The pure thermal spectrum in dragging coordinate system and the tunneling radiation characteristics across the event horizon for stationary Demianski-Newman black hole are researched. The result shows that the tunneli...The pure thermal spectrum in dragging coordinate system and the tunneling radiation characteristics across the event horizon for stationary Demianski-Newman black hole are researched. The result shows that the tunneling rate of the particle is relevant to Bekenstein-Hawking entropy, and the derived radiate spectrum is not strictly pure thermal, but is consistent with underlying unitary theory. Finally, we use the obtained results to reduce to stationary Kerr black hole and static Schwarzschild black hole, and lind that only when ignoring the spectrum at higher energies is the tunneling radiation spectrum consistent with Hawking pure thermal one.展开更多
We have investigated the quasinormal modes （QNMs） of phantom scalar perturbation in a Reissner Nordstr6m （RN） background. We find that the dependence of Q, NMs on the mass of the field for the phantom perturbation...We have investigated the quasinormal modes （QNMs） of phantom scalar perturbation in a Reissner Nordstr6m （RN） background. We find that the dependence of Q, NMs on the mass of the field for the phantom perturbation is totally different from that of usual massive perturbation. However, we obtain the same critical value of the overtone number for an angular quantum number from which the mass will begin to have a reverse effect on the real part of QNM frequencies and the perturbation-independent relation between the Q, NMs and the second order thermodynamic phase transition.展开更多
[Objective] Camellia oleifera Abel is a typical woody oil plant in China and it has many functional components. Since it was first found in 1980, Basilepta melanopus Lefevre has become the pest with outbreak area, whi...[Objective] Camellia oleifera Abel is a typical woody oil plant in China and it has many functional components. Since it was first found in 1980, Basilepta melanopus Lefevre has become the pest with outbreak area, which makes the yield and quality of camellia seed oil suffer great losses. The aim was to provide refer- ences for the field damages and prediction of Basilepta melanopus Lefevre based on severity of damage and the actual need for prediction of B. melanopus. [Meth- ods] The investigation was carried out to study the average number of wormholes in damaged leaves, average number of fruit per branch and leaf damage rate caused by B. melanopus using point-survey systematically at Yong＇an Town of Changsha, Hunan Province from early May to middle June in 2014. Six functions were used to find the optimal model through fitting to calculate the threshold of mean wormhole number. [Results] The cubic equations had the best effects in fitting the 3 pairs of variables of average wormhole number and camellia fruit, camellia fruit and leaf damage rate, and wormhole number and leaf damage rate, and the variance analy- sis reached the extreme significant difference （P〈0.05）. [Conclusion] Based on these mathematical models, the threshold of wormhole number is 5.01 per leaf.展开更多
The effects of different yaw angles on the aerodynamic performance of city electric multiple units(EMUs)were investigated in a wind tunnel using a 1:16.8 scaled model.Pressure scanning valve and six-component box-type...The effects of different yaw angles on the aerodynamic performance of city electric multiple units(EMUs)were investigated in a wind tunnel using a 1:16.8 scaled model.Pressure scanning valve and six-component box-type aerodynamic balance were used to test the pressure distribution and aerodynamic force of the head car respectively from the 1.5-and 3-coach grouping city EMU models.Meanwhile,the effects of the yaw angles on the pressure distribution of the streamlined head as well as the aerodynamic forces of the train were analyzed.The experimental results showed that the pressure coefficient was the smallest at the maximum slope of the main shape-line.The side force coefficient and pressure coefficient along the head car cross-section were most affected by crosswind when the yaw angle was 55°,and replacing a 3-coach grouping with a 1.5-coach grouping had obvious advantages for wind tunnel testing when the yaw angle was within 24.2°.In addition,the relative errors of lift coefficient C_(L),roll moment coefficient C_(Mx),side force coefficient C_(S),and drag coefficient C_(D) between the 1.5-and 3-coach cases were below 5.95%,which all met the requirements of the experimental accuracy.展开更多
