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Flight Time Minimization of UAV for Cooperative Data Collection in Probabilistic LoS Channel

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China Communications 2024年第2期21卷 210-226页

作者： Yan Li Shaoyi Xu Yunpu Wu Dongji Li school of electronic and Information engineering Beijing Jiaotong UniversityBeijing 100044China school of Electrical engineering and electronic Information Xihua UniversityChengdu 610039China

This paper investigates the data collection in an unmanned aerial vehicle(UAV)-aided Internet of Things(IoT) network, where a UAV is dispatched to collect data from ground sensors in a practical and accurate probabilistic line-of-sight(LoS) channel. Especially, access points(APs) are introduced to collect data from some sensors in the unlicensed band to improve data collection efficiency. We formulate a mixed-integer non-convex optimization problem to minimize the UAV flight time by jointly designing the UAV 3D trajectory and sensors’ scheduling, while ensuring the required amount of data can be collected under the limited UAV energy. To solve this nonconvex problem, we recast the objective problem into a tractable form. Then, the problem is further divided into several sub-problems to solve iteratively, and the successive convex approximation(SCA) scheme is applied to solve each non-convex subproblem. Finally,the bisection search is adopted to speed up the searching for the minimum UAV flight time. Simulation results verify that the UAV flight time can be shortened by the proposed method effectively.

关键词： data collection flight time probabilistic line-of-sight channel unlicensed band unmanned aerial vehicle

Influence and optimization of swirler parameters on elbow wear of deep coal fluidization pipeline transportation system

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Friction 2024年第7期12卷 1408-1433页

作者： Shaodi ZHAO Jiusheng BAO Shirong GE Zhongbin WANG Yan YIN Congguang HUANG school of mechanical and Electrical engineering China University of Mining and TechnologyXuzhou 221116China school of mechanical electronic and Information engineering China University of Mining and Technology-BeijingBeijing 100083China Frontier Scientific Research Center for Fluided Mining of Deep Underground Resources China University of Mining and TechnologyXuzhou 221008China

Elbow wear is a major threat to the multiphase pipeline transportation industry,which has a negative impact on the stable operation of the transportation *** order to find the wear reduction methods of elbows in the fluidization pipeline transportation system for 2000-meter-deep coal resources,the swirler was installed upstream of the elbows,and wear simulations and tests of three kinds of elbows were carried *** results showed that the maximum wear rate(MWR)of elbows increased and then decreased along the elbow *** to the different directions of gravity,the heavy wear position(HWP)of the horizontal-vertical(H-V)elbow was in front of the vertical-horizontal(V-H)*** the downstream portion of the horizontal-horizontal(H-H)elbow was still a horizontal pipe,the HWP of the H-H elbow almost covered the whole *** swirler placed upstream of the elbows could make the particles at the elbow move to the intrados of the elbows,resulting in less collision between the particles and the extrados of the elbows,thus reducing the wear of the *** wear reduction effects of swirlers on three different elbows were favorably connected with the guide vane angle(GVA)and negatively correlated with the guide vane length(GVL),decreased first and then increased as the guide vane height(GVH)increased,and were little affected by the guide vane number(GVN)and the guide vane thickness(GVT).The mathematical models between the MWR of the elbows and guide vane parameters were *** bench tests,the wear reduction effect of three kinds of elbows under the optimal guide vane parameters was 58.4%,76.9%,and 78.6%,*** errors between the bench test results and the simulation results were around 10%.

关键词： pipe elbow erosion wear spiral flow swirler guide vane parameters particle collision

One-step growth of ultrathin CoSe_(2)nanobelts on N-doped MXene nanosheets for dendrite-inhibited and kinetic-accelerated lithium-sulfur chemistry

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Science Bulletin 2024年第13期69卷 2059-2070页

作者： Chuanliang Wei Zhengran Wang Peng Wang Xinlu Zhang Xuguang An Jinkui Feng Baojuan Xi Shenglin Xiong school of Chemistry and Chemical engineering School of Materials Science and EngineeringShandong UniversityJinan 250100China school of mechanical engineering Chengdu UniversityChengdu 610106China

The practical application of lithium–sulfur(Li–S)batteries is inhibited by the shuttle effect of lithium polysulfides(LiPSs)and slow polysulfide redox kinetics on the S cathode as well as the uncontrollable growth of dendrites on the Li metal ***,both cathode and anode sides must be considered when modifying LiS ***,two-dimensional(2D)ultrathin CoSe_(2)nanobelts are in situ grown on 2D N-doped MXene nanosheets(CoSe_(2)@N-MXene)via one-step solvothermal process for the first *** to its unique 2D/2D structure,CoSe_(2)@N-MXene can be processed to crumpled nanosheets by freeze-drying and flexible and freestanding films by vacuum *** crumpled CoSe_(2)@NMXene nanosheets with abundant active sites and inner spaces can act as S hosts to accelerate polysulfide redox kinetics and suppress the shuttle effect of LiPSs owing to their strong adsorption ability and catalytic conversion effect with ***,the CoSe_(2)@N-MXene film(CoSe_(2)@NMF)can act as a current collector to promote uniform Li deposition because it contains lithiophilic CoSe_(2)and N *** the systematic effect of CoSe_(2)@N-MXene on S cathode and Li metal anode,the electrochemical and safety performance of Li–S batteries are ***_(2)@NMF also shows excellent storage performances in flexible energy storage devices.

