In the aerospace field,hole burnishing enhancement plays an essential role in improving the service performance of load-bearing holes.To satisfy the assembly accuracy and strength requirements,the structure shape and ...In the aerospace field,hole burnishing enhancement plays an essential role in improving the service performance of load-bearing holes.To satisfy the assembly accuracy and strength requirements,the structure shape and surface integrity must be considered simultaneously during the enhancement process.The current manufacturing process of hole burnishing has a relatively weak balance between the structure shape and surface integrity;therefore,it is necessary to analyze the mechanism and optimize the parameters to improve the strengthening effect of the holes.In this study,a two-dimensional longitudinal simplified model for the hole burnishing process was established,and the reasons for the surface roughness improvement of the hole wall and material accumulation on the upper surface were analyzed.Experiments were conducted to determine the influence of the burnishing parameters on the structure shape(material accumulation,shape contour,and roundness)and surface integrity(surface roughness,residual stress,and surface hardness),based on the opposite requirements of improving the structure shape and surface integrity for the burnishing depth(BD).The results showed that with an increase in the BD,the structure shape deteriorated,whereas the surface integrity improved.Fatigue behavior verification experiments were conducted,and parameter selection schemes for the collaborative improvement of the structure shape and surface integrity were discussed.For the holes of titanium alloy TB6(Ti-10V-2Fe-3Al),the fatigue life can be increased by 162%when the BD,spindle speed,and feed rate were 0.20 mm,200 r/min,and 0.2 mm/r,respectively.展开更多
Although CO_(2)photoreduction is a promising method for solar‐to‐fuel conversion,it suffers from low charge transfer efficiency of the photocatalysts.To improve the CO_(2)photoreduction performance,introduction of e...Although CO_(2)photoreduction is a promising method for solar‐to‐fuel conversion,it suffers from low charge transfer efficiency of the photocatalysts.To improve the CO_(2)photoreduction performance,introduction of electron‐accumulated materials on the photocatalyst surface is considered an effective method.In this study,the Bi_(19)S_(27)Br_(3)/BiOBr composites were designed and synthesized.The Bi19S27Br3 nanorod in this photocatalytic system acts as an electron‐accumulated active site for extracting the photogenerated electrons on the BiOBr surface and for effectively activating the CO2 molecules.As a result,Bi_(19)S_(27)Br_(3)/BiOBr composites exhibit the higher charge carrier transfer efficiency and further improves the CO_(2)photoreduction performance relative to that of pure Bi_(19)S_(27)Br_(3)and BiOBr.The rate of CO formation using Bi_(19)S_(27)Br_(3)/BiOBr‐5 is about 8.74 and 2.40 times that using Bi_(19)S_(27)Br_(3)and BiOBr,respectively.This work provides new insights for the application of Bi_(19)S_(27)Br_(3)as an electron‐accumulating site for achieving high photocatalytic CO2 reduction performance in the future.展开更多
The boundary between subtropical zone and temperate zone is not only important in physical geography, but also attractive in agricultural production. Seven soil profiles studied in this pape...The boundary between subtropical zone and temperate zone is not only important in physical geography, but also attractive in agricultural production. Seven soil profiles studied in this paper are placed along the southern slope of Funiu Mountain at different heights above sea level. Many compositions and properties of these soils have been determined in laboratory. In this paper, the laws of migration and accumulation of soil materials on the southern slope of Funiu Mountain are discussed first, then the division of the boundary between subtropical zone and temperate zone in this area according to soil geochemistry is discussed with qualitative methods and mathematical classification method in which twelve selected indexes such as K m , Saf, Ba, β, Feo/Fet, Mno/Mnt and so on are used. The result indicates that the boundary between subtropical zone and temperate zone on the southern slope of Funiu Mountain is about 950 m above sea level.展开更多
