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Graphical abstract Highlights • Nb 2 O 5 -MO x were synthesized by sol-gel method to mix the elements at atom level. • Strong interaction between Nb 2 O 5 and MO x influences the physicochemical properties. • Nb 2 O 5 -TiO 2 exhibits high catalytic activity for 1,2-dichloroethane combustion. • Synergistic catalytic effect is observed in the Nb 2 O 5 -MO x catalysts. Abstract Nb 2 O 5 based solid superacids (Nb 2 O 5 -MO x , M = Ti, W, Zr, Si, Al and Ca, respectively) were synthesized by sol-gel method using citric acid as the cross-linking agent, and then were investigated for catalytic combustion of 1,2-dichloroethane (abbreviation: DCE), one of the typical examples for chlorinated VOCs pollutants. The research results of the structure-performance relationship show that mesopore and amorphous state structure are formed for Nb 2 O 5 -MO x , and the metal elements are highly dispersed, which contribute to enhancing the metal-metal interaction and modifying the physicochemical properties of the catalysts. The order for the inherent catalytic activity is: Nb 2 O 5 -WO 3 ＞Nb 2 O 5 -ZrO 2 ＞Nb 2 O 5 -TiO 2 ＞Nb 2 O 5 -SiO 2 ＞Nb 2 O 5 -Al 2 O 3 ＞Nb 2 O 5 ＞Nb 2 O 5 -CaO. There exists synergistic catalytic effect: the mesopore and surface acidity facilitate the adsorption, activation and destruction of the C Cl bond in the reactants to form HCl and byproduct C 2 H 3 Cl (or carbocation intermediate), and then the redox sites promote deep oxidation of the byproduct/intermediate to convert to CO 2 and H 2 O. Especially, the Nb 2 O 5 -TiO 2 catalyst represents the highest apparent catalytic degradation activity. It also represents good thermal stability and durability for DCE destruction as well as good resistance to water vapor. [ABSTRACT FROM AUTHOR]

[Display omitted] • We implement more accurate optical flow tracking by the assistance of IMU. We use the rotated tracked points obtained by an IMU to initialize the estimation of the optical flow, and this can improve the reliability of the initial feature points. To obtain accurate feature matching, a stereo baseline constraint and ring matching are used to remove outlier points. The experiments show that the information fused with a stereo camera and an IMU achieves real-time optical flow tracking and more accurate feature matching than the LK optical flow method. Compared with the feature matching method in ORB-SLAM3, the proposed method is more lightweight and faster. • We develop a high-precision SLAM framework that integrates stereo vision and an IMU to tackle the problem of pose inaccuracy that results from the fast movement of a stereo camera and insufficient view overlap between frames. We build a new objective function based on VINS to reduce the complexity of the computation. We adopt a sliding window to ensure the real time performance of the system, and the marginalized information is added as a prior in the objective function. The experimental results demonstrate that the localization accuracy of the proposed SLAM framework is better than that of OKVIS, VINS-Mono and VINS-Fusion. • We propose a fast method for constructing dense point maps to estimate depth values based on stereo vision and an IMU. The depth value computed by SGBM (semi-global block matching) is regarded as the initial value to update the depth of the deep filter, which can improve the convergence rate. We further adopt the TSDF (truncated signed distance function) to fuse the depth images obtained by stereo matching and build a dense map. The experiments show that the proposed stereo dense reconstruction method can obtain a deeper image, less convergence time for the estimated picture and fewer updating frames than the REMODE (probabilistic, monocular dense reconstruction) method. Mobile vehicles require accurate localization and dense mapping for motion planning. In this paper, we propose a dense map construction algorithm based on a light-and-fast stereo visual-inertial navigation system (VINS). A tightly coupled nonlinear optimization method is used to calculate the position of adjacent keyframes. An optical flow tracking method fused with IMU information and ring matching constraints is used to improve the matching accuracy and speed of the