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Search Results: 1 - 10 of 104268 matches for " Chaofeng Zhang "
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Chaos Control in a Discrete Ecological System  [PDF]
Limin Zhang, Chaofeng Zhang
International Journal of Modern Nonlinear Theory and Application (IJMNTA) , 2012, DOI: 10.4236/ijmnta.2012.13011
Abstract: In research [1], the authors investigate the dynamic behaviors of a discrete ecological system. The period-double bifurcations and chaos are found in the system. But no strategy is proposed to control the chaos. It is well known that chaos control is the first step of utilizing chaos. In this paper, a controller is designed to stabilize the chaotic orbits and enable them to be an ideal target one. After that, numerical simulations are presented to show the correctness of theoretical analysis.
Dynamics of a Hyperparasitic System with Prolonged Diapause for Host*  [PDF]
Limin Zhang, Chaofeng Zhang
International Journal of Modern Nonlinear Theory and Application (IJMNTA) , 2013, DOI: 10.4236/ijmnta.2013.24028
Abstract:

A hyperparasitic system with prolonged diapause for host is investigated. It is assumed that host prolonged diapause occur at larval stage, and parasitoid attack is limited to egg stage before the initiation of host diapause. Such behavior has been reported for many ichneumons. Hyperparasite only attacks the parasitoids that parasitize the hosts. Hyperparasitic system is often used in biological control. The existence and stability of nonnegative fixed points are explored. Numerical simulations are carried out to explore the global dynamics of the system, which demonstrate appropriate prolonged diapause rate and appropriate intrinsic growth rate can stabilize the system. The reasons are explained according to the ecological perspective. Furthermore, many other complexities which include quasi-periodicity, period-doubling bifurcations leading to chaos, chaotic attractor, intermittent and supertransients are observed.

Permanence, Periodicity and Extinction of a Delayed Biological System with Stage-Structured Preference for Predator  [PDF]
Limin Zhang, Chaofeng Zhang
Journal of Applied Mathematics and Physics (JAMP) , 2016, DOI: 10.4236/jamp.2016.43060
Abstract: This study considers a delayed biological system of predator-prey interactions where the predator has stage-structured preference. It is assumed that the prey population has two stages: immature and mature. The predator population has different preference for the stage-structured prey. This type of behavior has been reported in Asecodes hispinarum and Microplitis mediator. By some lemmas and methods of delay differential equation, the conditions for the permanence, existence of positive periodic solution and extinction of the system are obtained. Numerical simulations are presented that illustrate the analytical results as well as demonstrate certain biological phenomena. In particular, overcrowding of the predator does not affect the persistence of the system, but our numerical simulations suggest that overcrowding reduces the density of the predator. Under the assumption that immature prey is easier to capture, our simulations suggest that the predator’s preference for immature prey increases the predator density.
New Asymptotical Stability and Uniformly Asymptotical Stability Theorems for Nonautonomous Difference Equations  [PDF]
Limin Zhang, Chaofeng Zhang
Applied Mathematics (AM) , 2016, DOI: 10.4236/am.2016.710089
Abstract: New theorems of asymptotical stability and uniformly asymptotical stability for nonautonomous difference equations are given in this paper. The classical Liapunov asymptotical stability theorem of nonautonomous difference equations relies on the existence of a positive definite Liapunov function that has an indefinitely small upper bound and whose variation along a given nonautonomous difference equations is negative definite. In this paper, we consider the case that the Liapunov function is only positive definite and its variation is semi-negative definite. At these weaker conditions, we put forward a new asymptotical stability theorem of nonautonomous difference equations by adding to extra conditions on the variation. After that, in addition to the hypotheses of our new asymptotical stability theorem, we obtain a new uniformly asymptotical stability theorem of nonautonomous difference equations provided that the Liapunov function has an indefinitely small upper bound. Example is given to verify our results in the last.
Uniform Persistence, Periodicity and Extinction in a Delayed Biological System with Stage Structure and Density-Dependent Juvenile Birth Rate  [PDF]
Limin Zhang, Chaofeng Zhang
American Journal of Computational Mathematics (AJCM) , 2016, DOI: 10.4236/ajcm.2016.62014
Abstract: A delayed biological system of predator-prey interaction with stage structure and density dependent juvenile birth rate is investigated. It is assumed that the prey population has two stages: immature and mature. The growth of the immature prey is density dependent and is a function of the density of adult prey. Such phenomenon has been reported for beetles, tribolium, copepods, scorpions, several fish species and even crows. The growth of the predator is affected by the time delay due to gestation. By some Lemmas and methods of delay differential equation, the conditions for the uniform persistence and extinction of the system are obtained. Numerical simulations illustrate the feasibility of the main results and demonstrate that the density dependent coefficient has influence on the system populations’ densities though it has no effect on uniform persistence and extinction of the system.
β-Hausdorff Operator on Lipschitz Space in the Unit Polydisk  [PDF]
Rong Hu, Chaofeng Zhang
Advances in Pure Mathematics (APM) , 2014, DOI: 10.4236/apm.2014.45022
Abstract:

In this paper, we define β-Hausdorff operator on the unit polydisk and study the boundedness of the operator on Lipschitz space. Firstly, we translate the problem of coefficient into integral of weighted composition operator, then give the sufficient conditions of boundedness, and also obtain an upper bound for the operator norm on Lipschitz space.

