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Extinction and persistence of a nonautonomous stochastic food-chain system with impulsive perturbations

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International Journal of Biomathematics 2016年第5期9卷 217-242页

作者： Baodan tian Shouming zhong Zhijun Liu ＊Institute of Modeling and Algorithm School of Science Southwest University of Science and Technology Mianyang 621010 P. R. China School of Mathematical Sciences University of Electronic Science and Technology of China Chengdu 611731 P. R. China School of Science Hubei University for Nationalities Enshi 445000 P. R. China

In this paper, a nonautonomous stochastic food-chain system with functional response and impulsive perturbations is studied. By using Ito＇s formula, exponential martingale inequality, differential inequality and other mathematical skills, some sufficient conditions for the extinction, nonpersistence in the mean, persistence in the mean, and stochastic permanence of the system are established. Furthermore, some asymptotic properties of the solutions are also investigated. Finally, a series of numerical examples are presented to support the theoretical results, and effects of different intensities of white noises perturbations and impulsive effects are discussed by the simu｜ations.

关键词： Food-chain system functional response stochastic perturbations impulsive effects extinction stochastic permanence.

An integrated nanocarbon–cellulose membrane for solid-state supercapacitors

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Science Bulletin 2016年第5期61卷 368-377页

作者： Huabo Liu Yuheng tian Rose Amal da-Wei Wang School of Chemical Engineering The University of New South Wales

In this work, we demonstrate the assembly of oxidised carbon nanohybrids(o CNHs) with a commercial cellulose membrane for solid-state supercapacitors. The o CNHs–cellulose membranes were prepared by filtering a water dispersion of o CNHs through the cellulose membrane. The o CNHs were derived from carbon nanotubes via a modified Hummer's method and contained both closed tubes and unzipped tubes, which indicated a hybrid geometrical structure. The solid-state supercapacitor based on the o CNHs–cellulose membranes showed a high areal capacitance of *75 m F/cm^2 at a low scan rate(5 m V/s)and excellent stability for 1,000 cycles.

关键词： Solid-state supercapacitors Carbon nanotubes Membrane

Novel Propagation Properties of Total Internal Reflection Photonic Crystal Fibres with Rhombic Air Holes

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Chinese Physics Letters 2011年第11期28卷 135-137页

作者： YAN Hai-Feng YU zhong-Yuan LIU Yu-Min tian Hong-da HAN Li-Hong Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and TelecommunicationsMinistry of EducationBeijing 100876

We investigate the propagation properties of a multi-layer photonic crystal fiber with novel rhombic air holes using the finite element method,and calculate the dependence of the propagation properties on the wavelength in the fiber with different geometrical structural parameters,including the internal angle and the external arrangement of the rhombic air *** these parameters,we design a photonic crystal which exhibits both a small dispersion value and low loss near the wavelength of 1.55μm.

关键词： fiber Crystal arrangement

Hybrid Modeling for Soft Sensing of Molten Steel Temperature in LF

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Journal of Iron and Steel Research International 2009年第4期16卷 1-6页

作者： tian Hui-xin MAO Zhi-zhong WANG An-na School of Electrical and Automation Engineering Tianjin Polytechnic University Tianjin 300160 China School of Information Science and Engineering Northeastern University Shenyang 110004 Liaoning China Key Laboratory of Integrated Automation of Process Industry of Ministry of Education NortheasternUniversity Shenyang 110004 Liaoning China

Aiming at the limitations of traditional thermal model and intelligent model, a new hybrid model is established for soft sensing of the molten steel temperature in LF. Firstly, a thermal model based on energy conservation is described; and then, an improved intelligent model based on process data is presented by ensemble ELM （extreme learning machine） for predicting the molten steel temperature in LF. Secondly, the self-adaptive data fusion is pro- posed as a hybrid modeling method to combine the thermal model with the intelligent model. The new hybrid model could complement mutual advantage of two models by combination. It can overcome the shortcoming of parameters obtained on-line hardly in a thermal model and the disadvantage of lacking the analysis of ladle furnace metallurgical process in an intelligent model. The new hybrid model is applied to a 300 t LF in Baoshan Iron and Steel Co Ltd for predicting the molten steel temperature. The experiments demonstrate that the hybrid model has good generalization performance and high accuracy.

关键词： ladle furnace hybrid modeling soft sensing thermal model data fusion

Tourism Competitiveness Evaluation and Spatio-temporal Characteristics of Chinese Border Counties

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Chinese Geographical Science 2016年第6期26卷 817-828页

作者： SHI Yuqing zhong Linsheng CHEN tian YU Hu Institute of Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

Under the current government strategy of building a Silk Road economic belt, tourism in Chinese border counties has becoming increasingly popular. Studying tourism competitiveness in Chinese border counties is of sizable theoretical and practical importance, as there are several notable factors involved. In this study, we constructed a tourism competitiveness evaluation model based on eight factors: natural environment, tourism resource, location and transportation, social environment, tourism service facility, border port, tourism industrial cluster and tourism market. We then analyzed the spatial characteristics of tourism competitiveness in border counties and identified five types of border counties: resource advantage type(RA), border-port advantage type(PA), location advantage type(LA), agglomeration advantage type(AA), and relative balance type(RB), and examined the correlation between tourism market competitiveness and interior competitiveness factors in the counties from 2006 to 2011. Results showed that tourism resource, location and transportation, and tourism service facility are the most important competition factors for RA border counties during the study period. Competition factors in PA counties transferred from tourism resource, social environment and tourism service facility to border port and tourism industrial cluster; competition factors in LA counties transferred from natural environment and tourism resource to tourism service facility and tourism industrial cluster and border port. Competition factors in AA counties transferred from tourism service facility to tourism resource. Tourism industrial cluster, tourism service facility and tourism resource proved to be important competition factors in RB counties. The findings of this study can be used to target tourism strategies according to different county types.