feature points. In addition, we obtain the pose and depth values using the semi-global block matching (SGBM) method, which are used as the initial values of the depth filter to update the depth image and improve the convergence speed. Then, we further use the Truncated Signed Distance Function (TSDF) method to construct the dense map. We compare our algorithm with state-of-the-art algorithms on the EuRoc dataset and then compare the estimated depth image using the proposed algorithm and the point cloud construction with the probabilistic monocular dense reconstruction (REMODE). The experiments show that the proposed algorithm can obtain more accurate localization than VINS and OKVIS, as well as a faster tracking speed, a better depth map, a lower convergence time for the estimated image and a lower number of updated frames than REMODE. [ABSTRACT FROM AUTHOR]

Cooperative vehicles are better able to detect the environment and self-localize than a single vehicle. Cooperative vehicles can quickly cover the entire environment by communicating and cooperating with each other and can also reduce localization and mapping error by merging the cooperative vehicle information from observation and navigation. In this paper, we propose a novel algorithm for an effective solution of navigation and mapping for cooperative vehicles in an unknown environment. We present an improved centralized and collaborative monocular simultaneous localization and mapping (CCM-SLAM) approach. The proposed algorithm can accurately compute the transformation matrix for cooperative vehicle maps and reduce the communication delay, data loss among vehicles and decrease the bandwidth demand. The quaternion and credibility similarity transformation (QC-Sim(3)) method we proposed is used to accurately merge the matched maps and accomplish loop closures. The sending messages at variable frequencies (SMVF) method we proposed and an improved detection and resending lost data (I-DRLD) method we proposed can improve the accuracy of pose estimation. SMVF solves the time-delay problem by sending messages to the vehicles at flexible frequencies while I-DRLD detects and resends the lost data. We also adopt Intra-frame Feature Compression (IFC) to decrease the bandwidth demand in the process of the transmitting data. The experiments demonstrate the superiority of our proposed algorithm compared with the state-of-the-art methods. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Nb 2 O 5 -TiO 2 were synthesized by the sol-gel method. • Strong interaction between Nb 2 O 5 and TiO 2 influences the physicochemical properties. • Nb 2 O 5 -TiO 2 exhibit higher activity for 1,2-dichloroethane combustion than single metal oxides. • Synergistic catalytic effect is observed in Nb 2 O 5 -TiO 2 catalyst system. Abstract The Nb 2 O 5 -TiO 2 catalyst system was synthesized via sol-gel method and investigated for adsorption/catalytic combustion of toxic 1,2-dichloroethane (DCE), which was usually recognized as a representative of various chlorinated and brominated VOCs pollutants. The research results of structure-performance relationship revealed that binary Nb 2 O 5 -TiO 2 were amorphous and mesoporous materials with pore diameter mainly in the range of 2–10 nm, and Nb and Ti elements were uniformly dispersed. The interaction between Nb 2 O 5 and TiO 2 coupled with the molar ratio of Nb/Ti improved the physicochemical properties of Nb 2 O 5 -TiO 2. Moreover, Nb 2 O 5 -TiO 2 exhibited higher catalytic activity for DCE combustion than single Nb 2 O 5 or TiO 2. Especially, the 2Nb1Ti catalyst (Nb/Ti = 2:1, molar ratio) displayed the highest activity, over which 90% conversion of DCE could be achieved at 295 °C. These results were related to that the interaction effect between Nb 2 O 5 and TiO 2 improved acidity and oxidizing properties, and the materials had large surface area, all of which were favorable for adsorbing DCE at relatively low temperatures (below 93 °C) on Nb 2 O 5 -TiO 2 and then improving catalytic combustion performance at lower reaction temperatures than Nb 2 O 5 or TiO 2. Besides, during the long-term continuous reaction, even though partial deactivation was observed for this catalyst, it could be suppressed at elevated temperature. [ABSTRACT FROM AUTHOR]