An Empirical Study on Fuzzy Comprehensive Evaluation of Red Tourism Resources Based on AHP  [PDF]
Rong Hu, Chaofeng Zhang
Applied Mathematics (AM) , 2018, DOI: 10.4236/am.2018.92012
Abstract:
Red tourism, which is featured with spiritual culture, resource fusion and historical socialization, is a remarkable innovation with Chinese characteristics. It is the shinning point of China’s tourism business development. This paper will show the objective and correct evaluation of red tourism resource. Firstly, it will create evaluation index system by theoretical analysis method and expert consultation method. Secondly, it will evaluate each object synthetically by fuzzy comprehensive evaluation method and analytic hierarchy process. Finally, through case study of General Zhang Aiping’s, Former Residence in Dazhou, Sichuan Province, conclusion and related suggestion will be achieved.
Effects of lithium chloride on outward potassium currents in acutely isolated hippocampal CA1 pyramidal neurons
Chaofeng Zhang,Huizhi Du,Pin Yang
Chinese Science Bulletin , 2006, DOI: 10.1007/s11434-006-2076-2
Abstract: Although lithium possesses neuroprotective functions, the molecular mechanism underlying its actions has not been fully elucidated. In the present paper, the effects of lithium chloride on voltage-dependent potassium currents in the CA1 pyramidal neurons acutely isolated from rat hippocampus were studied using the whole-cell patch-clamp technique. Depolarizing test pulses activated two components of outward potassium currents: a rapidly activating and inactivating component, I A and a delayed component, I K. Results showed that lithium chloride increased the amplitude of I A in a concentration-dependent manner. Half enhancement concentration (EC 50) was 22.80±5.45 μmol·L 1. Lithium chloride of 25 μmol·L 1 shifted the steady-state activation curve and inactivation curve of I A to more negative potentials, but mainly affected the activation kinetics. The amplitude and the activation processes of I K were not affected by lithium chloride. The effects of lithium chloride on potassium channel appear to possess neuroprotective properties by Ca2+-lowing effects modulate neuronal excitability by activating I A in rat hippocampal neurons.
Synthesis and characterization of Zr0.85Y0.15O1.925-La9.33Si6O26 composite electrolyte for application in SOFCs
Chaofeng Liu,Hong Zhang,Junxiao Xia,Zhicheng Li
Journal of Advanced Ceramics , 2012, DOI: 10.1007/s40145-012-0033-x
Abstract: Composite oxide ionic conductors consisting of Zr0.85Y0.15O1.925 (YSZ) and La9.33Si6O26 (LSO) have been synthesized by a modified coprecipitation method. X-ray diffraction, electron microscope, and complex impedance were adopted to investigate the phase component, microstructures, and conductivities, respectively. The results show that the average grain sizes of the composite powders and as-sintered pellets are less than 20 nm and 200 nm, respectively. The conductivity of the composite materials composed of 94 wt% YSZ and 6 wt% LSO is 0.215 S/cm at 700 °C. The conductivity of the composite is three times higher than that of the polycrystalline YSZ and has two orders in magnitude higher than that of the polycrystalline LSO at 700 °C. By analyzing the impedance spectra and modulus spectra, the grain-boundary effect on the conductivity improvement is investigated and the conductive mechanisms of the composite materials are discussed.
Computation of the Normalized Prediction Error of the Electroencephalogram Signal
Chaofeng Cai,Yong Zhang,Jingying Ren,Liying Jiang
TELKOMNIKA : Indonesian Journal of Electrical Engineering , 2012, DOI: 10.11591/telkomnika.v10i5.1268
Abstract: In this paper, the normalized prediction error of the electroencephalogram (EEG) signal recorded at five different mental tasks was computed. The results indicate that there exists predictability in the EEG signal beyond the baseline prediction of the mean and the one-step-ahead normalized prediction error of EEG signal vary greatly when different mental tasks are implemented, which implies that the one-step-ahead normalized prediction error can be employed as a feature of EEG signal to distinct different mental tasks. For different subjects, the one-step-ahead normalized prediction error vary greatly even the EEG signal are recorded from the same electrode under the same mental task, which implies that the subjects’ individual differences should be considered adequately when the one-step-ahead normalized prediction error is employed to distinct different mental tasks.
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