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Greedy Lattice Paths with General Weights

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Acta Mathematica Sinica,English Series 2024年第9期40卷 2213-2222页

作者： Yin shan chang An Qi ZHENG College of Mathematics Sichuan UniversityChengdu 610065P.R.China

Let{X_(v):v∈Z^(d)}be *** *** S(π)=Σ_(v∈π)X_(v)be the weight of a self-avoiding lattice pathπ.Let M_(n)=max{S(π):πhas length n and starts from the origin}.We are interested in the asymptotics of Mn as n→∞.This model is closely related to the first passage percolation when the weights{X_(v):v∈Z^(d)}are non-positive and it is closely related to the last passage percolation when the weights{X_(v):v∈Z^(d)}are *** general weights,this model could be viewed as an interpolation between first passage models and last passage ***,this model is also closely related to a variant of the position of right-most particles of branching random *** the two assumptions that∃α>0,E(X_(0)^(+))^(d)(log^(+)X_(0)^(+))^(d+α)0,E(X_(0)^(+))^(d)(log^(+)X_(0)^(+))^(d+α)<+∞and that E[(X_(0)^(−))^(4)]<+∞,we prove that M_(n)/n converges to the same constant M almost surely as n tends to infinity.

关键词： Last passage percolation first passage percolation greedy lattice path

New Siliceous Microfossils from the Terreneuvian Yanjiahe Formation,South China:The Possible Earliest Radiolarian Fossil Record

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Journal of Earth Science 2018年第4期29卷 912-919页

作者： shan chang Qinglai Feng Lei Zhang School of Earth Sciences China University of Geosciences State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences

Radiolarians form an important part of the planktonic realm in the ocean of Early Paleozoic, but their origin and evolutionary processes has long been enigmatic. The ancestral representatives of radiolarians have been considered to belong to the order Archaeospicularia, whose unquestionable fossil records were dated back to the Middle Cambrian. Here we report ？Blastulospongia and unnamed spherical radiolarians in the Terreneuvian from the Yanjiabe Formation in Hubei Province, South China. Blastulospongia is an enigmatic siliceous microfossil genus, with affinities proposed amongst the radiolarian, sphinetozoan-grade sponges and uncertain protists. As for the newly discovered unnamed radiolarians, morphologically they possess latticed shell, spherical shape and are all small in size. Our discoveries support the idea that spherical radiolarians is an ancient representative, whose origin and diversification was probably much earlier than generally accepted. The hypothesis that the oldest radiolarians belong to the order Archaeospicularia needs to be re-examined.

关键词： Cambrian radiolarian ?Blastulospongia silica-biomineralization

Augmentation quotients for complex representation rings of dihedral groups

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Frontiers of Mathematics in China 2012年第1期7卷 1-18页

作者： shan chang Hong CHEN Guoping TANG School of Mathematics Hefei University of Technology Hefei 230026 China School of Mathematical Sciences Soochow University Suzhou 215006 China School of Mathematical Sciences Graduate University of Chinese Academy of Sciences Beijing 100049 China

Denote by Dm the dihedral group of order 2m. Let R（Dm） be its complex representation ring, and let △（Dm） be its augmentation ideal. In this paper, we determine the isomorphism class of the n-th augmentation quoti... 详细信息

关键词： dihedral group representation augmentation quotient

Pulsed γ-ray properties of Crab pulsar in a retarded dipole with a current-induced magnetic field

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Research in Astronomy and Astrophysics 2015年第12期15卷 2229-2236页

作者： shan chang Li Zhang Xiang Li Department of Astronomy School of Physical Science and TechnologyKey Laboratory of Astroparticle Physics of Yunnan ProvinceYunnan University

Motivated by the Fermi observations of some γ-ray pulsars in which the phases of radio and γ-ray peaks are almost the same, we investigate the outer gap model in a retarded dipole with a current-induced magnetic field and apply it to explain pulsed γ-ray properties of the Crab pulsar. Our results show that the observed γ-ray energy-dependent light curves, which almost align with the radio light curve and phase averaged spectrum for the Crab pulsar, are reproduced well.

