The paper presents a 3D numerical simulation of turbulent heat transfer and flow characteristics in converging-diverging tubes (CDs) and converging-diverg)ng tubes.equi.pped with twin counter-swirling twisted tapes...The paper presents a 3D numerical simulation of turbulent heat transfer and flow characteristics in converging-diverging tubes (CDs) and converging-diverg)ng tubes.equi.pped with twin counter-swirling twisted tapes (CDTs). The effects of Reynolds number (Re= 10000-20000), pitch length (P= 11.25, 22.5 mm), rib height (e = 0.5, 0.8, 1.1 ram), pitch ratio (8= 1 " 8, 5 " 4, 8 " 1), gap distance between twin t)visted tapes (b = 0.5, 4.5, 8.5 mm) and tape number (n = 2, 3, 4, 5, 6) on Nusselt number (Nu), Iriction tactor 0') and thermal enhancement factor (r/) are investigated under uniform heat flux conditions,using water as working fluid. In order to illustrate the heat transter and tlu^d tlow mechamsms, flow structures m ~StJs and ~SDIs are presented. The obtained results reveal that all geometric parameters have important effects on the thermal performance of CD and CDT, and both CD and CDT show better thermal performance than plain tube at the constant pumping power. It is also found that the increases in the Nusselt number and friction factor for CDT are, respectively, up to 6.3%-35.7% and 1.75-5.3 times of thecorresponding bare CD. All CDTs have good thermal perbrmance with greater than 1 which indicates that the compound heat transfer technique of CDT is commendable for the maximum enhanced heat transfer rate.展开更多
The article not only presents the boundedness and compactness of the weighted composition operator from α-Bloch spaces(or little α-Bloch spaces) to H^∞, but also gives some estimates for the norm of the weighted ...The article not only presents the boundedness and compactness of the weighted composition operator from α-Bloch spaces(or little α-Bloch spaces) to H^∞, but also gives some estimates for the norm of the weighted composition operator.展开更多
In this paper, we define the weighted Dirichlet space D p α(Ω) on bounded symmetric domains Ω of C n. Using η-α Carleson measure,we study the boundedness and compactmess of the composition operators between the w...In this paper, we define the weighted Dirichlet space D p α(Ω) on bounded symmetric domains Ω of C n. Using η-α Carleson measure,we study the boundedness and compactmess of the composition operators between the weighted Dirichlet spaces.展开更多
We consider the weighted composition operators between Hardy spaces on the unit ball, and obtain some sufficient and necessary conditions of bounded or compact weighted composition operators. We also prove that the op...We consider the weighted composition operators between Hardy spaces on the unit ball, and obtain some sufficient and necessary conditions of bounded or compact weighted composition operators. We also prove that the operator from H^1 to H^1 is compact if and only if it is weakly compact. Meanwhile, we get the analogue on the Bergman spaces.展开更多
In this paper, we give a necessary and sufficient condition for weighted composition operators Cu,φ to be boundedness on Bloch type spaces B^α. The theorem generalizes some previous results.
