检索结果-南通市图书馆

Journal of Materials Science & Technology 2013年第11期29卷 1018-1024页

作者： shufeng li Hisashi Imai Katsuyoshi Kondoh Faculty of Materials Science and Engineering Xi'an University of Technology Joining and Welding Research Institute Osaka University

The effect of titanium addition on the microstructure and mechanical properties of brass Cu4OZn has been studied via the powder metallurgy （P/M） route. The water-atomized Cu4OZn-1.0 wt% Ti alloy powder was consolidated at different temperatures in the range of 400-600℃ using spark plasma sintering （SPS） and hot extrusion subsequently. Results show that the super-saturated solid solution titanium element in rapidly cooled brass Cu4OZn powder created high chemical potential for a precipitate reaction, showing significant grain refinement effects on the consolidated Cu4OZn matrix. Consequently, excellent mechanical properties were obtained by precipitation hardening and work hardening after sintering and extrusion, with yield strength of 390 MPa, ultimate tensile strength of 617 MPa, and Vickers micro-hardness of 192 HV, which are 28.7%, 23.4%, and 23.9% higher values than those of extruded Cu4OZn brass, respectively.

关键词： Brass Spark plasma sintering Extrusion Microstructure Mechanical property Precipitation Phase transformation

Research on encoding and decoding of non-binary polar codes over GF(2m)

在线全文

学校读者我要写书评

暂无评论

Digital Communications and Networks 2022年第3期8卷 359-372页

作者： shufeng li Mingyu Cai Robert Edwards Yao Sun libiao Jin The State Key Laboratory of Media Convergence and Communication School of Information and EngineeringCommunication University of ChinaBeijing100024China The Wolfson School of Mechanical Electrical and Manufacturing Engineering Loughborough UniversityLeicestershireLE113TEUK James Watt School of Engineering University of GlasgowG128QQScotlandUK

Binary Polar Codes (BPCs) have advantages of high-efficiency and capacity-achieving but suffer from large latency due to the Successive-Cancellation list (SCL) decoding. Non-Binary Polar Codes (NBPCs) have been investigated to obtain the performance gains and reduce latency under the implementation of parallel architectures for multi-bit decoding. However, most of the existing works only focus on the Reed-Solomon matrix-based NBPCs and the probability domain-based non-binary polar decoding, which lack flexible structure and have a large computation amount in the decoding process, while little attention has been paid to general non-binary kernel-based NBPCs and Log-likelihood Ratio (LLR) based decoding methods. In this paper, we consider a scheme of NBPCs with a general structure over GF(2m). Specifically, we pursue a detailed Monte-Carlo simulation implementation to determine the construction for proposed NBPCs. For non-binary polar decoding, an SCL decoding based on LLRs is proposed for NBPCs, which can be implemented with non-binary kernels of arbitrary size. Moreover, we propose a Perfect Polarization-Based SCL (PPB-SCL) algorithm based on LLRs to reduce decoding complexity by deriving a new update function of path metric for NBPCs and eliminating the path splitting process at perfect polarized (i.e., highly reliable) positions. Simulation results show that the bit error rate of the proposed NBPCs significantly outperforms that of BPCs. In addition, the proposed PPB-SCL decoding obtains about a 40% complexity reduction of SCL decoding for NBPCs.

关键词： Non-binary polar code Log-likelihood ratio Successive-cancellation list Perfect polarization based-SCL Decoding complexity

Late Eocene sclerophyllous oak from Markam Basin, Tibet, and its biogeographic implications

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2021年第11期64卷 1969-1981页

作者： linlin CHEN Weiyudong DENG Tao SU shufeng li Zhekun ZHOU Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical GardenChinese Academy of SciencesMengla 666303China Key Laboratory of Biodiversity and Biogeography Kunming Institute of BotanyChinese Academy of SciencesKunming 650204China University of Chinese Academy of Sciences Beijing 100049China Center of Plant Ecology Core Botanical GardensChinese Academy of SciencesMengla 666303China

