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A delayed SEIRS epidemic model with impulsive vaccination and nonlinear incidence rate

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International Journal of Biomathematics 2014年第3期7卷 149-162页

作者： jiancheng zhang and jitao sun Department of Mathernatics Tongji University Shanghai 200092 P. R. China

In this paper, a delayed SEIRS epidemic model with nonlinear incidence rate and impul- sive vaccination is investigated. In vaccination strategy, we perform impulsive vaccina- tion of newborn infants. Using the discrete dynamic system determined by stroboscopic map, we obtain an infection-free periodic solution and establish conditions, on which the solution is globally attractive. We also conclude that the disease is permanent if the parameters of the model satisfy appropriate conditions. Finally, we illustrate the effec- tiveness of our theorems with numerical simulation. The results obtained in this paper are a good extension of the results obtained in [J. Hou and Z. Teng, Continuous and impulsive vaccination of SEIR epidemic models with saturation incidence rate, Math. Comput, Simulat. 79 （2009） 3038 3054] to the corresponding delayed SEIRS epidemic model with nonlinear incidence rate and impulsive vaccination.

关键词： SEIRS impulsive vaccination delay globally attractive permanence.

Devonian integrative stratigraphy,biotas,and paleogeographical evolution of the Qinghai-Tibetan Plateau and its surrounding areas

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Science China Earth Sciences 2024年第4期67卷 1036-1070页

作者： Wenkun QIE Kun LIANG Wen GUO Biao GAO Junjun SONG Bo CHEN Pu HUANG Li QIAO Honghe XU jitao CHEN Yucong sun Yichun zhang State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and PalaeontologyChinese Academy of SciencesNanjing 210008China University of Chinese Academy of Sciences Nanjing 211135China

The Devonian System in the Qinghai-Tibetan Plateau and its surrounding areas is widely distributed,diverse in lithotypes and rich in *** records the crucial processes of continuous subduction and reduction of the Paleo-Asian Ocean in the northern hemisphere and the transformation of the Proto-Tethys Ocean into the Paleo-Tethys Ocean in the southern ***,it is of great significance for explaining the global paleogeographic evolution,tectonic activities and biodiversity changes during this critical *** blocks on both sides of the southern Tienshan suture zone and the Longmu Co-ShuanghuChangning-Menglian suture zone belong to different sedimentary systems and paleobiogeographic realms and regions,showing important tectonic paleogeographic partitioning *** two suture zones represent the main branches of the PaleoAsian Ocean and the Paleo-Tethys Ocean,respectively,and on this basis the Devonian System can be subdivided into three types:the Tienshan type,the Tethys type and the Gondwana *** on recent research progress on the Devonian stratigraphy and paleontology in combining provenance analysis and biotic characteristics in the Qinghai-Tibetan Plateau and surrounding areas,this paper aims to establish the latest integrative stratigraphic framework and conduct paleogeographic reconstruction,providing foundation for exploring the geological evolution and dynamic mechanisms of various terranes and blocks in the northern margin of *** results indicate that the North Qiangtang,South Qiangtang,Simao,Baoshan and Tengchong terranes,as well as the Himalaya Tethys Zone and the South China Block have affinities with the Indian Block,while the Lhasa Terrane has affinities with the Australian Block,and may be located between the South China and Australian *** the Emsian(Early Devonian),the South China Block separated from the northern margin of Gondwana,a process that was accompanied by the opening of the Jinshajiang-Ailaosh

关键词： Devonian Paleo-Tethys Ocean Integrative stratigraphy Biotas Provenance Analysis Paleogeography

Analysis and suppression of operational overvoltage and inrush current for high-speed trains by automatic phase-switching technique

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HIGH VOLTAGE 2024年第3期9卷 733-748页

作者： Cao, Ye Xiao, Song Ye, Zhizong Wu, Guangning Guo, Yujun Gao, Guoqiang sun, Chuanming Liu, jiancheng Chen, Zheng Hou, Hao Wang, Zijing Liu, Puyang zhang, Yuhui Yu, Jie Southwest Jiaotong Univ Sch Elect Engn Chengdu Peoples R China Guangdong Power Grid LLC Co China Southern Power Grid Guangzhou Peoples R China CRRC Qingdao Sifang Co Ltd Qingdao Peoples R China State Grid Chongqing Elect Power Co Chongqing Peoples R China

When a high-speed train approaches the insulated phase-splitting section embedded between neighbouring power supply arms, the vacuum circuit breaker (VCB) installed on trains must be disconnected to maintain the traction power supply system as a no-load condition for completing phase-switching action, as the train passes through the phase-splitting section depending on its inertia. However, when operating VCBs, the arc is easily triggered between the mobile contacts inside, accompanied by an overvoltage impulse. Herein, to explore the generating mechanism of inrush current and operational overvoltage, a model describing the 'substation-catenary-train' traction power supply system is launched based on an equivalent circuit modelling technique. Through the analysis of the transient VCB operational process, the phase of catenary voltage is directly related to the characteristics of the VCB switching-on overvoltage, as the traction current's phase angle is relevant to the amplitude-frequency characteristics of the VCB switching-off overvoltage. Inrush current as a noteworthy element is related to the traction transformer's remanence. The automatic phase-switching technique is utilised to suppress both operational overvoltage and inrush current, as the optimal combination of VCB switching-on and switching-off phases considering the balance between overvoltage and inrush current is achieved based on the particle swarm algorithm.

