Size-controlled synthesis of two-dimensional(2D)catalysts with low stacking numbers and small nanoflake lengths is crucial for promoting the catalytic performance in diverse heterogeneous catalysis.Herein,we report a ...Size-controlled synthesis of two-dimensional(2D)catalysts with low stacking numbers and small nanoflake lengths is crucial for promoting the catalytic performance in diverse heterogeneous catalysis.Herein,we report a facile and general“surface curvature-confined synthesis”strategy to modulate the slab lengths and stacking numbers of 2D transition metal sulfides by controlling the strain induced by different surface curvature of supports.An efficient NiMo sulfide with shorter slab length(average 3.71 nm),less stacking number(1–2 layers)and more edge active sites is synthesized onto ZSM-5 zeolites with the average size of 100 nm,which shows superior kHDS value of dibenzothiophene(14.05×10^−7 mol/(g·s)),enhanced stability up to 80 h,and high direct desulfurization selectivity(>95%).This design concept is also proved to be generally applicable to modulate the slab lengths and stacking numbers of other 2D catalysts such as MoS2 and WS2 nanoflakes,which shows great potentials for developing more ultrasmall 2D catalysts with controlled sizes and excellent catalytic activities.展开更多
The unique Coanda surface has a great influence on the performance of bladeless fan.However,there is few studies to explain the relationship between the performance and Coanda surface curvature at present.In order to ...The unique Coanda surface has a great influence on the performance of bladeless fan.However,there is few studies to explain the relationship between the performance and Coanda surface curvature at present.In order to gain a qualitative understanding of effect of the curvature on the performance of bladeless fan,numerical studies are performed in this paper.Firstly,three-dimensional numerical simulation is done by Fluent software.For the purpose to obtain detailed information of the flow field around the Coanda surface,two-dimensional numerical simulation is also conducted.Five types of Coanda surfaces with different curvature are designed,and the flow behaviour and the performance of them are analyzed and compared with those of the prototype.The analysis indicates that the curvature of Coanda surface is strongly related to blowing performance,It is found that there is an optimal curvature of Coanda surfaces among the studied models.Simulation result shows that there is a special low pressure region.With increasing curvature in Y direction,several low pressure regions gradually enlarged,then begin to merge slowly,and finally form a large area of low pressure.From the analyses of streamlines and velocity angle,it is found that the magnitude of the curvature affects the flow direction and reasonable curvature can induce fluid flow close to the wall.Thus,it leads to that the curvature of the streamlines is consistent with that of Coanda surface.Meanwhile,it also causes the fluid movement towards the most suitable direction.This study will provide useful information to performance improvements of bladeless fans.展开更多
In this paper, we establish a rigidity theorem for compact constant mean curva- ture surfaces of the Berger sphere in terms of the surfaces＇ geometric invariants. This extends the previous similar result on compact m...In this paper, we establish a rigidity theorem for compact constant mean curva- ture surfaces of the Berger sphere in terms of the surfaces＇ geometric invariants. This extends the previous similar result on compact minimal surfaces of the Berger sphere.展开更多
Though the Bǎcklund transformation on time-like surfaces with constant mean curvature surfaces in R^2,1 has been obtained, it is not easy to obtain corresponding surfaces because the procedure of solving the related ...Though the Bǎcklund transformation on time-like surfaces with constant mean curvature surfaces in R^2,1 has been obtained, it is not easy to obtain corresponding surfaces because the procedure of solving the related integrable system cannot be avoided when the Bǎcklund transformation is used, For sake of this, in this article, some special work is done to reform the Bǎcklund transformation to a recursion formula, by which we can construct time-like surfaces with constant mean curvature form known ones just by quadrature procedure.展开更多
Jet force on the surface is typical for impinging jets towards the surface and it is very important in drying applications for force-sensitive surfaces. The designer should optimize the design parameters of industrial...Jet force on the surface is typical for impinging jets towards the surface and it is very important in drying applications for force-sensitive surfaces. The designer should optimize the design parameters of industrial drying equipment to achieve minimum pressure force between multiple jets and a moving curved surface. SST <em>k-ω</em> turbulence model is used to simulate a real geometry for industrial drying applications. The SST <em>k-ω</em> turbulence model succeeded with reasonable accuracy in reproducing the experimental results. The jet to surface distance, jet to jet spacing, jet inlet velocity, jet angle, and surface velocity are chosen as the design parameters. For the optimization of the impinging round jet, the pressure force coefficient on the moving curved surface is set as the objective function to be minimized. The SHERPA search algorithm is used to search for the optimal point from the weighted sum of all objectives method. One correlation is developed and validated for the pressure force coefficient. It is found that the pressure force coefficient is highly dependent on the nozzle to surface distance and jet angle but relatively insensitive to jet inlet velocity, jet to jet spacing, and surface velocity. The minimum pressure force coefficient correlates with a high value of nozzle to surface distance (tenfold diameter in this analysis) and a low value of the jet angle (40? in this analysis). The agreement in the prediction of the pressure force coefficient between the numerical simulation and developed correlation is found to be reasonable and all the data points deviate from the correlation approximately 8% on average.展开更多
