Concepts and connotations of circular economy and eco-agricultural tourism were introduced,and feasibility of applying circular economy in eco-agricultural tourism was further studied.It was stressed that development ...Concepts and connotations of circular economy and eco-agricultural tourism were introduced,and feasibility of applying circular economy in eco-agricultural tourism was further studied.It was stressed that development of eco-agricultural tourism complies with the theme of resource recycling,moreover,both eco-agricultural tourist products and circular economy value environment protection,and target at the win-win of ecological and economic benefits.From the perspective of circular economy,the construction of eco-agricultural tourist product mode was studied,construction of eco-agricultural tourist areas,catering and accommodation areas and traffic construction of eco-agricultural scenic areas were discussed.The study stressed that connotations of circular economy can be used to restrain eco-agricultural tourism,and realize recycling and sustainable development of resources.展开更多
In this study, three rapid repair techniques are proposed to retrofit circular bridge piers that are severely damaged by the flexural failure mode in major earthquakes. The quasi-static tests on three 1：2.5 scaled ci...In this study, three rapid repair techniques are proposed to retrofit circular bridge piers that are severely damaged by the flexural failure mode in major earthquakes. The quasi-static tests on three 1：2.5 scaled circular pier specimens are conducted to evaluate the efficiency of the proposed repair techniques. For the purpose of rapid repair, the repair procedure for all the specimens is conducted within four days, and the behavior of the repaired specimens is evaluated and compared with the original ones. A finite element model is developed to predict the cyclic behavior of the repaired specimens and the numerical results are compared with the test data. It is found that all the repaired specimens exhibit similar or larger lateral strength and deformation capacity than the original ones. The initial lateral stiffness of all the repaired specimens is lower than that of the original ones, while they show a higher lateral stiffness at the later stage of the test. No noticeable difference is observed for the energy dissipation capacity between the original and repaired pier specimens. It is suggested that the repair technique using the early-strength concrete jacket confined by carbon fiber reinforced polymer （CFRP） sheets can be an optimal method for the rapid repair of severely earthquake-damaged circular bridge piers with flexural failure mode.展开更多
Mode matching is used for the analysis of monopole antenna on circular disc, which is achieved by developing a novel model consisting of two artificial ground planes above and bellow the monopole antenna. Using this m...Mode matching is used for the analysis of monopole antenna on circular disc, which is achieved by developing a novel model consisting of two artificial ground planes above and bellow the monopole antenna. Using this model, the input impedance is computed and compared with measured data reported in literatures, and excellent agreement is observed.展开更多
A theoretical model of a circular flexure-mode piezoelectric bimorph ac- tuator is established. The circular bimorph structure, consisting of two flexible layers of piezoelectric material and a layer of metallic mater...A theoretical model of a circular flexure-mode piezoelectric bimorph ac- tuator is established. The circular bimorph structure, consisting of two flexible layers of piezoelectric material and a layer of metallic material in the middle, is powered to the flexural deformation. The analytical solutions including the statics solution and the dynamics solution are derived from the 3D equations of the linear theory of piezoelectric- ity. Numerical results are included to show the circular bimorph piezoelectric actuator （CBPA） performance, depending on the physical parameters.展开更多
Circular economy adapts to large-scale production, has higher requirement on technical level, and possesses positive externality. There- fore, circular economy requires a lot of financial support. Facing investment an...Circular economy adapts to large-scale production, has higher requirement on technical level, and possesses positive externality. There- fore, circular economy requires a lot of financial support. Facing investment and financing problems of circular economy by enterprise, the govern- ment should strengthen the regulatory role, increase investment support on circular economy, strengthen the bank＇s green credit business, reduce barriers to business loans, diversify financing channels for enterprises, guide social investment＇s flow direction, and promote circular economy form- ing larger scale, thereby providing policy support for building a resource-saving and environment-friendly society.展开更多
This paper gives the simple and logical approach of LP modes in circular and elliptical waveguides. Earlier the basic approach of modes in circular and elliptical fibers was studied by the authors. In this paper, the ...This paper gives the simple and logical approach of LP modes in circular and elliptical waveguides. Earlier the basic approach of modes in circular and elliptical fibers was studied by the authors. In this paper, the role of radial antinode in circular and elliptical waveguides is given clearly. Splitting of modes in circular and elliptical fiber has been discussed.展开更多
