Professors Mohazzbi and Luo [1] published “Despite several attempts have been made to explain the twin paradox … none of the explanations … resolved the paradox. If the paradox can be ever resolved, it requires a m...Professors Mohazzbi and Luo [1] published “Despite several attempts have been made to explain the twin paradox … none of the explanations … resolved the paradox. If the paradox can be ever resolved, it requires a much deeper understanding … of the theory of relativity”. The deeper understanding of resolving the paradox is by applying more explicit definitions of proper time interval, Lorentz transform, time dilation, and aging time.展开更多
The large storage requirement is a critical issue in cross-correlation imaging-condition based reverse time migration(RTM),because it requires the operation of the source and receiver wavefields at the same time.The b...The large storage requirement is a critical issue in cross-correlation imaging-condition based reverse time migration(RTM),because it requires the operation of the source and receiver wavefields at the same time.The boundary value method(BVM),based on the finite difference method(FDM),can be used to reconstruct the source wavefield in the reverse time propagation in the same way as the receiver wavefield,which can reduce the storage burden of the RTM data.Considering that the FDM cannot well handle models with discontinuous material properties and rough interfaces,we develop a source wavefield reconstruction strategy based on the finite element method(FEM),using proper orthogonal decomposition(POD)to enhance computational efficiency.In this method,we divide the whole time period into several segments,and construct the POD basis functions to get a reduced order model(ROM)for the source wavefield reconstruction in each segment.We show the corresponding quantitative analysis of the storage requirement of the POD-FEM.Numerical tests on the homogeneous model show the effectiveness of the proposed method,while the layered model and part of the Marmousi model tests indicate that the POD-FEM can keep an excellent balance between computational efficiency and memory usage compared with the full-stored method(FSM)and the BVM,and can be effectively applied in imaging.展开更多
The influence of the distribution of nano-pores on the mechanical properties evaluation of porous low-k films by surface acoustic waves （SAW） is studied. A theoretical SAW propagation model is set up to characterize...The influence of the distribution of nano-pores on the mechanical properties evaluation of porous low-k films by surface acoustic waves （SAW） is studied. A theoretical SAW propagation model is set up to characterize the periodic porous dielectrics by transversely isotropic symmetry. The theoretical deductions of SAW propagating in the low-k film/Si substrate layered structure are given in detail. The dispersive characteristics of SAW in differ- ent propagation directions and the effects of the Young＇s moduli E, E′ and shear modulus G′ of the films on these dispersive curves are found. Computational results show that E′ and G′ cannot be measured along the propagation direction that is perpendicular to the nano-pores＇ direction.展开更多
Let f be a proper edge coloring of G using k colors. For each x ∈ V（G）, the set of the colors appearing on the edges incident with x is denoted by Sf（x） or simply S（x） if no confusion arise. If S（u） = S（v） ...Let f be a proper edge coloring of G using k colors. For each x ∈ V（G）, the set of the colors appearing on the edges incident with x is denoted by Sf（x） or simply S（x） if no confusion arise. If S（u） = S（v） and S（v） S（u） for any two adjacent vertices u and v, then f is called a Smarandachely adjacent vertex distinguishing proper edge col- oring using k colors, or k-SA-edge coloring. The minimum number k for which G has a Smarandachely adjacent-vertex-distinguishing proper edge coloring using k colors is called the Smarandachely adjacent-vertex-distinguishing proper edge chromatic number, or SA- edge chromatic number for short, and denoted by Xsa（G）. In this paper, we have discussed the SA-edge chromatic number of K4 V Kn.展开更多
Magnesia chrome bricks were prepared with fiLsed MgO- Cr2 O3 synthesized material, fused magnesite and ：hrome ore as main starting materials. Nano-Al2O3 was tdded into refractories （ 2% , 4% and 6% in mass ） ;ubst...Magnesia chrome bricks were prepared with fiLsed MgO- Cr2 O3 synthesized material, fused magnesite and ：hrome ore as main starting materials. Nano-Al2O3 was tdded into refractories （ 2% , 4% and 6% in mass ） ;ubstit,ting for Al203 micropowder. After m＆ing and ;haping, the bricks were fired at 1 550 ℃, 1 600 91℃, t 650 ℃ and 1 750℃, respectively. The microstruc-ure , sintering property, mechanical properties, thermal ;kock resistance and shtg resistance of the specimens with he addition of nano-Al2O3 were investigated. The results indicate that the performance of brick with 4 mass% of nano-Al2O3 is greatly improred afier firing at 1 650 ℃.展开更多
