Dispersion of Nodes Added to a Network

For location problems in which optimal locations can be at nodes or along arcs but no finite dominating set has been identified, researchers may desire a method for dispersing p additional discrete candidate sites along the m arcs of a network. This article develops and tests minimax and maximin models for solving this continuous network location problem, which we call the added-node dispersion problem (ANDP). Adding nodes to an arc subdivides it into subarcs. The minimax model minimizes the maximum subarc length, while the maximin model maximizes the minimum subarc length. Like most worst-case objectives, the minimax and maximin objectives are plagued by poorly behaved alternate optima. Therefore, a secondary MinSumMax objective is used to select the best-dispersed alternate optima. We prove that equal spacing of added nodes along arcs is optimal to the MinSumMax objective. Using this fact we develop greedy heuristic algorithms that are simple, optimal, and efficient (O( mp )). Empirical results show how the maximum subarc, minimum subarc, and sum of longest subarcs change as the number of added nodes increases. Further empirical results show how using the ANDP to locate additional nodes can improve the solutions of another location problem. Using the p-dispersion problem as a case study, we show how much adding ANDP sites to the network vertices improves the p-dispersion objective function compared with (a) network vertices only and (b) vertices plus randomly added nodes. The ANDP can also be used by itself to disperse facilities such as stores, refueling stations, cell phone towers, or relay facilities along the arcs of a network, assuming that such facilities already exist at all nodes of the network.     

Programming Models for Facility Dispersion: The p-Dispersion and Maxisum Dispersion Problems

The p-dispersion problem is to locate p facilities on a network so that the minimum separation distance between any pair of open facilities is maximized. This problem is applicable to facilities that pose a threat to each other and to systems of retail or service franchises. In both of these applications, facilities should be as far away from the closest other facility as possible. A mixed-integer program is formulated that relies on reversing the value of the 0–1 location variables in the distance constraints so that only the distance between pairs of open facilities constrain the maximization. A related problem, the maxisum dispersion problem, which aims to maximize the average separation distance between open facilities, is also formulated and solved. Computational results for both models for locating 5 and 10 facilities on a network of 25 nodes are presented, along with a multicriteria approach combining the dispersion and maxisum problems. The p -dispersion problem has a weak duality relationship with the (p-1)-center problem in that one-half the maximin distance in the p-dispersion problem is a lower bound for the minimax distance in the center problem for (p-1) facilities. Since the p-center problem is often solved via a series of set-covering problems, the p-dispersion problem may prove useful for finding a starting distance for the series of covering problems.     

Location and Pricing Decisions of a MultiStore Monopoly in a Spatial Market

Abstract.  This article presents an analysis of location and pricing decisions of a monopolist about to open several stores in a compact geographical space. The number of stores is made endogenous by the introduction of fixed costs. A novel methodology is developed, by which the firm's location and price decisions are represented as continuous functions defined over the geographical space. This modeling artifact generates a negligible error but simplifies the solution considerably and allows the derivation of several intuitive results. Although the focus is on one‐dimensional markets, it is shown that the method can easily be adapted to two‐dimensional markets.     

Power and the Spirit of Clustering

This paper utilizes the Scotch Whisky industry to identify an issue which is absent from the current literature on sector specific clusters namely the concept of power. It is argued that in order to understand the nature of power relationships within a cluster it is necessary to adopt a radical Coasian framework. The paper utilizes a typical Structure-conduct-performance approach to analyse the Scotch Whisky industry and to highlight the problems that power relationships pose within a typical cluster. It is imperative that policy-makers are aware of the power relationships which exist in clusters if clustering strategies are to deliver the perceived potential.     

Plant Size and Clustering of Manufacturing Activity

Although a growing number of studies emphasize the advantages small firms gain by co-locating in space, there is little empirical work that directly examines clustering trends by firm size. This paper presents an empirical analysis of the isolated effects of size on clustering patterns of producers in a major manufacturing state in the southeast United States. Recent developments in point process modeling allow us to control for the critical fact that economic activity is, in general, concentrated in space. Our findings suggest that the relationship between establishment size and clustering in North Carolina is roughly characterized by an inverted u-shape, that is, clustering increases up to some size threshold and then decreases again.     

Optimal Facility Location in a One-Dimensional Spatial Market

This paper analyzes properties of the optimal spatial arrangement of what may be interpreted as a class of public facilities. Optimality is defined as cost minimization. Three different optimality criteria are considered, and for each, the necessary and, sufficient conditions, market area size, and production levels, are derived. The relationship between optimal production levels and number of facilities needed is also considered. Next the results of implementing various pricing strategies are analyzed with emphasis given to marginal and uniform pricing. It is shown that, given certain conditions, all facilities incur operating deficits, given marginal pricing. Estimates on the level of the deficits are derived in terms of location rents. Finally, in the appendix, several important results from other studies are derived as special cases of the basic model.     