The particle morphological properties,such as sphericity,concavity and convexity,of a granular assembly significantly affect its macroscopic and microscopic compressive behaviors under isotropic loading condition.Howe...The particle morphological properties,such as sphericity,concavity and convexity,of a granular assembly significantly affect its macroscopic and microscopic compressive behaviors under isotropic loading condition.However,limited studies on investigating the microscopic behavior of the granular assembly with real particle shapes under isotropic compression were reported.In this study,X-ray computed tomography(mCT)and discrete element modeling(DEM)were utilized to investigate isotropic compression behavior of the granular assembly with regard to the particle morphological properties,such as particle sphericity,concavity and interparticle frictions.The mCT was first used to extract the particle morphological parameters and then the DEM was utilized to numerically investigate the influences of the particle morphological properties on the isotropic compression behavior.The image reconstruction from mCT images indicated that the presented particle quantification algorithm was robust,and the presented microscopic analysis via the DEM simulation demonstrated that the particle surface concavity significantly affected the isotropic compression behavior.The observations of the particle connectivity and local void ratio distribution also provided insights into the granular assembly under isotropic compression.Results found that the particle concavity and interparticle friction influenced the most of the isotropic compression behavior of the granular assemblies.展开更多
We investigate the isoperimetric deficit upper bound, that is, the reverse Bonnesen style inequality for the convex domain in a surface X2 of constant curvature ε via the containment measure of a convex domain to con...We investigate the isoperimetric deficit upper bound, that is, the reverse Bonnesen style inequality for the convex domain in a surface X2 of constant curvature ε via the containment measure of a convex domain to contain another convex domain in integral geometry. We obtain some reverse Bonnesen style inequalities that extend the known Bottema＇s result in the Euclidean plane E2.展开更多
It is well known that a totally geodesic Lagrangian surface in a Lorentzian complex space form M12（4ε） of constant holomorphic sectional curvature 4s is of constant curvature 6. A natural question is ＂Besides tota...It is well known that a totally geodesic Lagrangian surface in a Lorentzian complex space form M12（4ε） of constant holomorphic sectional curvature 4s is of constant curvature 6. A natural question is ＂Besides totally geodesic ones how many Lagrangian surfaces of constant curvature εin M12（46） are there？＂ In an earlier paper an answer to this question was obtained for the case e = 0 by Chen and Fastenakels. In this paper we provide the answer to this question for the case ε≠0. Our main result states that there exist thirty-five families of Lagrangian surfaces of curvature ε in M12（4ε） with ε ≠ 0. Conversely, every Lagrangian surface of curvature ε≠0 in M12（4ε） is locally congruent to one of the Lagrangian surfaces given by the thirty-five families.展开更多
In order to find out the optimal press bend forming path in fabricating aircraft integral panels, this article proposes a new method on the basis of the authors＇ previous work. It is composed of the finite element me...In order to find out the optimal press bend forming path in fabricating aircraft integral panels, this article proposes a new method on the basis of the authors＇ previous work. It is composed of the finite element method （FEM） equivalent model, the surface curvature analysis, the artificial neural network response surface and the genetic algorithm. The method begins with analyzing the objective＇s shape curvature to determine the bending position. Then it optimizes the punch travel at each bending position by the following steps： （1） Establish a multi-step press bend forming FEM equivalent model, with which the FEM ex- periments designed with the Taguchi method are performed. （2） Construct a back-propagation （BP） neural network response surface with the data from the FEM experiments. （3） Use the genetic algorithm to optimize the neural network response surface as the objective function. Finally, this method is verified by press bending a complicated double-curvature grid-type stiffened panel and bears out its effectiveness and intrinsic worth in designing the press bend forming path.展开更多
基金This work was supported by the National Key R&D Program of China(No.2018YFE0201704)the National Natural Science Foundation of China(Nos.21631004,21801069,21571054,and 21901064)+2 种基金the Fundamental Research Funds for Central Universities(Nos.3072019CFJ1502 and RCYJTD201801)the University Program for Young Scholars with Creative Talents in Heilongjiang Province(No.UNPYSCT-2018013)Heilongjiang Provincial Postdoctoral Science Foundation(No.LBH-Z18232)and the Heilongjiang University Excellent Youth Foundation.
