检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

乙烯裂解炉配管设计

石油化工设计 2025年第1期42卷 54-58,I0004页

作者：沈圳张军文中国石化工程建设有限公司北京100101

介绍了乙烯装置裂解炉单元构架与炉前管廊配管布置的新模式,结合国内某乙烯装置裂解炉单元20万t/a炉管设计经验和实例,从构架与管廊功能性的角度阐述了关于平台设置、阀组布置重新分配的设计过程。并就裂解气大阀的管道设计及管廊跨距... 详细信息

介绍了乙烯装置裂解炉单元构架与炉前管廊配管布置的新模式,结合国内某乙烯装置裂解炉单元20万t/a炉管设计经验和实例,从构架与管廊功能性的角度阐述了关于平台设置、阀组布置重新分配的设计过程。并就裂解气大阀的管道设计及管廊跨距给出了新方案,同时从应力角度论证了此种布置方案的可行性。从平面布置角度探讨了通过缩小管廊跨距减少裂解炉单元占地的可行性。

关键词：乙烯裂解炉裂解气大阀平竖面布置

Constellation shaping optimization for nonlinearity mitigation in CAP UVLC system

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(Information Sciences) 2023年第9期66卷 274-290页

作者： Junlian JIA junwen zhang Nan CHI Key Laboratory for Information Science of Electromagnetic Waves(MoE) Fudan University Shanghai Engineering Research Center of Low-Earth-Orbit Satellite Communication and Applications Shanghai Collaborative Innovation Center of Low-Earth-Orbit Satellite Communication Technology Peng Cheng Laboratory

In the sixth-generation communication(6G), wireless communication will cover not only conventional air links but also underwater links. Underwater visible light communication(UVLC) is an expected technique that achieves a high data rate. However, UVLC systems suffer from severe nonlinear distortions for the high-power transmitting, thus nonlinear compensation is vital to the system. Carrier-less amplitude and phase(CAP) modulation is a promising modulation, especially for the scenes with high nonlinear *** this paper, for the first time, we proposed a constellation optimization method for the UVLC system supporting the native artificial intelligence in 6G. The proposed framework, based on the complete process of the CAP modulation and demodulation, fulfills an end-to-end learning scheme with a neural network at the transmitter side and the conventional demodulation processes at the receiver side. A loss function is further designed to support the training without needing a fixed signal-to-noise ratio(SNR). The proposed framework is simulated and then tested in an experiment. In a 1.2-meter nonlinear UVLC channel, compared with 1.5 Gbit/s supported by the conventional grid encoding, the proposed method brings an extra 200 Mbit/s data rate.

关键词： underwater visible light communication nonlinearity compensation constellation optimization

Characterization and evaluation of brittleness of deep bedded sandstone from the perspective of the whole life-cycle evolution process

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2023年第4期33卷 481-502页

作者： Zhixiang Song junwen zhang Yang zhang Xukai Dong Shanyong Wang School of Energy and Mining Engineering China University of Mining and Technology-BeijingBeijing 100083China Priority Research Centre for Geotechnical Science&Engineering The University of NewcastleCallaghan NSW 2308Australia

The quantitative determination and evaluation of rock brittleness are crucial for the estimation of excavation efficiency and the improvement of hydraulic fracturing ***,a“three-stage”triaxial loading and unloading stress path is designed and ***,six brittleness indices are *** addition,the evolution characteristics of the six brittleness indices selected are characterized based on the bedding effect and the effect of confining ***,the entropy weight method(EWM)is introduced to assign weight to the six brittleness indices,and the comprehensive brittleness index Bcis defined and ***,the new brittleness classification standard is determined,and the brittleness differences between the two stress paths are ***,compared with the previous evaluation methods,the rationality of the proposed comprehensive brittleness index Bcis also *** results indicate that the proposed brittleness index Bccan reflect the brittle characteristics of deep bedded sandstone from the perspective of the whole life-cycle evolution ***,the method proposed seems to offer reliable evaluations of the brittleness of deep bedded sandstone in deep engineering practices,although further validation is necessary.

