Collaborative positioning for swarms:A brief survey of vision,LiDAR and wireless sensors based methods

As positioning sensors,edge computation power,and communication technologies continue to develop,a moving agent can now sense its surroundings and communicate with other agents.By receiving spatial information from both its environment and other agents,an agent can use various methods and sensor types to localize itself.With its high flexibility and robustness,collaborative positioning has become a widely used method in both military and civilian applications.This paper introduces the basic fundamental concepts and applications of collaborative positioning,and reviews recent progress in the field based on camera,LiDAR(Light Detection and Ranging),wireless sensor,and their integration.The paper compares the current methods with respect to their sensor type,summarizes their main paradigms,and analyzes their evaluation experiments.Finally,the paper discusses the main challenges and open issues that require further research.

An improved particle filter indoor fusion positioning approach based on Wi-Fi/PDR/geomagnetic field

The existing indoor fusion positioning methods based on Pedestrian Dead Reckoning(PDR)and geomagnetic technology have the problems of large initial position error,low sensor accuracy,and geomagnetic mismatch.In this study,a novel indoor fusion positioning approach based on the improved particle filter algorithm by geomagnetic iterative matching is proposed,where Wi-Fi,PDR,and geomagnetic signals are integrated to improve indoor positioning performances.One important contribution is that geomagnetic iterative matching is firstly proposed based on the particle filter algorithm.During the positioning process,an iterative window and a constraint window are introduced to limit the particle generation range and the geomagnetic matching range respectively.The position is corrected several times based on geomagnetic iterative matching in the location correction stage when the pedestrian movement is detected,which made up for the shortage of only one time of geomagnetic correction in the existing particle filter algorithm.In addition,this study also proposes a real-time step detection algorithm based on multi-threshold constraints to judge whether pedestrians are moving,which satisfies the real-time requirement of our fusion positioning approach.Through experimental verification,the average positioning accuracy of the proposed approach reaches 1.59 m,which improves 33.2%compared with the existing particle filter fusion positioning algorithms.

The characteristics of mRNA m^(6)A methylomes in allopolyploid Brassica napus and its diploid progenitors

Genome duplication events,comprising whole-genome duplication and single-gene duplication,produce a complex genomic context leading to multiple levels of genetic changes.However,the characteristics of m^(6)A modification,the most widespread internal eukaryotic mRNA modification,in polyploid species are still poorly understood.This study revealed the characteristics of m^(6)A methylomes within the early formation and following the evolution of allopolyploid Brassica napus.We found a complex relationship between m^(6)A modification abundance and gene expression level depending on the degree of enrichment or presence/absence of m^(6)A modification.Overall,the m^(6)A genes had lower gene expression levels than the non-m^(6)A genes.Allopolyploidization may change the expression divergence of duplicated gene pairs with identical m^(6)A patterns and diverged m^(6)A patterns.Compared with duplicated genes,singletons with a higher evolutionary rate exhibited higher m^(6)A modification.Five kinds of duplicated genes exhibited distinct distributions of m^(6)A modifications in transcripts and gene expression level.In particular,tandem duplication-derived genes showed unique m^(6)A modification enrichment around the transcript start site.Active histone modifications(H3K27ac and H3K4me3)but not DNA methylation were enriched around genes of m^(6)A peaks.These findings provide a new understanding of the features of m 6A modification and gene expression regulation in allopolyploid plants with sophisticated genomic architecture.

