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Precise large deviations for generalized dependent compound renewal risk model with consistent variation

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Frontiers of Mathematics in China 2014年第1期9卷 31-44页

作者： Yu chen weiping ZHANG Chun SU Department of Statistics and Finance School of Management University of Science and Technology of China Hefei 230026 China

We investigate the precise large deviations of random sums of negatively dependent random variables with consistently varying tails. We find out the asymptotic behavior of precise large deviations of random sums is insensitive to the negative dependence. We also consider the generalized dependent compound renewal risk model with consistent variation, which including premium process and claim process, and obtain the asymptotic behavior of the tail probabilities of the claim surplus process.

关键词： Negative dependence precise large deviation random sum consistently varying tail

Microstructure and Mechanical Behavior of FeNiCoCr and FeNiCoCrMn High-Entropy Alloys Fabricated by Powder Metallurgy

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Acta Metallurgica Sinica(English Letters) 2021年第4期34卷 445-454页

作者： chenliang Chu weiping chen Zhen chen Zhenfei Jiang Hao Wang Zhiqiang Fu Guangdong Key Laboratory for Advanced Metallic Materials Processing South China University of TechnologyGuangzhou 510640China Shantou Technician College Shantou 515041China

The present work reports a systematic investigation on phase evolution,microstructure and microstructure-property relationship of two typical face-centered cubic(FCC)structured high-entropy alloys(HEAs),FeNiCoCr and FeNiCoCrMn,prepared via mechanical alloying(MA)followed by spark plasma sintering(SPS).Following 50 h of MA,the two HEAs consisted of a mixture of FCC and body-centered cubic *** SPS,the bulk FeNiCoCr alloy showed a primary FCC phase with a small amount of Cr_(23)C_(6) and Cr_(2)O_(3) contaminants,while the bulk FeNiCoCrMn alloy was composed of a primary FCC phase with some(Cr,Mn)23C6 and MnCr_(2)O_(4) *** average grain size of the primary FCC phase in the bulk FeNiCoCr alloy was~416 nm,while that of the primary FCC phase in the bulk FeNiCoCrMn alloy was~547 *** yield strength,compressive strength and strain-to-failure of the bulk FeNiCoCr alloy are 1525 MPa,1987 MPa and 24.4%,respectively,whereas those of the bulk FeNiCoCrMn alloy are 1329 MPa,1761 MPa and 21.9%,*** suggests that the bulk FeNiCoCrMn exhibited lower strength and plasticity in comparison with the bulk FeNiCoCr ***,the smaller grain size of the primary FCC phase in the FeNiCoCr alloy is mainly responsible for the better mechanical performance.

关键词： High-entropy alloy Mechanical alloying Microstructure Strengthening Contaminants

Synthesis and Characterization of Hyperbranched Epoxy with Terminal Ally Group and Its Application of Toughen Bismaleimide

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Journal of Wuhan University of Technology(Materials Science) 2021年第5期36卷 720-729页

作者： ZHANG Ze WANG Xiang chen Danxia chen Yao MA Wei chen weiping School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China

A hyperbranched epoxy(AHEP)resin with terminal allyl groups was *** number average molecular weight of the synthesized AHEP is 1260,the multi-dispersion coefficient is 1.88,and the branching degree is *** hyperbranched epoxy resin and bismaleimide(BMI)monomer were heated to extend the chain and then blended and cured with methyl nadic *** have found that when the molar ratio of AHEP:BDM is 1:2,the mechanical properties and heat resistance of the resin casting body reach the *** them,the impact toughness was 15.05 kg/m^(2),the bending strength was 101 MPa,and the heat resistance temperature index was 229.23℃.We used AHEP to toughen bismaleimide resin in three ways simultaneously:hyperbranched structure,allyl copolymerized brackets chain and flexible side chain(epoxy group)*** have proved that AHEP can improve the flexibility of the BMI chain and maintain its heat resistance,thereby forming a matrix with excellent mechanical properties and processing properties.

