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Qi B.,Shandong University | Zhang N.-B.,Shandong University | Wang S.-Y.,Shandong University | Sun B.-Y.,Lanzhou University | Sun B.-Y.,Key Laboratory of Special Function Materials and Structure Design
Chinese Physics Letters | Year: 2015

Based on the equations of state from the relativistic mean field theory without and with the inclusion of strangeness-bearing hyperons, we study the dimensionless spin parameter j = cj/(GM2) of uniformly rotating neutron stars. It is shown that the maximum value of the spin parameter jmax of a neutron star rotating at the Keplerian frequency fK is jmax ∼ 0.7 when the star mass M > 0.5⊙, which is sustained for various versions of equations of state without and with hyperons. The relationship between j and the scaled rotation frequency f/K is found to be insensitive to the star mass or the adopted equation of state in the models without hyperons. However, the emergence of hyperons in neutron stars will lead to an uncertainty of the spin parameter j, which in turn could generate a complexity in the theoretical study of the quasi-periodic oscillations observed in disk-accreting compact-star systems. © 2015 Chinese Physical Society and IOP Publishing Ltd. Source

Qi B.,Shandong University | Zhang N.-B.,Shandong University | Sun B.-Y.,Lanzhou University | Sun B.-Y.,Key Laboratory of Special Function Materials and Structure Design | And 2 more authors.
Research in Astronomy and Astrophysics | Year: 2016

We study the dimensionless spin parameter j ≡ cJ/(GM2) of different kinds of uniformly rotating compact stars, including traditional neutron stars, hyperonic neutron stars and hybrid stars, based on relativistic mean field theory and the MIT bag model. It is found that jmax ∼ 0.7, which had been suggested in traditional neutron stars, is sustained for hyperonic neutron stars and hybrid stars with M > 0.5 M⊙. Not the interior but rather the crust structure of the stars is a key factor to determine jmax for three kinds of selected compact stars. Furthermore, a universal formula j = 0.63(f/fK) - 0.42(f/fK)2 + 0.48(f/fK)3 is suggested to determine the spin parameter at any rotational frequency f smaller than the Keplerian frequency fK. © 2016 National Astronomical Observatories, Chinese Academy of Sciences and IOP Publishing Ltd. Source

Li J.J.,Lanzhou University | Li J.J.,University Claude Bernard Lyon 1 | Li J.J.,University Paris - Sud | Margueron J.,University Claude Bernard Lyon 1 | And 3 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2016

The formation of new shell gaps in intermediate mass neutron-rich nuclei is investigated within the relativistic Hartree-Fock-Bogoliubov theory, and the role of the Lorentz pseudo-vector and tensor interactions is analyzed. Based on the Foldy-Wouthuysen transformation, we discuss in detail the role played by the different terms of the Lorentz pseudo-vector and tensor interactions in the appearing of the N=16, 32 and 34 shell gaps. The nuclei 24O, 48Si and 52,54Ca are predicted with a large shell gap and zero (24O, 52Ca) or almost zero (48Si, 54Ca) pairing gap, making them candidates for new magic numbers in exotic nuclei. We find from our analysis that the Lorentz pseudo-vector and tensor interactions induce very specific evolutions of single-particle energies, which could clearly sign their presence and reveal the need for relativistic approaches with exchange interactions. © 2015 The Authors. Source

Xiang D.-X.,Lanzhou University | Li H.-R.,Lanzhou University | Li H.-R.,Key Laboratory of Special Function Materials and Structure Design | Xie L.-Z.,Lanzhou University | And 4 more authors.
Faguang Xuebao/Chinese Journal of Luminescence | Year: 2015

Two types of white organic light-emitting devices (WOLED) containing a layered light-emitting region composed of a single blue-emitting host and different fluorescent dopants (blue and orange) were fabricated. The efficiency, lifetime, brightness, spectral voltage-dependence and white balance of devices were investigated. The results show that the performance of the devices strongly depends on the stack order of two emitting layers and the thickness of the emitting layer. It is found that the WOLED with an EML sequence of orange/blue (from anode to cathode) shows better stability than that with an EML sequence of blue/orange. It is due to the rubrene in orange emitting layer that acts as hole-trap sites and captures the passing holes and hence balances the concentration of electrons and holes. The optimized white device exhibits a favorable CIE coordinates (0.3201, 0.3459) which is close to the standard white light. ©, 2015, Chines Academy of Sciences. All right reserved. Source

Liu B.,Lanzhou University | Shi K.,Lanzhou University | Shi K.,Key Laboratory of Special Function Materials and Structure Design | Ye G.,Lanzhou University | And 3 more authors.
Microchemical Journal | Year: 2016

A convenient method was developed for rapid determination of Pu in environmental water samples. The analytical procedure involves preconcentration of Pu using TEVA extraction chromatography implemented in a vacuum box setup, and measurement of 239+240Pu by low background liquid scintillation counter (LSC). Chromatographic behaviors of plutonium, uranium, thorium, and americium were investigated, and the size of chromatographic column, concentration and flow rate of uploaded medium/washing liquid, and composition of eluent of Pu(Cl-)6 2--on TEVA column were explored. The results show that all the above factors affect the adsorption and desorption of Pu(Cl-)6 2--on TEVA column. Decontamination factors of more than 1×104 for uranium and 1×103 for thorium and americium were achieved. Chemical yields of plutonium in the overall procedure range from 70% to 98% and a detection limit of 6×10-3 Bq L-1 in 60min counting time for 5L of water samples were obtained. The method has been successfully applied for rapid and effective determination of low level Pu in water samples. The analytical results show a good agreement with the values obtained using the conventional method. Compared with the conventional analytical procedure, the time consumption and labor intensiveness of the new procedure were greatly reduced and the analysis throughput was greatly increased with low analysis cost. The method is applicable to routine and emergency radiometric assays. © 2015 Elsevier B.V. Source

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