Does public opinion influence US imports?Do countries with a good reputation export more to the US?And vice versa?Based on an extended trade gravity model,this paper employs news data from the GDELT database and US mo...Does public opinion influence US imports?Do countries with a good reputation export more to the US?And vice versa?Based on an extended trade gravity model,this paper employs news data from the GDELT database and US monthly import data to create an indicator of the influence of public opinion to examine the effects of US domestic public opinion on imports.Our research findings suggest that:(i)US public opinion influences US imports.Specifically,(ii)when public opinion turned negative during 2013-2017,it exerted a significantly negative effect on US imports;when public opinion was favorable during 2008-2012,it exerted an insignificantly positive effect on US imports.(iii)According to the pulse response function and variance decomposition,negative public opinion exerted a more significant and more lasting effect on US imports compared with positive public opinion.(iv)It can be discovered after further decomposing such effects on product categories that significant product heterogeneity exists in the public opinion effects on US imports:Complex and differentiated products are more influenced by negative public opinion while homogeneous and intermediate products are more influenced by positive public opinion.展开更多
In this paper we investigate the perturbations from a kind of quartic Hamiltonians under general cubic polynomials. It is proved that the number of isolated zeros of the related abelian integrals around only one cente...In this paper we investigate the perturbations from a kind of quartic Hamiltonians under general cubic polynomials. It is proved that the number of isolated zeros of the related abelian integrals around only one center is not more than 12 except the case of global center. It is also proved that there exists a cubic polynomial such that the disturbed vector field has at least 3 limit cycles while the corresponding vector field without perturbations belongs to the saddle loop case.展开更多
In this paper, we investigate the number and the distribution of the limit cycles bifurcated from a kind of degenerate planar polycycles through three singular points: a saddle-node P 0, a fine saddle P 1 with finite ...In this paper, we investigate the number and the distribution of the limit cycles bifurcated from a kind of degenerate planar polycycles through three singular points: a saddle-node P 0, a fine saddle P 1 with finite order m ∈ N, a contractive (attracting) saddle P 2 with the hyperbolicity ratio q 2(0) ? Q. The connection between P 0 and P 1 is of hh-type and the connection between P 0 and P 2 is of hp-type. It is assumed that the connections between P 0 to P 2 and P 0 to P 1 keep unbroken. We obtain that the cyclicity of this polycycle is not more than 3m + 1, which is linearly dependent on the order of the resonant saddle P 1. We also show that the cyclicity is not more than m + 3 if q 2(0) > m, and that the nearer q 2(0) is close to 1, the more the limit cycles are bifurcated.展开更多
基金the Major Tendering Project of the National Social Science Fund of China(NSSFC)“Study on the Theory and Practiceof Inclusive Green Growth(19ZDA048)”the Advantageous Discipline of CASS Peak Strategy(industrial economics).
文摘Does public opinion influence US imports?Do countries with a good reputation export more to the US?And vice versa?Based on an extended trade gravity model,this paper employs news data from the GDELT database and US monthly import data to create an indicator of the influence of public opinion to examine the effects of US domestic public opinion on imports.Our research findings suggest that:(i)US public opinion influences US imports.Specifically,(ii)when public opinion turned negative during 2013-2017,it exerted a significantly negative effect on US imports;when public opinion was favorable during 2008-2012,it exerted an insignificantly positive effect on US imports.(iii)According to the pulse response function and variance decomposition,negative public opinion exerted a more significant and more lasting effect on US imports compared with positive public opinion.(iv)It can be discovered after further decomposing such effects on product categories that significant product heterogeneity exists in the public opinion effects on US imports:Complex and differentiated products are more influenced by negative public opinion while homogeneous and intermediate products are more influenced by positive public opinion.
基金supported by National Natural Science Foundation of China (Grant No. 10671020)
文摘In this paper we investigate the perturbations from a kind of quartic Hamiltonians under general cubic polynomials. It is proved that the number of isolated zeros of the related abelian integrals around only one center is not more than 12 except the case of global center. It is also proved that there exists a cubic polynomial such that the disturbed vector field has at least 3 limit cycles while the corresponding vector field without perturbations belongs to the saddle loop case.
基金This work was supported by the National Natural Science Foundation of China(Grant No.10671020)
文摘In this paper, we investigate the number and the distribution of the limit cycles bifurcated from a kind of degenerate planar polycycles through three singular points: a saddle-node P 0, a fine saddle P 1 with finite order m ∈ N, a contractive (attracting) saddle P 2 with the hyperbolicity ratio q 2(0) ? Q. The connection between P 0 and P 1 is of hh-type and the connection between P 0 and P 2 is of hp-type. It is assumed that the connections between P 0 to P 2 and P 0 to P 1 keep unbroken. We obtain that the cyclicity of this polycycle is not more than 3m + 1, which is linearly dependent on the order of the resonant saddle P 1. We also show that the cyclicity is not more than m + 3 if q 2(0) > m, and that the nearer q 2(0) is close to 1, the more the limit cycles are bifurcated.
