检索结果-南通市图书馆

Effects of dynamical spanwise retraction and stretch on flapping-wing forward flights

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第4期37卷 181-202页

作者： Kang lIU Bifeng SONG ang CHEN zhihe wang Dong XUE wenqing Yang School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China Intelligent Aircraft Research Center Chengdu Technological UniversityChengdu 610031China Research&Development Institute of Northwestern Polytechnical University in Shenzhen Shenzhen 518057China Harbin Institute of Technology Shenzhen 518055China

Birds and bats retract and stretch their wings dynamically during each flap in level flights, implying intriguing mechanisms for the aerodynamic performance improvement of flapping wings. A numerical investigation into the aerodynamic effects of such bio-inspired concept in forward flights has been performed based on a three-dimensional wing in plunging motion and a twosection wing in flapping motion. The currently considered Reynolds number and Strouhal number are Re=1.5×10^(5) and St=0.3, respectively. During the research, the mean angle of attack is varied in relatively wide ranges to achieve lift-thrust interconversion for the wings. The conclusive results show that dynamical spanwise retraction and stretch has induced three absolutely desirable scenarios for the oscillating wings in forward flights, namely producing more lift and consuming less power for a given thrust generation, producing more thrust and consuming less power for a given lift generation, and producing more lift and more thrust while consuming less power. Furthermore,the morphing wings have alleviated periodical aerodynamic load fluctuations compared with the non-morphing baseline. The mechanism of the aerodynamic effects of the bionic morphing mode is analyzed with the aid of field visualization. The current article is the first to reveal the absolute advantages of the bionic spanwise morphing. Hopefully, it may help comprehend the behaviors of natural fliers and provide inspirations for performance enhancement of micro artificial flappingwing vehicles.

关键词： Flapping wing Morphing wing Bionic Aerodynamics Vortex Flight

维普期刊数据库

Recent progress in single crystal perovskite X-ray detectors

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2024年第3期67卷 5-19页

作者： Xiao lIU Jun REN Yu-ang CHEN Xiangshun GENG Dan XIE Tian-ling REN School of Integrated Circuits Tsinghua University Beijing National Research Center for Information Science and Technology (BNRist)

Perovskites have attracted extensive attention as radiation detection material due to their long carrier diffusion length and lifetime, high absorption coefficient, and flexible manufacturing process. Compared with polycrystalline structures, single crystal perovskites improve the performance of optoelectronic devices due to their low defect state density, better photoelectric characteristics, and chemical ***, we review the recent progress of single crystal perovskite X-ray detectors. First, we briefly introduced the basic concepts, detection mechanisms, figure of merits of perovskite X-ray detectors, and the preparation methods of single crystal perovskites. Then, we summarized the significant advancements in single crystal perovskite X-ray detectors in recent times. Finally, we discussed the critical challenges and some practicable solutions for developing high-performance X-ray detectors.

关键词： single crystal perovskites carrier transport radiation detection X-ray detectors X-ray imaging

Compressive property and energy absorption characteristic of interconnected porous Mg-zn-Y alloys with adjusting Y addition

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Magnesium and Alloys 2024年第1期12卷 171-185页

作者： J.A.liu S.J.liu B.wang w.B.Sun X.J.liu z.w.Han College of Materials Science and Engineering Key Laboratory of Automobile Materials(Ministry of Education)Jilin UniversityChangchun 130022PR China Key laboratory of Bionic Engineering(Ministry of Education) College of Biological and Agricultural EngineeringJilin UniversityChangchun130022PR China weihai Institute for Bionics-Jilin University Weihai 264205PR China

