Fatigue life and reliability of aero-engine blade are always of important significance to flight safety.The establishment of damage model is one of the key factors in blade fatigue research.Conventional linear Miner＇...Fatigue life and reliability of aero-engine blade are always of important significance to flight safety.The establishment of damage model is one of the key factors in blade fatigue research.Conventional linear Miner＇s sum method is not suitable for aero-engine because of its low accuracy.A back propagation neutral network（BPNN） based on the combination of Levenberg-Marquardt（LM） and finite element method（FEM） is used to describe process of nonlinear damage accumulation behavior in material and predict fatigue life of the blade.Fatigue tests of standard specimen made from TC4 are carried out to obtain material fatigue parameters and S-N curve.A nonlinear continuum damage model（CDM）,based on the BPNN with one hidden layer and ten neurons,is built to investigate the nonlinear damage accumulation behavior,in which the results from the tests are used as training set.Comparing with linear models and previous nonlinear models,BPNN has the lowest calculation error in full load range.It has significant accuracy when the load is below 500 MPa.Especially,when the load is 350 MPa,the calculation error of the BPNN is only 0.4%.The accurate model of the blade is built by using 3D coordinate measurement technology.The loading cycle in fatigue analysis is defined from takeoff to cruise in 10 min,and the load history is obtained from finite element analysis（FEA）.Then the fatigue life of the compressor blade is predicted by using the BPNN model.The final fatigue life of the aero-engine blade is 6.55 104 cycles（10 916 h） based on the BPNN model,which is effective for the virtual design of aero-engine blade.展开更多
A pH predictive model based on acid–base equilibria and ion equilibria was proposed to calculate the pH value of the overhead condensing system of crude distillation unit. The pH model could be used to predict the ap...A pH predictive model based on acid–base equilibria and ion equilibria was proposed to calculate the pH value of the overhead condensing system of crude distillation unit. The pH model could be used to predict the appropriate amounts of neutralizers by measuring the Cl-ion concentration of the overhead knockout drum. The pH values of various neutralized streams were estimated by this model. The results showed that the predicted pH values were in good agreement with the experimental ones. The trend of the corrosion inhibition efficiency decreases in the following order: ethylenediamine > N,Ndimethylethanolamine> triethylamine > 3-methoxypropylamine > morpholine. The difficulty in the accurate control of corrosion was solved, and a good instruction was provided for mitigating corrosion in refinery.展开更多
A new bipartition neutral transport model was developed for quick identification of the recycling properties of the wall-released hydrogenic neutral particles in the vicinity of the divertor target plate. Based on thi...A new bipartition neutral transport model was developed for quick identification of the recycling properties of the wall-released hydrogenic neutral particles in the vicinity of the divertor target plate. Based on this model, the numerical calculation results are fairly consistent with the results obtained with the ＇multi-generation method＇. This model can not only be utilized to provide a source term from neutral transport calculations for the B2 edge plasma transport code, which has been used to simulate edge plasma transport of an HL-2A divertor configuration, but can also be specifically applied for fast classification of the divertor plasma as high recycling or low recycling. Our results also show that the transmissivity is lower in the high-recycling regime.展开更多
Based on the multipoint magnetic observations of Cluster from 2001 to 2004,the magnetic field structure in magnetotail Neutral Sheet(NS) is statistically surveyed.The results are as follows.In NS,a cubic function is s...Based on the multipoint magnetic observations of Cluster from 2001 to 2004,the magnetic field structure in magnetotail Neutral Sheet(NS) is statistically surveyed.The results are as follows.In NS,a cubic function is selected to reveal the relation between y(GSM) and positional parameter z.The relation between y and magnetic field values indicates that the magnetic field is weak at midnight region and strengthens gradually at the duskside and dawnside.The relation between y and curvature radius is expressed by a quadratic function.And R_c of flattened CS is less than that of the normal CS.B_y determines the orientation of MFLs' configuration.The polar angle of the curvature vector is affected by the NS configuration.In addition,the correlation between the polar angle of the curvature vector and z is higher.The polar angle of the normal of the osculating plane is uncertain in the center area.The relation between the azimuthal angles of the curvature vector(the normal of the osculating plane) and y is negatively correlated.An empirical model applied to yz plane of the three-dimensional structure of the magnetic field lines in the NS are developed,and it is represented as a function of the positional parameter y.Finally,the current density is also statistically surveyed.展开更多