Fluid flow past twin circular cylinders in a tandem arrangement placed near a plane wall was investigated by means of numerical simulations. The two-dimensional Navier-Stokes equations were solved with a three-step fi...Fluid flow past twin circular cylinders in a tandem arrangement placed near a plane wall was investigated by means of numerical simulations. The two-dimensional Navier-Stokes equations were solved with a three-step finite element method at a relatively low Reynolds number of Re -- 200 for various dimensionless ratios of 0.25 ≤ G/D ≤2.0 and 1.0 ≤ L/D ≤ 4.0, where D is the cylinder diameter, L is the center-to-center distance between the two cylinders, and G is the gap between the lowest surface of the twin cylinders and the plane wall. The influences of G/D and L/D on the hydrodynamic force coefficients, Strouhal numbers, and vortex shedding modes were examined. Three different vortex shedding modes of the near wake were identified according to the numerical results. It was found that the hydrodynamic force coefficients and vortex shedding modes are quite different with respect to various combinations of G/D and L/D. For very small values of G/D, the vortex shedding is completely suppressed, resulting in the root mean square （RMS） values of drag and lift coefficients of both cylinders and the Strouhal number for the downstream cylinder being almost zero. The mean drag coefficient of the upstream cylinder is larger than that of the downstream cylinder for the same combination of G/D and L/D. It is also observed that change in the vortex shedding modes leads to a significant increase in the RMS values of drag and lift coefficients.展开更多
This paper firstly elaborated current situation of agricultural resources and ecological environment protection of China,and pointed out that circular agriculture is an inevitable choice for sustainable development of...This paper firstly elaborated current situation of agricultural resources and ecological environment protection of China,and pointed out that circular agriculture is an inevitable choice for sustainable development of agriculture and effective approach for low-carbon economic development. Then,it analyzed mode and benefit of typical circular agriculture,such as ecological orchard in southeast hills,sightseeing ecological agricultural garden,and crop straw use. Finally,it came up with countermeasures for further developing circular agriculture,including integrating building system and establishing suitable mode,formulating production standard and ensuring food safety,strengthening technological innovation,and supporting sustainable development.展开更多
Plate shaped sandstones containing two fabricated circular holes that were filled with gypsum and high-strength concrete respectively were prepared for studying the effects of ligament length L ligament incline angle ...Plate shaped sandstones containing two fabricated circular holes that were filled with gypsum and high-strength concrete respectively were prepared for studying the effects of ligament length L ligament incline angle α, as well as filling modes on their strength properties and failure modes. The results show that the initial cracks can be categorized as wing crack, axial tensile crack and curved tensile crack. The failure modes of ligaments can be categorized as mode of single inclined crack, mode of single axial crack and mode of two parallel cracks. The final failure modes of all specimens can be categorized as the tension-shear mixed failure and shear failure. The strength of inclusions shows little influence on the final failure modes of specimens, while the failure modes vary with L and α. When α is a fixed value, the peak strength σc and elastic modulus Ec of tested specimens increase firstly with increasing L and reaches to the maximum value at L of 16 mm, then declines. When L is a fixed value, σc declines firstly and then turns to increase as α increases to 75° from 45°, while Ec increases linearly. The axial stress σp performs the similar variation trends with those of σc versus increasing L and α when ligaments fail.展开更多
The uniaxial compression experiments on the sandstone samples containing double fissures and a single circular hole were carried out by using electro-hydraulic servo universal testing machine to investigate the effect...The uniaxial compression experiments on the sandstone samples containing double fissures and a single circular hole were carried out by using electro-hydraulic servo universal testing machine to investigate the effect of rock bridge angle β and fissure angle α on mechanical properties and evolution characteristics of cracks.The results show that the peak strength,peak strain and elastic modulus of defected specimens decrease comparing with those for intact sample,and show a decreased trend firstly and then increase with β changing from 0° to 90°.The peak strength and elastic modulus achieve the minimum value as the rock bridge angle is 60°,while the peak strain reaches the minimum value with the rock bridge angle of 45°.The crack initiation of tested rock samples occurs firstly in stress concentration areas at tips of prefabricated fissures under uniaxial compression,and then propagates constantly and coalescences with the prefabricated hole.Some secondary cracks initiate and propagate as well until buckling failure happens.The rock bridge angle has a great influence on crack initiation,coalescence,final failure mode,crack initiation stress and transfixion stress.The peak strength varies significantly,while the elastic modulus and peak strain change slightly,and the failure modes are also different due to the influence of fissure angle.展开更多
