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Backward Bifurcation in Simple SIS Model

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Acta Mathematicae Applicatae Sinica 2009年第1期25卷 127-136页

作者： zhan.wei Wang Department of Mathematics and Physics Zhengzhou Institute of Aeronautical Industry Management Zhengzhou450015 China

We describe and analyze a simple SIS model with treatment. In particular, we give a completely qualitative analysis by means of the theory of asymptotically autonomous system. It is found that a backward bifurcation occurs if the adequate contact rate or the capacity is small. It is also found that there exists bistable endemic equilibria. In the case of disease-induced death, it is shown that the backward bifurcation also occurs. Moreover, there is no limit cycle under some conditions, and the subcritical Hopf bifurcation occurs under another conditions.

关键词： SIS model backward bifurcation treatment bistable limit cycle

Roles of liver innate immune cells in nonalcoholic fatty liver disease

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World Journal of Gastroenterology 2010年第37期16卷 4652-4660页

作者： Yu-Tao zhan.wei An Department of Gastroenterology and Hepatology Beijing Tongren Hospital Capital Medical University Beijing 100730 China Department of Cell Biology Capital Medical UniversityBeijing 100069China

Nonalcoholic fatty liver disease (NAFLD) has become the most common liver disease in the United States and other developed countries and is expected to increase in the next few years. Emerging data suggest that some patients with NAFLD may progress to nonalcoholic steatohepatitis (NASH), cirrhosis and even hepatocellular carcinoma. NAFLD can also promote the development and progression of disease in other organ systems, such as the cardiovascular and endocrine (i.e. diabetes) systems. Thus, understanding the pathogenesis of NAFLD is of great clinical importance and is critical for the prevention and treatment of the disease. Although the "two-hit hypothesis" is generally accepted, the exact pathogenesis of NAFLD has not been clearly established. The liver is an important innate immune organ with large numbers of innate immune cells, including Kupffer cells (KCs), natural killer T (NKT) cells and natural killer (NK) cells. Recent data show that an imbalance in liver cytokines may be implicated in the development of fatty liver disease. For example, Th1 cytokine excess may be a common pathogenic mechanism for hepatic insulin resistance and NASH. Innate immune cells in the liver play important roles in the excessive production of hepatic Th1 cytokines in NAFLD. In addition, liver innate immune cells participate in the pathogenesis of NAFLD in other ways. For example, activated KCs can generate reactive oxygen species, which induce liver injury. This review will focus primarily on the possible effect and mechanism of KCs, NKT cells and NK cells in the development of NAFLD.

关键词： Innate immune cells Nonalcoholic fatty liver disease Kupffer cell Natural killer T cell Natural killer cell

Impacts of human activities on morphological evolution in the Modaomen Estuary, China

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Acta Oceanologica Sinica 2023年第5期42卷 79-92页

作者： Tiehan Liao Haigang zhan.Xing wei weikang zhan State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China University of Chinese Academy of Sciences Beijing 100049China Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou 511458China

The morphology of the Modaomen Estuary(ME)has undergone drastic changes in recent decades,and quantifying the contribution of human activities and natural processes is crucial for estuary *** Landsat images,chart data,and hydrological and meteorological data,this study analyzed the evolution of the shoreline and subaqueous topography of the ME and attempted to quantify the extent of the contributions of human *** results show that local human activities dominated morphological evolution in some *** 1973 to 2003,the shoreline advanced rapidly seaward,resulting in approximately half of the water area being converted into *** activity is critical to this process,with the direct contribution of local land reclamation projects reaching more than 85%.After 2003,the shoreline remained relatively stable,probably due to a decrease in land reclamation *** the evolution of subaqueous topography,the shoals in the estuary were heavily silted and gradually disappeared during 1983–2003,and the waterways narrowed and *** average siltation rate decreased from 15.43 mm/a to-1.02 mm/a,indicating that the ME changed from sedimentation to slight *** detecting variations of sediment load,we found that upstream human activities reduced river sediment,while downstream human activities significantly increased sediment input to the ME,leaving little change in the actual sediment input to the ME for a relatively long *** addition,based on the empirical relationship between the sediment input and siltation rate,local human activities influenced the shift in the siltation state more than upstream and downstream human activities *** findings suggest that more attention should be paid to local human activities to improve the estuarine management in the ME.

