Achieving Energy-Efficient Uplink URLLC with MIMO-Aided Grant-Free Access

The optimal design of the energy-efficient multiple-input multiple-output (MIMO) aided uplink ultra-reliable low-latency communications (URLLC) system is an important but unsolved problem. For such a system, we propose a novel absorbing-Markov-chain-based analysis framework to shed light on the puzzling relationship between the delay and reliability, as well as to quantify the system energy efficiency. We derive the transition probabilities of the absorbing Markov chain considering the Rayleigh fading, the channel estimation error, the zero-forcing multi-user-detection (ZF-MUD), the grant-free access, the ACK-enabled retransmissions within the delay bound and the interactions among these technical ingredients. Then, the delay-constrained reliability and the system energy efficiency are derived based on the absorbing Markov chain formulated. Finally, we study the optimal number of user equipments (UEs) and the optimal number of receiving antennas that maximize the system energy efficiency, while satisfying the reliability and latency requirements of URLLC simultaneously. Simulation results demonstrate the accuracy of our theoretical analysis and the effectiveness of massive MIMO in supporting large-scale URLLC systems.Comment: 14 pages, 9 figures, accepted to appear on IEEE Transactions on Wireless Communications, Aug. 202

Analysis and Design of a Novel Multiband Antenna for Mobile Terminals

A multiband planar terminal antenna with a compact size of 40 mm × 24 mm is proposed in this paper. This antenna consists of a monopole patch with two slots on it and a meandering strip loaded on the top. Two parasitic stubs and a branch on the ground are used to adjust and widen the impedance bandwidth of the antenna. Simulations and measurements are carried out to study the antenna performances in terms of impedance matching, efficiency, gain, and radiation patterns. Both of simulation and measurement results are shown to illustrate the good performance of the proposed antenna. The antenna can operate at 450–474 MHz, 860–1040 MHz, 1705–2428 MHz, and 2500–2710 MHz. These operating bandwidths cover GSM900, DCS, PCS, UMTS, LTE2500, and LTE’s low frequency band (450–470 MHz). It is very suitable for multifunctional terminal applications in wireless communication systems

The effects of O-MWNTs,PEG and PVP additives on the performances of polyvinylidene fluoride(PVDF) membranes

Introducing hydrophilic additives is an effective method to improve the structure and permeation performance of polyvinylidene fluoride (PVDF) membranes.In this work,oxidized multi-wall carbon nanotubes (O-MWNTs) accompanied with polyethylene glycol/polyvinyl pyrrolidone (PEG/PVP) additives were employed to modify PVDF membranes.The effects of additives on the structure,permeation performances,hydrophilicity and crystallization behavior of the prepared PVDF membranes were investigated in detail.The results indicate that the addition of O-MWNTs can enhance the permeation flux,hydrophilicity and mechanical property of PVDF membranes.The pure water flux(PWF) attains 222.9±12.5 L·m-2·h-1·bar-1 and 256.9±14.8 L·m-2·h-1·bar-1 by adding 0.6 wt.% O-MWNTs accompanied with 5% PEG 200 and 3% PVP in the cast solution,respectively.PEG200 additive can enhance the dispersion of O-MWNTs,and accelerate the exchange rate between solvent and non-solvent.PVP working as pore-forming agent promotes the growth of pores of PVDF membranes and pure water permeation flux

An integrated decision-making framework for highway autonomous driving using combined learning and rule-based algorithm

In order to solve the manual labelling, long-tail effect and driving conservatism of the existing decision-making algorithm. This paper proposed an integrated decision-making framework (IDF) for highway autonomous vehicles. Firstly, states of the highway traffic are extracted by the velocity, time headway (TH) and the probabilistic lane distribution of the surrounding vehicles. With the extracted traffic state, the reinforcement learning (RL) is adopted to learn the optimal state-action pair for specific scenario. Analogously, by mapping millions of traffic scenarios, huge amounts of state-action pairs can be stored in the experience pool. Then the imitation learning (IL) is further employed to memorize the experience pool by deep neural networks. The learning result shows that the accuracy of the decision network can reach 94.17%. Besides, for some imperfect decisions of the network, the rule-based method is taken to rectify by judging the long-term reward. Finally, the IDF is simulated in G25 highway and has promising results, which can always drive the vehicle to the state with high efficiency while ensuring safety.This work was supported in part by the National Nature Science Foundation of China under Grants 52072175 and 51775007 and in part by the China Scholarship Council under Grant 202006830050