Accumulative roll bonded （ARB） Copper Niobium （Cu-Nb） nano-lamellar composite （NLC） panels were friction stir welded （FSWed） to evaluate the ability to join panels while retaining the nano-lamellar structure. ...Accumulative roll bonded （ARB） Copper Niobium （Cu-Nb） nano-lamellar composite （NLC） panels were friction stir welded （FSWed） to evaluate the ability to join panels while retaining the nano-lamellar structure. During a single pass of the friction stir welding （FSW） process, the nano-lamellar structure of the parent material （PM） was retained but was observed to fragment into equiaxed grains during the second pass. FSW has been modeled as a severe deformation process in which the material is subjected to an instantaneous high shear strain rate followed by extreme shear strains. The loss of the nano-lamellar layers was attributed to the increased strain and longer time at temperature resulting from the second pass of the FSW process. Kinematic modeling was used to predict the global average shear strain and shear strain rates experienced by the ARB material during the FSW process. The results of this study indicate that through careful selection of FSW parameters, the nano-lamellar structure and its associated higher strength can be maintained using FSW to join ARB NLC panels.展开更多
The maize mixture feeding with a large mass cannot be migrated backward rapidly along the planar reciprocating vibrating screen,and it is easy to accumulate in the front of the screen,which leads to the decrease of sc...The maize mixture feeding with a large mass cannot be migrated backward rapidly along the planar reciprocating vibrating screen,and it is easy to accumulate in the front of the screen,which leads to the decrease of screening efficiency.Based on the reverse engineering technology,using the wavy geometry formed during the earthworm(Pheretima guillelmi)moving as a bionic prototype,a bionic screen was designed to make the maize mixture migrate backward rapidly in the front of the screen.The contour curve of earthworm’s head in an axial contracted state was extracted and fitted to obtain its equation.Based on the difference of concave position of the lower surface’s wavy geometry during the earthworm moving,the motion of the bionic screen was divided into four postures,and the conversion between different postures of the bionic screen was realized by the cam drive mechanism.The kinematics simulation of the bionic screen was carried out through ADAMS,and the displacement and velocity of the bionic screen were analyzed.When the feeding mass of the maize mixture was set at 5 kg/s,6 kg/s and 7 kg/s,the test results showed that the time of the maize mixture migrated(TOMMM)in the front of the bionic screen was shortened by 0.18 s,0.71 s,and 1.36 s,respectively,compared with that of planar reciprocating vibrating screen.The total screening time(TST)of the bionic screen was shortened by 1.28 s,1.33 s,and 1.53 s,respectively.The ability of the maize mixture to be migrated backward was improved.This study can provide a reference for the innovative design of the cleaning screen.展开更多
文摘In the aerospace field,hole burnishing enhancement plays an essential role in improving the service performance of load-bearing holes.To satisfy the assembly accuracy and strength requirements,the structure shape and surface integrity must be considered simultaneously during the enhancement process.The current manufacturing process of hole burnishing has a relatively weak balance between the structure shape and surface integrity;therefore,it is necessary to analyze the mechanism and optimize the parameters to improve the strengthening effect of the holes.In this study,a two-dimensional longitudinal simplified model for the hole burnishing process was established,and the reasons for the surface roughness improvement of the hole wall and material accumulation on the upper surface were analyzed.Experiments were conducted to determine the influence of the burnishing parameters on the structure shape(material accumulation,shape contour,and roundness)and surface integrity(surface roughness,residual stress,and surface hardness),based on the opposite requirements of improving the structure shape and surface integrity for the burnishing depth(BD).The results showed that with an increase in the BD,the structure shape deteriorated,whereas the surface integrity improved.Fatigue behavior verification experiments were conducted,and parameter selection schemes for the collaborative improvement of the structure shape and surface integrity were discussed.For the holes of titanium alloy TB6(Ti-10V-2Fe-3Al),the fatigue life can be increased by 162%when the BD,spindle speed,and feed rate were 0.20 mm,200 r/min,and 0.2 mm/r,respectively.