文摘Size-controlled synthesis of two-dimensional(2D)catalysts with low stacking numbers and small nanoflake lengths is crucial for promoting the catalytic performance in diverse heterogeneous catalysis.Herein,we report a facile and general“surface curvature-confined synthesis”strategy to modulate the slab lengths and stacking numbers of 2D transition metal sulfides by controlling the strain induced by different surface curvature of supports.An efficient NiMo sulfide with shorter slab length(average 3.71 nm),less stacking number(1–2 layers)and more edge active sites is synthesized onto ZSM-5 zeolites with the average size of 100 nm,which shows superior kHDS value of dibenzothiophene(14.05×10^−7 mol/(g·s)),enhanced stability up to 80 h,and high direct desulfurization selectivity(>95%).This design concept is also proved to be generally applicable to modulate the slab lengths and stacking numbers of other 2D catalysts such as MoS2 and WS2 nanoflakes,which shows great potentials for developing more ultrasmall 2D catalysts with controlled sizes and excellent catalytic activities.
基金supported by National Natural Science Foundation of China(No.51276172)National Science and TechnologySupport Project(No.2013BAF05B01)
文摘The unique Coanda surface has a great influence on the performance of bladeless fan.However,there is few studies to explain the relationship between the performance and Coanda surface curvature at present.In order to gain a qualitative understanding of effect of the curvature on the performance of bladeless fan,numerical studies are performed in this paper.Firstly,three-dimensional numerical simulation is done by Fluent software.For the purpose to obtain detailed information of the flow field around the Coanda surface,two-dimensional numerical simulation is also conducted.Five types of Coanda surfaces with different curvature are designed,and the flow behaviour and the performance of them are analyzed and compared with those of the prototype.The analysis indicates that the curvature of Coanda surface is strongly related to blowing performance,It is found that there is an optimal curvature of Coanda surfaces among the studied models.Simulation result shows that there is a special low pressure region.With increasing curvature in Y direction,several low pressure regions gradually enlarged,then begin to merge slowly,and finally form a large area of low pressure.From the analyses of streamlines and velocity angle,it is found that the magnitude of the curvature affects the flow direction and reasonable curvature can induce fluid flow close to the wall.Thus,it leads to that the curvature of the streamlines is consistent with that of Coanda surface.Meanwhile,it also causes the fluid movement towards the most suitable direction.This study will provide useful information to performance improvements of bladeless fans.
文摘In this paper, we establish a rigidity theorem for compact constant mean curva- ture surfaces of the Berger sphere in terms of the surfaces＇ geometric invariants. This extends the previous similar result on compact minimal surfaces of the Berger sphere.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10571149, 10571165, and 10101025 We are grateful to Sha Nan-Shi and Zhang Wen-Jing, who are both students in Department of Statistics and Finance, University of Science and Technology of China, for their valuable and creative ideas in stimulating discussions as well as conscientious work of computing.
文摘Though the Bǎcklund transformation on time-like surfaces with constant mean curvature surfaces in R^2,1 has been obtained, it is not easy to obtain corresponding surfaces because the procedure of solving the related integrable system cannot be avoided when the Bǎcklund transformation is used, For sake of this, in this article, some special work is done to reform the Bǎcklund transformation to a recursion formula, by which we can construct time-like surfaces with constant mean curvature form known ones just by quadrature procedure.
