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61.
So far, in the nonparametric literature only full frontier nonparametric methods have been applied to search for economies of scope and scale, particularly the data envelopment analysis method (DEA). However, these methods present some drawbacks that might lead to biased results. This paper proposes a methodology based on more robust partial frontier nonparametric methods to look for scope and scale economies. Through this methodology it is possible to assess the robustness of these economies, and in particular to assess the influence that extreme data or outliers might have on them. The influence of the imposition of convexity on the production set of firms was also investigated. This methodology was applied to the water utilities that operated in Portugal between 2002 and 2008. There is evidence of economies of vertical integration and economies of scale in drinking water supply utilities and in water and wastewater utilities operating mainly in the retail segment. Economies of scale were found in water and wastewater utilities operating exclusively in the wholesale, and in some of these utilities diseconomies of scope were also found. The proposed methodology also allowed us to conclude that the existence of some smaller utilities makes the minimum optimal scales go down. 相似文献
62.
Optimality conditions for weak efficient, global efficient and efficient solutions of vector variational inequalities with constraints defined by equality, cone and set constraints are derived. Under various constraint qualifications, necessary optimality conditions for weak efficient, global efficient and efficient solutions in terms of the Clarke and Michel–Penot subdifferentials are established. With assumptions on quasiconvexity of constraint functions sufficient optimality conditions are also given. 相似文献
63.
《Operations Research Letters》2014,42(5):337-342
This paper discusses a mean–variance portfolio selection problem under a constant elasticity of variance model. A backward stochastic Riccati equation is first considered. Then we relate the solution of the associated stochastic control problem to that of the backward stochastic Riccati equation. Finally, explicit expressions of the optimal portfolio strategy, the value function and the efficient frontier of the mean–variance problem are expressed in terms of the solution of the backward stochastic Riccati equation. 相似文献
64.
陈飞 《数学的实践与认识》2014,(7)
基于农业生产技术的功能性特征及随机前沿理论,构建可分离柯布-道格拉斯形式生产函数,测算我国粮食生产全要素增长率及其组成成分.实证结果表明,1999-2011年间,小麦、稻谷和玉米作物的全要素增长率普遍较低,其中,前沿技术进步率对全要素增长率具有正的贡献;但技术效率(尤其是M技术效率)在逐年降低,是造成全要素增长率偏低的主要原因.在此基础上,对影响我国粮食生产技术效率变化的因素进行理论分析和实证检验.研究发现,以直接补贴为主的农业财政支出政策对BC和M技术效率提高作用明显,且影响效果最强.粮食生产技术的推广与普及、粮食生产的规模化和专业化对技术效率具有显著正向影响,但市场机制的影响效果并没有显现出来. 相似文献
65.
集值映射向量优化问题是最优化理论中的一个重要方向.在集值映射为生成锥内部-锥一类凸(简记为ic-锥类凸)的假设条件下,利用择一定理,给出了集值映射向量优化问题ε-弱有效解和ε-有效解的最优性条件和ε-Lagrange乘子定理,是弱有效解和有效解相应结果的推广. 相似文献
66.
67.
本文研究拓扑空间中锥拟凸多目标优化问题的有效解集的连通性.在目标映射是上连续和拟凸(次严格拟凸)的条件下,证明了锥弱有效(有效)解集是连通的.进一步,在是连续和强拟凸的条件下,证明了锥有效解集是路连通的. 相似文献
68.
Container ports are a major component of international trade and the global supply chain. Hence, the improvement of port efficiency can have a significant impact on the wider maritime economy. This paper deconstructs a representation in the existing literature that neglects the heterogeneity of individual and group-specific terminal operators. In its place, we present a hierarchical model to make a connection between efficiency and terminal operator group characteristics. The paper develops a stochastic frontier model that controls not only individual heterogeneity but also group-specific variations. The model decomposes the total stochastic derivation from the frontier into inefficiency, individual heterogeneity, group-specific variations, and noise components, with the estimation being performed using Markov chain Monte Carlo simulations. The validity of the model is tested with a panel of container terminal operator data from 1997-2004. Our findings show that terminal operator groups are important in promoting terminal efficiency at the global level, and that the operators with stevedore backgrounds show a higher efficiency than carriers. 相似文献
69.
Shigeru Arimoto Mark Spivakovsky Hiromu Ohno Peter Zizler Keith F. Taylor Tokio Yamabe Paul G. Mezey 《International journal of quantum chemistry》2001,84(4):389-400
The present Part VI of this series of articles provides a mathematical and methodical link between (i) fundamental methodology in the repeat space theory (RST), which is referred to as the approach via the aspect of form and general topology and which has universal unifying power to handle additivity problems of molecules that have many identical moieties, and (ii) frontier electron theory of reactivity indices. Using theoretical tools required to link (i) and (ii), we establish a theorem from which the Generalized Alpha Existence Theorem (a theorem essential in the RST and proved in the previous Part V) directly follows. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 389–400, 2001 相似文献
70.
In this paper, a graphical characterization, in the decision space, of the properly efficient solutions of a convex multiobjective
problem is derived. This characterization takes into account the relative position of the gradients of the objective functions
and the active constraints at the given feasible solution. The unconstrained case with two objective functions and with any
number of functions and the general constrained case are studied separately. In some cases, these results can provide a visualization
of the efficient set, for problems with two or three variables. Besides, a proper efficiency test for general convex multiobjective
problems is derived, which consists of solving a single linear optimization problem. 相似文献