The effects of residual stress on the hydro-elastic vibration of circular diaphragm are theoretically investigated by using the added mass approach. The Kirchhoff theory of plates is used to model the elastic thin cir...The effects of residual stress on the hydro-elastic vibration of circular diaphragm are theoretically investigated by using the added mass approach. The Kirchhoff theory of plates is used to model the elastic thin circular diaphragm on an aperture of an infinite rigid wall and in contact with a fluid on one side. The fluid is assumed to be incompressible and inviscid and the velocity potential is used to describe its irrotational motion. A non-dimensional tension parameter is defined, and the effects of the tension parameter on the frequency parameters and mode shapes of the diaphragm in the air are presented. The Hankel transform is applied to solve the fluid-diaphragm coupled system;boundary conditions are expressed by integral equations. Finally, the effects of residual stress on the non-dimensional added virtual mass incremental (NAVMI) factors of the diaphragm contact with a fluid on one side are investigated. It is found that the effects of the residual stress cannot be neglected when the edges of the circular diaphragm are clamped. The effects of residual stress for NAVMI factors can be increases 11% when the non-dimensional tension parameter is 1000.展开更多
The spatial evolution of vortices and transition to three-dimensionality in the wake of two circular cylinders in tandem arrangement have been numerically studied. An improved virtual body method developed from the vi...The spatial evolution of vortices and transition to three-dimensionality in the wake of two circular cylinders in tandem arrangement have been numerically studied. An improved virtual body method developed from the virtual boundary method is used here. A Reynolds number range between 220 and 270 has been considered, and the spacing between two cylinders is selected as L/D=3 and L/D=3.5. When L/D=3, the secondary vortices of Mode-A are seen to appear at Re=240 and persist over the range of the Reynolds number of 240～270. When L/D=3.5, the similar critical Reynolds number has been found at Re=250. No obvious discontinuity has been found in the Strouhal-Reynolds number relationship, and this is different from three-dimensional flow around a single cylinder at the critical Reynolds number. The spanwise wavelength is about four times the diameter of the cylinder, and it is the characteristic wavelength for Mode-A instability. This paper can give some foremost insight into the three-dimensional instability of flow by complicated geometrical configuration.展开更多
基金Supported by Scientific Research Foundation of Shandong Jiaotong University(R200907)~~
文摘Concepts and connotations of circular economy and eco-agricultural tourism were introduced,and feasibility of applying circular economy in eco-agricultural tourism was further studied.It was stressed that development of eco-agricultural tourism complies with the theme of resource recycling,moreover,both eco-agricultural tourist products and circular economy value environment protection,and target at the win-win of ecological and economic benefits.From the perspective of circular economy,the construction of eco-agricultural tourist product mode was studied,construction of eco-agricultural tourist areas,catering and accommodation areas and traffic construction of eco-agricultural scenic areas were discussed.The study stressed that connotations of circular economy can be used to restrain eco-agricultural tourism,and realize recycling and sustainable development of resources.
基金National Natural Science Foundation of China under Grant No.51678150Science for Earthquake Resilience under Grant No.XH17064Australian Research Council Discovery Early Career Researcher Award(DECRA)
文摘In this study, three rapid repair techniques are proposed to retrofit circular bridge piers that are severely damaged by the flexural failure mode in major earthquakes. The quasi-static tests on three 1：2.5 scaled circular pier specimens are conducted to evaluate the efficiency of the proposed repair techniques. For the purpose of rapid repair, the repair procedure for all the specimens is conducted within four days, and the behavior of the repaired specimens is evaluated and compared with the original ones. A finite element model is developed to predict the cyclic behavior of the repaired specimens and the numerical results are compared with the test data. It is found that all the repaired specimens exhibit similar or larger lateral strength and deformation capacity than the original ones. The initial lateral stiffness of all the repaired specimens is lower than that of the original ones, while they show a higher lateral stiffness at the later stage of the test. No noticeable difference is observed for the energy dissipation capacity between the original and repaired pier specimens. It is suggested that the repair technique using the early-strength concrete jacket confined by carbon fiber reinforced polymer （CFRP） sheets can be an optimal method for the rapid repair of severely earthquake-damaged circular bridge piers with flexural failure mode.