The constraints on the number of neutrinos generations, g'1 coupling and Z?- Z′ mixing angle through the invisible width method, and in the framework of a U(1)B-L model are obtained. Based on the experimental val...The constraints on the number of neutrinos generations, g'1 coupling and Z?- Z′ mixing angle through the invisible width method, and in the framework of a U(1)B-L model are obtained. Based on the experimental value reported by the LEP for the rate , we obtained a bound on the g'1 coupling, . In addition, we derive 90% C.L. bounds on the Z?- Z′ mixing angle , improving the existing bounds by one order of magnitude.展开更多
In 2014,a 40-ha undisturbed plot was established in the Beijing Songshan Nature Reserve.The spatial distribution and spatial associations of five dominant tree species of different height classes were examined using s...In 2014,a 40-ha undisturbed plot was established in the Beijing Songshan Nature Reserve.The spatial distribution and spatial associations of five dominant tree species of different height classes were examined using spatial point pattern analysis and the effects of these species on local community diversity assemblages were examined using the ISAR method.The dominant species were characterized by an aggregated distribution at spatial scales of 0–50 m.At smaller spatial scales,trees in larger height classes had significant positive and negative effects on the diversity of the lower height classes.However,at larger spatial scales this effect was diminished.At small scales(0–10 m),accumulator species had positive effects on species diversity,maintained an over-representative proportion of diversity in their proximity,and supported the ecological niche theory.At the larger scale(10–50 m),neutral species were dominant and had positive effects on species diversity,though repeller species,which had negative effects on species diversity,also contributed to diversity.Neutral and accumulator species together determined local species diversity,but the relative importance of the two was closely related to spatial scale.A combination of the ecological niche theory and neutral processes together determines species coexistence and biodiversity of an undisturbed pine forest.展开更多
基金supported by National Natural Science Foundation of China (Grant No. 60879002)Tianjin Municipal Science and Technology Support Plan of China (Grant No. 10ZCKFGX03800)
文摘Fatigue life and reliability of aero-engine blade are always of important significance to flight safety.The establishment of damage model is one of the key factors in blade fatigue research.Conventional linear Miner＇s sum method is not suitable for aero-engine because of its low accuracy.A back propagation neutral network（BPNN） based on the combination of Levenberg-Marquardt（LM） and finite element method（FEM） is used to describe process of nonlinear damage accumulation behavior in material and predict fatigue life of the blade.Fatigue tests of standard specimen made from TC4 are carried out to obtain material fatigue parameters and S-N curve.A nonlinear continuum damage model（CDM）,based on the BPNN with one hidden layer and ten neurons,is built to investigate the nonlinear damage accumulation behavior,in which the results from the tests are used as training set.Comparing with linear models and previous nonlinear models,BPNN has the lowest calculation error in full load range.It has significant accuracy when the load is below 500 MPa.Especially,when the load is 350 MPa,the calculation error of the BPNN is only 0.4%.The accurate model of the blade is built by using 3D coordinate measurement technology.The loading cycle in fatigue analysis is defined from takeoff to cruise in 10 min,and the load history is obtained from finite element analysis（FEA）.Then the fatigue life of the compressor blade is predicted by using the BPNN model.The final fatigue life of the aero-engine blade is 6.55 104 cycles（10 916 h） based on the BPNN model,which is effective for the virtual design of aero-engine blade.