Sclerophyllous evergreen broad-leaved forests,mainly made up of sclerophyllous oak,Quercus section Heterobalanus(Øerst.)Menitsky,Fagaceae,represent the most typical forest type in the Hengduan *** distribution pattern is closely related to the growth and formation of the Qinghai-Tibetan Plateau(QTP).The oldest fossil record of Quercus *** so far discovered is from the middle Miocene of the Gazhacun Formation in Namling County,southern ***,our recent discovery of leaf fossils from the upper Eocene of Lawula Formation in Markam Basin,southeastern Tibet,illustrates that their origin is nearly 20 Myr older than previously *** integrating the results from geometric morphometrics,geographical range expansion,and ecological niche shifts of this section in what is now the QTP and the Hengduan Mountains,we infer that the leaves of Quercus *** were already adapted to cool and dry conditions in some local regions no later than in the late ***,with the growth of the QTP and late Cenozoic global cooling,the expansion of cooler and drier habitats benefited the spread and development of this section and their leaves exhibited morphological stasis through stabilizing *** on published fossil records and recent discoveries,we argue that Quercus *** appeared in the subtropical evergreen and deciduous broad-leaved mixed forests of the southeastern margin of what is now the QTP no later than in the late *** taxa spread westwards along the Gangdese Mountains and later the Himalaya,and others spread eastwards and southeastwards,gradually becoming a dominant group of species in the Hengduan *** dispersal route is contrary to the previous“northwards hypothesis”of this section,and further supports the hypothesis of an East Asian origin for Quercus section Ilex Loudon.

关键词： Quercus section Heterobalanus Cenozoic Qinghai-Tibetan Plateau Geometric Morphometrics Morphological Evolutionary Stasis Biogeography

Microstructure and mechanical properties of ZrO_2(Y_2O_3)-Al_2O_3 nanocomposites prepared by spark plasma sintering

在线全文

学校读者我要写书评

暂无评论

Particuology 2012年第3期10卷 345-351页

作者： shufeng li Hiroshi Izui Michiharu Okano Weihua Zhang Taku Watanabe College of Science and Technology Nihon University7-24-1NarashinodaiFunabashiChiba 274-8501Japan College of Science and Technology Nihon University1-8-14KandasurugadaiChiyoda.Tokyo 101-8308Japan College of Materials Science and Technology Xi'an University of Technology5 SouthJinhua RoadXi'anShaanxi 710048China

Zirconia （yttria）-alumina ceramic nanocomposites were fabricated from different powders by spark plasma sintering （SPS）. One powder was a commercially available nanocomposite powder TZP-3Y2OA, consisting of 3 mol% yttria-stabilized zirconia （3-YSZ） reinforced with 20wt% alumina, and the other, used as a comparison, was a conventional mechanically mixed powder 3YSZ-2OA, a blend made of 3 mol% yttria-stabilized zirconia powder ZrO2 （3Y） and 20 wt% ,x-alumina powder. The effect of the sintering temperature on the densification, the sintering behavior, the mechanical properties and the microstructure of the composites was investigated. The results showed that the density increased with increasing sintering temperature, and thus, the mechanical properties were strengthened because of the increased densification. The nanocomposite powder TZP-3Y20A was easily sintered, and good mechanical properties were achieved as compared with the powder from the conventional mechanically mixed method, the maximum flexural strength and fracture toughness of which were 967 MPa and 5.27 MPa m 1/2, respectively.

关键词： Zirconia-aluminaNanocompositeSpark plasma sintering (SPS)Mechanical propertiesMicrohardnessFracture toughnessDensification

AWG-based large dynamic range fiber Bragg grating interrogation system

在线全文

学校读者我要写书评

暂无评论

Optoelectronics Letters 2024年第3期20卷 129-134页

作者： li shufeng YUAN Pei li Ke li Ting ZHU lianqing Key Laboratory of the Ministry of Education for Optoelectronic Measurement Technology and Instrument Beijing Information Science&Technology UniversityBeijing 100192China Beijing Laboratory of Optical Fiber Sensing and System Beijing Information Science&Technology UniversityBeijing 100016China

Arrayed waveguide gratings(AWGs) are extensively employed in fiber Bragg grating(FBG) interrogation systems due to their compact size, lightweight nature, and excellent interrogation performance. The resolution and total measurement range of AWG-based FBG interrogation systems are constrained by the output properties of AWG. We proposed an AWG-based large dynamic range interrogation system. The temperature dependence of AWG is exploited to achieve continuous interrogation. The test results show that the interrogation system has a dynamic range of 28.67 nm, an interrogation accuracy better than 25 pm, and a wavelength resolution of 6 pm.

