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Accuracy assessment of real-time kinematics(RTK)measurements on unmanned aerial vehicles(UAV)for Direct geo-referencing

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Geo-Spatial Information Science 2020年第2期23卷 165-181页

作者： Desta Ekaso Francesco Nex Norman Kerle Department of Earth Systems Analysis ITC-Faculty of Geo-Information Science and Earth Observation of the University of TwenteEnschedeThe NetherlandsDepartment of Earth Systems AnalysisITC-Faculty of Geo-Information Science and Earth Observation of the University of TwenteEnschedeThe NetherlandsDepartment of Earth Systems AnalysisITC-Faculty of Geo-Information Science and Earth Observation of the University of TwenteEnschedeThe Netherlands

Geospatial information acquired with Unmanned Aerial Vehicles(UAV)provides valuable decision-making support in many different domains,and technological advances coincide with a demand for ever more sophisticated data products.One consequence is a research and development focus on more accurately referenced images and derivatives,which has long been a weakness especially of low to medium cost UAV systems equipped with relatively inexpensive inertial measurement unit(IMU)and Global Navigation Satellite System(GNSS)receivers.This research evaluates the positional accuracy of the real-time kinematics(RTK)GNSS on the DJI Matrice 600 Pro,one of the first available and widely used UAVs with potentially surveying-grade performance.Although a very high positional accuracy of the drone itself of 2 to 3 cm is claimed by DJI,the actual accuracy of the drone RTK for positioning the images and for using it for mapping purposes without additional ground control is not known.To begin with,the actual GNSS RTK position of reference center(the physical point on the antenna)on the drone is not indicated,and uncertainty regarding this also exists among the professional user community.In this study the reference center was determined through a set of experiments using the dual frequency static Leica GNSS with RTK capability.The RTK positioning data from the drone were then used for Direct georeferencing,and its results were evaluated.Test flights were carried out over a 70 x 70 m area with an altitude of 40 m above the ground,with a ground sampling distance of 1.3 cm.Evaluated against ground control points,the planimetric accuracy of Direct georeferencing for the photogrammetric product ranged between 30 and 60 cm.Analysis of Direct georeferencing results showed a time delay of up to 0.28 seconds between the drone GNSS RTK and camera image acquisition affecting Direct georeferencing results.

关键词： UAV GNSS RTK Direct georeferencing aerial triangulation lever arm offset

Extending the operational lifetimes of all-Direct electron transfer enzymatic biofuel cells by magnetically assembling and exchanging the active biocatalyst layers on stationary electrodes

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Nano Research 2019年第4期12卷 767-775页

作者： Katharina Herkendell Andreas Stemmer Ran Tel-Vered Saumerstrasse 4 Nanotechnology Group D-MAVT ETH Zurich Ruschlikon CH-8803 Switzerland

Enzymatic biofuel cells promise green power generation from a variety of natural resources, yet these systems all suffer from time-dependent degradati on effects, in particular progress! ng inactivation of enzymes, which severely limit the operati on al lifetimes of such power sources. To extend operational lifetimes, we introduce a method to magnetically exchange exhausted enzymes for fresh ones. To this end, anodic and cathodic enzymes or enzyme cascades are immobilized on carbon coated magnetic nanoparticles. Under the action of suitable magnetic field gradie nts, these nano particles are assembled on the respective stati onary electrodes, or released from the electrodes for collection and subsequent excha nge. We dem on strate this method on a fructose/oxygen con suming biofuel cell emplo ying fructose dehydroge nase and bilirubin oxidase as well as on anodic and cathodic cascades employing fructose dehydrogenase/invertase and bilirubin oxidase/catalase, respectively. The en zyme-modified nan oparticles support Direct electro n transfer bioelectrocatalytic curre nts by wiring the redox active cofactors to the carbonaceous coating and from there to the electrode surfaces. The facile injection, assembly, and removal of enzyme-modified magnetic nan oparticles along with fuel solutio n provides a promisi ng approach to exte nd the operati on al lifetime of enzymatic biofuel cells without the need for exchanging entire systems including chambers and electrodes.

