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51.
OPTIMAL FISH HARVESTING FOR A POPULATION MODELED BY A NONLINEAR PARABOLIC PARTIAL DIFFERENTIAL EQUATION 下载免费PDF全文
As the human population continues to grow, there is a need for better management of our natural resources in order for our planet to be able to produce enough to sustain us. One important resource we must consider is marine fish populations. We use the tool of optimal control to investigate harvesting strategies for maximizing yield of a fish population in a heterogeneous, finite domain. We determine whether these solutions include no‐take marine reserves as part of the optimal solution. The fishery stock is modeled using a nonlinear, parabolic partial differential equation with logistic growth, movement by diffusion and advection, and with Robin boundary conditions. The objective for the problem is to find the harvest rate that maximizes the discounted yield. Optimal harvesting strategies are found numerically. 相似文献
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Franck S. Schoonbeek Jan H. van Esch Bas Wegewijs Diederik B. A. Rep Matthijs P. de Haas Teun M. Klapwijk Richard M. Kellogg Ben L. Feringa 《Angewandte Chemie (International ed. in English)》1999,38(10):1393-1397
Hydrogen bonds between urea units allow self-organization of π systems in mono- and bithiophenes into fibers as shown schematically. In these fibers there is a surprisingly high mobility of charge carriers as determined by pulse-radiolysis time-resolved microwave conductivity measurements. 相似文献
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Various types of electron deficient saturated carbon atoms are reduced in a visible light initiated process by N-alkyl-2,3-dihydrobenzothiazoles; these reactions are accelerated in the presence of Ru(bipy)3Cl2. The same ring system can act as an enolate carrier under electrophilic conditions. 相似文献
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本文报导了采用氩离子激光器来泵浦Pr3+:YLF晶体,应用声光调制器实现了主动锁模;同时应用振动─高反射平面镜也实现了被动锁模,两种锁模均得到了ps光脉冲.据作者了解这是这种晶体材料的第一次锁模运转. 相似文献
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Summary Physical organic structural properties of small molecules and macromolecules such as bond count, branching and proximity between multiple polar fragments contribute significantly to measured hydrophobicity (log P). These structural properties are encoded in the Rekker and Leo methods of calculating log P as structural-dependent factors. Regardless of the size of the atom primitive set, methods predicting log P with only atom primitives can miss subtle structural detail within series of related compounds. The HINT (Hydropathic INTeractions) model for inter- and intramolecular noncovalent interactions calculates atom-based hydrophobic constants, but uses all Leo-type factors in the calculation rather than a large set of atom primitives. Two types of applications of HINT are discussed: evaluation of the binding of an inhibitor (A74704) to HIV-1 protease, where it is shown that modeling of the protonation state (i.e., Asp25, Asp125) in the protein can strongly influence perceived substrate binding; and the use of HINT to calculate a third (hydropathic) field for CoMFA can yield a statistically enhanced and predictive model for molecular design. 相似文献
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