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Stability and Hopf bifurcation of a delayed ratio-dependent predator-prey system

Acta Mechanica Sinica 2011年第2期27卷 285-296页

作者： Wan-Yong Wang li-jun pei School of Aerospace Engineering and Applied Mechanics Tongji University 200092 Shanghai China Department of Mathematics Zhengzhou University 450001 Zhengzhou China

Since the ratio-dependent theory reflects the fact that predators must share and compete for food, it is suitable for describing the relationship between predators and their preys and has recently become a very important theory put forward by biologists. In order to investigate the dynamical relationship between predators and their preys, a so-called Michaelis-Menten ratio-dependent predator-prey model is studied in this paper with gestation time delays of predators and preys taken into consideration. The stability of the positive equilibrium is investigated by the Nyquist criteria, and the existence of the local Hopf bifurcation is analyzed by employing the theory of Hopf bifurcation. By means of the center manifold and the normal form theories, explicit formulae are derived to determine the stability, direction and other properties of bifurcating periodic solutions. The above theoretical results are validated by numerical simulations with the help of dynamical software WinPP. The results show that if both the gestation delays are small enough, their sizes will keep stable in the long run, but if the gestation delays of predators are big enough, their sizes will periodically fluc-tuate in the long term. In order to reveal the effects of time delays on the ratio-dependent predator-prey model, a ratiodependent predator-prey model without time delays is considered. By Hurwitz criteria, the local stability of positive equilibrium of this model is investigated. The conditions under which the positive equilibrium is locally asymptotically stable are obtained. By comparing the results with those of the model with time delays, it shows that the dynamical behaviors of ratio-dependent predator-prey model with time delays are more complicated. Under the same conditions, namely, with the same parameters, the stability of positive equilibrium of ratio-dependent predator-prey model would change due to the introduction of gestation time delays for predators and preys. Moreover, w

关键词： Time delays · Stability · Hopf bifurcation · Normal form · Center manifold

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Multiple biomarkers response in maize (Zea mays L.)during exposure to copper

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Journal of Environmental Sciences 2006年第6期18卷 1182-1188页

作者： QI Xue-mei li pei-jun liU Wan XIE li-jing Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 China Graduate School of Chinese Academy of Sciences Beijing 100039 China College of Energy and Environmental Engineering Shanghai University of Electric Power Shanghai 200090 China College of Resource and Environment North East Agriculture University Harbin 150030 China

Biomarkers in higher plants played an important role to estimate exposure effects of pollutants in soil ecosystem and have received increasing attention in recent years. The qualitative and quantitative modifications arising in amplified fragment length polymorphism （AFLP） profiles as a measure of DNA effects were compared with a number of parameters, namely, the root length, total soluble protein content in root tips, chlorophylls content and shoot size to select the most sensitive biomarker responding to copper stress in the range of 0--600 mg/kg. The changes occurring in AFLP profiles of root tips following Cu treatment included loss of normal bands and appearance of new bands and variation in band intensity in comparison to that of the normal seedlings, A reduction in root length was observed at the 200 mg/kg of copper, which was accompanied with a decrease in total soluble protein content. According to their sensitivity to the copper toxicity, the above indicator rank in the following order： AFLP profiles 〉 total soluble protein content 〉 root length 〉 chlorophylls content 〉 shoot. We concluded that the AFLP offered a useful alternative hiomarker assay for the detection of genotoxic effects of environmental pollutants.

关键词： copper biomarker genotoxicity DNA damage

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Photochemical behavior of benzo[a]pyrene on soil surfaces under UV light irradiation

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Journal of Environmental Sciences 2006年第6期18卷 1226-1232页

作者： ZHANG li-hong li pei-jun GONG Zong-qiang Oni Adeola A. Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Department of Environmental Science University of Liaoning Shenyang 110036 China Department of Zoology University of Ibadan Ibadan Nigeria

The rates of photodegradation and photocatalysis of benzo [a]pyrene （BaP） on soil surfaces under UV light have been studied. Different parameters such as temperature, soil particle sizes, and soil depth responsible for photodegradation, catalyst loads and wavelength of UV irradiation blamed for photocatalysis have been monitored. The results obtained indicated that BaP photodegradation follows pseudo-first-order kinetics. BaP photodegradation was the fastest at 30℃ . The rates of BaP photodegradation at different soil particle size followed the order： less than 1 mm〉less than 0.45 mm〉less than 0.25 mm. When the soil depth increased from 1 mm to 4 ram, the half-life increased from 13.23 d to 17.73 d. The additions of TiO2 or Fe2O3 accelerated the photodegradation of BaP, and the photocatalysis of BaP follows pseudo-first-order kinetics. Changes in catalyst loads of TiO2 （0.5%, 1%, 2%, and 3% （wt）） or Fe203 （2%, 5%, 7%, and 10% （wt）） did not significantly affect the degradation rates. Both BaP photocatalysis in the presence of TiO2 and Fe2O3 were the fastest at 254 nm UV irradiation.

