23,143 research outputs found

    Velocity Distribution and Cumulants in the Unsteady Uniform Longitudinal Flow of a Granular Gas

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    The uniform longitudinal flow is characterized by a linear longitudinal velocity field ux(x,t)=a(t)xu_x(x,t)=a(t)x, where a(t)=a0/(1+a0t)a(t)={a_0}/({1+a_0t}) is the strain rate, a uniform density n(t)‚ąĚa(t)n(t)\propto a(t), and a uniform granular temperature T(t)T(t). Direct simulation Monte Carlo solutions of the Boltzmann equation for inelastic hard spheres are presented for three (one positive and two negative) representative values of the initial strain rate a0a_0. Starting from different initial conditions, the temporal evolution of the reduced strain rate a‚ąó‚ąĚa0/Ta^*\propto a_0/\sqrt{T}, the non-Newtonian viscosity, the second and third velocity cumulants, and three independent marginal distribution functions has been recorded. Elimination of time in favor of the reduced strain rate a‚ąóa^* shows that, after a few collisions per particle, different initial states are attracted to common "hydrodynamic" curves. Strong deviations from Maxwellian properties are observed from the analysis of the cumulants and the marginal distributions.Comment: 8 pages; 4 figures; contributed paper at the 28th International Symposium on Rarefied Gas Dynamics (Zaragoza, Spain, July 9-13, 2012

    Contribution towards the knowledge of Psalidognathus Gray, 1831 (Coleoptera, Cerambycidae, Prioninae)

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    The species of the "modestus" group of the genus Psalidognathus Gray (Cerambycidae: Prioninae) (currently with four species and three subspecies), which are recognized mainly by the antennomeres without apical spines, are studied. Psalidognathus thomsoni Lameere, 1885 is revalidated as a species distinct from P. modestus Fries, 1833. Psalidognathus erythrocerus reichei Quentin and Villiers, 1983 and P. erythrocerus pubescens Quentin and Villiers, 1983 are considered as different species from P. erythrocerus Reiche, 1840. Psalidognathus colombianus Demelt, 1989 and Psalidognathus modestus chocoensis Salazar, 2005 are synonymized with P. modestus, syn. nov. Psalidognathus rufescens, although belonging to ‚Äúfriendii‚ÄĚ group, is redescribed and some remarks are added. Species redescribed: P. erythrocerus; P. modestus; P. reichei; P. rufescens; P. onorei Quentin and Villiers, 1983; and P. thomsoni. Psalidognathus cerberus sp. nov. is described from Colombia and Ecuador. A provisional key is provided to males of species of "modestus" group

    On the emergence of large and complex memory effects in nonequilibrium fluids

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    Control of cooling and heating processes is essential in many industrial and biological processes. In fact, the time evolution of an observable quantity may differ according to the previous history of the system. For example, a system that is being subject to cooling and then, at a given time twt_{w} for which the instantaneous temperature is T(tw)=TstT(t_w)=T_{\mathrm{st}}, is suddenly put in contact with a temperature source at TstT_{\mathrm{st}} may continue cooling down temporarily or, on the contrary, undergo a temperature rebound. According to current knowledge, there can be only one "spurious" and small peak/low. However, our results prove that, under certain conditions, more than one extremum may appear. Specifically, we have observed regions with two extrema and a critical point with three extrema. We have also detected cases where extraordinarily large extrema are observed, as large as the order of magnitude of the stationary value of the variable of interest. We show this by studying the thermal evolution of a low density set of macroscopic particles that do not preserve kinetic energy upon collision, i.e., a granular gas. We describe the mechanism that signals in this system the emergence of these complex and large memory effects, and explain why similar observations can be expected in a variety of systems.Comment: 15 pages, 5 figure

    Description of the female of Malukandra heterostyla (Lameere, 1902) (Coleoptera, Cerambycidae, Parandrinae)

