Description: To meet the great needs for MFL (magnetic flux leakage) inspection of drill pipes at wellheads, a lift-off-tolerant MFL testing method is proposed and investigated in this paper. Firstly, a Helmholtz coil magnetization method and the whole MFL testing scheme are proposed. Then, based on the magnetic field focusing effect of ferrite cores, a lift-off-tolerant MFL sensor is developed and tested. It shows high sensitivity at a lift-off distance of 5.0 mm. Further, the follow-up high repeatability MFL probing system is designed and manufactured, which was embedded with the developed sensors. It can track the swing movement of drill pipes and allow the pipe ends to pass smoothly. Finally, the developed system is employed in a drilling field for drill pipe inspection. Test results show that the proposed method can fulfill the requirements for drill pipe inspection at wellheads, which is of great importance in drill pipe safety.

Description: Author(s): Xiaofei Shao, Xiaobiao Liu, Xinrui Zhao, Junru Wang, Xiaoming Zhang, and Mingwen Zhao Two-dimensional (2D) lattices composed exclusively of pentagons represent an exceptional structure of materials correlated to the famous pentagonal tiling problem in mathematics, but their π conjugation and the related electronic properties have never been reported. Here, we propose a tight-binding ... [Phys. Rev. B 98, 085437] Published Thu Aug 30, 2018

Description: Sensors, Vol. 18, Pages 1385: Geometric Integration of Hybrid Correspondences for RGB-D Unidirectional Tracking Sensors doi: 10.3390/s18051385 Authors: Shengjun Tang Wu Chen Weixi Wang Xiaoming Li Walid Darwish Wenbin Li Zhengdong Huang Han Hu Renzhong Guo Traditionally, visual-based RGB-D SLAM systems only use correspondences with valid depth values for camera tracking, thus ignoring the regions without 3D information. Due to the strict limitation on measurement distance and view angle, such systems adopt only short-range constraints which may introduce larger drift errors during long-distance unidirectional tracking. In this paper, we propose a novel geometric integration method that makes use of both 2D and 3D correspondences for RGB-D tracking. Our method handles the problem by exploring visual features both when depth information is available and when it is unknown. The system comprises two parts: coarse pose tracking with 3D correspondences, and geometric integration with hybrid correspondences. First, the coarse pose tracking generates the initial camera pose using 3D correspondences with frame-by-frame registration. The initial camera poses are then used as inputs for the geometric integration model, along with 3D correspondences, 2D-3D correspondences and 2D correspondences identified from frame pairs. The initial 3D location of the correspondence is determined in two ways, from depth image and by using the initial poses to triangulate. The model improves the camera poses and decreases drift error during long-distance RGB-D tracking iteratively. Experiments were conducted using data sequences collected by commercial Structure Sensors. The results verify that the geometric integration of hybrid correspondences effectively decreases the drift error and improves mapping accuracy. Furthermore, the model enables a comparative and synergistic use of datasets, including both 2D and 3D features.

Description: Sustainability, Vol. 10, Pages 1372: Measuring the Direct and Indirect Effects of Neighborhood-Built Environments on Travel-related CO2 Emissions: A Structural Equation Modeling Approach Sustainability doi: 10.3390/su10051372 Authors: Wenyue Yang Shaojian Wang Xiaoming Zhao Intervening in the built environment is a key way for land-use and transport planning and related policies to promote low-carbon development and low-carbon travel. It is of significance to explore and recognize the actual impact of the neighborhood built environment on travel-related CO2 emissions. This study calculated the CO2 emissions from four purposes of trips, which were within the urban region, using Travel O-D Point Intelligent Query System (TIQS) and 1239 residents’ travel survey questionnaires from 15 neighborhoods in Guangzhou. It measured the direct and indirect effects of built environments on CO2 emissions from different purposes of trips by developing structural equation models (SEMs). The results showed that for different purposes of trips, the effects of the neighborhood built environments on CO2 emissions were inconsistent. Almost all built environment elements had significant total effects on CO2 emissions, which were mainly indirect effects through mediators such as car ownership and trip distance, then affecting CO2 emissions indirectly. Most of the direct effects of neighborhood built environments on CO2 emissions were not significant, especially those from non-commuting trips. These findings suggest that in the process of formulating low-carbon oriented land-use and transport planning and policies, the indirect effects of the built environments should not be ignored, and the differences of the effects of the neighborhood built environments among different purposes of the trip should be fully considered.