检索结果-南通市图书馆

A high-resolution late Pleistocene record of pollen vegetation and climate change from Jingning, NW china

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

science china Earth sciences 2006年第2期49卷 154-162页

作者： LI Chunhai12, TANG Lingyu1, FENG Zhaodong3,4, ZHANG Hucai2, WANG Weiguo3 & AN Chenbang3 1. nanjing Institute of Geology and Palaeontology, Chinese Academy of sciences, nanjing 210008, china 2. Nanjng Institute of Geography and Limnology, Chinese Academy of sciences, nanjing 210008, china 3. Environment and resources college, Lanzhou university, Lanzhou 730000, china 4. Beijing Normal university, Beijing 100875, china nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences Nanjing China Nanjng Institute of Geography and Limnology Chinese Academy of Sciences Nanjing China Environment and resources college Lanzhou University Lanzhou China Beijing Normal university Beijing China

With the support of 18 AMS-14C data, a high-resolution pollen record from the Suancigou section at Jingning, Gansu Province was established. Our results showed that the vegetation ex-perienced a series of changes characterized by the alternative growth and decline of forest and steppe components during the period from 44.2 to 11 ka B.P. in the Jingning area. Over the period of 44―29 ka B.P. (MIS3), coniferous forests were flourishing, indicating a humid climate with the tem-perature being lower than that of the present. Since 23 ka B.P., the vegetation was dominated by steppe-desert steppe under a cold and dry condition, and entered the Last Glacial Maximum domi-nated by desert steppe. Several periods of the marked decrease in the arborous pollen content in Suancigou well corresponded to the North Atlantic Heinrich events, especially to Heinrich event 3, further supporting that the Heinrich events were well reflected by the pollen record in the Loess Pla-teau as well.

关键词： Western Loess Plateau, pollen record, climatic change, late Pleistocene.

Sufficient and necessary conditions for Lyapunov stability of Lorenz system and their application

在线全文

学校读者我要写书评

暂无评论

science china(Information sciences) 2010年第8期53卷 1574-1583页

作者： LUO Qi 1 , LIAO XiaoXin 2 & ZENG ZhiGang 2 1 college of Information and Control, nanjing university of Information science and Technology, nanjing 210044, china 2 Department of Control science and Engineering, Huazhong university of science and Technology, Image Processing and Intelligent Control Key Laboratory of Education Ministry of china, Wuhan 430074, china college of Information and Control Nanjing University of Information Science and Technology Nanjing China Department of Control science and Engineering Huazhong University of Science and Technology Image Processing and Intelligent Control Key Laboratory of Education Ministry of China Wuhan China

The sufficient and necessary conditions for Lyapunov stability of the zero equilibrium point of Lorenz system are discussed, and some brief criteria are presented for globally exponential stability, globally asymptotical stability and instability. Furthermore, the behavior of the non-zero equilibrium point of Lorenz system is also investigated, and several sufficient and necessary conditions are provided for locally exponential stability and instability. The established theorems in this paper develop and extend the existing achievements on Lyapunov stability of Lorenz system. In conclusion, by applying the obtained results, some less conservative feedback-control laws are derived to guarantee the globally exponential stability of the chaos control of Chen system, Lu¨ system, Yang-Chen system and Yu-Xia Li system.

关键词： Lorenz system Lyapunov stability sufficient and necessary condition bifurcation values globally exponential synchronization

Travelling wave solutions of a generalized Camassa-Holm-Degasperis-Procesi equation

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

science china Mathematics 2011年第3期54卷 555-572页

作者： DENG ShengFu1, GUO BoLing2 & WANG TingChun2,3 1Department of Mathematics, Zhanjiang Normal university, Zhanjiang 524048, china 2Institute of Applied Physics and Computational Mathematics, Beijing 100088, china 3 college of Math and Physics, nanjing university of Information science and Technology, nanjing 210044, china Department of Mathematics Zhanjiang Normal University Zhanjiang China Institute of Applied Physics and Computational Mathematics Beijing China college of Math and Physics Nanjing University of Information Science and Technology Nanjing China

The travelling wave solutions of a generalized Camassa-Holm-Degasperis-Procesi equation ut-uxxt + (1 + b)umux = buxuxx + uuxxx are considered where b > 1 and m are positive integers. The qualitative analysis methods of planar autonomous systems yield its phase portraits. Its soliton wave solutions, kink or antikink wave solutions, peakon wave solutions, compacton wave solutions, periodic wave solutions and periodic cusp wave solutions are obtained. Some numerical simulations of these solutions are also given.