Cruise Passengers in a Homeport: A Market Analysis

Abstract

The aim of this study is to examine cruise passengers' characteristics, preferences and their overall experience in a port of call. Based on 1,361 survey data collected from passengers in the port of call of Cartagena, during the third quarter of 2009, a three-step multivariate market segment analysis is employed. First, a correspondence analysis is run to reveal the underlying factors in the data; second, based on the correspondence analysis, a hierarchical cluster investigation is performed to segment the sample into homogeneous groups; third, a decision tree is computed to characterise each group. The cluster analysis identifies six distinct market segments differentiated by nationality, satisfaction, safety perception and expenditure. The findings imply several policy directions. In particular, institutions should enhance the perception of safety in Cartagena to guarantee repeated visits, an ad hoc marketing policy may encourage revisit by young South Americans, and managers should extend the inland visiting time that is likely to produce local multiplier effects.     

Spatial Characteristics and Comparisons of Interaction and Median Clustering Models

Cluster analysis has been pursued from a number of directions for identifying interesting relationships and patterns in spatial information. A major emphasis is currently on the development and refinement of optimization‐based clustering models for the purpose of exploring spatially referenced data. Within this context, two basic methods exist for identifying clusters that are most similar. An interesting feature of these two approaches is that one method approximates the relationships inherent in the other method. This is significant given that the approximation approach is invariably utilized for cluster detection in spatial and aspatial analysis. A number of spatial applications are investigated which highlight the differences in clusters produced by each model. This is an important contribution because the differences are in fact quite significant, yet these contrasts are not widely known or acknowledged.     

Mode Choice in a Hub-and-Spoke Network: A Zero-One Linear Programming Approach

While research has tackled the hub-and-spoke network design problem, that research has overlooked the air-truck modal integration issue which is a common feature of real express delivery systems. This paper devises integer linear programs to represent the mode and route assignment aspects of the operational problem. The model is solved under four different levels of delivery schedule, and the results show that as the promised delivery schedule is relaxed, not only does the use of truck routes become more desirable, but also interesting adjustments in mode and hub assignment occur. Consider the case of hubs in Los Angeles and Dayton. As the time constraints are relaxed, cities such as Minneapolis and New Orleans originally linked by air to Los Angeles, switch to Dayton because cheaper truck routes become feasible.     

The Spatial Dispersion of Informal Investment at a Regional Level: Evidence from the UK

Although there have been various studies on the geographical specialization of venture capital in the UK, there remains a gap in the research on regional differences in the behaviour of those informal investors who make a significant contribution to the funding of entrepreneurial ventures. Utilizing a unique data set from the Global Entrepreneurship Monitor project, this study will estimate the level of informal investment activity across the different regions of the UK. The relationship between informal investment and early stage formal venture capital availability is also examined to determine which areas display the greatest funding gaps in the provision of equity finance. It shows that while formal and informal investments are heavily concentrated in highly prosperous areas such as London and the South East of England, informal investments make a larger relative contribution to early stage and expansion equity capital within poorer regions.     

Surviving in a Competitive Spatial Market: The Threshold Capture Model

Many facility location decision models ignore the fact that for a facility to survive it needs a minimum demand level to cover costs. In this paper we present a decision model for a firm that wishes to enter a spatial market where there are several competitors already located. This market is such that for each outlet there is a demand threshold level that has to be achieved in order to survive. The firm wishes to know where to locate its outlets so as to maximize its market share taking into account the threshold level. It may happen that due to this new entrance, some competitors will not be able to meet the threshold and therefore will disappear. A formulation is presented together with a heuristic solution method and computational experience.     

亿元时代的艺术品市场与收藏

2010年12月27日,首届2010中国艺术品市场高峰论坛在北京隆重举行。此次论坛旨在搭建行业沟通和深层对话的交流平台,以加强社会各界对中国艺术价值的认识和理解,辨析艺术品经营、收藏和研究者的历史使命与社会责任,探讨中国艺术品市场与收藏健康、可持续发展的方略。     

Periodicity and Market Interactions

This paper develops two systems of modeling periodic shopping behavior. The first approach uses a system of Volterra equations to define interactions between populations of consumers and firms in a special market. The second approach develops the relationship between trip length, frequency, and time for consumers in the context of the place utility model. The final section investigates ways of integrating the two approaches.