文摘Mode matching is used for the analysis of monopole antenna on circular disc, which is achieved by developing a novel model consisting of two artificial ground planes above and bellow the monopole antenna. Using this model, the input impedance is computed and compared with measured data reported in literatures, and excellent agreement is observed.
基金Project supported by the National Natural Science Foundation of China(Nos.11403109,11190014,10921063,and 11373073)the Natural Science Foundation of Jiangsu Province(No.BK20141042)
文摘A theoretical model of a circular flexure-mode piezoelectric bimorph ac- tuator is established. The circular bimorph structure, consisting of two flexible layers of piezoelectric material and a layer of metallic material in the middle, is powered to the flexural deformation. The analytical solutions including the statics solution and the dynamics solution are derived from the 3D equations of the linear theory of piezoelectric- ity. Numerical results are included to show the circular bimorph piezoelectric actuator （CBPA） performance, depending on the physical parameters.
基金Supported by Research Planning Fund of Humanities and Social Sciences,Ministry of Education,China(09YJAZH005)Soft Science Research Item of Beijing Science and Technology Plan Project,China(Z131109001613006)+1 种基金Humanities and Social Sciences Fund of Beijing University of Technology,China(X5104001201301)"Research,Environment and Circular Economy"of Beijing Key Discipline,China(033000541214001)
文摘Circular economy adapts to large-scale production, has higher requirement on technical level, and possesses positive externality. There- fore, circular economy requires a lot of financial support. Facing investment and financing problems of circular economy by enterprise, the govern- ment should strengthen the regulatory role, increase investment support on circular economy, strengthen the bank＇s green credit business, reduce barriers to business loans, diversify financing channels for enterprises, guide social investment＇s flow direction, and promote circular economy form- ing larger scale, thereby providing policy support for building a resource-saving and environment-friendly society.
文摘This paper gives the simple and logical approach of LP modes in circular and elliptical waveguides. Earlier the basic approach of modes in circular and elliptical fibers was studied by the authors. In this paper, the role of radial antinode in circular and elliptical waveguides is given clearly. Splitting of modes in circular and elliptical fiber has been discussed.
基金supported by the National Natural Science Foundation of China(Grants No.51409035,51279029,and 51490673)the Open Fund from the Key Laboratory of Harbor,Waterway and Sedimentation Engineering of Ministry of Communications,Nanjing Hydraulic Research Institute
文摘Fluid flow past twin circular cylinders in a tandem arrangement placed near a plane wall was investigated by means of numerical simulations. The two-dimensional Navier-Stokes equations were solved with a three-step finite element method at a relatively low Reynolds number of Re -- 200 for various dimensionless ratios of 0.25 ≤ G/D ≤2.0 and 1.0 ≤ L/D ≤ 4.0, where D is the cylinder diameter, L is the center-to-center distance between the two cylinders, and G is the gap between the lowest surface of the twin cylinders and the plane wall. The influences of G/D and L/D on the hydrodynamic force coefficients, Strouhal numbers, and vortex shedding modes were examined. Three different vortex shedding modes of the near wake were identified according to the numerical results. It was found that the hydrodynamic force coefficients and vortex shedding modes are quite different with respect to various combinations of G/D and L/D. For very small values of G/D, the vortex shedding is completely suppressed, resulting in the root mean square （RMS） values of drag and lift coefficients of both cylinders and the Strouhal number for the downstream cylinder being almost zero. The mean drag coefficient of the upstream cylinder is larger than that of the downstream cylinder for the same combination of G/D and L/D. It is also observed that change in the vortex shedding modes leads to a significant increase in the RMS values of drag and lift coefficients.
基金Supported by the National Science and Technology Project in the Twelfth Five-year Plan Period(2012BAD14B15)
文摘This paper firstly elaborated current situation of agricultural resources and ecological environment protection of China,and pointed out that circular agriculture is an inevitable choice for sustainable development of agriculture and effective approach for low-carbon economic development. Then,it analyzed mode and benefit of typical circular agriculture,such as ecological orchard in southeast hills,sightseeing ecological agricultural garden,and crop straw use. Finally,it came up with countermeasures for further developing circular agriculture,including integrating building system and establishing suitable mode,formulating production standard and ensuring food safety,strengthening technological innovation,and supporting sustainable development.
