Accurate three-dimensional reconstruction of duodenum is very important in the navigation of ERCP surgery, which helps to improve the success rate of chathete-rization and reduce the difficulty of surgery. Due to the narrow anatomical space of the duodenum, the structure is tortuous, the surface is smooth with few texture features. The existing three-dimensional reconstruction and positioning methods still cannot achieve an effective performance. In this paper, the combination of electromagnetic sensing and ORBSLAM is used for the three-dimensional reconstruction of the duodenal biliary and pancreatic duct. First, we use the accurate tracking performance of electromagnetic sensors to improve the effectiveness of SLAM mapping. Second, we replaced the pose estimation of the camera in SLAM with electromagnetic sensing real-time pose, which improved the real-time performance of 3D reconstruction. The effectiveness and real-time performance of the algorithm in the three-dimensional reconstruction of the duodenum, biliary and pancreatic regions are verified through high-simulation models and real clinical video sequences.
A large amount of crude oil still adheres to the rock surface after water flooding in low-permeability reservoirs. Cations in the formation water were assumed to play a crucial role in crude oil adhesion. However, it lacks systematic investigation, and the mechanism remains unclear. In this work, the role of cations in these oil–rock interactions is investigated by performing water flooding experiments and molecular dynamics simulations. Results show that Ca2+ has a significant impact on the injection pressure and the oil recovery than Na+. The oil recovery of cores initially saturated by CaCl2 solution (39.02–47.48%) was lower than those saturated by NaCl solution (51.78–54.96%). It was found that the hydrated cations accumulate on the negatively charged rock surface to form a brine layer. The interaction energy between crude oil and rock surface was 1.7 times 0.5 M NaCl (−14.2 × 103 kJ·mol–1) when the brine layer contained 0.5 M CaCl2 (−24.2 × 103 kJ·mol–1), leading to the strong adhesion of crude oil. Thus, the amount of residual oil was higher in the presence of Ca2+ after water flooding. With the increase in Ca2+ concentration, the adhesion of crude oil became stronger, significantly reducing the efficiency of water flooding.
This study explored the effect of adding different concentrations of carbon nanotubes (CNTs) on the resistance to chloride ions penetration of cement mortars through natural penetration of chloride ions and Mercury IntrusionPorosimetry.The experimental results of natural penetration of chloride ions showed that, the chloride ions penetration depth of the samples which added with CNTs were deeper than the control group which was without the addition of CNTs in the case of 35 days, 45 days, 55 days, 65 days of natural penetration of chloride ions, and the penetration depth increased with the content of CNTs.However, Mercury Intrusion Porosimetry (MIP) experimental results indicated that the porosity of cement mortar incorporated CNTs instead decreased, so the speculation that adding CNTs makes the porosity of the cement mortar specimens increase resulting in the increase of the penetration depth can be excluded.Another assumption was proposed that there may be a water film on the surface of the CNTs, and this water film can accelerate the penetrating speed of chloride ions as a convenient channel.
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