In this study,interconnected porous Mg-2zn-xY alloys with different phase compositions were prepared by various Y additions(x=0.4,3,and 6 wt.%)to adjust the compressive properties and energy absorption *** characterization methods were then applied to identify the microstructure of the porous Mg-zn-Y and describe the details of the second *** tests were performed at room temperature(RT),200℃,and 300℃to study the impact of the Y addition and testing temperature on the compressive properties of the porous *** experimental results showed that a high Y content promotes a microstructure refinement and increases the volume fraction of the second *** the Y content increases,different Mg-zn-Y ternary phases appear:I-phase(Mg_(3)zn_(6)Y),w-phase(Mg_(3)zn_(3)Y_(2)),and lPSO phase(Mg_(12)znY).when the Y content ranges between 0.4%and 6%,the compressive strength increases from 6.30MPa to 9.23 MPa,and the energy absorption capacity increases from 7.33 MJ/m^(3)to 10.97 MJ/m^(3)at RT,which is mainly attributed to the phase composition and volume fraction of the second ***,the average energy absorption efficiency is independent of the Y *** addition,the compressive deformation behaviors of the porous Mg-zn-Y are altered by the testing *** compressive strength and energy absorption capacity of the porous Mg-zn-Y decrease due to the softening effect of the high temperature on the *** deformation behaviors at different temperatures are finally observed to reflect the failure mechanisms of the struts.

关键词： Porous magnesium Rare earth elements Microstructure Compressive behavior Energy absorption characteristic

维普期刊数据库

Spatiotemporal variations of parameters of internal solitary waves in the northern South China Sea

在线全文

学校读者我要写书评

暂无评论

Journal of Oceanology and limnology 2024年第2期42卷 421-438页

作者： Yu’ang lIU Yifei JIang Xiaojiang zHang zhiyuan wang Yu CAO Huizan wang College of Meteorology and Oceanography National University of Defense TechnologyChangsha 410000China

The dynamic parameters for internal solitary waves(ISws)derived from the extended Korteweg-de Vries(eKdV)equation play an important role in the understanding and prediction of *** spatiotemporal variations of the dynamic parameters of the ISws in the northern South China Sea(SCS)were studied based on the reanalysis of long-term temperature and salinity *** results for spectrum analysis show that there are definite geographical differences for the periodic variation of the parameters:in shallow water,all parameters vary with a wave period of one year,while in deep water wave components of the parameters at other frequencies *** wavelet analysis,the wavelet power spectral densities in deep water exhibited an inter-annual variation *** example,the wave component of the dispersion coefficient with a wave period of about half a year reached its power peak once every two *** on previous work,this inter-annual variation pattern was deduced to be caused by dynamic *** further work on the regulatory mechanisms,empirical orthogonal function(EOF)decomposition was *** was found that the modes of the dispersion coefficient have different geographical distributions,explaining the reason why the wave components in different frequencies appeared in different *** numerical simulation results confirm that the variations in the parameters of the ISws derived from the eKdV equation could affect the waveforms significantly because of changes in the polarity of the ***,the periodic variations of the dynamic parameters are related to the geographical location because of dynamic processes operating.

关键词： internal solitary waves(ISws) dynamic parameters eKdV equation spatiotemporal variation polarity empirical orthogonal function(EOF)decomposition

维普期刊数据库

A multi-sensor appiproach to calving detection

在线全文

学校读者我要写书评

暂无评论

Information Processing in Agriculture 2024年第1期11卷 45-64页

作者： Anita z.Chang David l.Swain Mark G.Trotter Institute for Future Farming Systems School of HealthMedicaland Applied SciencesCentral Queensland UniversityRockhamptonQueensland 4700Australia

The advent of remote livestock monitoring systems provides numerous possibilities for improving on-farm productivity,efficiency,and *** potential application for these systems is for the detection of calving *** study describes the integration of data from multiple sensor sources,including accelerometers,global navigation satellite systems(GNsS),an accelerometer-derived rumination algorithm,a walk-over-weigh unit,and a weather station for parturition detection using a support vector machine *** best performing model utilised data from GNsS,the ruminating algorithm,and weather stations to achieve 98.6%accuracy,with 88.5%sensitivity and 100%*** topranking features of this model were primarily GNSS *** study provides an overview as to how various sensor systems could be integrated on-farm to maximise calving detection for improved production and welfare outcomes.

