Search results for "Operations Research"
showing 10 items of 1297 documents
Using store level scanner data to improve category management decisions: Developing positioning maps
2009
This paper provides evidence of the usefulness of aggregated point-of-sale scanner data to infer the positioning of competing brands, providing valuable information for category management and hence facilitating decision making. Specifically, the authors propose a methodology to study the internal market structure based on market share models with latent heterogeneity when only macro-level time series data (not individual choices) are available. The proposed approach assumes a multidimensional decomposition, latent in the preference structure that is implicit to these types of models. By empirically applying this approach, the authors (1) simultaneously identify both latent dimensions of co…
Understanding the Health Disaster: Research Design for the Response to the 2014 West African Ebola Outbreak
2015
International audience; The 2014 Ebola outbreak in West Africa is the largest ever in history, affecting multiple countries and to this date, the World Health Organization has registered more than 6,500 deaths attributed to Ebola. The challenges arising from this outbreak to responders worldwide do not follow the standard characterisation or response patterns of natural sudden onset vs. conflict disasters. Rather, it is a medical emergency, which is intertwined with multiple challenges in the sectors decision-making, coordination, logistics and information management. In this paper, we present our research framework, which is based on desk research and initial interviews with responders. Th…
Group Extensions and Graphs
2016
A classical result of Gaschütz affirms that given a finite A-generated group G and a prime p, there exists a group G# and an epimorphism phi: G# ---> G whose kernel is an elementary abelian p-group which is universal among all groups satisfying this property. This Gaschütz universal extension has also been described in the mathematical literature with the help of the Cayley graph. We give an elementary and self-contained proof of the fact that this description corresponds to the Gaschütz universal extension. Our proof depends on another elementary proof of the Nielsen-Schreier theorem, which states that a subgroup of a free group is free.
The effect of inventory record inaccuracy in information exchange supply chains
2015
Abstract The goal of this paper is to quantify the impact of Inventory Record Inaccuracy on the dynamics of collaborative supply chains, both in terms of operational performance (i.e. order and inventory stability), and customer service level. To do so, we model an Information Exchange Supply Chain under shrinkage errors in the inventory item recording activity of their nodes, present the mathematical formulation of such supply chain model, and conduct a numerical simulation assuming different levels of errors. Results clearly show that Inventory Record Inaccuracy strongly compromises supply chain stability, particularly when moving upwards in the supply chain. Important managerial insights…
Variable Neighborhood Search for the Vertex Separation Problem
2012
The vertex separation problem belongs to a family of optimization problems in which the objective is to nd the best separator of vertices or edges in a generic graph. This optimization problem is strongly related to other well-known graph problems; such as the Path-Width, the Node Search Number or the Interval Thickness, among others. All of these optimization problems are NP-hard and have practical applications in VLSI, computer language compiler design or graph drawing. Up to know, they have been generally tackled with exact approaches, presenting polynomial-time algorithms to obtain the optimal solution for speci c types of graphs. However, in spite of their practical applications, these…
From the crowd to the market: The role of reward-based crowdfunding performance in attracting professional investors
2017
Abstract We focus on new technology-based entrepreneurial ventures engaging in reward-based crowdfunding and examine the effect of their performance in such funding channel on the likelihood of securing subsequent funding from professional investors. We also study how this effect is influenced by the presence of patents granted for the new product idea and the entrepreneur social capital. Results from a sample of technology projects launched on Kickstarter demonstrate that pledging a higher amount of money in crowdfunding can ignite professional investors’ interest and thus help secure subsequent funding. However, this positive evidence is effective only when complemented by the presence of…
Multiple Objective Analysis of Input-Output Models for Emergency Management
1990
This paper shows how a visual, interactive, dynamic multiple objective linear programming decision support system can effectively be used for analyzing input-output models. We have applied our approach to studying the quantitative effects of economic or political crises to the Finnish economy. Examples of such crises are nuclear power plant accidents, trade embargoes, and international conflicts. An input-output model of the Finnish economy with 17 industries (sectors) is employed. Our system has been implemented on a microcomputer and is being used by the National Board of Economic Defense. Several typical case situations are discussed.
"A Comment on Tobias Kronenberg's "Construction of Regional Input-Output Tables Using Nonsurvey Methods: The Role of Cross-Hauling"
2012
This article examines the effectiveness of a new non-survey regionalization method: Kronenberg’s Cross-Hauling Adjusted Regionalization Method (CHARM). This aims to take into account the fact that regions typically both import and export most commodities. Data for Uusimaa, Finland’s largest region, are employed to carry out a detailed empirical test of CHARM. This test gives very encouraging results. CHARM is suitable for studying environmental questions, but it can only be applied in situations where foreign imports have been included in the national input–output table. Where the focus is on regional output and employment, location quotients (LQs) can be used for purposes of regionalizati…
An analysis of the scientific productivity and visibility of publications on usability (1971-2005)
2009
Aims: To analyse usability-related articles published in the period 1971-2005 from a bibliometric point of view. Methods: A search for articles was made in the CSIC databases, the Social Science Citation Index, Science Citation Index, PsycInfo, MEDLINE and Inspec databases, using ad hoc search strategies designed for each. Contribution, specific contribution and overlap indices were calculated, as were the indicators of change in scientific production, the productivity of institutions and journals, and the distribution of journals by area of knowledge. Results: An exponential increase in the number of published articles was recorded, with the highest increase seen over the last five years. …
Uncertainty Assessment of a Water-Quality Model for Ephemeral Rivers Using GLUE Analysis
2011
Every model is, by definition, a simplification of the system under investigation. Although it would be desirable to reduce the gap between the simulated and the observed behaviors of the system to zero, this reduction is generally impossible owing to the unavoidable uncertainties inherent in any modeling procedure. Uncertainty analyses can provide useful insights into the best model approach to be used for obtaining results with a high level of significance and reliability. The evaluation of parameter uncertainties is necessary for calibration and for estimating the impact of these uncertainties on model performance. In this context, the uncertainty of a river water-quality model developed…