A simple method was developed to prepare the uniform hematite hollow submicro-spheres with controllable structure and different diameter based on monodisperse poly（styrene-co-acrylic acid） [P（St-co-AA）] particles....A simple method was developed to prepare the uniform hematite hollow submicro-spheres with controllable structure and different diameter based on monodisperse poly（styrene-co-acrylic acid） [P（St-co-AA）] particles. The structure and formation mechanism of the hollow spheres were investigated in detail. The control mechanism of shell thickness was also discussed. The results indicated that the shell thickness and coarseness of the synthesized core-shell hematite hollow spheres could be tuned simply by the surface carboxyl content of the P（St-co-AA） particles. This method provided a new approach for the structure control in the preparation of hollow spheres. A Brunauer-Emmett-Teller （BET） test shows that the prepared hollow spheres have large surface areas which were decreased along with the increase of the diameter. The magnetic properties of the as-obtained hematite hollow spheres were investigated. The result showed that the coercivity and saturated magnetization were increased along with the increase of the shell thickness, and the remanent magnetization was increased along with the decrease of the diameter.展开更多
The key to reduce shell breakout in the continuous casting process is to control shell thickness in the mold. A numerical simulation on the turbulent flow and heat transfer coupled with solidification in the slab mold...The key to reduce shell breakout in the continuous casting process is to control shell thickness in the mold. A numerical simulation on the turbulent flow and heat transfer coupled with solidification in the slab mold using the volume of fluid （VOF） model and the enthalpy-porosity scheme was conducted and the emphasis was put upon the flow effect on the shell thickness profiles in longitudinal and transverse directions. The results show that the jet acts a stronger impingement on the shell of narrow face, which causes a zero-increase of shell thickness in a certain range near the impingement point. The thinnest shell on the slab cross-section locates primarily in the center of the narrow face, and secondly near the comer of the wide face. Nozzle optimization can obviously increase the shell thickness and make it more uniform.展开更多
Using the modified method of multiple scales, the nonlinear stability of a truncated shallow spherical shell of variable thickness with a nondeformable rigid body at the center under compound loads is investigated. Wh...Using the modified method of multiple scales, the nonlinear stability of a truncated shallow spherical shell of variable thickness with a nondeformable rigid body at the center under compound loads is investigated. When the geometrical parameter k is larger, the uniformly valid asymptotic solutions of this problem are obtained and the remainder terms are estimated.展开更多
The theory of nonlinear stability for a truncated shallow conical shell with variable thickness under the action of uniform pressure was presented. The fundamental equations and boundary conditions were derived by mea...The theory of nonlinear stability for a truncated shallow conical shell with variable thickness under the action of uniform pressure was presented. The fundamental equations and boundary conditions were derived by means of calculus of variations. An analytic solution for the critical buckling pressure of the shell with a hyperbolically varying thickness is obtained by use of modified iteration method. The results of numerical calculations are presented in diagrams, which show the influence of geometrical and physical parameters on the buckling behavior.展开更多
This paper is concerned with the nonlillear bending, stability and optimal design of revolution shallowshells with variable thickness. The problems are investigated by means of a modified iterative method proposedearl...This paper is concerned with the nonlillear bending, stability and optimal design of revolution shallowshells with variable thickness. The problems are investigated by means of a modified iterative method proposedearlier by the author. Solutiolls for nonlinear bedding and stability problems of revolution shallow shells withvariable thickness, such as spherical and conical shells, are presented. Deflections and critical loads for stability arecalculated and the numerical results are plotted and given in tabular forms. It is showil that the equation determiningthe maximum deflection and the load coincides with the cusp catastrophe manifold. The optimal design of plates andshells, in Which the volullle is minimized or the critical load of shells is maximized, is investigated. When the volumeoftlle shell and the arch height of the shell are given, the variable thickness parameter can be solved. In addition, thispaper also gives tile constraint optimization of nonlinear bedding of circular plates.展开更多