关键词： IMPACT

Deforestation in Latin America in the 2000s predominantly occurred outside of typical mature forests

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The Innovation 2024年第3期5卷 88-98页

作者： Zhiyu zhang Wenjian Ni Shaun Quegan Jingming Chen Peng Gong Luiz Carlos Estraviz Rodriguez Huadong Guo jiancheng Shi Liangyun Liu Zengyuan Li Yating He Qinhuo Liu Yosio Shimabukuro Guoqing sun Key Laboratory of Remote Sensing and Digital Earth Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Shijingshan DistrictBeijing 100049China Chinal of Mathematics and Statistics University of SheffieldSheffield S37RHUK Department of Geography and Program in Planning University of TorontoTorontoON M5S 3G3Canada Department of Earth Sciences and Department of Geography University of Hong KongHong KongChina Forest Science Department Luiz de Queiroz College of AgricultureUniversity of São PauloAv.Pádua Dias11Piracicaba 13418-900Brazil National Space Science Center Chinese Academy of SciencesBeijing 100190China Institute of Forest Resource Information Techniques Chinese Academy of ForestryBeijing 100091China Research Institute of Forest Policy and Information Chinese Academy of ForestryBeijing 100091China Remote Sensing Department National Institute for Space Research(INPE)Av.dos Astronautas 1758São Josédos Campos 12227-010Brazil Department of Geographical Sciences University of MarylandCollege ParkMD 20742USA

The role of tropical forests in the global carbon budget remains controversial,as carbon emissions from deforestation are highly *** high uncertainty arises from the use of either fixed forest carbon stock density or maps generated from satellite-based optical reflectance with limited sensitivity to biomass to generate accurate estimates of emissions from *** space missions aiming to accurately map the carbon stock density rely on direct measurements of the spatial structures of forests using lidar and *** found that lost forests are special cases,and their spatial structures can be directly measured by combining archived data acquired before and after deforestation by space missions principally aimed at measuring ***,using biomass mapping,we obtained new estimates of carbon loss from deforestation ahead of forthcoming space ***,using a high-resolution map of forest loss and the synergy of radar and lidar to estimate the aboveground biomass density of forests,we found that deforestation in the 2000s in Latin America,one of the severely deforested regions,mainly occurred in forests with a significantly lower carbon stock density than typical mature forests.

关键词： forest Latin lidar

Gigahertz-rate-switchable wavefront shaping through integration of metasurfaces with photonic integrated circuit

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Advanced Photonics 2024年第1期6卷 106-114页

作者： Haozong Zhong Yong Zheng Jiacheng sun Zhizhang Wang Rongbo Wu Ling-en zhang Youting Liang Qinyi Hua Minghao Ning jitao Ji Bin Fang Lin Li Tao Li Ya Cheng Shining Zhu East China Normal University School of Physics and Electronic ScienceState Key Laboratory of Precision SpectroscopyShanghaiChina Nanjing University College of Engineering and Applied SciencesNational Laboratory of Solid State MicrostructuresNanjingChina China Jiliang University College of Optical and Electronic TechnologyHangzhouChina Shanxi University Collaborative Innovation Center of Extreme OpticsTaiyuanChina Chinese Academy of Sciences(CAS) Shanghai Institute of Optics and Fine Mechanics(SIOM)State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-Intense Laser ScienceShanghaiChina

Achieving spatiotemporal control of light at high speeds presents immense possibilities for various applications in communication,computation,metrology,and *** integration of subwavelength metasurfaces and optical waveguides offers a promising approach to manipulate light across multiple degrees of freedom at high speed in compact photonic integrated circuit(PIC)***,we demonstrate a gigahertz-rate-switchable wavefront shaping by integrating metasurface,lithium niobate on insulator photonic waveguides,and electrodes within a PIC *** proofs of concept,we showcase the generation of a focus beam with reconfigurable arbitrary polarizations,switchable focusing with lateral focal positions and focal length,orbital angular momentum light beams as well as Bessel *** measurements indicate modulation speeds of up to the gigahertz *** integrated platform offers a versatile and efficient means of controlling the light field at high speed within a compact system,paving the way for potential applications in optical communication,computation,sensing,and imaging.

关键词： metasurface photonic integrated circuit lithium niobate on insulator high-speed modulation

On Existence and Uniqueness of Random Impulsive Differential Equations

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Journal of Systems Science & Complexity 2016年第2期29卷 300-314页

作者： zhang Shuorui sun jitao Department of Mathematics Tongji University

This paper studies existence and uniqueness for random impulsive differential *** authors first generalize a random fixed point theorem of Schaefer's *** the authors shall rely on the generalized Schaefer's type random fixed point theorem to discuss the existence of the *** addition,the authors study the existence and uniqueness of random impulsive differential equations by applying random Banach fixed point theorem and obtain some less conservative ***,an example is given to illustrate the effectiveness of the results.

