ABSTRACT
Global registration is an important step in the three-dimensional reconstruction of multi-view laser point clouds for moving objects, but the severe noise, density variation, and overlap ratio between multi-view laser point clouds present significant challenges to global registration. In this paper, a multi-view laser point cloud global registration method based on low-rank sparse decomposition is proposed. Firstly, the spatial distribution features of point clouds were extracted by spatial rasterization to realize loop-closure detection, and the corresponding weight matrix was established according to the similarities of spatial distribution features. The accuracy of adjacent registration transformation was evaluated, and the robustness of low-rank sparse matrix decomposition was enhanced. Then, the objective function that satisfies the global optimization condition was constructed, which prevented the solution space compression generated by the column-orthogonal hypothesis of the matrix. The objective function was solved by the Augmented Lagrange method, and the iterative termination condition was designed according to the prior conditions of single-object global registration. The simulation analysis shows that the proposed method was robust with a wide range of parameters, and the accuracy of loop-closure detection was over 90%. When the pairwise registration error was below 0.1 rad, the proposed method performed better than the three compared methods, and the global registration accuracy was better than 0.05 rad. Finally, the global registration results of real point cloud experiments further proved the validity and stability of the proposed method.
ABSTRACT
A hybrid drug delivery system coloaded with different drugs for synergistic drug delivery was developed. Alginate/calcium carbonate (CaCO3) hybrid microparticles (MPs) were fabricated via a facile coprecipitation method under mild conditions without using any organic solvent and surfactant. Due to the incorporation of negatively charged alginate chains onto the surface, the obtained hybrid MPs with spherical morphology showed good colloidal stability in an aqueous solution. An antitumor drug (doxorubicin, DOX) and a drug resistance reversal agent (verapamil, VP) were coloaded in the hybrid MPs simultaneously to obtain dual-drug-loaded MPs (DOX/VP/MP). Due to the presence of inorganic CaCO3 (â¼54 wt%), the drugs could be loaded in the hybrid MPs with high encapsulation efficiency and the drug release could be effectively sustained. The cell growth inhibition of the drug-loaded MPs was evaluated in HeLa cells. An in vitro study showed DOX/VP/MP exhibited higher cell growth inhibition as compared with DOX monodrug-loaded MPs (DOX/MP). These results suggest the hybrid MPs can potentially be used as a synergistic drug delivery platform for cancer chemotherapy.