In this paper, we propose a new spatial-multiplexing(SM) scheme employing an orthogonal precoder over Rayleigh-fading channels for an erasure event in single frequency networks(SFN). To optimize the precoder, the aver...In this paper, we propose a new spatial-multiplexing(SM) scheme employing an orthogonal precoder over Rayleigh-fading channels for an erasure event in single frequency networks(SFN). To optimize the precoder, the average bit error rate(BER) is evaluated and minimized through a mathematical analysis. Compared to an ordinary SM, the proposed scheme guarantees identical BER performance under non-erasure fading channels and achieves a greatly improved performance under erasure fading channels, especially for a higher erasure-ratio and SNR values. This improvement is mainly due to the increase in the diversity gain incurred by the optimized precoder over the erasure event. We also compare the performance of the proposed SM to that of the conventional constellation-rotation(CR) scheme applied to the single antenna SFN systems. The results of a computer simulation show that the performance of the new scheme is more effective than that of a conventional CR across all simulation cases.展开更多
The relation between composition operators on the Dirichlet spaces in the open unit disk and derivative weighted composition operators on the Bergman spaces in the open unit disk is investigated firstly,and for a comb...The relation between composition operators on the Dirichlet spaces in the open unit disk and derivative weighted composition operators on the Bergman spaces in the open unit disk is investigated firstly,and for a combination of several derivative weighted composition operators which acts on classic Bergman space,the lower bound of its essential norm is estimated in terms of the boundary data of the symbols of d-composition operators.Some similar results about composition operators on the Dirichlet space are also presented.A necessary condition is given to determine the compactness of the combination of several derivative weighted composition operators on Bergman spaces.展开更多
In order to investigate the boundedness or compactness of composition operator from the logarithmic Bloch-type space to the Bergman space on the unit polydisc, the classic Bergman norm is firstly changed into another ...In order to investigate the boundedness or compactness of composition operator from the logarithmic Bloch-type space to the Bergman space on the unit polydisc, the classic Bergman norm is firstly changed into another equivalent norm. Then according to some common inequalities, the properties of logarithmic Bloch-type space and the absolute continuity of the general integral, the conditions which the symbol map must meet when the composition operator is bounded or compact are obtained after a series of calculations, and the boundedness and compactness are proved to be equivalent.展开更多
In this paper,we give a fixed point theorem for multi-valued composite increasing operators,in partially ordered spaces,which generalizes the results of [1]-[3] and [5]- [8].
The coupled models of LBM (Lattice Boltzmann Method) and RANS (Reynolds-Averaged Navier-Stokes) are more practical for the transient simulation of mixing processes at large spatial and temporal scales such as crud...The coupled models of LBM (Lattice Boltzmann Method) and RANS (Reynolds-Averaged Navier-Stokes) are more practical for the transient simulation of mixing processes at large spatial and temporal scales such as crude oil mixing in large-diameter storage tanks. To keep the efficiency of parallel computation of LBM, the RANS model should also be explicitly solved; whereas to keep the numerical stability the implicit method should be better for PANS model. This article explores the numerical stability of explicit methods in 2D cases on one hand, and on the other hand how to accelerate the computation of the coupled model of LBM and an implicitly solved RANS model in 3D cases. To ensure the numerical stability and meanwhile avoid the use of empirical artificial lim- itations on turbulent quantities in 2D cases, we investigated the impacts of collision models in LBM (LBGK, MRT) and the numerical schemes for convection terms (WENO, TVD) and production terms (FDM, NEQM) in an explic- itly solved standard k-e model. The combination of MRT and TVD or MRT and NEQM can be screened out for the 2D simulation of backward-facing step flow even at Re = 107. This scheme combination, however, may still not guarantee the numerical stability in 3D cases and hence much finer grids are required, which is not suitable for the simulation of industrial-scale processes.Then we proposed a new method to accelerate the coupled model of LBM with RANS (implicitly solved). When implemented on multiple GPUs, this new method can achieve 13.5-fold accelera- tion relative to the original coupled model and 40-fold acceleration compared to the traditional CFD simulation based on Finite Volume (FV) method accelerated by multiple CPUs. This study provides the basis for the transient flow simulation of larger spatial and temporal scales in industrial applications with LBM-RANS methods.展开更多