Spin Transport Properties of MnBi_(2)Te_(4)-Based Magnetic Tunnel Junctions

The van der Waals heterojunctions,stacking of different two-dimensional materials,have opened unprecedented opportunities to explore new physics and device concepts.Here,combining the density functional theory with non-equilibrium Green’s function technique,we systematically investigate the spin-polarized transport properties of van der Waals magnetic tunnel junctions(MTJs),Cu/MnBi_(2)Te_(4)/MnBi_(2)Te_(4)/Cu and Cu/MnBi_(2)Te_(4)/hBN/n·MnBi_(2)Te_(4)/Cu(n=1,2,3).It is found that the maximum tunnel magnetoresistance of Cu/MnBi_(2)Te_(4)/hBN/3·MnBi_(2)Te_(4)/Cu MTJs can reach 162.6%,exceeding the system with only a single layer MnBi_(2)Te_(4).More interestingly,our results indicate that Cu/MnBi_(2)Te_(4)/h-BN/n·MnBi_(2)Te_(4)/Cu(n=2,3)MTJs can realize the switching function,while Cu/MnBi_(2)Te_(4)/h-BN/3·MnBi_(2)Te_(4)/Cu MTJs exhibit the negative differential resistance.The Cu/MnBi_(2)Te_(4)/h-BN/3·MnBi_(2)Te_(4)/Cu in the parallel state shows a spin injection efficiency of more than 83.3%.Our theoretical findings of the transport properties will shed light on the possible experimental studies of MnBi_(2)Te_(4)-based van der Waals magnetic tunneling junctions.

苯并噁嗪改性硅炔树脂固化行为及性能

通过含氰基和乙炔基的苯并噁嗪(BZ-BPA)改性聚(间二乙炔基苯一甲基氢硅烷)(PSA)制备了一系列BP共混树脂。采用傅里叶变换红外光谱、旋转流变仪、差示扫描量热分析、热重分析法分析了BP共混树脂的固化行为,结果表明,噁嗪环、硅氢键、端乙炔基、内乙炔基及氰基等活性基团均参与了固化反应。BP-3固化物在N_(2)和空气中热失重5%的温度(T_(d5))及1000℃质量保留率分别为687.3℃,92.1%和582.4℃,26.5%。石英纤维增强BP树脂复合材料(QF/BP)的力学性能和耐热性能测试结果显示,常温下弯曲强度从153.5 MPa提高至300.4 MPa、层剪剪切强度从21.6 MPa提高至35.6 MPa;400℃热氧化2 h后,QF/BP复合材料的力学强度保留率高于60%,600℃热氧化15 min后树脂结构已遭破坏;QF/BP-3的玻璃化转变温度(Tg)超过500℃。以上结果表明,BP共混树脂及其复合材料具有优异的耐热性能,力学性能有所提升。

Discussion on the role and practice of narrative medicine in China's COVID-19 epidemic

Narrative medicine is an important practice form of medical humanistic care.In COVID-19,the concept and practice of narrative medicine played an important role.This paper makes a distinction between the narrow sense and the broad sense of narrative medicine,and expounds in detail the characteristics and influence of the broad sense of narrative medicine in the epidemic situation,as well as the possible practice forms of the narrow sense of narrative medicine in the special period of the epidemic situation.Through reviewing the narrative medicine during the COVID-19,we hope to provide ideas for further expanding the connotation and application boundaries of narrative medicine.

All-perfluoropolymer,nonlinear stability-assisted monolithic surface combines topology-specific superwettability with ultradurability

Developing versatile and robust surfaces that mimic the skins of living beings to regulate air/liquid/solid matter is critical for many bioinspired applications.Despite notable achievements,such as in the case of developing robust superhydrophobic surfaces,it remains elusive to realize simultaneously topology-specific superwettability and multipronged durability owing to their inherent tradeoff and the lack of a scalable fabrication method.Here,we present a largely unexplored strategy of preparing an all-perfluoropolymer(Teflon),nonlinear stability-assisted monolithic surface for efficient regulating matters.

Large Tunneling Magnetoresistance and Perfect Spin Filtering Effect in van der Waals Cu/FeX_(2)/h-BN/FeX_(2)/Cu(X=Cl,Br,I)Magnetic Tunnel Junctions

The two-dimensional magnetic van der Waals heterojunctions have opened unprecedented opportunities to explore new physics due to their potential for spintronic applications.Here,combing density functional theory with non-equilibrium Green’s function technique.