关键词： Modaomen Estuary morphological evolution human activity quantitative analysis

Gelfand–Kirillov Dimension and Reducibility of Scalar Generalized Verma Modules

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Acta Mathematica Sinica,English Series 2019年第11期35卷 1854-1860页

作者： zhan.Qiang BAI wei XIAO School of Mathematical Sciences Soochow UniversitySuzhou 215006P.R.China College of Mathematics and statistics Shenzhen Key Laboratory of Advanced Machine Learning Applications Shenzhen UniversityShenzhen 518060P.R.China

The Gelfand–Kirillov dimension is an invariant which can measure the size of infinitedimensional algebraic structures. In this article, we show that it can also measure the reducibility of scalar generalized Verma modules. In particular, we use it to determine the reducibility of scalar generalized Verma modules associated with maximal parabolic subalgebras in the Hermitian symmetric case.

关键词： Gelfand–Kirillov dimension generalized Verma module reducibility

Biomechanical properties of ready-to-harvest rapeseed plants:Measurement and analysis

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Information Processing in Agriculture 2023年第3期10卷 391-399页

作者： Guangchao zhan.Wangyuan Zong Lina Ma Junyi wei wei Liu College of Engineering Huazhong Agricultural UniversityWuhan 430070PR China Key Laboratory of Agricultural Equipment in Middle-lower Reaches of the Yangtze River Ministry of Agriculture and Rural AffairsWuhan 430070PR China

A large loss occurs in the combine harvesting of rapeseeds due to the fragility of rapeseed pods,and all the more so with the vibration of the combine header and the collision between the header and *** loss is greatly affected by the biomechanical properties of ready-to-harvest rapeseed *** understand the mechanism of pod cracking and seed loss and to propose measures for alleviating them,it is needed to study the biomechanical properties of ready-to-harvest rapeseed *** this end,“Huayouza 62”,a widely planted rapeseed variety in central China,was selected to study the biomechanical properties,including pod-cracking resistance,main stem-shearing resistance and resonant frequencies,of whole *** results showed that the distribution of pod-cracking resistance forces was 1.333–6.100 N in the mature stage,and the pod width and thickness had a significant influence on the cracking *** main influencing factor of the main stem-shearing resistance was the stem diameter.A thicker main stem resulted in a larger shearing resistance force but a smaller shear *** moisture contents of the main stems varied from 47.71%to 76.13%.However,the varying moisture contents did not show a significant impact on the shearing *** resonant frequencies of whole rapeseed plants ready for harvest ranged from 6.5 Hz to 7.5 Hz,which was close to the excitation frequency of the cutter bar on the 4LL-1.5Y *** study lays a foundation for improving the design and construction of harvesting devices for rapeseed plants to reduce seed loss.

关键词： Rapeseed pod Cracking resistance Shearing resistance Resonant frequency Rapeseed harvesting

Structural properties and catalytic performance of the La-Cu-Zn mixed oxides for CO2 hydrogenation to methanol

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Journal of Rare Earths 2018年第3期36卷 273-280页

作者： Haijuan zhan.Zhiqiang Wu Ning Zhao Wanyi Liu wei wei School of Chemistry and Chemical Engineering Ningxia UniversityYinchuan 750021China State Key Laboratory of High-efficiency Coal Utilization and Green Chemistry Engineering Ningnia UniversityYinchuan 750021China State Key Laboratory of Coal Conversion Institute of Coal ChemistryChinese Academy of SdencesTaiyuan 030001China Center for Greenhouse Gas and Environmental Engineering Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201203China

A series of La-Cu-Zn-O mixed oxide catalysts were synthesized by a co-precipitation method and calcined under different temperatures. The XRD, BET, TPR, N2 O-adsorption, XPS, SEM and TPD techniques were carried out to measure the aimed catalysts. The results indicated that the chemical environment of lanthanum element changes with the increase of calcination temperature. The La2 CuO4 perovskite structure is obtained at the temperature higher than 823 K and the special copper species appear in the perovskites due to the special structure property. The catalysts with La2 CuO4 perovskite structure show higher methanol selectivity compared with the mixed copper catalyst. For the perovskite catalysts, the conversion of CO2 changes with the same tendency of the copper species ratio（（Cu^（α＋）＋Cu^0）/（Cu（Total））%）, which implied both Cu^（α＋） and Cu^0 are important active sites in the perovskite catalyst for the reaction.