In this paper, to begin with. the nonlinear differential equations of a truncaled shallow spherical shell with variable thickness under uniformal distributed load are linearized by step-by-step loading method. The lin...In this paper, to begin with. the nonlinear differential equations of a truncaled shallow spherical shell with variable thickness under uniformal distributed load are linearized by step-by-step loading method. The linear differential equations can be solved by spline collocanon method. Critical loads have been obtained accordingly.展开更多
Stability analyses of perfect and imperfect cylindrical shells under axial compression and torsion were presented. Finite element method for the stability analysis of perfect cylindrical shells was put forward through...Stability analyses of perfect and imperfect cylindrical shells under axial compression and torsion were presented. Finite element method for the stability analysis of perfect cylindrical shells was put forward through comparing critical loads and the first buckling modes with those obtained through theoretical analysis. Two typical initial defects, non-circularity and uneven thickness distribution, were studied. Critical loads decline with the increase of non-circularity, which exist in imperfect cylindrical shells under both axial compression and torsion. Non-circularity defect has no effect on the first buckling mode when cylindrical shell is under torsion. Unfortunately, it has a completely different buckling mode when cylindrical shell is under axial compression. Critical loads decline with the increase of thickness defect amplitude, which exist in imperfect cylindrical shells under both axial compression and torsion, too. A greater wave number is conducive to the stability of cylindrical shells. The first buckling mode of imperfect cylindrical shells under torsion maintains its original shape, but it changes with wave number when the cylindrical shell is under axial compression.展开更多
A coupled mathematical model was established to simulate the whole solidification process of round billet continuous casting for wheel steel using piecewise linear functions of heat flux density in the mold, the secon...A coupled mathematical model was established to simulate the whole solidification process of round billet continuous casting for wheel steel using piecewise linear functions of heat flux density in the mold, the secondary cooling zone and the with- drawing-straightening zone. The calculated results were consistent with the measured data showing that the model accords with the practice. The surface temperature and the solidified shell thickness of round billets are more strongly influenced by casting speed than by casting temperature. The holding zones have effect on surface temperature, which is more obvious for the 450 mm round billet. The relation between casting temperature/speed and solidification end is expressed as a linear function. The solidification end is located after straightening machine.展开更多
The buoyancy of Artemia resting eggs is a feature with both biological and economic importance.Since the buoyancy of resting eggs is dependent on the specific weight of the eggs or salinity of ambient water,we suppose...The buoyancy of Artemia resting eggs is a feature with both biological and economic importance.Since the buoyancy of resting eggs is dependent on the specific weight of the eggs or salinity of ambient water,we suppose that habitat salinity may exert a selection pressure on resting egg buoyancy,and thereby lower habitat salinity may result in better floating capacity of resting eggs and vice versa.In this study,we compared the floating capacity of resting eggs from 25 Artemia populations.The results showed that the floating capacity of resting eggs varied greatly among different populations.The minimum salinity to float some eggs varied from 0 to 180.The salinity at which all resting eggs floated varied from 80 to 320.The FS_(50)(salinity with 50%eggs floating)of Zhundong and Yuncheng population was not detectable(over 50%eggs floating in distilled water),that of Kyêbxang Co population was 4.3,while the maximum value found in Dabancheng population was 234.5.In terms of the‘apparent specific weight’of resting eggs,18 populations exhibited a single-peak distribution pattern,while the other 7 populations showed a multiple-peak or non-peak distribution.Negative correlations were found between FS50 and chorion thickness,and between FS_(50) and the volume percentage of the chorion in eggs,supporting a previous standpoint that shell thickness was a determinative factor for the floating capacity of resting eggs.A positive correlation was determined between FS50 and habitat salinity.The hypothesis that habitat salinity may cause a directional selection on the buoyancy of resting eggs seems to be true.展开更多