Aluminum laminate is one kind of the rigidizable composite materials and plays an important role in construction of the inflatable space structure(ISS),which has potential application in space in the future.But the st...Aluminum laminate is one kind of the rigidizable composite materials and plays an important role in construction of the inflatable space structure(ISS),which has potential application in space in the future.But the study of the predecessors mainly focuses on the research of the mechanical behavior in the room temperature,for this reason,mechanical properties of the aluminum laminate in low-high temperature have been studied in this paper.The failure mechanism of the aluminum laminate is also analyzed in the microscopic view by JCXA-T33 electron probe.The results show uhat the temperature has significant influence on the strength and Young's modulus of the aluminum laminate.With the increase of temperature,both the strength and Young's modulus of the aluminum laminate decrease.A model between Young's modulus of the aluminum laminate and temperatures is obtained by using Arrhenius equation.The predicted values by the model agree well with the experiment values.展开更多
We consider the Schatten class weighted composition operators on the Bergman space of the unit ball. The main result is several necessary and sutfficient conditions for such kind of weighted composition operators belo...We consider the Schatten class weighted composition operators on the Bergman space of the unit ball. The main result is several necessary and sutfficient conditions for such kind of weighted composition operators belong to the Schatten-Von Neumann ideal Sp. As a corollary, we now have that Wφ,ψ is a Hilbert-Schmidt operator if and only if ∫Bn │ψ(w)│^2/(1-│φ(W)│^2)^n+1 dV(W)〈∞展开更多
Composition operators are used to study the E0(p,q) spaces, which coincide with the space Qq,0 for p = 2 and the little Bloch space B0 for p > 0 and q > 1. The compactness of these operators is also considered. ...Composition operators are used to study the E0(p,q) spaces, which coincide with the space Qq,0 for p = 2 and the little Bloch space B0 for p > 0 and q > 1. The compactness of these operators is also considered. The criteria for these operators to be compact are given in terms of the Carlesou measure.展开更多
The authors express the essential norms of composition operators between Hardy spaces of the unit disc in terms of the natural Nevanlinna counting function.
Suppose φ is an analytic map of the unit disk D into itself, X is a Banach space of analytic functions on D. Define the composition operator Cφ: Cφf = f °φ, for all f ∈ X. In this paper, the boundedness and ...Suppose φ is an analytic map of the unit disk D into itself, X is a Banach space of analytic functions on D. Define the composition operator Cφ: Cφf = f °φ, for all f ∈ X. In this paper, the boundedness and compactness of the composition operators from α-Bloch spaces into QK(p,q) and QK,0(p,q) spaces are discussed, where 0 < α < ∞.展开更多
The authors give an upper bound of the essential norms of composition opera- tors between Hardy spaces of the unit ball in terms of the counting function in the higher dimensional value distribution theory defined by ...The authors give an upper bound of the essential norms of composition opera- tors between Hardy spaces of the unit ball in terms of the counting function in the higher dimensional value distribution theory defined by Professor S. S. Chern. The sufficient condition for such operators to be bounded or compact is also given.展开更多
With the socio-economic development associated with urbanization, the urban-rural relationship has changed across the world. In China, due to the urban-rural dual structure, these changes turn out to be more complicat...With the socio-economic development associated with urbanization, the urban-rural relationship has changed across the world. In China, due to the urban-rural dual structure, these changes turn out to be more complicated. Spatial restructuring are suggested as the main strategies and spatial supporting platforms for urban-rural development. However, the theory still lacks solid methodology and support from systematic empirical studies. This study seeks an adequate scientific methodology and discusses the difference of urban-rural transformation in plains and mountainous areas. A case in Shanghang County, China, demonstrates: 1) The compound ecological niche model can be a suitable approach in urban-rural restructuring, especially in mountainous areas. 2) The urban-rural development area with highly inappropriate, slightly appropriate, moderately appropriate, and highly appropriate areas are 1273.2 km2(44.69%); 906.1 km2(31.80%); 509.4 km2(17.88%); and 160.1 km2(5.62%), respectively. 3) The "deserting villages" in mountainous areas play positive synergistic roles in urbanization, in contrast to the "hollowing villages" common in plain areas. 4) The central town-village will become the most important settlement in mountainous areas. Therefore, we suggest more attention should be paid to environmental capacity in the construction of central town-villages. This study significantly extends the understanding of "hollowing village" theory and regional planning.展开更多