Analysis on internal mechanism of zedoary turmeric in treatment of liver cancer based on pharmacodynamic substances and pharmacodynamic groups

Zedoary tumeric(Curcumae Rhizoma,Ezhu in Chinese)has a long history of application and has great potential in the treatment of liver cancer.The antiliver cancer effect of zedoary tumeric depends on the combined action of multiple pharmacodynamic substances.In order to clarify the specific mechanism of zedoary tumeric against liver cancer,this paper first analyzes the mechanism of its single pharmacodynamic substance against liver cancer,and then verifies the joint anti liver cancer mechanism of its“pharmacodynamic group”.By searching the research on the antihepatoma effect of active components of zedoary tumeric in recent years,we found that pharmacodynamic substances,including curcumol,zedoarondiol,curcumenol,curzerenone,curdione,curcumin,germacrone,β-elemene,can act on multi-target and multi-channel to play an antihepatoma role.For example,curcumin can regulate miR,GLO1,CD133,VEGF,YAP,LIN28B,GPR81,HCAR-1,P53 and PI3K/Akt/mTOR,HSP70/TLR4 and NF-κB.Wnt/TGF/EMT,Nrf2/Keap1,JAK/STAT and other pathways play an antihepatoma role.Network pharmacological analysis showed that the core targets of the“pharmacodynamic group”for anti-life cancer are AKT1,EGFR,MAPK8,etc,and the core pathways are neuroactive live receiver interaction,nitrogen metabolism,HIF-1 signaling pathway,etc.At the same time,by comparing and analyzing the relationship between the specific mechanisms of pharmacodynamic substance and“pharmacodynamic group”,it is found that they have great reference significance in target,pathway,biological function,determination of core pharmacodynamic components,formation of core target protein interaction,in-depth research of single pharmacodynamic substance,increasing curative effect and so on.By analyzing the internal mechanism of zedoary tumeric pharmacodynamic substance and“pharmacodynamic group”in the treatment of liver cancer,this paper intends to provide some ideas and references for the deeper pharmacological research of zedoary tumeric and the relationship between pharmacodynamic substance and“pharmacodynamic group”.

Terahertz synthetic aperture in-line holography with intensity correction and sparsity autofocusing reconstruction

We demonstrate high-resolution and high-quality terahertz(THz)in-line digital holography based on the synthetic aperture method.The setup is built on a self-developed THz quantum cascade laser,and a lateral resolution better than 70μm(~λ)is achieved at 4.3 THz.To correct intensity differences between sub-holograms before aperture stitching,a practical algorithm with global optimization is proposed.To address the twin-image problem for in-line holography,a sparsity-based phase retrieval algorithm is applied to perform the high-quality reconstruction.Furthermore,a new autofocusing criterion termed"reconstruction objective function"is introduced to obtain the best in-focus reconstruction distance,so the autofocusing procedure and the reconstruction are unified within the same framework.Both simulation and experiment prove its accuracy and robustness.Note that all the methods proposed here can be applied to other wavebands as well.We demonstrate the success of this THz synthetic aperture in-line holography on biological and semiconductor samples,showing its potential applications in bioimaging and materials analysis.

Numerical investigation of separation efficiency of the cyclone with supercritical fluid-solid flow

The utilization of hydrogen is gaining increasing attention due to its high heating value and environmentally friendly combustion product.The supercritical water circulating fluidized bed reactor is a promising and potentially clean technology that can generate hydrogen from coal gasification.Cyclone is a vital part of the reactor which can separate incomplete decomposition of pulverized coal particles from mixed working fluid.This paper aims to gain in-depth understanding of the cyclone separation mechanisms under supercritical fluid by computational fluid dynamics(CFD).Although the amount of supercritical carbon dioxide in mixed working fluid is minor,it obviously influences the flow fields and separation efficiency of a cyclone.The simulation results suggest that both the decreasing content of supercritical carbon dioxide and adding the extra dipleg cause the promoting performance of cyclones.Research findings could refine the design of supercritical fluid-solid cyclones.