关键词： Ultrathin CoSe_(2)nanobelts N-doped MXene nanosheets In situ growth Flexible MXene-based films Li-S batteries

Carbon nanotubes and hexagonal boron nitride nanosheets co-filled ethylene propylene diene monomer composites:Improved electrical property for cable accessory applications

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High Voltage 2024年第3期9卷 546-555页

作者： Tiandong Zhang Huiduo Xu Chuanxian Dai Changhai Zhang Yongquan Zhang Qingguo Chi school of Electrical and electronic engineering Harbin University of Science and TechnologyHarbinChina

Rubber-based composites based on ethylene propylene diene monomer(EPDM)with excellent non-linear electrical conductivity are preferred to serve as reinforced insu-lation in cable accessories,which can self-adaptively regulate electric field distribution and avoid electric field concentration due to the non-linear *** conductive carbon nanotubes(CNT)are filled into EPDM to improve the non-linear conductivity,while the insulating hexagonal boron nitride nanosheets(h-BN)are used to reconcile the electric breakdown *** results show that with the increase of CNT loading content,the non-linear conductivity of CNT/h-BN/EPDM com-posites becomes more prominent,accompanying the decrease of threshold field strength and increase of non-linear ***,the electric breakdown strength of CNT/h-BN/EPDM composites seriously deteriorates due to the increase of CNT content and *** incorporating 10 wt.%h-BN into the com-posites,the reduction percentage of breakdown strength can be significantly lowered,which is 19.95%of neat EPDM and 13.74%of CNT/h-BN/EPDM composites at 70℃,*** COMSOL Multiphysics simulation results demonstrate that using the CNT/h-BN/EPDM composite as the reinforced insulation can eliminate the electric field concentration of the cable accessory as well as enable the cable accessory with good lightning shock resistance.

关键词： composites hexagonal boron

Formal Modeling of Frame Selection in Asynchronous TSN Communications

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Chinese Journal of electronics 2024年第2期33卷 549-563页

作者： Ershuai LI Xuan ZHOU Jinjing SUN Huagang XIONG Feng HE school of electronic and Information engineering Beihang University

The asynchronous time-sensitive networking(TSN) based on IEEE 802.1Qcr is expected to be a promising solution for the asynchronous transmissions of safety-critical flows without the support of clock *** the asynchronous traffic shaping(ATS) mechanism is adopted to meet the deadline requirements for transmissions of safety-critical flow, it is necessary to formally verify the real-time properties and corresponding network ***, it is still unclear how to build an efficient formal model to evaluate different frame selection methods during the ATS scheduling process, which originate from the dominations of priority or eligibility time. In this paper, we present a formal modeling framework to compare the impacts of different frame selection on transmission sequence under the ATS mechanism. According to the priority level(p ATS) or eligibility time(e ATS) for flows, two transmission selection methods in ATS are modeled and compared. Then, we verify the real-time properties of ATS. The result shows that the shaping-for-free property can be satisfied with the p ATS method but can not be fulfilled with the e ATS method. Besides, the timing analysis results illustrate that the e ATS method can provide more fairness than the p ATS method for the transmission of low-priority flows in TSN networks.

关键词： System recovery Real-time systems Delays Synchronization

The Active Compensation Technique for Large Reflector Antennas Based on Quadratic Curve Fitting

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Research in Astronomy and Astrophysics 2024年第7期24卷 226-234页

作者： Tian-Xiang Zheng Bin-Bin Xiang Han-Wei Cui Wei Wang Pei-Yuan Lian Shang-Ming Lin Yang Zhang Jian-Ping Zhou Kai Li school of mechanical engineering Xinjiang UniversityUrumqi 830017China school of Mechano-electronic engineering Xidian UniversityXi’an 710017China Xi’an Institute of Optics and Precision Mechanics Chinese Academy of SciencesXi’an 710119China

Active reflectors are often used to compensate the surface distortion caused by environmental factors that degrade the electromagnetic performance of large high-frequency reflector *** is crucial for maintaining high gain operation in antennas.A distortion compensation method for the active reflector of a large dual-reflector antenna is proposed.A relationship is established between the surface deformation and the optical path difference for the primary reflector by geometric ***,employing finite element analysis,a polynomial fitting approach is used to describe the impact of adjusting points on the reflector surface based on the coordinates of each *** standardizing the positions of various panels on the reflector,the fitting ns can be applied to the reflector panels of similar ***,based on the distribution characteristics of the primary reflector panels,the adjustment equation for the actuators is derived by the influence matrix *** can be used to determine the adjustment amount of actuators to reduce the rms of the optical path ***,the least squares method is employed to resolve the matrix *** example of a 110 m aperture dual-reflector antenna is carried out by finite element analysis and the proposed *** results show that the optical path difference is reduced significantly at various elevation cases,which indicates that the proposed method is effective.