关键词： Brittleness Deep bedded sandstone Whole life-cycle evolution process Bedding effect Effect of confining pressure Entropy weight method

Geochemical behavior of lithium isotopes in a small mountainous river of the Tibetan Plateau:A case study from Niyang River

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2023年第8期66卷 1853-1864页

作者： junwen zhang Yani YAN Zhiqi ZHAO Congqiang LIU School of Earth Science and Resources Chang’an UniversityXi’an 710054China Institute of Surface-Earth System Science Tianjin UniversityTianjin 300072China

Lithium(L_(i))and its isotopes are potential tracers of silicate weathering in river ***,the relationship between the Li isotopic composition(δ~7Li)in rivers and silicate weathering intensity remains *** study analyzed the Li concentration and isotopic composition in river waters from the Niyang River,southern Tibetan *** results show that these samples have significantly variable Li concentrations(0.31–7.4μg/L)andδ~7Li values(+7.0–+20.7‰,n=28),and highδ~7Li values are found in several *** indicate that dissolved Li in river water is predominantly derived from silicate weathering and geothermal *** the exception of certain tributaries,geothermal water contributes 68%to 85%of the dissolved *** waters have lowδ~7Li values(-0.9–+2.9‰)in the Tibetan *** in the proportional contribution of dissolved Li in river samples from silicate weathering and geothermal water may be the main reason for the spatiotemporal variation in riverineδ~7Li *** samples have higherδ~7Li values when the dissolved Li in the water samples is mainly derived from silicate weathering contributions,and lower values when the contribution from geothermal waters is ***,the interaction of dissolved Li from geothermal water with secondary minerals results in Li isotopic fractionation,which may contribute to variations in river waterδ~*** is accepted that the lower weathering intensity in orogenic(or mountainous)belts compared to floodplains is the main controlling factor for lowerδ~7Li values in the *** study indicates that geothermal water input may cover the Li isotope signal of silicate weathering in river water,which in turn,affects the accurate understanding of the relationship between riverineδ~7Li values and the silicate weathering ***,whether the lowerδ~7Li values of river waters in hydrothermal-rich orogenic belts are mainly controlled by the regional weathering intensi

关键词： Lithium isotopes Silicate weathering Hot springs Tibetan Plateau

Advances in brain tumor therapy:from molecular diagnostics to novel treatments

在线全文

学校读者我要写书评

暂无评论

Science China(Life Sciences) 2024年第12期67卷 2771-2773页

作者： junwen zhang Ran Mu Fusheng Liu Brain Tumor Research Center Beijing Neurosurgical InstituteCapital Medical UniversityBeijing 100070China Department of Neurosurgery Beijing Tiantan HospitalCapital Medical UniversityBeijing 100070China

With the rapid increase in incidence and mortality,brain tumors have become a major social,economic,and public health problem *** to the latest report from the International Agency for Research on Cancer(IARC),there are approximately 320,000 new cases and 250,000 deaths from brain and central nervous system(CNS)tumors each *** incidence and mortality rates rank 19th and 12th among all cancers(Bray et al.,2024),respectively,and are particularly prevalent in East Asia,Western Europe,and South Asia.

关键词： mortality Cancer

First Record of Petalodus Owen,1840(Chondrichthyes,Petalodontidae)in the Lower Permian(Cisuralian)of China

在线全文

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 2021年第4期95卷 1057-1064页

作者： GAI Zhikun BAI Zhijun LIN Xianghong MENG Xinyuan zhang junwen Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences Institute of Vertebrate Paleontology and PaleoanthropologyChinese Academy of SciencesBeijing 100044China CAS Center for Excellence in Life and Paleoenvironment Beijing 100044China University of Chinese Academy of Sciences Beijing 100039China Planning and Natural Resources Bureau of Yangquan YangquanShanxi 045000China Second Institute of Geological and Engineering Exploration of Shanxi YangquanShanxi 045000China

The Petalodontiformes are a small intriguing group of Permo–Carboniferous *** is the longest known petalodont genus generally considered representative of the *** first definite fossil record of seven well-preserved Petalodus teeth has been found in the Qianshi limestone in the Lower Permian(Cisuralian)middle–upper Taiyuan Formation in Yangquan City,Shanxi Province,North *** specimens are characterized by petal-shaped teeth with a spade-like crown,and a long,tongue-shaped root;the crown is circled with a band or cingulum composed of imbricated ridges at the *** seven teeth are assigned to the species *** because of their vertically narrow cingulum and much longer *** is a worldwide genus,with fossil localities mainly concentrated in the Laurussia *** occurrence of Petalodus teeth in Yangquan not only is the first fossil record in China,but also only the second record in *** Yangquan fossil site was part of the paleoequatorial North China Craton during the Early Permian,and was isolated from Laurusia and East Gondwana by the Paleo-Tethys *** successful dispersal of Petalodus from Laurusia to the North China Block along Paleo-Tethys may support the possibility that Petalodus taxa were active free-swimmers rather than bottom *** new finding increases the petalodont diversity in eastern Asia,and also sheds new light on the distribution and stratigraphic range.