Starting from a rudimentary quantum-networks model that consists of two two-level confined atoms locating respectively in spatially-separated cavities coupled by fiber,we investigate the complex entanglement character...Starting from a rudimentary quantum-networks model that consists of two two-level confined atoms locating respectively in spatially-separated cavities coupled by fiber,we investigate the complex entanglement characteristics of the composite system analytically under the maximally initial entangled state that generates two excitations simultaneously during the temporal-evolution process.Our calculation clearly shows that,through mediating the atom-cavity coupling strength and photon-photon hopping rate appropriately,the entanglement dynamics displays some distinctive temporal properties differing from those obtained in one-excitation space,characterized partially by these newly quantum phenomena termed as entanglement sudden death and recurrence.Effectively,within the framework of two excitations,we suggest the purposeful manipulations of atomic entanglement communication for quantum networks.展开更多
基金Supported by the Science and Technology Key Projects of Shanxi Province(2011A080804012)
文摘The paper presents a 3D numerical simulation of turbulent heat transfer and flow characteristics in converging-diverging tubes (CDs) and converging-diverg)ng tubes.equi.pped with twin counter-swirling twisted tapes (CDTs). The effects of Reynolds number (Re= 10000-20000), pitch length (P= 11.25, 22.5 mm), rib height (e = 0.5, 0.8, 1.1 ram), pitch ratio (8= 1 " 8, 5 " 4, 8 " 1), gap distance between twin t)visted tapes (b = 0.5, 4.5, 8.5 mm) and tape number (n = 2, 3, 4, 5, 6) on Nusselt number (Nu), Iriction tactor 0') and thermal enhancement factor (r/) are investigated under uniform heat flux conditions,using water as working fluid. In order to illustrate the heat transter and tlu^d tlow mechamsms, flow structures m ~StJs and ~SDIs are presented. The obtained results reveal that all geometric parameters have important effects on the thermal performance of CD and CDT, and both CD and CDT show better thermal performance than plain tube at the constant pumping power. It is also found that the increases in the Nusselt number and friction factor for CDT are, respectively, up to 6.3%-35.7% and 1.75-5.3 times of thecorresponding bare CD. All CDTs have good thermal perbrmance with greater than 1 which indicates that the compound heat transfer technique of CDT is commendable for the maximum enhanced heat transfer rate.
基金the National Natural Science Foundation of China(10471039)the Natural Science Foundation of Zhejiang Province(Y606197)the Natural Science Foundation of Huzhou City(2005YZ02)
文摘The article not only presents the boundedness and compactness of the weighted composition operator from α-Bloch spaces(or little α-Bloch spaces) to H^∞, but also gives some estimates for the norm of the weighted composition operator.
文摘In this paper, we define the weighted Dirichlet space D p α(Ω) on bounded symmetric domains Ω of C n. Using η-α Carleson measure,we study the boundedness and compactmess of the composition operators between the weighted Dirichlet spaces.
基金Supported in part by 973 plan and NSF of Zhejiang Province of China(Gl999075105)
文摘We consider the weighted composition operators between Hardy spaces on the unit ball, and obtain some sufficient and necessary conditions of bounded or compact weighted composition operators. We also prove that the operator from H^1 to H^1 is compact if and only if it is weakly compact. Meanwhile, we get the analogue on the Bergman spaces.
基金the Scientific Research Program of the Higher Education Institution of Xinjiang(XJEDU2005E06)
文摘In this paper, we give a necessary and sufficient condition for weighted composition operators Cu,φ to be boundedness on Bloch type spaces B^α. The theorem generalizes some previous results.
文摘In this paper, we propose a new spatial-multiplexing(SM) scheme employing an orthogonal precoder over Rayleigh-fading channels for an erasure event in single frequency networks(SFN). To optimize the precoder, the average bit error rate(BER) is evaluated and minimized through a mathematical analysis. Compared to an ordinary SM, the proposed scheme guarantees identical BER performance under non-erasure fading channels and achieves a greatly improved performance under erasure fading channels, especially for a higher erasure-ratio and SNR values. This improvement is mainly due to the increase in the diversity gain incurred by the optimized precoder over the erasure event. We also compare the performance of the proposed SM to that of the conventional constellation-rotation(CR) scheme applied to the single antenna SFN systems. The results of a computer simulation show that the performance of the new scheme is more effective than that of a conventional CR across all simulation cases.