关键词： homoclinic orbits heteroclinic orbits peakon wave solutions compacton wave solutions periodic cusp wave solutions

Facile Synthesis of Nanocrystalline Cr_2O_3 Thin Film

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan university of Technology(Materials science) 2011年第6期26卷 1032-1035页

作者：杨明 School of Transportation Southeast University

A novel and facile synthesis route for the manufacture of transparent and uniform self-assembled nanocrystalline Cr2O3 （nc-Cr2O3） thin films with different morphology was reported, utilizing chromium nitrate as the inorganic source and triblock copolymer F127 as the morphology-directing agent by the evaporation-induced assembly （EIA） method. X-ray powder diffraction （XRD）, thermogravimetry-differential scanning calorimetry （TG-DSC）, N2-sorption, scanning electron microscopy （SEM） and transmission electron microscopy （TEM） were used to characterize the as-prepared nc-Cr2O3 thin films. The Cr2O3 thin film with different morphology was obtained by changing the relative humidity. The possible formation mechanism of the nc-Cr2O3 thin films with different morphologies was discussed.

关键词： microstrucmre Cr2O3 thin film

Hydroisomerization of n-heptane over bimetal-bearing H_3PW_(12)O_(40) catalysts supported on dealuminated USY zeolite

在线全文

学校读者我要写书评

暂无评论

science china Chemistry 2008年第2期51卷 120-127页

作者： WEI RuiPing1,2, GU YanBo1 & WANG Jun1 1 State Key Laboratory of Materials-Oriented Chemical Engineering, college of Chemistry and Chemical Engineering, nanjing Uni- versity of Technology, nanjing 210009, china 2 college of Chemistry and Chemical Engineering, Southeast university, nanjing 211189, china State Key Laboratory of Materials-Oriented Chemical Engineering College of Chemistry and Chemical Engineering Nanjing University of Technology Nanjing China college of Chemistry and Chemical Engineering Southeast University Nanjing China

The bimetal-bearing (CePt or LaPt) 12-tungstophosphoric acid (H3PW12O40 (PW)) catalysts supported on dealuminated USY zeolite (DUSY) were prepared by impregnation and characterized by XRD, BET, IR, and H2-chemisorption. Their catalytic activities were tested in the hydroisomerization of n-heptane with a continuous atmospheric fixed-bed reactor. After the steam treatment combined with the acid leaching, as well as the supporting with PW and the bimetals, the DUSY support retains the Y zeolite porosity and the PW well keeps its Keggin structure in catalysts. The doping of Ce into the catalysts enhances the dispersion of Pt on the catalyst surface. The Pt-bearing PW catalysts doped with Ce or La, especially Ce, exhibit much higher catalytic activity and selectivity than the catalysts without dopants at lowered reaction temperatures. At the optimal reaction conditions, i.e., the reaction temperature of 250℃ and WHSV of 1.4 h1, the catalyst with a Pt loading of 0.4%, PW loading of 10% and a molar ratio of Ce to Pt of 15:1 shows a conversion of n-heptane of 70.3% with a high selectivity for isomerization products of 94.1%.

关键词： hydroisomerization of n-heptane bimetal catalyst heteropoly acid USY platinum

Effects of coffee and caffeine on bladder dysfunction in streptozotocininduced diabetic rats

在线全文

学校读者我要写书评

暂无评论

Acta Pharmacologica Sinica 2006年第8期27卷 1037-1043页

作者： Chao-ran YI~(2,5) Zhong-qing WEI~2 Xiang-lei DENG~4 Ze-yu SUN~2 Xing-rong LI~4 Cheng-gong TIAN~3 ~2Department of Urology,~3Department of Endocrinology,the Affiliated Drum Tower Hospital,nanjing university Medical School,nanjing 210008,china ~4Department of Biochemisto,and Molecular Biology,Medieal college of Southeast university,nanjing 210009,china Department of Urology the Affiliated Drum Tower Hospital Nanjing University Medical School Nanjing China Department of Biochemistry and Molecular Biology Medical College of Southeast University Nanjing China Department of Endocrinology the Affiliated Drum Tower Hospital Nanjing University Medical School Nanjing China

Aim:To explore the effects and mechanisms of caffeine and coffee on bladderdysfunction in streptozotocin-induced diabetic ***:Sprague-Dawleymale rats were divided randomly into 4 groups:control,diabetes mellitus(DM),DM with coffee treatment,and DM with caffeine *** diabetic rat wasinduced by intraperitoneal injection of streptozotocin(60 mg/kg).After 7 weeks oftreatment with coffee and caffeine,cystometrogram,contractile responses to elec-trical field stimulation(EFS)and acetylcholine(ACh),and cyclic AMP(cAMP)concentration of the bladder body and base were ***:The bladderweight,volume threshold for micturition and post-void residual volume(PVR)inthe diabetic rats were significantly higher compared to those in the control *** or caffeine treatment significantly reduced the bladder weight,bladdercapacity and PVR in the diabetic *** caused significant decreases in cAMPconcentration of the bladder and coffee and caffeine caused upregulation of cAMPcontent in the diabetic *** addition,coffee and caffeine tended to normal-ize the altered detrusor contractile responses to EFS and ACh in the diabetic ***:These results indicate that caffeine and coffee may have beneficialeffects on bladder dysfunction in the early stage of diabetes by increasing cAMPcontent in the lower urinary tract,recovering the micturition reflex and improvingthe detrusor contractility.