关键词： gamma rays: theory -- pulsars: general -- pulsars: individual (Crab) --stars: neutron

Electrospun nanofibers of poly(vinyl pyrrolidone)/Eu^(3+) and its photoluminescence properties

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Chinese Chemical Letters 2007年第4期18卷 465-468页

作者： shan shan Tang chang Lu Shao Shou Zhu Li Center for Advanced Optoelectronic Functional Materials Research Northeast Normal University Changchun 130024 PR China

Nanofibers of poly（vinyl pyrrolidone）（PVP）/Eu^3＋ with diameters of 300-900 nm were prepared by using sol-gel processing and electrospinning technique. The products were characterized by scanning electron microscope （SEM）, Fourier transform infrared spectroscopy （FT-IR）, and photoluminescence （PL）. The results indicated that, Eu^3＋ was successfully embedded in the onedimensional hybrid nanofibers, and the PVP/Eu^3＋ hybrid nanofibers had favorable photoluminescence properties.

关键词： Electrospinning Nanofibers PVP Eu^3+

Characteristics and Sources of Organic Matter from the Early Cambrian Niutitang Formtion and Its Preservation Environment in Guizhou

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Journal of Earth Science 2022年第4期33卷 933-944页

作者： Hong Wei Qinglai Feng Jianxin Yu shan chang State Key Laboratory of Geological Processes and Mineral Resources China University of GeosciencesWuhan 430074China School of Earth Sciences China University of GeosciencesWuhan 430074China College of Urban and Environmental Sciences Hubei Normal UniversityHuangshi 435002China

The Early Cambrian Niutitang Formation on the Yangtze Block is a set of high-quality marine source ***,hydrocarbon-forming organisms of these organic-rich shales was poorly *** this paper,the results of palynofacies analysis and hydrocarbon-forming organism characteristics of the Niutitang Formation from the Yangtze Block are reported for the first time,and the sedimentary environment is discussed in combination with geochemical *** analysis show that the organic matter(OM)of the Niutitang Formation is mainly composed of amorphous organic matter(AOM),with a small amount of structural organic matter(STOM)and palynomorphs(PL).The results of CONISS(stratigraphically constrained incremental sum of squares)cluster analysis show that the PL can be divided into three zones in the ascending order:Leiosphaeridia-Micrhystridiumfungal zone,algal bloom zone and fungal development zone,corresponding to three stages:transgression,high-stand and regression,*** principal component analysis(PCA)shows that the main hydrocarbon-forming organisms include planktonic green microalgae or dinoflagellates that are related to Leiosphaeridia and *** analysis and geochemical data show that the Niutitang Formation was deposited under anoxic or dysoxic condition which was favorable to the enrichment of organic matter.

关键词： organic matter palynofacies hydrocarbon-forming organisms sedimentary environment Niutitang Formation Yangtze Block

A Diverse Microfossil Assemblage from the Ediacaran–Cambrian Deep-Water Chert of the Liuchapo Formation in Guizhou Province,South China

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Journal of Earth Science 2023年第2期34卷 398-408页

作者： Yan Zhang shan chang Qinglai Feng Shucan Zheng State Key Laboratory of Geological Processes and Mineral Resources China University of GeosciencesWuhan 430078China School of Earth Sciences China University of GeosciencesWuhan 430074China College of Urban and Environmental Sciences Hubei Normal UniversityHuangshi 435002China School of Architectural Engineering Huanggang Normal UniversityHuanggang 438000China

The Ediacaran to Cambrian transition witnessed great biological and environmental turnovers from the Precambrian to *** changes are also reflected by the fossil records during that ***,the fossil distribution was highly *** diverse fossils were constantly found from the shallow shelf including restricted basins,reports from deep-water areas,which are characterized by chert-dominated formations straddling the Ediacaran-Cambrian boundary,were *** them was the Liuchapo Formation that has been considered *** this study,a fossiliferous assemblage was found from the Liuchapo Formation in east Guizhou Province,South *** assemblage comprises Palaeopascichnus jiumenensis,Horodyskia minor,multicellular algae that possibly related with red algae,cyanobacteria,sponge spicules,small shelly fossils,membrane structures of uncertain affinity,and fossils with structures resemble the Ediacaran *** and Horodyskia have been widely reported and abundant in the Liuchapo Formation and equivalents,while the others have seldomly,or never,been found from this formation or,more widely,the deep-water chert of transitional *** discovery not only contributes to the rare paleontological records preserved in deep-water sediments,but also expanded the geographic distribution of the fossils,providing new materials of biological diversity during this critical interval.