关键词： La2CuO4 perovskite CO2 hydrogenation Rare earths

Exploration of Rare-Earth Element Sc to Enhance Microstructure, Mechanical Properties and Corrosion Resistance of Zr-8.8Si Biomedical Alloy

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Journal of Bionic Engineering 2022年第2期19卷 530-546页

作者： Yaokun Fu Liying Luo Chengxia wei Yongzhong zhan School of Resources Environment and MaterialsGuangxi UniversityNanning 530004China Guangxi Key Laboratory of Processing for Non-Ferrous Metal and Featured Materials Guangxi UniversityNanning 530004China Department of Materials Science and Engineering Southern University of Science and TechnologyShenzhen 518000China

The main mechanism of rare-earth element Sc on the microstructure and properties of Zr-8.8Si biomaterial alloy was *** novel Zr-8.8Si-xSc(x=0,5,10 and 15 at.%)alloys were prepared by electric arc smelting with Ar *** microstructural and mechanical properties as well as electrochemical corrosion and tribological behaviors in artificial saliva solution of the Zr-8.8Si-xSc alloys were systematically *** results show that the Zr-8.8Si-xSc alloys only consist of two-phase α-Zr and Zr_(3)Si,Sc dissolve in α-Zr matrix to form Zr-Sc solid *** addition of Sc is conducive to refine microstructure,and reduce micro-pores of Zr-8.8Si alloy which lead to higher Young's modulus,compressive strength and *** them,the highest value of Young's modulus is 31.5 GPa,still at a low level in biomedical *** promotion of corrosion resistance can be attributed to the addition of Sc which can accelerate the formation of passive film,slow down the appearance of pitting and reduce the accumulation of corrosion products in *** the condition of sliding wear test with artificial saliva solution,compared with Zr-8.8Si-0Sc alloy,the wear loss of samples with Sc is greatly decreased,and wear resistance is increased with increasing content of *** experimental results indicate that the combination of good mechanical properties,corrosion resistance and tribological properties of Zr-8.8Si-(5,10 and 15 at.%)Sc alloys was much better than Zr-8.8Si-0Sc *** them,the comprehensive property of Zr-8.8Si-10Sc alloy is preferable in this work.

关键词： Zr-8.8Si-xSc alloys Biomedical alloy Microstructure Mechanical properties Corrosion resistance Tribological properties

Existence of Positive Solutions to Fourth Order Quasilinear Boundary Value Problems

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Acta Mathematica Sinica,English Series 2006年第6期22卷 1825-1830页

作者： zhan.Bing BAI wei Gao GE Institute of Mathematics Shandong University of Science and Technology Qingdao 266510 P.R. China Department of Applied Mathematics Beijing Institute of Technology Beijing 100081 P.R. China

In this paper, we generalize the fixed point theorem of cone expansion and compression of norm type to the theorem of functional type. As an application, the existence of positive solutions for some fourth-order beam equation boundary value problems is obtained. The emphasis is put on that the nonlinear term is dependent on all lower order derivatives.

关键词： fourth-order boundary value problem fixed point theorem positive solution

A deep water shelly fauna from the uppermost Ordovician in northwestern Hunan, South China and its paleoecological implications

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Science China Earth Sciences 2018年第6期61卷 730-744页

作者： Jiayu RONG Xin wei Renbin zhan.Yi WANG State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences School of Earth and Space Sciences University of Science and Technology of China College of Earth Sciences University of Chinese Academy of Sciences

It is the first time to document the trilobite Mucronaspis(Songxites) wuningensis and the brachiopod ParomalomenaAegiromenella Assemblage from the Xinkailing Bed(Hirnantian, uppermost Ordovician) in Taoyuan and Cili counties,northwestern Hunan Province. Synecological analysis shows that this is a deep water shelly fauna of South China during the Hirnantian. It lived on the upper Jiangnan Slope in northwestern Hunan, adjacent to the southeast margin of the Upper Yangtze Region, and belongs to the Hirnantia fauna with cool and deep water, and low diversity affinity, similar to its contemporary shelly faunas from the southern Shaanxi Slope adjacent to the north margin of the Upper Yangtze Region, the northern Chongqing depression(new name), and the Jiangxi-Anhui-Jiangsu gentle slope of the Lower Yangtze Region. Paleoecologically,it could be attributed to the BA 4–5 benthic regime(about 60–150 m deep, and deepest to 200 m), and was significantly different from the trilobite M.(S.) mucronata and the typical Hirnantia fauna while the latters may have habited in BA 2–3 benthic regimes(about 5–60 m deep). A new paleogeographic distribution pattern of the Hirnantian shallow and deep water shelly faunas of South China is herein proposed for the first time. Assuming that the depositional rate was constant in northwestern Hunan during the end Ordovician, the duration of the Xinkailing Bed might be only 12 thousand years according to the thickness of the Wufeng Formation and the absolute age values of those relevant graptolitic biozones. Such a short time interval may indicate that the global environmental change during the crisis was much shorter than previously thought, and its influence on the deep water regime was significantly shorter than that on the shallow water regime.

关键词： Hirnantia fauna Latest Ordovician Deeper water facies Community ecology Northwestern Hunan