关键词： hyperbranched toughen resins

Evaluation of joint toxicity of heavy metals and herbicide mixtures in soils to earthworms(Eisenia fetida)

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Journal of Environmental Sciences 2020年第8期32卷 137-146页

作者： Xuzhi Li Meie Wang Rong Jiang Liping Zheng weiping chen State Key Laboratory of Urban and Regional Ecology Research Centre for Eco-environmental SciencesChinese Academy of SciencesBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China State Environmental Protection Key Laboratory of Soil Environmental Management and Pollution Control Nanjing Institute of Environmental SciencesMinistry of Ecology and EnvironmentNanjing 210042China

It is widely acknowledged that a simplified and robust approach to evaluating thecombined effects of chemical mixtures is critical for ecological risk assessment(ERA)of contaminated *** earthworm(Eisenia fetida)was used as a model to study the combined effects of polymetallic contamination and the herbicide siduron in field soil using a microcosm *** responses of multiple biomarkers,including the activities of catalase(CAT),superoxide dismutase(SOD),glutathione reductase(GR)and acetylcholine esterase(AChE),the concentrations of glycogen,soluble protein(SP),malonaldehyde(MDA),and metallothionein(MT),and the neutral red uptake test(NRU),were *** analysis,Principal Component Analysis(PCA)and Spearman’s Rank Correlations analysis(BVSTEP)revealed that the activities of AChE and CAT and the NRU content were the prognostic biomarkers capturing the minimum data set of all the *** Cd(tissue Cd)in earthworms was closely related to the health status of worms under combined contamination of heavy metals and *** integrated effect(E mix)calculated based on the activities of AChE and CAT and NRU content using the stress index method had significantly linear regression with internal Cd(p<0.01).E mix(10),E mix(20),and E mix(50)were then calculated,at 1.27,1.63 and 2.71 mg/kg dry weight,*** could be concluded that a bioassaybased approach incorporating multivariate analysis and internal dose was pragmatic and applicable to evaluating combined effects of chemical mixtures in soils under the guidance of the top-down evaluation concept of combined toxicity.

关键词： Siduron Polymetallic contamination Multiple biomarker responses Multivariate analysis Bioaccumulation

Estimation of the accumulation rates and health risks of heavy metals in residential soils of three metropolitan cities in China

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Journal of Environmental Sciences 2022年第5期34卷 149-161页

作者： Chi Peng Kai Zhang Meie Wang Xinxing Wan weiping chen Institute of Environmental Engineering School of Metallurgy and EnvironmentCentral South UniversityChangsha 410083China State key laboratory of urban and regional ecology Research center for eco-environmental sciencesChinese academy of sciencesBeijing 100085China Third Xiangya Hospital Central South UniversityChangsha 410013China

Heavy metal concentrations in urban soils are likely to increase over time because of contin-uous urbanization and heavy metal *** estimate the accumulation rates of heavy metals in urban soils,we collected soil samples from residential areas with different build-ing ages in the metropolitan cities of Shanghai,Shenzhen,and Beijing,*** metal concentrations in the soils varied among the cities and were primarily affected by soil parent material and the intensity of anthropogenic *** analyses revealed that the accumulation rates of Cd and Cu in the soils ranged from 0.0034 to 0.0039 mg/(kg·year)and 0.343 to 0.391 mg/(kg·year),respectively,and were similar across the three cities,while ac-cumulation rates of Zn and Pb in Shanghai were higher than those in Shenzhen and *** higher accumulation rates of Zn and Pb in Shanghai can be explained by differences in city history and industrial structures among the *** soils with high health risks posed by the heavy metals were mostly collected from old towns of Shanghai because of high Pb content in the *** recent urbanization resulted in elevated concen-trations of Cd,Cu,Zn,and Pb in the residential soils,the effect on the total health risks of residents exposed to the soils was negligible.

关键词： Urbanization Urban soil Health risk assessment Building age Regression model Source analysis

Effects of urbanization on heavy metal accumulation in surface soils, Beijing

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Journal of Environmental Sciences 2018年第2期30卷 328-334页

作者： Meie Wang Rui Liu weiping chen Chi Peng Bernd Markert State Key Laboratory of Urban and Regional Ecology Research Centre for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China Environmental Institute of Scientific Networks 49733 Haren Germany

Urbanization processes affect the accumulation of heavy metals in urban soils. Effects of urbanization on heavy metal accumulation in soils were studied using Beijing as an example. It has been suggested that the ecological function of vegetation covers shifting from natural to agricultural settings and then to urban greenbelts could increase the zinc（Zn） concentrations of soils successively. The Zn concentration of urban soils was significantly correlated to the percentage of the impervious land surface at the500 m × 500 m spatial scale. For urban parks, the age or years since the development accounted for 80% of the variances of cadmium（Cd） and Zn in soils. The population density,however, did not affect the heavy metal distributions in urban soils. To conclude, the urban age turned out to be a notable factor in quantifying heavy metal accumulation in urban soils.