关键词： Methods analytical-Methods numerical-Telescopes

A comparison of cross-correlation-based and phasecorrelation-based image registration algorithms for optical coherence tomographic angiography

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Chinese Optics Letters 2024年第7期22卷 19-28页

作者： Yurui Pu Chaoliang Chen school of electronic Science&engineering Southeast UniversityNanjing 210096China

A large field of view is in high demand for disease diagnosis in clinical applications of optical coherence tomography(OCT)and OCT angiography(OCTA)*** to limits on the optical scanning range,the scanning speed,or the data processing speed,only a relatively small region could be acquired and processed for most of the current clinical OCT systems at one time and could generate a mosaic image of multiple adjacent small-region images with registration algorithms for disease *** this work,we investigated performing cross-correlation(instead of phase-correlation)in the workflow of the Fourier–Mellin transform(FMT)method(called dual-cross-correlation-based translation and rotation registration,DCCTRR)for calculating translation and orientation offsets and compared its performance to the FMT method used on OCTA images *** phantom and in vivo experiments were implemented for comparisons,and the results quantitatively demonstrate that DCCTRR can align OCTA images with a lower overlap rate,which could improve the scanning efficiency of large-scale imaging in clinical applications.

关键词： optical coherence tomography optical coherence tomographic angiography:image registration cross-correlation phase-correlation.

A complementary binary code based phase unwrapping method

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Optoelectronics Letters 2024年第4期20卷 228-233页

作者： LI Wenjie SUN Huanghe LI Fuquan WANG Beibei WANG Haijian GAO Xinyu school of mechanical and Electrical engineeringGuilin University of electronic Technology Guilin 541004China

Phase unwrapping is used to establish the mapping relationship between camera and projector,which is one of the key technologies in fringe projection profilometry(FPP)based three-dimensional(3D)*** complementary Gray code assisted phase unwrapping technology can get a good result on the periodic boundary,it needs more coded images to obtain a high frequency *** at this problem,a complementary binary code assisted phase unwrapping method is proposed in this *** to the periodic consistency between the wrapping phase and binary codes,the coded patterns are *** the connected domain strategy is performed to calculate the fringe orders using the positive and negative image *** avoid the mistake near the periodic boundary,complementary binary code inspired by the complementary Gray code is *** fringe order correction is also discussed for different situations in the first measured *** two binary images are needed in the proposed method,and the fringe frequency is not *** the simulation and experiment have verified the feasibility of proposed method.

关键词： method. complementary phase

Experimental and numerical study of combustion characteristics of ammonia-hydrogen-air swirling flame with/without secondary air injection

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Chinese Journal of Aeronautics 2024年第4期37卷 243-255页

作者： Chunyu LIU Chenhu GAO Yue HUANG Hua JIN Dan ZHAO Wenjiang XU Yancheng YOU school of Aerospace engineering Xiamen UniversityXiamen 361005China school of mechanical engineering Shanghai Jiao Tong UniversityShanghai 200240China Department of mechanical engineering University of CanterburyChristchurch 8041New Zealand

Ammonia (NH_(3)) is currently considered to be a potential carbon-free alternative fuel,and its large-scale use as such would certainly decrease greenhouse gas emissions and meet increasingly stringent emission *** the low flame propagation speed and high NO production of NH_(3) hinder its direct application as a renewable fuel,co-combustion of NH_(3)–H_(2)is an effective way to overcome these *** this study,the combustion characteristics of NH_(3)–H_(2)swirling flames under different equivalence ratios and H_2blending ratios conditions are both numerically and experimentally ***,the One-Dimensional (1D) laminar flame computation presents a comparison base and the Three-Dimensional (3D) numerical simulation yields detailed flame property ***,the high-speed camera takes instantaneous swirl flame images and the gas analyzer measures the NO emission at the exit plane of the flame *** and quantitative analysis is performed on the flame structure and NO emission for a series of NH_(3)–H_(2)swirl *** variation trends of the NO emission calculated using different techniques agree very *** quantitative results show that the NO emissions are much higher at lean equivalence ratios than those at rich equivalence ratios,and such difference is closely related to the combustion flame ***,it is shown that the utilization of secondary air injection can achieve a significant reduction in NO emissions at the exit of the combustion chamber at equivalence ratios less than or equal to 0.9.

关键词： Ammonia combustion Swirling flow NO emission characteristics Secondary combustion Chemical reaction mechanism