基金Supported by National Natural Science Foundation of China (No. 10971153 and No. 10671141)
文摘The relation between composition operators on the Dirichlet spaces in the open unit disk and derivative weighted composition operators on the Bergman spaces in the open unit disk is investigated firstly,and for a combination of several derivative weighted composition operators which acts on classic Bergman space,the lower bound of its essential norm is estimated in terms of the boundary data of the symbols of d-composition operators.Some similar results about composition operators on the Dirichlet space are also presented.A necessary condition is given to determine the compactness of the combination of several derivative weighted composition operators on Bergman spaces.
基金Supported by National Natural Science Foundation of China (No.10971153)
文摘In order to investigate the boundedness or compactness of composition operator from the logarithmic Bloch-type space to the Bergman space on the unit polydisc, the classic Bergman norm is firstly changed into another equivalent norm. Then according to some common inequalities, the properties of logarithmic Bloch-type space and the absolute continuity of the general integral, the conditions which the symbol map must meet when the composition operator is bounded or compact are obtained after a series of calculations, and the boundedness and compactness are proved to be equivalent.
文摘In this paper,we give a fixed point theorem for multi-valued composite increasing operators,in partially ordered spaces,which generalizes the results of [1]-[3] and [5]- [8].
基金Supported by the National Key Research and Development Program of China(2017YFB0602500)National Natural Science Foundation of China(91634203 and91434121)Chinese Academy of Sciences(122111KYSB20150003)
文摘The coupled models of LBM (Lattice Boltzmann Method) and RANS (Reynolds-Averaged Navier-Stokes) are more practical for the transient simulation of mixing processes at large spatial and temporal scales such as crude oil mixing in large-diameter storage tanks. To keep the efficiency of parallel computation of LBM, the RANS model should also be explicitly solved; whereas to keep the numerical stability the implicit method should be better for PANS model. This article explores the numerical stability of explicit methods in 2D cases on one hand, and on the other hand how to accelerate the computation of the coupled model of LBM and an implicitly solved RANS model in 3D cases. To ensure the numerical stability and meanwhile avoid the use of empirical artificial lim- itations on turbulent quantities in 2D cases, we investigated the impacts of collision models in LBM (LBGK, MRT) and the numerical schemes for convection terms (WENO, TVD) and production terms (FDM, NEQM) in an explic- itly solved standard k-e model. The combination of MRT and TVD or MRT and NEQM can be screened out for the 2D simulation of backward-facing step flow even at Re = 107. This scheme combination, however, may still not guarantee the numerical stability in 3D cases and hence much finer grids are required, which is not suitable for the simulation of industrial-scale processes.Then we proposed a new method to accelerate the coupled model of LBM with RANS (implicitly solved). When implemented on multiple GPUs, this new method can achieve 13.5-fold accelera- tion relative to the original coupled model and 40-fold acceleration compared to the traditional CFD simulation based on Finite Volume (FV) method accelerated by multiple CPUs. This study provides the basis for the transient flow simulation of larger spatial and temporal scales in industrial applications with LBM-RANS methods.
文摘Aluminum laminate is one kind of the rigidizable composite materials and plays an important role in construction of the inflatable space structure(ISS),which has potential application in space in the future.But the study of the predecessors mainly focuses on the research of the mechanical behavior in the room temperature,for this reason,mechanical properties of the aluminum laminate in low-high temperature have been studied in this paper.The failure mechanism of the aluminum laminate is also analyzed in the microscopic view by JCXA-T33 electron probe.The results show uhat the temperature has significant influence on the strength and Young's modulus of the aluminum laminate.With the increase of temperature,both the strength and Young's modulus of the aluminum laminate decrease.A model between Young's modulus of the aluminum laminate and temperatures is obtained by using Arrhenius equation.The predicted values by the model agree well with the experiment values.
基金the National Natural Science Foundation of China(10471039)the Natural Science Foundation of the Education Commission of Jiangsu Province(03KJD140210,06KJD110175)the Natural Science Foundation of Xuzhou Institute of Technology(KY200508).