关键词： Urban soils Human disturbance Zn Impervious land Population density

Wastewater reclamation and reuse in China:Opportunities and challenges

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Journal of Environmental Sciences 2016年第1期28卷 86-96页

作者： Sidan Lyu weiping chen Weiling Zhang Yupeng Fan Wentao Jiao State Key Laboratory for Urban and Regional Ecology Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China

The growing water stress both in terms of water scarcity and quality deterioration promotes the development of reclaimed water as a new water resource use. This paper reviewed wastewater reuse practices in China, and the opportunities and challenges of expanding reclaimed water use were analyzed. Rapid urbanization with the increasing of water demand and wastewater discharge provides an opportunity for wastewater reuse. The vast amount of wastewater discharge and low reclaimed water production mean that wastewater reuse still has a great potential in China. Many environmental and economic benefits and successful reclamation technologies also provide opportunities for wastewater reuse. In addition, the overall strategy in China is also encouraging for wastewater reuse. In the beginning stage of wastewater reclamation and reuse, there are many significant challenges to expand wastewater reuse in China including slow pace in adopting urban wastewater reuse programs, the establishment of integrated water resources management framework and guidelines for wastewater reuse programs, incoherent water quality requirements, the limited commercial development of reclaimed water and the strengthening of public awareness and cooperation among stakeholders.

关键词： Wastewater reuse Urbanization Policy Integrated water resource management Public acceptance

Multi-factors influencing the spatial distribution of polycyclic aromatic hydrocarbons in soils surrounding drinking water protection zone

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Journal of Environmental Sciences 2013年第8期25卷 1643-1648页

作者： Wentao Jiao Tieyu Wang Yonglong Lu Andrew Chang weiping chen State Key Laboratory of Urban and Regional Ecology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Department of Environmental Sciences University of California

We selected the Guanting Reservoir in Beijing, China as a case where an industrial area locates on the upwind corner to study the influence of human activities and natural processes on the distribution of polycyclic aromatic hydrocarbons （PAHs） in soils. Soil PAH concentrations in the study area follow a log-normal probability distribution function, suggesting that distribution of PAH in soils was affected by human activities. Distribution of PAHs in soils was significantly affected by the point source that high PAH concentrations were observed in near industrial area with an obvious declining trend from the northwest to the southeast which was the prevailing wind direction in this area. Away from the influence of point source, distribution of PAHs in soils was found to significantly correlate with total organic carbon content, while the influences of agricultural land uses and type of soil texture on the total soil PAHs contents and ring compositions were quite limited. The results can provide some evidences and data on the pollutant accumulation in drink water protection area influenced by natural processes and human activities.

关键词： soil PAH contamination Guanting Reservoir PAH distribution

Study on microstructure and properties of brass containing Sb and Mg

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Science China(Technological Sciences) 2009年第8期52卷 2172-2174页

作者： ZHU QuanLi WU WeiDong LIU KaiZhou chen GengChun chen weiping School of Mechanical and Automotive Engineering South China University of TechnologyGuangzhou 510640China

A novel free-cutting unleaded brass containing antimony and magnesium was prepared by gravity casting and hot extrusion. Microstructure of the hot extruded Sb-Mg brass was studied with scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS). Its mechanical properties were measured by tensile test, and cutting performance was investigated by lathe turning experiment. Results showed that microstructure of the hot extruded Sb-Mg brass was composed of α, β phases and Sb-Mg containing intermetallic compounds. The newly developed brass was compared with the HPb59-1 brass for its mechanical property. Its cutting performance was close to that of a German free-cutting unleaded brass. Sb-Mg brass has potential to replace HPb59-1 brass so as to reduce cost and protect environment.

关键词： unleaded brass Mg-Sb brass hot extrusion microstructure mechanical property cutting performance