To figure out the load distribution of thin-section rolling bearing supported by flexible structure with squirrel cage and the distribution's influence on bearing life,an iterative FEA method is proposed to use th...To figure out the load distribution of thin-section rolling bearing supported by flexible structure with squirrel cage and the distribution's influence on bearing life,an iterative FEA method is proposed to use the result calculated from the Quasi-Dynamic model based on the rigid support hypothesis. The contact angle,contact position and stiffness of equivalent spring are modified during the iterative FEA to optimize the FEA model,and then the bearings' life can be predicted when the error is below 0.5%. It can be concluded that from the analysis results the load distribution under flexible support is more uniform than that of the rigid support,while the maximum load decreases by 11.2% and bearing life increases by 14.7%. The analysis result of different values of thickness of bearing house,rings and hollow shaft demonstrates the thicknesses of bearing house and hollow shaft have a greater influence on the load's uniformity and bearing's life than those of the rings.展开更多
The objective of this study is to investigate the spatiotemporal dynamics of a Rhizophagusgrandis-Dendroctonusvalenspredator-prey system.Under Neu-mann boundary conditions,we establish a reaction-diffusion system inco...The objective of this study is to investigate the spatiotemporal dynamics of a Rhizophagusgrandis-Dendroctonusvalenspredator-prey system.Under Neu-mann boundary conditions,we establish a reaction-diffusion system incorpo-rating Holling-II functional response,nonlocal effect,predator-prey taxis and time delay to elucidate the regulatory mechanisms of chemotactic behaviors and delayed predation pressure on ecosystem stability.In addition,we inves-tigate the existence conditions for Hopf bifurcation and employ the multiple time scales method to derive its normal form.Under appropriate parameter constraints,numerical simulations demonstrate that the system exclusively exhibits Hopf bifurcation in the current parameter configuration,where non-local interactions,taxis and time delays synergistically induce the formation of spatially heterogeneous periodic solutions.These results elucidate the in-trinsic mechanism underlying periodic pest outbreaks and provide a theoret-ical foundation for optimizing biological control strategies.Notably,our anal-ysis reveals the critical role of predator taxis capability and delayed predation feedback in stabilizing pest population cycles,offering practical guidance for sustainable forest pest management.展开更多
Pine wilt disease is a destructive forest disease with strong infectivity,a wide spread range and high difficulty in prevention and control.Since controlling Monochamus alternatus,the vector of pine wood nematode(Burs...Pine wilt disease is a destructive forest disease with strong infectivity,a wide spread range and high difficulty in prevention and control.Since controlling Monochamus alternatus,the vector of pine wood nematode(Bursaphelenchus rylophilus)can reduce the occurrence of pine wilt disease efficiently,the parasitic natural enemy of M.alternatus,Dastarcus helophoroides,is introduced in this paper.Considering the infuence of parasitic time of D.helophoroides on the control effect,based on the mutualistic symbiosis and parasitic relationship among pine wood nematode,M.alternatus and D.heloporoides,this paper establishes a pine wood nematode prevention and control model with delay.Then,the stability of positive equilibrium and the existence of Hopf bifurcation are discussed.Besides,we obtain the normal form of Hopf bifurcation by applying the multiple time scales method.Finally,numerical simulations with two sets of meaningful parameters selected by means of statistical analysis are carried out to support the theoretical findings.Through the comparative analysis of numerical simulations,the factors affecting the control effect of pine wilt disease are obtained,and some suggestions are put forward for practical control in the forest.展开更多
This study aimed to better understand the changes of fatty acids in dry-cured fish during storage,and to analyze the reactive carbonyl species(RCS)formation mechanism primarily from the standpoint of oxygen-derived fr...This study aimed to better understand the changes of fatty acids in dry-cured fish during storage,and to analyze the reactive carbonyl species(RCS)formation mechanism primarily from the standpoint of oxygen-derived free radical reactions interactions.Oleic acid and linoleic acid were the predominant unsaturated fatty acids in dry-cured fish.The content of unsaturated fatty acids in dry-cured fish increased over time at 4℃,while decreased at 25℃.Singlet oxygen,superoxide anion and hydroxyl-alkyl radical levels increased with time,and more free radicals were yielded in the samples held at 25℃.Redundancy analysis revealed that hydroxyl-alkyl radicals had the greatest influence on the oxidation of lipids.Hydroxyl-alkyl radicals and singlet oxygen levels were positively correlated with 4-hydroxy-2-nonenal(HNE),malondialdehyde(MDA),peroxide value and acid value levels,but adversely to 4-hydroxy-2-hexenal(HHE)and fatty acids levels.Moreover,HNE and MDA were both inversely linked with fatty acids contents.It is possible that the intermediates of lipid oxidation undergo oxidation,cleavage and other reactions due to free radical activity,resulting in the generation of aldehyde precursors.These findings help us further characterize the lipid oxidation and RCS formation mechanism in dry-cured fish during storage.展开更多
基金Sponsored by the Major State Basic Research Development Program of China(Grant No.2013CB632305)the National Natural Science Foundation of China(Grant No.51375108)
文摘To figure out the load distribution of thin-section rolling bearing supported by flexible structure with squirrel cage and the distribution's influence on bearing life,an iterative FEA method is proposed to use the result calculated from the Quasi-Dynamic model based on the rigid support hypothesis. The contact angle,contact position and stiffness of equivalent spring are modified during the iterative FEA to optimize the FEA model,and then the bearings' life can be predicted when the error is below 0.5%. It can be concluded that from the analysis results the load distribution under flexible support is more uniform than that of the rigid support,while the maximum load decreases by 11.2% and bearing life increases by 14.7%. The analysis result of different values of thickness of bearing house,rings and hollow shaft demonstrates the thicknesses of bearing house and hollow shaft have a greater influence on the load's uniformity and bearing's life than those of the rings.