关键词： Accelerometer GNSS GPS Rumination Sensor wOw

SCIRD: Revealing Infection of Malicious Software in Edge Computing-Enabled IoT Networks

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2024年第5期79卷 2743-2769页

作者： Jiehao Ye wen Cheng Xiaolong liu wenyi zhu Xuan’ang wu Shigen Shen School of Information Engineering Huzhou UniversityHuzhou313000China

The Internet of Things(IoT)has characteristics such as node mobility,node heterogeneity,link heterogeneity,and topology *** the face of the IoT characteristics and the explosive growth of IoT nodes,which brings about large-scale data processing requirements,edge computing architecture has become an emerging network architecture to support IoT applications due to its ability to provide powerful computing capabilities and good service ***,the defense mechanism of Edge Computing-enabled IoT Nodes(ECIoTNs)is still weak due to their limited resources,so that they are susceptible to malicious software spread,which can compromise data confidentiality and network service *** this situation,we put forward an epidemiology-based susceptible-curb-infectious-removed-dead(SCIRD)***,we analyze the dynamics of ECIoTNs with different infection levels under different initial conditions to obtain the dynamic differential ***,we establish the presence of equilibrium states in the SCIRD ***,we conduct an analysis of the model’s stability and examine the conditions under which malicious software will either spread or disappear within Edge Computing-enabled IoT(ECIoT)***,we validate the efficacy and superiority of the SCIRD model through MATlAB *** research findings offer a theoretical foundation for suppressing the propagation of malicious software in ECIoT *** experimental results indicate that the theoretical SCIRD model has instructive significance,deeply revealing the principles of malicious software propagation in ECIoT *** study solves a challenging security problem of ECIoT networks by determining the malicious software propagation threshold,which lays the foundation for buildingmore secure and reliable ECIoT networks.

关键词： Edge computing Internet of Things malicious software propagation model heterogeneity

QBIoT:A Quantum Blockchain Framework for IoT with an Improved Proof-of-Authority Consensus Algorithm and a Public-Key Quantum Signature

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2024年第7期80卷 1727-1751页

作者： ang liu Qing zhang Shengwei Xu Huamin Feng Xiu-bo Chen wen liu Network and Information Management Division Beijing Electronic Science and Technology InstituteBeijing100070China Department of Cyberspace Security Beijing Electronic Science and Technology InstituteBeijing100070China Information Security Institute Beijing Electronic Science and Technology InstituteBeijing100070China General Office Beijing Electronic Science and Technology InstituteBeijing100070China Information Security Center State Key Laboratory of Networking and Switching TechnologyBeijing University of Posts and TelecommunicationsBeijing100876China

The Internet of Things(IoT)is a network system that connects physical devices through the Internet,allowing them to ***,IoT has become an integral part of our lives,offering convenience and smart ***,the growing number of IoT devices has brought about a corresponding increase in cybersecurity threats,such as device vulnerabilities,data privacy concerns,and network *** blockchain technology with IoT has proven to be a promising approach to enhance IoT ***,the emergence of quantum computing poses a significant challenge to the security of traditional classical cryptography used in blockchain,potentially exposing it to quantum *** support the growth of the IoT industry,mitigate quantum threats,and safeguard IoT data,this study proposes a robust blockchain solution for IoT that incorporates both classical and post-quantum security ***,we present the Quantum-Enhanced Blockchain Architecture for IoT(QBIoT)to ensure secure data sharing and integrity ***,we propose an improved Proof of Authority consensus algorithm called“Proof of Authority with Random Election”(PoARE),implemented within QBIoT for leader selection and new block ***,we develop a publickey quantum signature protocol for transaction verification in the ***,a comprehensive security analysis of QBIoT demonstrates its resilience against cyber threats from both classical and quantum *** summary,this research introduces an innovative quantum-enhanced blockchain solution to address quantum security concernswithin the realmof *** proposedQBIoT framework contributes to the ongoing development of quantum blockchain technology and offers valuable insights for future research on IoT security.

