A methodology to select suppliers to increase sustainability within supply chains

Central European Journal of Operations Research - Sustainability practice within supply chains remains in an early development phase. Enterprises still need tools that support the integration of...     

Single-molecule pump-probe detection resolves ultrafast pathways in individual and coupled quantum systems

We report the first experimental study of individual molecules with femtosecond time resolution using a novel ultrafast single-molecule pump-probe method. A wide range of relaxation times from below 100 up to 400 fs is found, revealing energy redistribution over different vibrational modes and phonon coupling to the nanoenvironment. Addressing quantum-coupled molecules we find longer decay times, pointing towards inhibited intramolecular decay due to delocalized excitation. Interestingly, each individual system shows discrete jumps in femtosecond response, reflecting sudden breakup of the coupled superradiant state.     

A new approach for data editing and imputation

The editing-and-imputation problem concerns the question of finding errors in a record which does not satisfy a set of consistency rules. Once some potential errors have been localizated, it is also necessary to impute new values to the associated fields. The output dataset should consist of valid records and preserve similar statistical properties as the input dataset. Most of this work is usually done manually by statistical agencies, thus consuming a great deal of human resources. This paper presents a mathematical programming model to optimally solve the problem on surveys with categorical values and particular edits. We also describe a heuristic approach to deal with the more complex surveys. The heuristic procedure follows a combination of the widely-accepted hot-deck donor scheme and the multivariate regression analysis. It has been implemented in a graphical user interface running on standard personal computers, and has been tested on real-world surveys. This paper demonstrates the satisfactory performance of our automatic procedure.     

Using an ANP performance management framework to manage the development of transversal competences in University degrees

Organisations are concerned about measuring the performance of the product/service they deliver to their customers. In all types of organisations, if a proper performance assessment is to be developed, it should be measured in different dimensions. At University, the new study programs include the development and assessment of transversal competences due to their importance in enhancing the abilities and improving the employability of students. The achievement of transversal competences can be assessed in different levels/stages; for example, the 1st and 2nd years of a Bachelor’s degree; the 3rd and 4th years of a Bachelor’s degree and at Master’s level. The purpose of this paper is to integrate the research into performance management in organisations to develop an approach consisting of four components (a methodology, a solid and integrated performance management framework, graphical diagrams and quantitative techniques) to assess and manage the achievement of transversal competences through the different levels of study using a consolidated approach. The proposal uses the Analytic Network Process (ANP) to model dependences and feedback among the elements of the competences.

     

On the one-commodity pickup-and-delivery traveling salesman problem with stochastic demands

This paper studies how to set the vehicle capacity for traveling Salesman Problems where some of the customer demands are stochastic. The analyses are done for the one-commodity pickup-and-delivery TSP, as this problem also includes the setting of the initial load. The paper first considers feasibility issues. This includes finding the smallest vehicle capacity and some initial load such that a given tour is feasible for all scenarios. Different variants are considered as a function of the time when information becomes available. The paper then analyzes the case where some penalties are paid for routing a tour unable to handle customer demands. Various types of penalties are considered. The paper studies properties of the minimal expected penalty of a given tour, which are then used to provide approaches to find near-optimal tours. Computational results are presented.     

Controlled rounding and cell perturbation: statistical disclosure limitation methods for tabular data

Rounding methods are common techniques in many statistical offices to protect sensitive information when publishing data in tabular form. Classical versions of these methods do not consider protection levels while searching patterns with minimum information loss, and therefore typically the so-called auditing phase is required to check the protection of the proposed patterns. This paper presents a mathematical model for the whole problem of finding a protected pattern with minimum loss of information, and proposes a branch-and-cut algorithm to solve it. It also describes a new methodology closely related to the classical Controlled Rounding methods but with several advantages. The new methodology is named Cell Perturbation and leads to a different optimization problem which is simpler to solve than the previous problem. This paper presents a cutting-plane algorithm for finding an exact solution of the new problem, which is a pattern guaranteeing the same protection level requirements but with smaller loss of information when compared with the classical Controlled Rounding optimal patterns. The auditing phase is unnecessary on the solutions generated by the two algorithms. The paper concludes with computational results on real-world instances and discusses a modification in the objective function to guarantee statistical properties in the solutions. Received: April, 2004     

Organized vs. Competitive Corruption

We study bureaucratic corruption in a model in which a constituency sets required levels for a given set of activities. Each activity is carried out by an external provider and its realization is supervised by a bureaucrat. Bureaucrats are supposed to act on behalf of the constituency, but they can allow providers to deliver lower activity levels than contracted in exchange for a bribe. Given this, the constituency sets the optimal activity levels weighing off the value of activity levels, their costs, as well as the possibility for the bureaucrats to be corrupt. We use this setup to study the impact on equilibrium corruption of the degree of decentralization of corruption. To do this we compute equilibrium corruption in two different settings: (1) Each bureaucrat acts in such a way as to maximize his own individual utility (competitive corruption); (2) An illegal syndicate oversees the corruption decisions of the population of bureaucrats in such a way as to maximize total proceeds from corruption (organized corruption). We show that the illegal syndicate acts in such a way as to restrain the total number of corrupt transactions and corruption is lower when it is organized than when it is competitive.