基金funded by the Heilongjiang Provincial Natural Science Foundation of China(Grant No.LH2024A001)the College Students Innovations Special Project funded by Northeast Forestry University(No.DCLXY-2025010).
文摘The objective of this study is to investigate the spatiotemporal dynamics of a Rhizophagusgrandis-Dendroctonusvalenspredator-prey system.Under Neu-mann boundary conditions,we establish a reaction-diffusion system incorpo-rating Holling-II functional response,nonlocal effect,predator-prey taxis and time delay to elucidate the regulatory mechanisms of chemotactic behaviors and delayed predation pressure on ecosystem stability.In addition,we inves-tigate the existence conditions for Hopf bifurcation and employ the multiple time scales method to derive its normal form.Under appropriate parameter constraints,numerical simulations demonstrate that the system exclusively exhibits Hopf bifurcation in the current parameter configuration,where non-local interactions,taxis and time delays synergistically induce the formation of spatially heterogeneous periodic solutions.These results elucidate the in-trinsic mechanism underlying periodic pest outbreaks and provide a theoret-ical foundation for optimizing biological control strategies.Notably,our anal-ysis reveals the critical role of predator taxis capability and delayed predation feedback in stabilizing pest population cycles,offering practical guidance for sustainable forest pest management.
基金funded by Fundamental Research Funds for the Central Universities of China(No.2572022DJ06).
文摘Pine wilt disease is a destructive forest disease with strong infectivity,a wide spread range and high difficulty in prevention and control.Since controlling Monochamus alternatus,the vector of pine wood nematode(Bursaphelenchus rylophilus)can reduce the occurrence of pine wilt disease efficiently,the parasitic natural enemy of M.alternatus,Dastarcus helophoroides,is introduced in this paper.Considering the infuence of parasitic time of D.helophoroides on the control effect,based on the mutualistic symbiosis and parasitic relationship among pine wood nematode,M.alternatus and D.heloporoides,this paper establishes a pine wood nematode prevention and control model with delay.Then,the stability of positive equilibrium and the existence of Hopf bifurcation are discussed.Besides,we obtain the normal form of Hopf bifurcation by applying the multiple time scales method.Finally,numerical simulations with two sets of meaningful parameters selected by means of statistical analysis are carried out to support the theoretical findings.Through the comparative analysis of numerical simulations,the factors affecting the control effect of pine wilt disease are obtained,and some suggestions are put forward for practical control in the forest.
基金supported financially by the National Natural Science Foundation of China(31871869)the National Key R&D Program of China(2018YFD0901006).
文摘This study aimed to better understand the changes of fatty acids in dry-cured fish during storage,and to analyze the reactive carbonyl species(RCS)formation mechanism primarily from the standpoint of oxygen-derived free radical reactions interactions.Oleic acid and linoleic acid were the predominant unsaturated fatty acids in dry-cured fish.The content of unsaturated fatty acids in dry-cured fish increased over time at 4℃,while decreased at 25℃.Singlet oxygen,superoxide anion and hydroxyl-alkyl radical levels increased with time,and more free radicals were yielded in the samples held at 25℃.Redundancy analysis revealed that hydroxyl-alkyl radicals had the greatest influence on the oxidation of lipids.Hydroxyl-alkyl radicals and singlet oxygen levels were positively correlated with 4-hydroxy-2-nonenal(HNE),malondialdehyde(MDA),peroxide value and acid value levels,but adversely to 4-hydroxy-2-hexenal(HHE)and fatty acids levels.Moreover,HNE and MDA were both inversely linked with fatty acids contents.It is possible that the intermediates of lipid oxidation undergo oxidation,cleavage and other reactions due to free radical activity,resulting in the generation of aldehyde precursors.These findings help us further characterize the lipid oxidation and RCS formation mechanism in dry-cured fish during storage.
