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The diffusive logistic growth model with time delay and feedback control is considered. First, the well-posedness and permanence of solutions are discussed by using some comparison techniques. Then, the sufficient conditions for stability of nonnegative constant steady states are established, and the occurrence of Hopf bifurcation at positive steady state(More)
The activity of polyphenol oxidase (PPO) in sour cherry fruit are determined by spectrophotometer. The effects of optimum pH, substrate concentration, temperature, substrates and inhibitors on PPO are studied and the reaction kinetic equation is established. The results showed that the optimum conditions are pH7.5, 0.1 M substrate and 20°C for PPO assay.(More)
To investigate the safety of urban mass transit, the forewarning grade of emergency is evaluated with the fuzzy sets theory. The new fuzzy evaluation method shows how the interrupt time, casualties, happen position, property loss and sphere of influence affect the forewarning grade of emergency in urban mass transit system. The results demonstrate that(More)
To evaluate the forewarning grade of emergency in urban mass transit comprehensively, a new combinatorial method combined with color warning was proposed. The evaluation factors which could influence the emergency were divided into external factors and internal factors. External factors were mainly decided by the evacuation wave in stations. Internal(More)
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