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    The female of Malukandra heterostyla (Lameere, 1902) (Coleoptera: Cerambycidae) is described and figured for the first time. An identification key to Malukandra is provided.A f√™mea de Malukandra heterostyla (Lameere, 1902) (Coleoptera: Cerambycidae) √© descrita e figurada pela primeira vez. √Č fornecida uma chave de identifica√ß√£o para Malukandra

    Descriptions of females of Nothopleurus Lacordaire and Strongylaspis Thomson (Coleoptera: Cerambycidae: Prioninae: Macrotomini) with new distributional records

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    The female of Nothopleurus subsulcatus (Dalman, 1823) (Coleoptera: Cerambycidae: Prioninae: Macrotomini) is described for the first time, and the female of Strongylaspis bullata Bates, 1872 is redescribed. Color photographs of the habitus of both, and key characters for the former are included. New distributional records within Mexico for N. subsulcatus and Strongylaspis championi Bates, 1884 are given.A fêmea de Nothopleurus subsulcatus (Dalman, 1823) (Coleoptera: Cerambycidae: Prioninae: Macrotomini) é descrita pela primeira vez e a de Strongylaspis bullata Bates, 1872 é redescrita. São adicionadas figuras coloridas para as duas espécies e chave parcial para a N. subsulcatus. São fornecidos novos registros no México para N. subsulcatus e Strongylaspis championi Bates, 1884

    A new species of Villiersicometes Santos-Silva, 2003 (Coleoptera, Cerambycidae, Disteniinae)

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    Villiersicometes absalom sp. nov., a new species of Villiersicometes Santos-Silva, 2003 (Coleoptera, Cerambycidae, Disteniinae) is described from French Guiana. The species is illustrated and a key to the species of the genus is provided

    A Synopsis of Bolivian Polyrhaphis Audinet-Serville (Coleoptera, Cerambycidae, Lamiinae) with description of a new species

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    The Bolivian species of Polyrhaphis Audinet-Serville, 1835, (Coleoptera, Cerambycidae, Lamiinae) are reviewed and illustrated, with P. skillmani new species described. A key is presented to the six species recorded from Bolivia (P. angustata Buquet, 1853; P. argentina Lane, 1978; P. gracilis Bates, 1862; P. pilosa Lane, 1965; P. spinosa (Drury, 1773); and P. skillmani Wappes and Santos-Silva, new species). Their collection localities, based on recently identified specimens examined by the authors, are plotted to show the distribution of species, and displayed next to an ecoregion map of Bolivia to illustrate biogeographical information for Polyrhaphis.Se revisan e ilustran las especies bolivianas de Polyrhaphis Audinet-Serville, 1835, (Coleoptera, Cerambycidae, Lamiinae) con la descripción de P. skillmani especie nueva. Se presenta una clave para las seis especies conocidas de Bolivia (P. angustata Buquet, 1853; P. argentina Lane, 1978; P. gracilis Bates, 1862; P. pilosa Lane, 1965; P. spinosa (Drury, 1773); y P. skillmani Wappes y Santos-Silva especie nueva). Se trazan sobre un mapa las localidades de colecta, basadas en especímenes identificados recientemente y examinados por los autores, y se muestran junto a un mapa de las ecorregiones de Bolivia para ilustrar la información biogeográfica de Polyrhaphis

    The genus Aplagiognathus Thomson, 1861 (Coleoptera, Cerambycidae, Prioninae, Macrotomini)

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    Aplagiognathus Thomson, 1861 (Coleoptera, Cerambycidae, Prioninae, Macrotomini) and its two species, A. spinosus (Newman, 1840) and A. hybostoma Bates, 1879, are redescribed and figured. As the type of A. spinosus is apparently lost, a neotype for the species is designated herein as is a lectotype for A. hybostoma. Keys to the North and Central American genera of Macrotomini (excluding the West Indies) and to Aplagiognathus species are provided. Details on the numerous changes in the nomenclatural history of the genus are also chronicled
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