Metric Monocular Localization Using Signed Distance Fields

Metric localization plays a critical role in vision-based navigation. For overcoming the degradation of matching photometry under appearance changes, recent research resorted to introducing geometry constraints of the prior scene structure. In this paper, we present a metric localization method for the monocular camera, using the Signed Distance Field (SDF) as a global map representation. Leveraging the volumetric distance information from SDFs, we aim to relax the assumption of an accurate structure from the local Bundle Adjustment (BA) in previous methods. By tightly coupling the distance factor with temporal visual constraints, our system corrects the odometry drift and jointly optimizes global camera poses with the local structure. We validate the proposed approach on both indoor and outdoor public datasets. Compared to the state-of-the-art methods, it achieves a comparable performance with a minimal sensor configuration.Comment: Accepted to 2019 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS

RESEARCH ON UNBALANCED WEIGHING EXPERIMENT OF MULTI-POINT BRACED SWIVEL CABLE-STAYED BRIDGE

To guarantee the safety of the swivel process, the weighing experiment before the swivel is especially important. Based on this, this paper takes a twin-tower, double-cable prestressed concrete swivel cable-stayed bridge as the background and suggests a multi-point braced swivel weighing experiment involving the joint force of the arm-brace and the spherical hinge to solve problems such as a particular obstacle in the relying project's swivelling process. Firstly, the relevant weighing experiment formulas for various circumstances were theoretically derived. The field test results were then used to calculate the jacking force at the limit state during the jacking process, which was then substituted into the relevant formulae, and the relevant parameters of the weighing experiment were calculated. Finally, the counterweight is adjusted based on the weighing results to carry out the structural rotation. The angular velocity was stable during the swivelling process, and the structure was successfully swivelled. The successful practice of a multi-point braced swivel weighing experiment involving the joint force of the arm-brace, and the spherical hinge can provide a reference for the design and construction of similar bridges

A Dual-Bacterial Coupled Fermentation Strategy for Nicotinamide Mononucleotide Synthesis

In this study, a dual-bacterial coupled fermentation system containing nicotinamide nucleoside kinase (NRK) and polyphosphatase (PPK) was constructed, and the application of PPK-based ATP regeneration system in NMN production was achieved. First, engineering strains expressing NRK1 and NRK2 were constructed, and the highly active Escherichia coli BL21 (DE3)-pET28a-NRK1 was selected, with NMN yield and productivity of 5.17 g/L and 77.4%, respectively. Then, the induced expression conditions of NRK1 were optimized, and a low temperature of 16 ℃, an isopropyl-β-D-thiogalactopyranoside (IPTG) concentration of 0.7 mmol/L, an inoculation amount of 3% and an induction duration of 22 h were found to be optimal the soluble expression of NRK1 protein. The optimal synthesis conditions of NMN by E. coli BL21 (DE3)-pET28a-NRK1 were explored. It was found that after 12 h culture at 18 ℃ at an initial cell concentration of 100 g/L and a ratio of ATP to NR of 1:1.5, the highest yield of NMN of 5.73 g/L was obtained with a productivity of 85.78%. Finally, the optimal conditions that provided maximal NMN production (11.81 g/L) by coupled fermentation with E. coli BL21 (DE3) pET28a-PPK and E. coli BL21 (DE3)-pET28a-NRK1 were determined as 1:3.5, 1:2 and 16 h for ATP to NR ratio, initial cell concentration and fermentation time, respectively. The high-density dual-bacterial coupled fermentation strategy established in this study opens up a new pathway for high-efficiency, low-cost and large-scale production of NMN