Search results for "Operations"

Case Studies in Financial Optimization

2010

Operational and financial effectiveness of e-collaboration tools in supply chain integration

2004

This paper develops a comprehensive model of supply chain integration and uses it to analyze and assess the operational and financial effectiveness of different e-collaboration tools at various levels of supply chain integration. This model is also used to evaluate the importance of the sequence in which e-collaboration tools are adopted in supply chain integration. Computational results from a validated system dynamics simulation model with different implementation sequences of e-collaboration tools and different financial scenarios show that local financial constraints can also severely impact operational and financial performance of the entire supply chain. (C) 2003 Elsevier B.V. All rig…

A Stochastic Programming Model for the Optimal Issuance of Government Bonds

2010

Sovereign states issue fixed and floating securities to fund their public debt. The value of such portfolios strongly depends on the fluctuations of the term structure of interest rates. This is a typical example of planning under uncertainty, where decisions has to be drawn on the base of the key stochastic economic factors underneath the model.We propose a multistage stochastic programming model to select portfolios of bonds, where the aim of the decision maker is that of minimizing the cost of the decision process. At the same time, we bound the conditional Value-at-Risk, a measure of risk which accounts for the losses of the tail distribution. We build an efficient frontier to trade-off…

A Spatial Multilevel Analysis of Italian SMEs Productivity

2009

Abstract In this paper, we adapt multilevel analysis methods to investigate the spatial variability of SMEs' productivity across the Italian territory, and account for differences in the socio-economic context. Our results suggest that to properly capture the variability of the data, it is important to allow for both spatial mean and slope effects. Social decay has the expected negative impact. However, while this effect is larger on firms with smaller capital intensity, firms with higher capital intensity seem to be less affected by geography. Greater territorial heterogeneity emerges among those firms with lower capital to labour ratios. Une analyse spatiale a plusieurs niveaux de la prod…

Robotic assistance for industrial sanding with a smooth approach to the surface and boundary constraints

2021

[EN] Surface treatment operations, such as sanding, deburring, finishing, grinding, polishing, etc. are progressively becoming more automated using robotic systems. However, previous research in this field used a completely automatic operation of the robot system or considered a low degree of human-robot interaction. Therefore, to overcome this issue, this work develops a truly synergistic cooperation between the human operator and the robot system to get the best from both. In particular, in the application developed in this work the human operator provides flexibility, guiding the tool of the robot system to treat arbitrary regions of the workpiece surface; while the robot system provides…

UML/OCL-based modeling of work-based access control policies for collaborative healthcare systems

2016

A work-based access control (WBAC) model is proposed by introducing the team role concept and modifying the user-role assignment model from a previous work. The main goals of WBAC are flexibility, easy manageability, security, as well as suitability to support cooperative work of dynamic teams in healthcare environments. One of the major challenges of WBAC regards authorization constraints in terms of organizational policies. In this article, we show how Unified Modeling Language (UML) and Object Constraints Language (OCL) are utilized to design and analyze the authorization constraints of WBAC in cooperative engagements with complex scenarios in the collaborative healthcare domain. We also…

Balancing Flexibility and Coherence: Information Exchange in a Paper Machinery Project

1999

The problem of balancing coherence and flexibility in collaborative information system design is approached here with two pairs of concepts. Boundary objects can support communication for perspective taking between communities of practice. Conscripting devices can support communication for perspective making within a community of practice. These theoretical lenses are used to study the uses of the technical specification in paper machine projects. Our study showed that as a boundary object it provided enough flexibility to allow negotiations, and sufficient local structure, for carrying out work in both communities of practice, the customer and the manufacturer. As a conscription device in …

General and flexible methodology and architecture for CAPP: GF-CAPP system

2003

Although all researchers insist on the need to develop computer-aided process planning (CAPP) systems, they agree that one of its most significant shortfalls is the low level of generality and flexibility present in current proposals. One of the outcomes of this low level of generality--apart from its limited application domain--is the low level of integration achieved with CAD, CAM and PP&C systems. To ensure optimized running of the production system, it is also important to stress the need to develop alternative process planning that enables it to adapt to disruptions in production. Several factors play an important role in implementing these features, among which the following may be hi…

Principles of scatter search

2006

Scatter search is an evolutionary method that has been successfully applied to hard optimization problems. The fundamental concepts and principles of the method were first proposed in the 1970s, based on formulations dating back to the 1960s for combining decision rules and problem constraints. In contrast to other evolutionary methods like genetic algorithms, scatter search is founded on the premise that systematic designs and methods for creating new solutions afford significant benefits beyond those derived from recourse to randomization. It uses strategies for search diversification and intensification that have proved effective in a variety of optimization problems. This paper provides…

Semiparametric stochastic frontier models: A generalized additive model approach

2017

Abstract The choice of the functional form of the frontier into a stochastic frontier model is typically neglected in applications and canonical functions are usually considered. This paper introduces a semiparametric approach for stochastic frontier estimation that extends previous works based on pseudo-likelihood estimators allowing flexibility in model selection and capability of imposing monotonicity and concavity constraints. For these purposes the present work introduces a generalized additive framework that moreover permits to model the influence of contextual/environmental factors to the hypothesized production process by the relative extension given by generalized additive models f…