关键词： photodegradation photocatalysis benzo[a]pyrene UV-irradiation

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Biodegradation of benzo[a]pyrene in soil by Mucor ***06 and Bacillus ***02 co-immobilized on vermiculite

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Journal of Environmental Sciences 2006年第6期18卷 1204-1209页

作者： SU Dan li pei-jun FRANK Stagnitti XIONG Xian-zhe Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 China Graduate University of Chinese Academy of Sciences Beijing 100049 China School of life and Environmental Science Faculty of Science and Technology P. O Box 423 Warmambool Victoria 3280 Australia

Two indigenous microorganisms, Bacillus sp. SB02 and Mucor sp. SF06, capable of degrading polycyclic aromatic hydrocarbons （PAHs） were co-immobilized on vermiculite by physical adsorption and used to degrade benzo[a] pyrene （BaP）. The characteristics of BaP degradation by both free and co-immobilized microorganism were then investigated and compared. The removal rate using the immobilized bacterial-fungal mixed consortium was higher than that of the freely mobile mixed consortium. 95.3% of BaP was degraded using the co-immobilized system within 42 d, which was remarkably higher than the removal rate of that by the free strains. The optimal amount of inoculated co-immobilized system for BaP degradation was 2%. The immobilized bacterial-fungal mixed consortium also showed better water stability than the free strains. Kinetics of BaP biodegradation by co-immobilized SF06 and SB02 were also studied. The results demonstrated that BaP degradation could be well described by a zero-order reaction rate equation when the initial BaP concentration was in the range of 10--200 mg/kg. The scanning electronic microscope （SEM） analysis showed that the co-immobilized microstructure was suitable for the growth of SF06 and SB02. The mass transmission process of co-immobilized system in soil is discussed. The results demonstrate the potential for employing the bacterial-fungal mixed consortium, co-immobilized on vermiculite, for in situ bioremediation of BaP.

关键词： biodegradation Bacillus sp. SB02 Mucor sp. SF06 benzo[a]pyrene immobilization soil pollution

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基于地层元素测井的鄂西宜昌地区下寒武统水井沱组页岩储层参数评价

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矿物岩石地球化学通报 2024年第3期43卷 553-562页

作者：童广勤陈林李培军秦维秉韩晓影苗凤彬高坝大库运行安全湖北省重点实验室湖北宜昌443133 中国长江三峡集团有限公司流域枢纽运行管理中心湖北宜昌443133 中国地质调查局武汉地质调查中心(中南地质科技创新中心) 武汉430205 南方复杂构造区页岩油气成藏理论与工程技术创新中心武汉430205 南方复杂构造区页岩气研究中心武汉430205 华北理工大学矿业工程学院河北唐山063210

鄂西宜昌地区下寒武统水井沱组页岩是近年来我国南方页岩气勘探的重点层位之一。为解决实验室储层测试资料相对有限的约束,本研究基于地层元素测井资料建立一套鄂西宜昌地区下寒武统水井沱组页岩储层参数解释方法,进而为储层评价提供依... 详细信息

鄂西宜昌地区下寒武统水井沱组页岩是近年来我国南方页岩气勘探的重点层位之一。为解决实验室储层测试资料相对有限的约束,本研究基于地层元素测井资料建立一套鄂西宜昌地区下寒武统水井沱组页岩储层参数解释方法,进而为储层评价提供依据。基于地层元素测井数据和实验室测试X射线衍射数据,建立了储层矿物组分类型及含量元素测井解释模型,误差性分析结果显示解释的岩石矿物含量与岩心测试矿物含量具有良好的相关性(黏土矿物R为0.7813,碳酸盐矿物R为0.7859,硅质矿物R为0.738),利用元素开展的矿物含量解释具有较高的准确度。基于矿物组分解释开展了水井沱组岩相类型划分,总体上岩相组合变化与相对海平面变化具有良好相关性,高灰质含量页岩类型对应于水体相对较浅环境。利用矿物组分解释模型,建立水井沱组页岩脆性矿物组分指数计算方法,对水井沱组页岩脆性进行了综合评价,结果与页岩弹性参数脆性评价结果具有良好一致性。总体上基于地层元素测井解释的矿物组分结果可为鄂西宜昌地区下寒武统水井沱组页岩储层岩相划分、储层甜点识别、压裂段优选等提供参照,对区域内储层评价与勘探开发具有良好指导意义。

