This paper theoretically studies the recombination-dominated nonequilibrium reacting flow inside the stagnation point bound- ary layer （SPBL） and the heat transfer characteristics under rarefied conditions. A genera...This paper theoretically studies the recombination-dominated nonequilibrium reacting flow inside the stagnation point bound- ary layer （SPBL） and the heat transfer characteristics under rarefied conditions. A general model is intuitively proposed to de- scribe the energy transfer and conversion along the stagnation streamline towards a slightly blunted nose with non-catalytic wall surface. It is found that the atoms recombination effects inside the SPBL could be equivalent to a modification on the de- gree of dissociation in the external flow. As a result, a recombination nonequilibrium criterion Dar, that is a specific DamktSh- let number, is introduced to characterize the nonequilibrium degree of the reacting flow in the SPBL, and then, based on the general model and Dar, a bridging function indicating the nonequilibrium chemical effects on the SPBL heat transfer is estab- lished. By using the explicitly analytical bridging function, the flow and heat transfer mechanisms, including the real gas flow similarity law and the nonequilibrium flow regimes classification, are discussed. In addition, the direct simulation Monte Carlo （DSMC） method has also been employed to systematically validate the analytical results.展开更多
In this paper, the incremental harmonic balance nonlinear identification (IHBNID) is presented for modelling and parametric identification of nonlinear systems. The effects of harmonic balance nonlinear identification...In this paper, the incremental harmonic balance nonlinear identification (IHBNID) is presented for modelling and parametric identification of nonlinear systems. The effects of harmonic balance nonlinear identification (HBNID) and IHBNID are also studied and compared by using numerical simulation. The effectiveness of the IHBNID is verified through the Mathieu-Duffing equation as an example. With the aid of the new method, the derivation procedure of the incremental harmonic balance method is simplified. The system responses can be represented by the Fourier series expansion in complex form. By keeping several lower-order primary harmonic coefficients to be constant, some of the higher-order harmonic coefficients can be self-adaptive in accordance with the residual errors. The results show that the IHBNID is highly efficient for computation, and excels the HBNID in terms of computation accuracy and noise resistance.展开更多
A nonlinear mathematical model is proposed and analyzed to study the dynamics of 2009 HIN1 flu epidemic in a homogeneous population with constant immigration of susceptibles. The effect of contact tracing and quaranti...A nonlinear mathematical model is proposed and analyzed to study the dynamics of 2009 HIN1 flu epidemic in a homogeneous population with constant immigration of susceptibles. The effect of contact tracing and quarantine （isolation） strategies in reduc- ing the spread of H1N1 flu is incorporated. The model monitors the dynamics of five sub-populations （classes）, namely susceptible with high infection risk, susceptible with reduction of infection risk, infective, quarantined and recovered individuals. The model analysis includes the determination of equilibrium points and carrying out their stability analysis in terms of the threshold parameter R0. Moreover, the numerical simulation of the proposed model is also performed by using fourth order Runge-Kutta method along with the sensitivity analysis of the endemic equilibrium point. The analysis and numeri- cal simulation results demonstrate that the maximum implementation of contact tracing and quarantine strategies help in reducing endemic infective class size and hence act as effective intervention strategy to control the disease. This gives a theoretical interpreta- tion to the practical experiences that the early contact tracing and quarantine strategies are criticMly important to control the outbreak of epidemics.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.91116012 and 11202224)the Postdoctoral Science Foundation of China (Grant No.2011M500415)
文摘This paper theoretically studies the recombination-dominated nonequilibrium reacting flow inside the stagnation point bound- ary layer （SPBL） and the heat transfer characteristics under rarefied conditions. A general model is intuitively proposed to de- scribe the energy transfer and conversion along the stagnation streamline towards a slightly blunted nose with non-catalytic wall surface. It is found that the atoms recombination effects inside the SPBL could be equivalent to a modification on the de- gree of dissociation in the external flow. As a result, a recombination nonequilibrium criterion Dar, that is a specific DamktSh- let number, is introduced to characterize the nonequilibrium degree of the reacting flow in the SPBL, and then, based on the general model and Dar, a bridging function indicating the nonequilibrium chemical effects on the SPBL heat transfer is estab- lished. By using the explicitly analytical bridging function, the flow and heat transfer mechanisms, including the real gas flow similarity law and the nonequilibrium flow regimes classification, are discussed. In addition, the direct simulation Monte Carlo （DSMC） method has also been employed to systematically validate the analytical results.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10672141, 10732020, and 11072008)
文摘In this paper, the incremental harmonic balance nonlinear identification (IHBNID) is presented for modelling and parametric identification of nonlinear systems. The effects of harmonic balance nonlinear identification (HBNID) and IHBNID are also studied and compared by using numerical simulation. The effectiveness of the IHBNID is verified through the Mathieu-Duffing equation as an example. With the aid of the new method, the derivation procedure of the incremental harmonic balance method is simplified. The system responses can be represented by the Fourier series expansion in complex form. By keeping several lower-order primary harmonic coefficients to be constant, some of the higher-order harmonic coefficients can be self-adaptive in accordance with the residual errors. The results show that the IHBNID is highly efficient for computation, and excels the HBNID in terms of computation accuracy and noise resistance.
文摘A nonlinear mathematical model is proposed and analyzed to study the dynamics of 2009 HIN1 flu epidemic in a homogeneous population with constant immigration of susceptibles. The effect of contact tracing and quarantine （isolation） strategies in reduc- ing the spread of H1N1 flu is incorporated. The model monitors the dynamics of five sub-populations （classes）, namely susceptible with high infection risk, susceptible with reduction of infection risk, infective, quarantined and recovered individuals. The model analysis includes the determination of equilibrium points and carrying out their stability analysis in terms of the threshold parameter R0. Moreover, the numerical simulation of the proposed model is also performed by using fourth order Runge-Kutta method along with the sensitivity analysis of the endemic equilibrium point. The analysis and numeri- cal simulation results demonstrate that the maximum implementation of contact tracing and quarantine strategies help in reducing endemic infective class size and hence act as effective intervention strategy to control the disease. This gives a theoretical interpreta- tion to the practical experiences that the early contact tracing and quarantine strategies are criticMly important to control the outbreak of epidemics.