文摘Jet force on the surface is typical for impinging jets towards the surface and it is very important in drying applications for force-sensitive surfaces. The designer should optimize the design parameters of industrial drying equipment to achieve minimum pressure force between multiple jets and a moving curved surface. SST <em>k-ω</em> turbulence model is used to simulate a real geometry for industrial drying applications. The SST <em>k-ω</em> turbulence model succeeded with reasonable accuracy in reproducing the experimental results. The jet to surface distance, jet to jet spacing, jet inlet velocity, jet angle, and surface velocity are chosen as the design parameters. For the optimization of the impinging round jet, the pressure force coefficient on the moving curved surface is set as the objective function to be minimized. The SHERPA search algorithm is used to search for the optimal point from the weighted sum of all objectives method. One correlation is developed and validated for the pressure force coefficient. It is found that the pressure force coefficient is highly dependent on the nozzle to surface distance and jet angle but relatively insensitive to jet inlet velocity, jet to jet spacing, and surface velocity. The minimum pressure force coefficient correlates with a high value of nozzle to surface distance (tenfold diameter in this analysis) and a low value of the jet angle (40? in this analysis). The agreement in the prediction of the pressure force coefficient between the numerical simulation and developed correlation is found to be reasonable and all the data points deviate from the correlation approximately 8% on average.
基金the Universidad Nacional de San Agustín(UNSA)through the joint Center for Mining Sustainability with the Colorado School of Mines is highly acknowledged.
文摘The particle morphological properties,such as sphericity,concavity and convexity,of a granular assembly significantly affect its macroscopic and microscopic compressive behaviors under isotropic loading condition.However,limited studies on investigating the microscopic behavior of the granular assembly with real particle shapes under isotropic compression were reported.In this study,X-ray computed tomography(mCT)and discrete element modeling(DEM)were utilized to investigate isotropic compression behavior of the granular assembly with regard to the particle morphological properties,such as particle sphericity,concavity and interparticle frictions.The mCT was first used to extract the particle morphological parameters and then the DEM was utilized to numerically investigate the influences of the particle morphological properties on the isotropic compression behavior.The image reconstruction from mCT images indicated that the presented particle quantification algorithm was robust,and the presented microscopic analysis via the DEM simulation demonstrated that the particle surface concavity significantly affected the isotropic compression behavior.The observations of the particle connectivity and local void ratio distribution also provided insights into the granular assembly under isotropic compression.Results found that the particle concavity and interparticle friction influenced the most of the isotropic compression behavior of the granular assemblies.
基金supported by National Natural Science Foundation of China (Grant Nos.10971167, 11271302 and 11101336)
文摘We investigate the isoperimetric deficit upper bound, that is, the reverse Bonnesen style inequality for the convex domain in a surface X2 of constant curvature ε via the containment measure of a convex domain to contain another convex domain in integral geometry. We obtain some reverse Bonnesen style inequalities that extend the known Bottema＇s result in the Euclidean plane E2.
文摘It is well known that a totally geodesic Lagrangian surface in a Lorentzian complex space form M12（4ε） of constant holomorphic sectional curvature 4s is of constant curvature 6. A natural question is ＂Besides totally geodesic ones how many Lagrangian surfaces of constant curvature εin M12（46） are there？＂ In an earlier paper an answer to this question was obtained for the case e = 0 by Chen and Fastenakels. In this paper we provide the answer to this question for the case ε≠0. Our main result states that there exist thirty-five families of Lagrangian surfaces of curvature ε in M12（4ε） with ε ≠ 0. Conversely, every Lagrangian surface of curvature ε≠0 in M12（4ε） is locally congruent to one of the Lagrangian surfaces given by the thirty-five families.
基金Specialized Research Fund for the Doctoral Program of High Education of China (20091102110021)
文摘In order to find out the optimal press bend forming path in fabricating aircraft integral panels, this article proposes a new method on the basis of the authors＇ previous work. It is composed of the finite element method （FEM） equivalent model, the surface curvature analysis, the artificial neural network response surface and the genetic algorithm. The method begins with analyzing the objective＇s shape curvature to determine the bending position. Then it optimizes the punch travel at each bending position by the following steps： （1） Establish a multi-step press bend forming FEM equivalent model, with which the FEM ex- periments designed with the Taguchi method are performed. （2） Construct a back-propagation （BP） neural network response surface with the data from the FEM experiments. （3） Use the genetic algorithm to optimize the neural network response surface as the objective function. Finally, this method is verified by press bending a complicated double-curvature grid-type stiffened panel and bears out its effectiveness and intrinsic worth in designing the press bend forming path.