关键词：页岩储层元素俘获能谱测井储层评价宜昌地区

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用于VSLAM系统的CNN在FPGA平台上的加速

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计算机工程与设计 2024年第1期45卷 71-78页

作者：郁媛李沛君王光奇张德兵张春清华大学集成电路学院北京100084

为实现视觉同步定位与建图系统中卷积神经网络在FPGA上的加速,基于SuperPoint模型设计一种低功耗高效CNN加速器及相应的SoC系统。采用循环分块、数据复用、计算单元展开和双缓冲策略充分利用加速器的片上资源;为提高突发传输效率,预先... 详细信息

为实现视觉同步定位与建图系统中卷积神经网络在FPGA上的加速,基于SuperPoint模型设计一种低功耗高效CNN加速器及相应的SoC系统。采用循环分块、数据复用、计算单元展开和双缓冲策略充分利用加速器的片上资源;为提高突发传输效率,预先对权重参数重排;提出Pack模块和Unpack模块,设计多通道数据传输,用于提高传输带宽。在Ultra96-V2 FPGA平台上部署整个SoC系统,在仅3 W左右的功耗下实现25.63 GOPS的吞吐量,其BRAM效率、DSP效率、性能密度和功耗效率相比之前的文献有明显优势。

关键词：同步定位与建图系统图像处理卷积加速数据复用并行计算突发传输软硬件协作

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Soil Quality Degradation in a Magnesite Mining Area

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Pedosphere 2011年第1期21卷 98-106页

作者： FU Sha-Sha li pei-jun FENG Qian li Xiao-jun li Peng SUN Yue-Bing CHEN Yang Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 (China) Graduate University of the Chinese Academy of Sciences Beijing 100049 (China) Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences Fuzhou 350002 (China) Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 (China)

Fourteen soil properties in 17 sampling sites were analyzed to study the soil degradation in a magnesite mining area in Halcheng City, Northeast China. Such areas have hitherto received little attention. The current practices of magnesite mining in this area resulted in degradation of soil quality and specifically led to an increase in soil pH, the ratio of magnesium to calcium, bulk density, clay dispersibility, total magnesium and equivalent calcium carbonate and a decrease in surface soil porosity and available phosphorous. The soil quality in the areas affected by intensive mining activity was obviously worse than that of areas far away from the mine. Four factors were identified and ＂magnesium factor＂, ＂pH factor＂ and ＂fertility factor＂, involving 13 soil properties, explained 82~0 of the total variance in the entire data set. Discriminant analysis showed that the total magnesium, water-soluble calcium and available phosphorous were the most sensitive indicators for soil quality.

关键词： discriminant analysis factor analysis magnesite processing soil degradation

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Removal of heavy metals from a contaminated soilusing tartaric acid

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Journal of Environmental Sciences 2006年第4期18卷 727-733页

作者： KE Xin li pei-jun ZHOU Qi-xing ZHANG Yun SUN Tie-heng Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 China Graduate School of the Chinese Academy of Sciences Beijing 100039 China Shenyang Agriculture University Shenyang 110161 China

This study reports the feasibility of remediation of a heavy metal （HM） contaminated soil using tartaric acid, an environmentally-friendly extractant. Batch experiments were performed to test the factors influencing remediation of the HM contaminated soil. An empirical model was employed to describe the kinetics of riM dissolution/desorption and to predict equilibrium concentrations of HMs in soil leachate. The changes of HMs in different fractions before and after tartaric acid treatment were also investigated. Tartaric acid solution containing HMs was regenerated by chestnut shells. Results show that utilization of tartaric acid was effective for removal of riMs from the contaminated soil, attaining 50%-60% of Cd, 40%-50% of Pb, 40%-50% of Cu and 20%-30% of Zn in the pH range of 3.5-4.0 within 24 h. Mass transfer coefficients for cadmium （Cd） and lead （Pb） were much higher than those for copper （Cu） and zinc （Zn）. Sequential fractionations of treated and untreated soil samples showed that tartaric acid was effective in removing the exchangeable, carbonate fractions of Cd, Zn and Cu from the contaminated soil. The contents of Pb and Cu in Fe-Mn oxide fraciton were also significantly decreased by tartaric acid treatment. One hundred milliliters of tartaric acid solution containing HMs could be regenerated by 10 g chestnut shells in a batch reactor. Such a remediation procedure indicated that tartaric acid is a promising agent for remediation of HM contaminated soils. However, further research is needed before the method can be practically used for in situ remediation of contaminated sites.

