Tightly Coupled 3D Lidar Inertial Odometry and Mapping

Ego-motion estimation is a fundamental requirement for most mobile robotic applications. By sensor fusion, we can compensate the deficiencies of stand-alone sensors and provide more reliable estimations. We introduce a tightly coupled lidar-IMU fusion method in this paper. By jointly minimizing the cost derived from lidar and IMU measurements, the lidar-IMU odometry (LIO) can perform well with acceptable drift after long-term experiment, even in challenging cases where the lidar measurements can be degraded. Besides, to obtain more reliable estimations of the lidar poses, a rotation-constrained refinement algorithm (LIO-mapping) is proposed to further align the lidar poses with the global map. The experiment results demonstrate that the proposed method can estimate the poses of the sensor pair at the IMU update rate with high precision, even under fast motion conditions or with insufficient features.Comment: Accepted by ICRA 201

Evaluation on the Influence of the Timing of Twin Pregnancy Termination on the Outcome of Mother and Infants

Objective: To observe the maternal and infant outcomes of pregnant women with twins terminating their pregnancy at different timings.  Methods: Among the twin pregnant women admitted to our hospital from August 2019 to August 2020, 50 primiparous women who opted to terminate their pregnancies at 5 different timings of “34——34+6 weeks”, “35——35+6 weeks”, “36——36+6 weeks”, “37——37+6 weeks”, “38——38+6 weeks” were selected as the research subjects. According to the timing of pregnancy termination, they were divided into 5 groups, each with 10 cases of pregnant women, and the impact of the timing of pregnancy termination on the outcome of the mothers and infants were compared.  Results: The “37——37+6 weeks” group had the largest amount of postpartum hemorrhage, and the difference in Hb level before and after delivery was the largest. With the increase in gestational week, the weight of both large and small fetuses increased. In terms of neonatal diseases, the comparison between “34——34+6 weeks”, “35——35+6 weeks”, “36——36+6 weeks” and “37——37+6 weeks”, “38——38+6 weeks”, P＜0.05, the comparison between “37——37+6 weeks” and “38——38+6 weeks”, P>0.05.  Conclusion: The extension of the gestational week of twin pregnancies has no effect on postpartum hemorrhage, but it can improve the outcome of infants

Wetting transition energy curves for a droplet on a square-post patterned surface

Due to the property of water repellence, biomimetic superhydrophobic surfaces have been widely applied to green technologies, in turn inducing wider and deeper investigations on superhydrophobic surfaces. Theoretical, experimental and numerical studies on wetting transitions have been carried out by researchers, but the mechanism of wetting transitions between Cassie-Baxter state and Wenzel state, which is crucial to develop a stable superhydrophobic surface, is still not fully understood. In this paper, the free energy curves based on the transition processes are presented and discussed in detail. The existence of energy barriers with or without consideration of the gravity effect, and the irreversibility of wetting transition are discussed based on the presented energy curves. The energy curves show that different routes of the Cassie-to-Wenzel transition and the reverse transition are the main reason for the irreversibility. Numerical simulations are implemented via a phase field lattice Boltzmann method of large density ratio, and the simulation results show good consistency with the theoretical analysis

Effect of resistive load on the performance of an organic Rankine cycle with a scroll expander

An experimental investigation is performed for an organic Rankine cycle system with different electrical resistive loads. The test rig is set up with a small scroll expander-generator unit, a boiler and a magnetically coupled pump. R134a is used as the working fluid in the system. The experimental results reveal that the resistive load coupled to the scroll expander-generator unit affects the expander performance and power output characteristics. It is found that an optimum pressure ratio exists for the maximum power output. The optimal pressure ratio of the expander decreases markedly as the resistive load gets higher. The optimum pressure ratio of the scroll expander is 3.6 at a rotation speed of 3450 r/min for a resistive load of 18.6 Ω. The maximum electrical power output is 564.5 W and corresponding isentropic and volumetric efficiencies are 78% and 83% respectively

HGCN-GJS: Hierarchical Graph Convolutional Network with Groupwise Joint Sampling for Trajectory Prediction

Accurate pedestrian trajectory prediction is of great importance for downstream tasks such as autonomous driving and mobile robot navigation. Fully investigating the social interactions within the crowd is crucial for accurate pedestrian trajectory prediction. However, most existing methods do not capture group level interactions well, focusing only on pairwise interactions and neglecting group-wise interactions. In this work, we propose a hierarchical graph convolutional network, HGCN-GJS, for trajectory prediction which well leverages group level interactions within the crowd. Furthermore, we introduce a novel joint sampling scheme for modeling the joint distribution of multiple pedestrians in the future trajectories. Based on the group information, this scheme associates the trajectory of one person with the trajectory of other people in the group, but maintains the independence of the trajectories of outsiders. We demonstrate the performance of our network on several trajectory prediction datasets, achieving state-of-the-art results on all datasets considered.Comment: 8 pages, 5 figures, in submission to conferenc