120,318 research outputs found
Carbon dioxide reforming of methane with Pt catalysts using microwave dielectric heating
No full textA 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Sound radiation from a generic bypass duct with bifurcations
No full textThe influence of bifurcations in an aero-engine bypass duct on noise radiation was investigated through high-order accurate three-dimensional numerical simulations. The physical process was described by a set of acoustic perturbation equations (APE), with a background mean flow. Four bifurcation arrangements, with an airfoil cross-section, were regularly placed in circumferential direction. Results of the simulations were compared with those of a clean duct case. A circumferential mode of m=12 with radial mode of n=1 and multi-n modes at a source frequency of 1547 Hz were set as acoustic inputs. Acoustic modes
interfered with the bifurcations resulting in a doubled circumferential mode pattern in the near field acoustic pressure distribution and slightly stronger sound
pressure level behind the bifurcations. Far field noise computations indicated 3.2 dB and 2.0 dB sound pressure level increases for radial mode of n=1 and multi-n
modes respectively. The bifurcations did not alter the radiation angle. A comparison was also made between APE and linearlised Euler equations (LEE). Results showed that the APE simulation produced almost identical far field sound
prediction to the LEE, with a small difference (< 0.8dB) at the main radiation peak angle
Existence and blow-up rate of large solutions of p(x)-Laplacian equations with gradient terms
No full textIn this paper we investigate boundary blow-up solutions of p(x)-Laplacian equations with gradient terms Our results extend the previous work of Y. Liang, Q.H. Zhang and C.S. Zhao, published in 2014, from the radial case to the non-radial setting, and of Q.H. Zhang and D.
Motreanu, appeared in 2016, from the assumption that the term involving the gradient is a small perturbation, to the harder case in which it is a large perturbation.We provide an exact estimate of the pointwise different behavior of the solutions near the boundary in terms of of the distance of a point x to the boundary of the domain,say d(x). and in terms of the growth of the exponents. Furthermore,
the comparison principle is no longer applicable in our context, since the forcing term f is not assumed to be monotone in this paper
GAT-DNS: DNS Multivariate Time Series Prediction Model Based on Graph Attention Network
No full textAs one of the most basic services of the Internet, DNS has suffered a lot of attacks. Existing attack detection methods rely on the learning of malicious samples, so it is difficult to detect new attacks and long-period attacks. This paper transforms the DNS data flow into time series, and proposes a DNS anomaly detection method based on graph attention network and graph embedding (GAT-DNS). GAT-DNS establishes a multivariate time series model to depict the DNS service status. When the actual flow of a feature exceeds the predicted range, it is considered that abnormal DNS behavior is found. In this paper, vertex dependency is proposed to describe the dependency between features. The features with high vertex dependency values are deleted to achieve model compression. This improves the system efficiency. Experiments on open data sets show that compared with the latest AD-Bop and QLAD methods, GAT-DNS method not only improves the precision, recall and F1 value, but also improves the time efficiency of the model
Selliguea wusugongii Liang Zhang, X. P. Fan & Li Bing Zhang 2021, sp. nov.
No full text<i>Selliguea wusugongii</i> Liang Zhang, X.P.Fan & Li Bing Zhang, <i>sp. nov.</i> (Figs. 2 & 3). <p> Type:— CHINA. Xizang: Medog County, Beibeng Xiang, Deergong Village, elev. 1700–1800 m, 29°10’N / 95°08’E, on tree trunk in broadleaved evergreen forests of primary vegetation, 24 November 2018, <i>Liang Zhang 2955</i> (holotype KUN1497728!; isotypes KUN & CDBI!).</p> <p> <b>Diagnosis:—</b> <i>Selliguea wusugongii</i> is most similar to <i>S. stenopteris</i> by having narrow lamina and marginal and rounded sori, but differs the latter in having scales considerably more scattered on the rhizome and a monomorphic graminiform frond up to 40 cm long.</p> <p> <b>Plants</b> perennial, evergreen, epiphytic. <b>Rhizome</b> long creeping, ca. 0.8–1.2 mm in diam., dark brown when dry, with many hairy roots and a few short phyllopodia, internodes of phyllopodia 0.8–1.4 cm long, cross section of rhizome with 4–10 vascular strands (amount of vascular strands are quite variable from different individuals, see C, D, E of figure 3), sclerenchyma strands 13–25; rhizome and phyllopodia distinct scaly, <b>rhizome scales</b> lanceolate, scattered and exserted, 1.6–4.2 mm long, 1.1–1.3 mm wide at the widest, light brown, peltate, basal parts appressed, upper middle parts spreading, apex acuminate, margin entire, scales of phyllopodia similar to rhizome scales but smaller. <b>Frond</b> monomorphic, (11–) 25–40 cm tall, 0.8–1.1 mm wide; <b>petiole</b> stramineous, wingless part (1.2–) 3.5–9 cm long, 0.4–0.6 mm wide, with a few scales on base, slighted grooved, gradually winged at distal part. <b>Lamina</b> long needlelike, simple, slightly grooved adaxially, margins entire and revolute when dry, (9–) 21–32 cm long, 0.8–1.1 mm wide, widest at middle of lamina, papery, dark green in the wild, light green when dry, glabrous; <b>midrib</b> stramineous when dry, slightly raised, up to half width of laminae, sometimes partially covered by revolute laminae. <b>Veins</b> invisible. <b>Sori</b> on upper part of lamina, oblong, (4)6–8 on each side of midrib, 2.0– 2.3 mm long, 0.6–0.8 mm wide, at least covering half width of laminae, slightly out of lamina margins, basal pairs of sori nearly opposite, upwards alternate and distant, ca. 0.4–1.1 cm apart from one another. <b>Paraphyses</b> absent.