In this study, nano ferrite materials were produced to replace costive industrial materials<span style="font-family:;" "=""> </span><span style="font-family:Verdana;"&...In this study, nano ferrite materials were produced to replace costive industrial materials<span style="font-family:;" "=""> </span><span style="font-family:Verdana;"><span style="font-size:10.0pt;font-family:" color:#943634;"=""><span style="font-family:Verdana;white-space:normal;">[1]</span></span><span style="font-size:10.0pt;font-family:;" "=""></span><span style="font-size:10.0pt;font-family:" times="" new="" roman","serif";"=""><span></span></span></span><span></span><span><span></span></span><span style="font-family:Verdana;">.</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">Ferrite nanoparticles are the interesting material due to their rich and unique physical and chemical properties. They find applications in catalysis, bio-processing, medicine, magnetic recording, adsorption, devices etc.</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Using co-participation method, five nano ferrite samples Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> (x = 0.00, 0.10, 0.20, 0.30 and 0.40) were prepared. The electrical and optical properties of the Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> samples were studied using the Ultraviolet-visible (UV-Vis) spectroscopy. The results verified that the formation of the absorption coefficient of the five samples of Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> increased with the increase of Lithium (Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">). The energy band gap of the Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> samples ranged </span></span><span style="font-family:Verdana;">from</span><span style="font-family:Verdana;"> 3.28 to 3.12</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">eV</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">[1]</span><span style="font-family:;" "=""></span><span style="font-family:" minion="" pro="" capt","serif";"=""><span></span></span><span style="font-family:Verdana;">.</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">The extinction coefficient (K) for five samples of Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> increased with the increase of Lithium (Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">) at 338 nm f</span></span><span style="font-family:Verdana;">ro</span><span style="font-family:Verdana;">m 0.074 to 0.207. The high magnitude of optical conductivity is (1.34</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">×</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">10</span><sup><span style="font-family:Verdana;">12</span></sup><span style="font-family:Verdana;"> sec<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;">) and the maximum value of electrical conductivity is 42</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">(Ω<sup>.</sup></span><span style="font-family:;" "=""><span><span style="font-family:Verdana;">cm)<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;">. This may due to the electrical and optical properties of lithium.</span></span></span>展开更多
Proper meshing of Hy-Vo silent chain and sprocket is important for realizing the transmission of the silent chain with more efficiency and less noise. Based on the study of the meshing theory of the Hy-Vo silent chain...Proper meshing of Hy-Vo silent chain and sprocket is important for realizing the transmission of the silent chain with more efficiency and less noise. Based on the study of the meshing theory of the Hy-Vo silent chain with the sprocket and the roll cutting machining principle of the sprocket with the hob, the proper conditions of the meshing for the Hy-Vo silent chain and the sprocket are put forward with the variable pitch characteristic of the Hy-Vo silent chain taken into consideration, and the proper meshing design method on the condition that the value of the link tooth pressure angle is unequal to the value of the sprocket tooth pressure angle is studied. Experiments show that this new design method is feasible. In addition, the design of the pitch, the sprocket tooth pressure angle and the fillet radius of the sprocket addendum circle are studied. It is crucial for guiding the design of the hob which cuts the Hy-Vo silent chain sprocket.展开更多
Some properties of convex cones are obtained and are used to derive several equivalent conditions as well as another important property for nearly cone-subconvexlike set-valued functions. Under the assumption of nearl...Some properties of convex cones are obtained and are used to derive several equivalent conditions as well as another important property for nearly cone-subconvexlike set-valued functions. Under the assumption of nearly cone-subconvexlikeness,a Lagrangian multiplier theorem on Benson proper efficiency is presented. Related results are generalized.展开更多
To improve the accuracy and reduce the calcu- lation cost for the inverse problem of centrifugal pump impeller, the new inverse method based on proper orthog- onal decomposition （POD） is proposed. The pump blade sha...To improve the accuracy and reduce the calcu- lation cost for the inverse problem of centrifugal pump impeller, the new inverse method based on proper orthog- onal decomposition （POD） is proposed. The pump blade shape is parameterized by quartic Bezier curve, and the initial snapshots is generated by introducing the perturbation of the blade shape control parameters. The internal flow field and its hydraulic performance is predicted by CFD method. The snapshots vector includes the blade shape parameter and the distribution of blade load. The POD basis for the snap- shots set are deduced by proper orthogonal decomposition. The sample vector set is