文摘We consider the Schatten class weighted composition operators on the Bergman space of the unit ball. The main result is several necessary and sutfficient conditions for such kind of weighted composition operators belong to the Schatten-Von Neumann ideal Sp. As a corollary, we now have that Wφ,ψ is a Hilbert-Schmidt operator if and only if ∫Bn │ψ(w)│^2/(1-│φ(W)│^2)^n+1 dV(W)〈∞
文摘Composition operators are used to study the E0(p,q) spaces, which coincide with the space Qq,0 for p = 2 and the little Bloch space B0 for p > 0 and q > 1. The compactness of these operators is also considered. The criteria for these operators to be compact are given in terms of the Carlesou measure.
基金Project supported by the National Natural Science Foundation of China (No. 10771201)the Anhui Provincial Natural Science Foundation of China (No. 090416233)
文摘The authors express the essential norms of composition operators between Hardy spaces of the unit disc in terms of the natural Nevanlinna counting function.
基金the National Natural Science Foundation of China (No.10471039)the Grant of Higher Schools’ Natural Science Basic Research of Jiangsu Province of China (Nos.06KJD110175 07KJB110115)
文摘Suppose φ is an analytic map of the unit disk D into itself, X is a Banach space of analytic functions on D. Define the composition operator Cφ: Cφf = f °φ, for all f ∈ X. In this paper, the boundedness and compactness of the composition operators from α-Bloch spaces into QK(p,q) and QK,0(p,q) spaces are discussed, where 0 < α < ∞.
基金National Natural Science Foundation of China(Nos.11171255,11101279)the Natural Science Foundation of Shanghai(No.13ZR1444100)
文摘The authors give an upper bound of the essential norms of composition opera- tors between Hardy spaces of the unit ball in terms of the counting function in the higher dimensional value distribution theory defined by Professor S. S. Chern. The sufficient condition for such operators to be bounded or compact is also given.
基金National Natural Science Foundation of China,No.41301621Institute of Urban Environment,Chinese Academy of Sciences and National Scholarship Committee
文摘With the socio-economic development associated with urbanization, the urban-rural relationship has changed across the world. In China, due to the urban-rural dual structure, these changes turn out to be more complicated. Spatial restructuring are suggested as the main strategies and spatial supporting platforms for urban-rural development. However, the theory still lacks solid methodology and support from systematic empirical studies. This study seeks an adequate scientific methodology and discusses the difference of urban-rural transformation in plains and mountainous areas. A case in Shanghang County, China, demonstrates: 1) The compound ecological niche model can be a suitable approach in urban-rural restructuring, especially in mountainous areas. 2) The urban-rural development area with highly inappropriate, slightly appropriate, moderately appropriate, and highly appropriate areas are 1273.2 km2(44.69%); 906.1 km2(31.80%); 509.4 km2(17.88%); and 160.1 km2(5.62%), respectively. 3) The "deserting villages" in mountainous areas play positive synergistic roles in urbanization, in contrast to the "hollowing villages" common in plain areas. 4) The central town-village will become the most important settlement in mountainous areas. Therefore, we suggest more attention should be paid to environmental capacity in the construction of central town-villages. This study significantly extends the understanding of "hollowing village" theory and regional planning.
基金supported by the National Basic Research Program of China (Grant No. 2012CB921900)the National Natural Science Foundation of China (Grant No. 10574166)the Guangdong Natural Science Foundation (Grant No. 8151027501000062)
文摘Starting from a rudimentary quantum-networks model that consists of two two-level confined atoms locating respectively in spatially-separated cavities coupled by fiber,we investigate the complex entanglement characteristics of the composite system analytically under the maximally initial entangled state that generates two excitations simultaneously during the temporal-evolution process.Our calculation clearly shows that,through mediating the atom-cavity coupling strength and photon-photon hopping rate appropriately,the entanglement dynamics displays some distinctive temporal properties differing from those obtained in one-excitation space,characterized partially by these newly quantum phenomena termed as entanglement sudden death and recurrence.Effectively,within the framework of two excitations,we suggest the purposeful manipulations of atomic entanglement communication for quantum networks.