关键词： border counties tourism competiveness spatio-temporal characteristics type classification

Energy dissipation in atomic-scale friction

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Friction 2013年第1期1卷 24-40页

作者： Yuan-zhong HU tian-bao MA Hui WANG State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China

The mechanisms of energy dissipation are discussed in this paper by reviewing the models and research in atomic-scale *** study is undertaken to answer a fundamental question in the study of friction:How is frictional work dissipated,particularly in cases where material damage and wear are not *** initiation of energy dissipation,the role of structural commensurability,and the estimation of the interfacial shear strength have been examined in detail by introducing the Tomlinson model,the Frenkel-Kontorova model,and the cobblestone model,*** discussion is extended to energy dissipation progress described in terms of phononic and electronic *** contributions from other mechanisms of dissipation such as viscoelastic relaxation and material wear are also *** an example,we analyzed a specific process of dissipation in multilayer graphene,on the basis of results of molecular dynamics(MD)simulations,which reveal a reversible part of energy that circulates between the system and the external *** leads us to emphasize that it is crucial in future studies to clearly define the coefficient of dissipation.

关键词： energy dissipation atomic-scale friction phononic damping viscoelastic relaxation

A new protoberberine alkaloid from Corydalis yanhusuo ***

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Chinese Chemical Letters 2009年第8期20卷 955-957页

作者： tian tian Hu Xue Zhang Shi zhong Ma Xin Sheng Yao School of Traditional Chinese Materia Medica Shenyang Pharmaceutical University Shenyang 110016 China

A new protoberberine alkaloid, named 5,6-dihydro- 10-hydroxy-2,3,9-trimethoxy- 13-methyldibenzo[α,g]quinoliziniurn （1） was isolated from the 60% ethanol extract of the tubers of Corydalis yanhusuo W. T. Wang, together with a new natural product, 13methylpalmatrubine （2）. Their structures were established by spectroscopic methods. 2009 Xin Sheng Yao. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All fights reserved.

关键词： Corydalis yanhusuo W. T. Wang Protoberberine alkaloid 13-Methylpalmatrubine

Free-surface air entrainment in open-channel flows

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Science China(Technological Sciences) 2017年第6期60卷 893-901页

作者： WEI WangRu XU WeiLin DENG Jun tian zhong ZHANG FaXing State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University Chengdu 610065 China

In hydraulic engineering,free-surface aeration is a natural phenomenon occurring in smooth channel *** self-aerated flows,a key aspect that has not yet been well understood is the formation mechanism of free-surface air *** this research,the process of free-surface entrapped deformation is analyzed theoretically and the critical radius of curvature for air entrainment is obtained,affected by flow mean velocity and *** the severity of local free-surface deformation exceeds the critical condition,the entrapped free surface encounters closure in the unstable deformation movement process,resulting in air *** inference agrees well with observed experimental results that are obtained from the processes of surface entrapped deformation and air entrainment captured by a high-speed camera-based data acquisition *** agreement indicates that self-aeration occurs in low-velocity open-channel *** is also confirmed that free-surface turbulent deformation provides a mechanism for air entrainment.

关键词： hydraulic engineering self-aeration turbulence free surface open-channel flows

PRESSURE FLUCTUATIONS BENEATH SPATIAL HYDRAULIC JUMPS

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Journal of Hydrodynamics 2006年第6期18卷 723-726页

作者： YAN zhong-min ZHOU Chun-tian LU Shi-qiang College of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 China Shanghai Academy of Environmental Sciences Shanghai 200233 China

This article deals with statistical analysis of pressure fluctuations at the bottom of spatial hydraulic jumps with abrupt lateral expansions. The effects of the channel expansion ratio and inflow condition on the power spectral and dominant frequency were examined. Pressure data were recorded for different Froude numbers ranging from 3.52 to 6.86 and channel expansion ratios ranging from 1.5 to 3.0. A sampling frequency of 100 Hz was selected. The measurements were conducted in the bed of a glass-walled laboratory flume by means of pressure transducers and data acquisition systems. Power spectra as well as dominant frequency and some other statistical characteristics of fluctuating pressure beneath hydraulic jumps were obtained. Test results were compared with those of classical jump, which indicates that the peak frequencies and intensity coefficients of pressure fluctuations are higher than those of the corresponding classical jumps.

关键词： spatial hydraulic jumps pressure fluctuation,stochastic analysis frequency amplitude