expressed in terms of the linear combination of the orthogonal basis. The objective blade shape corresponding to the objective distribution of blade load is obtained by least square fit. The Iterative correction algorithm for the centrifugal pump blade inverse method based on POD is proposed. The objective blade load dis- tributions are corrected according to the difference of the CFD result and the POD result. The two dimensional and three dimensional blade calculation cases show that the proposed centrifugal pump blade inverse method based on POD have good convergence and high accuracy, and thecalculation cost is greatly reduced. After two iterations, the deviation of the blade load and the pump hydraulic perfor- mance are limited within 4.0% and 6.0% individually for most of the flow rate range. This paper provides a promising inverse method for centrifugal pump impeller, which will benefit the hydraulic optimization of centrifugal pump.展开更多
Proper Orthogonal Decomposition （POD） provides a powerful modal transformation tool for stochastic dynamics. In this paper, coherency matrix-based proper orthogonal decomposition （CPOD） is presented as an innovati...Proper Orthogonal Decomposition （POD） provides a powerful modal transformation tool for stochastic dynamics. In this paper, coherency matrix-based proper orthogonal decomposition （CPOD） is presented as an innovative form of the POD based on cross power spectral density matrices. By introducing a discretizing scheme, the CPOD-based spectral representation method is obtained for use in stochastic simulation. Moreover, some criteria are proposed that allow the truncation order of CPOD to be conveniently determined. A numerical example to illustrate the application of the proposed method for the simulation of a wind velocity field is provided.展开更多
Time-resolved particle image velocimetry（TRPIV） experiments are performed to investigate the coherent structure＇s performance of riblets in a turbulent boundary layer（TBL） at a friction Reynolds number of 185. To...Time-resolved particle image velocimetry（TRPIV） experiments are performed to investigate the coherent structure＇s performance of riblets in a turbulent boundary layer（TBL） at a friction Reynolds number of 185. To visualize the energetic large-scale coherent structures（CSs） over a smooth surface and riblets, the proper orthogonal decomposition（POD） and finite-time Lyapunov exponent（FTLE） are used to identify the CSs in the TBL. Spatial-temporal correlation is implemented to obtain the characters and transport properties of typical CSs in the FTLE fields. The results demonstrate that the generic flow structures, such as hairpin-like vortices, are also observed in the boundary layer flow over the riblets, consistent with its smooth counterpart. Low-order POD modes are more sensitive to the riblets in comparison with the high-order ones,and the wall-normal movement of the most energy-containing structures are suppressed over riblets. The spatial correlation analysis of the FTLE fields indicates that the evolution process of the hairpin vortex over riblets are inhibited. An apparent decrease of the convection velocity over riblets is noted, which is believed to reduce the ejection/sweep motions associated with high shear stress from the viscous sublayer. These reductions exhibit inhibition of momentum transfer among the structures near the wall in the TBL flows.展开更多
文摘Professors Mohazzbi and Luo [1] published “Despite several attempts have been made to explain the twin paradox … none of the explanations … resolved the paradox. If the paradox can be ever resolved, it requires a much deeper understanding … of the theory of relativity”. The deeper understanding of resolving the paradox is by applying more explicit definitions of proper time interval, Lorentz transform, time dilation, and aging time.
基金This work was supported by Natural Science Basic Research Program of Shaanxi(Program No.2023-JC-YB-269)the National Natural Science Foundation of China(Grant No.41974122).
文摘The large storage requirement is a critical issue in cross-correlation imaging-condition based reverse time migration(RTM),because it requires the operation of the source and receiver wavefields at the same time.The boundary value method(BVM),based on the finite difference method(FDM),can be used to reconstruct the source wavefield in the reverse time propagation in the same way as the receiver wavefield,which can reduce the storage burden of the RTM data.Considering that the FDM cannot well handle models with discontinuous material properties and rough interfaces,we develop a source wavefield reconstruction strategy based on the finite element method(FEM),using proper orthogonal decomposition(POD)to enhance computational efficiency.In this method,we divide the whole time period into several segments,and construct the POD basis functions to get a reduced order model(ROM)for the source wavefield reconstruction in each segment.We show the corresponding quantitative analysis of the storage requirement of the POD-FEM.Numerical tests on the homogeneous model show the effectiveness of the proposed method,while the layered model and part of the Marmousi model tests indicate that the POD-FEM can keep an excellent balance between computational efficiency and memory usage compared with the full-stored method(FSM)and the BVM,and can be effectively applied in imaging.
