Summary: A grid falling film tower (GFFT) has been invented as an ideal polycondensation reactor. In this reactor, polymer melt flows through multi‐layers grids from top to bottom to form falling film owing to gravity without agitation and shear; large gas‐liquid interfacial area is generated; the grids are perpendicular between adjacent layers to ensure film renewal and to achieve uniformly flowing. The fluid flow in this reactor has little back‐mixing and dead zone, which is near to plug flow. All melts are under the state of thin film which avoids the negative effect of hydrostatic head on the mass transfer impetus. Furthermore, the GFFT has wide operation flexibility as well as adjustable configuration parameters to meet different demands. A pilot scale GFFT with the height of 4.0 meters has been applied to polyester polycondensation process. The intrinsic viscosity of polyethylene terephthalate increased from 0.45 dl/g to 0.8–0.9 dl/g successfully. GFFT is supposed to be an universal apparatus for many devolatilization processes.

In recent years, underwater wireless sensor networks (UWSNs) have received extensive attention due to their application in the development of marine resources. The underwater acoustic channel has a long delay, low bandwidth, and highly dynamic changes in the underwater environment so that the existing technologies and protocols in the traditional wireless sensor network cannot be directly applied to underwater. This paper studies the medium access control (MAC) protocol and positioning technology of UWSNs and introduces the typical underwater line sensor network MAC protocol. Aiming at the problem of spatial fairness caused by the propagation characteristics of the underwater acoustic channel and the triple terminal problem caused by the long propagation delay in UWSNs, and effectively implementing the multi-channel mechanism, an underwater multi-channel based on a single transceiver is proposed, which is SFM-MAC. The existing underwater positioning algorithms are divided into two categories, centralized positioning algorithm and distributed positioning algorithm, and each type of algorithm is briefly explained. In this paper, the Markov chain is used to construct the reservation model of the control channel, and the theoretical analysis of multi-channel throughput is given. The theoretical throughput of the multi-channel MAC protocol under the condition of reserved collision is obtained. Finally, this paper verifies the actual performance of SFM-MAC through simulation experiments. INDEX TERMS Underwater wireless sensor networks, MAC protocol, localization algorithm, fairness, hidden terminal.

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To solve the persistently multiple object tracking in cluttered environments, this paper presents a novel tracking association approach based on the shortest path faster algorithm. First, the multiple object tracking is formulated as an integer programming problem of the flow network. Then we relax the integer programming to a standard linear programming problem. Therefore, the global optimum can be quickly obtained using the shortest path faster algorithm. The proposed method avoids the difficulties of integer programming, and it has a lower worst-case complexity than competing methods but better robustness and tracking accuracy in complex environments. Simulation results show that the proposed algorithm takes less time than other state-of-the-art methods and can operate in real time.