文摘Although CO_(2)photoreduction is a promising method for solar‐to‐fuel conversion,it suffers from low charge transfer efficiency of the photocatalysts.To improve the CO_(2)photoreduction performance,introduction of electron‐accumulated materials on the photocatalyst surface is considered an effective method.In this study,the Bi_(19)S_(27)Br_(3)/BiOBr composites were designed and synthesized.The Bi19S27Br3 nanorod in this photocatalytic system acts as an electron‐accumulated active site for extracting the photogenerated electrons on the BiOBr surface and for effectively activating the CO2 molecules.As a result,Bi_(19)S_(27)Br_(3)/BiOBr composites exhibit the higher charge carrier transfer efficiency and further improves the CO_(2)photoreduction performance relative to that of pure Bi_(19)S_(27)Br_(3)and BiOBr.The rate of CO formation using Bi_(19)S_(27)Br_(3)/BiOBr‐5 is about 8.74 and 2.40 times that using Bi_(19)S_(27)Br_(3)and BiOBr,respectively.This work provides new insights for the application of Bi_(19)S_(27)Br_(3)as an electron‐accumulating site for achieving high photocatalytic CO2 reduction performance in the future.
基金National Natural Science Foundation of China No.49070028
文摘The boundary between subtropical zone and temperate zone is not only important in physical geography, but also attractive in agricultural production. Seven soil profiles studied in this paper are placed along the southern slope of Funiu Mountain at different heights above sea level. Many compositions and properties of these soils have been determined in laboratory. In this paper, the laws of migration and accumulation of soil materials on the southern slope of Funiu Mountain are discussed first, then the division of the boundary between subtropical zone and temperate zone in this area according to soil geochemistry is discussed with qualitative methods and mathematical classification method in which twelve selected indexes such as K m , Saf, Ba, β, Feo/Fet, Mno/Mnt and so on are used. The result indicates that the boundary between subtropical zone and temperate zone on the southern slope of Funiu Mountain is about 950 m above sea level.
基金supported by the Los Alamos National Laboratory Directed Research and Development (LDRD) project 20130764ECR
文摘Accumulative roll bonded （ARB） Copper Niobium （Cu-Nb） nano-lamellar composite （NLC） panels were friction stir welded （FSWed） to evaluate the ability to join panels while retaining the nano-lamellar structure. During a single pass of the friction stir welding （FSW） process, the nano-lamellar structure of the parent material （PM） was retained but was observed to fragment into equiaxed grains during the second pass. FSW has been modeled as a severe deformation process in which the material is subjected to an instantaneous high shear strain rate followed by extreme shear strains. The loss of the nano-lamellar layers was attributed to the increased strain and longer time at temperature resulting from the second pass of the FSW process. Kinematic modeling was used to predict the global average shear strain and shear strain rates experienced by the ARB material during the FSW process. The results of this study indicate that through careful selection of FSW parameters, the nano-lamellar structure and its associated higher strength can be maintained using FSW to join ARB NLC panels.
基金This work was supported by the National Natural Science Foundation of China(Grant No.52075091,51475090)the Heilongjiang Provincial Natural Science Foundation of China(Grant No.E2017004).
文摘The maize mixture feeding with a large mass cannot be migrated backward rapidly along the planar reciprocating vibrating screen,and it is easy to accumulate in the front of the screen,which leads to the decrease of screening efficiency.Based on the reverse engineering technology,using the wavy geometry formed during the earthworm(Pheretima guillelmi)moving as a bionic prototype,a bionic screen was designed to make the maize mixture migrate backward rapidly in the front of the screen.The contour curve of earthworm’s head in an axial contracted state was extracted and fitted to obtain its equation.Based on the difference of concave position of the lower surface’s wavy geometry during the earthworm moving,the motion of the bionic screen was divided into four postures,and the conversion between different postures of the bionic screen was realized by the cam drive mechanism.The kinematics simulation of the bionic screen was carried out through ADAMS,and the displacement and velocity of the bionic screen were analyzed.When the feeding mass of the maize mixture was set at 5 kg/s,6 kg/s and 7 kg/s,the test results showed that the time of the maize mixture migrated(TOMMM)in the front of the bionic screen was shortened by 0.18 s,0.71 s,and 1.36 s,respectively,compared with that of planar reciprocating vibrating screen.The total screening time(TST)of the bionic screen was shortened by 1.28 s,1.33 s,and 1.53 s,respectively.The ability of the maize mixture to be migrated backward was improved.This study can provide a reference for the innovative design of the cleaning screen.