Study of the Mechanism of the Fe-BHA Chelates in Scheelite Flotation

Scheelite associated with calcium-containing minerals such as calcite and fluorite is difficult to separate by flotation because of the Ca ions contained in the mineral lattices, which cause scheelite to have similar surface properties and floatability to gangue minerals. Traditional collectors such as oleic acid need to add a large amount of sodium silicate as gangue inhibitors, which causes difficulties for the settlement of tailings. In addition, the use of benzohydroxamic acid (BHA), which needs the addition of Pb(NO3)2 as the scheelite activator, can also cause environmental pollution. In this paper, Fe-BHA, a new collector containing the iron complex, was studied to investigate its flotation ability of scheelite, as well as its BHA/FeCl3 ratio on scheelite flotations. In the single mineral flotations, the Fe-BHA showed a significant difference in the flotation recoveries of scheelite and calcite, with a scheelite recovery of 77.03% at pH 8.0 and calcite recovery of 16.69% at the same pH. The results of the roughing tests of Xianglushan actual ore showed that the scheelite with Fe-BHA (500 g/t BHA and 200 g/t FeCl3) and 40 g/t oleic acid as collectors obtained satisfactory flotation results with a WO3 grade of 1.56% and WO3 recovery of 65.52%, which were much higher than those of scheelite with BHA or oleic acid as the collector, but there was still a gap with those of scheelite using Pb(NO3)2 as activation and BHA as the collector. The UV-Vis curves of the Fe-BHA with different BHA/FeCl3 ratios indicated that the Fe-BHA chelates might have several different structural forms, and the single mineral tests of the BHA/FeCl3 ratios showed that when the molar ratio of benzohydroxamic acid to FeCl3 was about 1.2:1, the best scheelite flotation result was obtained in this test. In addition, the XPS analyses proved that the adsorption of the Fe-BHA on the scheelite surface occurred, and by fitting the peaks of Ca 2p and O 1s of scheelite, it was found that the mechanism of the Fe-BHA acting on the Ca sites of the scheelite surface was through the removal of H2O from the Ca-OH of scheelite and Fe-OH from Fe-BHA to form Fe-O-H

Study of the Mechanism of the Fe-BHA Chelates in Scheelite Flotation

Scheelite associated with calcium-containing minerals such as calcite and fluorite is difficult to separate by flotation because of the Ca ions contained in the mineral lattices, which cause scheelite to have similar surface properties and floatability to gangue minerals. Traditional collectors such as oleic acid need to add a large amount of sodium silicate as gangue inhibitors, which causes difficulties for the settlement of tailings. In addition, the use of benzohydroxamic acid (BHA), which needs the addition of Pb(NO3)2 as the scheelite activator, can also cause environmental pollution. In this paper, Fe-BHA, a new collector containing the iron complex, was studied to investigate its flotation ability of scheelite, as well as its BHA/FeCl3 ratio on scheelite flotations. In the single mineral flotations, the Fe-BHA showed a significant difference in the flotation recoveries of scheelite and calcite, with a scheelite recovery of 77.03% at pH 8.0 and calcite recovery of 16.69% at the same pH. The results of the roughing tests of Xianglushan actual ore showed that the scheelite with Fe-BHA (500 g/t BHA and 200 g/t FeCl3) and 40 g/t oleic acid as collectors obtained satisfactory flotation results with a WO3 grade of 1.56% and WO3 recovery of 65.52%, which were much higher than those of scheelite with BHA or oleic acid as the collector, but there was still a gap with those of scheelite using Pb(NO3)2 as activation and BHA as the collector. The UV-Vis curves of the Fe-BHA with different BHA/FeCl3 ratios indicated that the Fe-BHA chelates might have several different structural forms, and the single mineral tests of the BHA/FeCl3 ratios showed that when the molar ratio of benzohydroxamic acid to FeCl3 was about 1.2:1, the best scheelite flotation result was obtained in this test. In addition, the XPS analyses proved that the adsorption of the Fe-BHA on the scheelite surface occurred, and by fitting the peaks of Ca 2p and O 1s of scheelite, it was found that the mechanism of the Fe-BHA acting on the Ca sites of the scheelite surface was through the removal of H2O from the Ca-OH of scheelite and Fe-OH from Fe-BHA to form Fe-O-H

Shakedown Analysis and Experimental Study of Thermal Barrier Coatings

Interfacial stress–strain fields become complicated in thermal barrier coatings (TBCs) under cyclic thermal loading, which affects the stability and spalling failure of TBCs directly. The convex and concave interfacial structures of TBCs were approximated as a multilayer cylinder model, and an analytical method of TBCs for shakedown analysis was established. A series of 8-YSZ TBC specimens were prepared by the plasma spraying process, followed by isothermal and thermal shock tests. The results showed that the stability limit is significantly greater than the elastic limit, the limit for the convex model was higher than that in the concave model, the first failure occurs in the concave area, and the main failure mode of a thermal barrier coating is the appearance of cracks at the interface layer during a thermal shock test. For the coating samples prepared in this study, the stability limits were between 950 °C and 1050 °C, and the validity of the stability limit analysis model of a multilayer structure was verified

Advanced Sensing and Control for Connected and Automated Vehicles

In recent years, connected and automated vehicles (CAV) have been a transformative technology that is expected to reduce emissions and change and improve the safety and efficiency of the mobilities [...]PolyU (UGC): A004025