Virtual neighborhood technique for moduli spaces of holomorphic curves

We use the technique of Ruan(1999)and Li and Ruan(2001)to construct the virtual neighborhoods and show that the Gromov-Witten invariants can be defined as integrals over the top strata of the virtual neighborhoods.We prove that the invariants defined in this way satisfy all the axioms of Gromov-Witten invariants summarized by Kontsevich and Manin(1994).

Compressive properties of homemade carbon fiber composite laminates with delamination defect

Large numbers of aircraft composite structures were researched,and the distribution of delamination sizes and though thickness positions in the composite laminates were investigated.An experiment was conducted to probe into the effect of delamination sizes and through thickness positions on the compressive strengths of laminates with single embedded circular delamination with the most dangerous delamination sizes and positions defined from the distribution.A shell model was established for compressive strength prediction,and the virtual crack closure technique(VCCT) was employed for the strain energy release rate calculation.The finite element(FE) prediction was in good agreement with the experimental measurements,for the predicted compressive strengths stood within 10%error of experimental results.It was observed that the compressive strength was highly effected by the delamination size,while the though thickness position of delamination did not have significant effect on the compressive strength.

Compressive behavior of composite panels with deeply embedded delamination

The compressive behavior of laminates with a deeply embedded circular delamination was studied numerically and experimentally.In the finite element analysis(FEA),virtual crack closure technique(VCCT) and B-K law were employed to simulate the delamination growth,and the contact of the two substrates was considered.The effect of the delamination size and through-thickness position on the compressive behavior of laminates with an artificially embedded circular delamination was discussed.It is found that the through-thickness position affects the buckling mode,which then strongly influences delamination growth speed and direction,as well as the dominant component energy release rate(ERR).The numerical results agreed well with the experimental results.

Similarity Solution for the Synchronous Grouting of Shield Tunnel Under the Vertical Non-Axisymmetric Displacement Boundary Condition

Abstract.Similarity solution is investigated for the synchronous grouting of shield tunnel under the vertical non-axisymmetric displacement boundary condition in the paper.The synchronous grouting process of shield tunnel was simplified as the cylindrical expansion problem,which was based on the mechanism between the slurry and stratum of the synchronous grouting.The stress harmonic function on the horizontal and vertical ground surfaces is improved.Based on the virtual image technique,stress function solutions and Boussinesq’s solution,elastic solution under the vertical non-axisymmetric displacement boundary condition on the vertical surface was proposed for synchronous grouting problems of shield tunnel.In addition,the maximum grouting pressure was also obtained to control the vertical displacement of horizontal ground surface.The validity of the proposed approach was proved by the numerical method.It can be known fromthe parameter analysis that larger vertical displacement of the horizontal ground surface was induced by smaller tunnel depth,smaller tunnel excavation radius,shorter limb distance,larger expansion pressure and smaller elastic modulus of soils.