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排序方式: 共有693条查询结果,搜索用时 15 毫秒
81.
This paper deals with a predator–prey model with specialist harvesting, representing a two predators (Zooplankton) and one resource (Phytoplankton) system. First, the existence and stability of equilibria is analyzed both from local and global point of view. Our results indicate that a specialist harvesting which is discriminate may mediate the coexistence of the two zooplankton species which competitively exclude each other in absence harvesting. Although in most cases increasing harvesting reduces the two zooplankton species numbers, when harvesting leads to coexistence, it may also lead to increase the two zooplankton species numbers. Furthermore, to protect fish population from over exploitation a control instrument tax is imposed. The problem of optimal taxation policy is then solved by using Pontryagin’s maximal principle. It is established that the zero discounting leads to the maximization of the net economic revenue to the society and an infinite discount rate leads to complete dissipation of the net economic revenue to the society. Finally, the impact of harvesting is mentioned along with numerical results to provide some support to the analytical findings. 相似文献
82.
本文构建了电力供应链网络均衡模型,网络中包含三级决策主体,分别是:发电厂、电力服务商和用电市场.在分析各级决策者行为的基础上,得到了基于变分不等式的均衡条件,研究了针对发电厂的排污权交易政策设计问题.研究发现:排污交易政策实施后,总排污量不会超过给定的排污权总量;发电厂清洁生产能力的差异对排污权交易政策影响显著. 相似文献
83.
We consider the problem of finding the optimal dividend policy for a company whose cash reserve follows a Brownian motion with drift and volatility modulated by an observable finite-state continuous-time Markov chain. The Markov chain represents the regime of the economy. We allow fixed costs and taxes associated with the dividend payments. This optimization problem generates a stochastic impulse control problem with regime switching. We solve this problem and obtain the first analytical solutions for the optimal dividend policy when there are simultaneously fixed costs, taxes and business cycles. Our results show that the optimal dividend policy depends strongly on the regime of the economy, on fixed costs and on taxes. 相似文献
84.
报童模型的最优解及其解空间研究 总被引:1,自引:0,他引:1
文章从经典报童模型出发,找到了使收益最大化的报童模型最优解及其存在的解空间。在分析最优解存在条件的基础上,研究了单位生产成本和单位缺货惩罚成本对最优解的解空间的影响。在此基础上,进一步分析了如何通过控制单位生产成本和单位缺货惩罚成本,影响最优解存在条件的方法。最后,在该领域其他学者的实际算例的基础上,提出了分别通过调节单位生产成本和单位缺货惩罚成本,以及同时调节单位生产成本和单位缺货惩罚成本,从而影响企业生产决策的三种方法。文章结果可以指导相关学者选择适当的报童模型算例,且实际算例表明该方法在企业管理方面也有较好的效果和应用前景。 相似文献
85.
《Random Structures and Algorithms》2018,52(1):41-53
Given a sequence of n independent random variables with common continuous distribution, we propose a simple adaptive online policy that selects a monotone increasing subsequence. We show that the expected number of monotone increasing selections made by such a policy is within of optimal. Our construction provides a direct and natural way for proving the ‐optimality gap. An earlier proof of the same result made crucial use of a key inequality of Bruss and Delbaen [5] and of de‐Poissonization. 相似文献
86.
《Operations Research Letters》2020,48(1):96-103
This paper deals with risk-sensitive piecewise deterministic Markov decision processes, where the expected exponential utility of a finite-horizon reward is to be maximized. Both the transition rates and reward functions are allowed to be unbounded. Feynman–Kac’s formula is developed in our setup, using which along with an approximation technique, we establish the associated Hamilton–Jacobi–Bellman equation and the existence of risk-sensitive optimal policies under suitable conditions. 相似文献
87.
《Operations Research Letters》2020,48(6):792-797
This study considers a multi-period two-region repositioning problem with setup repositioning costs involved for vehicle sharing systems. We find that incorporating such costs can influence the total cost significantly and complicate the structure of the optimal policy. Moreover, we manage to partially characterize the optimal policy, and then develop an easy-to-implement heuristic policy. The performance of the heuristic policy and the influence of setup repositioning costs on policies are assessed numerically. 相似文献
88.
89.
Based on continuous review (r, Q) policy, this paper deals with contracts for vendor managed inventory (VMI) program in a system comprising a single vendor and a single retailer. Two business scenarios that are popular in VMI program are “vendor with ownership” and “retailer with ownership”. Taking the system performance in centralized control as benchmark, we define a contract “perfect” if the contract can enable the system to be coordinated and can guarantee the program to be trusted. A revenue sharing contract is designed for vendor with ownership, and a franchising contract is designed for retailer with ownership. Without consideration of order policy and related costs at the vendor site, it is shown that one contract can perform satisfactorily and the other one is a perfect contract. With consideration of order policy and related costs at the vendor site, it is shown that one contract can perform satisfactorily and the performance of the other one depends on system parameters. 相似文献
90.
Rikard Althin Lars Behrenz Rolf Färe Shawna Grosskopf Erik Mellander 《European Journal of Operational Research》2010
We measure how well Swedish employment offices perform in delivering the services required of them by the Swedish government. In contrast to earlier studies we use a dynamic efficiency framework, which allows us to better model the intertemporal nature of these services, explicitly allowing for placements of intermediate nature across periods. Rather than using second stage analysis to assess the effects of varying local labor market conditions and differences in client characteristics on performance, we include a measure of the office’s expected work load directly in the model. This measure, derived from duration analysis, is designed to capture the variation across offices in resources needed before an average individual can obtain employment. It is estimated from the characteristics of all unemployed individual and local labor market conditions. 相似文献