关键词： fiber waveguide AWG

Pliocene flora and paleoenvironment of Zanda Basin, Tibet, China

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2020年第2期63卷 212-223页

作者： Jian HUANG Tao SU shufeng li Feixiang WU Tao DENG Zhekun ZHOU CAS Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical GardenChinese Academy of SciencesXishuangbanna 666303China University of Chinese Academy of Sciences Beijing 100049China Kunming Institute of Botany Chinese Academy of SciencesKunming 650201China Institute of Vertebrate Paleontology and Paleoanthropology Chinese Academy of SciencesBeijing 100044China Center for Excellence in life and Paleoenvironment Chinese Academy of SciencesBeijing 100044China

This paper describes a plant megafossil assemblage from the Pliocene strata of Xiangzi, Zanda Basin in the western Qinghai-Tibet Plateau. Twenty-one species belonging to 12 genera and 10 families were identified. Studies show that the Pliocene vegetation in Zanda Basin was mostly deciduous shrub composed of Cotoneaster, Spiraea, Caragana, Hippophae,Rhododendron, Potentilla fruticosa, etc. Leaf sizes of these taxa were generally small. Paleoclimate reconstruction using Coexistence Analysis and CLAMP showed that this area had higher temperature and precipitation in the Pliocene than today, and distinct seasonal precipitation variability was established. The reconstructed paleoelevation of Zanda Basin in the Pliocene was similar to modern times. In the context of central Asian aridification, the gradual drought in the area beginning in the late Cenozoic caused vegetation to transition from shrub to desert, and the flora composition also changed.

关键词： Qinghai-Tibet Plateau Cenozoic Pliocene Plant fossils Paleovegetation Paleoclimate Environmental change

Interface regulation strategy of Al-CNTs composite induced by Al-Si eutectic reaction and its strengthening mechanism

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2023年第20期151卷 1-9页

作者： Xin Zhang Xin li Lei liu Bo li Xiaodong Hou Deng Pan lina Gao shufeng li School of Materials Science and Engineering Xi’an University of TechnologyXi’an 710048China Xi’an Key Laboratory of Advanced Powder Metallurgy Materials and New Technology Xi’an University of TechnologyXi’an 710048China Centre of Excellence for Advanced Materials Songshan LakeDongguan 523808China

Carbon nanotubes(CNTs)reinforced aluminum matrix composites(AMCs)show broad application prospects in the fields of aerospace and transportation because of their lightweight,high specific strength and specific modulus.A new alloying strategy in this study is proposed to regulate its weak intrinsic interface and uncontrollable interfacial *** results show that Si element could hinder the dissolution and diffusion of carbon atoms in Al matrix,inhibiting Al-CNTs interface *** refinement and dislocation increment induced by the reinforcements promote the contributions to the strength of *** wettability and interface bonding of Al-CNTs could be effectively improved by Al/Si/CNTs composite interface,the formed discontinuous strong interface is advantageous to coordinate the plastic deformation of *** particles can also firmly fix CNTs through pinning effect during deformation,which leads to a better load ***,the tensile strength of Al-5Si-0.5CNTs composite can be enhanced up to 391 MPa while maintaining an acceptable plasticity of 7.5%.It brings the strengthening effect of CNTs into full play in AMCs and achieves the strengthening effect of 1+1>2 under the comprehensive effect of grain refinement strengthening,dislocation strengthening,dispersion strengthening of Si particles and load transfer to CNTs。

关键词： Aluminum matrix composites Interface regulation Microstructure Strengthening effect Mechanical properties

Vegetation changes across the Eocene-Oligocene transition:Global signals *** development