TahcoRoll: fast genomic signature profiling viathinned automaton and rolling hash

Objectives:Genomic signatures like k-mers have become one of the most prominent approaches to describe genomic data.As a result,myriad real-world applications,such as the construction of de Bruijn graphs in genome assembly,have been benefited by recognizing genomic signatures.In other words,an efficient approachof genomic signatureprofiling is an essential need for tackling high-throughput sequencing reads.However,most of the existing approaches only recognize fixed-size k-merswhile many research studies have shown the importance of considering variable-length k-mers.Methods:In this paper,we present a novel genomic signature profiling approach,TahcoRoll,by extending the Aho–Corasick algorithm(AC)for the task of profiling variable-length k-mers.We first group nucleotides into two clusters and represent each cluster with a bit.The rolling hash technique is further utilized to encode signatures and read patterns for efficient matching.Results:In extensive experiments,TahcoRoll significantly outperforms the most state-of-the-art k-mer counters and has the capability of processing reads across different sequencing platforms on a budget desktop computer.Conclusions:The single-thread version of TahcoRoll is as efficient as the eight-thread version of the state-of-the-art,JellyFish,while the eight-thread TahcoRoll outperforms the eight-thread JellyFish by at least four times.

Color-kinematics duality for Sudakov form factor in non-supersymmetric pure Yang-Mills theory

We study the duality between color and kinematics for the Sudakov form factors of tr(F~2)in non-supersymmetric pure Yang-Mills theory.We construct the integrands that manifest the color-kinematics duality up to two loops.The resulting numerators are given in terms of Lorentz products of momenta and polarization vectors,which have the same powers of loop momenta as that from the Feynman rules.The integrands are checked by d-dimensional unitarity cuts and are valid in any dimension.We find that massless-bubble and tadpole topologies are needed at two loops to realize the color-kinematics duality.Interestingly,the two-loop solution contains a large number of free parameters suggesting the duality may hold at higher loop orders.

Failure responses of rock tunnel faces during excavation through the fault-fracture zone

It is essential to cast light on the construction risks in tunnel excavations through the fault-fracture zone(FFZ).This study adopts the material point method(MPM)to simulate the failure responses of a rock tunnel face during excavation through the FFZ.A numerical study was conducted to compare a physical model test and validate the feasibility of using the MPM in simulating tunnel face failure.One hundred ninety numerical simulation cases were constructed to represent a rock tunnel excavation project with different site con-figurations.The simulation results suggest that the cohesion and the friction angle significantly influence failure responses.The tunnel cover depth can magnify the failure responses,and the FFZ thickness significantly affects the mobilized rock mass volume when the FFZ consists of a weak rock mass.The numerical simulation results suggest three deformation patterns:face bulge,partial failure,and slide collapse.The failure responses can be characterized by stress arch,slip surface,angle of reposing,and influence range.The insights suggested by the face failure responses during excavation through the FFZ can aid field engineers in determining the scope of possible damage,and in establishing emergency measures to minimize losses if such failure occurs.

Viologens-based redox mediators with tunable HOMO–LUMO energy gap for highly effective hydrogen peroxide electrosynthesis

In comparison with the developing nano-carbon catalysts,some small organic molecules are also emerging as catalysts with typical features,however,their working mechanism is still unclear.Here,we synthesized a series of viologen-based heterogeneous catalysts with the same molecular skeleton but different substituent groups through anion exchange engineering.These viologen-based molecules were used as a model catalyst to investigate the underlying structure–function relationship for small molecules-based H_(2)O_(2) electrosynthesis.Differing from the commonly reported carbon-based electrocatalysts,viologens can produce H_(2)O_(2) in a synergistic manner,which means that viologens can not only directly catalyze oxygen reduction but also serve as a redox mediator.We found that the ring current and H_(2)O_(2) selectivity of viologens deliver an increasing trend with the increase of the alkyl chain length of alkyl-substituted viologens and further increase when using benzyl as the substituent group.As a result,a benzyl-substituted viologen(BV)delivers the best electrocatalytic performance among the samples,including the highest H_(2)O_(2) selectivity of 96.9%at 0.6 V and the largest ring current density of about 13.6 mA·mmol-1.Furthermore,density functional theory(DFT)calculations disclose that the carbon atoms bonded with positively charged N are the active sites and the small highest occupied molecular orbital(HOMO)–lowest unoccupied molecular orbital(LUMO)energy gap of BV is beneficial to the synergistic mechanism for H_(2)O_(2) production.This work sheds new insight into the efficient H_(2)O_(2) production in a synergistic manner for small molecules-based electrocatalysts.