</p> <p> <b>Geographical distribution</b>:— Currently, <i>Selliguea wusugongii</i> is found in Medog County, Xizang, China, and nearby regions, may represent a species endemic to southeast Xizang.</p> <p> <b>Ecology:</b> — <i>Selliguea wusugongii</i> was observed to grow on tree trunks in primary forests, at elevations between 1700 and 1800 m. The rhizomes are partially covered by some mosses such as <i>Metzgeria conjugata</i> Lindberg (1875: 495).</p> <p> <b>IUCN Red List category:</b> —Only two populations with about 22 individuals of <i>Selliguea wusugongii</i> were found. The status of the new species can be classified as Critically Endangered (CR), based on current information and following the IUCN (The International Union for Conservation of Nature and Natural Resources) guidelines (IUCN, 2019), but more extensive fieldwork focusing on the tree trunks in the nearby mountains is needed to accurately assess its conservation status.</p> <p> <b>Etymology:</b> <i>—</i> Named in honor of Prof. Wu Sugong, pteridologist based at KUN, for his contributions to the taxonomy of ferns, and especially to the fern flora of Xizang.</p> <p> <b>Taxonomic notes</b>: <i>—</i> Two collections from a single locality (R.S. Rao 17766 & 1766A) from the adjacent area of Medog County were referred to <i>Selliguea bisulcata</i> by Dixit & Nair (1977), which should be conspecific to <i>S. wusugongii.</i> These were discussed by Fraser-Jenkins (2008, 2012) and re-identified as either <i>S. enervis</i> or <i>S. subsparsa</i>, and were assigned the IUCN category of Critically Endangered (CR). Fraser-Jenkins (pers. comm. 11.2020) now identifies them as being the same as <i>S. wusugongii</i>.</p>Published as part of <i>Fan, Xue-Ping, Zhang, Lin, Zhang, Li-Bing & Zhang, Liang, 2021, Selliguea wusugongii (Polypodiaceae), a new fern species from southeastern Xizang, China based on morphological and molecular evidence, pp. 57-68 in Phytotaxa 480 (1)</i> on pages 59-63, DOI: 10.11646/phytotaxa.480.1.5, <a href="http://zenodo.org/record/5414463">http://zenodo.org/record/5414463</a>
Stoichiometry patterns in the androdioecious Acer tegmentosum
No full textCITATION: Zhang, X., et al. 2016. Stoichiometry patterns in the androdioecious Acer tegmentosum. Scientific Reports, 6:35022, doi:10.1038/srep35022.The original publication is available at http://www.nature.com/srepENGLISH ABSTRACT: This study evaluates stoichiometry patterns in the androdioecious Acer tegmentosum, a species characterized by a rare reproductive system where males and hermaphrodites coexist. Altogether 31 hermaphrodites and 29 male plants were harvested and samples of leaves, current-year shoots, branches and coarse roots were analyzed to explore gender differences in biomass, C, N and P concentrations of these four components. The nitrogen to phosphorus relationship of each component was examined using SMA estimates. Males had significantly greater amounts of leaf and coarse root dry matter content than hermaphrodites. C, N and P stoichiometry differed significantly between genders, especially in the newly emerging vegetative components (leaves and shoots). Males had higher C/N and C/P ratios in current-year shoots and lower C/P ratios in leaves and branches. Hermaphrodites had higher N/P ratios in the leaves and branches. Males had higher rates of increase in leaf P content than hermaphrodites. This study suggests that stoichiometry patterns may be significantly affected by gender.https://www.nature.com/articles/srep35022Publisher's versio
Relations between x-ray timing features and spectral parameters of galactic black hole x-ray binaries
No full textWe present a study of correlations between spectral and timing parameters for a sample of black hole X-ray binary candidates. Data are taken from GX
339-4, H 1743-322, and XTE J1650-500, as the Rossi X-ray Timing Explorer
(RXTE) observed complete outbursts of these sources. In our study we investigate outbursts that happened before the end of 2009 to make use of the high-energy coverage of the HEXTE detector and select observations that
show a certain type of quasi-periodic oscillations (type-C QPOs). The spectral parameters are derived using the empirical convolution model simpl to model the Comptonized component of the emission together with a disc blackbody for the emission of the accretion disc. Additional spectral features, namely a reflection component, a high-energy cut-off, and excess emission at 6.4 keV, are taken into account. Our investigations confirm the known positive
correlation between photon index and centroid frequency of the QPOs and reveal an anti-correlation between the fraction of up-scattered photons and the QPO frequency. We show that both correlations behave as expected in the “sombrero”
geometry. Furthermore, we find that during outburst decay the correlation between photon index and QPO frequency follow a general track, independent of individual outbursts
Magnetic properties and giant magnetoresistance in magnetic granular Cox Cu100-x alloys
No full textMagnetic granular CoxCu100-x alloys (x = 5-20) have been prepared by melt-spinning acid subsequently annealing at 450 degrees C for 30 min, which is most appropriate for obtaining the largest MR change with magnetic field in each sample. The highest magnetoresistance (MR) change of 42.5% was observed in annealed Co15CU85 ribbons. Based on the superparamagnetic assumption, the average size of Co particles embedded in a Cu-rich matrix for different samples, ranging from 3.5 to 5.5 nm, has been estimated by simulating the magnetization curves at room temperature which is higher than the blocking temperature T-B for each sample. The value of MR change was found to strongly depend on the Co composition and annealing temperature
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