旅行社的旅游线路优化设置问题探讨

尽管在旅游线路的设计过程中需要解决的问题很多,但从优化的角度而言,如何设计出一条能实现出发地与目的地间的最短路径目标,便是其中的最为关键性的一个问题。由于不同的交通方式的不同组合能对应着不同的路程、时间与成本问题,因而,如何通过有效的选择来形成最佳的旅游线路也就有了相当的必要性。此外,在旅游线路设计与安排过程中,旅行社除了要合理安排和规划旅游线路的长度以力求不走回头路、不走冤枉路和形成有效的闭合回路外,还需充分考虑到其中的线路在时间安排上的合理问题;否则,再好的线路安排也会失去其内在的价值与影响力。     

Evolutionary Stability in the Investment-Opportunism-Retaliation Game

Can economically efficient outcomes be obtained and sustained in the absence of externally enforced property rights? We study the evolutionary properties of a game that exhibits two well-defined Nash equilibria: one generates an inefficient outcome while the other set generates an efficient outcome supported by the potential for retaliation. Although standard forward-looking refinements eliminate the efficient equilibrium, neither equilibrium type satisfies strict evolutionary stability criteria. However, both types of equilibrium define strategies that are neutrally stable, which makes them vulnerable to drift in dynamic environments. We conduct computer simulation experiments in which players learn adaptively via a tournament selection mechanism called sophisticated experimentation. Our simulations demonstrate that while the system spends a disproportionately high proportion of time in the inefficient equilibrium set, the efficient equilibrium is pervasive as the system drifts back and forth between the equilibrium sets, never settling on one or the other.     

Learning across the life cycle: Experimentation and performance among the hollywood studio heads

Guided by notions from the literature on organizational learning, this paper investigates how product line experimentation and organizational performance change across the careers of top managers. Its subjects are the studio heads who ran all the major Hollywood film studios from 1936 to 1965. The study found first, that product line experimentation declines over the course of executive tenures; second, that there is an inverse U‐shaped relationship between top executive tenure and an organization's financial performance; and third, that product line experimentation is more likely to benefit financial performance late in top executives' tenures. These findings are consistent with a three‐stage ‘executive life cycle’. During the early years of their tenures, top managers experiment intensively with their product lines to learn about their business; later on their accumulated knowledge allows them to reduce experimentation and increase performance; finally, in their last years, executives reduce experimentation still further, and performance declines. Copyright © 2001 John Wiley & Sons, Ltd.     

论科研选题应注意的几个问题

科研选题要善于把握选题的原别和导向，注意课题的研究动态，把握课题的研究范围，发挥出科研人员的优势，设计出切实可行的研究路线。     

On estimating the mean of the selected normal population under the LINEX loss function

Following Parsian and Farsipour (1999), we consider the problem of estimating the mean of the selected normal population, from two normal populations with unknown means and common known variance, under the LINEX loss function. Some admissibility results for a subclass of equivariant estimators are derived and a sufficient condition for the inadmissibility of an arbitrary equivariant estimator is provided. As a consequence, several of the estimators proposed by Parsian and Farsipour (1999) are shown to be inadmissible and better estimators are obtained. Received January 2001/Revised May 2002     

Selecting Sites for New Facilities Using Data Envelopment Analysis

This paper develops a mathematical programming model for obtaining a best set of sites for planned facilities. The model is concerned with those situations where resource constraints are present. The specific setting for the paper involves the selection of sites for a set of retail outlets, wherein the ratio of aggregate outputs to inputs for the selected set is maximal among all possible sets that could be chosen. At the same time, the model guarantees that the only sets of stores allowable are those for which the available resources are used to the maximum extent possible.     

三阶随机占优准则在证券选择中的应用

通常可以用分布函数和分住数函数描述随机占优准则,Man-Chung Ng列举的两个例子说明在三阶随机占优条件下用两种方法得到的结论是不一致的,这与Levy的观点相反。该文分别将这两种方法描述的三阶随机占优准则用于上海证券市场的基金选择,发现用两种方法在应用中得到的结论并不总是一致的。由此验证用Levy提出的分位数方法描述的随机占优准则进行实证研究是不正确的,一阶和二阶条件除外。     

Forecasting economic time series using flexible versus fixed specification and linear versus nonlinear econometric models

Nine macroeconomic variables are forecast in a real-time scenario using a variety of flexible specification, fixed specification, linear, and nonlinear econometric models. All models are allowed to evolve through time, and our analysis focuses on model selection and performance. In the context of real-time forecasts, flexible specification models (including linear autoregressive models with exogenous variables and nonlinear artificial neural networks) appear to offer a useful and viable alternative to less flexible fixed specification linear models for a subset of the economic variables which we examine, particularly at forecast horizons greater than 1-step ahead. We speculate that one reason for this result is that the economy is evolving (rather slowly) over time. This feature cannot easily be captured by fixed specification linear models, however, and manifests itself in the form of evolving coefficient estimates. We also provide additional evidence supporting the claim that models which ‘win’ based on one model selection criterion (say a squared error measure) do not necessarily win when an alternative selection criterion is used (say a confusion rate measure), thus highlighting the importance of the particular cost function which is used by forecasters and ‘end-users’ to evaluate their models. A wide variety of different model selection criteria and statistical tests are used to illustrate our findings.     

Risky allocations from a risk-neutral informed principal

We study a model of informed principal with private values where the principal is risk neutral and the agent is risk averse. We show that the principal, regardless of her type, gains by not revealing her type to the agent through the contract offer. The equilibrium allocation transfers some ex-ante risk from one type of agent to the other. Despite the increase in the principal's surplus, allocative efficiency does not necessarily improve. Received: 26 January 2004, Accepted: 5 May 2005 JEL Classification: C72, D23, D82 I would like to thank my supervisor Leonardo Felli for suggestions and Leo Ferraris for helpful discussions. All remainig errors are my own.     

经济生产量模型对库存的控制

在分析需求变化的基础上修改和完善了经济批量模型,进一步研究了单项物品和多项物品的最小经济生产批量以及年最小总成本,改进了经济生产量模型。