Self-assembled multiepitope nanovaccine based on NoV P particles induces effective and lasting protection against H3N2 influenza virus

Current seasonal influenza vaccines confer only limited coverage of virus strains due to the frequent genetic and antigenic variability of influenza virus(IV).Epitope vaccines that accurately target conserved domains provide a promising approach to increase the breadth of protection;however,poor immunogenicity greatly hinders their application.The protruding(P)domain of the norovirus(NoV),which can self-assemble into a 24-mer particle called the NoV P particle,offers an ideal antigen presentation platform.In this study,a multiepitope nanovaccine displaying influenza epitopes(HMN-PP)was constructed based on the NoV P particle nanoplatform.Large amounts of HMN-PP were easily expressed in Escherichia coli in soluble form.Animal experiments showed that the adjuvanted HMN-PP nanovaccine induced epitope-specific antibodies and haemagglutinin(HA)-specific neutralizing antibodies,the antibodies could persist for at least three months after the last immunization.Furthermore,HMN-PP induced matrix protein 2 extracellular domain(M2e)-specific antibody-dependent cell-mediated cytotoxicity,CD4^(+)and CD8^(+)T-cell responses,a nucleoprotein(NP)-specific cytotoxic T lymphocyte(CTL)response.These results indicated that the combination of a multiepitope vaccine and self-assembled NoV P particles may be an ideal and effective vaccine strategy for highly variable viruses such as IV and SARS-CoV-2.

保留后鞘完整的隧道式造口预防造口旁疝疗效分析

目的比较传统造口方式与保留后鞘完整的隧道式造口方式的短期效果,探讨保留后鞘完整的隧道式造口预防造口旁疝的临床疗效。方法回顾性分析2014年3月至2021年4月在陕西省人民医院普外一科因低位直肠癌行永久性乙状结肠造口术的70例患者资料。均行腹腔镜经腹会阴联合直肠癌根治术,据造口方式不同分为对照组(传统结肠造口术)40例,试验组(保留后鞘完整的隧道式造口术)30例。对比分析2组患者一般资料,手术时长,术后造口排气时间,术后进食时间,造口一般并发症,造口旁疝发生率情况。结果2组患者在性别、年龄、体质量指数、肿瘤TNM分期,手术时长、术中出血量、术后造口排气时间、术后进食时间,造口一般并发症、切口感染方面比较差异均无统计学意义(P>0.05)。对照组造口旁疝发生率(27.5%)高于试验组(0),差异有统计学意义(P<0.05),对照组造口旁疝多发生于术后2周~3年。结论保留后鞘完整的隧道式造口可以在短期内预防造口旁疝。

Performance analysis of solar absorption-subcooled compression hybrid refrigeration system in subtropical city

Solar absorption-subcooled compression hybrid refrigeration system is a new type of efficient and economical solar refrigeration device which always meets the demand of cooling load with the change of solar irradiance.The perfonnance of the hybrid system is higher due to the improvement of evaporator temperature of absorption subsystem.But simultaneously,the variation of working process as well as performance is complicated since the absorption and compression subsystems are coupled strongly.Based on the measured meteorological data of Guangzhou,a subtropical city in south China,a corresponding parametric model has been developed for the hybrid refrigeration system,and a program written by Fortran has been used to analyze the performance of the hybrid system under different external conditions.As the condensation temperature ranges from 38°C to 50°C,the working time fraction of the absorption subsystem increases from 75%to 85%.Besides,the energy saving fraction also increases from 5.31%to 6.02%.The average COP of the absorption subsystem is improved from 0.366 to 0.407.However,when the temperature of the absorption increases from 36°C to 48°C,the average COP of hybrid system decreases from 2.703 to 2.312.Moreover,the working time fraction of the absorption subsystem decreases from 80%to 71.7%.The energy saving fraction falls from 5.67%to 5.08%.In addition,when the evaporate temperature increases from 4°C to 14°C,the average COP of the absorption subsystem decreases from 0.384 to 0.365.The work of the compressor decreases from 48.2 kW to 32.8 kW and the corresponding average COP of the absorption subsystem is improved from 2.591 to 3.082.