In cross sections by microscopic studies have examined the features of the shell thickness grains, cells, aleuronic layer and endosperm in the species T. dicoccum Schuebl., sorts Mironovskaya-808 and their interspecif...In cross sections by microscopic studies have examined the features of the shell thickness grains, cells, aleuronic layer and endosperm in the species T. dicoccum Schuebl., sorts Mironovskaya-808 and their interspecific hybrids F9 （alloplasmatic lines）. The result of studies showed the specific and varietal differences, and differences in hybrid plants on linear parameters size grains, the degree of specificity of the shells grains of wheat and identified species and varietal differences as well as differences among hybrids in the linear dimensions of the cells of the aleuronic layer. It is shown that among the studied forms of wheat allocated species T. dicoccum Shuebl. and the lines D-N-05, D-F-05 and D-40-05-KhNA with relatively large grains, a well-developed endosperm, most of thin shells and large grain aleurone layer cells. They are of most interest for further breeding research in terms of nutritional value.展开更多
基金Funded by the New Century Excellent Talent Plan from Ministry of Education,China (No.NCET-05-0660)Fok YingTung Education Foundation (No. 101049)
文摘A simple method was developed to prepare the uniform hematite hollow submicro-spheres with controllable structure and different diameter based on monodisperse poly（styrene-co-acrylic acid） [P（St-co-AA）] particles. The structure and formation mechanism of the hollow spheres were investigated in detail. The control mechanism of shell thickness was also discussed. The results indicated that the shell thickness and coarseness of the synthesized core-shell hematite hollow spheres could be tuned simply by the surface carboxyl content of the P（St-co-AA） particles. This method provided a new approach for the structure control in the preparation of hollow spheres. A Brunauer-Emmett-Teller （BET） test shows that the prepared hollow spheres have large surface areas which were decreased along with the increase of the diameter. The magnetic properties of the as-obtained hematite hollow spheres were investigated. The result showed that the coercivity and saturated magnetization were increased along with the increase of the shell thickness, and the remanent magnetization was increased along with the decrease of the diameter.
基金supported by the National Natural Science Foundation of China (No.60672145)
文摘The key to reduce shell breakout in the continuous casting process is to control shell thickness in the mold. A numerical simulation on the turbulent flow and heat transfer coupled with solidification in the slab mold using the volume of fluid （VOF） model and the enthalpy-porosity scheme was conducted and the emphasis was put upon the flow effect on the shell thickness profiles in longitudinal and transverse directions. The results show that the jet acts a stronger impingement on the shell of narrow face, which causes a zero-increase of shell thickness in a certain range near the impingement point. The thinnest shell on the slab cross-section locates primarily in the center of the narrow face, and secondly near the comer of the wide face. Nozzle optimization can obviously increase the shell thickness and make it more uniform.
文摘Using the modified method of multiple scales, the nonlinear stability of a truncated shallow spherical shell of variable thickness with a nondeformable rigid body at the center under compound loads is investigated. When the geometrical parameter k is larger, the uniformly valid asymptotic solutions of this problem are obtained and the remainder terms are estimated.
文摘The theory of nonlinear stability for a truncated shallow conical shell with variable thickness under the action of uniform pressure was presented. The fundamental equations and boundary conditions were derived by means of calculus of variations. An analytic solution for the critical buckling pressure of the shell with a hyperbolically varying thickness is obtained by use of modified iteration method. The results of numerical calculations are presented in diagrams, which show the influence of geometrical and physical parameters on the buckling behavior.
文摘This paper is concerned with the nonlillear bending, stability and optimal design of revolution shallowshells with variable thickness. The problems are investigated by means of a modified iterative method proposedearlier by the author. Solutiolls for nonlinear bedding and stability problems of revolution shallow shells withvariable thickness, such as spherical and conical shells, are presented. Deflections and critical loads for stability arecalculated and the numerical results are plotted and given in tabular forms. It is showil that the equation determiningthe maximum deflection and the load coincides with the cusp catastrophe manifold. The optimal design of plates andshells, in Which the volullle is minimized or the critical load of shells is maximized, is investigated. When the volumeoftlle shell and the arch height of the shell are given, the variable thickness parameter can be solved. In addition, thispaper also gives tile constraint optimization of nonlinear bedding of circular plates.
文摘In this paper, to begin with. the nonlinear differential equations of a truncaled shallow spherical shell with variable thickness under uniformal distributed load are linearized by step-by-step loading method. The linear differential equations can be solved by spline collocanon method. Critical loads have been obtained accordingly.