基金Project(2017YFC0603001)supported by the High-tech Research and Development Program of ChinaProject(51374198)supported by the National Natural Science Foundation of China
文摘Plate shaped sandstones containing two fabricated circular holes that were filled with gypsum and high-strength concrete respectively were prepared for studying the effects of ligament length L ligament incline angle α, as well as filling modes on their strength properties and failure modes. The results show that the initial cracks can be categorized as wing crack, axial tensile crack and curved tensile crack. The failure modes of ligaments can be categorized as mode of single inclined crack, mode of single axial crack and mode of two parallel cracks. The final failure modes of all specimens can be categorized as the tension-shear mixed failure and shear failure. The strength of inclusions shows little influence on the final failure modes of specimens, while the failure modes vary with L and α. When α is a fixed value, the peak strength σc and elastic modulus Ec of tested specimens increase firstly with increasing L and reaches to the maximum value at L of 16 mm, then declines. When L is a fixed value, σc declines firstly and then turns to increase as α increases to 75° from 45°, while Ec increases linearly. The axial stress σp performs the similar variation trends with those of σc versus increasing L and α when ligaments fail.
基金Financial support for this work, provided by the National Key Basic Research Development Plan Project of China (No.2013CB036003)the National Natural Science Foundation of China (Nos.51134001,51374198)the Young Scientists Fund of the National Science Foundation of China (No.51504247)
文摘The uniaxial compression experiments on the sandstone samples containing double fissures and a single circular hole were carried out by using electro-hydraulic servo universal testing machine to investigate the effect of rock bridge angle β and fissure angle α on mechanical properties and evolution characteristics of cracks.The results show that the peak strength,peak strain and elastic modulus of defected specimens decrease comparing with those for intact sample,and show a decreased trend firstly and then increase with β changing from 0° to 90°.The peak strength and elastic modulus achieve the minimum value as the rock bridge angle is 60°,while the peak strain reaches the minimum value with the rock bridge angle of 45°.The crack initiation of tested rock samples occurs firstly in stress concentration areas at tips of prefabricated fissures under uniaxial compression,and then propagates constantly and coalescences with the prefabricated hole.Some secondary cracks initiate and propagate as well until buckling failure happens.The rock bridge angle has a great influence on crack initiation,coalescence,final failure mode,crack initiation stress and transfixion stress.The peak strength varies significantly,while the elastic modulus and peak strain change slightly,and the failure modes are also different due to the influence of fissure angle.
文摘The effects of residual stress on the hydro-elastic vibration of circular diaphragm are theoretically investigated by using the added mass approach. The Kirchhoff theory of plates is used to model the elastic thin circular diaphragm on an aperture of an infinite rigid wall and in contact with a fluid on one side. The fluid is assumed to be incompressible and inviscid and the velocity potential is used to describe its irrotational motion. A non-dimensional tension parameter is defined, and the effects of the tension parameter on the frequency parameters and mode shapes of the diaphragm in the air are presented. The Hankel transform is applied to solve the fluid-diaphragm coupled system;boundary conditions are expressed by integral equations. Finally, the effects of residual stress on the non-dimensional added virtual mass incremental (NAVMI) factors of the diaphragm contact with a fluid on one side are investigated. It is found that the effects of the residual stress cannot be neglected when the edges of the circular diaphragm are clamped. The effects of residual stress for NAVMI factors can be increases 11% when the non-dimensional tension parameter is 1000.
基金This work was financially supported by the National Natural Science Foundation of China (Grant No. 10272094)
文摘The spatial evolution of vortices and transition to three-dimensionality in the wake of two circular cylinders in tandem arrangement have been numerically studied. An improved virtual body method developed from the virtual boundary method is used here. A Reynolds number range between 220 and 270 has been considered, and the spacing between two cylinders is selected as L/D=3 and L/D=3.5. When L/D=3, the secondary vortices of Mode-A are seen to appear at Re=240 and persist over the range of the Reynolds number of 240～270. When L/D=3.5, the similar critical Reynolds number has been found at Re=250. No obvious discontinuity has been found in the Strouhal-Reynolds number relationship, and this is different from three-dimensional flow around a single cylinder at the critical Reynolds number. The spanwise wavelength is about four times the diameter of the cylinder, and it is the characteristic wavelength for Mode-A instability. This paper can give some foremost insight into the three-dimensional instability of flow by complicated geometrical configuration.
