89,193 research outputs found
ZHANG, F. & LIU, X-W. (2009) A review of the subgenus Diestrammena (Gymnaeta) from China (Orthoptera: Rhaphidophoridae Aemodogryllinae). Zootaxa, 2272, 21-36.
No full textZhang, F., Liu, X-W. (2009): ZHANG, F. & LIU, X-W. (2009) A review of the subgenus Diestrammena (Gymnaeta) from China (Orthoptera: Rhaphidophoridae Aemodogryllinae). Zootaxa, 2272, 21-36. Zootaxa 2288 (1): 68, DOI: 10.11646/zootaxa.2288.1.5, URL: http://dx.doi.org/10.11646/zootaxa.2288.1.
Dataset for: The importance of the heel effect in X-ray CT imaging of soils
No full textDataset supports the paper K. Liu, R. Boardman, M. Mavrogordato, F. A. Loveridge, and W. Powrie 'The importance of the heel effect in X-ray CT imaging of soils' in Environmental Geotechnics, https://doi.org/10.1680/jenge.20.00048</span
A 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
UvA-DARE (Digital Academic Repository) Link to publication Citation for published version (APA)
No full textThe real role of active-shell in enhancing the luminescence of lanthanides doped nanomaterials Wu, F.; Liu, X.; Kong, X.; Zhang, Y.; Tu, L.; Liu, K.; Song, S.; Zhang, H
Operando X-ray absorption spectroscopy investigations on NaxNi1/3Fe1/3Mn1/3O2 positive electrode materials for sodium and sodium ion batteries
No full textNaxMn1/3Fe1/3Ni1/3O2 (x = 2/3 and 1) layered oxides are synthesized and applied as positive electrode materials for sodium batteries. The crystal structure of the material changes from the O3 single phase to P2/O3 mixed phases as the Na content decreases from 1 to 2/3. The mixed-phases Na2/3Mn1/3Fe1/3Ni1/3O2 shows superior cycling performance compared to the single-phase NaMn1/3Fe1/3Ni1/3O2 due to different redox process and structural change that are demonstrated by operando X-ray absorption spectroscopy (XAS). The Na2/3Mn1/3Fe1/3Ni1/3O2 experiences redox reactions of Ni3+|Ni4+ and Fe3+|Fe4+ with inactive Mn ions during the charge/discharge processes, while the NaMn1/3Fe1/3Ni1/3O2 undergoes deeper redox reactions from Ni2+|Ni3+|Ni4+ and Fe3+|Fe4+ that Mn ions are irreversibly oxidized to Mn4+ in the 1st charge process. In addition, the mixed-phases material has smaller changes in the transition metal oxygen bond lengths during cycling, corresponding to less distortions of TMO6 units in the crystal structure. The better reversibility of the redox reactions and the occurrence of less structural changes are both responsible for the enhanced cycling performance obtained from the mixed-phases material compared to the single-phase material. These results strengthen the understanding of interactions of transition metals in the layered cathode and provide guidelines for designing positive electrode materials for sodium batteries
Influence of ac ageing on space charge dynamics in LDPE
No full textPolymeric materials have been widely used as insulation in power industry due to their excellent electrical properties. However, these properties deteriorate in time irreversibly when the material is subjected to electric stress. Although space charge is believed to play an important role in ac ageing, exact mechanisms are poorly understood due to very limited experimental data. In the present work efforts have been made to investigate the influence of ac ageing on space charge dynamics in low-density polyethylene (LDPE). LDPE films with 200mm were aged at 50 kV/mm at 50 Hz for various times at ambient temperature. Space charge dynamics in the samples prior to and after ageing were monitored using the pulsed electroacoustic (PEA) technique under dc electric stress. The results indicate that there is a significant amount of homocharge accumulation in the unaged sample due to charge injection. These injected charges are the captured by the deep traps originated from the interface between crystalline and amorphous regions in LDPE. Ageing under ac condition does not necessarily lead to an increase in amount of charge in the bulk but leads to an increase in mobility of charge carriers. Chemical analysis by infrared spectroscope (FTIR) reveals there are chemical changes taken place in the bulk of the material after ac ageing. It is believed that the chemical changes introduce shallow traps which promote the movement of charge carriers in the bulk. Consequently, the injected charges spread across the sample
CoS2xSe2(1-x) nanowire array: An efficient ternary electrocatalyst for the hydrogen evolution reaction
No full textBinary transition metal dichalcogenides (TMDs) have emerged as efficient catalysts for the hydrogen evolution reaction (HER). Co-based TMDs, such as CoS2 and CoSe2, demonstrate promising HER performance due to their intrinsic metallic nature. Recently, the ternary electrocatalysts were widely acknowledged for their prominent efficiency as compared to their binary counterparts due to increased active sites caused by the incorporation of different atoms. Herein, we successfully grew the ternary CoS2xSe2(1-x) (x = 0.67) nanowires (NWs) on a flexible carbon fiber. As a superior electrocatalyst, ternary CoS2xSe2(1-x) NWs arrays demonstrated excellent catalytic activity for electrochemical hydrogen evolution in acidic media, achieving current densities of 10 mA cm-2 and 100 mA cm-2 at overpotentials of 129.5 mV and 174 mV, respectively. Notably, the high stability of CoS2xSe2(1-x) NWs suggested that the ternary CoS2xSe2(1-x) NWs are a scalable catalyst for electrochemical hydrogen evolution
Neriene poculiforma Liu & Chen 2010
No full textNeriene poculiforma Liu & Chen, 2010 Figs 56–58, 69 Neriene poculiforma Liu & Chen, 2010: 65, f. 1A–I, 2A–K (Dmf). Material examined. Yunnan: Xishuangbanna Dai Autonomous Prefecture, Mengla County, Menglun Town, Xishuangbanna Natural Reserve, 21.94°N, 101.25°E, 555m, 1.ix.2009, Zhenyu Wang leg., 1M (holotype), 3MM and 25FF paratypes (CBEE); 50 females, collection site as above, 11. to 16.x.2005, Jian Chen and Fengxiang Liu leg. Diagnosis and Description: See Liu & Chen (2010). Distribution: China (Yunnan) (Fig. 69).Published as part of Li, Jian Yong, Liu, Jie & Chen, Jian, 2018, A review of some Neriene spiders (Araneae, Linyphiidae) from China, pp. 1-90 in Zootaxa 4513 (1) on page 59, DOI: 10.11646/zootaxa.4513.1.1, http://zenodo.org/record/260765
Observation of a(0)(0)(980)-f(0)(980) Mixing
No full textWe report the first observation of a(0)(0)(980)-f(0)(980) mixing in the decays of J/psi -> phi f(0)(980) -> phi a(0)(0)(980) -> phi eta pi(0) and chi(c1) -> a(0)(0)(980)pi(0) -> f(0)(980)pi(0)->pi(+)pi(-)pi(0), using data samples of 1.31 x 10(9) J/psi events and 4.48 x 10(8) psi (3686) events accumulated with the BESIII detector. The signals of f(0)(980) -> a(0)(0)(980) and a(0)(0)(980) -> f(0)(980) mixing are observed at levels of statistical significance of 7.4 sigma and 5.5 sigma, respectively. The corresponding branching fractions and mixing intensities are measured and the constraint regions on the coupling constants, g(a0K+K-) and g(f0K+K-), are estimated. The results improve the understanding of the nature of a(0)(0)(980) and f(0)(980)
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
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