关键词： Direct electron transfer magnetic nanoparticle enzymatic biofuel cell recharge lifetime enzyme cascade

Animal models used to study Direct peripheral nerve repair: a systematic review

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Neural Regeneration Research 2020年第3期15卷 491-502页

作者： Francisco Javier Vela Guadalupe Martínez-Chacón Alberto Ballestín JoséLuis Campos Francisco Miguel Sánchez-Margallo Elena Abellán Department of Microsurgery Jesús Usón Minimally Invasive Surgery CentreCáceresSpain Scientific Director Jesús Usón Minimally Invasive Surgery CentreCáceresSpain

Objective:Peripheral nerve repair is required after traumatic injury.This common condition represents a major public health problem worldwide.Recovery after nerve repair depends on several factors,including the severity of the injury,the nerve involved,and the surgeon’s technical skills.Despite the precise microsurgical repair of nerve lesions,adequate functional recovery is not always achieved and,therefore,the regeneration process and surgical techniques are still being studied.Pre-clinical animal models are essential for this research and,for this reason,the focus of the present systematic review(according to the PRISMA statement)was to analyze the different animal models used in pre-clinical peripheral nerve repair studies.Data sources:Original articles,published in English from 2000 to 2018,were collected using the Web of Science,Scopus,and PubMed databases.Data selection:Only preclinical trials on Direct nerve repair were included in this review.The articles were evaluated by the first two authors,in accordance with predefined data fields.Outcome measures:The primary outcomes included functional motor abilities,daily activity and regeneration rate.Secondary outcomes included coaptation technique and animal model.Results:This review yielded 267 articles,of which,after completion of the screening,49 studies were analyzed.There were 1425 animals in those 49 studies,being rats,mice,guinea pigs,rabbits,cats and dogs the different pre-clinical models.The nerves used were classified into three groups:head and neck(11),forelimb(8)and hindlimb(30).The techniques used to perform the coaptation were:microsuture(46),glue(12),laser(8)and mechanical(2).The follow-up examinations were histology(43),electrophysiological analysis(24)and behavioral observation(22).Conclusion:The most widely used animal model in the study of peripheral nerve repair is the rat.Other animal models are also used but the cost-benefit of the rat model provides several strengths over the others.Suture techniques are currently the first option for n

关键词： nerve microsurgery peripheral nerve regeneration repair reconstruction Direct nerve repair animal model coaptation PRISMA systematic review

A study on periodic boundary condition in Direct numerical simulation for gas–solid flow

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Chinese Journal of Chemical Engineering 2020年第1期28卷 236-241页

作者： Shiwen Liu Xiaowen Liu Feiguo Chen Limin Wang Wei Ge State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China School of Chemical Engineering University of Chinese Academy of SciencesBeijing 100049China

Direct numerical simulation(DNS) of gas–solid flow at high resolution has been carried out by coupling the lattice Boltzmann method(LBM) for gas flow and the discrete element method(DEM) for solid particles. However,the body force periodic boundary condition(FPBC) commonly used to cut down the huge computational cost of such simulation has faced accuracy concerns. In this study, a novel two-region periodic boundary condition(TPBC) is presented to remedy this problem, with the flow driven in the region with body force and freely evolving in the other region. With simulation cases for simple circulating fluidized bed risers, the validity and advantages of TPBC are demonstrated with more reasonable heterogeneity of the particle distribution as compared to the corresponding case with FPBC.

关键词： Direct numerical simulation Periodic boundary condition Two-region periodic boundary condition Gas–solid flow Heterogeneity

Reaction kinetics during Direct alloying of manganese ore cored wire

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Journal of Iron and Steel Research(International) 2020年第3期27卷 282-294页

作者： Wei Wu Qi Gao Bo Zhang Hua-dong Meng Lu Lin Jia-qing Zeng Metallurgical Technology Research Department Central Iron and Steel Research InstituteBeijing 100081China State Key Laboratory of Refractory and Metallurgy Wuhan University of Science and TechnologyWuhan 430081HubeiChina