The massless scalar quasiaormal modes （QNMs） of a stationary axisymmetric Einstein-Maxwell dilato-axioa （EMDA） black hole are calculated numerically using the continued fraction method first proposed by Leaver. Th...The massless scalar quasiaormal modes （QNMs） of a stationary axisymmetric Einstein-Maxwell dilato-axioa （EMDA） black hole are calculated numerically using the continued fraction method first proposed by Leaver. The fundamental quasinormal frequencies （slowly damped QNMs） are obtained and the peculiar behaviours of them are studied. It is shown that these frequencies depend on the dilaton parameter D, the rotational parameter a, the multiple moment l and the azimuthal number m, and have the same values with other authors at the Schwarzschild and Kerr limit.展开更多
We investigate the electromagnetic perturbation around a black hole with quintessence-like matter and a deficit solid angle.The complex frequencies of the quasinormal modes of electromagnetic perturbation are evaluate...We investigate the electromagnetic perturbation around a black hole with quintessence-like matter and a deficit solid angle.The complex frequencies of the quasinormal modes of electromagnetic perturbation are evaluated by the third-order WKB approximation.The results show that the electromagnetic perturbation around the black hole damps more slowly owing to the presence of the quintessence-like.The phenomenon can be distinguished from the black hole only with a deficit angle.展开更多
We present some novel rotating hairy black hole metric in （2 ＋ 1） dimensions, which is an exact solution to the field equations of the Einstein-scalar-AdS theory with a non-minimal coupling. The scalar potential is...We present some novel rotating hairy black hole metric in （2 ＋ 1） dimensions, which is an exact solution to the field equations of the Einstein-scalar-AdS theory with a non-minimal coupling. The scalar potential is determined by the metric ansatz and consistency of the field equations and cannot be prescribed arbitrarily. In the simplified, critical ease, the scalar potential contains two independent constant parameters, which are respectively related to the mass and angular momentum of the black hole in a particular way. As long as the angular momentum does not vanish, the metric can have zero, one or two horizons. The case with no horizon is physically uninteresting because of the curvature singularity lying at the origin. We identify the necessary conditions for at least one horizon to be present in the solution, which imposes some bound on the mass-angular momentum ratio. For some particular choice of pararneters our solution degenerates into some previously known black hole solutions.展开更多
基金The project supported by National Natural Science Foundation of China under Grant No. 10347008 and the Science Foundation for Fundamental Research of Sichuan Province of China under Grant No. 05JY029-092 Great thanks are due to Prof. Zhang Jing-Yi and Dr. Ren Jun for their helpful discussion.
文摘The pure thermal spectrum in dragging coordinate system and the tunneling radiation characteristics across the event horizon for stationary Demianski-Newman black hole are researched. The result shows that the tunneling rate of the particle is relevant to Bekenstein-Hawking entropy, and the derived radiate spectrum is not strictly pure thermal, but is consistent with underlying unitary theory. Finally, we use the obtained results to reduce to stationary Kerr black hole and static Schwarzschild black hole, and lind that only when ignoring the spectrum at higher energies is the tunneling radiation spectrum consistent with Hawking pure thermal one.
基金Supported by the National Natural Science Foundation of China under Grant No.10905020the China Postdoctoral Science Foundation under Grant Nos.201003245 and 20090460592
文摘We have investigated the quasinormal modes （QNMs） of phantom scalar perturbation in a Reissner Nordstr6m （RN） background. We find that the dependence of Q, NMs on the mass of the field for the phantom perturbation is totally different from that of usual massive perturbation. However, we obtain the same critical value of the overtone number for an angular quantum number from which the mass will begin to have a reverse effect on the real part of QNM frequencies and the perturbation-independent relation between the Q, NMs and the second order thermodynamic phase transition.
