We propose and study a discrete host-parasitoid model of difference equations with a spatial host refuge where hosts in the refuge patch are free from parasitism but undergo a demographic strong Allee effect.If the gr...We propose and study a discrete host-parasitoid model of difference equations with a spatial host refuge where hosts in the refuge patch are free from parasitism but undergo a demographic strong Allee effect.If the growth rate of hosts in the non-refuge patch is less than one,a host Allee threshold is derived below which both populations become extinct.It is proven that both populations can persist indefinitely if the host growth rate in the non-refuge patch exceeds one and the maximum reproductive number of parasitoids is greater than one.Numerical simulations reveal that the host refuge can either stabilize or destabilize the host-parasitoid interactions,depending on other model parameters.A large number of parasitoid turnover from a parasitized host may be detrimental to the parasitoids due to Allee effects in the hosts within the refuge patch.Moreover,it is demonstrated numerically that if the host growth rate is not small,the population level of parasitoids may suddenly drop to a small value as some parameters are varied.展开更多
The behavior of shear modulus in solid-liquid mixing phase has been discussed and analyzed. The result was concluded that shear modulus went to zero as the melting mass ratio attained a critical value. The percolation...The behavior of shear modulus in solid-liquid mixing phase has been discussed and analyzed. The result was concluded that shear modulus went to zero as the melting mass ratio attained a critical value. The percolation theory model we pro-posed showed that this value was about 0.68742. The melting-induced destabilizing factor of material proposed by us can represent phenomenologically the change of shear modulus in melting process.展开更多
In this paper, after taking th e effect of axis force on bending into consideration, the general potential ener gy for the circular double articulated arch is established undergoing vertical d istributive load g 0/...In this paper, after taking th e effect of axis force on bending into consideration, the general potential ener gy for the circular double articulated arch is established undergoing vertical d istributive load g 0/ cos 2θ . With sufficient engineering precision, the fourth approximations to the destabilizing critical load of the arch under t his load are obtained by Ritz method. The approximations to the critical load ta ble are listed for various center angles of arch, and are contrasted with the cr itical load circular arch undergoing radial uniform load. Some reference results have been obtained.展开更多
文摘We propose and study a discrete host-parasitoid model of difference equations with a spatial host refuge where hosts in the refuge patch are free from parasitism but undergo a demographic strong Allee effect.If the growth rate of hosts in the non-refuge patch is less than one,a host Allee threshold is derived below which both populations become extinct.It is proven that both populations can persist indefinitely if the host growth rate in the non-refuge patch exceeds one and the maximum reproductive number of parasitoids is greater than one.Numerical simulations reveal that the host refuge can either stabilize or destabilize the host-parasitoid interactions,depending on other model parameters.A large number of parasitoid turnover from a parasitized host may be detrimental to the parasitoids due to Allee effects in the hosts within the refuge patch.Moreover,it is demonstrated numerically that if the host growth rate is not small,the population level of parasitoids may suddenly drop to a small value as some parameters are varied.
文摘The behavior of shear modulus in solid-liquid mixing phase has been discussed and analyzed. The result was concluded that shear modulus went to zero as the melting mass ratio attained a critical value. The percolation theory model we pro-posed showed that this value was about 0.68742. The melting-induced destabilizing factor of material proposed by us can represent phenomenologically the change of shear modulus in melting process.
文摘In this paper, after taking th e effect of axis force on bending into consideration, the general potential ener gy for the circular double articulated arch is established undergoing vertical d istributive load g 0/ cos 2θ . With sufficient engineering precision, the fourth approximations to the destabilizing critical load of the arch under t his load are obtained by Ritz method. The approximations to the critical load ta ble are listed for various center angles of arch, and are contrasted with the cr itical load circular arch undergoing radial uniform load. Some reference results have been obtained.