In order to increase the reaction rates between the molten steel and the slag and cut down the reduction time when the top slag of manganese ore is added into the molten steel,a method of Directly alloying manganese ore has been experimented in a 500-kg induction furnace.The results show that the manganese yield is greater than 90%when the wire feeding method is used.The manganese yield is 43.26%within 1 min.In contrast,the manganese yield for the top-slag adding process is only 10.98%for the same duration.The mass transfer rate of the manganese is greater in the molten steel than in the slag,and the limiting factor is the mass transfer rate of the manganese in the slag in the period of 10-30 min.The slag composition area is closer to the area of high melting point for the wire feeding method than for the top-slag adding process.During the slagging process,refining slag composed of C a O and SiO:is formed after 15 min;after 25-30 min,refining slag with a high basicity is formed and consists of CaO,SiO2 and Al203.

关键词： Manganese ore Cored wire Direct alloying process Reaction kinetics Mass transfer rate

Comparison between Direct repair and humana cellular nerve allografting during contralateral C7 transfer to the upper trunk for restoration of shoulder abduction and elbow flexion

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Neural Regeneration Research 2019年第12期14卷 2132-2140页

作者： Liang Li Wen-Ting He Ben-Gang Qin Xiao-Lin Liu Jian-Tao Yang Li-Qiang Gu Department of Orthopedic Trauma and Microsurgery the First Affiliated Hospital of Sun Yat-sen University

Direct coaptation of contralateral C7 to the upper trunk could avoid the interposition of nerve grafts. We have successfully shortened the gap and graft lengths, and even achieved Direct coaptation. However, Direct repair can only be performed in some selected cases, and partial procedures still require autografts, which are the gold standard for repairing neurologic defects. As symptoms often occur after autografting, human acellular nerve allografts have been used to avoid concomitant symptoms. This study investigated the quality of shoulder abduction and elbow flexion following Direct repair and acellular allografting to evaluate issues requiring attention for brachial plexus injury repair. Fifty-one brachial plexus injury patients in the surgical database were eligible for this retrospective study. Patients were divided into two groups according to different surgical methods. Direct repair was performed in 27 patients, while acellular nerve allografts were used to bridge the gap between the contralateral C7 nerve root and upper trunk in 24 patients. The length of the harvested contralateral C7 nerve root was measured intraoperatively. Deltoid and biceps muscle strength, and degrees of shoulder abduction and elbow flexion were examined according to the British Medical Research Council scoring system;meaningful recovery was defined as M3–M5. Lengths of anterior and posterior divisions of the contralateral C7 in the Direct repair group were 7.64 ± 0.69 mm and 7.55 ± 0.69 mm, respectively, and in the acellular nerve allografts group were 6.46 ± 0.58 mm and 6.43 ± 0.59 mm, respectively. After a minimum of 4-year follow-up, meaningful recoveries of deltoid and biceps muscles in the Direct repair group were 88.89% and 85.19%, respectively, while they were 70.83% and 66.67% in the acellular nerve allografts group. Time to C5/C6 reinnervation was shorter in the Direct repair group compared with the acellular nerve allografts group. Direct repair facilitated the restoration of shoulder abduction and elbow flexion. Thus

关键词： nerve regeneration contralateral C7 nerve root transfer nerve graft brachial plexus avulsion injury Direct repair human acellular nerve allograft shoulder function elbow function nerve transfer phrenic nerve accessary nerve neural regeneration

A looped heat-driven thermoacoustic refrigeration system with Direct-coupling configuration for room temperature cooling

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Science Bulletin 2019年第1期64卷 8-10页

作者： Huizhi Wang Limin Zhang Guoyao Yu Jianying Hu Ercang Luo Ying Ma Chao Jiang Xianxian Liu Key Laboratory of Cryogenics Technical Institute of Physics and Chemistry Chinese Academy of Sciences School of Engineering Science University of Chinese Academy of Sciences School of Future Technology University of Chinese Academy of Sciences