关键词： Existence impulses random differential equations random fixed point uniqueness.

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基于纤维素纳米纤维的电磁屏蔽材料研究进展

复合材料学报 2024年第3期41卷 1109-1123页

作者：张建成郭伟佳沈顺禹张倩李彩彩孙庆丰浙江农林大学化学与材料工程学院杭州311300

纤维素纳米纤维(CNFs)作为一种新型的一维纳米材料,具有来源广泛、长径比高、力学性能优异等特点。以CNFs为载体或增强相通过不同的方法可以制备出多种多样的电磁屏蔽功能复合材料,如气凝胶、薄膜和海绵等。本文基于电磁屏蔽的原理,综述... 详细信息

纤维素纳米纤维(CNFs)作为一种新型的一维纳米材料,具有来源广泛、长径比高、力学性能优异等特点。以CNFs为载体或增强相通过不同的方法可以制备出多种多样的电磁屏蔽功能复合材料,如气凝胶、薄膜和海绵等。本文基于电磁屏蔽的原理,综述了CNFs基电磁屏蔽材料的制备方法及研究进展,并比较了不同的CNFs基电磁屏蔽材料在结构和性能上的差异,最后对CNFs基电磁屏蔽功能复合材料未来的发展方向进行了展望。

关键词：纤维素纳米纤维制备方法复合材料电磁屏蔽研究进展

Development and application of state-dependent fractional plasticity in modeling the non-associated behavior of granular aggregates

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Acta Mechanica Solida Sinica 2017年第5期30卷 507-519页

作者： Yifei sun Shunxiang Song Yang Xiao jiancheng zhang Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering College of Civil and Transportation Engineering Hohai University Nanjing 210098 China. College of Civil and Transportation Engineering Hohai University Nanjing 210098 China. State Key Laboratory of Coal Mine Disaster Dynamics and Control School of Civil Engineering Chongqing University Chongqing 400450 China School of Naval Architecture and Civil Engineering Jiangsu University of Science and Technology Jiangsu 215600 China

To characterize the constitutive behavior of granular aggregates, a non-associated plasticity model with two different yield and plastic potential surfaces was usually used. However, in this paper, a state-dependent fractional elastoplastic model is proposed by only perform- ing the first- and fractional-order differentiations of the yield function. The non-associated plastic flow is obtained without using any plastic potential functions. The state dependence is considered by correlating the fractional order with a state parameter. The model is then validated by simulating a series of test results of different granular aggregates, including sand, ballast and rockfill, under a variety of loading conditions.

关键词： Fractional plasticityGranular aggregatesNon-associated flow

高铁过电压对车载牵引供电系统的影响机理及抑制方法:系统性综述

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中国电机工程学报 2024年第12期44卷 4682-4701,I0008页

作者：肖嵩曹野吴广宁高国强郭裕钧张血琴孙传铭刘建城西南交通大学四川省成都市611756 中车青岛四方机车车辆股份有限公司山东省青岛市266611

为了追求更高的牵引速度及更强的运载能力,高铁车载牵引供电系统功率容量不断提升,现有牵引供电系统及关键设备需要应对更高频次、更大幅值的过电压冲击,如何保障列车在高速运行状态下牵引系统安全、可靠地运行是如今高速列车设计面临... 详细信息

为了追求更高的牵引速度及更强的运载能力,高铁车载牵引供电系统功率容量不断提升,现有牵引供电系统及关键设备需要应对更高频次、更大幅值的过电压冲击,如何保障列车在高速运行状态下牵引系统安全、可靠地运行是如今高速列车设计面临的重要技术挑战。详细调研了过电压导致牵引供电系统出现的典型故障,归纳了高速列车中过电压的种类及相关特性,目前主流的牵引供电方式包括采用带回流线的直接供电方式与自耦变压器(automatic transformer,AT)供电方式,均是单相交流供电制式。为了保障三相负荷平衡,防止系统中负序电流的产生,传输异相电流的相邻供电臂间通过绝缘分相区进行隔离。列车在驶过分相区时需要操作车载真空断路器(vacuum circuit breaker,VCB),分合闸过程中会产生剧烈的过电压冲击;此外,“弓-网”离线电弧及“轮-轨”滚动电弧频发,也伴随着过电压。通过调研目前已构建的牵引供电系统过电压特性仿真模型,探究了过电压的产生机理及传播规律;梳理了影响过电压特性的关键因素及抑制措施;明确了未来的研究重点,即“弓-网”及“轮-轨”燃弧过电压产生的机理和影响;“多车共臂”及“多车重联”工况下过电压的传播规律;展望了“源头-路径-终端”三位一体的过电压抑制方法。

关键词：高速列车过电压真空断路器电弧弓网离线电弧 “轮-轨”滚动电弧

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