文摘[Objective] Camellia oleifera Abel is a typical woody oil plant in China and it has many functional components. Since it was first found in 1980, Basilepta melanopus Lefevre has become the pest with outbreak area, which makes the yield and quality of camellia seed oil suffer great losses. The aim was to provide refer- ences for the field damages and prediction of Basilepta melanopus Lefevre based on severity of damage and the actual need for prediction of B. melanopus. [Meth- ods] The investigation was carried out to study the average number of wormholes in damaged leaves, average number of fruit per branch and leaf damage rate caused by B. melanopus using point-survey systematically at Yong＇an Town of Changsha, Hunan Province from early May to middle June in 2014. Six functions were used to find the optimal model through fitting to calculate the threshold of mean wormhole number. [Results] The cubic equations had the best effects in fitting the 3 pairs of variables of average wormhole number and camellia fruit, camellia fruit and leaf damage rate, and wormhole number and leaf damage rate, and the variance analy- sis reached the extreme significant difference （P〈0.05）. [Conclusion] Based on these mathematical models, the threshold of wormhole number is 5.01 per leaf.
基金Project(2020YFA0710903) supported by the National Key R&D Program of ChinaProjects(2020zzts111, 2020zzts117)supported by the Graduate Student Independent Innovation Project of Central South University,ChinaProject(202037)supported by Transport Department of Hunan Province Technology Innovation Project,China。
文摘The effects of different yaw angles on the aerodynamic performance of city electric multiple units(EMUs)were investigated in a wind tunnel using a 1:16.8 scaled model.Pressure scanning valve and six-component box-type aerodynamic balance were used to test the pressure distribution and aerodynamic force of the head car respectively from the 1.5-and 3-coach grouping city EMU models.Meanwhile,the effects of the yaw angles on the pressure distribution of the streamlined head as well as the aerodynamic forces of the train were analyzed.The experimental results showed that the pressure coefficient was the smallest at the maximum slope of the main shape-line.The side force coefficient and pressure coefficient along the head car cross-section were most affected by crosswind when the yaw angle was 55°,and replacing a 3-coach grouping with a 1.5-coach grouping had obvious advantages for wind tunnel testing when the yaw angle was within 24.2°.In addition,the relative errors of lift coefficient C_(L),roll moment coefficient C_(Mx),side force coefficient C_(S),and drag coefficient C_(D) between the 1.5-and 3-coach cases were below 5.95%,which all met the requirements of the experimental accuracy.
基金Project supported by the National Natural Science Foundation of China （Grant No 10473004）, the FADEDD （Grant No 200317）, and the SRFDP （Grant No 20040542003）.
文摘The massless scalar quasiaormal modes （QNMs） of a stationary axisymmetric Einstein-Maxwell dilato-axioa （EMDA） black hole are calculated numerically using the continued fraction method first proposed by Leaver. The fundamental quasinormal frequencies （slowly damped QNMs） are obtained and the peculiar behaviours of them are studied. It is shown that these frequencies depend on the dilaton parameter D, the rotational parameter a, the multiple moment l and the azimuthal number m, and have the same values with other authors at the Schwarzschild and Kerr limit.
基金Supported by the National Natural Science Foundation of China under Grant No. 11147104
文摘We investigate the electromagnetic perturbation around a black hole with quintessence-like matter and a deficit solid angle.The complex frequencies of the quasinormal modes of electromagnetic perturbation are evaluated by the third-order WKB approximation.The results show that the electromagnetic perturbation around the black hole damps more slowly owing to the presence of the quintessence-like.The phenomenon can be distinguished from the black hole only with a deficit angle.
文摘We present some novel rotating hairy black hole metric in （2 ＋ 1） dimensions, which is an exact solution to the field equations of the Einstein-scalar-AdS theory with a non-minimal coupling. The scalar potential is determined by the metric ansatz and consistency of the field equations and cannot be prescribed arbitrarily. In the simplified, critical ease, the scalar potential contains two independent constant parameters, which are respectively related to the mass and angular momentum of the black hole in a particular way. As long as the angular momentum does not vanish, the metric can have zero, one or two horizons. The case with no horizon is physically uninteresting because of the curvature singularity lying at the origin. We identify the necessary conditions for at least one horizon to be present in the solution, which imposes some bound on the mass-angular momentum ratio. For some particular choice of pararneters our solution degenerates into some previously known black hole solutions.