Heat-driven thermoacoustic refrigeration has drawn extensive concern in the past decades due to its advantages of high reliability and external heat-driven mechanism.In such a system,heat can be firstly converted into acoustic power and then the acoustical power drives a refrigerator to generate cooling effect without any moving mechanical components.So far,most of researches on heat-driven thermoacoustic refrigeration have focused on cryo- genic application,such as natural gas liquefaction [1,2].In addition, heat-driven thermoacoustic refrigeration also plays important roles in recovering waste heat and provides an environment- friendly alternative to the current abso'rption chiller especially in the small-scale power range [3-7].However,two main obstacles to use the thermoacoustic technology in practice are its relatively low cooling capacity and low cooling efficiency.Either the two-loop configuration proposed by Luo et al.[5]or the configuration of a one-unit refrigerator driven by a three-unit engine brought forward by Kees [6],they both suffer from phase-shifting tube and mismatch between the thermoacoustic engine (TAE)and thermoacoustic refrigerator (TAR).

关键词： Direct coupling Refrigeration system Thermoacoustic refrigeration driven by heat

Weakly-coupled mode division multiplexing over conventional multi-mode fiber with intensity modulation and Direct detection

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Frontiers of Optoelectronics 2019年第1期12卷 31-40页

作者： Juhao LI Zhongying WU Dawei GE Jinglong ZHU Yu TIAN Yichi ZHANG Jinyi YU Zhengbin LI Zhangyuan CHEN Yongqi HE State Key Laboratory of Advanced Optical Communication Systems and Networks Peking UniversityBeijing 100871China Wuhan Research Institute of Posts and Telecommunications Wuhan 430074China

Multi-mode fiber(MMF)links are expected to greatly enhance capacity to cope with rapidly increasing data traffic in optical short-reach systems and networks.Recently,mode division multiplexing(MDM)over MMF has been proposed,in which different modes in MMF are utilized as spatial channels for data transmission.Stronglycoupled MDM techniques utilizing coherent detection and multiplex-input-multiplex-output(MIMO)digital signal processing(DSP)are complex and expensive for shortreach transmission.So the weakly-coupled approach by significantly suppressing mode coupling in the fiber and optical components has been proposed.In this way,the signals in each mode can be independently transmitted and received using conventional intensity modulation and Direct detection(IM-DD).In this paper,we elaborate the key technologies to realize weakly-coupled MDM transmission over conventional MMF,including mode characteristic in MMF and weakly-coupled mode multiplexer/ demultiplexer(MUX/DEMUX).We also present the upto-date experimental results for weakly-coupled MDM transmission over conventional OM3 MMF.We show that weakly-coupled MDM scheme is promising for high-speed optical interconnections and bandwidth upgrade of already-deployed MMF links.

关键词： multi-mode fiber (MMF) mode division multiplexing (MDM) weak mode coupling intensity modulation and Direct detection (IM-DD)

Direct extraction of Mo(Ⅵ) from sulfate solution by synergistic extractants in the rotation column

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Chinese Journal of Chemical Engineering 2020年第2期28卷 445-455页

作者： Benyamin Shakib Meisam Torab-Mostaedi Mohammad Outokesh Mehdi Asadollahzadeh Department of Energy Engineering Sharif University of TechnologyP.O.Box 11365-8639TehranIran Materials and Nuclear Fuel Research School Nuclear Science and Technology Research InstituteP.O.Box:11365-8486TehranIran

Direct extraction of molybdenum from sulfate solution with synergistic extractants(mixture of D2EHPA and TBP)was studied in the rotation column.The influence of extractant concentration and initial pH of aqueous phase was studied in the bench scale experiments.The outcomes demonstrated that the synergistic solvent extraction enhances the constancy of the extracted complexes for transfer into the organic phase.In the continuous experiments,the effect of different operating parameters such as speed of agitation,inlet solvent flow rate and inlet aqueous flow rate on the holdup,mean drop size,drop size distribution,slip and characteristic velocities and extraction percentage were examined.Modified correlations were proposed for prediction of hydrodynamic parameters with consideration of reaction extraction condition in the rotation column.Furthermore,these correlations were compared with the experimental data.According to the results,the Direct extraction of Mo(Ⅵ)from aqueous solution and sulfuric media with extraction efficiency of 90.4%was obtained at higher rotor speed(240 r·min–1 rpm)in this column.

关键词： Direct extraction Molybdenum Rotation column Synergistic Extractant