2,646 research outputs found
Sharp local well-posedness for the "good" Boussinesq equation
No full textIn the present article, we prove the sharp local well-posedness and ill-posedness results for the "good" Boussinesq equation on 1d torus; the initial value problem is locally well-posed in H[−1/2](T) and ill-posed in H[s](T) for s (-3/8) given by Oh, Stefanov (2012). Similar ideas also establish the sharp local well-posedness in H[−1/2](R) and ill-posedness below H[−1/2] for the nonperiodic case, which improves the result of Tsugawa and the author (2010) in H[s](R) with s > (-1/2
Multiple transitions in rotating turbulent Rayleigh-Bénard convection
No full textSharp transitions between potentially different turbulent states are unexpected because one might think that they should be washed out by the prevailing intense fluctuations and short coherence lengths and times. Contrary to this expectation, we found a sequence of such transitions in turbulent rotating Rayleigh-Bénard convection as the rotation rate was increased. This phenomenon became most prominent at very large Rayleigh numbers up to 2 × 10^12 where the fluctuations are extremely vigorous. It was found in the heat transport as well as in the temperature gradient near the sample center. We conjecture that the transitions are between different large-scale structures which involve changes of symmetry and thus can not be gradual
Role of the strain-rate tensor in turbulent scalar-transport modeling
No full textWe examine the geometric orientation of the subfilter-scale scalar-flux vector in homogeneous isotropic turbulence. Vector orientation is determined using the eigenframe of the resolved strain-rate tensor. The Schmidt number is kept sufficiently large so as to leave the velocity field, and hence, the strain-rate tensor, unaltered by filtering in the viscous-convective subrange. Strong preferential alignment is observed for the case of Gaussian and box filters, whereas the sharp-spectral filter leads to close to a random orientation. The orientation angle obtained with the Gaussian and box filters is largely independent of the filter-width and the Schmidt number. It is shown that the alignment direction observed numerically using these two filters is predicted very well by the tensor-diffusivity model. Further a-priori tests indicate poor alignment of the Smagorinsky and stretched vortex model predictions with the exact subfilter flux
Hydrocanthus debilis Sharp 1882
No full textHydrocanthus debilis Sharp, 1882 Hydrocanthus debilis Sharp, 1882. Type locality: Brazil, Bahia / Amazonas, Amazonas Valley. Sharp 1882a: 281 (orig. descr.); Sharp 1882b: 8; Branden 1885: 18; Régimbart 1889: 263; Régimbart 1895: 343; Meinert 1901: 413; Régimbart 1904: 225; Zimmermann 1919: 118; Zimmermann 1920a: 14; Zimmermann 1920b: 225; Zimmermann 1921: 206; Zimmermann 1924: 1; Zimmermann 1925: 1; Zimmermann 1928: 167; Blackwelder 1944: 73; Ferreira-Jr. et al. 1998: 133; Benetti & Hamada 2003: 704; Ferreira-Jr. & Braga 2009: 325; Nilsson 2011: 22; Macchia et al. 2015: 113. Hydrocanthus (s. str.) debilis Sharp, 1882: Guignot 1957: 5; Young 1979: 2; Nilsson 2005: 111. Hydrocanthus (Guignocanthus) debilis Sharp, 1882: Young 1985: 98. Hydrocanthus finitimus Guignot, 1942. Type locality: French Guiana, Cayenne. Guignot 1942: 45 (orig. descr.); Spangler 1966: 387; Young 1985: 98 (N. Syn.). Hydrocanthus (s. str.) finitimus Guignot, 1942: Guignot 1956: 396; Guignot 1957: 5. Hydrocanthus rubiginosus Guignot, 1942 Syn. nov. Type locality: French Guiana, Cayenne. Guignot 1942: 47 (orig. descr.); Nilsson 2011: 26. Hydrocanthus (s. str.) rubiginosus Guignot, 1942: Guignot 1957: 5; Nilsson 2005: 111. Type material examined. Hydrocanthus debilis. Syntypes. “ BRAZIL, Bahia, 497, Sharp Coll. 1905–313” (1 ♂ 1 ♀ / BMNH). Hydrocanthus finitimus. Holotype ♂. “ GUIANA, Cayenne, III.1937, coll. Guignot ” (MNHN). Paratypes. “ GUIANA, Cayenne, III.1937, coll. Guignot ” (1 ♂ 2 ♀♀ / MNHN). Hydrocanthus rubiginosus. Holotype ♀ (Fig. 7). “ GUIANA, Cayenne, III.1937, coll. Guignot ” (MNHN). Paratypes. “ GUIANA, Cayenne, III.1937, coll. Guignot ” (2 ♀♀ / MNHN). Taxonomic notes. The comparison of type material of both taxa confirms that Hydrocanthus rubiginosus Guignot, 1942 is a junior subjective synonym of Hydrocanthus debilis Sharp, 1882. The particular combination of light reddish-brown