关键词： caffeine diabetic mellitus bladder urodynamics muscle contraction cyclic AMP

Responses of soil nutrient to driving mechanism in Taihu Lake basin in last 20 years

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Geographical sciences 2001年第1期11卷 92-98页

作者： CHEN Fu, PENG Bu-zhuo, BAO Hao-sheng (Department of Urban and resources science, nanjing university, nanjing 210093, china) Department of Urban and resources science Nanjing University Nanjing China

The objectives of this study is to understand the changing law of soil nutrient quality in Taihu Lake basin, Yangtze Delta in last 20 years, and reveal the relationship between soil nutrient changes and human driving forces in regional level over long period of time. Experiment on long-term collecting samples was conducted to study changes of soil organic matter, total N, available N, available P and available K in Dongting town, Wuxi city during the last 20 years. The paper analyses the co-relationship of the fluctuation of soil nutrient and state policy, cultivating practice, agricultural input, and per hectare agricultural net income. The results showed that at first the content of soil organic matter increased, then decreased, and increased again. The content of total N and available N steadily increased. The content of available K and available P steadily decreased. The authors found that the influence of state policy and cultivating practice on soil nutrient quality index (SNQI) is obvious, agricultural input and SNQI are positively correlated, and per hectare agricultural net income and SNQI are negatively correlated.

关键词： soil nutrient SNQI human driving mechanism Taihu Lake basin

An exploration for the macroscopic physical meaning of entropy

在线全文

学校读者我要写书评

暂无评论

science china(Technological sciences) 2010年第7期53卷 1809-1816页

作者： WU Jing1 & GUO ZengYuan2 1 college of Energy and Power Engineering, nanjing university of Aeronautics and Astronautics, nanjing 210016, china 2 Key Laboratory for Thermal science and Power Engineering of Ministry of Education, School of Aerospace, Tsinghua university, Beijing 100084, china college of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics Nanjing China Key Laboratory for Thermal science and Power Engineering of Ministry of Education School of Aerospace Tsinghua University Beijing China

The macroscopic physical meaning of entropy is analyzed based on the exergy (availability) of a combined system (a closed system and its environment), which is the maximum amount of useful work obtainable from the system and the environment as the system is brought into equilibrium with the environment. The process the system experiences can be divided in two sequent sub-processes, the process at constant volume, which represents the heat interaction of the system with the environment, and the adiabatic process, which represents the work interaction of the system with the environment. It is shown that the macroscopic physical meaning of entropy is a measure of the unavailable energy of a closed system for doing useful work through heat interaction. This statement is more precise than those reported in prior literature. The unavailability function of a closed system can be defined as T0S and p0V in volume constant process and adiabatic process, respectively. Their changes, that is, AiTgS) and A (p0V) represent the unusable parts of the internal energy of a closed system for doing useful work in corresponding processes. Finally, the relation between Clausius entropy and Boltzmann entropy is discussed based on the comparison of their expressions for absolute entropy.

关键词： entropy macroscopic physical meaning exergy heat interaction

Field experiments on greenhouse gas emissions and nitrogen and phosphorus losses from rice paddy with efficient irrigation and drainage management

在线全文

学校读者我要写书评

暂无评论

science china(Technological sciences) 2011年第6期54卷 1581-1587页

作者： PENG ShiZhang1,2,YANG ShiHong1,2,XU JunZeng1,2 & GAO HuanZhi1,2 1State Key Laboratory of Hydrology-Water resources and Hydraulic Engineering,Hohai university,nanjing 210098,china 2college of Water Conservancy and Hydropower Engineering,Hohai university,nanjing 210098,china State Key Laboratory of Hydrology-Water resources and Hydraulic Engineering Hohai University Nanjing China college of Water Conservancy and Hydropower Engineering Hohai University Nanjing China

Greenhouse gas emissions,nitrogen and phosphorous losses through ammonia volatilization,leaching and surface drainage from rice paddy under efficient irrigation and drainage were analyzed based on field experimental data in order to reveal the eco-environmental impacts of efficient irrigation and drainage on rice *** results showed that total methane emission from rice paddy under the controlled irrigation was reduced by more than 80% and total nitrous oxide emission increased by 15.9% compared with flooding *** comprehensive global warming potentials(GWP) of methane and nitrous oxide were 62.23 gCO2 m-2 for rice paddy under the controlled irrigation,reduced by 68.0% compared with flooding *** to large reduction in seepage and surface drainages,nitrogen and phosphorous losses through leaching were reduced by 40.1% and 54.8%,nitrogen and phosphorous losses through surface drainage were reduced by 53.9% and 51.6% from rice paddy under efficient irrigation and drainage compared with traditional irrigation and *** loss through ammonia volatilization was reduced by 14.0%.Efficient irrigation and drainage management is helpful to mitigate greenhouse gases emission,nitrogen and phosphorus losses and their pollution on groundwater and surface water.

关键词： efficient irrigation and drainage nitrogen and phosphorus greenhouse gas ammonia volatilization paddy field