Factors affecting accuracy of radial point interpolation meshfree method for 3-D solid mechanics

Recently,the radial point interpolation meshfree method has gained popularity owing to its advantages in large deformation and discontinuity problems,however,the accuracy of this method depends on many factors and their influences are not fully investigated yet.In this work,three main factors,i.e.,the shape parameters,the influence domain size,and the nodal distribution,on the accuracy of the radial point interpolation method(RPIM)are systematically studied and conclusive results are obtained.First,the effect of shape parameters(R,q)of the multi-quadric basis function on the accuracy of RPIM is examined via global search.A new interpolation error index,closely related to the accuracy of RPIM,is proposed.The distribution of various error indexes on the R q plane shows that shape parameters q[1.2,1.8]and R[0,1.5]can give good results for general 3-D analysis.This recommended range of shape parameters is examined by multiple benchmark examples in 3D solid mechanics.Second,through numerical experiments,an average of 30 40 nodes in the influence domain of a Gauss point is recommended for 3-D solid mechanics.Third,it is observed that the distribution of nodes has significant effect on the accuracy of RPIM although it has little effect on the accuracy of interpolation.Nodal distributions with better uniformity give better results.Furthermore,how the influence domain size and nodal distribution affect the selection of shape parameters and how the nodal distribution affects the choice of influence domain size are also discussed.

AN ANALYSIS ON LARGE-SCALE AIR-SEA INTERACTIVE LINKAGES BETWEEN THE TROPICAL INDIAN OCEAN AND THE PACIFIC OCEAN DURING ENSO EVENTS

By utilizing a 3-D atmospheric circulation resolving method, the authors studied the air-sea interactive linkages between the tropical Indian Ocean and the Pacific Ocean in 1979-2008 E1 Nifio-Southern Oscillation （ENSO） events. Their findings showed that evident 3-D gear-coupling characteristics existed in the 1979-2008 ENSO events. Their resolving analyses also suggested that the general circulation showed stronger and wider sinking motions over the eastern Indian Ocean-western Pacific during the mature phase of 1979-2008 ENSO events, compared with the vertical velocities from the U.S. National Centers for Enviornmental Prediction （NCEP） reanalysis data. With their 3-D analysis method, the vertical velocity was resolved by two components, i.e. zonal and meridional components. It was found that the zonal component of the vertical velocities showed a strong sinking motion while the meridional components showed an upward motion during the prevailing phases of the ENSO events. In the tropics, the zonal component of the vertical velocities was found greater than the meridional component, reflecting the dominant characteristics of the vertical velocity, and the overall outcomes showed a strong sinking motion, although the two components also partially offset each other in the processes. Compared with the vertical velocities from NCEP reanalysis, the vertical motions calculated with the 3-D resolving analysis method demonstrate some advantages.

Using 3-D magnetic modeling to evaluate subsurface structures of the Siwa Oasis,Western Desert,Egypt

This work was designed to study the subsurface structures in the Siwa Oasis area of the Western Desert in Egypt and to determine their effects on surface geologic structures. A detailed land magnetic survey was performed in traverses covering about 400 km2 of the study area. The measured total magnetic field was corrected and reduced to the north magnetic pole. The reduction-to-pole aeromagnetic and Bouguer anomaly maps were used to obtain regional extensions of these subsurface structures, study the continuation of these structures in sedimentary rocks, and delineate the depths to the basement rocks. Data analysis was performed using trend analysis, Euler deconvolution, Werner deconvolution, the Hilbert transform of the analytical signal, and 3-dimensional magnetic modeling methods. The results indicate that the area is affected by tectonic forces in the E-W, N45°-65°E, and N35°-45°W trends, which are correlated with the directions of surface geologic lineaments. The depth to the basement rocks increases from 3.2 km in the southern part to about 3.6 km in the northern part of the area. The results are in good agreement with depths obtained from drill hole data in the area.