Trajectory clustering is a cornerstone task in the field of trajectory mining. With the proliferation of deep learning, deep trajectory clustering has been widely researched to mine mobility patterns from massive unlabeled trajectories. Nevertheless, existing methods mostly ignore trajectories' temporal regularities, which are essential for mining fine-grained mobility patterns for applications including traveling group identification, transportation mode discovering, social security emergency, etc. To fill this gap, we propose ConDTC, a contrastive deep trajectory clustering method targeting for fine-grained mobility pattern mining. Specifically, we first design a spatial-temporal trajectory representation learning method which can capture both spatial and temporal regularities of trajectories synchronously. The proposed trajectory representation model can be used as a pre-trained model to serve various downstream trajectory mining tasks. Then, we construct a contrastive trajectory clustering module which optimizes trajectory representations and clustering performance simultaneously. Experimental results on three datasets validate that ConDTC can identify fine-grained mobility patterns by clustering trajectories with similar spatial-temporal mobility patterns together while separating those with different mobility patterns apart. Actually, ConDTC outperforms all state-of-the-art competitors substantially in terms of effectiveness, efficiency and robustness.
We report a facile "hydrothermal etching assisted crystallization" route to synthesize Fe(3)O(4)@titanate yolk-shell microspheres with ultrathin nanosheets-assembled double-shell structure. The as-prepared microspheres possess a uniform size, tailored shell structure, good structural stability, versatile ion-exchange capability, high surface area, large magnetization, and exhibit a remarkable catalytic performance.
Large-sized, crack-free silica monoliths with highly ordered mesostructure are prepared by a fast and easy way via liquid-paraffin-medium protected solvent evaporation. By employing the inert liquid paraffin as the morphology "protector", cracks of the materials can be successfully avoided and the processing time can be reduced to 8 h. The block copolymer−silica composite monoliths are transparent and crack-free with a large size. The mesoporous silica monoliths have been characterized by small-angle powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and nitrogen adsorption, which show that the materials have a highly ordered hexagonal mesostructure of space group p6mm and narrow pore size distribution, with a mean pore diameter of 5.65 nm. In addition, metal ions can be easily doped into the monoliths, indicating potential optical, electronic, magnetic, and catalytic properties. This fast synthetic method is valuable for the applications of mesostructured silica monoliths in optics and separation.
From polymer templates to mesoporous materials: With the reverse amphiphilic triblock copolymer PPO-PEO-PPO and a resol resin precursor an organic–organic self-assembly process leads to the formation of an ordered polymer and a carbon mesostructure with a face-centered-cubic Fdm symmetry and bimodal pores (see scheme). PPO=polypropylenoxide, PEO=polyethylenoxide. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2007/z603665_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
Mesoporous silica encapsulating upconversion luminescence NaYF(4) nanorods with uniform core-shell structures have been successfully synthesized by the surfactant-assistant sol-gel process. The thickness of ordered mesoporous silica shells can be adjusted from 50 to 95 nm by varying the amount of hydrolyzed silicate oligomer precursors from tetraethyl orthosilicate (TEOS), which further influences the BET surface area, pore volume, and the luminescence intensity. After coated with mesoporous silica shells, the hydrophobic nanorods is rendered to hydropholic simultaneously. The obtained beta-NaYF(4)@SiO(2)@mSiO(2) core-shell nanorods possess high surface area (71.2-196 m(2) g(-1)), pore volume (0.07-0.17 cm(3) g(-1)), uniform pore size distribution (2.3 nm), and accessible channels. Furthermore, the uniform core-shell nanorods show strong upconversion luminescence property similar to the hexagonal upconversion cores. The open mesopores can not only provide convenient transmission channels but also offer the huge location for accommodation of large molecules, such as fluorescent dyes and quantum dots. The secondary-excitation fluorescence of Rhodamine B is generated from the upconversion rare-earth fluoride nanorods cores to the fluorescent dyes loaded in the mesoporous silica shells.
Large cavities (≈10–12.3 nm) of cubic (Fm-3m) mesoporous silica without intergrowth are synthesized in the presence of block copolymer templates. The entrance sizes of these cavities can be adjusted in the range of ≈4–9 nm as confirmed by nitrogen sorption studies and an examination of the negative gold replicas. The 3D open mesostructures facilitate the transportation of biomolecules (see picture), as well as the replication of a large-pore (9 nm) cubic mesoporous carbon. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2003/z51027_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
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