Multi-View Laser Point Cloud Global Registration for a Single Object.

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.

[Preparation and catalytic activity of surface-modification CNTs/TiO2 composite photocatalysts].

A novel kind of carbon nanotubes/titanium dioxide (CNTs/TiO2) composite photocatalyst was prepared by a modified sol-gel method in which the nanoscaled TiO2 particles were uniformly deposited on the CNTs modified with poly(vinyl pyrrolidone) (PVP). The composites were characterized by a range of analytical techniques including high resolution transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results show the successful covering of the CNTs with PVP, forming core-shell structure. The nanoscaled TiO2 particles were uniformly deposited on the surface of CNTs reducing the bare CNTs which avoid losing the absorption and scattering of photons. The combination of CNTs and TiO2 particles imply the enhanced interactions between the CNTs and TiO2 interface which possibly becomes heterojunction. The composites become mesoporous crystalline TiO2 (anatase) clusters after annealing at 500 degrees C, and the surface area increases obviously. The photocatalytic activities of surface modification CNTs/TiO2 (smCNTs/TiO2) composites are extremely enhanced from the results of the photodegradation of methylene blue (MB).

[Mechanism study of fluoride adsorption by hydrous metal oxides].

Hydrous oxides of cerium, aluminum, nickel and copper were prepared by alkaline precipitation method. Langmuir adsorption isotherm was studied and specific surface area was measured by BET method through N2 adsorption-desorption process. IR characterization of hydrous metal oxides before and after fluoride adsorption was also studied. Results show that different hydrous metal oxides have different specific surface areas and their pore size distributions also are not all the same. Adsorption capacity is not directly dependent on the specific surface area. Isotherm study indicates that the adsorption follows Langmuir model and shows the feature of monolayer adsorption. IR study before and after fluoride adsorption shows that different hydrous metal oxides have similar adsorption sites in the same IR region as well as adsorption sites in the different IR region. The comprehensive interaction of these adsorption sites with fluoride ions results in the different adsorption capacity of different hydrous metal oxides.

[Removal of methyl orange from aqueous solution by magnetic carbon nanotubes].

Ferrocene was used as a catalyst, and xylene as carbon source. Chemical vapor deposition method was used to synthesize carbon nanotubes (CNTs). The CNTs were treated by oxidation method with concentrated nitric acid. Magnetic carbon nanotubes were prepared by using chemical co-precipitation. The products were characterized by field emission scanning electron microscope. This paper is concerned with the adsorption of methyl orange by magnetic carbon nanotubes. The best experimental conditions were found. Adsorbent solution was analyzed by UV-Vis adsorption spectra. At the same time, desorption and re-adsorption of methyl orange from magnetic CNTs were studied.