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In this paper, we present some new properties of the Mitra‐Wan forestry model written as a discrete‐time optimal control problem. For this problem, the set of stationary states is characterized. For the optimal long‐run management, we consider the following optimality criteria: average optimality, good control policies, bias optimality, and overtaking optimality. We establish relationships between these criteria and show that the value of average optimal policies is constant and equals the value in the optimal stationary state. 相似文献
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Strontium Sorption on Hematite at Elevated Temperatures 总被引:1,自引:0,他引:1
Karasyova ON Ivanova LI Lakshtanov LZ Lövgren L 《Journal of colloid and interface science》1999,220(2):419-428
Acid–base reactions and surface complexation of Sr(II) at the hematite/water interface have been studied by means of potentiometric titrations at three different temperatures: 25, 50, and 75°C. Equilibrium measurements were performed in 0.1 M NaCl. In the evaluation of equilibrium models for the acid–base reactions and complexation reactions in the three-component system H+ ---(FeOH)---Sr2+, the constant capacitance model was applied. During the titrations with Sr, aliquots of the suspension were sampled at in several points. The aqueous concentrations of Sr were analyzed by atomic absorption spectrometry. Treatment of data included tests for formation of both inner-sphere and outer-sphere complexes of different stoichiometric composition. The proposed equilibrium model consists of the following surface complexes of inner sphere type: FeOHSr2+ and FeOSrOH. Besides the stability constants for the surface complexes, the thermodynamic parameters ΔH and ΔS were evaluated. The combined effect of a decrease in pHpzc with increasing temperature and positive enthalpies of surface complex formation favors adsorption of Sr at elevated temperatures. 相似文献
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