pronotum and dark reddish-brown elytra with yellowish marmorations (Fig. 7b), prosternum laterally and medially setose, prosternal process entirely setose except along the apical margin, metaventrite laterally and apically setose (Figs 2d, 7c), and small size (4.00– 4.10 mm) is unique within the known females of this genus. Additional notes. In Nilsson’s catalogues (NILSSON 2005, 2011) the type locality for Hydrocanthus rubiginosus is reported as “ French Guiana> Abonnenc”, however in the original description (Guignot 1942), the author mentions “ Guyane française: Cayenne (Abonnenc)”; Abonnenc is reported as the collector (probably referring to Émile Abonnenc) not as the locality.Published as part of Guimarães, Bruno A. C., Ferreira-Jr, Nelson & Miller, Kelly B., 2018, On Hydrocanthus Say, 1823 (Coleoptera: Noteridae): description of a new species, two new synonyms and a key to Brazilian species, pp. 288-300 in Zootaxa 4508 (2) on pages 296-297, DOI: 10.11646/zootaxa.4508.2.10, http://zenodo.org/record/260695
Short-term responses of Dutch vacationers to a sharp increase in transport costs
No full textThis paper investigates vacationers’ short-term responses to a sharp increase in transport costs. It aims to (1) acquire an understanding of the relative popularity of the different types of responses among vacationers and (2) explore whether there are distinct market segments of vacationers that respond differently to a sharp increase in transport costs. Data are obtained from a novel, tailor-made questionnaire which was done in the Netherlands in 2012. Results show that no single response is either very popular or unpopular. Furthermore, using latent class cluster analysis, four market segments (classes) of vacationers are identified that have markedly distinct response patterns. It was found that Age and Income explain class membership.</p
Cryogenic receiver front-end with sharp skirt characteristics
No full textThis paper presents an experimental cryogenic receiver front-end (CRFE) with sharp skirt characteristics for mobile base stations. The CRFE comprises a high-temperature superconducting filter, a cryogenic low-noise amplifier, and a highly reliable cryostat that is very compact. The major characteristics of the proposed CRFE measured at 70 K are a centre frequency of 1.95 GHz, passband width of 20 MHz, sharp selectivity of 20 dB/100 kHz, 1.4 dB ripple, 31.3 dB average passband gain, and average passband equivalent noise temperature of 47.9 K. The CRFE weighs 19 kg and occupies 35 l. Random failure of the cryostat is also evaluated by a continuous operation test using four identical ones simultaneously. The cryostat used in the CRFE has a high reliability level of over five years of continuous maintenance-free operation
Synobius Sharp 1899
No full textSynobius Sharp Synobius Sharp 1899: 558. Discussion. Synobius Sharp is a little-known genus containing two described species, Synobius lobicollis Sharp, 1899, described from Panama, and Synobius lobatus (Grouvelle, 1896), from Brazil. Grouvelle originally described his species in Nausibius and, although differing from this genus in general facies, it does seem to be more closely related to it than any other in the family. Grouvelle (1913) transferred his species to Synobius remarking that an examination of the figures of S. lobicollis and S. lobatus showed these species were very closely related. Indeed, one of the labels that he attached to his holotype following the establishment of the new genus by Sharp, suggests he thought that they might be conspecific. Sharp, when describing the genus, remarked that it was apparently allied to Nausibius, Cathartus Reiche and Hapalips Reitter (the last of these is now placed in the Erotylidae). He stated that ‘… the greatest peculiarity of the genus is the peculiar, glabrous, rigid antennae.’ and drew attention to the fact that the structure of the sterna is that normal in the ‘Silvanides’. In his accompanying species description, Sharp anticipated a myrmecophilous or termitophilous habit for this insect. The habitat data on the majority of specimens examined (see descriptions below) tends to confirm an inquiline relationship as they were found in nests of bees of the genus Trigona Jurine (Apidae). Diagnosis. This genus (Fig. 1–17, 123), as represented by the two known species, may be distinguished from Nausibius by its antennae, which have a very small, narrow terminal segment; the pronotum, which is without lateral teeth, has a strong indentation before the anterior angles that form rounded and in front slightly declivous lobes; and the elytra, which lack obvious striae (an unusual condition in Nausibius although it does occur). The tarsi in Synobius are simple (Fig. 2) and there are no antennal grooves on the head. Obvious secondary sexual characters have not been found although with larger individuals, more transverse pronota may be indicative of females, as is often the case in Nausibius and some other silvanine genera. Apart from the types in the MNHN (S. lobatu s) and NHML (S. lobicollis) the species are known to the author only from a small number of specimens from Nevermann’s collection made in the 1930s and now mainly in the USNM, but also NHML and MIZP (just S. lobicollis in these last two depositories). Nevermann believed that his material represented two new species and labelled the specimens as such but did not publish descriptions. Comparison of Nevermann’s specimens with S. lobatus and S. lobicollis has shown that they represent these two extremely similar and very obviously closely related taxa, which are maintained here as distinct species and redescribed.Published as part of Halstead, David G. H., 2020, New and little known Coleoptera (Silvanidae: Silvaninae) from Central and South America, pp. 1-37 in Insecta Mundi 2020 (842) on pages 2-3, DOI: 10.5281/zenodo.535410
An improved ghost-cell sharp interface immersed boundary method with direct forcing for particle laden flows
No full textIn this paper, an accurate and stable sharp interface immersed boundary method(IBM) is presented for the direct numerical simulation of particle laden flows. The current IBM method is based on the direct-forcing method by incorporating the ghost-cell approach implicitly. An important feature of this IBM is the sharp representation of the solid surface, contrary to other variants of IBM for freely moving particles in which the solid surface is diffuse. Moreover, a correction of the diameter is not necessary for obtaining accurate results. The current ghost-cell IBM is stable because spurious oscillations incurred due to discontinuity in the pressure and velocity field in moving particle simulations is avoided. An algorithm for accurate torque computation is developed. The proposed algorithm is verified by comparison to an analytical expression and is shown to give a substantial improvement over the existing method. Finally, the present IBM is validated for various test cases of single and multi-particle systems and is shown to be accurate and robust for a wide range of flow conditions.Accepted Author ManuscriptIntensified Reaction and Separation System
Sharp bounds for cumulative distribution functions
No full textRatios of integrals can be bounded in terms of ratios of integrands under certain mono- tonicity conditions. This result, related with L?H?opital?s monotone rule, can be used to obtain sharp bounds for cumulative distribution functions. We consider the case of non- central cumulative gamma and beta distributions. Three different types of sharp bounds for the noncentral gamma distributions (also called Marcum functions) are obtained in terms of modified Bessel functions and one additional type of function: a second modified Bessel function, two error functions or one incomplete gamma function. For the noncen- tral beta case the bounds are expressed in terms of Kummer functions and one additional Kummer function or an incomplete beta function. These bounds improve previous results with respect to their range of application and/or its sharpness.The author acknowledges financial support from Ministerio de Economía y Competitividad (project
MTM2012-34787
Observability of Sharp Phase Transitions in Neutron Stars
No full text© 2019 Author(s). With central densities as high as 5-10 times the nuclear saturation density, neutron stars exhibit extreme conditions that cannot be observed elsewhere. They are ideal astrophysical laboratories for probing the composition and properties of cold, ultra-dense matter. We shall discuss taking into account currently available data from observation, how to reveal possible sharp phase transitions in dense neutron star cores
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