Stable coexistence mediated by specialist harvesting in a two zooplankton–phytoplankton system

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.     

组合评价模型在河南省主要城市综合经济实力评价中的应用

组合评价模型通过组合多个单一评价模型的评价结果,有效弥补单一方法的不足,提高评价的全面性和科学性.首先利用河南省2010年的相关数据,分别采用综合指数法、加权平均法、主成分分析法和因子分析法,对河南省的18个主要地区的综合经济实力进行了评价和排序;其次,建立基于模糊Borda法的组合评价模型,应用该模型对河南省的18个主要地区的综合经济实力进行了重新评价和排序,得到了更为可行的评价结果.     

辽宁省碳排放、能源消费与经济增长的实证研究

在环境库兹涅茨曲线的基础上,通过VAR分析方法,从实证的角度揭示了辽宁省1978-2009年碳排量、能源消耗同经济增长之间的动态关系,通过广义脉冲反应分析,得出不同于以往的"N"型EKC曲线.Granger因果检验表明,辽宁省持续提升的GDP不断刺激碳排放量和能源消耗量的增加,但环境变化却不是推动省内经济增长的重要变量.辽宁目前的环境质量正随着经济的增长而恶化,环境质量的提升问题亟待解决.     

基于IPAT模型的长株潭城市群经济增长与能源消耗的实证研究

基于IPAT方程,通过设定不同的情景来分析长株潭城市群2008年-2013年期间经济增长与资源消耗之间的定量关系．实证结果表明：GDP年增长率为12％,单位GDP能耗年下降4％这种组合是合理和适当的。符合长株潭城市群能源消耗的实际．以此为目标,能平稳推进长株潭城市群资源节约型社会建设进程,保持国民经济快速、健康、稳定的发展．     

An FPTAS for a single-item capacitated economic lot-sizing problem with monotone cost structure

We present a fully polynomial time approximation scheme (FPTAS) for a capacitated economic lot-sizing problem with a monotone cost structure. An FPTAS delivers a solution with a given relative error ɛ in time polynomial in the problem size and in 1/ɛ. Such a scheme was developed by van Hoesel and Wagelmans [8] for a capacitated economic lot-sizing problem with monotone concave (convex) production and backlogging cost functions. We omit concavity and convexity restrictions. Furthermore, we take advantage of a straightforward dynamic programming algorithm applied to a rounded problem.     

Fuzzy Model of Regional Economic Competitiveness in GIS Spatial Analysis: Case Study of Gansu, Western China

After more than 20 years of impressive development since the economic reforms in 1978, today western China is facing an increasing development gap between its regions, particularly between urban and rural areas. Using the fuzzy comprehensive evaluation model, this paper aims to demonstrate the evolution of the economic competitiveness levels base on two categories of geographical unity in the province of Gansu located in Northwest China between 2000 and 2004. The results of fuzzy modeling are integrated into GIS spatiotemporal analyses in order to identify the spatial variation of each significant change in terms of the regional economic development. Our research effectively illustrates that there is a particular spatial dynamic of the economic development from region to region. Although the cities have improved very well in their economic competitiveness, the rural areas and minority regions still have a lot of progress to be achieved.     

考虑货架存放期的经济批量排产问题的求解

在化工、造纸、制药、钢铁等工业生产中，一台设备或一条生产线可以生产多种产品的情况很常见。在生产中，如何安排各类产品的生产顺序以及生产数量显得十分重要。这类问题通常称作经济批量排产问题，这类问题是生产库存中的经典问题。本文研究的经济批量排产问题考虑了产品货架存放期因素，针对以往研究的不足，本文提出用批量变动方法求解该类问题，由计算结果显示，按照这种排产方法花费的成本要低于其他两种经济批量排产问题常用的方法。     

油价波动对国民经济影响模型构建与应用

为了科学构建原油价格波动与国民经济发展的关系,在借鉴国内外专家学者相关模型基础上,考虑不同国民经济指标对油价波动的时滞反馈等因素,构建油价波动对国民经济影响模型.利用原油价格波动对国民经济发展的动态模型,对模型的各部分关系系数进行确定,最后根据所得到的模型对国民经济影响进行实际分析与预测,并得出规避油价波动影响风险的措施.     

A discrete model for optimal operation of fossil-fuel generators of electricity

This paper presents a new discrete approach to the price-based dynamic economic dispatch (PBDED) problem of fossil-fuel generators of electricity. The objective is to find a sequence of generator temperatures that maximizes profit over a fixed-length time horizon. The generic optimization model presented in this paper can be applied to automatic operation of fossil-fuel generators or to prepare market bids, and it works with various price forecasts. The model’s practical applications are demonstrated by the results of simulation experiments involving 2009 NYISO electricity market data, branch-and-bound, and tabu-search optimization techniques.     

基于DEA和SFA的我国商业银行效率研究

本文利用板块数据,分别采用非参数前沿法中的DEA法和参数前沿法中的SFA法对我国十四家商业银行1997-2001期间的综合效率进行了测度,在此基础上对两种方法测度出的银行效率值排序进行了相关分析和一致性检验,结果表明两种方法测度出的银行效率在数值上有显著差异,但在是效率排序上具有很好的一致性。