关键词： IoT quantum blockchain public-key quantum signature quantum hash function

Microstructure evolution and shape memory behaviors of Ni_(47)Ti_(44)Nb_(9)alloy subjected to multistep thermomechanical loading with different prestrain levels

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2024年第4期171卷 80-93页

作者： Y.H.zhang H.li z.w.Yang X.liu Q.F.Gu State Key laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an 710072China Shaanxi Key laboratory of High-Performance Precision Forming Technology and Equipment Northwestern Polytechnical UniversityXi’an 710072China

Ni_(47)Ti_(44)Nb_(9)shape memory alloy(SMA)is a promising material in the aerospace field due to its wide transformation *** application of shape memory effect depends on multistep thermomechan-ical loading,viz.,low-temperature deformation and subsequent heating to ***-temperature deformation prestrain plays a pivotal role in shape memory properties tailoring of SMA ***,microstructure evolution and deformation mechanisms of Ni_(47)Ti_(44)Nb_(9)SMA subjected to vari-ous prestrain levels are still *** this end,microstructure evolution and shape memory behaviors of Ni_(47)Ti_(44)Nb_(9)alloy subjected to multistep thermomechanical loading with prestrain levels of 8%-16%at-28℃(M_(s)+30℃)were *** results demonstrate that the stress-strain curve of the specimen exhibits four distinct stages at a maximal prestrain of 16%.whereas stageⅡand stageⅢend at prestrains of∼8%and∼12%,*** stageⅡ,the stress-induced martensitic transformation is accompanied by the dislocation slip of the NiTi matrix andβ-Nb *** stageⅢ,in addition to the higher density of dislocations and further growth of stress-induced martensite variants(SIMVs),(001)compound twins are introduced as a result of the(001)deformation twinning in stress-induced ***{20-1}martensite twins are gradually introduced in stageⅣ.Correspondingly,after subsequent unloading and heating,a higher density of{114}austenite twins form in the specimen with a larger prestrain of 16%.with increasing prestrain from 8%to 16%,the recoverable strainε_(re)^(T)upon heating increases first and then ***ε_(re)^(T)obtains a maximum of 7.03%at 10%prestrain and de-creases to 6.17%at 16%*** increase ofε_(re)^(T)can be attributed to the formation of new SIMVs,the further growth of existing SIMVs,and the recoverable(001)compound *** the decrease ofε_(re)^(T)is mainly associated with the irrecoverable strain by{20−1}martensite *** effe

关键词： Ni_(47)Ti_(44)Nb_(9)shape memory alloy wide transformation hysteresis Thermomechanical loading Microstructure evolution Shape memory behaviors Stress-induced martensitic transformation Deformation twinning

Interface catalytic reduction of alumina by nickle for the aluminum nanowire growth: Dynamics observed by in situ TEM

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2024年第3期17卷 1225-1231页

作者： zichun wang Dan wang ang li lizhuo wang Xiaodong Han Yijiao Jiang Jianfeng Chen Jun Huang Beijing Advanced Innovation Center for Soft Matter Science and Engineering State Key Laboratory of Organic–Inorganic CompositesBeijing University of Chemical TechnologyBeijing 100029China laboratory for Catalysis Engineering School of Chemical and Biomolecular EngineeringThe University of SydneyNew South Wales 2006Australia Beijing Key laboratory of Microstructure and Property of Advanced Materials Beijing University of TechnologyBeijing 100024China Department of Engineering Macquarie UniversitySydneyNew South Wales 2109Australia

Metal nanowires show promise in a broad range of applications and can be fabricated via a number of methods,such as vapor–liquid–solid process and template-based ***,the synthesis of Al nanowires(Nws)is still challenging from the stable alumina *** this work,the Ni-catalyzed fabrication of Al Nws has been realized using various Al_(2)O_(3) *** growth dynamics of Al Nws on Ni/Al_(2)O_(3) was studied using in situ transmission electron microscopy(TEM).The effect of alumina structures,compositions,and growth temperature were *** growth of Al Nws correlates with the Na addition to the alumina *** no eutectic mixture of nickel aluminide was formed,a mechanism of Ni-catalyzed reduction of Al_(2)O_(3) for Al Nws growth has been proposed instead of the vapor–liquid–solid *** key insights reported here are not restricted to Ni-catalyzed Al Nws growth but can be extended to understanding the dynamic change and catalytic performance of Ni/Al_(2)O_(3) under working conditions.

关键词： in situ transmission electron microscopy(TEM) Al nanowires alumina reduction nanowire growth