AlSb High Electron Mobility Transistors
Autorzy:
Vasallo, B.
Rodilla, H.
González, T.
Lefebvre, E.
Moschetti, G.
Grahn, J.
Mateos, J.
Powiązania:
https://bibliotekanauki.pl/articles/1506159.pdf
Data publikacji:
2011-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
85.30.De
85.30.Tv
Opis:
We perform a physical analysis of the kink effect in InAs/AlSb high electron mobility transistors by means of a semiclassical 2D ensemble Monte Carlo simulator. Due to the small bandgap of InAs, InAs/AlSb high electron mobility transistors are very susceptible to suffer from impact ionization processes, with the subsequent hole transport through the structure, both implicated in the kink effect. When the drain-to-source voltage $V_{DS}$ is high enough for the onset of impact ionization, holes generated tend to pile up at the gate-drain side of the buffer. This occurs due to the valence-band energy barrier between the buffer and the channel. Because of this accumulation of positive charge, the channel is further opened and the drain current $I_{D}$ increases, leading to the kink effect in the I-V characteristics.
Źródło:
Acta Physica Polonica A; 2011, 119, 2; 222-224
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-6 z 6

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