文摘The influence of the distribution of nano-pores on the mechanical properties evaluation of porous low-k films by surface acoustic waves （SAW） is studied. A theoretical SAW propagation model is set up to characterize the periodic porous dielectrics by transversely isotropic symmetry. The theoretical deductions of SAW propagating in the low-k film/Si substrate layered structure are given in detail. The dispersive characteristics of SAW in differ- ent propagation directions and the effects of the Young＇s moduli E, E′ and shear modulus G′ of the films on these dispersive curves are found. Computational results show that E′ and G′ cannot be measured along the propagation direction that is perpendicular to the nano-pores＇ direction.
基金Supported by NNSF of China(61163037,61163054,61363060)
文摘Let f be a proper edge coloring of G using k colors. For each x ∈ V（G）, the set of the colors appearing on the edges incident with x is denoted by Sf（x） or simply S（x） if no confusion arise. If S（u） = S（v） and S（v） S（u） for any two adjacent vertices u and v, then f is called a Smarandachely adjacent vertex distinguishing proper edge col- oring using k colors, or k-SA-edge coloring. The minimum number k for which G has a Smarandachely adjacent-vertex-distinguishing proper edge coloring using k colors is called the Smarandachely adjacent-vertex-distinguishing proper edge chromatic number, or SA- edge chromatic number for short, and denoted by Xsa（G）. In this paper, we have discussed the SA-edge chromatic number of K4 V Kn.
文摘Magnesia chrome bricks were prepared with fiLsed MgO- Cr2 O3 synthesized material, fused magnesite and ：hrome ore as main starting materials. Nano-Al2O3 was tdded into refractories （ 2% , 4% and 6% in mass ） ;ubstit,ting for Al203 micropowder. After m＆ing and ;haping, the bricks were fired at 1 550 ℃, 1 600 91℃, t 650 ℃ and 1 750℃, respectively. The microstruc-ure , sintering property, mechanical properties, thermal ;kock resistance and shtg resistance of the specimens with he addition of nano-Al2O3 were investigated. The results indicate that the performance of brick with 4 mass% of nano-Al2O3 is greatly improred afier firing at 1 650 ℃.
文摘In this study, nano ferrite materials were produced to replace costive industrial materials<span style="font-family:;" "=""> </span><span style="font-family:Verdana;"><span style="font-size:10.0pt;font-family:" color:#943634;"=""><span style="font-family:Verdana;white-space:normal;">[1]</span></span><span style="font-size:10.0pt;font-family:;" "=""></span><span style="font-size:10.0pt;font-family:" times="" new="" roman","serif";"=""><span></span></span></span><span></span><span><span></span></span><span style="font-family:Verdana;">.</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">Ferrite nanoparticles are the interesting material due to their rich and unique physical and chemical properties. They find applications in catalysis, bio-processing, medicine, magnetic recording, adsorption, devices etc.</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Using co-participation method, five nano ferrite samples Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> (x = 0.00, 0.10, 0.20, 0.30 and 0.40) were prepared. The electrical and optical properties of the Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> samples were studied using the Ultraviolet-visible (UV-Vis) spectroscopy. The results verified that the formation of the absorption coefficient of the five samples of Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> increased with the increase of Lithium (Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">). The energy band gap of the Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> samples ranged </span></span><span style="font-family:Verdana;">from</span><span style="font-family:Verdana;"> 3.28 to 3.12</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">eV</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">[1]</span><span style="font-family:;" "=""></span><span style="font-family:" minion="" pro="" capt","serif";"=""><span></span></span><span style="font-family:Verdana;">.</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">The extinction coefficient (K) for five samples of Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> increased with the increase of Lithium (Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">) at 338 nm f</span></span><span style="font-family:Verdana;">ro</span><span style="font-family:Verdana;">m 0.074 to 0.207. The high magnitude of optical conductivity is (1.34</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">×</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">10</span><sup><span style="font-family:Verdana;">12</span></sup><span style="font-family:Verdana;"> sec<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;">) and the maximum value of electrical conductivity is 42</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">(Ω<sup>.</sup></span><span style="font-family:;" "=""><span><span style="font-family:Verdana;">cm)<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;">. This may due to the electrical and optical properties of lithium.</span></span></span>
基金This project is supported by National Natural Science Foundation of China(No.50575089).
