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Zhang S.,Tianjin University of Technology | Guo W.,Institute of Military Traffic | Lv F.,Nankai University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

A PPKTP crystal was used to efficient green emission. Spectrum characteristics of FF and SH wave was analyzed, and phase-matching wavelength shift results from thermally-induced poling period shift. A conversion efficiency of 26.1% can be achieved.

Lv Y.,Tianjin Polytechnic University | Pei Y.,Tianjin Polytechnic University | Gao S.,Gannan Normal University | Li C.,Institute of Military Traffic
Nonlinear Analysis: Real World Applications | Year: 2010

Considering that some phytoplankton and zooplankton are harvested for food, a phytoplanktonzooplankton model with harvesting is proposed and investigated. First, stability conditions of equilibria and existence conditions of a Hopf-bifurcation are established. Our results indicate that over exploitation would result in the extinction of the population and an appropriate harvesting strategy should ensure the sustainability of the population which is in line with reality. Furthermore, the existence of bionomic equilibria and the optimal harvesting policy are discussed. The present value of revenues is maximized by using Pontryagin's maximum principle subject to the state equations and the control constraints. We discussed the case of optimal equilibrium solution. It is found that the shadow prices remain constant over time in optimal equilibrium when they satisfy the transversality condition. It is established that the zero discounting leads to the maximization of economic revenue and that an infinite discount rate leads to complete dissipation of economic rent. Finally, some numerical simulations are given to illustrate our results. © 2009 Elsevier Ltd. All rights reserved.

Pei Y.,Tianjin Polytechnic University | Ji X.,Tianjin Polytechnic University | Li C.,Institute of Military Traffic
Mathematical and Computer Modelling | Year: 2010

In this paper, two integrated pest management models are investigated, which rely on release of infective pest individuals and of natural enemies in a constant amount, together with spraying of pesticides. It is proved that the susceptible pests can be eradicated if the release amount of infected pests is above some threshold or the pesticide effect is above another threshold. Furthermore, permanent conditions are established when an impulsive control is used. Finally, numerical results show that (1) fewer infected pests or pesticides are needed as the impulsive strategy is taken, displaying its positive effect on the pest control; (2) our assumption that the natural enemies of the pests do not catch the infective pests would reduce the level of the susceptible pests. © 2009 Elsevier Ltd. All rights reserved.

Yongzhen P.,Tianjin Polytechnic University | Shuping L.,Tianjin Polytechnic University | Changguo L.,Institute of Military Traffic
Nonlinear Dynamics | Year: 2011

In the paper an eco-epidemic system with delay and parasitic infection in the prey is investigated. The conditions for asymptotic stability of steady states are derived and the length of the delay preserving the stability is also estimated. Further, the criterion for existence of Hopf-type small amplitude periodic oscillations of the predator and prey biomass is derived. Numerical results indicate that the delay does not affect the stability of the system in the process but makes all populations oscillate more intensively. In addition, the results show that the recovery makes the levels of the infected prey and the predator become lower but makes the sound prey higher in limit time. © 2010 Springer Science+Business Media B.V.

Ji X.,Tianjin Polytechnic University | Pei Y.,Tianjin Polytechnic University | Li C.,Institute of Military Traffic
Nonlinear Analysis: Real World Applications | Year: 2010

In this paper, two SIR epidemic models with different patterns of recruitment and difference in immunity are investigated. When the recruitment rate is less than some threshold value, the disease will be eradicated. Furthermore, for the continuous recruitment model, according to the Poincare-Bendixson theorem, the global asymptotical stability of a unique positive equilibrium is obtained. For the pulse recruitment model, we investigated the existence of nontrivial periodic solutions via a supercritical (subcritical) bifurcation. From a biological point of view, our results indicate that (1) the disease can be eradicated if the recruitment rate is controlled under some threshold; (2) the number of the infected increases as the difference in immunity increases; (3) fewer individuals are infected as the pulse recruitment is taken, displaying its effect on the control of the disease. © 2009 Elsevier Ltd. All rights reserved.

Jin S.,Hebei University of Technology | Zhang Y.,Hebei University of Technology | Wan Y.,Hebei University of Technology | Li N.,Hebei University of Technology | Zhang H.,Institute of Military Traffic
Advances in Intelligent and Soft Computing | Year: 2012

The strong deviation theorems is one of the central questions for studying in the International Probability theory. In this paper, a strong deviation theorem for Markov chains functional indexed by a non-homogeneous tree were obtained by constructing a non-negative martingale. © 2012 Springer-Verlag Berlin Heidelberg.

Shi B.-C.,Nankai University | Wang X.-L.,Nankai University | Guo W.-G.,Institute of Military Traffic | Song L.-P.,Nankai University
Chinese Physics B | Year: 2015

Digital holography can be applied to ultrafast detection when a femtosecond laser pulse is used. In this paper, the interference process of two femtosecond laser pulses is studied and the recording process of the femtosecond laser pulsed digital hologram is simulated. Holograms at different recording angles are generated by integrating the instantaneous interference field. By analyzing the distribution of the reconstructed phase error, the characteristics of femtosecond laser pulsed digital holography are discussed. © 2015 Chinese Physical Society and IOP Publishing Ltd.

Hu H.-F.,Nankai University | Wang X.-L.,Nankai University | Guo W.-G.,Institute of Military Traffic | Zhai H.-C.,Nankai University | Wang P.,Nankai University
Wuli Xuebao/Acta Physica Sinica | Year: 2011

The dynamic process of femtosecond laser pulse ablation of silica glass has been experimentally investigated by ultrafast time-resolved optical diagnosis. The digital holograms of material ejections outside the silica glass are recorded, and two-dimensional phase difference maps at different delay times are obtained, from which the composition and the structure of the ejected materials are deduced. Besides, the time-resolved shadowgraphs of the phenomena inside the silica glass are also recorded, and the evolution process of two stress waves inside the silica glass is observed in the shadowgraphs, which are believed to be related to two material ejections outside the target. © 2011 Chinese Physical Society.

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