关键词： vertebrate paleontology Petalodus Petalodontiformes Yangquan Taiyuan Formation Paleo-Tethys Ocean Asselian–Sakmarian Shanxi Province

Studying the performance of fully encapsulated rock bolts with modified structural elements

在线全文

学校读者我要写书评

暂无评论

International Journal of Coal Science & Technology 2021年第1期8卷 64-76页

作者： Jianhang Chen Hongbao Zhao Fulian He junwen zhang Kangming Tao School of Energy and Mining Engineering China University of Mining and Technology(Beijing)Beijing100083China Beijing Key Laboratory for Precise Mining of Intergrown Energy and Resources China University of Mining and Technology(Beijing)Beijing100083China

Numerical simulation is a useful tool in investigating the loading performance of rock *** cable structural elements(cableSELs)in FLAC3D are commonly adopted to simulate rock bolts to solve geotechnical *** this study,the bonding performance of the interface between the rock bolt and the grout material was simulated with a two-stage shearing coupling ***,the FISH language was used to incorporate this two-stage shear coupling model into FLAC3D to modify the current *** was performed between numerical and experimental results to confirm that the numerical approach can properly simulate the loading performance of rock *** on the modified cableSELs,the influence of the bolt diameter on the performance of rock bolts and the shear stress propagation along the interface between the bolt and the grout were *** simulation results indicated that the load transfer capacity of rock bolts rose with the rock bolt diameter *** the bolt diameter increasing,the performance of the rock bolting system was likely to change from the ductile behaviour to the brittle ***,after the rock bolt was loaded,the position where the maximum shear stress occurred was ***,with the continuous loading,it shifted from the rock bolt loaded end to the other end.

关键词： Fully encapsulated rock bolts Numerical simulation Structural elements Shear coupling model Interface shear strength

Recent progress on high-speed optical transmission

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

Digital Communications and Networks 2016年第2期2卷 65-76页

作者： Jianjun Yu junwen zhang Key Laboratory for Information Science of Electroma1netic Waves (EOM). Fudan University. Shanghai 200433. China ZTE (TX) Inc. Morristown NJ 07920 USA

The recently reported high spectral efficiency （SE） and high-baud-rate szgnal transmission are all Daseo on digital coherent optical communications and digital signal processing （DSP）. DSP simplifies the re- ception of advanced modulation formats and also enables the major electrical and optical impairments to be processed and compensated in the digital domain, at the transmitter or receiver side. In this paper, we summarize the research progress on high-speed signal generation and detection and also show the progress on DSP for high-speed signal detection. We also report the latest progress on multi-core and multi-mode multiplexing.

关键词： Coherent optical detectionModulation formatCapacityOptical fiber communication

Path planning based on sliding window and variant A* algorithm for quadruped robot

在线全文

学校读者我要写书评

暂无评论

High Technology Letters 2016年第3期22卷 334-342页

作者：张慧 Rong Xuewen Li Yibin Li Bin zhang junwen zhang Qin School of Control Science and Engineering Shandong University School of Electrical Engineering Jinan University

In order to improve the adaptability of the quadruped robot in complex environments,a path planning method based on sliding window and variant A* algorithm for quadruped robot is presented. To improve the path planning efficiency and robot security,an incremental A* search algorithm( IA*) and the A* algorithm having obstacle grids extending( EA*) are proposed respectively. The IA* algorithm firstly searches an optimal path based on A* algorithm,then a new route from the current path to the new goal projection is added to generate a suboptimum route incrementally. In comparison with traditional method solving path planning problem from scratch,the IA* enables the robot to plan path more efficiently. EA* extends the obstacle by means of increasing grid g-value,which makes the route far away from the obstacle and avoids blocking the narrow passage. To navigate the robot running smoothly,a quadratic B-spline interpolation is applied to smooth the *** results illustrate that the IA* algorithm can increase the re-planning efficiency more than 5 times and demonstrate the effectiveness of the EA* algorithm.

关键词： quadruped robot path planning sliding window A* algorithm