Facile Synthesis of Uniform Hollow Hematite Sub-micro Spheres with Controllable Shell Thickness

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.

Characteristics of shell thickness in a slab continuous casting 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.

THE METHOD OF MULTIPLE SCALES APPLIED TO THE NONLINEAR STABILITY PROBLEM OF A TRUNCATED SHALLOW SPHERICAL SHELL OF VARIABLE THICKNESS WITH THE LARGE GEOMETRICAL PARAMETER

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.

NONLINEAR STABILITY OF TRUNCATED SHALLOW CONICAL SANDWICH SHELL WITH VARIABLE THICKNESS

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.

Nonlinear Analysis and Optimization of Shallow Shells of Variable Thickness

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.

NONLINEAR STABILITY OF TRUNCATED SHALLOW SPHERICALSHELL WITH VARIABLE THICKNESS UNDERUNIFORMLY DISTRIBUTED LOAD

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.

AXISYMMETRIC PROBLEMS OF CYLINDRICAL SHELLS WITH VARIABLE WALL THICKNESS

The purpose of this paper is to give the general solutions for axisymmetric eylindrical shells with paraholically varying wall thickness.

A Comparative Study on the Buoyancy of Resting Eggs from Different Artemia Populations, with Emphasis on Its Relationships with Habitat Salinity and Biometric Characters of Resting Eggs

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.