文摘Proper meshing of Hy-Vo silent chain and sprocket is important for realizing the transmission of the silent chain with more efficiency and less noise. Based on the study of the meshing theory of the Hy-Vo silent chain with the sprocket and the roll cutting machining principle of the sprocket with the hob, the proper conditions of the meshing for the Hy-Vo silent chain and the sprocket are put forward with the variable pitch characteristic of the Hy-Vo silent chain taken into consideration, and the proper meshing design method on the condition that the value of the link tooth pressure angle is unequal to the value of the sprocket tooth pressure angle is studied. Experiments show that this new design method is feasible. In addition, the design of the pitch, the sprocket tooth pressure angle and the fillet radius of the sprocket addendum circle are studied. It is crucial for guiding the design of the hob which cuts the Hy-Vo silent chain sprocket.
文摘Some properties of convex cones are obtained and are used to derive several equivalent conditions as well as another important property for nearly cone-subconvexlike set-valued functions. Under the assumption of nearly cone-subconvexlikeness,a Lagrangian multiplier theorem on Benson proper efficiency is presented. Related results are generalized.
基金Supported by National Natural Science Foundation of China(Grant Nos.51469014,51676003)National Key Research and Development Program of China(Grant No.20016YFB0200901)
文摘To improve the accuracy and reduce the calcu- lation cost for the inverse problem of centrifugal pump impeller, the new inverse method based on proper orthog- onal decomposition （POD） is proposed. The pump blade shape is parameterized by quartic Bezier curve, and the initial snapshots is generated by introducing the perturbation of the blade shape control parameters. The internal flow field and its hydraulic performance is predicted by CFD method. The snapshots vector includes the blade shape parameter and the distribution of blade load. The POD basis for the snap- shots set are deduced by proper orthogonal decomposition. The sample vector set is expressed in terms of the linear combination of the orthogonal basis. The objective blade shape corresponding to the objective distribution of blade load is obtained by least square fit. The Iterative correction algorithm for the centrifugal pump blade inverse method based on POD is proposed. The objective blade load dis- tributions are corrected according to the difference of the CFD result and the POD result. The two dimensional and three dimensional blade calculation cases show that the proposed centrifugal pump blade inverse method based on POD have good convergence and high accuracy, and thecalculation cost is greatly reduced. After two iterations, the deviation of the blade load and the pump hydraulic perfor- mance are limited within 4.0% and 6.0% individually for most of the flow rate range. This paper provides a promising inverse method for centrifugal pump impeller, which will benefit the hydraulic optimization of centrifugal pump.
基金Research Fund for Communications in Western China Under Grant No. 200431800028
文摘Proper Orthogonal Decomposition （POD） provides a powerful modal transformation tool for stochastic dynamics. In this paper, coherency matrix-based proper orthogonal decomposition （CPOD） is presented as an innovative form of the POD based on cross power spectral density matrices. By introducing a discretizing scheme, the CPOD-based spectral representation method is obtained for use in stochastic simulation. Moreover, some criteria are proposed that allow the truncation order of CPOD to be conveniently determined. A numerical example to illustrate the application of the proposed method for the simulation of a wind velocity field is provided.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11332006,11732010,11572221,and 11502066)the Natural Science Foundation of Tianjin City(Grant No.18JCQNJC5100)
文摘Time-resolved particle image velocimetry（TRPIV） experiments are performed to investigate the coherent structure＇s performance of riblets in a turbulent boundary layer（TBL） at a friction Reynolds number of 185. To visualize the energetic large-scale coherent structures（CSs） over a smooth surface and riblets, the proper orthogonal decomposition（POD） and finite-time Lyapunov exponent（FTLE） are used to identify the CSs in the TBL. Spatial-temporal correlation is implemented to obtain the characters and transport properties of typical CSs in the FTLE fields. The results demonstrate that the generic flow structures, such as hairpin-like vortices, are also observed in the boundary layer flow over the riblets, consistent with its smooth counterpart. Low-order POD modes are more sensitive to the riblets in comparison with the high-order ones,and the wall-normal movement of the most energy-containing structures are suppressed over riblets. The spatial correlation analysis of the FTLE fields indicates that the evolution process of the hairpin vortex over riblets are inhibited. An apparent decrease of the convection velocity over riblets is noted, which is believed to reduce the ejection/sweep motions associated with high shear stress from the viscous sublayer. These reductions exhibit inhibition of momentum transfer among the structures near the wall in the TBL flows.