基金Project(11102163)supported by the National Natural Science Foundation of ChinaProjects(JC20110218,JC20110260)supported by Foundation for Fundamental Research of Northwestern Polytechnical University,China
文摘Stability analyses of perfect and imperfect cylindrical shells under axial compression and torsion were presented. Finite element method for the stability analysis of perfect cylindrical shells was put forward through comparing critical loads and the first buckling modes with those obtained through theoretical analysis. Two typical initial defects, non-circularity and uneven thickness distribution, were studied. Critical loads decline with the increase of non-circularity, which exist in imperfect cylindrical shells under both axial compression and torsion. Non-circularity defect has no effect on the first buckling mode when cylindrical shell is under torsion. Unfortunately, it has a completely different buckling mode when cylindrical shell is under axial compression. Critical loads decline with the increase of thickness defect amplitude, which exist in imperfect cylindrical shells under both axial compression and torsion, too. A greater wave number is conducive to the stability of cylindrical shells. The first buckling mode of imperfect cylindrical shells under torsion maintains its original shape, but it changes with wave number when the cylindrical shell is under axial compression.
文摘A coupled mathematical model was established to simulate the whole solidification process of round billet continuous casting for wheel steel using piecewise linear functions of heat flux density in the mold, the secondary cooling zone and the with- drawing-straightening zone. The calculated results were consistent with the measured data showing that the model accords with the practice. The surface temperature and the solidified shell thickness of round billets are more strongly influenced by casting speed than by casting temperature. The holding zones have effect on surface temperature, which is more obvious for the 450 mm round billet. The relation between casting temperature/speed and solidification end is expressed as a linear function. The solidification end is located after straightening machine.
基金supported by the Science and Technology Project of Tibet Autonomous Region(Nos.XZ201703-GB-04,XZ202102YD0022C)the Science and Technology Project of Zhejiang Province(No.2020C26008).
文摘The buoyancy of Artemia resting eggs is a feature with both biological and economic importance.Since the buoyancy of resting eggs is dependent on the specific weight of the eggs or salinity of ambient water,we suppose that habitat salinity may exert a selection pressure on resting egg buoyancy,and thereby lower habitat salinity may result in better floating capacity of resting eggs and vice versa.In this study,we compared the floating capacity of resting eggs from 25 Artemia populations.The results showed that the floating capacity of resting eggs varied greatly among different populations.The minimum salinity to float some eggs varied from 0 to 180.The salinity at which all resting eggs floated varied from 80 to 320.The FS_(50)(salinity with 50%eggs floating)of Zhundong and Yuncheng population was not detectable(over 50%eggs floating in distilled water),that of Kyêbxang Co population was 4.3,while the maximum value found in Dabancheng population was 234.5.In terms of the‘apparent specific weight’of resting eggs,18 populations exhibited a single-peak distribution pattern,while the other 7 populations showed a multiple-peak or non-peak distribution.Negative correlations were found between FS50 and chorion thickness,and between FS_(50) and the volume percentage of the chorion in eggs,supporting a previous standpoint that shell thickness was a determinative factor for the floating capacity of resting eggs.A positive correlation was determined between FS50 and habitat salinity.The hypothesis that habitat salinity may cause a directional selection on the buoyancy of resting eggs seems to be true.
文摘In cross sections by microscopic studies have examined the features of the shell thickness grains, cells, aleuronic layer and endosperm in the species T. dicoccum Schuebl., sorts Mironovskaya-808 and their interspecific hybrids F9 （alloplasmatic lines）. The result of studies showed the specific and varietal differences, and differences in hybrid plants on linear parameters size grains, the degree of specificity of the shells grains of wheat and identified species and varietal differences as well as differences among hybrids in the linear dimensions of the cells of the aleuronic layer. It is shown that among the studied forms of wheat allocated species T. dicoccum Shuebl. and the lines D-N-05, D-F-05 and D-40-05-KhNA with relatively large grains, a well-developed endosperm, most of thin shells and large grain aleurone layer cells. They are of most interest for further breeding research in terms of nutritional value.