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Earth Sciences 2024年第9期67卷 2937-2952页

作者： Mengxiao WU Lutz KUNZMANN shufeng li Vasilis TEODORIDIS Zhekun ZHOU Tao SU CAS Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical GardenChinese Academy of SciencesMengla 666303China Senckenberg Natural History Collections Dresden Konigsbrücker LandstraBe 159Dresden 01109Germany Department of Biology and Environmental Studies Faculty of EducationCharles UniversityMagdalény Rettigové411639 Prague 1Czech Republic State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Chengdu University of TechnologyChengdu 610059China Institute of Sedimentary Geology Chengdu University of TechnologyChengdu 610059China

The Eocene-Oligocene transition(EOT)marked a rapid global cooling event,often considered as the beginning of the modern icehouse *** by various factors,including tectonic activity and paleogeographic settings,the terrestrial records indicate a diverse response of fauna and vegetation to this global *** examined nine macrofossil assemblages from seven fossil localities on the southeastern margin of the Tibetan Plateau and from the mid-latitudinal Europe ranging from the latest Bartonian and Priabonian(37.71-33.9 Ma)to the Rupelian(33.9-27.82 Ma).Our aims were to trace and compare the vegetation history of both regions in the late Eocene and early *** results show that both regions experienced changes in vegetation composition in response to climate change,characterized by a decrease in the percentages of broad-leaved evergreen elements and distinctive changes in general vegetation types.A general change in the overall vegetation type from subtropical broad-leaved evergreen forests in the late Eocene to temperate broad-leaved mixed deciduous evergreen forests,or mixed mesophytic forests,in the early Oligocene is recognized in both *** results indicate a clear change in leaf architecture,leaf margin states,and secondary venation types in the mid-latitudinal Europe,while the results from the southeastern margin of the Tibetan Plateau show a distinct reduction in leaf *** data suggest that both global and regional factors played key roles in shaping the vegetation in the two regions.

关键词： Eocene-Oligocene transition Plant fossil Paleoclimate Leaf architecture Biodiversity

同方期刊数据库

An Improved SCMA Detector Based on ResNet Perception Fusion

在线全文

学校读者我要写书评

暂无评论

China Communications 2024年第12期21卷 152-165页

作者： Jin libiao Feng Yuwei li shufeng Sun Yao Yin Fangfang State Key Laboratory of Media Convergence and Communication Communication University of ChinaBeijing 100024China James Watt School of Engineering University of GlasgowScotland G128QQUK

The received signals used for sparse code multiple access(SCMA)detection are usually contaminated with noise during transmission,which exposes an issue of low decoding *** address this issue,a novel detector based on a residual network(ResNet)perception fusion framework(RSMPA)is proposed for uplink SCMA system in this ***,we first formulate a joint design of perception system and traditional communication module.A perception framework based on ResNet is applied to cancel the noise component and enhance the communication system *** ResNet model is designed and trained using the clean and noisy SCMA signal,*** on the denoised output,information iteration process is executed for multi-user *** results indicate that the perception model achieves an excellent denoising performance for SCMA system and the proposed scheme outperforms the conventional detection algorithms in terms of SER performance.

关键词： perception fusion ResNet SCMA signal detection

Glacial expansion of cold-tolerant species in low latitudes: megafossil evidence and species distribution modelling

在线全文

学校读者我要写书评

暂无评论

National Science Review 2023年第4期10卷 13-15页

作者： Luliang Huang shufeng li Weiye Huang Helanlin Xiang Jianhua Jin Alexei A.Oskolski State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources School of Life Sciences/School of Ecology Sun Yat-sen University State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences CAS Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical Garden Chinese Academy of Sciences Department of Botany and Plant Biotechnology University of Johannesburg Botanical Museum Komarov Botanical Institute of the Russian Academy of Sciences

The Pleistocene was a time of repeated glaciations that severely affected the land biota over large areas of Eurasia and North America. Drastic climatic fluctuations during the Pleistocene drove largescale extinctions, migrations and diversification in plant and animal *** dramatic processes had a strong impact on the distribution of modern flora and fauna.

关键词：