基金supported by the PetroChina Company Limited (20151191)
文摘A pH predictive model based on acid–base equilibria and ion equilibria was proposed to calculate the pH value of the overhead condensing system of crude distillation unit. The pH model could be used to predict the appropriate amounts of neutralizers by measuring the Cl-ion concentration of the overhead knockout drum. The pH values of various neutralized streams were estimated by this model. The results showed that the predicted pH values were in good agreement with the experimental ones. The trend of the corrosion inhibition efficiency decreases in the following order: ethylenediamine > N,Ndimethylethanolamine> triethylamine > 3-methoxypropylamine > morpholine. The difficulty in the accurate control of corrosion was solved, and a good instruction was provided for mitigating corrosion in refinery.
文摘A new bipartition neutral transport model was developed for quick identification of the recycling properties of the wall-released hydrogenic neutral particles in the vicinity of the divertor target plate. Based on this model, the numerical calculation results are fairly consistent with the results obtained with the ＇multi-generation method＇. This model can not only be utilized to provide a source term from neutral transport calculations for the B2 edge plasma transport code, which has been used to simulate edge plasma transport of an HL-2A divertor configuration, but can also be specifically applied for fast classification of the divertor plasma as high recycling or low recycling. Our results also show that the transmissivity is lower in the high-recycling regime.
基金Supported by the National Natural Science Foundation of China(41231066)Ministry of Science and Technology of China(2011CB811404)+1 种基金the Specialized Research Fund for State Key Laboratories of the CASthe Scientific Research Staring Foundation for Nanjing University of Information Science and Technology(2013x030)
文摘Based on the multipoint magnetic observations of Cluster from 2001 to 2004,the magnetic field structure in magnetotail Neutral Sheet(NS) is statistically surveyed.The results are as follows.In NS,a cubic function is selected to reveal the relation between y(GSM) and positional parameter z.The relation between y and magnetic field values indicates that the magnetic field is weak at midnight region and strengthens gradually at the duskside and dawnside.The relation between y and curvature radius is expressed by a quadratic function.And R_c of flattened CS is less than that of the normal CS.B_y determines the orientation of MFLs' configuration.The polar angle of the curvature vector is affected by the NS configuration.In addition,the correlation between the polar angle of the curvature vector and z is higher.The polar angle of the normal of the osculating plane is uncertain in the center area.The relation between the azimuthal angles of the curvature vector(the normal of the osculating plane) and y is negatively correlated.An empirical model applied to yz plane of the three-dimensional structure of the magnetic field lines in the NS are developed,and it is represented as a function of the positional parameter y.Finally,the current density is also statistically surveyed.
文摘The constraints on the number of neutrinos generations, g'1 coupling and Z?- Z′ mixing angle through the invisible width method, and in the framework of a U(1)B-L model are obtained. Based on the experimental value reported by the LEP for the rate , we obtained a bound on the g'1 coupling, . In addition, we derive 90% C.L. bounds on the Z?- Z′ mixing angle , improving the existing bounds by one order of magnitude.
基金supported by the Beijing Common Construction Project Research and demonstrations on the regression technique for minimum populations of wild plants(2016YFC0503106)
文摘In 2014,a 40-ha undisturbed plot was established in the Beijing Songshan Nature Reserve.The spatial distribution and spatial associations of five dominant tree species of different height classes were examined using spatial point pattern analysis and the effects of these species on local community diversity assemblages were examined using the ISAR method.The dominant species were characterized by an aggregated distribution at spatial scales of 0–50 m.At smaller spatial scales,trees in larger height classes had significant positive and negative effects on the diversity of the lower height classes.However,at larger spatial scales this effect was diminished.At small scales(0–10 m),accumulator species had positive effects on species diversity,maintained an over-representative proportion of diversity in their proximity,and supported the ecological niche theory.At the larger scale(10–50 m),neutral species were dominant and had positive effects on species diversity,though repeller species,which had negative effects on species diversity,also contributed to diversity.Neutral and accumulator species together determined local species diversity,but the relative importance of the two was closely related to spatial scale.A combination of the ecological niche theory and neutral processes together determines species coexistence and biodiversity of an undisturbed pine forest.