关键词： Liuchapo Formation Early Cambrian latest Ediacaran deep-water chert fossils paleobiology

Quasi-Static and Dynamic Behaviors of Helical Gear System with Manufacturing Errors

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Chinese Journal of Mechanical Engineering 2018年第2期31卷 106-114页

作者： Bing Yuan shan chang Geng Liu Li-Yan Wu Shaanxi Engineering Laboratory for Transmissions and Controls School of Mechanical Engineering Northwestern Polytechnical University China Shipbuilding Industry Corporation 703 Institute

Time?varying mesh stiffness(TVMS) and gear errors include short?term and long?term components are the two main internal dynamic excitations for gear transmission. The coupling relationship between the two factors is usually neglected in the traditional quasi-static and dynamic behaviors analysis of gear system. This paper investigates the influence of short?term and long?term components of manufacturing errors on quasi?static and dynamic behaviors of helical gear system considering the coupling relationship between TVMS and gear errors. The TVMS, loaded static transmission error(LSTE) and loaded composite mesh error(LCMS) are determined using an improved loaded tooth contact analysis(LTCA) model. Considering the structure of shaft, as well as the direction of power flow and bearing location, a precise generalized finite element dynamic model of helical gear system is developed, and the dynamic responses of the system are obtained by numerical integration method. The results suggest that lighter loading conditions result in smaller mesh stiffness and stronger vibration, and the corresponding resonance speeds of the system become lower. Long?term components of manufacturing errors lead to the appearance of sideband frequency components in frequency spectrum of dynamic responses. The sideband frequency components are predominant under light loading conditions. With the increase of output torque, the mesh frequency and its harmonics components tend to be enhanced relative to sideband frequency components. This study can provide effective reference for low noise design of gear transmission.

关键词： Manufacturing error Mesh stiffness Transmission error Loaded composite mesh error Vibration acceleration Sideband frequency

Shale gas reservoir characteristics of Ordovician-Silurian formations in the central Yangtze area, China

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Frontiers of Earth Science 2017年第1期11卷 184-201页

作者： chang'an shan Tingshan ZHANG Yong WEI Zhao ZHANG School of Earth Sciences and Engineering Xi'an Shiyou University Xi'an 710065 China State Key Laboratory of Oil and Gas Reservoir Geology and Exploration Southwest Petroleum University Chengdu 610500 China School of Geoscience and Technology Southwest Petroleum University Chengdu 610500 China Exploration and Development Research Institute Southwest Oil & Gas field Company CNPC Chengdu 610041 China Exploration and Development department Zhejiang Oilfield Company CNPC Hangzhou 310023 China

The characteristics of a shale gas reservoir and the potential of a shale gas resource of Ordovician-Silurian age in the north of the central Yangtze area were determined. Core samples from three wells in the study area were subjected to thin-section examination, scanning electron microscopy, nuclear magnetic resonance testing, X-ray diffraction mineral analysis, total organic carbon （TOC） testing, maturity testing, gas-bearing analysis, and gas component and isothermal adsorption experiments. A favorable segment of the gas shale reservoir was found in both the Wufeng Formation and the lower part of the Longmaxi Formation; these formations were formed from the late Katian to early Rhuddanian. The high-quality shale layers in wells J1, J2, and J3 featured thicknesses of 54.88 m, 48.49 m, and 52.00 m, respectively, and mainly comprised carbonaceous and siliceous shales. Clay and brittle minerals showed average contents of 37.5% and 62.5% （48.9% quartz）, respectively. The shale exhibited type Ⅱ1 kerogens with a vitrinite reflectance ranging from 1.94% to 3.51%. TOC contents of 0.22%-6.05% （average, 2.39%） were also observed. The reservoir spaces mainly included micropores and microfractures and were characterized by low porosity and permeability. Well J3 showed generally high gas contents, i.e., 1.12-3.16 m^3/t （average 2.15 m^3/t）, and its gas was primarily methane. The relatively thick black shale reservoir featured high TOC content, high organic material maturity, high brittle mineral content, high gas content, low porosity, and low permeability. Shale gas adsorption was positively correlated with TOC content and organic maturity, weakly positive correlated with quartz content, and weakly negatively correlated with clay content. Therefore, the Wufeng and Longmaxi formations in the north of the central Yangtze area have a good potential for shale gas exploration.

关键词： reservoir characteristic shale gas Upper Ordovician Lower Silurian central Yangtze area