关键词： tartaric acid soil remediation heavy metals soil contamination

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Growth, Cadmium Accumulation and Physiology of Marigold (Tagetes erecta L.) as Affected by Arbuscular Mycorrhizal Fungi

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Pedosphere 2011年第3期21卷 319-327页

作者： liU ling-Zhi GONG Zong-Qiang ZHANG Yu-Long li pei-jun Shenyang Agricultural University Shenyang 110866 (China) Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 (China)

A pot experiment was carried out to study the effects of three arbuscular mycorrhizal fungi （AMF）, including Glomus intraradices, Glomus constrictum and Glomus mosseae, on the growth, root colonization and Cd accumulation of marigold （Tagetes erecta L.） at Cd addition levels of 0, 5 and 50 mg kg-1 in soil. The physiological characteristics, such as chlorophyll content, soluble sugar content, soluble protein content and antioxidant enzyme activity, of Tagetes erecta L. were also investigated. The symbiotic relationship between the marigold plant and arbuscular mycorrhizal fungi was well established under Cd stress. The symbiotic relationship was reflected by the better physiobiochemical parameters of the marigold plants inoculated with the three AMF isolates where the colonization rates in the roots were between 34.3% and 88.8%. Compared with the non-inoculated marigold plants, the shoot and root biomass of the inoculated marigold plants increased by 15.2%- 47.5% and 47.8%-130.1%, respectively, and the Cd concentration and accumulation decreased. The chlorophyll and soluble sugar contents in the mycorrhizal marigold plants increased with Cd addition, indicating that AMF inoculation helped the marigold plants to grow by resisting Cd stress. The antioxidant enzymes reacted differently with the three AMF under Cd stress. For plants inoculated with G. constrictum and G. mosseae, the activities of superoxide dismutase （SOD） and catalase （CAT） increased with increasing Cd addition, but peroxidase （POD） activity decreased with increasing Cd addition. For plants inoculated with G. intraradices, three of the antioxidant enzyme activities were significantly decreased at high levels of Cd addition. Overall, the activities of the three antioxidant enzymes in the plants inoculated with AMF were higher than those of the plants without AMF inoculation under Cd stress. Our results support the view that antioxidant enzymes have a great influence on the biomass of plants, and AMF can

关键词： antioxidant enzyme Cd stress metal accumulation phytoremediation root colonization

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Degradation of metabolites of benzo[a]pyrene by coupling Penicillium chrysogenum with KMnO_4

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Journal of Environmental Sciences 2007年第2期19卷 238-243页

作者： ZANG Shu-yan li pei-jun YU Xiao-cai SHI Kun ZHANG Hui CHEN Jing Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 China Shenyang Institute of Chemical Technology Shenyang 110142 China Graduate School of Chinese Academy of Sciences Beijing 100039 China Environment Science and Engineering School Dalian Jiaotong University Dalian 116028 China Northeast University Shenyang 110006 China

Several main metabolites of benzo[a]pyrene （BaP） formed by Penicillium chrysogenum, Benzo[a]pyrene-1,6-quinone （BP 1,6- quinone）, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene （BP 7,8-diol）, 3-hydroxybenzo[a]pyrene （3-OHBP）, were identified by high-performance liquid chromatography （HPLC）. The three metabolites were liable to be accumulated and were hardly further metabolized because of their toxicity to microorganisms. However, their further degradation was essential for the complete degradation of BaP. To enhance their degradation, two methods, degradation by coupling Penicillium chrysogenum with KMnO4 and degradation only by Penicillium chrysogenum, were compared; Meanwhile, the parameters of degradation in the superior method were optimized. The results showed that （1） the method of coupling Penicillium chrysogenum with KMnO4 was better and was the first method to be used in the degradation of BaP and its metabolites; （2） the metabolite, BP 1,6-quinone was the most liable to be accumulated in pure cultures; （3） the effect of degradation was the best when the concentration of KMnO4 in the cultures was 0.01% （w/v）, concentration of the three compounds was 5 mg/L and pH was 6.2. Based on the experimental results, a novel concept with regard to the bioremediation of BaP-contaminated environment was discussed, considering the influence on environmental toxicity of the accumulated metabolites.

关键词： BaP metabolites accumulated coupling potassium permanganate

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